THTR-300 nuclear power plant

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THTR-300 nuclear power plant
Dry cooling tower of the THTR-300 (demolished 1991)
Dry cooling tower of the THTR-300 (demolished 1991)
location
THTR-300 nuclear power plant (North Rhine-Westphalia)
THTR-300 nuclear power plant
Coordinates 51 ° 40 ′ 45 "  N , 7 ° 58 ′ 18"  E Coordinates: 51 ° 40 ′ 45 "  N , 7 ° 58 ′ 18"  E
Country: Germany
Data
Owner: High temperature nuclear power plant
Operator: High temperature nuclear power plant
Project start: 1971
Commercial operation: June 1, 1987
Shutdown: September 29, 1989

Decommissioned reactors (gross):

1 (308 MW)
Energy fed in in 1988: 294.63 GWh
Energy fed in since commissioning: 2,756 GWh
Website: official page
Was standing: Oct 6, 2006
The data source of the respective entries can be found in the documentation .
f1

The THTR-300 ( Thorium was -High-temperature reactor) is a helium-cooled high temperature reactor of the type pebble bed reactor in North Rhine-Westphalia Hamm with an electric power of 300  megawatts . Despite its designation as a thorium reactor , like most nuclear power plants, it essentially gained energy from the fission of uranium-235: 90 percent of its nuclear fuel consisted of thorium, but less than 30 percent of its energy was generated. Because of

  • the inadequate profitability (among other things because the operating results of the AVR Jülich were not included in the planning process),
  • its problematic fuel supply (due to contracts terminated by the US government in 1977 with EURATOM for the supply of highly enriched uranium (HEU) ),
  • the very high construction costs (exceeding the original plans twelve times),
  • its unusually long construction period (16 years),
  • the unexpectedly low long-term stability of the concrete reactor vessel,
  • its susceptibility to failure (failure on average every three days),
  • its problematic management (including attempts to disguise incidents) and
  • its unsatisfactory (regular breaks every six weeks) and short operation

it is widely regarded as one of the biggest technical debacles in post-war Germany.

Location and use

The reactor was located in the Hamm-Uentrop district ( Schmehausen district ) of the city of Hamm in North Rhine-Westphalia on the grounds of the Westfalen power plant . After the functional principle of the high-temperature reactor in pebble- bed design had been tested on the test reactor AVR (Jülich) , the THTR-300 was built as a prototype for the commercial use of high-temperature reactors (HTR). It was put into operation on a trial basis in 1983, handed over to the operator in 1987 and finally shut down in September 1989 for technical, safety and economic considerations after only 423 days of full load operation. He is currently in safe confinement .

Core physics basics of the THTR

Energy generation

As in other nuclear reactors, energy is generated through nuclear fission , which is brought about by thermal neutrons and maintained as a chain reaction in a controlled manner. Graphite instead of water serves as a moderator , similar to the British AGR or the Russian RBMK . Graphite is the main component of the fuel elements in the THTR (see below ). As with other reactor types, the chain reaction is controlled by control rods made of neutron-absorbing material. The peculiarity of the thorium high-temperature reactor, however, is that it uses not only 235 U , but also 233 U as fuel . This is produced from 232 Th in the fuel elements during ongoing reactor operation and partly burned immediately.

It was hoped that there would be better overall utilization of fuels and breeding materials than in light water reactors, since graphite-moderated reactors, for reasons of neutron physics, in principle permit higher burn-ups than conventional light water reactors (albeit lower than heavy-water-moderated reactors such as the CANDU type ). The HTR fuel elements used, however, only allowed limited burn-up due to material-technical reasons, so the theoretical advantage hardly had any effect. For a closed fuel cycle and extensive fuel and raw material utilization, reprocessing would also have been necessary. A THOREX process for thorium-containing fuel elements, which is analogous to the PUREX reprocessing process, has been developed, but has never been implemented on a technical scale; the processing of the HTR fuel, which consists of coated particles embedded in graphite , would be very expensive.

The THTR reactor concept therefore made it possible to partially use the thorium, which is much more abundant on earth than uranium, to generate energy. Fuels containing thorium can, however, also be used in all other reactor types.

If thorium is used, the fresh fuel elements must, for reasons of reactor physics, also contain material that can be used in weapons and can be easily separated. In the case of the THTR-300, this was uranium, which was enriched to 93 percent . Because of this weapons-grade uranium, the THTR fuel elements were legally owned by the EU ( Euratom ) and were only made available to the THTR operator for consumption under Euratom control. Due to the danger of weapons spreading (danger of proliferation ), US President Jimmy Carter stopped delivering highly enriched uranium for high-temperature reactors as early as 1977. Up until then, around 1300 kg of highly enriched uranium had been delivered to Germany for HTR. This decision caused the pebble bed reactor concepts developed later to move away from thorium and envisaged the use of low-enriched uranium fuel (LEU). The THTR itself could only have been converted to LEU fuel with considerable loss of performance, which impaired its medium-term economic perspective and probably contributed to its shutdown. In order not to worsen the reactivity behavior in the event of accidents caused by ingress of water, the heavy metal loading of the fuel elements would have had to be reduced from 11 g per fuel element for U / Th fuel to below 8 g for LEU fuel.

Breeding process

The conversion of thorium into 233 U can be written as the following formula:

In words: a 232 Th atomic nucleus captures a thermal neutron and thus becomes 233 Th. This decays with a half-life of 22.2 minutes through beta decay in 233 Pa ; this core changes to 233 U with a half-life of almost 27 days through a further beta decay . The neutron in the above formula comes from the normal fission process of the 235 U contained in the fuel , or to a lesser extent from the fission of the breeding 233 U. This corresponds to the breeding and combustion of the plutonium when using 238 U as breeding material in the standard fuel of light water reactors .

The THTR did hatch 233 U, but was not a breeder reactor because it hatched less fissile material than it consumed. The original intention to develop pebble bed reactors and especially the THTR-300 as thermal thorium breeder failed because of the excessive neutron losses in HTR, and a. Due to its low power density: Only a maximum of around four percent of the THTR thorium inventory could be used to generate energy, which led to a contribution of almost 30 percent to the reactor's output; Most of the thorium in the fuel elements was intended for final disposal. The THTR worked with a breeding ratio of less than 0.5, which hardly justified its characterization as a near-breeder or upconverter .

In the meantime, thorium is again being discussed more intensively as a breeding material. However, pebble bed reactors are hardly involved, since efficient thorium use would require both breeder reactors and reprocessing ; Both are practically impossible to achieve with pebble bed reactors.

Fuel assemblies and reactor core

In the THTR-300, the fuel elements containing the fissile and breeding material were spheres with a diameter of six centimeters and a mass of around 200 g. These have an outer, fuel-free graphite shell with a thickness of 5 mm. Inside is the above. Fuel in the form of approx. 30,000 coated particles ( English: coated particles , see Pac beads ) embedded in a graphite matrix.

In the THTR-300, double-coated particles without silicon carbide were used as coated spheres ( BISO ). Although these were already considered obsolete from around 1980 compared to TRISO particles (triple coated particles with silicon carbide), the use of TRISO particles in the THTR-300 was no longer possible for technical approval reasons. Each fuel element contained approx. 1 g of 235 U and approx. 10 g of 232 Th in the form of mixed oxides of both heavy metals.

The choice of a mixed oxide fuel element turned out to be a design error, since, contrary to the original expectations, no usable fuel can be recovered when it is reprocessed: In a side reaction to cleavage, 236 U is produced from 235 U, which no longer separates from the hatched fuel 233 U in the mixed oxide leaves. Because of the comparatively high capture cross-section of 236 U for thermal neutrons, the uranium obtained from the reprocessing of THTR-300 fuel elements was not suitable for return to the THTR-300. Attempts to use separate uranium and thorium particles instead of a mixed oxide in order to be able to obtain pure 233 U during reprocessing did not get beyond the experimental stage ( feed / breed concept ) and the completed JUPITER HTR reprocessing plant in Jülich was therefore never able to enter Be put into operation. Before being used in the THTR-300, around 30,000 fuel elements of the THTR type were tested by the Jülich Research Center in the AVR reactor .

The fuel-free shell of the fuel assembly, together with the graphite matrix, is responsible for the mechanical strength of the fuel assembly. Graphite only sublimes at approx. 3500 ° C, i.e. H. Melting of the fuel assemblies is avoided up to this high temperature. However, a considerable amount of radioactivity is released from the fuel assemblies above 1600 ° C. Nevertheless, the preservation of the mechanical stability together with the comparatively low power density represents a limited safety-relevant advantage compared to the fuel rods usually used in light water reactors , which are more prone to overheating. However, the spherical fuel elements of the THTR-300 were combustible (ignition temperature approx. 650 ° C) and an accident with air entering the reactor would have resulted in a graphite fire with high levels of radioactivity being released. Leakage of the steam generator with water / steam access to the core would have led to chemical reactions with graphite with the formation of flammable gases (hydrogen and carbon monoxide).

The THTR-300 reactor did not contain any mounts or guides for the fuel assemblies, but these formed a pebble bed under their own weight (hence the name pebble bed reactor ). As a result, this reactor had the advantage that the core would only contain materials that could withstand temperatures well above the operating temperature. However, when the absorber rods were pushed in when the reactor was shut down, the balls were subjected to very uneven mechanical loads, which led to ball fractures and uneven burning.

After removal from the core, the burn-off, i.e. H. the consumption of nuclear fuel in a fuel assembly is determined. Since this determination in the AVR Jülich did not work satisfactorily, a small auxiliary reactor with 3.9 kg of highly enriched uranium (U / Al alloy) was used in the THTR-300, the output of which increased after a fuel element ball was inserted according to the fissile material content of the ball. Depending on the burn, the balls should either be removed, returned to the edge of the core or in the area of ​​the core axis.

The number of operating elements (fuel elements, graphite and absorber spheres) in the THTR-300 core was 675,000. Mathematically, a maximum core temperature of approx. 1050 ° C was reached in normal operation. In the center, however, the temperatures were probably higher, as measurements in hot gas strands showed.

Functional principle of the THTR

  1. In the THTR-300, helium was passed through the reactor core in the primary circuit under a pressure of approx. 40 bar. The helium, which was cooled to 250 ° C by the heat exchangers (“steam generator”), was sucked in by the cooling gas fans above the steam generator and fed back to the reactor core. As a noble gas, helium has the advantage over the conventional heat carrier water that it does not react chemically with other materials even at elevated temperatures, i.e. it does not cause corrosion . However, this means that metals cannot build up protective oxide layers in helium, which means that impurities released from the graphite have significant corrosion effects on metals. Helium mainly consists of 4 He, which cannot be converted into radioactive substances. However, natural helium contains small amounts of 3 He, which is very easily converted into radioactive tritium and thus represented an essential source of tritium in the THTR-300. The viscosity of gases such as helium increases with increasing temperature, which can have the disadvantageous consequence that hot areas are less cooled.
  2. As it flows through the reactor, the helium absorbs the thermal energy of the nuclear fission process and is pumped to the heat exchangers by cooling gas fans in hot gas channels . In these, the thermal energy is transferred to the secondary circuit operated with water. The primary circuit and the secondary circuit are therefore - as in a pressurized water reactor - separated from one another by metal pipe walls, so that there is no connection between the radioactive primary circuit and the almost non-radioactive secondary circuit.
  3. The steam produced in the steam generators flows through the live steam lines to the high-pressure section of a steam turbine, is then reheated in the steam generators, then flows through the medium and low-pressure sections of a steam turbine, and is finally cooled in the condenser by the actual cooling circuit (tertiary circuit) and as condensate (i.e. Water) down. This condensate is conveyed from the main coolant pumps (water pumps) through the preheaters to the degasser with feed water tank and fed back to the steam generators.
  4. The tertiary cycle has no direct contact with the secondary cycle. The cooling water pumps convey the cooling water to the dry cooling tower, where it is cooled in closed cooling elements by the passing air. The water cooled in this way then flows back to the surface condenser.

Construction and operation

Westphalia power plant with THTR at the bottom right

There were preliminary planning from 1962. The preparation of ready-to-build documents for the THTR-300 nuclear power plant took place from 1966 to 1968 by a consortium of BBC / Krupp , Euratom and Forschungszentrum Jülich , at that time KFA Jülich, under the direction of Rudolf Schulten . The planning work was already carried out parallel to the commissioning of the smaller AVR pebble bed reactor in Jülich, which had the negative consequence that the AVR's operating experience could hardly be incorporated into the THTR concept. This rush in planning and starting construction of the THTR-300 was due to the market launch of light water reactors at the end of the 1960s , with which one wanted to catch up. The owner of the THTR-300 was HKG Hoch Temperatur-Kernkraftwerk GmbH Hamm-Uentrop , founded in 1968 , whose parent companies were six medium-sized and smaller regional electricity suppliers. The THTR-300 was designed as a commercial nuclear power plant to generate electrical energy and was comparable to the reactor in the Fort St. Vrain nuclear power plant (not a pebble bed reactor, but a so-called block-type HTR) in the USA . Since a steel pressure vessel of the required size could not be built, it was designed as an integrated helium-tight prestressed concrete vessel and designed for an internal operating pressure of around 40  bar . The thermal output of the reactor was 750  megawatts . A consortium made up of BBC, Krupp Reaktorbau GmbH and Nukem was commissioned to build the turnkey system .

Five days before the planned first groundbreaking ceremony in June 1971, Krupp left the building consortium and discontinued its activities for pebble bed reactors, as it was in the company's management and a. there were serious doubts about the pebble bed reactor concept due to the operational results of the AVR (Jülich) now available. This led to initial delays of 6 months. After Krupp's exit, the BBC also considered switching from the pebble bed concept to the more undemanding prismatic fuel element of the US HTR, which, however, met with resistance from Jülich. Jülich could not prevent the beginning of extensive planning and even a licensing procedure for a larger HTR with prismatic fuel elements, which was to be erected next to the THTR, in 1973, which was abandoned after a few years in favor of planning for pressurized water reactors due to the technical difficulties of HTR. The projected and contractually stipulated five-year construction period for the THTR became 15 years due to technical problems and stricter requirements, the construction costs rose from an estimated 300-350 million DM in 1968 and 690 million DM at the start of construction to finally more than four billion DM. The federal government borne 63 percent and the state of North Rhine-Westphalia eleven percent of the construction costs. The financial contribution through the investment subsidy , which covered almost ten percent of the construction costs, also came from tax revenues . The power plant was inaugurated by the Federal Minister of Research at the time, Heinz Riesenhuber, on September 13, 1983 and was commissioned for the first time with a self-sustaining chain reaction . So many problems arose during the commissioning phase that Stadtwerke Bremen surrendered its share of the THTR-300 to the HKG main shareholder, Vereinigte Elektrizitätswerke Westfalen (VEW), at a symbolic price of DM 1 in order to avoid the liability risk. Shortly afterwards there were further, albeit unsuccessful, attempts by minority shareholders (including Stadtwerke Bielefeld and Wuppertal) to sell their shares or to transfer them to VEW. The partial license of the nuclear licensing authority for regular operation was only granted on April 9, 1985. The THTR did not receive a permanent operating license, but an operating license limited to 1100 full load days or until 1992 at the latest, which could have been converted into a continuous operating license after successful performance test operation. Furthermore, a coherent fuel element disposal concept should have been submitted after 600 days of full load operation. The first electricity was fed into the grid on November 16, 1985. Because of the considerable disruptions in the commissioning phase, HKG refused to take over the plant until June 1, 1987.

From 1985 until its decommissioning in 1989, the THTR-300 recorded only 16,410 operating hours with an electrical energy output of 2,756,000 MWh (gross: 2,881,000 MWh). That corresponds to 423 full load days. The work availability of at least 70 percent required for an economical operation was not achieved in any operating year (1988: 41 percent). There was a purchase guarantee for the electricity generated in the THTR at a price based on hard coal power generation, which at that time was around 40% above the purchase price for light water reactors ; this is to be interpreted as additional subsidization of the THTR.

In 1982 a group of companies from Brown, Boveri & Cie. and Hoch Temperatur Reaktorbau GmbH (HRB) with the HTR-500 is a successor to the THTR-300 with a thermal output of 1,250 megawatts and an electrical output of 500 megawatts. There was an approval procedure, but the electricity industry rejected a construction contract because of the significantly higher installation costs compared to light water reactors. The Hamm nuclear power plant was to be built alongside the THTR-300 . However, the plan was rejected. In the immediate vicinity of the THTR-300 is the Westphalia power plant for generating electricity from coal.

Problems and incidents

Incidents (according to the IAEA classification INES: ≥ 2, which was only introduced in 1990, after THTR shutdown : ≥ 2) did not occur in the THTR-300 according to the information provided by the nuclear supervisory authority. This is doubted by the environmental movement, which suspects a deliberate release during events on May 4, 1986 (see here ), which could be significantly higher than previously admitted and which might have to be classified as an accident. The more than 120 known reportable events with only 423 days of full-load operation were often taken as evidence of the immaturity of the pebble bed technology. The failure of the safety-relevant humidity sensors on September 7, 1985 was assigned to the second highest reporting category B valid at the time. The THTR-300 was originally considered to be much more accident-proof than other reactor types due to the functional principle in which no core meltdown can occur. However, it was already shown in 1984 by the Institute for Nuclear Safety Research at Forschungszentrum Jülich that a loss of coolant in the THTR-300 leads to very high temperatures (2300 ° C), which results in a massive release of radioactivity even without a core meltdown. The pre-stressed concrete tank also proved to be disadvantageous, as concrete decomposes when heated, releasing water vapor and the resulting water vapor reacts chemically with the hot graphite. An expert report for the NRW state government from 1988, which was kept confidential for a long time, certified that the THTR-300 even posed a risk of nuclear runaway in the event of accidents caused by water ingress due to steam generator pipe bursts , including scenarios similar to the Chernobyl nuclear disaster . This similarity to the Chernobyl nuclear reactor is caused by the use of graphite as a moderator in both reactor types. Proponents of pebble bed technology could not refute this report in the course of the investigations of the AVR expert group .

There were also problems with operational safety. Among other things, the shut-off rods, which were pushed into the pebble from above, caused much more frequent breakage than previously calculated damage to the fuel assemblies. A total of 25,000 damaged fuel assemblies were found, which was about a thousand times what was expected for 40 years of operation. In 1988, after every six weeks of operation, the reactor had to be shut down and run down for at least one week in order to remove defective fuel elements from the collecting container. The high breakage rate was probably a consequence of the unfavorable friction properties in helium, which had not been sufficiently investigated for the THTR-300. The friction of the absorber rods could be reduced by feeding in ammonia , but this led to an inadmissibly high rate of corrosion on metallic components. The resulting ball fracture threatened to worsen the cooling of the reactor by clogging the cooling gas holes in the floor reflector; For any future systems, a design was therefore proposed that should be less prone to clogging.

On November 23, 1985, 7 shutdown rods did not go in completely when attempting to shut down the reactor, but got stuck in the pebble because the ammonia feed was missing. The insulation of the concrete was insufficient in places, so that it became too hot; repair was not possible and the damaged area had to be inspected regularly, which meant that the reactor had to be shut down every time. Because of the friction problems already mentioned and possibly also the ball breakage, the balls did not flow as expected, but in the center by a factor of 5 to 10 faster than at the edge. This caused the reactor in the lower center to get at least 150 ° C too hot.

Presumably through excessively hot strands of gas, 36 retaining bolts of the hot gas line were damaged in such a way that they broke in 1988; Individual graphite dowels in the ceramic reactor area also failed. It was not possible to repair the damage to the bolts and dowels. A ball removal was only possible with reduced performance and could therefore only be carried out on Sundays. In addition, the manufacture of the spherical fuel elements was not guaranteed and their reprocessing was not possible. Therefore, the now abandoned high-temperature reactors in South Africa were planned without reprocessing; this disadvantage should be partially compensated for by a somewhat higher burn-up compared to reactors with light water moderation and thus better utilization of the available nuclear fuel .

Emission of radioactive aerosols on May 4, 1986 immediately after the Chernobyl accident

A reportable incident with the release of radioactivity on May 4, 1986 occurred shortly after radioactive precipitation from the Chernobyl accident fell over Hamm. The emissions from the THTR were initially not noticed. However, an anonymous informant from the workforce of the THTR-300 informed supervisory authorities and environmental organizations about a hidden radioactive emission on May 4, 1986. The operator denied any irregularity in an express letter dated May 12, 1986 to all members of the NRW state parliament. Only when an unusually high concentration of 233 Pa was detected in the chimney exhaust air of the THTR-300, which could not come from Chernobyl but only from the thorium of broken fuel elements of the THTR-300, it gradually became clear that it was from the THTR- 300 significant radioactive emissions must have been in the area. According to internal investigations by HKG, more than 40% of the released activity attributable to the THTR was 233 Pa. On May 30, 1986, the Öko-Institut claimed that about 75 percent of the activity near the THTR was due to it itself. A little later, Dietrich Grönemeyer reported high releases from the THTR to the authorities. On June 3, 1986, the THTR was shut down by a nuclear law directive from the Düsseldorf supervisory authority until it was cleared up. The instruction was necessary because the THTR operators did not want to voluntarily forego a restart. On the same day, the operators finally declared that the cause of the release of radioactivity was a malfunction in the charging system of the reactor, but rejected the claims of the Öko-Institut. Until then, the operators had claimed that it was a permissible, non-reportable discharge of radioactivity, i.e. an emission on a route provided for this purpose and below limit values. In contrast, emissions on routes not intended for this purpose and / or above limit values ​​are notifiable releases. The state government of North Rhine-Westphalia took the view at the time that, because of the emission route, it was a reportable release that had not been duly reported. The decommissioning order was revoked on June 13, 1986 with conditions.

THTR critics suspected that the HKG had hidden the radioactive emission in the hope that it could not be detected because of the radioactivity from Chernobyl; The reason for hiding could have been that the incident points to some weak points in pebble bed reactors, namely radioactive dust, broken pebbles and a lack of full-pressure containment. This incident (especially the alleged attempts to conceal it) and the resulting intensive media coverage significantly worsened the previously positive image of pebble bed reactors in the German public. The physicist Lothar Hahn stated in a report on the safety of the THTR-300 in June 1986 against the background of this incident: The conclusion can already be drawn today that the technology of the pebble bed reactor has failed.

Results of the regulatory investigation

The supervisory authority in Düsseldorf began on May 30, 1986 with intensive investigations into aerosol emissions on May 4, 1986. The results are summarized in the radiation protection report of the NRW state government for the 2nd quarter as follows:

On May 4, 1986, the fuel element loading system was not operated in automatic mode, but in manual mode, contrary to the operating rules, for the introduction of absorber elements. An operating error led to a malfunction in the process flow. As a result, the infeed section of the charging system, which contained helium contaminated with radioactive aerosols, was relieved of pressure to the exhaust air chimney, with the result that radioactive aerosols were emitted via the exhaust air chimney (150 m height).

The aerosol activity emitted on May 4, 1986 is not greater than 2 * 10 8 Bq; This value is the result of the evaluation of the aerosol collection filter for all charges in KW 18, from which the previous load from the effects of the reactor accident in Chernobyl has to be deducted in order to arrive at the value of the emissions caused by the operation of the THTR. Because of u. a. Difficulties in determining the Chernobyl content on the filter due to the limited accuracy of the measurement, it is not possible to clearly determine whether the limit values ​​approved for releases of radioactive substances from the THTR have not been slightly exceeded.

Even if it is assumed, however, that the emission of 2 * 10 8 Bq is exclusively due to the THTR, a mathematical estimate of the soil contamination would result in a value of <1 Bq / m² at the worst starting point. This is at a chimney height of 150 m and the meteorological dispersion and deposition conditions on May 4, 1986 at a distance of 2000 to 3000 m from the THTR-300; a metrological proof of this contamination contribution is not possible.

The limit values ​​for the THTR are:

  • Maximum permissible aerosol emission totaled over 180 consecutive days: 1.85 × 10 8 Bq
  • Maximum allowable emission on a single day: 0.74 × 10 8 Bq.

The TÜV assessor suspects that these limit values ​​were just undercut. The authority assumes helium emissions in the event of a sudden release of <0.5 m³. The event was not formally classified as an incident.

Uncertainties and weaknesses of the regulatory investigation

The final report mentions a number of circumstances which could have impaired the informative value of the report. These weak points, above all the temporary interruption of the recording of emission data by the operator, gain additional importance due to the later discussed allegations (2016) of a former THTR employee that the issue was deliberate impulse emissions of radioactive aerosols.

1. Approximately at the same time as the automatic hazard report was received in the reactor control room "Aerosol activity concentration high at the chimney" due to a shock-like emission, the operator interrupted the recording of the aerosol-borne activity emitted via the chimney for an "in a phase when activity emissions rose again", according to the authorities. no longer clearly determinable period ". The operator justified this with measures for "time adjustment" on the recording recorder. The operator briefly noted the process on the measurement record. There is no monitoring of the aerosol activity release via the chimney for this period. The authority writes: It has already been objected that a time correction has been made to the measurement record for the aerosol activity concentration while an increased value was displayed. In its final report, the supervisory authority discussed the possibility of additional activity taxes in this time window, but ultimately rejected this. However, taking into account all the uncertainties, the authorities say: A clear determination of the aerosol release on May 4, 1986 is not possible.

2. The authority continues to criticize the operator's behavior: The measures to be taken in accordance with the safety rules .... when the danger message "high aerosol activity concentration" is pending, namely the immediate replacement of one of the two redundant suspended matter filters (weekly filter), the aerosol / iodine sample collector and its immediate replacement Measurements in the radiation protection laboratory and the additional taking of a representative sample for the evaluation of radioactive noble gases were omitted .

3. According to the authorities, the operator did not adequately document the processes in the logbooks. There is a short entry in the shift log about the malfunction in the loading system, but the authorities criticize: An entry in the malfunction log was not found . When the automatic alarm message "Aerosol activity concentration at the chimney is high" is received, the authorities say: In the shift log, however, neither the alarm message nor what was initiated by the shift personnel are entered. The sequence of events assumed by the authority is therefore essentially based on subsequent surveys of the staff and later information from the operator.

4. Problems in the charging system were reported to the supervisory authority on May 8, 1986, but without referring to the danger report “high aerosol activity concentration in the chimney”. According to the operator, this was due to the fact that a connection between the malfunctions in the charging system and the simultaneous aerosol emissions had not been recognized. This delayed their examination by several weeks and made them considerably more difficult or possibly made them partially impossible.

5. The high level of soil contamination due to the Chernobyl accident only allowed the determination of the immission values ​​from the THTR to a limited extent: According to information provided by the supervisory authority on the basis of dispersion calculations over the chimney, the most unfavorable starting point was for the rain-free weather conditions on the evening of May 4th for an emission of 0.2 GBq of activity emitted via the chimney with aerosol activities of <1 Bq / m² to be expected; the soil contamination in the THTR area caused by Chernobyl, on the other hand, was up to 10,000 Bq / m² according to the authorities.

6. The final report lacks key information on aerosol emissions, such as the measured nuclide spectrum. At that time unpublished, but now accessible documents of the official investigation show that, according to operator information, the aerosol emissions (total 0.102 GBq) attributable to the THTR consisted of 44% 233 Pa, 18% 60 Co, 10% 181 Hf. The remainder were exclusively activation products of steel. Fission products found should not come from the THTR, but from the Chernobyl cloud. According to the operator, the high proportion of 233 Pa, an intermediate product in the incubation of 233 U from thorium and therefore from the nuclear fuel, is difficult to reconcile with the aerosol emission sequence assumed by the authority: the authority assumes that Most of the aerosols emitted do not come from the primary circuit, but from the discharge lines to the chimney.

In the opinion of the environmental movement, the following fact is important for the assessment of the official report: In 2014, based on the investigations of an independent group of experts appointed by Forschungszentrum Jülich , it became clear that the same supervisory authority was responsible for the pebble bed reactor AVR Jülich, the predecessor reactor of the THTR, despite good knowledge of the circumstances had classified a possibly serious incident as an event of subordinate safety-related importance (see AVR expert group ).

Reports of an alleged deliberate release of aerosol-borne radioactivity on May 4, 1986

Former THTR manager Hermann Schollmeyer claimed in May 2016 that the release of radioactive aerosols into the environment was deliberate. Some of the graphite spheres in the reactor were damaged mainly as a result of sudden shutdowns; Dust and chipped particles would have clogged the pipes. The pipes would have been blown out of the cooling circuit with helium gas, the filters required for this had already been ordered and were available two to three weeks later. After the Chernobyl accident it was assumed that blowing out the air without a filter would go undetected because of the radioactive contamination already present in the area. The current operator RWE and the operations manager at the time contradicted this representation. The regulator has announced that it will carefully examine the new allegations about the events. The safety expert for pebble bed reactors Rainer Moormann considers the information provided by Schollmeyer to be plausible. Immediately after the release there were reports that the emission had been deliberate; these reports were discussed in the NRW state parliament at the time. The environmental movement now suspects that the failure of the measuring equipment during the incident and the alleged removal of many traces of the incident were also deliberately carried out and that the radioactive emissions could be greater than previously assumed. She has called for clarification - also through parliamentary channels. Moormann has submitted a document that appears to confirm parts of Schollmeyer's statements. The responsible Minister of North Rhine-Westphalia stated on June 15, 2016 that there was no evidence to support Schollmeyer's claims; He declined further investigations.

Thyroid cancer in the vicinity of the THTR-300

In 2013 it became known through an official investigation that in the vicinity of the THTR-300 there were “statistically significantly increased rates for thyroid cancer in women (and not in men) in the years 2008–2010”. The study sees no concrete evidence for the THTR as a cause and suspects a "screening effect" from more frequent cancer screening examinations. This assessment is contradicted by parts of the environmental movement. The cancer incidence study was originally requested by the environmental movement because of the uncertainties surrounding the radioactivity emitted in the May 4, 1986 incident.

Decommissioning and safe confinement

During the standstill phase from September 1988 due to broken retaining bolts in the hot gas line, HKG submitted a "precautionary closure request" to the federal and state governments of North Rhine-Westphalia at the end of November 1988 in order to draw attention to their precarious financial situation: The operation of the THTR had turned out differently than forecast -300 was shown to be in high deficit and HKG's financial reserves were largely exhausted. Although the risk-sharing agreement for the THTR provided that the public sector assumed 90% of the operating losses for the first three years of operation, this takeover rate fell to 70% thereafter. Without a permanent solution to these financial problems, the supervisory authority no longer saw the conditions for continued operation of the THTR as given, and the reactor remained shut down.
In the summer of 1989 HKG came to the brink of insolvency and had to be supported by the federal government with 92 million DM and the state of North Rhine-Westphalia with 65 million DM, since the parent companies of the HKG did not want to make any further payments without higher state subsidies. In addition, the THTR fuel element factory in Hanau was shut down in 1988 for safety reasons.

Since the USA no longer supplied any highly enriched (and thus weapons-grade) uranium for THTR operations, the reactor would have had to be converted to low-enriched uranium with no or reduced thorium addition. This would have required a new approval procedure with an uncertain outcome and would have resulted in a considerable reduction in performance. Therefore, this option was soon abandoned and with the existing reserves only standard fuel was available for a good two years of operation. Due to the considerable, also economic risk of the THTR operation, the operator considered additional reserves of DM 650 million to be necessary even for a two-year phase-out operation, since a corresponding increase in deficits was expected up to 1991 and only far too little reserves for disposal were present. The CEO of HKG main shareholder VEW Klaus Knizia even spoke out in favor of a quick THTR shutdown so that the HTR development as a whole would not be burdened by further disruptions at the THTR. The auditing company Treuarbeit AG also issued an unfavorable medium-term economic forecast for the THTR-300.
Negotiations between the federal government, the state of North Rhine-Westphalia and the electricity industry on these reserves failed because neither the state of North Rhine-Westphalia nor the electricity industry wanted to make significant contributions to them. Due to economic, technical and safety considerations as well as the dwindling interest of the energy industry in pebble bed reactors, the decommissioning of the THTR-300 was then decided on September 1, 1989, which was then applied for by the HKG to the supervisory authority on September 26, 1989 in accordance with the Atomic Energy Act.

In 1989, the HKG proposed to the federal and state governments of North Rhine-Westphalia that the THTR should be transferred to Forschungszentrum Jülich for dismantling after it had been safely enclosed. However, since this would in fact have been tantamount to shifting the responsibility for disposal, the proposal was not implemented.
From October 1993 to April 1995 the spent, intact and broken fuel elements were transported in 305 fuel element casks of the Castor type to the Ahaus transport cask storage facility; two castors contain the fuel elements of the THTR auxiliary reactor for burn-up measurements. Because of the short operating time, only an average fuel element burnup of approx. 5.2 percent fima was achieved (target value 11.4 percent fima). Therefore, the highly enriched uranium is only incompletely consumed and there is a clear risk of proliferation in the discharged THTR fuel elements. According to Moormann's calculations, the unused highly enriched uranium should be sufficient for approx. Six to twelve atomic bombs of the Hiroshima type. Approx. 1 to 1.6 kg of fissile material (corresponding to 2000 to 3000 fuel elements) are still suspected in the reactor.

The unused, fresh 362,000 THTR fuel elements were processed in the Scottish reprocessing plant Dounreay , the highly enriched uranium was returned to Germany and used in the Munich II research reactor . The reactor itself was transferred to the so-called " safe enclosure " by 1997 and continues to generate costs of 6.5 million euros annually. Although these costs were borne exclusively by the public purse until 2009, the owners received tax breaks from the EU for the closure; A political controversy arose in 2011 over an ongoing application to extend these tax breaks.
The reactor still contains around 390 tons of radioactive plant components, plus the partially contaminated prestressed concrete container. In December 2017, it was decided Template: future / in 5 yearsto begin demolition in 2028 , after the radioactivity had partially subsided, for which around 20 years are estimated. In 2007, the owner estimated the costs for disposal without final storage at approx. 350 million euros, in 2011 it was 1 billion euros. The comparison with the similar US HTGR Fort St. Vrain (prismatic fuel elements, 330 MW el ), which was also shut down after unsatisfactory operation in 1988 and which could be dismantled and converted into a gas power plant by 1997 at a cost of 174 million USD, shows the difficult dismantling conditions at the THTR. In 2012 HKG only had own funds of € 41.5 million. Due to the legal form of a GmbH, direct liability on the HKG shareholders to cover the disposal costs is not possible, so that the assumption of costs is unclear. Unlimited guarantees have already been issued in the area, for example by the Wuppertaler Stadtwerke (WSW) towards the Hattingen joint venture. The possible consequences of assuming costs for the municipal utilities and municipalities involved are also unclear, since some of these municipalities are financially poor.

In a 2015 study by the Hertie School of Governance , the THTR is counted among the biggest undesirable developments in German projects over the past 55 years.

In his book The Second Law of Economics, the economic physicist Reiner Kümmel quotes the banker and businessman Hermann Josef Werhahn , who, according to his own assessment, has “accompanied reactor technology with spherical fuel elements as a consultant from the start”, with the statement that the possibility of electricity and generating heat in decentralized communal systems, which ran counter to the commercial interests of the major energy suppliers. Werhahn, however, has often come out with very positive, but scientifically unfounded assessments of the HTR such as "rocket-proof", "foolproof", "rogue-proof" or "final storage issue solved". The environmental researcher Klaus Traube , on the other hand, sees the failure of the pebble bed HTR in Germany to be due to its technical and safety inferiority compared to the light water reactor , since high-temperature reactors represent a further development of the military graphite reactors for the production of plutonium, which are less suitable as power reactors, while LWR from the beginning as power reactors designed and optimized.

Operating company (as of 2010)

Operating elements in trade

Graphitic operating elements of the THTR without nuclear fuel have already been offered on eBay . According to the NRW Ministry of Economics, non-irradiated and therefore non-radioactive operating elements were given to collectors and interested parties when the reactor was shut down. So far there is no evidence that spherical fuel elements with nuclear fuel, i.e. highly enriched weapons-grade uranium, have also been misused. All previous finds, at Forschungszentrum Jülich z. B. in landfills and in sewer pipes, proved to be free of nuclear fuel and not radioactive.

Microspheres in the THTR environment

In 2011, microspheres were discovered in the vicinity of the THTR, some of which are similar to the coated particles of the THTR-300. Similar microspheres play a role in the discussion about the accumulation of leukemia in the Elbmarsch . Because of the uncertainties regarding the radioactivity emitted in the incident on May 4, 1986 , the suspicion arose that it could be fuel particles from the THTR-300. The fuel is embedded in the graphite of the fuel elements in the form of coated particles with a diameter of less than 1 mm. The coating of the fuel element particles with pyrocarbon serves to hold back the fission products. Analyzes by the NRW investigation offices could not detect any increased radioactivity in the microspheres. However, criticism has been expressed of the measuring methods used by the investigation offices.

Effects of early shutdown on HTR development

The problems and the shutdown of the THTR-300 led to the extensive end of pebble bed reactor development in Germany. Negotiations for the market launch of the HTR module (200 MW th ) developed at Siemens with the chemical company Hoechst , the chemical combine Leuna / GDR, the US Department of Defense (for a plant for the production of tritium for hydrogen bombs ) and the Soviet Union failed against the background of the THTR -300; a location-independent approval procedure for the HTR module in Lower Saxony was canceled without result by the applicant, the energy company Brigitta & Elwerath , in 1988.
The company Hoch Temperatur-Reaktorbau (HRB) was then dissolved, as were the company parts for HTR development at Siemens / Interatom, only a small company remained to market the HTR know-how that had been built up. The fuel element development at Nukem has been discontinued. The Jülich nuclear research facility was renamed Forschungszentrum Jülich and the HTR research areas were reduced to 50 people in 1989, with a steady decline until 2005; However, the HTR-friendly NRW state government, which was in office from 2005 to 2010, reinforced HTR research again. After a lengthy public discussion, the Supervisory Board of Forschungszentrum Jülich only decided in May 2014 to stop HTR research in Jülich at the end of 2014 and to shut down the test stands.

From 1988 onwards, despite the embargoes against South Africa and China that were in force at the time, the pebble pile advocates managed to transfer their know-how to these countries. In South Africa a small pebble bed reactor (500 kW) was originally planned for military purposes (nuclear submarine), which is to be seen in connection with the nuclear weapons of the apartheid government . After the end of apartheid, it became a completely civil project, but it finally failed in 2010.
In China, a small pebble bed reactor (HTR-10) was built near Beijing . Since 2005, the HTR-10 has only rarely been in operation, which is attributed to the prioritization of the larger successor reactor HTR-PM by proponents of the pebble bed, but which critics associate with technical problems with ball circulation.

Due to the very reserved attitude of the German energy suppliers and the reactor building industry towards pebble bed reactors, which is mainly caused by the failure of the THTR-300, there has been no renaissance of this technology in Germany after the THTR-300. Nevertheless, there is still a lobby for pebble-bed reactors in Germany. a. Owners of the Werhahn group, the LaRouche movement , individual conservative politicians, especially from North Rhine-Westphalia, national conservative circles as well as the former environmental politician Fritz Vahrenholt and the economist Hans-Werner Sinn include.

Attempts by this lobby to revive the pebble bed technology after the nuclear disaster in Fukushima under the motto “change instead of getting out” (meaning the change to supposedly safe pebble bed reactors), fizzled out without any appreciable response. The assessment of the THTR-300 is controversial within the pebble-bed lobby: While one group admits that the THTR-300 and its influence on the shutdown were major technical difficulties and that it is a fundamentally different concept, others see the THTR-300 as a success and speak of "pure politically induced shutdown ". However, this is contradicted by the fact that no new pebble bed reactor has been in continuous operation worldwide for years.

Dry cooling tower

The THTR-300 was equipped with the largest dry cooling tower in the world at the time . On September 10, 1991, the cooling tower was blown up. Using it for the neighboring coal-fired power plant in Westphalia was impractical, as its air-water heat exchangers became soiled extremely quickly even when they were used for the THTR300 in the agricultural environment, so that the nuclear power plant had to be operated at partial load at times between the cleaning cycles. The plan to keep it as a technical monument failed because of the costs.

Technical specifications
design type Dry cooling tower
Base diameter 141 m
Upper edge of rope net jacket 147 m
Height of the air inlet opening 19 m
Height of the mast 181 m
Diameter of the mast 7 m
Amount of water 31,720 m³ / hour
Hot water temperature 38.4 ° C
Cold water temperature 26.5 ° C

Data of the reactor block

Reactor block Reactor type net
power 		gross
power 		start of building Network
synchronization 		Commercialization
of essential operation 		switching off
processing
THTR-300 Thorium high temperature reactor 296 MW 308 MW May 1, 1971 November 16, 1985 June 1, 1987 September 29, 1988
Technical specifications THTR-300
thermal performance 759.5 MW
electrical power 307.5 MW
Efficiency 40.49%
Medium power density 6 MW / m³
Reactor core height / diameter 6 m / 5.6 m
Fissile material 235 U
Height of reactor pressure vessel 25.5 m
Reactor pressure vessel diameter 24.8 m
Mass of fissile material 344 kg
Breeding material 232 Th
Mass of the breeding material 6400 kg
Fissile material content in heavy metal use 5.4%
Absorber material B 4 C
Coolant Hey
Inlet temperature 250 ° C
Outlet temperature 750 ° C
pressure 39.2 bar (3.92 MPa)
Work equipment H 2 O
Feed water temperature 180 ° C
Live steam temperature 530 ° C
Live steam pressure 177.5 bar (17.75 MPa)

literature

  • BG Brodda, E. Merz: Gas-chromatographic monitoring of the extraction agent in the reprocessing of HTR fuel elements. In: Fresenius' Journal for Analytical Chemistry. 273, 1975, p. 113, doi : 10.1007 / BF00426269 .
  • Consideration for the continuation of the high-temperature reactor line from the point of view of VEW. Lecture on November 13, 1981 at the Ministry of Economics, Medium-sized Enterprises and Transport of the State of North Rhine-Westphalia in Düsseldorf. In: Westphalian economic history. Sources on economy, society and technology from the 18th to the 20th century. Edited by Karl-Peter Ellerbrock. Münster, 2017, ISBN 978-3-402-13171-8 , pp. 692–693.

Web links

Commons : THTR-300  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ Westfälischer Anzeiger September 13, 2013 THTR: The billion-dollar grave of Uentrop is accessed on September 13th http://www.wa.de/lokales/hamm/uentrop/thtr-millionengrab-hamm-uentrop-wird-jahre-3099260.html 2013
  2. ↑ a b E. Merz, reprocessing of thorium-containing nuclear fuels in the light of proliferation-safe fuel cycles, Naturwissenschaften 65 (1978) 424-31
  3. ↑ S. Brandes: THE GLOBE REACTOR AS A THERMAL THORIUM BROTHER. KFA report Jül-474-RG (1967)
  4. ↑ a b Die Zeit July 19, 1968 Hot German breeder http://www.zeit.de/1968/29/heisser-deutscher-brueter
  5. ↑ E. Merz, H. Jauer, M.Laser: Study on the further treatment of spent fuel elements from thorium high-temperature reactors with spherical fuel elements. Report Juel-0943 (1973)
  6. ↑ a b J. Fassbender et al., Determination of radiation doses in the vicinity of the THTR-300 as a result of an assumed core heating accident , report Juel-Spez 275 (1984)
  7. ↑ Rainer Moormann , Air ingress and graphite burning in HTRs: A survey of analytical examinations performed with the code REACT / THERMIX, Forschungszentrum Jülich, report Jül-3062 (1992)
  8. ↑ R.Moormann, Phenomenology of Graphite Burning in Air Ingress Accidents of HTRs, Science and Technology of Nuclear Installations, Volume 2011 (2011), Article ID 589747, 13 pages, http://www.hindawi.com/journals/stni/ 2011/589747 / ref /
  9. ↑ D. Denig, Gas-cooled high-temperature reactors, Thiemig Vlg. (1972)
  10. ↑ J. Quadakkers, Corrosion of high temperature alloys in the primary circuit helium of high temperature gas cooled reactors. Materials and corrosion 36 (1985) pp 141-150 and 335-347
  11. ↑ http://www.thtr.de/aktuelles-ddu.htm
  12. ↑ Brochure 300 MW nuclear power plant with thorium high temperature reactor (THTR-300) of the HKG in Hamm-Uentrop of the consortium BBC / HRB / Nukem
  13. ↑ Die Zeit March 22, 1974 http://www.zeit.de/1974/13/was-eva-trennt-heizt-adam-an/seite-4
  14. ↑ Der Spiegel, 24/1986 of June 9, 1986, page 29, “Environmentally friendly in metropolitan areas” (accessed June 15, 2011)
  15. ↑ Thorium reactor in Hamm-Uentrop: Once nuclear power and back. FAZ Wirtschaft April 23, 2011 http://www.faz.net/aktuell/wirtschaft/wirtschaftspektiven/energiepolitik/thorium-reaktor-in-hamm-uentrop-einmal-atomkraft-und-zurueck-1627483.html
  16. ↑ a b c U. Kirchner, The High Temperature Reactor, Campus Research Vol. 667 (1991)
  17. ↑ Atomwirtschaft, May 1989, p. 259
  18. ↑ a b c d R.Moormann on the Schollmeyer information, document from June 6, 2016: http://www.reaktorpleite.de/images/stories/pdf/THTR-St%C3%B6rfall-Moormann.pdf
  19. ↑ Selection of important reportable events in: http://www.reaktorpleite.de/die-thtr-pannenserie.html
  20. ↑ www.reaktorpleite.de
  21. ↑ http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-10429.pdf
  22. ↑ http://www.iaea.org/inisnkm/nkm/aws/htgr/fulltext/htr2004_h01.pdf
  23. ↑ http://www.patent-de.com/19970306/DE19547652C1.html
  24. ↑ a b Facts, October 21, 2004, pages 61–64, Atomkraft, yes please! - Chinese nuclear physicists have revived reactor technology believed to be forgotten (PDF; 5 MB)
  25. ↑ R. Bäumer: Selected topics from the operation of the THTR 300 . VGB Kraftwerkstechnik 69 (1989) 158-64
  26. ↑ a b Der Spiegel, 8/1989 of February 20, 1989, page 103, "Is bad - the ambitious project of a high-temperature reactor is over - but scrapping is too expensive."
  27. ↑ Nature News, February 23, 2010 Pebble bed nuclear reactor gets pulled (English)
  28. ↑ a b Der Spiegel, 24/1986 of June 9, 1986, page 28, "Sparkling eyes - the hammer reactor type was considered promising - until the accident at the beginning of May."
  29. ↑ FAZ.NET, March 31, 2011, Thorium test reactor: The most beautiful of machines - atomic debate
  30. ^ Die Zeit, June 9, 1986, incident - but with whom? - Operator and Ministry accuse each other
  31. ↑ https://www.landtag.nrw.de/portal/WWW/dokumentenarchiv/Dokument?Id=MMZ10%2F391
  32. ↑ a b Heske, Dr. Wahsweiler, Vey: HKG file note L 55/86 (AZ 28c-28k-422-423-424) from May 22, 1986, table 4.1.
  33. ^ City of Hamm: measurements by Dr. Grönemeyer in the immediate vicinity of the THTR. Letter to MWMT Düsseldorf dated June 12, 1986. Reference: 32 / 321-0. Can be viewed according to UIG at MWEIMH, Düsseldorf
  34. ↑ http://www.reaktorpleite.de/component/content/article.html?id=424:thtr-rundbrief-nr-139-juni-2012
  35. ^ Declaration by the Minister for Economics, Medium-Sized Enterprises and Technology in the Landtag of North Rhine-Westphalia on June 4, 1986, plenary minutes 10-24
  36. ↑ Justification for the atomic order of June 3, 1986 by the Minister for Economics, Small and Medium-Sized Enterprises and Technology, presented in the state parliament of North Rhine-Westphalia on June 4, 1986, plenary minutes 10-24
  37. ↑ a b c d e f g h i j k l MWMV template 10 / 561-1, August 1986 www.landtag.nrw.de
  38. ↑ a b Landtag NRW, plenary protocol 10/24 June 4, 1986 https://www.landtag.nrw.de/portal/WWW/dokumentenarchiv/Dokument?Id=MMP10%2F24%7C1714%7C1727
  39. ↑ Lothar Hahn: Basic safety problems with the high-temperature reactor and particular deficits with the THTR-300. Report on the THTR-300 (June 1986, online )
  40. ↑ https://www.wa.de/hamm/neue-vorwuerfe-thtr-hamm-radioaktiv-wolke-tschernobyl-genutzt-gefaehrliches-material-entsorgen-6417525.html
  41. ↑ Astrid Houben and Rainer Kellers: Hamm-Uentrop: Radiation intentionally released? , WDR , May 20, 2016
  42. ↑ http://www1.wdr.de/fernsehen/aktuelle-stunde/stoerfall-hamm-uentrop-zeitzeuge-schollmeyer-100.html
  43. ↑ https://www.neues-deutschland.de/artikel/1012479.atomreaktor-offenbar-radioaktivitaet-absichtlich-freigesetzt.html
  44. ↑ http://www1.wdr.de/nachrichten/ruhrgebiet/reaktor-stoerfall-wird-nicht-neu-untersucht-hamm-uentrop-100.html
  45. ↑ Report on Cancer Frequency Investigation 2013
  46. ↑ http://www.berliner-kurier.de/panorama/25-jahre-nach-stilllege-mysterioes--krebs-rate-um-atomreaktor-in-hamm-gestiegen,7169224,25451972.html
  47. ↑ http://www.ksta.de/gesundheit/-atomreaktor-erhoehte-krebsrate-in-hamm-uentrop,15938564,25451008.html
  48. ↑ a b c Der Spiegel, 29/1989 of July 17, 1989, page 74, Hamm nuclear ruin : Does Bonn pay for the demolition?
  49. ↑ German Bundestag printed matter 11/5144 September 6, 1989 http://dipbt.bundestag.de/doc/btd/11/051/1105144.pdf
  50. ↑ NRW-Landtag, Economic Committee, meeting on September 6, 1989, Minutes MMA 10 / 1292_1-15
  51. ↑ Jülich is to lead the demolition of the reactor. Jülich News July 18, 1989
  52. ↑ a b S. Plätzer et al. Unloading of the THTR reactor core and spent fuel management of the THTR-300 http://pbadupws.nrc.gov/docs/ML0215/ML021510148.pdf
  53. ↑ R.Moormann: The Jülich nuclear debacle ( Memento from March 11, 2014 in the Internet Archive ), March 8, 2014 (PDF)
  54. ↑ Atomic bomb alarm in Ahaus taz August 28, 2013 http://www.taz.de/1/archiv/digitaz/artikel/?ressort=wu&dig=2013%2F08%2F28%2Fa0074&cHash=e362eb9fdb88535799a9e1d062f20947
  55. ↑ http://www.reaktorpleite.de/images/stories/pdf/Waffentauglichkeit-Oct2014.pdf
  56. ↑ Executive Summary Letter of Compliance Assessment Report - Thorium High Temperature Reactor Graphite Waste. (PDF; 37.5 kB) Nuclear Decommissioning Authority , Radioactive Waste Management Directorate, March 5, 2010, accessed on August 10, 2019 .
  57. ^ German Atomic Forum e. V .: Annual Report 2008 - Time for Energy Responsibility . Berlin 2009, ISSN  1868-3630 . Page 32
  58. ↑ http://nachrichten.rp-online.de/regional/akw-betreiber-will-keine-steuern-zahlen-1.754779 , accessed April 28, 2011
  59. ↑ Hamm-Uentrop THTR: Who pays for the demolition? https://www.youtube.com/watch?v=OqS4uz79gb8
  60. ↑ State Parliament of North Rhine-Westphalia, 14th electoral period, submission 14/2173, October 17, 2008
  61. ↑ 50 year cooldown. In: sueddeutsche.de. April 18, 2011, accessed March 16, 2018 .
  62. ↑ http://en.uatom.org/posts/8
  63. ^ Nuclear Power Plant Decommissioning at Fort St. Vrain. (PDF) (No longer available online.) Westinghouse Electric Company , February 2011, archived from the original on January 16, 2016 ; accessed on August 10, 2019 .
  64. ↑ http://www.wsw-online.de/fileadmin/Unternehmen/Geschaeftsberichte/WSW_GB_2012.pdf
  65. ↑ https://www.wa.de/nordrhein-westfalen/thtr-uentrop-laut-einer-studie-einer-groessten-bau-flops-vergangenen-jahre-5037527.html
  66. ↑ a b Green nuclear power plants . In: Die Welt , November 15, 2008.
  67. ^ Reiner Kümmel: The Second Law of Economics: Energy, Entropy, and the Origins of Wealth. Springer, Berlin 2011, ISBN 978-1-4419-9364-9 . P. 80f.
  68. ↑ Klaus Traube: Do we have to switch? Rowohlt 1978. Subchapter p. 196: The success of light water reactors; Subchapter p. 206: The perfect chaos: The high temperature reactor
  69. ^ Shareholder of the GWH
  70. ↑ http://www.derwesten.de/nachrichten/element-aus-atomkraftwerk-bei-ebay-zu-ersteigern-id4280119.html
  71. ↑ http://www.wa.de/nachrichten/hamm/stadt-hamm/ominoese-kuegelchen-allen-probe-alten-kraftwerk-1778669.html
  72. ↑ [1]  ( page no longer available , search in web archives )@1@ 2Template: Toter Link / www.lia.nrw.de
  73. ↑ [2]  ( page no longer available , search in web archives )@1@ 2Template: Toter Link / www.lia.nrw.de
  74. ↑ http://www.reaktorpleite.de/thtr-rundbriefe-2012/432-thtr-rundbrief-nr-140-dezember-2012.html
  75. ↑ http://www.wa.de/nachrichten/kreis-soest/welver/gutachter-gabriel-kuegelchen-sind-radioaktiv-2666054.html
  76. ^ Rene Benden: Research on HT reactors before the end. May 14, 2014 http://www.aachener-nachrichten.de/lokales/region/forschung-an-ht-reaktoren-vor-dem-aus-1.826886
  77. ↑ http://www.ee.co.za/wp-content/uploads/legacy/Generation1a.pdf , accessed on April 27, 2011
  78. ↑ PBMR Chronology ( Memento November 12, 2013 in the Internet Archive ) accessed April 27, 2011
  79. ↑ http://www.issafrica.org/uploads/210.pdf , accessed April 27, 2011
  80. ↑ Green nuclear power plants, Hermann Josef Werhahn in an interview 2008 https://www.welt.de/wissenschaft/article2725609/Gruene-Atomkraftwerke.html , accessed April 24, 2011
  81. ↑ South Africa is building the 100 percent safe pebble bed reactor, http://www.solidaritaet.com/fusion/2006/1/fus0601-suedafrika.pdf , accessed April 24, 2011.
  82. ↑ http://www.tagesspiegel.de/zeitung/ein-haufen-energie/725170.html , accessed on April 26, 2011
  83. ↑ Speech by Minister Ms. Thoben ( Memento from January 18, 2012 in the Internet Archive ), accessed January 16, 2016
  84. ↑ Sigurd Schulien: The question of energy is a question of survival https://web.archive.org/web/20130118075552/http://www.terra-kurier.de/Energiefrage.htm
  85. ↑ How one got Germany to give up its domestic energy base. Cape. 3: The HTR for coal gasification. Hut letters October / November 2005
  86. ↑ U.Cleve, The technology of high temperature reactors, atomwirtschaft Heft 12 (2009), see http://www.buerger-fuer-technik.de/body_technik_der_hoch Temperaturreak1.html , accessed January 16, 2016
  87. ^ Film on Youtube
  88. ↑ The technology of the THTR 300 in numbers, publisher: Hoch Temperatur-Kernkraftwerk GmbH, Hamm, 1989
  89. ↑ Power Reactor Information System of the IAEA : "Germany, Federal Republic of: Nuclear Power Reactors" (English)
  90. ↑ Martin Volkmer: Nuclear energy basic knowledge . KernEnergie Information Circle, Berlin June 2007, ISBN 3-926956-44-5 . Page 49
  91. ↑ Brochure high temperature reactors BBC / HRB publication no. D HRB 1033 87 D, page 6