The reactor bankruptcy - THTR 300 The THTR Circular
Studies on THTR and much more. The THTR breakdown list
The HTR research The THTR incident in the 'Spiegel'

Unfortunately, the list of faults at the THTR does not end with the shutdown of the reactor in 1989 ...


Bankruptcies, bad luck and THTR breakdown series

In the issues 3/87 and 3/88 of the quarterly magazine "Kultur und Umweltinformation", which was published by the Landesverband Westfalen "Die Naturfreunde" in an edition of approx. Created in 1.000. Mostly on the basis of the THTR weekly reports, which the operator "Vereinigte Elektrizitätswerke Westfalen" (VEW) had to publish as paid advertisements in the "Westfälischer Anzeiger" (WA), thus complying with the great pressure for more detailed information.

"The Friends of Nature" were close to the SPD at the time. With this publication and the total of 36 pages of critical reporting on NRW's nuclear policy in 1987 and 1988, I, as a member of the Friends of Nature, hoped to be able to influence the largely nuclear-friendly policy of the SPD state government a little. The articles not only received friendly attention. - The THTR accident history, which was continued up to 1994, clearly shows that in the years of operation of this reactor hardly a month remained without complications. Even after its shutdown in 1989, the incidents did not stop.

Horst Blume


Beginning of the list - 07.09.1985

Failure of humidity sensor. Cause: The measuring electrodes of the humidity sensors are covered with graphite dust.


Crack in the condensate line. Cause: vibration cracking


False start of an emergency diesel generator. Cause: not found.


Shutdown of the reactor by triggering "rapid procedure". Cause: electromagnetic interference pulses


Loss of power on an emergency diesel generator. Cause: not found.


Failure of a temperature measuring point. Cause: Power interruption in the measuring sensor.


Reactor shutdown with NK 45. * Cause: Incorrect valve setpoint setting.


* The NK 45 emergency cooling procedure

is an automatically running emergency cooling process.

In such emergency cooling processes, the components of the reactor are subjected to severe thermal stress due to temperature change processes. The number of these emergency cooling procedures was therefore limited to a maximum of 45.

The THTR 10 had to cope with these emergency cooling processes within 12.11.1985 months (from November 02.09.1986th, 11 to September XNUMXnd, XNUMX).



Reactor shutdown with NK 45. Cause: A transformer switched off automatically


Incomplete retraction of 7 core rods. Cause: increased counter-forces on rods due to a lack of ammonia feed, low core temperature, unthrottled coolant throughput.


Reactor shutdown with NK 45. Cause: incorrect shutdown of an electrical rail.


Reactor shutdown with NK 45. Cause: Reduction of the feed water volume by hand and response to a protection criterion.


Reactor shutdown with NK 45. Cause: Loss of protection when switching from internal supply to the public grid.


Failure of the TL 11 ventilation system. Cause: Fan: Bearing damage, malfunction in the trigger mechanism.


Reactor shutdown with NK 45. Cause: Bad signal.


Reactor shutdown with NK 45. Cause: defective electronic contact.


Reactor shutdown with NK 45. Cause: Leakage with 2 throttle valves.


Reactor shutdown with NK 45. Cause: Underfeed of the steam generator.


Reactor shutdown with NK 45. Cause: Voltage drops in the fan supply during an experiment


Reactor shutdown with NK 45. Cause: Voltage drop in the fan supply during an attempt.


04.05.1986/XNUMX/XNUMX: Fault in the ball loading system of the THTR

See: In the 'History' - The incident -
and the 'reportable event' in 'INES - List of Incidents' -

As well as the contribution 'Sparkling eyes' in the mirror



Triggering of a post-cooling procedure. Cause: Malfunction of an electronic component.


Reactor shutdown with NK 45. Cause: Fault while testing a switchgear.


The THTR has reached its full capacity for the first time. The system is then switched off for several weeks to be checked.


The THTR has not been in operation since yesterday. Maintenance and optimization work is taking place, in which 500 specialists are involved.


Only two days after a seven-week general inspection, the reactor had to be shut down again. There was a jam in the trigger tube. A cooling fan has failed due to an error in the electronic control. The temperature rose so quickly for a short time that the reactor switched itself off.


At 40 percent power, "final improvements were made to controls and regulation".


The VEW announces that when the THTR is started up and shut down, the highly toxic anti-corrosion agent hydrazine gets into the lip. The concentration is reportedly 0,1 milligrams per liter.


Residents in the immediate vicinity of the THTR complain again about low-lying jet fighters of the Bundeswehr. For eight years there have been up to 80 approaches per day in sunny weather.


The THTR has been switched off since March 2nd.


Collection cans for no longer usable fuel assemblies were replaced.


Shutdown of the reactor. Checks on the pipes of the steam circuit. All welding wire areas on the small lines had to be checked and in some cases replaced.


The VEW confirm an increased ball breakage rate. Instead of 800 balls had to in the last year and a half 8.000 fuel assemblies be weeded out.


A bearing damage on one of the four auxiliary cooling water pumps has been fixed.


Automatic shutdown of the reactor. The cooling water supply to the turbines was interrupted because a fault in the control of the turbine steam circuit had to be rectified. A power supply unit failed during the standstill.


Turbine switched off due to a response value set too low in the generator protection device, two electronic cards defective. Power generation was interrupted for two hours and the reactor remained in operation.


Shutdown due to "annual revision" until the end of January 1988.


Automatic shutdown. The reason given by VEW was the incorrect response of the fill level monitoring of the feed water tank in the conventional part of the system.

November 09-15.11.1987, XNUMX:

Under the heading "Findings", the operators ticked off an incident in which inadmissibly high levels of the radioactive substance tritium reached the Lippe in the past week (WA November 21, 11).


The THTR has resumed operations after the annual revision that began in October 1987.


The THTR was switched off in order to eliminate the sluggishness of some control valves in the water-steam circuit mentioned in the last weekly report.


During control work on the sewer, through which checked, weakly contaminated operating wastewater from the THTR 300 is discharged directly to the Lippe, part of the wastewater was briefly channeled into the Lippe via the rainwater drainage path of the power plant.


Shutdown of the THTR for four weeks to carry out "various" work. I.a. the containers for damaged operating elements are replaced and inspections are carried out on the ball conveyor. The break is also used to carry out recurring tests on the system.


A malfunction was found during a recurring test on a control valve of the water-steam circuit. The defective controller was replaced immediately.

November 30.05-02.06.1988, XNUMX:

During a recurring test, a cooling water valve in the gas cleaning system did not close according to the program.


The cooling water supply to the turbine was interrupted due to a defective electronic card in the control of the dry cooling tower. As a result, an automatic shutdown of the reactor was triggered.


During a review of the ventilation systems for the reactor hall, mechanical stiffness on a ventilation flap was found and rectified.


To replace a leaky flange seal in the water-steam circuit, the power plant was temporarily disconnected from the network.

November 18-23.07.1988, XNUMX:

Defective electronic cards on the control of two relief valves in the water-steam circuit were replaced. These valves are used to regulate the pressure reduction during various shutdown procedures.


After the replacement of a container for operating elements that were no longer usable had been completed, the THTR went back on line after a one-week shutdown pause.


When the reactor continued to operate, the generator was disconnected from the network for approx. 5 hours to eliminate a small steam leak in the main turbine.



“Material fatigue in a heating channel prevents the Uentroper THTR from going back online as planned in mid-November. During the routine inspection of a hot gas duct with which hot gases are led from the reactor to the steam generator, five damaged fastening elements were discovered. "(From: WA dated November 1, 11)



Failure of the quick-closing function of the blower shut-off regulator of a cooling gas blower.


Insufficient cooling capacity of the refrigerant condensers for the refrigeration compressors of one of the two emergency and post-cooling systems.


Incorrect locking of an emergency cooling steam generator component protection criterion.


Increased noble gas and tritium concentration in a room group of the control area.


Failure of the fan of the negative pressure maintenance system due to a defective limit value card.


Failure of a fan in the rooms of the gas cleaning and charging system.


Failure to switch an infeed switch of the DC voltage supply when the test is repeated.


Failure to switch a supply air valve in the event of a recurring test.


Failure of the control function of a relief valve for the hot reheating (HZUE).


In September 1989 the THTR was shut down.

But what a real accident reactor is
of course, he continues to bother:


Crash of an empty fuel can.


Bearing damage on an exhaust fan.


A rotary switch on the control panel of the crane in the operating element store is no longer adequately fastened.


Malfunction of an air recoil valve of the air circulation system for the rooms of the charging system.


Failure of an exhaust fan for the fuel element store.


Failure of the high voltage detector on the iodine monitor of the chimney exhaust air monitoring.


Failure of the iodine signal computer and the high voltage detector on the iodine monitor.


Demolition of the drive spindle on a supply air control flap.


Failure of the noble gas and tritium activity measuring device for the nacelle exhaust air.


Failure of both conveyor units of the chimney exhaust air monitoring.


Failure of the tritium measuring channel in the activity monitoring of the nacelle exhaust air.


Faults in the V-belt drive of a supply air fan of the nuclear ventilation system.


Release of an exhaust fan for the reactor hall.


December 1992 to February 1993:

"Tritium accident":

Even after its shutdown, the THTR suffered a long-term incident with a release of radioactivity. The radiation protection report of the NRW state government reported on February 8, 1993: “The residual water found in a room of the gas cleaning system (water height approx Tritium activity concentration of 1,5 million becquerels per liter. The suspicion that this could result in a release of tritium from areas of the THTR plant into the soil or groundwater (groundwater) arose on December 18, 1992 on the basis of a water sample ... ”. The “basement” of the THTR, which is about four meters deep, has not been used for four years. According to the investigation report by the NRW Ministry of Economics, the groundwater rose to a height of 40 centimeters, as the solid deposits on the walls would show. A total of 7.000 liters of contaminated water have disappeared.


22.10/07.12.1993 until XNUMX:

Defective coupling of an exhaust fan.

22.10/07.12.1993 until XNUMX:

Too low a flow rate of a chimney exhaust air sampling fan.


A functional test of the fire dampers revealed that they did not close as required.

July 22.07nd to August 19.08.1994th, XNUMX:

During the period mentioned, an exhaust fan (replacement unit not in operation) was temporarily unavailable due to repair work on the associated power supply.


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