Investigation of N Reactor Scram of September 30, 1970
- Douglas United Nuclear, Inc., Richland, WA (United States)
During the early phases of startup and power ascension activities on September 30, 1970, the Hanford N Reactor received an automatic shutdown (scram) signal from its safety system which monitors reactor coolant flow. The reactor neutron absorbing safety rod systems which should normally function to achieve reactor shutdown, failed to automatically respond to the scram signal by inserting all withdrawn rods into the reactor core. Failure of the neutron poison rods to automatically insert caused the automatic activation of the reactor safety backup shutdown system which achieved an immediate and safe shutdown of the reactor. Investigation of the September 30 scram of N Reactor was accomplished by investigating teams from both the Atomic Energy Commission and Douglas United Nuclear, Inc. This report covers the investigations, findings, and corrective actions taken by DUN as a result of the September 30 scram of N Reactor. Failure of the rod system to respond to the scram signal was conclusively determined to have been the result of a "sneak" circuit permitted by the shorting failure of multiple in-series diodes specifically designed into the rod control circuitry to prevent this type of sneak circuit. It was also clearly established that at no time was the reactor in or near an unsafe condition.
- Research Organization:
- Douglas United Nuclear, Inc., Richland, WA (United States)
- Sponsoring Organization:
- USDOE; US Atomic Energy Commission (AEC)
- DOE Contract Number:
- AC06-87RL10930
- OSTI ID:
- 2473283
- Report Number(s):
- DUN--7342
- Country of Publication:
- United States
- Language:
- English
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