Criticality safety study of the MSRE auxiliary charcoal bed
The Molten Salt Reactor Experiment (MSRE) was operated from June 1965 to December 1969. The objective of the experiment was to investigate the practicality of developing a power reactor consisting of a graphite lattice with circulating molten uranium salt as fuel for application in central power stations. When the experiment was terminated in 1969, approximately 4710 kg of salt containing approximately 36.3 kg of uranium, 675 g of plutonium, and various fission products were transferred to two fuel drain tanks (FDTs). The almost 30.5 kg of Uranium 233 in the salt is the primary fissile constituent, but about 0.93 kg of Uranium 235 is also present. In April 1994, a gas sample from the MSRE off-gas system (OGS) indicated that uranium had migrated from the FDTs into the OGS. Further investigation revealed a likely accumulation of approximately 2.6 kg of uranium in the auxiliary charcoal bed (ACB), which is located in the concrete-lined charcoal bed cell (CBC) below ground level outside the MSRE building. The nuclear criticality safety (NCS) situation was further complicated by the CBC being filled with water up to the overflow pipe, which completely submerged the ACB. Thus there was not only an increased risk of criticality because of water reflection in the ACB, but also because of potential moderation in the ACB in case of water inleakage. Leakage into the ACB would result in a direct path for water between the CBC and the OGS or FDTs, thus increasing the risk of criticality in these areas. When uranium was discovered in the ACB, a number of steps, detailed in this report, were immediately taken to try to understand and ameliorate the situation. After all the actions were completed, a validation of the results obtained for the ACB was performed.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 408664
- Report Number(s):
- ORNL/M-5450; ON: DE97050141
- Resource Relation:
- Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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