Analysis of severe accident energetics in metallic-fueled, liquid metal cooled reactors
The energetics potential of severe accidents is investigated for metallic-fueled reactors using the SAS4A accident analysis code. The accident initiators considered are transient overpower and loss of flow, each with failure to scram. Extensive analysis of the response of metallic-fueled reactors to double fault initiators such as loss of flow, loss of heat sink, or transient overpower with failure to scram shows that the reactors passively adjust their power to match the available heat rejection capability without boiling coolant or melting fuel. The analysis considered here assumes some extremely unlikely additional contribution to the accident such as an essentially unlimited reactivity insertion in the case of the transient-overpower sequence, or failure of the flow-coastdown device in the case of a loss-of-flow sequence. When the reactivity insertion rates are high enough, either due to control rod motion or due to coolant voiding, the low melting point of metallic fuel allows fuel to disperse within intact cladding prior to cladding failure. Negative reactivity feedback from this in-pin fuel motion counters the positive reactivity insertion and prevents a rapid and large release of energy. The SAS4A analysis shows that extensive core melting and disruption can be expected, but that the energy release will not be large enough to threaten rupture of the reactor vessel. Metallic fuel acts as an additional safety device which acts to counter large or rapid reactivity insertions either from inadvertent control rod motion or coolant boiling and voiding.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 10200225
- Report Number(s):
- ANL-IFR-235; 154296
- Country of Publication:
- United States
- Language:
- English
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