Low sodium void cores
To avoid high energy releases in LMFBR TUC accidents which are accompanied by a failure to scram with a regular shutdown system, various devices have been proposed which would add negative reactivity to the core by either bringing poison material into the core or by creating negative reactivity feedbacks coming from the thermal expansion of the core. While inherent shutdown systems (ISSs) show promise for enhancing safety by adding poison to the reactor, the trigger mechanism and the geometry of the poison are critical design issues. But by postulating an ''unprotected'' accident, an emergency shutdown capability is denied by definition and the core has to rely solely on inherent safety features. Thermal expansion of core components can lead to the addition of negative reactivity to the core, however, dependng on the core restraint system this reactivity margin is usually small and does not prevent sodium boiling. Another approach to enhance the safety of the core is to modify the core design such that the removal of sodium from the core would add only a small amount of positive reactivity or even a negative reactivity. There exists no firm and quantified design goal for the maximum allowable sodium void reactivity. In a simplistic approach, a sodium void reactivity of approximately $2 or less would be desirable to compensate for roughly $1 in Doppler reactivity and $1 as the margin to the prompt-critical stage. But voiding incoherence and fuel motion patterns certainly affect this target value. At this stage of knowledge, it is also not clear if all fuel types would require the same reduction in sodium void reactivity to assure a benign transition phase leading to the termination of a TUC event. A discussion is presented of low sodium void core options which concentrates on the means of lowering sodium void reactivity in general and the oxide fuel form of the uranium--plutonium cycle in particular rather than the carbide, nitride and metal fuel forms.
- Research Organization:
- Argonne National Lab., IL (USA)
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 6386135
- Report Number(s):
- CONF-781022-32; TRN: 79-005121
- Resource Relation:
- Conference: Meeting on nuclear power reactor safety, Brussels, Belgium, 16 Oct 1978
- Country of Publication:
- United States
- Language:
- English
Similar Records
A simulation of I2S-LWR selected transients
PARAMETRIC REACTIVITY TRANSIENT ANALYSES FOR THE FFTF NUCLEAR PROOF TEST REACTOR
Related Subjects
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
EXCURSIONS
REACTIVITY INSERTIONS
LMFBR TYPE REACTORS
VOID COEFFICIENT
BOILING
DESIGN
REACTOR CORES
REACTOR KINETICS
SODIUM
ACCIDENTS
ALKALI METALS
BREEDER REACTORS
ELEMENTS
EPITHERMAL REACTORS
FAST REACTORS
FBR TYPE REACTORS
KINETICS
LIQUID METAL COOLED REACTORS
METALS
PHASE TRANSFORMATIONS
REACTIVITY
REACTIVITY COEFFICIENTS
REACTOR ACCIDENTS
REACTOR COMPONENTS
REACTORS
220900* - Nuclear Reactor Technology- Reactor Safety
210500 - Power Reactors
Breeding