Low sodium void cores

Conference · Sun Jan 01 04:00:00 EST 1978

OSTI ID:6386135

Barthold, W P; Beitel, J C; Lam, P S.K.; Orechwa, Y; Su, S F; Turski, R B

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-31109-ENG-38
• OSTI ID: 6386135
• Report Number(s): CONF-781022-32
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
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ACCIDENTS
ALKALI METALS
BOILING
BREEDER REACTORS
DESIGN
ELEMENTS
EPITHERMAL REACTORS
EXCURSIONS
FAST REACTORS
FBR TYPE REACTORS
KINETICS
LIQUID METAL COOLED REACTORS
LMFBR TYPE REACTORS
METALS
PHASE TRANSFORMATIONS
REACTIVITY
REACTIVITY COEFFICIENTS
REACTIVITY INSERTIONS
REACTOR ACCIDENTS
REACTOR COMPONENTS
REACTOR CORES
REACTOR KINETICS
REACTORS
SODIUM
VOID COEFFICIENT