TY - RPRT
TI - Effective void fraction for a BWR assembly with boiling in the bypass region
AB - Average BWR assembly cross-sections for nominal conditions, namely for zero bypass void, can be utilised in the analysis of transient conditions with boiling in the bypass. A model is developed to yield an effective channel void for such conditions. The use of this void in conjunction with the `nominal conditions` cross section library approximately preserves the assembly K-infinity corresponding to the true channel and bypass voids. The effective void is an augmentation of the actual channel void. The augment is proportional to the bypass-to-channel volume ratio, to the bypass void, and to a weight W which is introduced to quantify the fact that a water molecule in the bypass has a different assembly criticality worth than one in the channel. The formula developed is superior to the practice of choosing W=1, namely a simple, non-weighted, transfer of water from channel to bypass. The use of this approximate effective channel void reproduces actual K-infinity values of assemblies to better than 5 mk, whereas the use of a simple model sometimes misspredicts the assembly K-infinity by 40 mK. The effective void model cannot handle cases in which both channel and bypass void value are high, simply because then the effective void {alpha}{sub ch}{sup eff} becomes meaningless. A method to treat the {alpha}{sup eff}>1 domain is developed by which corrections to cross sections are provided. Such corrections are synthesised as functions of the assembly parameters. (author) figs., tabs., refs.
AU - Galperin, A
AU - Segev, M [Ben-Gurion Univ. of the Negev, Beersheba (Israel)]
AU - Knoglinger, E [Paul Scherrer Inst. (PSI), Villigen (Switzerland)]
KW - 21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
KW - BWR TYPE REACTORS
KW - VOID FRACTION
KW - BYPASSES
KW - BOILING
KW - EIGENVALUES
KW - PRESERVATION
KW - CROSS SECTIONS
KW - DANCOFF CORRECTION
KW - FUEL ASSEMBLIES
KW - MATHEMATICAL MODELS
KW - THEORETICAL DATA
KW - TRANSIENTS
KW - 210100
KW - POWER REACTORS, NONBREEDING, LIGHT-WATER MODERATED, BOILING WATER COOLED
DO -
UR -
PB -
CY - Switzerland
PY - 1991
DA - 1991-09-01
LA - English
J2 -
C1 - Paul Scherrer Inst. (PSI), Villigen (Switzerland)
C2 -
ER -