Need for High Temperature Nuclear Data Library for LWR Design Computations

WIMS Library Update Project (WLUP) was taken up by the IAEA for updating the nuclear cross section data libraries. The 172 group WIMS libraries (45 fast, 47 resonance groups and 80 thermal) obtained under WLUP are used for reactor physics computations. These libraries have cross section data for 173 nuclides up to Cm. Resonance Integral Tabulation (RIT) data for 28 resonant nuclides are provided for a set of background cross sections and temperature values up to 1100 ◦K. In the reactor design computations, one requires simulation of reactor states with fuel temperatures reaching nearly up to melting point of 2800 ◦C for UO2 fuel. While using deterministic codes for high temperature calculation beyond 1100 ◦K, a linear extrapolation w.r.t. √ Tfuel is normally done. This is not quite satisfactory since even a small error in the slope near the highest temperature of 1100 ◦K data point could lead to significant error if the extrapolation is done up to very high temperatures. Recently an updated WIMS library has become available through WLUP follow up activities. This library contains RIT data for 48 resonant nuclides including several minor actinides and temperature extended up to 2500 ◦K and burnup chain has been extended up to Cf. Use of the new library has alleviated the problem of possible error in extrapolation. The new library called ‘HTEMPLIB’ has been tested for the design computations of VVER-1000 MWe reactor being constructed at Kudankulam, Tamilnadu, India. Two fuel types containing 4% and 3.6% enriched fuel were analyzed using the hexagonal lattice burnup code EXCEL. The results of the lattice analyses with the new WIMS library as well as the original WIMS library ‘JEFF31GX’, containing data up to a temperature of 1100 ◦K are presented in this paper.