Neutronic analysis of tank-in-pool type research reactors

The neutronic analysis of low power tank in pool type research reactors has been performed using standard computer codes WIMS-D/4 and CITATION. The data of existing HEU core of PARR-2 has been used for this purpose. Group constants for fuel, control rod and water and Be reflectors have been calculated by using WIMS-D/4. The core calculation have been performed by using the R-Z model of the CITATION code. Excess reactivity and space and energy dependent neutron fluxes for PARR-2 have been compared with the experimentally measured values quoted in literature. The excess reactivity for fresh clean core at cold condition was found to be 4.14 mk where as reported value is 4.0 mk. This slightly greater value of excess reactivity is because of neglecting the tie bolts and dummy aluminum rods in the core and fuel has been assumed at these places. The control rod worth was found to be 7.22 mk, which provides sufficient shut down margin of 3.08 mk. The addition of 1095 cm thick top Be reflector provides an excess reactivity of 18.16 mk in fresh clean and cold core while the measured value is 18.5 mk. (author)