LWR SPENT FUEL CASK REACTIVITY MEASUREMENT SYSTEM

As initial enrichment and bumup of fuel assemblies in nuclear power reactors increases, taking bumup credit is now proceeding in LWR spent fuel cask criticality safety design. This paper describes a reactivity measurement system based upon the ~ssive neutron measurement technique in ~et condition(PA-w system) developed to obtain a subcriticality value by making direct in-cask measurement of neutron flux. The PA-w system comprises four sub-systems; the main control software, the computer analysis software, the data base and the on-site work. Analytical simulations, assuming nine PWR type fuel assemblies in a cask with a square array and four neutron detectors installed around the fuel assemblies, have been run to determine the system performance. The results demonstrated that the PA-w system is feasible for measuring the bumup of each loaded fuel assembly and the k-eff accurately, and has sufficient CPU time for fuel loading work.