Reactivity Worth of the Flooding of the ETRR-2 Second Shutdown System Chambers

The ETRR-2 research reactor has a second shutdown system consisting of four chambers surrounding the core chimney.These chambers are to be filled with Gadolinium solution in case of failure of the first shutdown system within a certain time period. The reactor core chimney together with second shutdown system four chambers lie inside the reactor main water pool.The possibility of the chambers to be flooded with water is considered to be one of the safety issues to be addressed. As the reactor core is very heterogeneous, the reactivity effects of each individual chamber are different. Also, the reactivity worth of these chambers depends on the core configuration.The present study aims to evaluate the reactivity worth of each individual chamber, the total worth of all the chambers and the maximum worth of any flooded chamber in case of the other chambers being filled with nitrogen. Certain conclusions are drawn regarding the safety of the ET-RR-2 reactor in case of the chambers being filled with water and the second shutdown system being on demand