A liquid injection based Second Shutdown System for a typical material testing research reactor.

Many research reactors are used all over the world. There is a higher probability of accidents in nuclear research reactors compared their wide applications in a broad spectrum of sciences and industries. Material Testing Reactor (MTR) type is one large species of nuclear research reactors. Safety criteria are of main concern issues in the entire nuclear research reactor lifetime to satisfy the defense in depth criteria. In this paper, the main focus is on Second Shutdown System (SSS) as an Engineered Safety Feature (ESF) considered to enhance safety which will transfer the reactor to a subcritical state at actuation of any command circuits when a specific parameters exceeds some pre-established set points. Tehran Research Reactor (TRR) is selected as an MTR case study and one SSS is designed and studied in detail using MCNPX 2.6.0 code with regard to its requirements. It turns out that this SSS improves the overall reactor safety, and has not considerable penalties on different capabilities and characteristics of the reactor such as neutronic characteristics, safety criteria, and performance applications. [ABSTRACT FROM AUTHOR]