Reactor system description and development status of ISIS

REACTOR SYSTEM DESCRIPTION AND DEVELOPMENT STATUS OF ISIS 7.6.1. Basic objectives and features 

The ISIS (Inherently Safe Immersed System) has been conceived and developed by ANSALDO in recent years beginning from 1987 as an innovative reactor with easily understandable inherent safety characteristics. 

It is an integrated PWR, completely immersed in a large pool of cold boronated on water which builds up on the density lock concept originally proposed by ABB ATOM for the PIUS plant and embodies revolutionary ideas for enhanced passive safety. The ISIS reactor components, on the other hand, are mainly based on proven technology derived from the ANSALDO experience in the field of both LWRs and LMFBRs. 

The engineered configuration provides defence, primarily by prevention, against accidents with severe core damage. 

The self-depressurization of the Primary System, the scrubbing effect of the pools and the absence of significant Reactor Containment pressurization under all accident conditions drastically reduce radioactive releases to the environment, 

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