A hot water layer system (HWLS) is a novel system for reducing radioactivity
under research reactor containment. This system is particularly useful in
pool-type research reactors or other light water reactors with an open pool
surface. The main purpose of a HWLS is to provide more protection for
operators and reactor personnel against undesired doses due to the radio-
activity of the primary loop. This radioactivity originates mainly from the
induced radioactivity contained within the cooling water or probable minute
leaks of fuel elements. More importantly, the bothersome radioactivity is
progressively proportional to reactor power and, thus, the HWLS is a partial
solution for mitigating such problems when power upgrading is planned.
Following a series of tests and checks for different parameters, a HWLS has
been built and put into operation at the Tehran research reactor in 2009. It
underwent a series of comprehensive tests for a period of 6 months. Within
this time-frame, it was realized that the HWLS could provide a better
protection for reactor personnel against prevailing radiation under
containment. The system is especially suitable in cases of abnormality, e. g.
the spread of fission products due to fuel failure, because it prevents the
mixing of pollutants developed deep in the pool with the upper layer and thus
mitigates widespread leakage of radioactivity.
Design and installation of a hot water layer system at the Tehran research reactor
