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Nuclear Safeguards Education Portal

Unattended Spent Fuel Monitor (UFSM)

The unattended fuel flow monitor (UFFM) and unattended spent fuel monitor (UFSM) monitor the movement of fresh fuel assemblies to the reactor (for those reactors utilizing MOX - mixed oxide fuel that contains plutonium - such as breeder reactors and LWRs on a MOX cycle), spent fuel assemblies from the reactor to the fuel storage pond, and spent fuel assemblies out of the storage pond.

A typical transfer sequence involving several monitor units could include a fresh fuel assembly being brought to the reactor core and a spent fuel assembly being retrieved and brought to the storage pond. The combination of neutron and γ ray signatures at the successive units characterizes the transferred material as either fresh fuel, spent fuel or other material (e.g. neutron irradiated blanket material at a breeder reactor facility). Surveillance cameras normally complement a UFFM over the fuel transfer route.


(Source: IAEA Safeguards Techniques and Equipment)