In-pond condition monitoring using ROVs

Project

Long-term storage of spent nuclear fuel

Benefits

This project will provide improved condition monitoring of spent nuclear fuel in long-term storage, helping to ensure the integrity of the material.

Current Status

A modified ROV with in-pond monitoring station has been developed and built. Initial inactive testing is complete, and implementation within the TR&S pond is underway.

Delivery Partners

Jacobs

Contact Details

Mark Holmes

innovation.team@sellafieldsites.com

Spent nuclear fuel from the UK’s fleet of AGRs will be held in long-term storage at the THORP Receipt & Storage (TR&S) pond before eventual disposal in a future GDF. This will involve spent fuel pins being transferred to 63-can racks for long-term storage within the pond.

Condition monitoring is required to confirm the integrity of the spent fuel pin stainless steel cladding throughout this storage period and identify any racks that may need closer monitoring. However, an improved method for monitoring spent fuel pins within racks for indicators of cladding deterioration was required that has two key capabilities:

1. Remote operation to minimise operator dose uptake associated with sampling operations and allow targeted sampling of specific racks of interest.

2. In-pond monitoring system, removing the requirement of sending a radioactive sample to the laboratories for analysis and provide an almost immediate result in-situ.

Collaboration with Jacobs has led to the development of an ROV which can sample water within the racks and monitor this in-situ. An existing ROV has been modified to include an arm-mounted syringe which can perform sampling of the rack water. This will then transport the sample to an in-pond monitoring station which contains a gamma spectrometer and analyse it for key indicators of cladding deterioration.

This project has resulted in the production of an ROV rack sampler and in-pond monitoring system, developed for use in the TR&S pond. Now that inactive testing is complete, further work to implement the technology is currently underway.

By continuously improving the condition monitoring capability as technology develops, the return on investment is maximised ensuring the safe long-term storage of spent nuclear fuel.