I undertook a system inspection of Berkeley's Shielded Facilities' caves' ventilation system. The information gained will be of value for future work to remove the intermediate level waste (ILW) stored in the caves and placing it in a passively safe form into self-shielding containers.
I attended Berkeley's Site Stakeholder Group meeting.
Berkeley provided me with a series of documents that together comprised the safety case for the caves' ventilation system. I inspected the outside of the caves and their ventilation system including filter housings and trunking. Berkeley explained how the quiescent safety case had been modified to cover the setting to work of equipment in the caves. I sampled the training requirements, operating instructions and maintenance requirements placed on the ventilation system arising from the safety case.
I judged the caves' ventilation system to be adequate for the current operations while there were no ILW movements taking place, but observed that the safety case would need modification, and as necessary, the ventilation system before treating the ILW into a passively safe form.
I judged that Berkeley was working in a way that should minimise the risks to safety from the ILW currently stored in the caves. I noted that, in order to increase the air flow through the caves during the maintenance activities on the cave machinery, parts of the ventilation system were working at their design limits. I advised Berkeley that this may mean that the ventilation system might need modification before the ILW could be processed into a passively safe form for long term storage.
Berkeley was reconsidering whether to use Ductile Cast Iron Containers (DCICs) or drums placed in concrete boxes for the long term storage of the "cave ILW" in the Interim Storage facility. I was told that from a safety perspective the DCICs seemed to be the preferred option, because there was no uncertainty in how the work would be achieved as this option had been demonstrated during work on emptying Vault 2. Berkeley staff noted that the use of drums for storage in concrete boxes appeared to require a number of new processes to be commissioned. Through my discussions I gained confidence that Berkeley staff understood the safety issues arising from their work in the caves.
Berkeley demonstrated that it was taking steps to minimise the risks to the public, workers and the environment in its preparations for emptying the Shielded Facilities' caves of the ILW currently stored in them.