Executive summary
Date(s) of inspection:
October 2024
Aim of inspection
The purpose of this intervention was to seek assurance on the adequacy of the implementation of the safety case at the LAEMG Medium Active Tank Farm (MATF).
Subject(s) of inspection
- LC10 - Training - Rating: GREEN
- LC23 - Operating rules - Rating: GREEN
- LC24 - Operating instructions - Rating: GREEN
- LC27 - Safety mechanisms, devices and circuits - Rating: GREEN
- LC28 - Examination, inspection, maintenance and testing - Rating: GREEN
- LC34 - Leakage and escape of radioactive material and radioactive waste - Rating: GREEN
- Overall Inspection Rating - Rating: AMBER
- PSSR - Rating: AMBER
Key findings, inspector's opinions and reasons for judgement made
I, the Site Inspector for Low Active Effluent Management Group, supported by specialist Civil Engineering, Mechanical Engineering, Human Factors, Structural Integrity and Fault Studies Inspectors, undertook a system based inspection (SBI) of the Medium Active Tank Farm (MATF) at the Sellafield Site.
MATF is a strategic asset for Sellafield Site operations, and will be required to operate until the cessation of Magnox Post Operational Clean Out (POCO) and to provide STP programme support. However, the sumps will remain operational until the building is demolished circa 2040. Normal operational receipts have stopped and both Magnox and THORP are looking to utilise storage capacity in MATF for their own POCO operations, although the exact timelines for these are still not fully underpinned. The current baseline shows MATF end of operations and POCO as of 2028. Removal of tank contents would follow and is expected to be completed by 2032.
MATF is comprised of two buildings, build of reinforced concrete walls, sectioned into compounds with the roofs constructed of pre-stressed, post-tensioned concrete beams with a concrete in-fill. All accessible valves are located on the roofs in either purpose-built brick or concrete bulges. There are 12 storage tanks in one of the buildings, 10 of which are open topped SS storage tanks with a nominal capacity of 1200 cubic metres each. There are two other lidded SS storage tanks with a nominal capacity of 600 cubic metres.
The MATF primarily stores solvents and other radioactive effluent in various states of treatment ahead of transfer elsewhere on the Sellafield Site.
I found that of the samples staff members, evidence was presented that showed that they were all adequately trained for operations or supervision for the MATF.
There is one formal operating rule at the MATF: keep the solvent tanks temperature below 30 degrees Celsius. I found that the evidence provided demonstrated that this rule is complied with adequately.
Safety mechanisms, devices and circuits had been identified in the safety case and were being maintained in accordance with the relevant written schemes.
I reviewed the draft system health reports (SHR) and found them to be useful for understanding the health and future expectations for the MATF.
I found a shortfall regarding MATF's implementation of Sellafield's arrangements for the pressure safety regulations (PSSR):
-
The high pressure steam pipelines were reportedly excluded from maintenance, appeared in disrepair and no justification was provided for this exclusion (PSSR Reg 12).
After the walkdown I sampled the most recent (from 2014) BV report on the thickness of the high pressure pipes on B213 and noted that the thickness of the pipe walls at twelve of thirteen locations were much less than the nominal thickness. As this report was 11 years old the degradation since that time led me to understand the the pipes may be now quite thin. As these are carrying high pressure steam around the facility, where operators regularly are located, I judged there to be a potential risk of serious personnel injury (ROSPI), discussed this with the facility operations manager who then decided to shut down and lock out the high pressure steam system until such time as LAEMG can justify a safe return to operation. I was content with this response from the facility as depressurisation and locking out the system removes the risk from a high pressure steam failure.
I rated this area Amber and have raised a Level 3 Regulatory Issue to track the dutyholder's work to return to compliance with the law.
While on plant I found housekeeping to be reasonable, although I recommended that the dutyholder improve cleaning and maintenance of the roof of the MATF.
Conclusion
I am of the opinion that LAEMG has adequately implemented the safety case for the MATF, however there were several shortfalls found associated with extent of condition of HP steam lines at B213, and implementation and understanding of the PSSRs. I have thus rated this inspection as Amber and have raised a Level 3 RI (RI-12433) to track the facility's work to bring it in line with the law (ONR-EDR-24-34). I will also be working with other ONR inspectors at a higher level to address Sellafield Ltd shortfalls associated with the PSSRs, using ONR-EDR-24-65.