Office for Nuclear Regulation

Planned System Based Inspection (SBI)

Executive summary

Purpose of Intervention

In accordance with the Office for Nuclear Regulation’s (ONR’s) Sellafield Strategy, each year ONR performs a series of planned system based inspections (SBIs) targeted on key safety significant systems. The purpose of this particular inspection was for ONR to determine the adequacy of implementation of Sellafield Ltd.’s (SL’s) safety case claims for two fuel storage ponds operated by the Oxide Fuel Storage Group (OFSG) North i.e. a Light Water Reactor (LWR) and an Advanced Gas Cooled Reactor (AGR) pond. The inspection sampled the storage ponds and the associated safety measures.

Interventions Carried Out by ONR

Between 5 – 7 June 2018, ONR carried out a planned 3-day inspection of the OFSG storage ponds utilising specialists from the following technical disciplines:

In order to determine the adequacy of the licensee’s implementation of the safety case   claims in respect of these systems, i.e. the OFSG storage ponds, ONR examined evidence to verify the adequacy of the implementation of SL’s arrangements for six pre-defined licence conditions (LCs), as listed below. These LCs have been selected in view of their importance to nuclear safety and are defined within ONR’s formal process for SBIs.

The inspection involved reviewing the applicable claims in the safety cases and then sampling suitable evidence to determine compliance against the selected LCs on the plant. This was achieved through a combination of document reviews, plant inspections and discussions with operators and maintenance staff.

ONR assessed compliance in Thorp against the following LCs by using the applicable ONR inspection guidance documents:

Explanation of Judgement if Safety System Not Judged to be Adequate

This safety system is judged to be adequate.

Key Findings, Inspector's Opinions and Reasons for Judgements Made

Whilst some minor opportunities for improvements were identified, I found LCs 23, 24, 27, 28 and 34 to be adequately implemented in relation to the systems inspected. Consequently, it is my opinion that for this system based inspection a rating of GREEN (no formal action) is appropriate for LCs23, 24, 27, 28 and 34.

For LC10 (Training), I judged that there is a significant shortfall against relevant good practice with regard to OFSG’s implementation of LC 10 arrangements. This relates to OFSG not being able to provide adequate records to demonstrate that all personnel who are required to compile and check Authorisation for Fuel Transfer (AFT) documents (for conducting fuel moves within SL) had received a specific training package, which is necessary for compliance with local OFSG arrangements. OFSG was also unable to provide records to demonstrate that personnel had been formally nominated to perform such roles, which is a further requirement of these arrangements. Consequently, it is my opinion that for this system based inspection a rating of AMBER (seek improvement) is appropriate for LC 10. Nevertheless, based on the evidence sampled I judged that the plant operators and maintainers had been adequately trained. Since the inspection, OFSG subsequently provided assurances as to how it has verified that the personnel who compile and check AFT documents are Suitable Qualified and Experienced (SQEP).

I have also raised a further four level 4 Regulatory Issues in relation to other minor shortfalls observed during the inspection.   

Conclusion of Intervention

From the evidence sampled during the inspection, I judge that OFSG has adequately implemented the relevant claims in the safety case and that the formal arrangements for LCs 23, 24, 27, 28 and 34 are being adequately implemented. Regarding LC 10, a level 3 candidate Regulatory Issue has been raised which the Thermal Oxide Reprocessing Plant (Thorp) and OFSG Site Inspector will use to track OFSG’s actions to address the identified shortfall.

Overall, I judge that the safety system is adequate and fulfils the requirements of the safety case.