Office for Nuclear Regulation

System Based Inspection of Thorp Receipt and Storage

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 intervention was to undertake a System Based Inspection (SBI) of B560 for the Thermal Oxide Reprocessing Plant (Thorp) to confirm the adequacy of the implementation of the safety case. Inspection of evidence to support the claims made in the safety case and to ascertain compliance against Licence Conditions 10, 23, 24, 27, 28 and 34.  The inspection sampled the fuel handling equipment and associated safety measures.

Interventions Carried Out by ONR

Between 5 – 6 February 2019, ONR carried out a planned 2-day inspection of the Thorp receipt and storage facility 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, 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 10, 23, 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 LCs 10, 23, 27, 28 and 34.

For LC24 (Operating Instructions), I judged that there is a significant shortfall against relevant good practice with regard to the licensee’s use of written instructions. It is not normal practice in B560 is for the operator to have a copy of the Continuous Use Quality Plan to hand. The approach is not compliant with SL’s corporate arrangements for use of written procedures and has the potential to create an error trap since it relies upon the memory of the operator to complete certain tasks. I was content that there was not an immediate safety issue as the operator questioned and two facility DAPs had an adequate knowledge of the limits and conditions and hold point steps. OFSG have provided an adequate short-term solution to the finding ahead of devising a long-term solution.  A candidate level 3 regulatory issue has been raised to track progress by the licensee to address this shortfall.

Conclusion of Intervention

From the evidence sampled during the inspection, I judge that Thorp has adequately implemented the relevant claims in the safety case and that the formal arrangements for LCs 10, 23, 27, 28 and 34 are being adequately implemented. Regarding LC 24, a Level 3 candidate Regulatory Issue has been raised which the THORP and the OFSG Site Inspector will use to track actions to address the identified shortfall. I have also raised a level 4 Regulatory Issue in relation to other minor shortfalls observed during the inspection.

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