Office for Nuclear Regulation

System Based Inspection of THORP Receipt and Storage

Executive summary

In accordance with the Office for Nuclear Regulation’s (ONR’s) Sellafield Limited (SL) 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 an SBI of the Thermal Oxide Reprocessing Plant (THORP) Receipt and Storage (TR&S) Facility 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. 

Interventions Carried Out by ONR

I, the Site Inspector for THORP and Oxide Fuel Storage Group (OFSG) carried out a planned 2 day inspection of the TR&S Facility on the 12 and 13 November 2019, 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 at Paragraph 5. 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 evidence to determine compliance against the selected LCs at the facility. This was achieved through a combination of document reviews, plant inspections and discussions with operators, training and maintenance staff.

ONR assessed compliance in TR&S 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

In relation to LC28, I identified two minor shortfalls; the pond cooling water system pumps (supporting the primary means of cooling the pond) are currently unavailable; the shortfall being in relation to SL being unable to demonstrate the due process followed to take these pumps out of service. However, I am satisfied that due to the pond inventory and alternative cooling arrangements, the unavailability of the pond cooling water system pumps is not a safety concern at this time. I also identified a minor shortfall identified in relation to the Civil Engineering System Health Report (SHR) for TR&S where it was judged that the summary SHR Red/Amber/Green rating did not reflect the plant status. I intend to manage these shortfalls by raising Level 4 regulatory issues.

Notwithstanding these minor shortfalls, I found LCs 10, 23, 24, 27, 28 and 34 to be adequately implemented in TR&S 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, 24, 27, 28 and 34.

My findings from the intervention were presented to and accepted by the Head of Operations on completion of the inspection.

Conclusion of Intervention

From the evidence sampled during the inspection, I judge that TR&S has adequately implemented the relevant claims in the safety case and that the formal arrangements for LCs 10, 23, 24, 27, 28 and 34 are being adequately implemented. Two minor shortfalls were identified which I plan to manage by way of raising Level 4 Regulatory Issues.

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