Office for Nuclear Regulation

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System Based Inspection, SBI 04 - Auxiliary Cooling (including Pressure Vessel Cooling Water System)

Executive summary

Purpose of intervention

The principle purpose of this intervention was to undertake a system based inspection of the auxiliary cooling system. This intervention was undertaken in line with the planned inspection programme contained in the Heysham 1 Integrated Intervention Strategy (IIS).

Interventions Carried Out by ONR

This intervention involved undertaking a safety case system based inspection of the auxiliary cooling system that includes: Pressure Vessel Cooling Water (PVCW), Low Pressure Back Up Cooling (LPBUC), Reactor Ancillary Cooling Water (RACW), Turbine Hall Ancillary Cooling Water (THACW) and Tertiary Pressure Vessel Cooling Water (TPVCW).

Through examination of this system we performed compliance inspections against LC 10: Training; LC 23: Operating rules; LC 24: Operating instructions; LC 27: Safety mechanisms, devices and circuits; and LC28: Examination, inspection, maintenance and testing. Our inspections were based on sampling the implementation of the arrangements in place against each licence condition. I held pre- and post- inspection meetings with Heysham 1 management where the inspection agenda was discussed and the outcome of the inspection was communicated.

LC 34 (Leakage and Escape of Radioactive Material and Radioactive Waste) was not applicable to the chosen structures and therefore it was not considered during the inspection.

Explanation of Judgement if Safety System Not Judged to be Adequate

This system based inspection judged that the arrangements and their implementation, associated with auxiliary cooling system, met the requirements of the safety case and are adequate.

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

From an LC10 perspective, the overview of the safety case by those involved from Nuclear Generation Limited (NGL) demonstrated that they had adequate knowledge and experience in the areas of the safety case as well as the operating rules and instructions in place for the PVCW, LPBUC, RACW, THACW and TPVCW systems inspected.

The inspection of staff training records and profiles were in accordance with the role requirements. Therefore, I consider the LC10 element of this inspection to be adequate, warranting an associated Integrated Intervention Strategy (IIS) rating of 3.

From an LC23 perspective, based on the evidence sampled during this inspection, the implementation of the technical specifications, commentaries, and schedules has been demonstrated to be consistent with the claims and arguments presented within the safety case for the PVCW, LPBUC, TPVCW, RACW, THACW systems inspected. I consider the LC23 element of this inspection to be adequate, warranting an associated IIS rating of 3.

From an LC24 perspective, based on the evidence sampled during this inspection, I was content that the provisions in place as required by the PVCW, LPBUC, TPVCW, RACW, THACW safety cases were adequately implemented at Heysham 1. The operating rules under LC23 have been implemented through station and plant operating instructions, which was confirmed by sampling documents and records during the inspection. I consider the LC24 element of this inspection to be adequate, warranting an associated IIS rating of 3.

From an LC27 perspective, I have considered the LPBUC and the TPVCW systems. The duty holder was able to demonstrate an adequate level of compliance against LC 27. I consider that the LC27 element of this inspection to be adequate, warranting an associated IIS rating of 3.

Examination, inspection, maintenance and testing under LC28 involved sampling a number of maintenance tasks including completed records and check sheets as well as consideration of asset condition as part of the plant inspection. The inspection highlighted that Trimpell Tank 11, RACW and THACW tanks are not routinely inspected. The inspection confirmed that the trenched LPBUCS pipework has been inspected as part of the Pipework Inspection Programme and the buried pipework inspection approach is under review across the whole fleet. The PVCW leak management is judge to be adequate. Minor shortfalls were observed during the site inspection, however, I am content that the Station will be capturing the observations within their own arrangements. I consider the LC28 compliance of this inspection to be adequate, warranting an associated IIS rating of 3.

The licence conditions were inspected against ONR's published guidance requirements (as described in our technical inspection guides).

Conclusion of Intervention

After consideration of all the evidence witnessed during the sampling inspections undertaken against LCs 10, 23, 24, 27 and 28, I consider that the arrangements and their implementation, associated with auxiliary cooling system, meet the requirements of the safety case and are deemed adequate.

There are no findings from this inspection that could significantly undermine nuclear safety and no change to the planned interventions and inspections of Heysham 1.