Office for Nuclear Regulation

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System Based Inspection of the Reactor Post Trip Logic System and Oxygen Injection readiness review

Executive summary

Purpose of Intervention

The primary focus of this intervention was a planned system based inspection (SBI) of the EDF Energy Nuclear Generation Ltd (EDF NGL) Heysham 1 (HY1) power station reactor post trip logic (RPTL) system, which was undertaken as part of the HY1 integrated intervention strategy (IIS) plan.

Interventions Carried Out by ONR

The nominated Office for Nuclear Regulation (ONR) HY1 site inspector, an ONR control and instrumentation (C&I) specialist inspector and two ONR electrical specialist inspectors undertook a SBI of the HY1 RPTL system in order to judge whether it was able to fulfil its safety duties (safety functional requirements) in line with the safety case.

The RPTL system automatically starts-up / shuts-down essential plant in a defined sequence following a reactor trip in order to control post-trip temperature transients and ensure adequate decay heat removal.

Through sampling of associated operating and maintenance documentation, a plant walkdown and discussions with relevant HY1 staff we examined the performance of the RPTL system against the following Licence Conditions (LCs), which are applicable provisions of the Energy Act 2013:

It should be noted that LC 34 (leakage and escape of radioactive material and radioactive waste) was not considered during this inspection, as the RPTL system does not contain radioactive material.

The intervention was performed in line with ONR's guidance requirements (as described in our technical inspection guides) in the areas inspected.

Two International Atomic Energy Agency (IAEA) Integrated Regulatory Review Service (IRRS) UK mission inspectors also attended the first day of the SBI in an observatory capacity only.

During the two days of the SBI, the C&I specialist inspector also held a number of ad hoc discussions with EDF NGL personnel regarding the status of HY1 oxygen injection system commissioning activities.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable.

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

The key findings of our SBI of the RPTL system are:

Conclusion of Intervention

From the evidence sampled during this SBI against LCs 10, 23, 24, 27 and 28, we judged that the RPTL system was able to fulfil its safety duties (safety functional requirements) in line with the safety case.

There are no findings from this intervention that could significantly undermine nuclear safety at HY1. At present, no additional regulatory action is needed over and above the planned interventions at HY1, as set out in the HY1 IIS, which will continue as planned.