Office for Nuclear Regulation

System Based Inspection - SBI 18 -Turbine Protection Systems

Executive summary

Purpose of Intervention

This intervention, conducted at the EDF Nuclear Generation Limited’s Hinkley Point B Power Station and was undertaken as part of the 2019/2020 intervention strategy.

The purpose of this intervention was to undertake a system based inspection of the steam turbine and emergency gas turbine overspeed protection systems at EDF Nuclear Generation Limited’s Hinkley Point B Power Station. This was conducted in accordance with the planned inspection programme.

Interventions Carried Out by ONR

The Office for Nuclear Regulation (ONR) site inspector for Hinkley Point B Power Station and ONR specialist inspectors in mechanical and electrical engineering conducted a planned system based inspection of the turbine protection systems. Implementation of EDF’s safety case for the protection systems was sampled via compliance inspections against a number of Licence Conditions.

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

Through examination of the systems and their associated sub-systems, we performed compliance inspections against Licence Conditions LC10 (Training), LC23 (Operating rules), LC24 (Operating instructions), LC27 (Safety mechanisms, devices and circuits), LC28 (Examination, inspection, maintenance and testing) and LC34 (Leakage and escape of radioactive material and radioactive waste).  The inspections were based on sampling the implementation of the arrangements in place against each licence condition.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not Applicable.

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

Based on the areas sampled during the system based inspection it was found that Hinkley point B met its legal requirements which ensure that the turbine protection systems meet the requirements of the safety case.

The inspection of the turbine protection systems was via examination of work instruction documentation and records, discussion with key plant personnel and inspection of relevant plant areas.

The outcome from the system based inspection of the turbine protection systems was that the arrangements and implementation for LC10, 23, 24, 27 and 28 were judged to meet legal requirements LC 34 was not applicable to the systems inspected, therefore no rating was appropriate.

Conclusion of Intervention

After considering all the sampled evidence examined against LCs 10, 23, 24, 27 and 28 (LC 34 was not applicable), we concluded that a ‘Green’ rating was appropriate.

There are no findings from this inspection that could significantly undermine nuclear safety associated with the equipment sampled during this inspection although three minor regulatory issues were raised to provide oversight of the licensees response to observations made during the inspection.