Office for Nuclear Regulation

Dungeness B - System Based Inspection of the Gas Circulator System

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake a multi-disciplinary System Based Inspection (SBI) at EDF Nuclear Generation Limited’s (NGL’s) Dungeness B power station in line with the inspection programme contained in the 2019 - 2020 Site Inspection Plan. The inspection was undertaken by two Fault Studies Specialist Inspectors, a Mechanical Engineering Specialist Inspector, an Electrical Engineering Specialist Inspector, and the Nominated Site Inspector. This SBI concentrated on the Gas Circulators System. The aim of the inspection was to confirm that the Gas Circulators, with associated operating instructions and maintenance schedule, is able to meet the safety case functional requirements.

Interventions Carried Out by ONR

The system based inspection of the Gas Circulators was conducted against compliance with the following Licence Conditions (LCs):

The Dungeness B arrangements for monitoring the health of the system were examined. A plant walkdown of key areas associated with the Gas Circulators System was conducted. This included the Gas Circulator Hall for each reactor, containing the gas circulators and associated main motors, very low speed pony motors, and low speed/high speed pony motors. Inspections were conducted, on a sample basis, of the implementation of arrangements against each of the above Licence Conditions.

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

Explanation of Judgement if Safety System Not Judged to be Adequate

Based on the sample made, I judged that the Gas Circulators System fulfils the safety function and that the safety case has been adequately implemented.

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

From the intervention conducted, I summarise the following judgements for each of the Licence Conditions inspected:

The following observations were raised with the station during the inspection:

Conclusion of Intervention

From the sample inspected, it is judged that compliance against LC 10, 23, 24, 27, 28 and 34 met the required standard; therefore a 'Green' rating was given for all Licence Conditions. The Gas Circulators System is judged to meet the safety case requirements.