Office for Nuclear Regulation

Fuel Route system Based Inspection (SBI) - Fuelling Machine & Plug Unit Maintenance Facility

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake a system based inspection of the Fuelling Machine (FM) and Plug Unit Maintenance Facility (PUMF) systems at EDF Energy Nuclear Generation Limited’s (NGL) Dungeness B power station in line with the planned inspection programme contained in the Dungeness B Integrated Intervention Strategy (IIS) for 2020/21.

The inspection was undertaken by a multi-disciplinary team of ONR inspectors, including C&I, fault studies, internal hazards and mechanical engineering specialist inspectors. Given the restrictions in place due to the coronavirus pandemic, this inspection was carried out remotely using teleconferencing facilities.

The aim of the SBI of the FM and PUMF systems was to judge the systems performance against their safety function. The purpose of the FM is to transfer fuel assemblies, control rod assemblies and other non-fuel assemblies including interstitial plug assemblies between the reactor channels of both reactors and other facilities. The purpose of the PUMF is to allow operators to test, maintain, refurbish, replace and store plug units while minimising their exposure to radiation as far as practicable. Through examination of these systems, compliance inspections were performed against Licence Conditions (LC) which are applicable provisions of the Energy Act 2013.

The inspections were based on sampling the implementation of the licensee’s arrangements at Dungeness B power station against the LCs. The objective of the inspection was to determine whether the licensee’s arrangements were adequately implemented and in accordance with the systems’ safety case requirements.

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 our sample, we considered that the requirements of the safety case for the PUMF have not been adequately implemented at Dungeness B Power Station. This is particularly in regards to examination, inspection, maintenance and testing (LC28), which we rated as Amber. The ratings under each Licence condition are discussed further below. A number of regulatory issues have been raised to address the shortfalls identified with the systems. There are currently no operations required to be carried out within the gloveboxes/partial enclosures or using the hoists prior to return to service, and therefore despite the significant shortfalls identified, we are content that these regulatory issues will resolve the shortfalls prior to the next use of the gloveboxes/partial enclosures and hoists. Additionally we advised that the Licensee needed to demonstrate that the gloveboxes and partial enclosures are safe to operate prior to their next use.

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

From the System Based Inspection on the Fuelling Machine and Plug Unit Maintenance Facility, we concluded that:

Conclusion of Intervention

After considering all of the evidence presented by EDF NGL we concluded that the arrangements and their implementation, associated with the PUMF did not meet the requirements of the safety case in terms of LC28 (Examination, Inspection, Maintenance and Testing). There are no foreseen operations are to be carried out in the gloveboxes/partial enclosures or using the hoists prior to return to service, and therefore we are content that the regulatory issues will resolve the shortfalls prior to next use of the plant. Additionally we advised that the Licensee needed to demonstrate that the gloveboxes and partial enclosures are safe to operate prior to their next use. An IIS rating of Amber (seek improvement) is considered to be appropriate for the system based inspection. The system based inspection resulted in a number of areas for improvement of varying significance being identified. We raised a number of Regulatory Issues with Dungeness B to address these.