Office for Nuclear Regulation

System Based Inspection - Cranes Structures

Executive summary

Purpose of Intervention

This planned intervention was undertaken as part of the 2020/21 intervention plan and propulsion sub-division strategy. Due to the restrictions from the COVID19 pandemic, the intervention was undertaken fully remotely with support on site of DRDL Independent Nuclear Oversight.

Dockside lifting operations on DRDL site represent one of the major challenges to nuclear safety. The integrity of the dockside cranes structures is therefore essential. The purpose of this inspection was for ONR to examine whether safety case claims in respect of the reliability of cranes structures have been adequately implemented.

ONR inspection targeted the two dockside cranes in 15 Dock Submarine Refit Complex and sought evidence to determine compliance against five relevant key Licence Conditions (LCs): 10, 23, 24, 27, and 28. These LCs provide a structured approach to assess the way the system inspected is operated and maintained and determine whether the safety case requirements, limits and conditions have been implemented adequately.

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

Not applicable.

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

From the areas targeted and the evidence examined during this inspection, ONR considers that DRDL has adequately implemented those safety case claims that relate to the dockside cranes structures.

No matters were identified as requiring immediate regulatory attention during the conduct of this system based inspection.

It is my opinion from the sampled evidence provided by the Licensee that the material condition of the cranes structures is generally good and appear to be in good working order and adequately maintained with only minor signs of degradation. It is my opinion from ONR interactions with the Licensee during the remote inspection and the evidence provided that there is a good level of awareness and control of the limits and conditions applicable to cranes structures in relation to the prevailing weather and vehicles impacts.

ONR noted two areas of good practice. DRDL demonstrated a robust control over the corrosion of the cranes structures, particularly with a robust quality control and the high level of care given to the application of corrosion prevention coating. DRDL has also demonstrated good practice with the systematic approach to training developed for the personnel in charge of crane maintenance.

ONR made two regulatory observations that will be followed as part of routine regulatory engagement with the site.

The first relates to the cranes structures being solely visually inspected albeit initially expected to receive a ten yearly 100% Non-Destructive Examination of the critical welds. Whilst DRDL presented a valid case for the change, good practice would expect that some level of NDE should be carried out to validate the cranes structures visual inspection e.g. similarly to DRDL visual and NDE of the cranes luff and hoist ropes.

A second regulatory observation was made regarding the training provision for the Technical Authority Structural Engineer training undertaking the annual visual inspection of the cranes. DRDL could not provide a robust demonstration that the individual was trained and experienced in undertaking the inspection. ONR expects a uniform systematic approach to training to be applied across the board and for DRDL to implement the same approach developed, for example for the crane maintenance personnel, to other personnel undertaking work that may affect safety.

Conclusion of Intervention

Notwithstanding the limited assurance from undertaking this system based inspection remotely, overall I judged from the body of sampled evidence provided during the intervention that the licensee demonstrated adequate compliance with the requirements of the LCs considered in relation to the system inspected, cranes structures.

On the basis of the evidence seen during the intervention, ONR has given an inspection rating of green for the five relevant LCs considered (LC 10 training, LC 23 Operating Rules, LC 24 Operating Instructions, LC 27 Safety Mechanisms Devices & Components and LC 28 Examination Inspection Maintenance & testing).