Office for Nuclear Regulation

Planned System Based Inspection (SBI) of the Shearing and Dissolver Operations Systems within THORP

Executive summary

Purpose of intervention

In accordance with the Office for Nuclear Regulation’s (ONR’s) Sellafield Strategy, each year ONR performs a series of planned system based inspections (SBIs) targeted at key safety significant systems on those facilities with the potential to give rise to offsite effects to the public. The purpose of this inspection was for ONR to determine the adequacy of implementation of Sellafield Ltd.’s (SL’s) safety case claims in respect of the Thermal Oxide Reprocessing Plant’s (THORP’s) Shearing and Dissolver Operations system.

Interventions Carried Out by ONR

ONR carried out a 2 day inspection of the Shearing and Dissolver Operations system between 21 - 22 October 2015 utilising specialists from the following technical disciplines:

In order to determine the adequacy of implementation of the licensee’s safety case claims in respect of this system, as part of all system based inspections, we examined evidence regarding the implementation of Sellafield Ltd.’s arrangements regarding six pre-defined licence conditions, listed below. These have been selected in view of their importance to nuclear safety and are defined within ONR’s formal process for system based inspection. The inspection involved reviewing the applicable safety case claims and sampling, through a combination of document reviews, discussions with operators and plant inspections, suitable evidence to determine compliance against these LCs on the plant.

ONR assessed compliance in THORP with the following Licence Conditions (LCs) using the applicable ONR inspection guidance:

In addition to this system based inspection, I met with senior members of the THORP management team to discuss current areas of regulatory focus.

I also carried out an unannounced review of compliance documentation to confirm that required checks and surveillances were being adequately completed.

Explanation of Judgement if Safety System Not Judged to be Adequate

I judge the safety system to be adequate.

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

Shearing and Dissolver Operations System Based Inspection

It is my opinion, based on the sampling undertaken, that SL has demonstrated that the THORP shearing and dissolver operations system has been adequately implemented in accordance with the safety case requirements.

It is my opinion that, whilst some potential minor improvements were identified to Sellafield Ltd, LCs 10, 23, 27, 28 and 34 are all adequately implemented with regards the shearing/dissolver operations system. Consequently, it is my opinion that an IIS rating of 3 (Adequate) was considered appropriate for these licence conditions. With regard to LC24; operating instructions it is my opinion that an IIS rating of 2 (Good Standard) is warranted. The is due to the high standard of operational documentation used to ensure compliance with regards to shearing/dissolver operations which I consider exceeds guidance requirements.

Unannounced Compliance Documentation Review of the THORP Control Room

Whilst I consider that overall compliance check requirements were generally being completed, I noted several opportunities for improvement regarding the rigour with which checks, readings etc. were completed. I do, however, acknowledge that this is a recognised area for improvement and THORP has put in place a comprehensive improvement programme aimed at raising generally raising standards in conduct of operations.

Conclusion of Intervention

I judge that based on the sampling undertaken, the shearing and dissolver operations systems adequately fulfil their safety case requirements to ensure nuclear safety during reprocessing operations.