Office for Nuclear Regulation

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The Thermal Oxide Reprocessing Plant (THORP) on Sellafield Ltd's nuclear licenced site

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 compliance inspections of selected licence conditions, targeted at those facilities with significant importance to nuclear safety.

Two such licence condition inspections were performed to assess Sellafield Ltd.'s (SL's) compliance with Licence Condition (LC) 32 (Accumulation of radioactive waste) and LC35 (Decommissioning) in the Thermal Oxide Reprocessing Plant (THORP).  LC32 requires the licensee to make and implement adequate arrangements for minimising so far as is reasonably practicable the rate of production and total quantity of radioactive waste accumulated on the site at any time and for recording the waste so accumulated.  LC35 requires the licensee to make and implement adequate arrangements for the decommissioning of any plant or process that may affect safety, and to make arrangements for the production and implementation of decommissioning programmes.

The LC32 intervention was a routine compliance inspection. The LC35 intervention focused on progress with SL's preparations for Post Operational Clean Out (POCO) for the THORP facility, following up an inspection carried out in February 2016.  THORP will be the first major facility to enter POCO when reprocessing operations cease in 2018, and thus will present a learning opportunity for other facilities. POCO is a key enabler for safe plant decommissioning and forms part of SL's arrangements for compliance with LC35. 

Interventions Carried Out by ONR

A team comprising the THORP site inspectors (outgoing and incoming) and specialist inspectors in nuclear liabilities regulation, carried out two one day planned compliance inspections against LC32 and LC35.  These comprised discussions with SL personnel, reviews of SL records, documents and processes, and a plant walk-down in the case of the LC32 inspection.  The LC35 intervention was supported by the Environment Agency (EA).

We utilised the following ONR inspection guidance:

Explanation of Judgement if Safety System Not Judged to be Adequate

N/A as this was not a safety systems inspection.

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

LC32 Accumulation of Radioactive Waste

We noted significant progress in the management of radioactive wastes in THORP as a result of planning for POCO, with the removal of a number of historical accumulations of higher activity wastes for long term storage in appropriate site stores and the transfer of low-level wastes for disposal.  We welcomed clarification of the plan for management of accumulated reprocessing plant treatment sludge, with the aim of complete removal by the end of POCO. 

We considered that SL is taking proactive steps to develop inventories of accumulated wastes for the various parts of THORP.  This work is currently at an early stage, but is providing benefits by enabling identification of wastes which might need to be "co-processed" during reprocessing or which require early prioritisation. We noted that SL is planning work on inventories at a site level which will enable development of waste strategies and opportunities for improvements. Further work is needed to define waste quantities and categories and to apply appropriate governance and prioritisation.

However, SL was unable to provide adequate evidence of compliance with the requirement of LC32 to record the radioactive waste accumulated in THORP, of compliance with local waste management arrangements or to comply with the site requirement to store radioactive wastes in accordance with an appropriate safety case, particularly for temporary waste laydown areas. We observed examples of radioactive waste storage that did not meet relevant good practice, and observed evidence of non-compliance with plant procedures.

LC35 Decommissioning

SL has made good progress since ONR's inspection in February 2016 in developing its systematic and structured approach to planning POCO tasks in THORP, for those parts of the plant entering POCO at the end of reprocessing operations. SL has also made significant progress in reviewing and updating its site arrangements for POCO.  These now include a new procedure for documenting the planned end-states of specific parts of plant (cells), addressing a conclusion from the 2016 inspection.  We welcome the evolution of SL's position on the role and magnitude of resources of the central POCO capability from that presented in 2016, and its move into the Remediation operating unit will facilitate integration with waste management and decommissioning expertise.

THORP was able to provide adequate evidence to demonstrate compliance with the requirements in SL's POCO arrangements.   SL acknowledged the need for further work to clarify governance processes.  SL has made good progress in developing a plan for characterisation of THORP.  However, this has been developed without reference to the SL Characterisation Centre of Excellence.  We consider that the site's POCO Capability team should include this aspect in its future work on governance. 

We welcomed SL's continuing work on seeking and sharing Learning from Experience (LFE), including experience in French reprocessing plants.  We also welcomed the work to identify areas where it may not be possible to achieve the planned POCO end-state using native reagents and existing wash-out techniques, and where alternative methods and reagents may be appropriate, taking account of risks to downstream waste routes. 

Conclusion of Intervention

On the basis of the evidence gathered during the LC32 inspection, I judge that an inspection rating of AMBER (Seek improvement) is appropriate for compliance against LC32 (Accumulation of Radioactive Waste).  SL was unable to demonstrate compliance with arrangements for LC32 in THORP, and there is weakness in the implementation of safety case requirements relating to the storage of radioactive wastes.  We will raise a Regulatory Issue to address the shortfalls identified and issue the appropriate ONR enforcement communication to SL to seek the required improvements.

On the basis of the evidence gathered during the LC35 inspection, I judge that an inspection rating of GREEN (No formal action) is appropriate for compliance against LC35 (Decommissioning).  I consider SL to be compliant with its legal duties, with only minor areas for improvement being identified.  These will be taken forward as part of routine regulatory business.