Office for Nuclear Regulation

Compliance inspection against the Ionising Radiations Regulations 1999 (IRR99) on the Thermal Oxide Reprocessing Plant (THORP) Operational Unit  on Sellafield Ltd.’s nuclear licensed site in Sellafield, Cumbria

Executive summary

Purpose of intervention

This report presents the findings of an inspection that was undertaken at the Thermal Oxide Reprocessing Plant  (THORP) at the Sellafield nuclear licensed site in order to assess Sellafield Limited’s (SL) compliance with the Ionising Radiations Regulations 1999 (IRR99), with particular emphasis on arrangements for the control of radioactive sources.

This inspection was added to our THORP inspection plan following an event in April 2015 where SL temporarily failed to maintain control of one of its radioactive sealed sources, used for testing radiation detectors.  This inspection therefore focussed on whether the improvements put in place by SL following that event were still working effectively.

Interventions Carried Out by ONR

IRR99 places a number of duties that are relevant to the control and accountancy of radioactive sources, for example:

The licensee provided a summary of progress with regard to the THORP Management of Radioactive Sealed Sources Improvement Plan and how Condition Reports are processed within the operating unit.  The revised sealed source arrangements were examined by sampling inspection of two source stores and a temporary (“bonded”) store.  Inspection of a number of C0/C1 changerooms and C1/C3 sub-changerooms was also undertaken (here “C0” etc denotes the class of the radioactive contamination controls applied).  There was however no opportunity during the visit to examine radiological protection controls applied at the point of work.

Explanation of Judgement if Safety System Not Judged to be Adequate

N/A: this intervention was not a safety system inspection.

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

It was my opinion that the improvements SL has made to its arrangements for the control of radioactive sealed sources have been adequately implemented within the two source stores inspected.  I sampled source accountancy records, cross-checked source identifiers and descriptors against the actual sources, and examined security seals utilised in the accountancy process and found no shortfalls within the source stores or relating to those installed sealed sources I examined on the plant. 

I was however unable to fully reconcile the source transfer records kept within the Head End Bonded Store with those within the source store from which the sources originated.  Here I received and accepted assurance from the licensee that the bonded store arrangements had already been identified as a weakness and that active consideration was being given to re-designating the bonded store as a radioactive source store.  I considered that this action would adequately address my identified shortfall and have recommended that it be implemented. 

I also noted that, although adequate records were kept relating to the Suitably Qualified and Experienced Person (SQEP) status of source users, Radiation Protection Supervisors (Sources), and their deputies, these records did not extend to those shift health physics personnel who are also required to account for sources.  I have therefore also recommended that consideration be given to the implementation of similar records for these personnel.

Each of these recommendations is minor and neither undermines my opinion that the arrangements I saw are adequate for securing compliance with relevant portions of IRR99.

Conclusion of Intervention

The intervention provided the opportunity to carry out an extensive examination of SL’s improved arrangements for the control and accountancy of radioactive sealed sources within THORP following the April 2015 event.  Based on my observations, I conclude that the arrangements within the designated source stores constitute relevant good practice and that these or similar arrangements should be introduced into any bonded store in which sources may be retained between shifts.  During my observations on plant and within changerooms I noted no matters of radiological concern.   As such I awarded an IIS rating of 3 (adequate) for this inspection, though I have also raised a Level 4 Regulatory Issue to track the resolution of my concerns in regard to source accountancy arrangements within the Head End Bonded Store.