Office for Nuclear Regulation

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Spent Fuel Management - HALES System Based Inspection (Ventilation)

Executive summary

Purpose of Intervention

The Office for Nuclear Regulation (ONR) undertakes all regulatory interaction with the Sellafield site licensee (Sellafield Limited, SL) against a strategy defined by the ONR Sellafield Sub Division. In accordance with that strategy, a System Based Inspection (SBI) was carried out on the Highly Active Liquor Evaporation and Storage (HALES) plant, as planned, on 17-18th July 2019. 

Interventions Carried Out by ONR

The purpose of this inspection was for ONR to examine whether the licensee’s safety case claims in respect of the HALES ventilation system have been adequately implemented. The inspection targeted the whole of the HALES ventilation system with particular attention given to the Vessel venting system.

ONR’s SBI process examines evidence to determine compliance against six Licence Conditions (LC). These LC’s, listed below, have been selected in view of their relevance to ensuring nuclear safety and provide a structured approach to determining whether the safety case has been implemented adequately through the system being inspected.

LC 10 requires SL to make and implement adequate arrangements for suitable training for all those on site who have responsibility for any operations which may affect safety.

LC23 requires SL to produce an adequate safety case to demonstrate the safety of its operations, and to identify the conditions and limits necessary in the interests of safety.

LC24 requires SL to ensure that all operations which may affect safety are carried out in accordance with written instructions.

LC27 requires SL to ensure that a plant is not operated, inspected, maintained or tested unless suitable safety mechanisms, devices and circuits are properly connected and in good working order.

LC28 requires SL to make and implement adequate arrangements for the regular and systematic examination, inspection, maintenance and testing of all plant which may affect safety.

LC34 requires SL to ensure, so far as is reasonably practicable, that radioactive material and radioactive waste on the site is at all times adequately controlled or contained so that it cannot leak or otherwise escape from such control or containment. 

Explanation of Judgement if Safety System Not Judged to be Adequate

Based upon the areas sampled I judge that the safety case requirements for the HALES ventilation system have been adequately implemented.

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

For LC10; I sampled the training of four HALES employees (operators and maintenance engineers) associated with the operation and maintenance of the pre-selected safety mechanisms.  From the evidence provided I was satisfied that individuals sampled had completed the required training requirements and were deemed suitably qualified and experienced for those tasks.  I therefore judge that the required standard is met and an inspection rating of Green (no formal action) is appropriate against LC10.

For LC23; I was satisfied that the safety case clearly identifies the fault sequences and the HALES plant has appropriate limits and conditions to protect against the faults identified within the safety case. During the plant visit, the SL operational employees showed knowledge of the Operating rules associated with the HALES safety case. Based on the evidence sampled, I judge that the required standard is met and an inspection rating of Green (no formal action) is appropriate.

For LC24; I was satisfied that the associated operating and maintenance instructions were adequate to ensure compliance with the limits and conditions identified in the safety case and the Operating rules. I therefore judge that the required standard is met and an inspection rating of Green (no formal action) is appropriate.

For LC27; I was satisfied that the appropriate Safety Mechanisms (SM), Safety Related Equipment (SRE) and Safety Features (SF) had been identified within the safety case and had been correctly designated. During the plant visit I was able to visually inspect the preselected safety mechanisms and gained confidence that the safety mechanisms on the plant were in an adequate condition. I therefore judge that the required standard is met and an inspection rating of Green (no formal action) is appropriate.  

For LC28; prior to the inspection I requested the last completed maintenance tasks for a number of safety mechanisms associated with the safety case for HALES ventilation system and a copy of the System Health Reports for those systems. From the maintenance records sampled I was satisfied that the safety mechanisms selected were being adequately maintained. From the system health reports sampled, I was satisfied that the condition of the plant was known and appropriate measures are in place to repair the known defects.   I therefore judge that the required standard is met and an inspection rating of Green (no formal action) is appropriate.

For LC34; from the information provided, I was satisfied that the appropriate measures were in place to prevent and manage the leakage and escape of radioactive material in connection with HALES ventilation system. I therefore judge that the required standard is met and an inspection rating of Green (no formal action) is appropriate against LC 34.

I also carried out preliminary enquiries into a recent event on the HALES ventilation system where a HEPA filter had failed its Dispersed Oil Particulates (DOP) test. SL provided an overview of the Basic Cause Investigation (BCI) for this event and the actions taken to resolve the issue. On the basis of our discussions I judge that SL has taken appropriate action to resolve the issue and that this event does not meet the ONR investigation criteria.

The intervention was performed in line with ONR's guidance requirements (as described in our technical inspection guides) in the areas inspected.

Conclusion of Intervention

From the evidence gathered during this intervention, I do not consider there to be any matters that have the potential to impact significantly on nuclear safety.    

At present, no additional regulatory action is needed over and above the planned interventions within the Spent Fuel Management Operating Unit at the Sellafield Nuclear Site as set out in the Integrated Intervention Strategy, which will continue as planned.