Office for Nuclear Regulation

System Based Inspection of the HALES Cooling Water System

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, Decommissioning, Fuel and Waste Division (SDFW). The inspection plan, PP5, for the Operational Waste Facilities (OWF) details a strategic programme of regulatory inspections which includes a System Based Inspection (SBI) of the cooling water system in the Highly Active Liquor Evaporation and Storage (HALES) facility.

The purpose of this inspection was for ONR to examine whether the licensee’s safety case claims in respect of the HALES cooling water system have been adequately implemented. The cooling water systems targeted in HALES were those responsible for supporting a number of structures, systems and components (SSCs) important to safety. These SSCs provide key safety case claimed functions including the removal of the decay heat and hydrogen generated by the highly active liquors processed and stored in the facility.

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.

Interventions Carried Out by ONR

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.

On this occasion, LC 34 (leakage and escape of radioactive materials) was not included in the System Based Inspection as ONR judged that it was not directly applicable to the system under consideration.

ONR carried out a two day SBI of the HALES cooling water system. Sellafield’s Nuclear Independent Oversight (NIO) participated in the inspection. The inspection comprised discussions with SL staff, a targeted plant walkdown and a review of plant records and other documentation.

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

ONR judged the safety case supporting HALES cooling water system to be adequate.

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

From the evidence made available during the inspection, ONR consider that SL has adequately implemented the claims made in the safety case which relate to the HALES cooling water system.

The loss of cooling represents the hazard with the highest potential consequences in HALES, owing to the nature of the material stored and processed. ONR acknowledge that the heat loading of the inventory currently stored and processed in HALES is significantly lower than the historic inventory and the plant design basis. As a result the burden on the cooling water system is less onerous than that currently justified within the safety case, and the facility has longer to respond to a loss of cooling before any adverse consequences would occur.

SL demonstrated a good understanding of how the facility would react to the loss of cooling water, and how long this could be tolerated before there would be any radiological consequences. ONR were satisfied that contingencies are in place to ensure that cooling water supply is maintained.

Throughout the inspection, the SL staff interviewed were knowledgeable and professional; and provided open and honest responses to ONR’s questions. It was noted that currently there are no role profiles for the operators detailing the minimum qualifications and experience for the roles undertaken. Whilst ONR found no evidence to raise concerns with the competence of the operators, the facility was unable to demonstrate that competence.  Consequently a Level 4 Regulatory Issue was raised to address this shortfall. This does not detract from ONRs overall inspection conclusions.

Conclusion of Intervention

Based on the evidence sampled during this inspection, I judge that SL has adequately implemented the claims made in its safety case. I therefore consider that inspection ratings of Green (no formal action) are appropriate against LC 10, LC 23, LC24, LC27 and LC28 in accordance with ONR assessment rating guidance. Licence condition LC 34 was judged not relevant for this system based inspection.