Office for Nuclear Regulation

System Based Inspection of HALES Containment Systems

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 (SDFW) Division. 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 containment systems 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 containment in HALES have been adequately implemented. The containment systems targeted in HALES were those structures, systems and components (SSCs) providing key safety case claimed functions relating to storage tank temperatures, transfer operations and the systems for detection and recovery of radioactive material outwith primary containment.

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.

ONR carried out a one and a half day SBI of the HALES containment systems. 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 inspection was performed in accordance with ONR guidance (detailed in ONR inspection guidance) available at

Explanation of Judgement if Safety System Not Judged to be Adequate

ONR judged the safety case for HALES containment systems to have been adequately implemented.

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

Loss of containment of radioactive materials is a hazard with the potential for significant consequences in HALES, owing to the nature of the material stored and processed.  The containment SSCs are key to ensuring that the radioactive materials remain in engineered containment and that any losses from the primary containment systems can be detected and recovered. 

SL demonstrated a good understanding of the limits and conditions which reduce the potential for loss of radioactive material from primary containment and the response to detection of material outwith primary containment.  Throughout the inspection, the SL staff interviewed were knowledgeable and professional and provided open and honest responses to ONR’s questions.

From the areas targeted and the evidence examined during this inspection, ONR consider that SL has adequately implemented the claims made in the safety case relating to the HALES containment systems.

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, LC 24, LC 27, LC 28 and LC 34 in accordance with ONR assessment rating guidance.