Office for Nuclear Regulation

Atomic Weapons Establishment Aldermaston – Inspection ID: 52836

Executive summary

Date(s) of inspection:

  • August 2023

Aim of inspection

This intervention will be undertaken alongside The Environment Agency. The purpose of this inspection is to form a view on the adequacy of AWE ventilation management arrangements.  We will also seek the demonstrable achievement of a sampled set of safety and environmental related claims identified from an AWE facility safety case. This intervention forms part of the evidence gathering for the closure of Regulatory Issue 7034.

Subject(s) of inspection

  • LC28 – Examination, inspection, maintenance and testing – Rating: Green

Key findings, inspector’s opinions and reasons for judgement made

In accordance with the Office for Nuclear Regulation’s (ONR’s) weapons sub-division Strategy, ONR performs planned compliance inspections of selected licence conditions, targeted at areas of significant importance to nuclear safety. This record describes the outcome from a planned compliance inspection at the Atomic Weapons Agency (AWE) Aldermaston site. This inspection was undertaken in conjunction with the Environment Agency. The purpose of the inspection was to confirm AWE’s compliance to its corporate arrangements for Licence Condition 28 (LC28)  (Examination, Inspection, Maintenance and Testing (EIMT)) relating to ventilation systems. This aligns with desired regulatory outcome 5.1 within the weapons sub-division strategy and forms part of AWE’s evidence to demonstrate shortfalls identified in regulatory issue 7034 have been addressed.

On the 30th and 31st August 2023, I carried out a planned licence condition compliance inspection, sampling AWE’s ventilation management arrangements. The purpose of this inspection was for ONR to determine the adequacy of the licensee’s formal ventilation management arrangements for compliance with LC28.This inspection comprised of discussions with AWE staff and reviews of plant records and other documentation.

Prior to the LC28 inspection, I undertook a review of the relevant AWE arrangements for ventilation management against the ONR guidance documents. From the areas sampled, I did not identify any significant shortfalls in the licensee’s formal arrangements for compliance with LC28 which would prompt an inspection of these arrangements earlier than currently planned.

To judge the adequacy of the ventilation management arrangements I asked AWE to explain how it has identified and incorporated relevant good practice. AWE explained how it has developed its overarching arrangements, reviewing appropriate standards, identifying relevant good practice and incorporating operational experience through collaboration with other duty holders. AWE is currently implementing its revised ventilation management arrangements. It is undertaking a pilot programme at A**.7. This will allow AWE to undertake a review learn and improve process. Arrangements will be updated if required as implementation is progressed across AWE. ONR will monitor progress as part of routine regulatory engagement.

I requested information on the storage arrangements for HEPA filters. AWE informed me that it does not intend to store filters but order them on demand. However, I note that AWE/MAN.SYS/6748 requires HEPA filters to be stored in environmentally controlled conditions with a temperature range of 5-30° C. The Environment Agency has an extant regulatory recommendation on the same subject. Progress will be monitored by both the Environment Agency and ONR as part of routine regulatory engagement.

I reviewed maintenance records for ventilation structures systems and components for a number of facilities. Maintenance periodicity was seen to be line with recommendations set out within AWEs ventilation arrangements (AWE/MAN.SYS/6748).


On the basis of the intervention evidence sampled at AWE in relation to LC28, I judge that the licensee has adequate arrangements in place for ventilations systems. I consider relevant good practice to be generally met in comparison to the appropriate benchmarks. Therefore, I have assigned and inspection rating of green(no formal action required).