Office for Nuclear Regulation

Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) inspection

Executive summary

Purpose of Intervention

This intervention, conducted at the Atomic Weapons Establishment (AWE) Aldermaston licensed site, was undertaken as part of the 2019/20 intervention plan and weapons sub-division strategy.

Interventions Carried Out by ONR

I conducted a planned Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) compliance inspection in the AWE Aldermaston Active Labs and Explosion Facilities.

Compliance with DSEAR is inspected against the Approved Code of Practice and guidance, which can be found at

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

Additionally I conducted routine chemical engineering engagements.

Explanation of Judgement if Safety System Not Judged to be Adequate


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

There were no significant findings identified during the DSEAR inspection of the Active Labs and Explosion Facilities

The inspection found that there had been improvements in DSEAR implementation across the site.  For example, there are no DSEAR zones within gloveboxes containing radioactive material.  This is a real improvement.  I also witnessed improvement in DSEAR zoning and hence reducing the ATEX rated equipment and the associated maintenance burden. However AWE acknowledged that the DSEAR verification dossier is still a work in progress. 

On balance, I consider an inspection rating of Green (no formal action) is merited against DSEAR as a result of this inspection.

Conclusion of Intervention

With regards to the DSEAR inspection my findings were shared with and accepted by the licensee as part of normal inspection feedback.

 In the case of other engagements I conducted with licensee personnel, no matters were identified as requiring additional regulatory attention.