This intervention was to investigate EDF Energy Nuclear Generation Limited (NGL’s) own investigation of Local Exhaust Ventilation (LEV) adverse conditions that arose during vessel entry work which was part of Hunterston B power station’s statutory outage maintenance programme undertaken in 2014.
This intervention sought to establish NGL’s on-going compliance with the Ionising Radiations Regulations 1999 in relation to the matters investigated and in its ACIN.
No system inspection was undertaken during this intervention.
NGL’s investigation was effective in identifying the causes of the LEV efficacy failures which had led to a number of low-level personal contamination events involving vessel entry workers (i.e. low personal doses). The investigation was also conclusive on the improvements that need to be made to LEV operation and maintenance in future and on the need for better training and operational oversight of the ventilation systems that contribute to the establishment of effective LEV during vessel entry work programmes at the Station.
Overall, I was satisfied with the corrective action that NGL was proposing to take and with the urgency it had given this work, principally that it should be completed before commencement of the Hunterston B 2015 statutory outage.
The intervention was performed in line with ONR’s guidance requirements (as described in our technical inspection guides) in the areas inspected.
There were no findings from my investigation that indicated that there had been at any time a shortfall in the maintenance of nuclear safety.