Hunterston B cabling incident at EDF: electrical safety lessons for engineers
Reviewed by Tom Sullivan
First reported on The Construction Index
30 Second Briefing
EDF Energy has been served an improvement notice by the Office for Nuclear Regulation after 415V electrical cabling was deployed unsafely during work on cooling water valves at the Hunterston B nuclear power station in Ayrshire in November 2025, creating a significant potential risk to workers. The notice compels EDF to review, revise and implement arrangements for the construction, maintenance, testing and control of all 415V portable equipment, and to strengthen risk assessments and procedures for electrical work. Compliance is required by 20 March 2026 under Section 2 of the Health and Safety at Work Act 1974 and multiple Electricity at Work Regulations, including Regulations 4, 7, 10 and 14.
Technical Brief
- Incident involved 415V portable electrical equipment used around cooling water valve works at Hunterston B.
- ONR judged cabling deployment as unsafe specifically during valve maintenance in one of the station’s facilities.
- No physical injuries occurred, but ONR assessed the potential for serious harm as “significant”.
- Improvement notice explicitly targets construction, maintenance, testing and control arrangements for all 415V portable kit on site.
- EDF must upgrade arrangements for personnel competence and procedures when undertaking electrical work at Hunterston B.
- Legal basis combines Health and Safety at Work Act 1974 s.2 with Electricity at Work Regulations 1989.
- Electricity at Work focus spans systems and PPE (Reg 4), insulation/segregation (Reg 7), terminations (Reg 10) and live-working controls (Reg 14).
Our Take
Hunterston B sits within the United Kingdom’s mature nuclear fleet, and in our infrastructure safety coverage ONR interventions at legacy plants often trigger wider reviews of portable and temporary electrical equipment standards across an operator’s entire estate, not just the named site.
The explicit linkage to the 1974 Health and Safety at Work Act and the 1989 Electricity at Work Regulations suggests EDF Energy may need to tighten its corporate-level electrical isolation and inspection regimes for 415 V tools and leads, which can have knock-on implications for contractors’ method statements and permit-to-work systems on other UK assets.
Among the 436 safety-tagged infrastructure pieces in our database, formal improvement notices with a fixed compliance date like the 20 March 2026 deadline typically precede more intrusive regulatory action only where operators miss milestones, so EDF’s response at Hunterston B will be watched as a bellwether for ONR’s enforcement stance at other decommissioning-era nuclear sites.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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