A flashover is an unintended electrical discharge, where light and heat are propelled through the air.

A spokesperson for AWE said they have indicated a guilty plea to the court and will enter the formal plea when they are sentenced in December.

The incident occurred in a non-nuclear building at the base on June 20, 2019, and the ONR say there was no radiological risk to workers or the public.

They described it as a “conventional health and safety matter”.

AWE said that the incident happened during a pre-demolition survey of a facility on the company’s Aldermaston site, when a contractor came into contact with a live circuit.

“The contractor was unharmed and sought medical advice as a precautionary measure,” a spokesperson continued.

“AWE has co-operated fully with the ONR’s formal investigation into the incident.

“AWE is committed to improving safety performance across its sites and will continue to work closely with its regulators to achieve this.

“We are unable to comment further at this time as the matter is subject to legal proceedings.”

The decision to commence legal proceedings follows an investigation into the incident by ONR, the UK’s independent nuclear safety regulator.

The case is scheduled to be heard at High Wycombe Magistrates’ Court on December 7, at 2pm.

AWE is currently under intensified scrutiny after being served with an improvement notice by the ONR last year.

The ONR also confirmed last year that it would continue to monitor AWE, who manufacture, maintain and develop warheads for the UK’s nuclear deterrent, Trident, until at least 2021.