Professional Engineering

An analysis of the Fukushima nuclear accident in Japan is to lead to a review of 38 technical and regulatory areas where lessons from the crisis can be learned in the UK.

The Office for Nuclear Regulation said the industry would be given one year to respond to the recommendations.

A report into the incident by Mike Weightman, Her Majesty’s chief inspector of Nuclear Installations and executive head of the Office for Nuclear Regulation, revealed no fundamental weaknesses in the UK's nuclear industry.

But Weightman said that government, industry and regulators should review 38 areas. These included: reliance on off-site infrastructure such as the electrical grid supply in extreme events, emergency response arrangements, layout of plant, risks associated with flooding, planning controls around nuclear facilities and prioritising safety reviews.

Weightman said: “I remain confident that our UK nuclear facilities have no fundamental safety weaknesses.

“The Office for Nuclear Regulation already requires protection of nuclear sites against the worst-case scenarios that are predictable for the UK. But we are not complacent. Our philosophy is one of continuous improvement. We will ensure lessons are learned from Fukushima. Action has already been taken in many cases, with work under way to further enhance safety at UK sites.

“While it is only six months since the earthquake and tsunami hit Japan, I am satisfied we are in a position to have drawn reliable conclusions and identified the main lessons to improve safety. Detailed technical information will no doubt continue to emerge and the Office for Nuclear Regulation will continue to monitor it and take action as necessary.”

Nuclear industry expert Dame Sue Ion, a fellow of the Royal Academy of Engineering, said Weightman's report reinforced the view that the future development of nuclear power in the UK can continue with the necessary regulations being in place and risk minimised.

“Lessons to be learned from the situation at Fukushima regarding back-up systems and supporting infrastructure would, as has always been the case in the UK, be incorporated into best practice going forward.

“Additionally the UK's safety regime through the way the ONR Inspectors operate anticipates potential combinations of events, such as those that occurred at Fukushimau20101, and the UK consequently has a robust, structured and comprehensive methodology for identifying design basis events.”

Here are some of the major recommendations relating to the nuclear industry:

Off-site infrastructure resilience
The UK nuclear industry should review the dependency of nuclear safety on offu2010site infrastructure in extreme conditions, and consider whether enhancements are necessary to sites’ self sufficiency taking into account the reliability of the grid under such extreme circumstances.

This should include:

• Essential supplies such as food, water, conventional fuels, compressed gases and staff, as well as the safe offu2010site storage of any equipment that may be needed to support the site response to an accident.
  
• Timescales required to transfer supplies or equipment to site.

Site and plant layout
The UK nuclear industry should review the plant and site layouts of existing plants and any proposed new designs to ensure that safety systems and their essential supplies and controls have adequate robustness against severe flooding and other extreme external events.

Fuel pond design
The UK nuclear industry should ensure that the design of new spent fuel ponds close to reactors minimises the need for bottom penetrations and lines that are prone to siphoning faults. Any that are necessary should be as robust to faults as are the ponds themselves.

Seismic resilience
Once detailed information becomes available on the performance of concrete, other structures and equipment, the UK nuclear industry should consider any implications for improved understanding of the relevant design and analyses.

The industry focus on this recommendation should be on future studies regarding the continuing validation of methodologies for analysing the seismic performance of structures, systems and components important to safety. This should include concrete structures and those fabricated from other materials.

Cooling supplies
The UK nuclear industry should review the need for, and if required, the ability to provide longer term coolant supplies to nuclear sites in the UK in the event of a severe offu2010site disruption, considering whether further onu2010site supplies or greater offu2010site capability is needed. This relates to both carbon dioxide and fresh water supplies, and for existing and proposed new plants.

The UK nuclear industry should review the site contingency plans for pond water make up under severe accident conditions to see whether they can and should be enhanced given the experience at Fukushima.

Combustible gases
The UK nuclear industry should review the ventilation and venting routes for nuclear facilities where significant concentrations of combustible gases may be flowing or accumulating to determine whether more should be done to protect them.