ONR Presentation to
NuLeAF
Tanya MacLeod
Responsibilities
• Prime responsibility for the assessment and
management of Flood and Coastal Risk on site rests
with the ‘duty holder’ – i.e. the Licensee
• ONR is responsible for regulating nuclear safety on
nuclear licensed sites, including the safety implications
associated with hazards arising from flood and coastal
erosion.
• The EA is the principal flood risk management authority
in England providing a strategic overview relating to all
forms of flood risk (SEPA, NRW).
About ONR – the work we do
• The Office for Nuclear Regulation's mission is to provide
efficient and effective regulation of the nuclear industry,
holding it to account on behalf of the public.
• ONR regulates 37 nuclear licensed sites across
England, Scotland and Wales
• ONR is responsible for the regulation of nuclear safety,
security, safeguards, transport, and conventional health
and safety at licensed sites
• Protection from flood hazards is a well established part
of ensuring safety at nuclear sites in the UK.
Protecting Nuclear Sites
• The Licensee must set out how an acceptable level of
safety will be achieved in a safety case. ONR’s
expectations as set out in SAPs are:
– Risks are As Low as Reasonably Practicable (ALARP)
– Design Basis, this is a “1 in 10,000 /yr event” for natural hazards
– There should also not be a disproportionate increase in risk for
more extreme events
– Margin and a defence-in-depth approach to safety are essential
to ensuring minimal public and worker risk
– Redundancy, Diversity, Segregation, Separation
Tolerability of Risk and ALARP
• ALARP = As Low as Reasonably
Practicable
• “So Far as is Reasonably
Practicable” is the primary legal
requirement from the Health and
Safety at Work Act, translated to
ALARP in the SAPs (Safety
Assessment Principles)
• Key references:
Reducing risks protecting people: HSE’s
decision making process (R2P2)
The tolerability of risks from nuclear
power stations (TOR)
ONR SAPs (Safety Assessment
Principles)
Assessment and Mitigation
• The safety case needs to consider still seawater
levels, precipitation, storm surge, tides, tsunami, river
flows and erosion and some of these will be affected
by climate change. Local topography, bathymetry and
shoreline management can all influence the nature of
the hazard.
Most preferred
Hierarchy of safety measures:
Passive safety measures
Automatically initiated active engineered
safety measures.
Active engineered safety measures that
need to be manually brought into service in
response to the fault.
Administrative safety measures
Mitigation safety measures
Least preferred
Typical flood protection includes:
Site platform level
Sea-walls/sand dunes
Site drainage and site topography
Local protection such as damboards and
building base height
Forecasting and advanced warning systems
Pumping out buildings in the event of water
entry
Access Roads
Access roads may become flooded. This is not considered a major
issue because, if flooded by the sea, the tidal cycle over these
timescales will typically naturally render the site accessible (although
impoundment is possible). Generally AGR and Magnox sites have a
minimum of 24 hours (driving towards 72 hours) before they claim any
need for off-site assistance following severe loss of safety -critical
equipment.
Mobile equipment held off-site: e.g. ATV's designed to drive through
water, mobile cranes for access and site clearance, etc
Shut-down reactors (Oldbury, etc): no
immediate or short term actions (i.e. within a
few weeks) are necessary to ensure adequate
fuel cooling should a flooding event occur
Learning from Experience
Post-Fukushima Review Completed
Recommendation IR-10: The UK nuclear industry should
initiate a review of flooding studies, including from
tsunamis, in light of the Japanese experience, to confirm
the design basis and margins for flooding at UK nuclear
sites, and whether there is a need to improve further sitespecific flood risk assessments as part of the periodic
safety review programme, and for any new reactors. This
should include sea-level protection. Supporting off-site
infrastructure is also at risk from natural hazards and
nuclear sites need to ensure adequate self sufficiency in
the event of loss of off-site services etc (e.g. see IR-8)
New Build Sites
• 8 proposed nuclear new
build sites in the UK to
be sited along the coast
• 5 of these are at least
partially in Flood Zone 3
– High Risk*
• Strategic level
assessments carried out
by EA suggest that all
potential new sites
identified in the National
Policy Statement for
nuclear power plants in
England and Wales
could potentially be
protected from flooding.
*Key reference: DECC, National Policy Statement
for Nuclear Power Generation EN-6, July 2011