Response:
The Flamanville 3 EPR unit under construction in France is on a Channel coastal site. Consequently the issue of the sea level rise (in this case up until 2070) was addressed in 2005 in order to determine the Maximum Safety Water Level (MSWL), which is the load case for the Exceptional Coastal Flooding hazard. This is the most demanding for External Flooding hazards.
The requirements related to the protection against external flooding, used for the design of the EPR ensure that buildings housing safety classified equipment are kept dry. This is achieved by setting the platforms and the ultimate heat sink equipment (pumps and filtration devices) at a level at least equal to the Maximum Design Flood Level. Similar consideration would apply for a UK coastal site.
In 2005, the maximum sea level was calculated considering the best scientific consensus at the time, namely the Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC). The average sea level rise given then was a range from 0.09 to 0.88 m (according to diverse scenarios) between 1990 and 2100. This estimation given by global climate models has been compared to measurements made in different places in western France. Statistical works on sea levels show an average sea level rise in Brest in the order of 1 mm per year between 1860 and 1995 (this location has been selected because of its longer chronicle). So the measurements are consistent with the model estimates.
Since 2005, the IPCC has continued to work on this topic. A new assessment report (AR4) was issued in 2007. The sea level rise range in this report is 0.18 to 0.59 m in the decade 2090-2099, with the note that this range is ?excluding future rapid dynamical changes in ice flow? (ref [1]).
Hansen?s paper (ref [2]) is not a presentation of new scientific results on sea level rise, but a discussion about the above AR4 exclusion. Hansen gives some arguments on ice flow dynamics being non-linear and states that the sea level rise will be dominated by ice sheet disintegration. The 5m sea level rise is the result of a rough calculation based on two main assumptions: (1) ice sheet contribution is 1cm in the decade 2005-2015 and (2) this contribution doubles each decade. Such assumptions need further scientific work and the calculation of sea level rise needs more accurate modelling.
The IPCC AR4, in its last part ?The long-term perspective? opens the prospect of future work on this issue, since ?...the risk of additional contributions to sea level rise from both the Greenland and possibly Antarctic ice sheets may be larger than projected by ice sheet models and could occur on century time scales.? (Ref [1] p.19).
In conclusion therefore, the postulated potential sea level rise value of 5m given in Hansen?s paper is not sufficiently refined to be used in the siting design of new reactors; it is not yet confirmed by measurements and is derived from a rough calculation, the purpose of which is not to scientifically model the sea level rise. Nevertheless, as ice dynamical processes seen in recent observations could increase the rate of ice lost, the scientific work on this matter will be followed carefully, and the siting design of coastal plants to be built around 2015 will be adapted to the results when they are available.
[1] Climate Change 2007 : Synthesis Report ? Summary for Policymakers - IPCC web site
[2] Scientific reticence and sea level rise ? J E Hansen -
http://pubs.giss.nasa.gov/docs/2007/
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Yours faithfully
The UK EPR GDA Project
A joint project of AREVA and EDF
