AREVA’s 3G reactors failsafe: NPCIL

The safety of nuclear power plants has become the hot topic of debate everywhere after the Fukushima disaster. Safety concerns have been raised over the 9,900 MW Jaitapur nuclear power project (JNPP).

DNA got in touch with the Nuclear Power Corporation of India Limited (NPCIL) to answer queries over the safety standards of the evolutionary pressurised reactors (EPRs) designed by French nuclear power giant AREVA. Following is NPCIL’s response:

EPR is the name of AREVA’s Generation III+ high power output pressurized water reactor (PWR). The EPR was designed to satisfy the demands of electricity utility companies for a new generation of nuclear power plants that offer increased levels of safety and competitiveness today while more efficiently meeting the energy requirements of tomorrow. The EPR showed an “excellent level of compliance” during its 2009 review by a group of major European electricity producers, demonstrating over 99.9% conformity with the criteria detailed in the European Utilities Requirements (EUR) document. The EPR is optimised to meet the higher safety requirements of the new generation of nuclear power plants while offering competitively priced power generation.

The EPR design features four separate safety subsystems known as “safety trains”. Additionally, these four redundant trains are physically separated from one another and located in four independent buildings to further prevent a simultaneous failure of the trains. Each safety building of an EPR includes one train of a system for injecting water into the reactor vessel in case of a loss of coolant, the steam generator emergency feed water system, and the electrical and instrumentation & control (I&C) systems.
The presence of four safety trains in the EPR enables more online maintenance. The EPR features a fully digital I&C system, which reduces the risk of human error by providing the operator with technical and operational support as well as instructions in the case of an ‘abnormal’ situation. To minimise the human risk, short-term protection and safety actions needed in the event of an incident or accident have been automated.

Probabilistic safety assessments reveal that the EPR has a vanishingly low probability for severe accidents: less than one accident every 10,000 years for a fleet of 1,000 EPRs. The EPR has been designed such that in the highly improbable event of an emergency situation inside the reactor or the presence of an unexpected external hazard (e.g. a large commercial aircraft crash), the impact would be limited to the industrial site itself and have no lasting effect on the surrounding population. The EPR building is protected by a thick outer shell of reinforced concrete and a thick inner shell of pre-stressed concrete. The inner shell is covered with a thick metallic liner.

To withstand severe earthquakes, the entire nuclear island stands on a single 6m thick reinforced concrete basement. The height of the buildings has been minimised to make them resistant to earth tremors, and the heaviest components, in particular the water tanks, are located at the lowest possible level.

As the EPR was designed for countries with high population density, its safety features have been designed to confine the consequences of an unlikely accident inside the plant’s perimeter. They meet the requirements of French and German nuclear safety authorities in this regard.