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Controlled experiments boost reactor safety

A series of experiments in light-water reactors has helped researchers identify the impact of severe accidents, such as loss of coolant, and to strengthen related safety codes.
Controlled experiments boost reactor safety
Light-water reactors (LWRs) are considered simpler and less expensive to build than other types of nuclear reactors, representing most of the nuclear reactors in service today around the globe. The EU-funded ERCOSAM (Containment thermal-hydraulics of current and future LWRs for severe accident management) project investigated the containment thermal-hydraulics of current and future LWRs for severe accident management. The project included teams around Europe and as well from Canada and USA.

In a joint effort with the ROSATOM-funded project SAMARA, the ERCOSAM project partners had two main objectives. On the one hand, they wanted to establish the strength of hydrogen (helium was used as substitute for hydrogen) stratification in case of a postulated accident. On the other, they aimed to establish if this stratification can be broken down by the operation of Severe Accident Management systems (SAMs), i.e. sprays, coolers and Passive Auto-catalytic Recombiners.

After defining the tests to be conducted, the project team identified the most suitable facilities for these experiments in France, Russia and Switzerland. It considered accidents involving containment pressurisation, hydrogen stratification build-up, stratification break-up, gas mixing, condensation, re-evaporation, depressurisation under the effect of spray, and cooler or heater activation.

The phenomena were then investigated in the identified facilities by simulating postulated severe accidents in a LWR with core degradation and release of hydrogen. The cooler and spray activation both led to containment depressurisation, with the spray displaying a faster rate and more profound effect on gas species mixing versus the limited effect of the cooler.

In another series of experiments, the heater tests revealed that the convection brought by the heat release resulted in a mixing effect above the heater inlet, while mixing below it was controlled by diffusion and thermal effects. In parallel modelling of thermal radiation helped improve the accuracy related to reproducing other variables and improved simulations.

The two-step pre-test and post-test analysis yielded considerable insight into modelling spray, cooler and heater phenomena, providing valuable information for tightening safety codes. The joint project ultimately extended pivotal recommendations for LWR containment and related safety codes for mitigating the effects in case of severe accidents involving nuclear power plants.

Related information


Nuclear Fission


Light-water reactor, LWR, ERCOSAM, accident management, SAMARA, stratification, coolant
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