Severe accident management measures for a generic German PWR. Part II: Small-break loss-of-coolant accident

The simulations show, that mobile pump injection significantly reduces the amount of the released fission products and hydrogen, if it is started within 75 min after the core exit temperature (CET) exceeded 400 °C. Without PSD, melting of the fuel can be prevented if the mobile pump is started immediately when CET > 650 °C, but release of fission products can only be prevented if early pump injection is combined with PSD. Cases with a delay of mobile pump injection in combination with a delay of PSD (e.g. due to temporary malfunction) are also investigated: until 50 min after CET > 400 °C a lower release of fission products and longer grace times to prevent melt relocation to the lower head are observed (compared to immediate PSD at CET > 400 °C).