Containment chemistry during severe reactor accidents

During severe reactor accidents, the containment chemistry is important for the release of radionuclides to the environment. In some cases, cable pyrolysis may cause low pH values in the containment due to release of HCl and H2SO4. The program PYROCORE has been developed to simulate such events. From the results one is able to estimate the pH values and speciation in the containment. The results show that the vapor pressures of iodine compounds vary by many orders of magnitude during the first 24 hours of the accident. Most important among the findings is that the redox potentials are far more important than the pH values for control of iodine vapor pressures. Typically, the activity may reach a maximum of 1011 Bq/m3 a couple of hours after the initiation of the accident, to drop to a negligible value after a few hours. (author)