4.152. Many containment designs include systems to recirculate water from collection points inside the containment envelope, either through heat exchangers or directly, for reinjection into the reactor vessel or into the containment spray system in an accident. Parts of these recirculation systems may be located outside the containment envelope, giving rise to a potential for leakage of radionuclides from pumps, valves or heat exchangers outside the containment envelope. Where a design of this type is used, provisions should be made to minimize the uncontrolled release of radionuclides to the environment resulting from such leakage, to test the leak rate periodically, and to detect and isolate accidental leaks by qualified means.

Control of leakage in buildings outside the containment

4.153. In buildings outside the containment, sources of radioactive material arising from leaks from the containment in accident conditions or from radioactive material stored in the buildings should also be confined.

4.154. In establishing the design basis for these buildings, consideration should be given to all possible events of both internal and external origin that could cause the release of radioactive material to the environment.

4.155. Design measures such as subdividing the buildings into compartments and ensuring adequate leaktightness should be adopted to minimize the dispersion of radioactive material inside the buildings. A filtered ventilation system should be provided to limit and control the release of radioactive material to the environment.