5.1. In order to demonstrate that the containment systems meet design and safety requirements, commissioning and in-service tests and inspections should be conducted as outlined in the following.

COMMISSIONING TESTS

5.2. Commissioning tests for the containment should be carried out prior to the first criticality of the reactor to demonstrate the containment’s structural integrity, to determine the leak rate of the containment envelope and to confirm the functioning of related equipment.

Structural integrity test

5.3. A pressure test should be conducted to demonstrate the structural integrity of all parts of the containment envelope (including extensions and penetrations) and of the containment systems. If the containment structure comprises two containment walls that are both subject to pressure loads, both walls should be tested.

5.4. The pressure test should be conducted at a specified pressure for which account is taken of the applicable codes for the material used, and which is at least the design pressure. The value of the test temperature should not be close to the ductile-brittle transition temperature for the metallic material.

5.5. A leak test should be conducted following the structural integrity test to demonstrate that the leak rate of the containment envelope does not exceed the specified maximum leak rate. The test should be conducted with the components of the containment in a state representative of the conditions that would prevail following an accident, to demonstrate that the specified leak rate would not be exceeded under such conditions.

5.6. To establish a point of reference for future in-service leak tests, the leak test performed during commissioning should be conducted at a test pressure or pressures consistent with the pressure selected for in-service leak tests:

(a) At values of pressures between the pressure selected for in-service leak testing and the positive design pressure, if the in-service tests are to be conducted at a pressure lower than the design pressure; or

(b) At the design pressure of the containment, if the in-service tests are to be conducted at this pressure.

5.7. The need to validate the leak rate assumed in the safety analysis reliably over the entire plant operating lifetime for the entire range of pressures calculated should be taken into consideration in the choice of test pressure(s).

5.8. The need for initial and periodic testing should be considered in the design, and all the components that might be damaged during testing should be identified. The necessary means to pressurize and depressurize the containment and appropriate instrumentation for testing should be included in the design.

5.9. One way of determining leak rates is the absolute pressure method, in which the leakage flow is determined by measuring the decrease in pressure as a function of time. In this method, the temperature and pressure of the containment atmosphere, the external atmospheric temperature and pressure, and the humidity of the containment atmosphere should be measured continuously and factored into the evaluation. Means should be provided to ensure that the temperature and humidity of the containment atmosphere are uniform.

5.10. Appropriate instrumentation should be provided in the containment, appropriately positioned and installed either permanently or as needed, to

5.11. For double wall containments, one way to determine the direct leak rate from the containment to the environment (i. e. if the leaked water or gas does not collect in the annular space between the inner and the outer containment walls) is by calculation. This calculation should determine the difference between (a) the total leak rate from the inner containment as determined by the leak test for the inner containment (this consists of both flow from the inner containment into the annulus and flow from the inner containment to the atmosphere) and (b) the leak rate from the inner containment wall to the annulus, obtained after ventilation of the annulus has been stopped (this is typically calculated by subtracting the normal flow out of the annulus vent from the flow out of the annulus vent during the leak test).