1.95. Containment structures and appurtenances (penetrations, isolation systems, doors and hatches) should prevent unacceptable releases of radioactive material in the event of an accident. For this purpose, their structural integrity should be maintained (i. e. the structural functions of protection and support should be ensured), and it should be ensured that the leaktightness criteria are met (Ref. [1], paras 6.43-6.67).

1.96. In steel containments the load bearing and leaktightness functions are generally fulfilled by the steel structure. The metallic structure should be protected against missiles generated inside and outside the containment as a result of internal and external events that affect the plant.

1.97. All loads should be identified, quantified and properly combined in order to define the challenges to structures and components. This process should include the adoption of adequate safety margins (Ref. [1], para. 6.45).

1.98. Acceptance criteria in terms of stresses, deformations and leaktightness should be established for each load combination (Ref. [1], paras 6.48-6.50).

1.99. In choosing the design parameters and determining structural sizing, local stresses should be taken into consideration.

1.100. Design for a specific maximum leak rate is not a straightforward or purely quantitative process. A number of factors should normally be taken into account, including the limitation of stresses in accident conditions, the proper choice of components (e. g. isolation valves), the proper choice of sealing materials, limitation of the number of containment penetrations and control of the construction quality. Extant operational data, experience and practices should be used to the maximum extent practicable.

4.47. Provisions for commissioning tests and for in-service testing and inspection should be included in the design, so as to be able to demonstrate that the containment systems meet design and safety requirements.