CHAPTER 7: VERIFICATION AND VALIDATION

Verification and validation

Verification and validation processes should assess the technical accuracy and adequacy of the accident management guidance to the extent possible, as well as the ability of personnel to follow and implement this guidance. The verification process should confirm the compatibility of the guidance with the referenced equipment, user aids and supplies (e.g. non-permanent equipment, posted job aids, computational aids). The validation process should demonstrate that the necessary instructions are provided to implement the guidance.

The staff involved in the validation of accident management guidance should be different from those who developed the guidance. Developers and writers of plant specific accident management guidance should prepare appropriate tests and scenarios for validation, and their participation as observers to the validation process may be beneficial.

The findings and insights from the verification and validation processes, including consideration of positive and negative consequences of actions, should be documented. This information should be used to provide feedback to the developers of procedures and guidelines for any necessary updates before the documents are brought into force by the management of the operating organization. The documentation should be stored appropriately to enable any future revalidation.

Guidance should be prepared for testing the permanent and non-permanent equipment and for testing any assembled subsystems necessary for the equipment to meet its planned performance. The frequency and type of testing should be conducted in accordance with the manufacturer’s recommendations. Tests should address necessary local actions, contingencies, the proper connection of non-permanent equipment to plant equipment, access to the site, off-site actions, emergency lighting and the possibility of events affecting multiple units, as well as the time needed to implement these actions, if appropriate. Accident management guidance should be provided for maintenance and periodic testing to ensure the proper functioning of equipment and may include the need for plant walkdowns.

Validation tests should address the organizational aspects of severe accident management, especially the roles of the evaluators and decision makers, including the staff in the main control room and in the technical support centre.

Validation should be performed under conditions that realistically simulate the conditions present during an emergency and should include simulation of other response actions, hazardous work conditions, time constraints and stress. Special attention should be paid to the use of portable and mobile equipment, when such use is considered, and for multiple unit sites, to the practicality of using backup equipment that could be provided by other units.

A cross-functional safety review of the plant should be performed with the objective of fully understanding all implications of severe accident management. This review should incorporate a plant walkdown to assess the difficulties associated with the practical implementation of severe accident management measures in the event of internal or external hazards.

Changes made to procedures and guidelines should be re-evaluated and revalidated on a periodic basis to maintain the adequacy of the severe accident management programme.

Plant specific verification and validation are further described in Module 4, which contains the plant-specific organisation and implementation matters.

Further information on verification and validation is in SSG-54 paragraphs 2.56 to 2.59 and 3.61 to 3.68

In addition, the following report contains a detailed discussion on verification, validation and use of simulation tools in the development, verification and validation of SAMG: Nuclear Safety NEA/CSNI/R(2017)