Frequency and extent of surveillance

FREQUENCY AND EXTENT OF SURVEILLANCE Determination of the frequency and extent of surveillance 

The frequency and extent of the surveillance of individual SSCs should be determined primarily on the basis of their relative importance to safety. Access limitations and the requirement to keep radiation doses to personnel as low as reasonably achievable should also be taken into account 

The frequency and extent of surveillance should be adequate to fulfil the following functions  

In using calculated reliability figures to determine the surveillance frequency, 

The reliability of SSCs may be adversely affected by an excessive number of thermal, mechanical or other cycles. To reduce cycling caused by testing, the testing of components that provide a given safety function may be suspended during periods in which that particnlar fnnction is not required to be available, provided that the surveillance reqnirements are met before any change in the operational state is made that reqnires the respective safety function to be available. 

---

Not all SSCs require the same frequency and extent of surveillance. The use of quality assurance principles enables the surveillance requirements to be derived in a graded manner such that the extent of the requirements is consistent with the safety functions performed by the SSCs. Account should be taken of the probability of failure to perform properly (PSA results can be used if applicable) and of the requirement to maintain radiation exposures as low as reasonably achievable. The frequency with which SSCs not normally in use are tested should be optimized, so that they can perform their functions satisfactorily when required and possible wear-out due to overtesting is avoided. In deciding on the extent of the surveillance requirements, systems may be classified in accordance with their importance to safety. 

The established frequency and extent of surveillance should be periodically reevaluated to verify that they are effective in maintaining the SSCs in an operational state. Where appropriate, PSA based methods can be used to optimize surveillance. Procedures should be established for ensuring that these re-evaluations are carried out and that any necessary changes are approved by the appropriate authorities. In these re-evaluations, the following points should be considered ... 

---