To ensure safety of nuclear power plants in Vietnam when there are postulated initiating events

To ensure safety of nuclear power plants in Vietnam when there are postulated initiating events (Internet image)

Article 8 of Circular 30/2012/TT-BKHCN stipulates requirements to ensure safety of nuclear power plants in Vietnam when there are postulated initiating events as follows:

- A systematic approach shall be adopted to identify all postulated initiating events that could result in serious consequences, and the postulated initiating events with a significant frequency of occurrence. These events must be considered in the design.

- The postulated initiating events shall be identified based on the basis of engineering judgment, and a combination of deterministic and probabilistic assessments. The A justification of the extent of usage of deterministic safety analysis and probabilistic safety analysis shall be provided to ensure the adequacy of the list of foreseeable accidents.

- An analysis of the postulated initiating events for the plant shall be made to establish the preventive measures and protective measures that are necessary to ensure the fulfillment of safety functions.

- When a postulated initiating event occurs, the conditions below must be satisfied in the following order of priority:

+ The event does not produce significant effects on the safety, or only causes a change that the safety conditions are able to be automatically restored due to the inherent features of the nuclear power plant;

+ After the event, the nuclear power plant would return to the safe state by means of to the passive safety features or the capability to operate continuously of the systems that control the postulated initiating event;

+ After the event, the nuclear power plant would return to the safe state due to the actuation of safety systems;

+ After the event, the nuclear power plant would return to the safe state due to the implementation of specified processes.

- An engineering judgment shall be provided for excluding from the design the initiating events not in the list of postulated initiating events.

- Where prompt and reliable action would be necessary, the automatic actuation of safety systems must be designed to prevent the postulated initiating events from escalating into more severe conditions. Where prompt response would not be necessary, the safety system is activated manually, or the operator may take actions instead of activating the safety system, the following requirements must be satisfied:

+ The administrative, operational, and emergency procedures shall be adequately specified;

+ An assessment of the potential for an operator to worsen an event through incorrect diagnosis of the necessary recovery process or erroneous operation of equipment shall be made in order to provide suitable solutions;

+ Any equipment necessary for manual response and the recovery processes shall be placed at most suitable locations to ensure its availability at the time of need, and allow safe access to such equipment under the environmental conditions anticipated.

- The equipment and procedures necessary for keeping control over the whole nuclear power plant and mitigating the consequences under of a loss of control shall be provided.

More details can be found in Circular 30/2012/TT-BKHCN, which comes into force from February 11, 2013.  

Le Vy

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