inside and outside nuclear power plant design

According to Article 10 of Circular No. 30/2012/TT-BKHCN of the Ministry of Science and Technology of Vietnam, the conditions for identifying design basis accidents are derived from the postulated initiating events for the purpose of establishing the boundary conditions for the nuclear power plant. Using the design basis accident conditions to identify the design basis of the safety system and the items important to safety aiming to bring the nuclear power plant back to the safe state and mitigating the consequences of the accidents that might occur.

When a design basis accident occurs, the key plant parameters must not exceed the specified design limits. The analysis of the design basis accidents must take due account of certain failures in safety systems, the errors of design criteria, the use of postulations, models, and input parameters.

Besides, according to Article 11 of Circular No. 30/2012/TT-BKHCN, the conditions for identifying beyond design basis accidents are derived on the basis of engineering judgment, deterministic assessments, and probabilistic assessments. The analysis undertaken shall include identification of the features that are designed for preventing beyond design basis accidents and mitigating their consequences if they do occur. These features must:

- Be independent, especially for more frequent accidents;

- Capable of performing in the conditions pertaining to beyond design basis accidents and severe accidents;

- Have reliability commensurate with the intended functions;

- The features of containment must be able to withstand extreme scenarios, including the melting of the reactor core.

The possibility of significant releases of radioactive materials upon the occurrence of a beyond design basis accident must be minimized. When radioactive releases occur, it is necessary to take measures for spatially and temporally limiting the releases in order to protect the public, and sufficient time shall be made available for implementing these measures

If the results of the engineering judgments, deterministic safety assessments, and probabilistic safety assessments indicate that combinations of events could lead to abnormal operation or accidents, such combination shall be considered design basis accidents or part of beyond design basis accidents. Such combinations shall be considered part of the original postulated initiating events.

View details at Circular No. 30/2012/TT-BKHCN of the Ministry of Science and Technology of Vietnam, effective from February 11, 2013.

Le Vy

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