Selection of SAMG Programme

At the beginning of the programme, various decisions must be made about the SAMG programme to be implemented:
- Use of a more procedural type approach, i.e. formulate deliberations and actions close to the existing EOPs, e.g. expand these into the severe accident domain.- This is done at only a few plants-
- Use of a more guidance type approach, i.e. a more flexible approach, as guidelines allow deviations from prescribed paths, usually SAMG - This is the more common approach-
As discussed earlier, the guidance approach is preferable due to:
- Difficulties in evaluating the plant specific status, equipment availability and the use of this information to develop a recovery strategy;
- Phenomenological uncertainties and the multitude of sequences of severe accidents.
The more procedural type approach must be, in general, based on a large number of pre-analysed scenarios. However, there is no guarantee that in case of unlikely event leading to a severe accident, the accident scenario will follow the one that was pre-analysed.
In addition to deciding whether to use the procedural or guidance type approach, the organisation will need to decide whether to use a generic SAMG program, developed by one of the NPP vendors, Owners Groups,
or a large utility operating many NPPs or alternatively use a plant-unique SAMG programme which includes the development of the Technical Basis for such programme.
Developing a plant-unique programme for a particular plant can be extremely complicated, as the full Technical Basis (e.g. comprehensive insights needed to understand the plant behaviour in a severe accident,
including the plant response to SAMG actions) must be developed. Very few plants - A well-known example is Loviisa NPP in Finland, VVER-440 - have done this so far, and where it was done it took many years
to formulate and execute the experimental programme. Because of the additional efforts needed to develop a full technical basis, the plant-unique programme can be very costly.
A SAMG programme should be selected that includes guidance for mitigation of accident occurring at low-power and shutdown states and the spent fuel pool accident, or one from which such guidance can be developed by plant staff
– However, the choice of the SAMG programme should not exclusively depend on the presence of a generic programme for low-power and shutdown SAMG.
Whatever the choice is, the SAMG programme should be based on observed parameters and symptoms and should not require recognition of the underlying scenario.
It should also be kept in mind that the focus of the SAMG programme is not to preserve the reactor core or spent fuel integrity, but to preserve the remaining intact fission product barriers or to delay their failure,
as well as to mitigate releases.
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