Comparison of two modern approaches for MBDA calculations of RBMK-type reactors

The paper presents the comparative study of modern approaches, i. e. “best-estimate” and “partially-conservative” for the accident analyses based on calculations of Maximum Design Basis Accident at the Ignalina Nuclear Power Plant. The calculated critical parameters, values of which lead to the determination of the safety margin, were compared for both analyses. The comparison of the results shows that these values for “best-estimate” calculation are slightly lower in comparison with “partially-conservative” calculation results. That enables to draw a conclusion that in most cases both approaches – either “best-estimate” or “partially-conservative” can be applied. The latter approach looks tempting since in this case only one calculation is sufficient; while in the case of the “best-estimate” approach a high number of calculations is required. Thus, the “partially-conservative” approach requires considerably less computational time. However, when using this methodology the obtained calculated results do not meet the acceptance criteria, the complete analysis by employing “best-estimate” approach is necessary.