**4.1. Introduction**

132 Nuclear Power – Practical Aspects

formula (1):

considerations are necessary.

with

material.

the safety distances according to the BMI guideline [18] are fulfilled, based on the

R = safety distance (in m) of the place where the explosive gas is handled from to the

It should be noticed that the total mass to be assumed depends on the type of explosive

For the case that the prerequisites of this prescribed check are met, no further probabilistic

**Figure 4.** Pressure behaviour at the building for a single pressure wave according to [18]

0 100 200

regarding explosion pressure waves as presented in Table 1 (see [19]).

Criterion 1: Occurrence frequency <1E-05 per year Criterion 2: Classes A and C are designed according

**Table 1.** The graded process of analysing explosion pressure waves

to load assumptions and safety distances determined in length lR according to [18]

0,30

0,45

Criterion 1: Not fulfilled Criterion 2: Fulfilled

Criterion 1: Not fulfilled Criterion 2: Not fulfilled

**Criteria Extent of analysis**

Otherwise the procedure has to be in accordance with the graded process of evidence

check

required

respective plant which should be larger than 100 m, and L = assumed mass of the explosive material (in kg).

1/3 *R L* 8 (1)

Verification using the prescribed

Detailed probabilistic safety analysis

Conservative estimation of occurrence frequency

The German PSA document on methods [3] describes the approaches to be used in the probabilistic safety assessment which have to be performed in the frame of comprehensive safety reviews of nuclear power plants.

One part of this approach is dedicated to the screening process already explained in section 2, the further parts of this document deal in more detail with the occurrence frequency of explosion pressure waves taking into account the site-specific situation, sources of possible explosion pressure waves in the surrounding of the plant, and the procedure for the calculation of occurrence frequencies of accidents during transportation of explosive material by ships, trains or trucks and of accidents of stationary plants near the plant under consideration.
