CSA N288.2:19 Guidelines for calculating the radiological consequences to the public of a release of airborne radioactive material for nuclear reactor accidents.
4 Treatment of meteorology S Note: The types of consequence calculations and output quantities are determined by the treatment of meteorology. For this reason, Clause 4 includes both deterministic and probabilistic methods for dealing with meteorology. 4.1 Types of consequence calculations 4.1.1 The consequence calculation shall be either a a) deterministic calculation; or b) probabilistic calculation. 4.1.2 A deterministic calculation shall be defined as the calculation of the consequences of an accidental release using a single weather scenario. 4.1.3 A probabilistic calculation shall be defined as the calculation of the probability distribution of the consequences of accidents as a function of weather conditions. Notes: 1) In a probabilistic calculation, the dispersion and consequence calculations are repeated for a large number of weather scenarios and the consequences are organized in histogram form, showing frequency of observing a given range of consequences. These calculations are included in Level II probabilistic safety assessment (PSA). They are the last part of a chain of probabilistic methods used to analyze accidents. The potential applications of a Level II PSA are described in IAEA Technical Document 1200 and IAEA 50-P-12. 2) The method used to obtain weather scenarios applicable for a given site, and the method used to sample these weather scenarios, are important considerations when performing probabilistic calculations (see Clause 4.3). Once the calculation is completed, it is customary to summarize the histogram of consequence data using point estimates such as the average, median, and percentiles (value corresponding to a given cumulative probability level), or complementary cumulative distribution functions (CCDF).
Probabilistic calculations shall be employed where doses are required for mean individual risk
calculations where it is not necessary to know the identity of the individual, or for estimating collective
risks to a large population.
4.2 General requirements
4.2.1 Deterministic calculations Deterministic safety assessment
For deterministic safety assessments, the selected weather scenario shall be
a) conservative; and
b) limiting for the consequences of the chosen end point.CSA N288.2 pdf download.