Statistics of meteorology for dose evaluation of crews of nuclear ship

For the purpose of the dose evaluation of crews of a nuclear ship, the statistics of wind speed and direction relative to the ship is discussed, using wind data which are reported from ships crusing sea around Japan Island. The analysis on the data shows that the occurrence frequency of wind speed can be fitted with the γ-distribution having parameter p around 3 and wind direction frequency can be treated as a uniform distribution. Using these distributions and taking the ship speed u₃ and the long-term mean speed of natural wind anti u as constant parameters, frequency distribution of wind speed and direction relative to the ship was calculated and statistical quantities necessary for dose evaluation were obtained in the way similar to the procedure for reactor sites on land. The 97% value of wind speed u₉₇, which should be used in the dose evaluation for accidental releases may give conservative doses, if it is evaluated as follows, u₉₇ = 0.64 u_s in the cases u_s > anti u, and u₉₇ = 0.86 anti u in the cases u_s < anti u including u sub(s) = 0. (author)