Precipitation issue of airborne radioactive substance in pipeline of sampling system

This paper presents an issue of the precipitation in sampling system pipeline of airborne radioactive substances, radioactive gases and aerosols, from nuclear facility effluents. The precipitation of radioactive substances in sampling pipeline could cause the actual concentrations to be underestimated with inadequate representative of sample, whereas, in the case of aerosol particles, the re-suspension of precipitating particles would lead, in some circumstances, to an overestimation of actual aerosol concentrations, also with less representative. The author of this paper, working with EIAs management in the NEPA over the recent several years, has a serious awareness of the imminency of addressing this problem. However there still exist a number of confusing concepts among the designers and/or operators of nuclear facilities. The purpose of the present paper is to bring this problem to the attention of the parts concerned to the in-pipeline precipitation of airborne radioactive substances and, in particular, of aerosol particles, so as to be put into study. (author)