EXPOSURE LEVELS FOR PERSONS INVOLVED IN RECOVERY OPERATIONS AFTER THECHERNOBYL ACCIDENT - STATISTICAL-ANALYSIS BASED ON THE DATA OF THE RUSSIAN NATIONAL MEDICAL AND DOSIMETRIC REGISTRY (RNMDR)

We present a detailed description of dosimetric data entered in the Ru ssian National Medical and Dosimetric Registry (RNMDR) for emergency w orkers (liquidators) involved in recovery operations (RO) after the Ch ernobyl accident. The data on the absorbed doses from external exposur e are based on the documents given to liquidators by organizations tha t performed dosimetric monitoring in the zones of operation. Using the data on external doses currently available in the RNMDR for 119416 Li quidators (78.4% of the total number of 152 325 persons), different st atistical characteristics were derived to assess the reliability of th e information. The paper also discusses dose distributions according t o the date of beginning work in the RO zone up to 250 km from the Cher nobyl nuclear power plant (NPP)I, on the distance of the settlement wh ere the liquidators were accommodated or worked from the NPP, and on t he duration of their stay in the RO zone. To analyse the reliability o f the dosimetric data, the notion of an effective exposure dose rate ( EEDR), i.e. the ratio of the dose registered in RNMDR and the duration of stay in the RO zone, was introduced for each liquidator, and corre sponding statistical characteristics for the distribution of EEDR depe nding on the date of entry into the RO zone and distance from the plac e of residence or work to the NPP were obtained. The analysis for diff erent groups of liquidators shows that the dosimetric information of t he RNMDR is, as a statistical aggregate, generally consistent with the data on the radiation situation in the RO zones.