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Determination of dosimetric burden to personnel of uranium mining enterprises.

#K-2322


Development of a methodology to determine dosimetric burden to the personnel of uranium mining enterprises

Tech Area / Field

  • ENV-EHS/Environmental Health and Safety/Environment

Status
3 Approved without Funding

Registration date
17.08.2016

Leading Institute
National Nuclear Center of the Republic of Kazakstan / Institute of Radiation Safety and Ecology, Kazakstan, Kurchatov

Collaborators

  • Forschungszentrum Jülich GmbH, Germany, Jülich

Project summary

According to the IAEA’s safety guidance [1] 1 mSv exceedance probability value of the committed effective dose by occupational exposure at annual radionuclide intake provides authority for monitoring. Control of occupational radiation is an essential part in personnel radiation safety assuarance system. Monitoring aims at reliable determination of exposure doses to personnel.

Internal irradiation control assumes particular importance if there is radionuclide intake probability into a body which takes place in the context of uranium mining enterprises.. This information is necessary as increased dosimetric burden are capable of causing irreversible processes in a human body, which without due attention of specialists may in the end result in serious diseases.

United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) published a report in 2000 [2] indicating possible approaches to control internal exposure doses to personnel. Three basic methods are suggested– air sampling in the working area, in-vitro biological material monitoring as well as internal in-vivo contamination measurements by means of whole-body counters.

The global practice currently most frequently uses air control in the working area and the indirect method of determining internal radionuclide concentration (in-vitro, 24-hour urine sample analysis) as control methods of internal radionuclide intake. In the context of uranium mining enterprises, uranium isotopes are determined in 24-hour urine samples. As a rule, concentration of radon daughters and uranium isotopes is determined in the air of the working area.

Air control of the working area has a number of shortcomings including necessary knowledge of the precise time an employee stays in the controlled area; inpidual protective equipment must be in good order and properly applied. Another air control method in the working area is using inpidual air samplers which are fastened directly next to в respiratory organs. By means of them one can assess radionuclide concentration in air directly inhaled by a worker. However, this method also requires information to know how well respiratory protection equipment «worked», how properly and if it was used at all. Thus, in either case, radionuclide intake is only assessed theoretically. Moreover, as practice shows, instead of inpidual samplers, uranium mining enterprises of developing countries (including those in Kazakhstan) use standard air control in the working area using which it is impossible to assess internal intakes determined by emergency situations: work solution spill, decontamination of contaminated areas, dust formation as a result of emergency situation and so on..

Using biophysical methods generally determines uranium concentration only, at that, probable internal intake of other radionuclides from 235,238U decay chains is ignored. At the same time 230Th and 226Ra dose factors are known to have the same order of magnitude as 235,238U dose factors. This is of prime importance at the uranium ore processing stage to chemical separation of uranium and its daughters.

All mentioned above gives reason to believe that internal exposure doses to personnel can be underrated. The problem can be solved by performing dosimetric cost monitoring for all the radionuclides in uranium decay chain taking into account reasonable assumptions regarding their behavior in the course of industrial processes. Besides, if monitoring is based on biophysical methods doses are calculated by actual internal radionuclide concentration rather than based on averaged values.

Methodology for the determination of internal exposure doses to personnel of uranium branch providing control of internal intake of all the dose forming radionuclides in 235, 238U decay chain using biophysicasl methods is planned to be developed within the framework of the Project.


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