Occupational Exposures at Nuclear Power Plants, 1969--1993: ISOE Report

Abstract

The Nuclear Energy Agency of the Organisation for Economic Cooperation and Development has set up an information system on occupational exposure (ISOE) received at nuclear power stations throughout the world. The third annual report produced by NEA on the data held on ISOE has recently been published. Data from 16 countries are included in the report, mainly from OECD countries, but some non-OECD countries are included through membership of IAEA, which is a co-sponsor of ISOE. The 1993 data are analysed and trends are given for the period 1969 to the end of 1993. At the end of 1993, data for 339 reactors were included in the database, which represents 78% of the operating reactors in the world. About half of these supplied data directly to ISOE, and other data for the report were obtained from annual reports produced by the utilities. The data are well presented, mainly in tabular and graphical form. The ISOE information system consists of three databases: NEA 1, NEA 2 and NEA 3. NEA 1 contains radiological data in the form of collective dose, and individual dose distributions, which can be analysed by country or type of reactor; these data are the main source of information for this report. However, only collective dose is analysed in the report and not individual dose data. NEA 2 includes information on dose control techniques and work management, whereas NEA 3 contains details of specific operations and experience gained in radiation protection procedures. All three databases are to be developed further. The total collective dose from all reactors in 1993 was 585 man Sv, which was 6% less than in 1992. This fall is a continuation of a steady reduction since the mid-1980s, there being a maximum of 913 man Sv in 1983. That peak was mainly caused by back-fitting work in PWR reactors required after the Three Mile Island incident. In recent years also, increased emphasis on dose minimisation has gradually reduced the annual collective dose. The collective dose per unit power generated in 1993 was 0.32 man Sv per Tw h; this is the lowest value achieved in any year for utilities on the database. The report gives other analyses such as average outage period for refuelling: Finland was lowest with an average of 2 to 3 weeks and Japan was the highest at around 20 weeks. The penultimate chapter gives brief reports from each participating country on the principal events that affected the collective dose in 1993, and shows how multifarious are the influences on this quantity from various plant operations. These national reports also demonstrate how universal is the drive towards minimising occupational exposure.

Validation of the neural network for 3D photon radiation field reconstruction under various source distributions

“…Before workers are allowed to enter a radiation operation space, the three-dimensional (3D) radiation field in the entire work space is typically defined. The geometry model, combined with the computer-calculated simulated worker dose exposure information, can then be used to determine the radiation dose of the workers that can be quantitatively gained before the work commences (Hughes, 1996). This is pertinent for reducing the radiation damage received by the workers during the actual operation process to create a safe working environment.…”