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PubMed1998

Potential environmental and regulatory implications of naturally occurring radioactive materials (NORM).

The immense volume of naturally occurring radioactive materials (NORM) wastes produced annually by extracting industries throughout the world deserves to come to the attention of international and national environmental protection agencies and regulatory bodies. Although a great deal of work has been done in the fields of radiation protection and remedial actions concerning uranium and other mines, the need to dispose of diffuse NORM wastes will have environmental and regulatory implications that thus far are not fully appreciated. NORM wastes constitute, by and large, unwanted byproducts of industrial activities as diverse as thorium and uranium milling, niobium, tin and gold mining extraction, water treatment, and the production of oil, gas, phosphate fertilizer, coal fire and aluminum. The volumes of NORM wastes produced annually could reach levels so high that the existing low level radioactive waste (LLRW) facilities would be readily occupied by NORM if controlled disposal procedures were not adopted. On the other hand, NORM cannot just be ignored as being below radiological concern (BRC) or lower than exempt concentration levels (ECLs), because sometimes NORM concentrations reach levels as high as 1 x 10(3) kBq/kg for 226Ra, and not much less for 228Ra. Unfortunately, thus far there is not enough information available concerning NORM wastes in key industries, though the international scientific community has been concerned, for a long time now, with technologically enhanced natural radiation exposures (TENRE). This article is written with the intention of examining, to the extent possible, the potential environmental and regulatory implications of NORM wastes being produced in selected industries.

Background Radiation↗
PubMed2000

Radiation doses to members of the public near to Sellafield, Cumbria, from liquid discharges 1952-98.

Liquid wastes containing low levels of radioactivity have been discharged to the Irish Sea from the nuclear fuel reprocessing site at Sellafield since operations began in the early 1950s, and monitoring of radioactivity in foodstuffs has been undertaken over many years. Based on the best available monitoring data, supplemented by modelled values where necessary, doses to local critical groups have been reassessed using the most recent dosimetry. Contemporary habits data have been used where available, again supplemented by assumed habits where necessary. During the 1950s and 1960s the highest doses were received by individuals consuming Cumbrian Porphyra as laverbread, and peak doses around 0.8 to 1.0 mSv year(-1) have been estimated. During the 1970s and 1980s the critical exposure group switched to consumers of local fish and shellfish, with peak doses possibly reaching 2.5 to 3.0 mSv year(-1). Latterly, doses to all marine-related groups have declined to less than 150 to 200 microSv year(-1). At all times, doses have been within the appropriate limits set for members of the public.

Environmental Exposure↗
PubMed2002

Thermoluminescence response of calcic bentonite subjected to conditions of high nuclear waste underground storage.

Bentonite is regarded as a backfilling material for underground storage facilities of highly radioactive nuclear waste built on granite formations. In these facilities, bentonite will be subjected to a gradient of temperature and dose rate, achieving a very high integrated dose and, therefore, changes in its structure and physical properties may take place. Two experiments to discriminate between the thermal and the irradiation effect were performed. In the first (named BIC 2A), samples were subjected to temperature while in the second (named BIC-2B) the combined effect of temperature and irradiation was studied. The experimental conditions were: a thermal gradient between 130 degrees C and 90 degrees C, a maximum dose rate of 3.5 kGy.h(-1) and a gradient of the integrated dose between 1.75 MGy and 10 MGy. Both experiments lasted a total of 124 days. An irradiation source of 60Co with an activity close to 300,000 Ci, and bentonite samples of 200 mm in length and 50 mm in diameter were used. After the experiment, the samples were ground and two fractions were obtained: a fine fraction (<2 microm) enriched in montmorillonite clay mineral and a coarse fraction (>80 microm). The results are described of thermoluminescence analyses on the two fractions obtained which showed that the coarse fraction can be 100 times more sensitive to radiation than the fine fraction. On the other hand, the heated and irradiated samples showed a thermoluminescence response around 50 times greater than the samples that were only heated. In addition to this, the temperature and dose rate conditions are relevant parameters in the generation and stabilisation of radiation induced defects. Finally, the response of samples heated and irradiated for two months was quite similar to that obtained on samples heated and irradiated for four months, indicating a saturation phenomenon.

Bentonite↗
PubMed2000

Dose reconstruction system for the exposed population living along the Techa River.

The Mayak Production Association, which began operation in 1948, was the first facility in the former Soviet Union for the production of plutonium. Significant worker and population exposure occurred as a result of failures in the technological processes in the late 1940's and early 1950's. Members of the public were exposed via discharge of about 1017 Bq of liquid wastes into the Techa River during 1949-1956, an explosion in the radioactive waste-storage facility in 1957, and gaseous aerosol releases within the first decades of the facility's operation. Residents of many villages downstream on the Techa River were exposed via a variety of pathways; the more significant included drinking of water from the river and external gamma exposure due to proximity to sediments and shoreline. The specific aim of this project is to enhance the reconstruction of external and internal radiation doses for individuals in the Extended Techa River Cohort. The purpose of this paper is to present the details of the methods that are being used in this enhanced dose-reconstruction effort and to provide example and representative results of the calculations. The methods of dose assessment currently being developed for the exposed population [termed the Techa River Dosimetry System-2000 (TRDS-2000)], which are a significant improvement on past methods (TRDS-1996), are presented. The new TRDS-2000 doses from the ingestion of radionuclides are substantially higher for the gastrointestinal tract, due to consideration of short-lived radionuclides. The TRDS-2000 doses from external exposure are substantially lower due to improvements in several factors. Assessment of uncertainty and validation of the "new" doses are significant issues currently under investigation.

Health Physics↗
PubMed1984

Optimum geometry of a large Marinelli-type vessel and its application to environmental aqueous samples.

In order to establish a system of monitoring radioactivity in waste water treatment plants, the optimum geometry of a large-volume Marinelli-type vessel with an 8% Ge(Li) detector was investigated, but optimum volume was not obtained. However, at a particular volume, the optimum geometry existed. The 30 L Marinelli-type vessel was applied to a system monitoring the influent and the return sludge at a waste water treatment plant in Tokyo.

Radiation Monitoring↗
PubMed1960

Avian uptake of fission products from an area contaminated by low-level atomic wastes.

Birds living on the Oak Ridge White Oak Lake bed, an area contaminated by low-level atomic wastes, revealed a striking seasonal difference in uptake of fission products. Because the omnivorous diet of passerine birds is ecologically comparable to the mixed diet of man, uptake of radionuclides by wild birds provides an assay of amounts to be expected at the trophic level of primary interest to man.

Animals↗