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The general conference on weights and measures in June 1975 introduced the new names of units, the Gray (for ionizing radiations) and the Becqerel (for activity of a radioactive substance), on an international level. The reasons for this change--the units hitherto valid are the Rad and the Curie--and the international efforts at durability of the new regulations are reported.
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The Fort St. Vrain Nuclear Generating Station was a one-of-its-kind High Temperature Gas Cooled Reactor located near Denver, CO. Due to operational difficulties, the reactor was permanently shut down in August 1989. Plants to ship the spent reactor fuel to Idaho were thwarted by the Governor of Idaho. The inability to ship the spent reactor fuel offsite necessitated the construction of an Independent Spent Fuel Storage Installation (ISFSI) in order to proceed with the decommissioning of the reactor. After loading the ISFSI, decommissioning of the reactor was initiated and successfully completed. At the same time, the site was repowered using natural gas. As part of a settlement with the owner of the reactor, the U.S. Department of Energy agreed to take title to the spent fuel in the ISFSI and obtain an NRC license for the facility. The license for the ISFSI was transferred to the DOE in June 1999. Day-to-day operations of the ISFSI are accomplished by the DOE's Maintenance and Operations contractor, Bechtel Babcock Wilcox Idaho (BBWI). BBWI also operates the Three Mile Island Unit 2 ISFSI in Idaho for the DOE. This paradigm for ISFSI operations has been highly successful and is expandable to additional ISFSIs that may come under the jurisdiction of the DOE.
The Advanced Characterization System (ACS) uses readily available commercial radiation Environmental Restoration Contractor (ERC) detection and measurement equipment in a complementary staged system to locate and identity contamination in structures, systems and land area at Hanford's Environmental Restoration Contractor work sites. Large structures, such as former plutonium production reactors and separations facilities, are thoroughly and comprehensively characterized, not only for decontamination and decommissioning (D&D), but also for disposal and/or release. The ACS uses gamma-ray imaging instruments, in situ gamma spectrometry and large-area data-logging contamination survey meters to generate sufficient quality data to make operational and release decisions. The system is also used to safely characterize in-place systems without violating any containment and to localize activity in unusual situations.
The Gulf Nuclear Superfund Site located in Odessa, Texas, was an abandoned radioactive source production facility slated for cleanup as a Removal Action under the U.S. Environmental Protection Agency Region VI Superfund program. Prior to cessation of operations and abandonment of the facility in 1992, it was used for the production of radioactive sources used in the oil and gas industry and nuclear medicine applications. Pangea Group was contracted by the U.S. Army Corps of Engineers (USACE) Kansas City District to perform remediation of the site and other contaminated debris, cleaning of interior building surfaces, building demolition, and excavation/removal of contaminated soils and septic system. The project scope also included loading, containerization and transportation of low-level radioactive wastes for offsite disposal. Primary radionuclides present at the facility were 137Cs, 60Co, and 241Am. The project also included packaging and removal of radioactive sources and mixed waste consisting of radiologically contaminated lead shot and lead source containers. Included in the paper is a discussion of primary worker protection and environmental protection measures employed on the project. Worker protection issues included the control of industrial and construction safety hazards as well as control of external and internal radiation dose. Control of air emissions and contaminated wastewater were also very important, especially due to the location of the site. The site was located in an area containing both residential and commercial properties. Several residences and businesses were located immediately adjacent to the site. The project involved the participation of the USACE Kansas City District, EPA Region 6, and the Texas Bureau of Radiological Health. Field work on the project started in April 2001 and was completed approximately five months later.
Current regulations for unrestricted release are based on annual dose equivalent. Unless one desires to use very conservative "screening levels," dose modeling must be accomplished to derive an areal or volumetric limit or concentration value for release purposes. Such derived limits are referred to as "Derived Concentration Guideline Levels" (DCGL). This paper describes the process employed to derive DCGLs for building surfaces contaminated with uranium and its decay progeny based on annual dose equivalent and the innovative means employed during the derivation.
Hanford's N-Reactor operated from 1963 to 1987 generating approximately 9 x 10(7) m3 of radioactive and hazardous liquid effluent as a result of reactor operations. Two liquid waste disposal sites, essentially large trenches designed to filter contaminants from the water as it percolates through the soil column, were established to dispose of the effluent. The discharges to the sites included cooling water from the reactor primary, spent fuel storage, and periphery systems, along with miscellaneous drainage from reactor support facilities. Today, both sites are classified as Treatment Storage and Disposal Facilities under the Resource Conservation and Recovery Act of 1976, which makes them priority sites for remediation. The two sites cover approximately 4,100 m2 and 9,300 m2, respectively. Remediation of the sites requires removing a combined total of approximately 2.6 x 10(8) kg of contaminated soil and debris. Principal radionuclides contained in the soil/debris are 60Co, 137Cs, 239Pu, and 90Sr. Remediation of these waste sites requires demolishing concrete structures and excavating, hauling, and disposing of contaminated soils in work areas containing high levels of contamination and whole body dose rates in excess of 1 mSv h-1. The work presents unique radiological control challenges, such as minimizing external dose to workers in a constantly changing outdoor work environment, maintaining contamination control during removal of a water distribution trough filled with highly contaminated sludge, and minimizing outdoor airborne contamination during size reduction of highly contaminated pipelines. Through innovative approaches to dose reduction and contamination control, Hanford's Environmental Restoration Contractor has met the challenge, completing the first phase on schedule and with a total project exposure below the goal of 0.1 person-Sv.
In their recent Jupiter flybys Pioneer 10 and Pioneer 11 passed through a belt of intense particulate radiation. For Pioneer 10 the radiation dose on the craft's outer surface was at least 5 x 10(5) rads from electrons plus 1.0 x 10(6) rads from protons; the radiation dose inside the craft (0.3 cm aluminum) was approximately 4.5 x 10(5) rads. For Pioneer 11 the surface dose was at least 1.3 x 10(5) rads from electrons plus 3 x 10(5) rads from protons; the interior radiation dose was approximately 1.2 x 10(5) rads. Significant survival of microbial spores would be possible at these calculated doses; however, even the interior dose of Pioneer 11 would be lethal to man and most multicellular biological organisms.
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It is to be feared that the expansion of interventional radiology could lead to the reappearance of chronic radiodermatitis. Only a few studies mention the doses received by the hands, however these radiation doses are always high. Whereas clinical examinations lead to a belated diagnosis, capillary microscopy, a quick and non invasive test, enables to detect vascular injuries at the subclinical stage. Radiological protection is currently based on leaded gloves and on the reduction of exposure duration. Compensation for chronic radiodermatitis depends on the practitioner's status. In spite of a better evaluation of the overall irradiation, hand exposure remains a cause for concern. Capillary microscopy can provide appropriate medical surveillance.
Shortening scan time of CT scanner system has been evolved and increase in number of CT examinations has also been remarkable. This has been resulted from global recognition of usefulness of the CT examination, contrary to this merit, however, it is important to recognize the risk of x-ray exposure dose. Japan Industry Association of Radiological Systems (JIRA) in which CT manufacturers join has issued the concrete countermeasure and guidance for reduction in x-ray exposure dose in response to the ICRP90 Recommendation. Current CT scanner systems provide the data related to x-ray exposure dose such as CTDI(w) for setting CT scan parameters. To reduce x-ray exposure dose against infant patient, the scan parameters specified to infant patient (CT infant protocol) can be provided. Exposure dose by x-ray CT can be measured by the measurement method corresponding to IEC-60601-2-44 and by using phantom. CTDI measurement is made by CTDI(100) that measures in a range of 100mm for all slice thicknesses, and absorbed radiation dose is converted to that of air. Dose profile is measured by using multiple thermoluminescence dosimeter (TDL) chips. CT exposure dose data including CTDI(100) and Dose profile are well-defined, and Dose Information Guide conforming to IEC-60601-2-44 is provided to user for the purpose of reducing x-ray exposure dose. Studies by low dose (2.5 approximately 3mA) simulation for the purpose of reducing x-ray exposure dose in screening CT examination of lung cancer and development of ROI scan to reduce x-ray exposure dose in puncture under CT fluoroscopy have also been conducted.
"The radiation protection measures from equipment side, from a maker's point of view."TAKAJI SAITO Medical Solutions Marketing Division, Siemens-Asahi Medical Technologies Ltd. Taking care of limited fluoro and acquisition time during every case is an important prerequisite for dose reduction. Latest technology provides us with a number of means for dose savings regarding patients and staff. Here, the practical techniques of the radiation control function in angiography system are addressed. Last Image Hold (LIH). Collimation without radiation on LIH. Pulsed fluoroscopy at high and low rates. Additional spectral filters in the X-ray beam. Display of applied dose during the procedure These technological measures will definitely contribute for dose reduction for interventional procedures.
Several recent studies have a questionnaire survey of many hospitals regarding the radiation exposure conditions of X-ray examinations. From the survey result the entrance surface doses (first quartile, median, third quartile and mean values) have calculated by using the Numerical Dose Determination (NDD) method. The calculated result for all types of examinations showed that the median values were lower than the mean values, whereas the median values of the results were lower than those in the NRPB 21 in England. The mean values of the results were lower than those in the NRPB 21 in England. The mean values were lower than IAEA guidance levels. The results have indicated that the medical exposure dose (entrance surface dose) is lower with Computed Radiography (CR) than with the Screen/Film (S/F) system except the case of chest radiography. In the case of chest radiography (adult patients) by CR exposure set-up using a lower voltage and high mAs than the S?F method, the entrance surface doses were 150 % of the median value for the overall examination and 160 % of the median value for orthochromatic S/F systems. A difference in patient dose among hospitals using CR system was also found. Mean entrance surface dose in CR system was 0.12 mGy in a quartile, 0.19 mGy in the middle and 0.27 mGy in the third quartile. Among the hospitals that showed higher doses of third quartile than above mentioned, dose differences of a quartile were distributed 2 to 10 times higher than mean exposure doses. Mori et al. propose guidance levels are lower than IAEA guidance levels of entrance surface doses for examinations carried out in Japanese institutions as the 3rd quartile of the dose distributions. Therefore the quality control of tube voltage, tube current and mAs and a regular measurement of exposure for X-ray units are required.
Numerous investigations have confirmed the occurrence of various biological effects evoked in humans by pulse microwave radiation emitted from radars or cellular phones. In such exposures, the electromagnetic energy may reach very high values of power density in peak at relatively low time-averaged levels of power density. Up till now, no one has evidenced that the relationship between radiation dose and biological effects has the same correlation function for weak field as well as for a very strong field in peak. The proposed exposure levels of pulse-modulated electromagnetic fields (Smax pulse) for the general and occupational populations are described.
In personal communication, the mobile phone systems have developed most rapidly. To enlarge the area of mobile phone availability one needs to fine a base antenna network. This means that the base antennas are closer and closer to people. Each antenna is the source of electromagnetic fields, and thus it has to be designed carefully with respect to public health. The standards are different for the general public and for occupational groups. In Polish standards, the limits for the frequency range of 0.3-300 GHz are expressed in power density with value of 0.1 W/m2. The EU standards are more sophisticated as they relate limit values to frequencies. This paper presents these values and other limits binding in the EU countries. Other limits are laid down for the population of workers. In this respect, there is a considerable discrepancy between the Polish and EU standards. The approach to standard setting is quite different. The Polish standards are exactly determined and very restrictive. They require from operators to take great care in establishing new base stations. The question whether the Polish standards should be compatible with the European Union standards remains still open. The EU regulations do not require any change in the standardization of member states if their standards prove to be more restrictive. From 1998, a tendency towards more restrictive limits, especially in respect to the general population, has been observed.
A critical review of protection regulations (or their proposals) on work safety regarding electromagnetic fields as well as the general public protection against unwanted exposure to the fields are presented in this paper. The standards of the Western World are illogical in both aspects, biomedical knowledge and technical. The results (permissible exposures) are defined more precisely than the input data. In Poland, two independent acts are in force: one on occupational exposures and the other on non-occupational exposures. The former is "a world-better", but requires to be immediately changed to a standard that is applicable and friendly to its users. The latter can be accepted after introducing several amendments. The enlargement of the environmental standard to include occupational issues may create a good Polish proposal also useful at the international level.
NASA is developing the knowledge required to accurately predict and to efficiently manage radiation risk in space. The strategy employed has three research components: (1) ground-based simulation of space radiation components to develop a science-based understanding of radiation risk; (2) space-based measurements of the radiation environment on planetary surfaces and interplanetary space, as well as use of space platforms to validate predictions; and, (3) implementation of countermeasures to mitigate risk. NASA intends to significantly expand its support of ground-based radiation research in line with completion of the Booster Applications Facility at Brookhaven National Laboratory, expected in summer of 2003. A joint research solicitation with the Department of Energy is under way and other interagency collaborations are being considered. In addition, a Space Radiation Initiative has been submitted by the Administration to Congress that would provide answers to most questions related to the International Space Station within the next 10 years.
In its 1990 Recommendations, the ICRP indicated that it believed that the standards of environmental control needed to protect man to the degree currently thought desirable would ensure that other species are not put at risk. The ICRP considers that its system of radiological protection has provided a fairly good indirect protection of the human habitat. However, no internationally agreed criteria or policies explicitly address protection of the environment from ionising radiation, and it is difficult to determine or demonstrate whether or not the environment is adequately protected from potential impacts of radiation under different circumstances. The present report suggests a framework, based on scientific and ethical-philosophical principles, by which a policy for the protection of non-human species could be achieved. The primary purpose of developing such a framework is to fill a conceptual gap in radiological protection; it does not reflect any particular concern over environmental radiation hazards. The proposed framework is designed to harmonise with the ICRP's approach to the protection of human beings, but does not intend to set regulatory standards. Instead, the proposed framework is intended to be a practical tool to provide high-level advice and guidance for regulators and operators. An agreed set of quantities and units, a set of reference dose models, reference dose-per-unit-intake (or unit exposure), and reference fauna and flora are required to serve as a basis for the more fundamental understanding and interpretation of the relationships between exposure and dose and between dose and certain categories of effect, for a few, clearly defined types of animals and plants. As a first step, a small set of reference fauna and flora with supporting databases will be developed by the ICRP. Others can then develop more area- and situation-specific approaches to assess and manage risks to non-human species.