The development of a simple high range skin dose rate meter using a silicon diode as a detector.
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Electrons↗
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Results for “RADIATION MONITORING”
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Experience with a sustained policy of radiation exposure control and research in a medical center.
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Cancer Care Facilities↗
Personnel dosimetry intercomparison studies at the Health Physics Research Reactor: a summary (1974-80).
Six personnel dosimetry intercomparison studies using the Health Physics Research Reactor at the Oak Ridge National Laboratory were conducted between 1974 and 1980. These studies allowed participants to test their neutron and gamma-ray dosimeters under a variety of mixed-field spectral conditions and to compare their results with those of others making measurements under identical conditions. Fifty-eight participant organizations, about half of which participated in more than one study, made approx. 2000 measurements of the neutron and gamma-dose-equivalent. Dose equivalents in the 0.1-12 mSv (i.e. 10-1200 mrem) range were determined for five different shielded reactor spectra using three basic types of dosimeters (thermoluminescent albedo, nuclear emulsion film and track etch) for neutron measurements and two basic types (film and thermoluminescent dosimeters) for the gamma-measurements. The data from the six studies are summarized, analyzed and explained. Intercomparison of the participants' results and consideration of reference dosimetry allows several conclusions to be made relative to the status of and trends in personnel neutron and gamma-ray dosimetry.
Film Dosimetry↗
Occupational exposure in the academic sector of the R.O.C.
This paper deals with occupational exposure in the academic sector of the Republic of China during the past two decades. The Tsing-Hua film badges were used for personnel monitoring. The radiation sources available in the research institutes and universities are listed and illustrated. The number, sex, age and per capita dose equivalent for the radiation workers in the past 21 yr are analyzed. The radioisotope production rate and the dose equivalent received by the workers are compared, and the results indicate that radiation protection has been greatly improved during last decade.
Academies and Institutes↗
Transportation of radioactive material in Georgia.
A 3-yr study of radioactive materials transportation examined the magnitude of radioactive materials shipments in terms of numbers of packages and motor vehicle trips and types of materials; compliance with regulations for packaging, labelling, handling, external radiation exposure, and surface contamination; and dose to workers as measured with personnel dosimeters. Much of the information was obtained at the Atlanta airport and its vicinity, a package distribution center for the southeastern U.S., and at the Barnwell, S.C. radioactive waste burial site, the destination of most shipments of radioactive waste from or through Georgia. Approximately 12,000 packages in radioactive material categories I, II and III were handled in Georgia each year. Motor vehicles made approximately 3300 trips per year. Some instances of noncompliance were observed, but few of them had the potential for elevated radiation exposure of persons. Several incidents associated with radioactive material transport are reported, of which one may have resulted in slightly elevated exposures to persons. Among drivers and handlers who worked with radioactive material shipments, dosimeters showed that less than one-half of them received radiation doses above background levels. The highest doses were found for drivers who transported large numbers of 99Mo generators.
Georgia↗
1976 Hanford americium exposure incident: decontamination and treatment facility.
An injured worker, contaminated with more than 6 mCi of 241Am required special treatment and housing for 4 months. This paper is a description of the design and management of the facility in which most of the treatment and housing occurred. The problems associated with contamination control, waste handling, supplies and radiological concerns during the two-stage transfer of the patient from a controlled situation to his normal living environment are discussed in detail.
Accidents, Occupational↗
A high sensitivity LiF thermoluminescent dosimeter--LiF(Mg, Cu, P).
This paper describes the dosimetric properties of a new, high-sensitivity thermoluminescence dosimeter material prepared in our laboratory. The sensitivity of the LiF(Mg, Cu, P) phosphor is about 23 times higher than that of LiF (TLD-100). Its TL response is linear from 0.3 mR to 1000 R. Its energy dependence is similar to that of LiF (TLD-100). It is stable and reusable without significant loss of sensitivity. Its application to environmental radiation monitoring is described.
Copper↗
Radiation transmission and scattering for medical linacs producing x rays of 6 and 15 MV: comparison of calculations with measurements.
We present comparisons of calculated and measured dose equivalent rates outside the shielding and in the entry mazes of 2 medical linac facilities producing x rays at 6 and 15 MV. Calculations were made using the NCRP recommendations for estimating transmission of radiation through a shielding wall and scattering of radiation in a maze. We found that, for walls made of high-density concrete, the x-ray dose rate outside the shield was estimated within 50% if transmission factors measured in the appropriate high-density concrete were used. The dose rate was overestimated by a factor of 2-4 when transmission factors for normal concrete were scaled using a density ratio. Dose equivalent rates calculated for x rays and neutrons in the entry mazes agreed within a factor of 2 with the measurements.
Neutrons↗
Determination of 99Tc in urine by liquid scintillation counting to evaluate internal contamination.
A practical method is described which allows the radiochemical determination of 99Tc in urine. The radionuclide is recovered as tetraphenylarsonium pertechnetate by coprecipitation with tetraphenylarsonium perchlorate and its activity is counted by the liquid scintillation technique. The lower limit of detection, assumed equal to three standard deviations of the blank activity, is about 2 pCi in 50 ml of urine and permits an evaluation of an internal contamination of one investigation level even four months after intake. The urinary excretion function of 99Tc is calculated from experimental data reported in the literature for 99mTc and is used to establish derived investigation levels on the basis of annual limits on intake recommended by the International Commission on Radiological Protection. The illustrated method is sensitive enough to perform accurate evaluations every three months, a frequency suitable for radiological protection of workers.
Humans↗
Calibration of a thermoluminescent dosimetry system to measure effective dose equivalent for 6- to 7-MeV gamma rays.
Uncertainty exists as to expected responses of personnel dosimeters when worn in fields of 16N gamma's. Doses to internal organs are also not well known. Accordingly, the response of the Ontario Hydro (OH) TLD badge in terms of the effective dose equivalent (EDE) concept of ICRP Publication 26 was evaluated. Photons at 6-7 MeV were generated from accelerator protons using the 19F (p, alpha gamma)16O* reaction, which closely simulates a 16N-decay gamma field. A phantom containing more than 300 internal TLDs and wearing the OH TLD badges was exposed in stationary and rotational configurations. Ratios of organ dose equivalents (gonads, mean bone marrow, lung and thyroid) to chest badge exposures were 0.6-0.7 for the stationary (frontal) field and 0.7-0.9 for the rotational field. Ratios of EDE to chest badge were 0.60 and 0.77, respectively. The OH TLD badge (and other badges of the same design) will perform satisfactorily in a 16N gamma field under the EDE concept.
Gamma Rays↗
Randomization of grab-sampling strategies for estimating the annual exposure of U miners to Rn daughters.
Periodic grab sampling in combination with time-of-occupancy surveys has been the accepted procedure for estimating the annual exposure of underground U miners to Rn daughters. Temporal variations in the concentration of potential alpha energy in the mine generate uncertainties in this process. A system to randomize the selection of locations for measurement is described which can reduce uncertainties and eliminate systematic biases in the data. In general, a sample frequency of 50 measurements per year is sufficient to satisfy the criteria that the annual exposure be determined in working level months to within +/- 50% of the true value with a 95% level of confidence. Suggestions for implementing this randomization scheme are presented.
Air Pollutants↗
Determination of particle size for airborne UO2 dust at a fuel fabrication work station and its implication on the derivation and use of ICRP Publication 30 derived air concentration values.
When internal radiation exposure occurs via the inhalation route, the activity deposition in the respiratory tract is dependent on the particle size distribution of the radioactive aerosol. This fact has been recognized by ICRP Publication 30 in which annual limit of intake (ALI) and derived air concentration (DAC) values have been calculated for a variety of radionuclides based upon an activity median aerodynamic diameter (AMAD) of 1 micron. When radioactive aerosols have AMADs not equal to 1 micron, ICRP Publication 30 suggests the use of correction factors to calculate the appropriate ALI and DAC values. This work describes the measurement of particle size distribution for UO2 dust at a fuel fabrication work station by means of a cascade impactor. Measurements were made on 39 d spread over a 10-mo period to determine if the particle size distribution was stable over a year. The results of this study indicate that for this work station the measured AMAD values are not stable over a year. A discussion is provided on the treatment of such particle-size distribution data with the objective of extracting a representative particle-size distribution value, upon which an ALI and a DAC value can be determined. The observations made in this study have implications on the application of ICRP Publication 30 recommendations to operational health physics practice.
Air Pollutants↗
H.M. Parker lecture. Radiation protection standards: a historical perspective.
The historical development of radiation standards limiting exposure to people is given in this paper. Since its purpose was to provide information to the public, the number of units is limited to two, and mathematical expressions are avoided. Emphasis is placed on the role of the National Council on Radiation Protection and Measurements and the International Commission on Radiological Protection rather than on regulations because the recommendations of these groups have played a strong part in the formulation of regulations.
Government Agencies↗
Personnel protection challenges in defense and waste management programs.
Three areas are targeted as offering major challenges to the health physicists of the future. One area is in the influx of new technologies, such as laser isotope separation (LIS) and its resultant impact on dosimetry. The LIS process, while generally reducing exposures, also has side effects that make it difficult to detect internal Pu contamination with present methods. Specifically, the LIS process will remove the 241Pu and its 241Am decay product, which is the estimator for Pu, from the 239Pu stream. A second area involves the requirements now being developed for waste management, which also challenges health physicists by insisting upon safe environments for workers who handle waste products while mandating confirmation and cleanup of hazardous wastes. Thus, developing remote inspection techniques will be vital for personnel protection. Finally, military health physicists are faced with the challenges posed to the civilian professionals as well as challenges unique to the military, such as the education of future health physicists to meet the complex military needs.
Health Physics↗
Spatial and temporal distribution of energy.
Studies of the spatial and temporal distribution of microscopic radiation doses lead to potentially important questions regarding conventional approaches to radiation protection. The short ranges of alpha-particle and Auger-electron emissions from radionuclides lead to uncertainties in assessing their hazards. The conventional extrapolations from intermediate doses to low doses and dose rates are questioned by observed dose-rate effects in the so-called "initial slope," by the total lack of data for single tracks in cells and by the possibility of multiple-cell effects. At all subcellular levels, even down to DNA, high linear-energy-transfer (LET) radiations can produce unique initial damage, different from that possible with low-LET radiations, and therefore may even, in principle, produce unique final biological effects. This questions simple extrapolations from low- to high-LET radiations and the application of universal quality factors to diverse effects. Further understanding of these questions could lead, in future, to substantial increases or decreases in estimations of risk.
Alpha Particles↗
The impact of the probability of causation on the radiation protection program.
Although the probability of causation approach is the only scientific basis on which a given cancer can be judged to be causally related to a given exposure, the impact of this concept on the radiation safety program could be counter-productive. As health physicists, the practices and the concepts we employ have been developed to protect the worker. Effective dose equivalent and committed dose equivalent are protective concepts but useless for probability of causation analysis. Perhaps extensive records will be the only way that good radiation protection and probability of causation analysis can coexist.
Humans↗
Measurements of radioactive gaseous releases to air from target halls at a high-energy proton accelerator.
Measurements of induced radioactivity concentration in air were made at five target halls associated with the Fermilab high-energy proton synchrotron. A gas flow-through ionization chamber was used to continuously sample air released from an exhaust stack at each location. The radioactive decay of a grab sample of air from each target hall was recorded, and a best-fit of each decay curve was made via iterative steps to determine the mixture of radionuclides present. The radionuclides 11C, 13N, 15O, 38Cl, 39Cl, and 41Ar were identified. Two distinct radionuclide mixtures or "signatures" were found and were correlated to the geometry of the proton loss point. The normalized activity release rates for the five target areas agree within a factor of two of the average value of 2.7 muBq per proton for 800 GeV protons.
Air Pollutants, Radioactive↗
Long-range alpha detector.
Historically, alpha-particle detectors have been limited by the very short range of alpha particles in air. This results in a number of problems inherent to alpha contamination detectors, such as relatively poor sensitivity, geometry limitations, and inefficient monitoring techniques. In this paper, we document tests of a new long-range alpha detector. The charges generated by the interaction of alpha particles with air can be transported over significant distances (several meters) in a moving current of air generated by a small fan. An ion chamber located in front of the fan measures the current carried by the moving ions and, hence, detects the alpha decays.
Alpha Particles↗