Exposure Rate Measurements Research Articles

Measuring and Predicting Gamma Radiation from Radioactive Glass-Filled Canisters

Measurement and prediction of outside surface exposure rates and measurement of gamma photon spectra from radioactive sources are described. The sources were 30-cm-diam canisters filled with borosilicate glass to a height of {approximately} 100 cm. Each canister contained up to 237 kCi of {sup 137}Cs and 159 kCi of {sup 90}Sr. Exposure rates on the outside surfaces ranged from 26000 to 320000 R/h chiefly from decay of {sup 137}Cs.

Population exposure from nuclear medicine procedures: measurement data.

In order to estimate the public radiation burden from nuclear medicine studies, a TLD chip in a sealed plastic bag was taped on the abdomen of patients who received 111In as chloride or oxine, 201T1 chloride, or one of four common 99mTc agents. The TLD chip was removed after 24 h. Additionally, abdominal skin surface exposure rate measurements were performed with an ionization chamber survey meter at various times (0 to about 60 h). There was superb correlation between TLD and integrated exposure rate measurements and between TLD and ionization chamber measurements and MIRD calculated doses. Scenarios postulated for exposure of co-workers and family members yielded doses between 7 muSv (0.7 mrem) and 20 muSv (2 mrem) for the selected radiopharmaceuticals. Calculations of the total population exposure from nuclear medicine procedures indicate the per capita dose (amortized over the entire population) is approximately 0.4 muSv (0.04 mrem), a negligible dose compared to natural background and total medical irradiation.

Effects on electrical parameters at Athens, Greece by radioactive fallout from a nuclear power plant accident

Some atmospheric electrical parameters, i.e., electric field, conductivity, and small ion concentration, measured at Athens, Greece, after the Chernobyl reactor accident, are analyzed and compared with their normal value and with measurements of radionuclide concentration and exposure rate in the air near the ground. The effects of the radioactive plume on the above electrical parameters, especially the conductivity, are very pronounced.

Measurement of Exposure Rate and Quasi-Effective Energy of Natural Radiation in Japan by Pair-Filter Thermoluminescence Dosemeter Method

Measurement of Exposure Rate and Quasi-Effective Energy of Natural Radiation in Japan by Pair-Filter Thermoluminescence Dosemeter Method

Measurement of Exposure Rate and Quasi-Effective Energy of Natural Radiation in Japan by the Pair Filter Thermoluminescence Dosemeter Method

Measurement of Exposure Rate and Quasi-Effective Energy of Natural Radiation in Japan by the Pair Filter Thermoluminescence Dosemeter Method

Measurement of Exposure Rate and Quasi-Effective Energy of Natural Radiation in Japan by the Pair Filter Thermoluminescence Dosemeter Method

Measurement of Exposure Rate and Quasi-Effective Energy of Natural Radiation in Japan by the Pair Filter Thermoluminescence Dosemeter Method

Rapid measurements of soil contamination after the Chernobyl accident in the federal Republic of Germany by in situ gamma ray spectrometry

The method of in situ gamma ray spectrometry for measurements of soil surface contamination is described. The results of nuclide specific measurements of soil contamination in the Federal Republic of Germany after the Chernobyl reactor accident including exposure rate measurements of individual radionuclides are reported. A total of 22 artificial radionuclides could be detected. In the first days after the Chernobyl accident, the main contamination resulted from the radionuclides 132Te/ 132I and 131I with about 100 kBq/m 2 each and 70 kBq/m 2, respectively. Regionally, large differences in the intensity of soil contamination were found ranging from 1 kBq/m 2 up to 44 kBq/m 2 for 137Cs. The measurements of the activity distribution in soil from various locations have shown about 80% of the total activity to be deposited in the top soil layer down to a depth of 1.5 cm.

Intercomparison Between EML Method and JAERI Method for the Measurement of Environmental Gamma Ray Exposure Rates

Intercomparison Between EML Method and JAERI Method for the Measurement of Environmental Gamma Ray Exposure Rates

Radioactivity measurements in the vicinity of Swiss nuclear power plants

To determine the radionuclide concentration in soil and on soil surface, respectively, caused by radionuclide releases from nuclear power plants, field gamma spectrometry is used to obtain, in a short period of time, quantitative data about the environmental radiation field, natural or man-made. This is obviously difficult to achieve by conventional sampling methods and laboratory analysis. This work describes the instruments used and the calibration methods, and gives the results of in situ measurements made around the Swiss nuclear power plants. The measurements and computations are compared with laboratory analysis of collected soil samples and with total exposure rate measurements in air. In addition to natural radioactivity this method allows especially the detection of radionuclides released from nuclear power stations to the environment with a good sensitivity.

Radon and radon daughter evaluation in a natural radioactivity survey indoors

An indoor survey in order to estimate the population exposure in five towns of an Italian Region is presented. A particular methodology for the campaign was planned and is being applied. Gamma spectrometry of building materials, exposure rate measurements indoors and outdoors and radon concentration measurements indoors were taken with different techniques. A correlation was found between mean gamma exposure rate and mean radon concentration in the houses investigated. An evaluation of mean effective dose equivalents for the inhabitants of the five towns is reported.

Radon concentration in water measured by track detectors

A theory for radon activity measurements in water by track detectors put inside an air cavity in a water medium is presented here. Theoretical assumptions have been tested by means of radon activity measurement in a lake by using the track detector Kodak LR 115. The minimum detectable radon activity in water 2–3 pCi/ℓ was established for the track detector mentioned above. A very small radon accumulation below the ice cover of the lake was proved by measuring the radon activities in the lake during two observation periods (with and without the ice cover). The exposure rate measured on the ice is but negligibly affected by radon and its daughters in the lake. A relatively stable and low-level secondary cosmic-ray background predominates in such environments which allows monitoring gaseous effluents of a higher level by means of exposure rate measurements on the ice cover of lakes near a nuclear power plant.

Exposure-rate calibration of small radioactive sources of 60Co, 226Ra and 7Cs

A comparison between measurements made at the National Physical Laboratory (NPL) and at The Radiochemical Centre Ltd (TRCL) has been carried out in order to assess the accuracy of TRCL's exposure rate calibrations for sources of gamma radiation of a few tens of mCi activity. TRCL calibrations are based either on measurement of absolute disintegration rates together with a knowledge of exposure-rate constants, or, for clinical sources, on a comparison with a secondary standard radium source. Exposure rate measurements were made at NPL on 60Co and 137Cs reference sources supplied by TRCL, and also on an NPL secondary standard 226Ra source. The measurements were made under scatter-free conditions using a 3500 cm 3 spherical ionization chamber, which had been calibrated at NPL in 1 MV and 2MV X-ray beams. The exposure rates measured by NPL were about 3% higher than those stated by TRCL. A similar discrepancy was found between the measured and calculated values for the NPL radium source. These discrepancies are within the arithmetic sum of the estimated uncertainties of the measurements.

EFFECT OF RADIATION AND CONTRAST MEDIA ON CHROMOSOMES

In recent years, the complexity of diagnostic cardiac catheterization and angiocardiography had increased greatly resulting in the performance of more angiocardiograms per study and the lengthening of exposure time. We have measured the chromosome aberrations in blood samples obtained from one child immediately before and for 3 years after 70 min. of radiation during cardiac catheterization and angiocardiography and the micronuclei in blood samples obtained immediately before and after similar studies from 5 children. An increase in chromosome damage was observed in all patients. The absorbed radiation dose estimated from the chromosome damage, on the order of 50 rads, was an order of magnitude larger than the estimate based on measurements of x-ray exposure rates. Subsequently in vitro studies were performed in peripheral blood cells to determine the separate effects of contrast agents and/or radiation on chromosome damage and production of micronuclei. The data clearly indicate that exposure of the cells to 5% solutions of Renografin or Hypaque alone for 30 minutes increases the yield of chromosome breaks and micronuclei to levels comparable to those found in our patients after angiocardiography. The ability of contrast media to break chromosomes in the absence of radiation indicates a hazard in their use to tissues outside the x-ray beams and for times much longer than the x-ray exposure.

"Terrestrial Gamma-Ray Surveys at Preoperational Nuclear Power Plants Using an In-Situ Ge(Li) Spectrometer"

As a prelude to in-situ measurements of gamma exposure rates from reactor plumes, baseline terrestrial gamma-ray surveys have been run at five preoperational nuclear power stations: Fort St. Vrain, Colorado; Fort Calhoun, Nebraska; Cooper Nuclear Station, Nebraska; Rancho Seco, California, and Diablo Canyon, California. A pressurized ion chamber was used to measure the total exposure from cosmic rays and terrestrial radionuclides. A portable Ge(Li) spectrometer was used to make in-situ measurements of the radionuclide soil concentrations and of the individual external gamma exposure rates at the TLD sites. Subsequent measurements after start-up will enable accurate determinations of deposition and buildup of reactor produced fission products to be made. The application of the in-situ Ge(Li) spectrometer for real-time plume dose measurements is being investigated.

Problems of exposure measurement with extended sources; Case of X-ray fluorescence

A number of problems involved in the measurement of exposure rates in X-ray or gamma-ray beams from extended sources were studied. A mathematical model simulating an experimental device producing practically monoenergetic X-ray beams (X-ray fluorescence method) was developed. The theoretical results were in good agreement with experimental data previously published. From this theoretical analogy, it was possible to determine the influence of various parameters of a free-air ionization chamber, and several corrective coefficients were evaluated and measured. The experiments were performed with a mesh-grid free-air chamber especially fitted to wide beams. The results were compared with those of cavity chambers used in the same experimental conditions.

Use of 129I for exposure rate calibration of x-ray instrumentation.

Due to the limitations of several popular techniques for exposure rate measurements at low x-ray energies, it is suggested that encapsulated isotopic sources of /sup 129/I be employed for calibration of monitoring equipment used under these conditions. This isotope emits a gamma photon at 39.6 keV and two K x rays, at 29.6 and 34.0 keV, which result from the internal conversion of the excited state in xenon. Absolute photon intensities for these emissions were calculated to be 4, 82, and 14% respectively. These values were obtained using published internal conversion coefficients, fluorescent yields, and characteristic x-ray relative int;nsities. An encapsulated /sup 129/I source of 1.4 mu Ci is described. and its exposure rate is calculated to be 0.155 mR/hr at 2.5 cm, compared to a measured value of 0.150 plus or minus 0.020 mR/hr. A value of 0.069 plus or minus 0.009 R/hr-Ci at 1 m was measured for the specific gamma -ray constant for this isotope. (auth)

Environmental Radiation Dosimetry for Nuclear Facilities and Problems

The new interest in determining small changes in environmental radiation levels as evidenced by the establishment of as low as practicable numerical criteria indicates a need for reliable low-level radiation measurements. Though the expected contributions from routine operation of nuclear facilities are small compared to existing contributions to dose from natural radioactivity, cosmic radiation and fallout, monitoring programs should be modified to document actual levels and improve public relations as originally suggested by the ICRP. The relative value of instantaneous environmental exposure rate measurements and continuous monitoring is described. Model experiments, some by the Health and Safety Laboratory, are being performed to establish the ranges of validity of dose assessment calculations and improve monitoring techniques. The importance of studies of background variations, trends in long-term additions to the environment, and pathway-to-man analyses is described.

Intercomparison of PTW/Keithley and Baldwin-Farmer dosemeters

A new instrument, consisting of a PTW transit dose chamber and Keithley model No. 602 Electrometer, for calibrating X- and gamma -ray teletherapy units has recently become available. A production model of this unit has been intercompared with a production model Baldwin-Farmer dosimeter with respect to linearity, accuracy, sensitivity, reproducibility, stability, energy dependence and ease of operation. Data for all measured parameters and evaluations are presented. The performance of the two instruments is found to be comparable, with the PTW/Keithley offering specific advantages in range of measurement, time to stability sensitivity, stem effect and ability to measure exposure rates directly.

Portable radiation and light detector using a p-i-n silicon diode

A portable survey instrument using a silicon p-i-n diode as the radiation detector has been designed. It can be used to measure exposure rates in the range 50 mR/hr to 10 R/min, or exposures between 1 mR and 10 R. The radiation waveform can be visualized by attaching an oscilloscope to the output of the instrument. The response per roentgen of the instrument shows a variation of +or-8% in the HVT range from 2 to 8 mm Al. When used as a detector of optical radiation in conjunction with a Wratten No.102 filter, the spectral response closely matches the Standard C.I.E. luminosity curve. The instrument can, therefore, also be used to measure the luminance of fluoroscopic screens to determine the conversion efficiency of conventional fluoroscopes as well as image intensified fluoroscopes.

Exposure rate measurements of x- and gamma-rays with silicon radiation detectors.

Exposure rate measurements of x- and gamma-rays with silicon radiation detectors.