Dosimeters types

Dosimeter Type Type of Readout Examples Absorbed Dose Range, Gy... 

Ideally when a chemical dosimeter is used to test or assess an ultrasonic device, care should be taken to match the system under study with the dosimeter type. The optimum conditions determined for a reactor using a chemical probe may well not be the same optimum as that required for the chemical system under investigation. Similar observations apply to the use of sonoluminescence. 

Industrial sterilization cycles tend to vary considerably, not only from manufacturer to manufacturer, but often from product type to product type, depending on the bioburden present on a given load. Chemical indicators have historically been used only to differentiate between sterilized and nonsterilized packages. More recent developments have resulted in the availability of chemical dosimeters of sufficient accuracy to permit their appHcation either as total monitors or as critical detectors of specific parameters. 

Various types of detector tubes have been devised. The NIOSH standard number S-311 employs a tube filled with 420—840 p.m (20/40 mesh) activated charcoal. A known volume of air is passed through the tube by either a handheld or vacuum pump. Carbon disulfide is used as the desorbing solvent and the solution is then analyzed by gc using a flame-ionization detector (88). Other adsorbents such as siUca gel and desorbents such as acetone have been employed. Passive (diffuse samplers) have also been developed. Passive samplers are useful for determining the time-weighted average (TWA) concentration of benzene vapor (89). Passive dosimeters allow permeation or diffusion-controlled mass transport across a membrane or adsorbent bed, ie, activated charcoal. The activated charcoal is removed, extracted with solvent, and analyzed by gc. Passive dosimeters with instant readout capabiUty have also been devised (85). 

Noise monitoring is usually located in the HASP as part of the monitoring program. Noise monitoring should be performed in accordance with acceptable practices. Typically, noise levels are monitored in the field with either a Type I or Type II sound level meter (SLM). Noise dosimeter readings can also be obtained to determine the percent (%) noise dose. Noise levels and % doses measured are then compared to limits listed in OSHA standard 29 CFR 1910.95, Hearing Conservation [3]. 

Selection of the type of whole-body dosimeter is important. Inner whole-body dosimeters are usually white, 100% cotton, long underwear purchased from a variety of clothing outlets and stores. One- or two-piece inner whole-body dosimeters are common. Outer whole-body dosimeters can range from hand-made cotton coveralls to shirts and pants bought directly off the shelf at local retail stores. Outer whole-body dosimeters can also be purchased from wholesale clothing outlets. Outer whole-body dosimeters may be any color and may also be 100% cotton or mixed materials, depending on the purpose for which the outer whole-body dosimeter is to be used. For example, one may want to use a coverall as an outer whole-body dosimeter. This would be acceptable even if the coverall were not white and not 100% cotton provided that the fabric did not contain interfering analytical components. 

Many types of matrices have been used in the past to measure the field stability of the test substance. Cotton gloves, cellulose patches, face wipe handkerchiefs and/or gauze face wipe matrices, long underwear (inner dosimeters), pants, shirts, coveralls (outer dosimeters), sorbent tubes, urine, and other matrices are common matrices that have been used for this purpose. 

A short weathering time for hand wash and face wipe samples is appropriate since these types of samples taken from test volunteers are usually processed and frozen immediately and are not subjected to weathering as are the dosimeter or air matrices. 

Field fortification samples are stored under various conditions in the fleld. Generally, after the weathering period is complete, the fleld fortification samples such as dosimeter sections are wrapped in aluminum foil, placed in a pre-labeled zip-type bag, and immediately placed on dry-ice in a cooler or in a freezer. Field fortification samples such as hand washes or face wipes are prepared in labeled jars, the lids are immediately taped with electrical tape, and the jars are placed in a zip-type bag and wrapped in bubble-pack and immediately placed in frozen storage. Air tubes or air filters are collected after weathering and wrapped so as to prevent breakage. These samples are then placed in a pre-labeled zip-type bag and immediately placed in frozen storage. 

In order to determine the dermal exposure of volunteers to chlorpyrifos, the penetration of chlorpyrifos through the outer whole-body dosimeter (coveralls) to the inner body dosimeter (t-shirt and briefs) was measured. The penetration factor was calculated for each volunteer in the study from the experimental data by dividing the amount of chlorpyrifos on the t-shirt and brief sample by the amount of chlorpyrifos on the torso section of the coveralls. This method of calculation assumes that the surface area of the torso section of the coveralls is nearly the same as the surface area of the t-shirt and briefs worn directly under the torso section of the coveralls. A mean penetration factor for each worker type was calculated by averaging all the worker volunteer... 

Measurements were made using two types of passive track-etch alpha dosimeters. One of them was the bare detector of CR-39. After exposure these dosimeters were etched by 30 % NaOH at 70°C for 5 hours. The number of pits was scored under a microscope with a television camera in Shiga University of Medical Science. Methods of calibration and adjustment for deposition of radon daughters introduced by Yonehara (Yonehara et al., 1986) were adopted. The second detectors were Terradex type SF (Alter and Price, 1972). These detectors consist of a plastic cup, covered by a filter to allow entry only of gases, with a track-etch detector inside. The reading of results was carried out by Terradex Corp. in Walnut Creek, California, U.S.A.. The measurements of radon concentration were carried out by both methods in each location, except for Hokkaido where the measurements were done only by Terradex. However, the data obtained by CR-39 detectors will be mainly presented in this paper, because the two methods did not give identical results as separately reported in this proceedings by Yonehara et al. (Yonehara et al., 1986). 

Special precautions The thyroid gland is the critical organ in terms of dose. The effective biological half-life in humans is around 140 days. Store this radioisotope behind lead shielding. Follow institutional regulations regarding (a) type and location of dosimeters and (b) monitoring thyroid for localized uptake. 

Special precautions The maximum range in air is 6 meters, and the maximum range in water is 8 mm. Because bone concentrates phosphate, is the critical organ in terms of dose. Store this radioisotope behind 1-3 cm Lucite shielding. Avoid working over open containers, and exercise institutional guidelines on the type and location of dosimeters. 

Special precautions Store behind lead shielding. Follow institutional regulations regarding type and location of dosimeter. Avoid working immediately above open containers. Because no organ selectively concentrates sodium metabohtes, the entire body is considered to be... 

The use of various types of dosimeters, more or less well calibrated, which convert the photonic energy collected in a specific waveband (variable from one device to another) into an electric signal has led to a situation where comparison of experimental conditions in different laboratories is sometimes impossible. The most rigorous approach would be spectro-radiometry measuring genuine spectral irradiance, but this method requires expensive devices. A comprehensive document has been issued... 

Each type of dosimeter requires a specific procedure to ensure accurate and reproducible results, such as postirradiation heat treatment. Others need to be stabilized for a certain time (up to 24 h with some) before readings of absorbance are taken. The absorbance reading can be done by conventional spectrophotometry or other, more involved methods. 

Alanine dosimeters are based on the ability of 1-a alanine (a crystalline amino acid) to form a very stable free radical when subjected to ionizing radiation. The alanine free radical yields an electron paramagnetic resonance (EPR) signal that is dose dependent, yet independent of the dose rate, energy type, and relatively insensitive to temperature and humidity. Alanine dosimeters are available in the form of pellets or films and can be used for doses ranging from 10 Gy to 200 kGy. A reference calibration service using the alanine EPR system was developed and the scans were sent to the service center by mail. Currently the available system allows transferring the EPR scan to a NIST server for a calibration certificate. This way the procedure has been shortened from days to hours. ... 

HPhe Fricke dosimeter (ferrous sulfate solutions) has been used to measure A the radiation intensity of various types of ionizing radiation sources since its development by Fricke and Morse in 1927 (2). It is widely accepted because it yields accurate and reproducible results with a minimum of care. This system meets many of the requirements specified for an ideal dosimeter (5, 9) however, it has a limited dose range, and for our applications it has been necessary to develop a dosimeter covering larger doses. Of the systems reviewed (6, 7), two (ferrous sulfate-cupric sulfate and ceric sulfate) showed the most promise for use with the radiation sources at the U. S. Army Natick Laboratories (8). Of these, the ferrous-cupric system has received the most use, and this paper describes our experience in using this system and suggests procedures by which it may be used by others with equal success. 

Scientists are often faced with problems directly related to the problem of equivalence of the radiation effects produced by different types of radiation. The most typical are the two following problems. The first has to do with prediction of the radiation effect produced by a given type of radiation based on the data of radiative transformations produced by another type of radiation. This problem is very closely related to the problem of determining the limits of applicability of dosimetric systems (especially, of liquid chemical dosimeters). The second problem concerns the choice of equivalent radiation that can be substituted for a difficult-to-study type of radiation we might be interested in. 

The problem of equivalence of the radiation effects produced by different types of radiation is very important in dosimetry of ionizing radiation (especially, for liquid chemical dosimeters). As we have shown in Section IX.A, in the general case, the radiation effect in a condensed... 

H2S exposure may be monitored by diffusion type colorimetric dosimeters (such as Vapor Gard) color changes from white to brown-black dosage exposure measured from the length of stain in the indicator tube. 

Utilization of passive dosimeters of permeation type of analyte collection stage and thermal desorption of their release... 

Extensive field testing determined that the most suitable and accurate pump for the dosimeter application was one designated "Accuhaler 808," which is manufactured by MDA Corporation. The principle of operation is based upon an aspiration cycle which draws a constant volume of sample air through a limiting type of orifice for each stroke of the pump. A counter reads out the pump strokes and the total sample volume is computed for a given sampling period. The dosimeter... 

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