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PubMed1984

Cost evaluation of control measures for indoor radon progeny.

Based on assumed conditions within a typical U.S. home, annualized costs for reducing indoor airborne radon progeny concentrations have been calculated for a variety of methods of control. These analyses were limited to methods for control in existing homes. Control through modified construction techniques was not evaluated. Methods assessed included increased air circulation, increased ventilation, particle removal using electrostatic precipitation and unipolar ion generation, and the application of sealants to room surfaces. Although surface sealants proved to be reasonably cost-effective per person- sievert dose reduction, such sealants are prone to cracking and the durability of their effectiveness is questionable. Use of ceiling fans for increased air circulation and particle deposition appears to be least cost-effective, but this method may be attractive in some cases for reasons of comfort. The use of unipolar ion generators appears to be the best approach from the standpoint of cost effectiveness. These devices are also easy to install and are esthetically readily acceptable.

Air Ionization↗
PubMed1986

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↗
PubMed1995

A comparison of results for the University of Missouri Research Reactor radiological airborne release assessments obtained from PC-based computer programs.

The United States Environmental Protection Agency has published three computer programs, COMPLY, AIRDOS-PC, and CAP88-PC, to assist the regulated community in determining compliance with the Environmental Protection Agency radionuclide air emission standards. The programs calculate radiation doses from routine airborne release to the general public residing outside a nuclear facility site. They consider doses from inhalation, ingestion of contaminated food, air immersion, and ground deposition. A PC-based computer code, XOQDOQ-82, developed for the Nuclear Regulatory Commission, was also chosen to compare and evaluate dispersion results from the Environmental Protection Agency codes for the University of Missouri Research Reactor Center. Effects of building parameters, terrain conditions, and downwind distances on dispersion factors were calculated. The results of this study indicated that dispersion factors calculated using AIRDOS-PC and CAP88-PC were several times lower than those calculated using XOQDOQ-82 at all distances, and those dispersion factors calculated using COMPLY were several times lower than the XOQDOQ-82 values at distances greater than 600 m.

Air Pollutants, Radioactive↗
PubMed1996

Survey of 222Rn concentrations in dwellings and soils in the Dutch Belgian border region.

222Rn levels in dwellings and soil gas have been investigated in the Eijsden-Visé region, located at the Dutch-Belgian border, in order to analyze the relationship between domestic radon levels and soil gas radon levels, in view of the fact that the local geology varies substantially from uranium-rich to uranium-poor rocks and soils. During February 1992, charcoal detectors were exposed for 24 h in 116 dwellings in the township of Visé, a radon prone area in Belgium. As expected, the results show a large regional variation, with an averaged indoor air radon level of 116 Bq m-3. In the nearby township of Eijsden, the Netherlands, an area with a lower radiation level, similar measurements by means of charcoal detectors in 42 dwellings during March 1993, resulted in an averaged indoor 222Rn concentration of 46 Bq m-3. Furthermore, in the same region time-integrated radon measurements were performed in 15 dwellings on different floors. These results indicate that a gradient in indoor air radon concentration exists from basement to upper floor level. In addition, a significant positive correlation has been found between radon gas levels of soils surrounding 26 houses and indoor air radon levels. The variation in indoor air radon levels in the region under study is mainly due to the variation of the radon levels in the soils. A soil gas radon survey is suitable for prescreening of the radon potential of an area taking into account the spatial heterogeneity of the local geology.

Air Pollutants, Radioactive↗
PubMed1999

Suitability of air sampling locations downstream of bends and static mixing elements.

The revised standard for sampling effluent air from stacks and ducts of the nuclear industry places limits on the non-uniformity of velocity and contaminant profiles at the sampling location; namely, the coefficients of variation must not exceed 20% over an area that encompasses at least the center 2/3 of the cross sectional area. Tests were conducted to characterize the degree of mixing at downstream locations as affected by several types of flow disturbances, including 90 degree elbows and commercial static mixing devices. Flow straighteners were incorporated into the ducting upstream of the mixer to be tested to simulate the dampening of flow turbulence that might occur because of upstream HEPA filters. The coefficients of variation of velocity and tracer gas concentration measured in a straight tube at a distance of 3 diameters downstream from a 90 degree elbow were 17% and 69%, respectively. The mixing is impacted by the upstream flow turbulence. Without a flow straightener, the tracer gas concentration coefficient of variation was reduced to 33% at the 3-diameter location. The use of static mixing elements can greatly enhance the mixing process. A ring placed just downstream of a 90 degree elbow, which blocks the outer 56% of the cross sectional area, results in a coefficient of variation of 19% for tracer gas concentration at the 3-diameter location. Pressure loss across the elbow with the ring is about nine times that of the basic elbow. One of the commercially available static mixers provides coefficients of variation that are less than 10% for both velocity and tracer gas concentration at 4 diameters downstream from the mixer with a pressure loss that is only about 3.5 times as large as that of a 90 degree elbow.

Air Pollutants, Radioactive↗
PubMed2003

Validation of the integrity of a HEPA filter system.

The objective of this study was to establish a delayed air sampling method to verify the integrity of an existing HEPA filter system in a ventilated fume hood. (238U,232Th)O2 microspheres were generated to fabricate cement nuclear fuel pellets in a HEPA-filtered hood. To comply with the air effluent concentration limits by NRC, the capture efficiency of the HEPA filter was examined. An in-line isokinetic air sampling system was installed downstream of the HEPA filter. Utilizing a gas flow proportional counter, 212Pb was used as a surrogate to indicate any possible penetration of the (238U,232Th)O2 particles through the HEPA filter. Based on the experimental results, this delayed sampling method proved to be an easy and effective way to validate the integrity of the HEPA filter.

Air Pollutants, Radioactive↗
PubMed2004

Room model with three modal distributions of attached radon progeny.

In this paper a room model with three modal distributions of attached radon progeny is developed. Recoil factors are recalculated for each of the modes, and different recoil factors than usually used are obtained. Dependence of progeny concentration in various modes on ventilation and attachment rate is presented. Unattached Pb is overestimated up to 15% if one modal distribution is used, which can lead to the overestimation of lung dose.

Air↗
PubMed1994

Contamination levels and doses to staff arising from the use of Technegas.

The aim of this work was to assess the levels of airborne activity and contamination arising from Technegas ventilation scintigraphy and to estimate doses to staff. The maximum air concentration was below the 99Tcm-derived air concentration limit and considerably lower than reported levels for conventional radioaerosols. The level of contamination on staff gloves and aprons exceeded the body surface contamination limit in 63 and 9% of cases, respectively. Levels of contamination and air concentration were generally higher if the patient had difficulty with the administration procedure. Room surface contamination was very low. In 24% of cases activity was detectable on staff (either in the hair or nose) using gamma camera imaging. Annual skin doses from these sources are calculated to be below the limit for deterministic effects. Whole body effective doses are calculated to be similar to those received by staff performing other nuclear medicine studies. However, care should be exercised to keep exposure from both airborne and fixed sources to a minimum and a regular review of contamination levels is recommended. We recommend the wearing of gloves for all Technegas administrations and disposable hats and masks may be considered in certain cases.

Air Pollutants, Occupational↗
PubMed1995

Air contamination following aerosol ventilation in the gamma camera room.

Air contamination levels arising from lung aerosol ventilation studies have previously been monitored [1]. Residence time in the room used for ventilation was perceived to be an important factor in dose received. This study was designed to assess air contamination levels when ventilation and imaging are carried out in the same room. Air samples were taken before, during and after aerosol administration, over 24 studies where a mouthpiece was used. The mean airborne contamination during administration was 4.39 kBq m-3, implying an effective dose equivalent (EDE) to the operator from inhaled activity of 0.004 microSv. Measurements made during studies on three patients where a mask was used gave a mean EDE of 0.065 microSv (the highest EDE was 0.08 microSv). Ten minutes after nebulizing had stopped, the contamination had reduced to background levels in all but two cases; in these cases, the levels were less than 1.1 kBq m-3. Aerosol ventilation in the gamma camera room does not constitute a significant radiation hazard to staff. Patient compliance is an important factor in minimizing doses. Clear instructions and practice are a vital part of the procedure.

Aerosols↗
PubMed2006

Mixing in a square and a rectangular duct regarding selection of locations for extractive sampling of gaseous contaminants.

Tests were conducted to characterize the uniformity of velocity and tracer gas profiles in a square and a rectangular duct with respect to defining the suitability of locations for single point sampling of gaseous contaminants. Several configurations, such as a straight duct with unidirectional flow at the entrance section and straight ducts preceded by mixing elements (a 90 degrees mitered bend and double 90 degrees bends in S- and U-type configurations) were tested. Results are compared with those from circular ducts. For a straight duct of square cross section, which is not preceded by a mixing element, the coefficients of variation (COV) of tracer gas concentration at 19 duct diameters downstream of the gas release location is 143% (center release of tracer gas). COVs of velocity and tracer gas concentration in a straight square duct 9.5 duct diameters downstream of a 90 degrees mitered bend are 6% and 24.3% (top inside release), respectively, which does not meet the ANSI N13.1 limit of 20% for the tracer gas COV. In case of the rectangular duct with a 3:1 (width to height) aspect ratio, COVs of velocity and tracer gas concentration at 9 duct diameters downstream of a 90 degrees mitered bend are 29% and 62% (bottom inside release), respectively. A mixing element in a square duct comprised of two 90 degrees mitered bends in a U-configuration produces results similar to those obtained with a single 90 degrees bend. However, COVs of velocity and tracer gas concentration in a square duct 6 duct diameters downstream of an S-type double bend are 10.6% and 8.3% (top inside release), respectively, which comply with the ANSI tracer gas and velocity criteria for single point representative sampling. When mixing elements were employed in square ducts, the COV results were comparable with those of other researchers for circular ducts.

Air Pollutants, Radioactive↗
PubMed2005

Residential radon in Canada: an uncertainty analysis of population and individual lung cancer risk.

Following a comprehensive evaluation of the health risks of radon, the U.S. National Research Council (US-NRC) concluded that the radon inside the homes of U.S. residents is an important cause of lung cancer. To assess lung cancer risks associated with radon exposure in Canadian homes, we apply the new (US-NRC) techniques, tailoring assumptions to the Canadian context. A two-dimensional uncertainty analysis is used to provide both population-based (population attributable risk, PAR; excess lifetime risk ratio, ELRR; and life-years lost, LYL) and individual-based (ELRR and LYL) estimates. Our primary results obtained for the Canadian population reveal mean estimates for ELRR, PAR, and LYL are 0.08, 8%, and 0.10 years, respectively. Results are also available and stratified by smoking status (ever versus never). Conveniently, the three indices (ELRR, PAR, and LYL) reveal similar output uncertainty (geometric standard deviation, GSD approximately 1.3), and in the case of ELRR and LYL, comparable variability and uncertainty combined (GSD approximately 4.2). Simplifying relationships are identified between ELRR, LYL, PAR, and the age-specific excess rate ratio (ERR), which suggest a way to scale results from one population to another. This insight is applied in scaling our baseline results to obtain gender-specific estimates, as well as in simplifying and illuminating sensitivity analysis.

Age Factors↗
PubMed2004

[Cellular biology and public health].

Within the framework of the National Research and Development Program No. 1/016 /2001 the authors determined the population levels of ionizing and nonionizing radiations, elaborated the system of assays for detection of biological effects including dose-effect relationships, studied the roles of protective and sensitizing factors in the effect modification. The radium content of building materials were determined as well as the indoor radon activity concentrations and the magnetic induction fields around household equipment operating with 50 Hz. Biological dosimetry techniques were categorized according to the indication time. In addition, radiation sensitivity of intracellular antioxidant enzymes and the antioxidant capacity of blood sera were measured.

Air Pollutants, Radioactive↗
PubMed2004

Lung cancer risk among Czech tin and uranium miners--comparison of lifetime detriment.

First epidemiological evidence of lung cancer risk from exposure to radon was based on studies of uranium miners. The risk in other mines was reported later. The cohort study among 2466 Czech tin miners was conducted in order to estimate the size of the risk and to compare it to that in uranium mines. Based on 205 lung cancers, the estimate of excess relative risk per unit exposure in the simple linear model 0.011 is compatible with findings from two cohort studies of Czech uranium miners. This similarity holds in more complex models that include modifying effects of age and time since exposure. In addition, an alternative description of the risk in terms of lifetime risk was used. This approach provides summarized characteristics, in which modifying effects of time and age are incorporated. The attributive risk derived from the lifetime relative risk is proportional to cumulated exposure observed in both tin and uranium miners. On the other hand, the expected life shortening of 19 years among radiation induced deaths is similar in these studies.

Adult↗
PubMed2006

[System preserving radiation safety for Moscow population].

Radiation safety system functioning on Moscow territory enables to control potential dangerous sources, opportunely reveal and liquidate accidents and pollutions, forecast degree of radiation jeopardy according to its components.

Air Pollutants, Radioactive↗