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By J. Wes Blakely

In the mid-1950s the importation of foreign oil began to encroach on traditional coal markets such as railroad steam engine fuel, home heating, electrical generating plants, and others. Many of the smaller coal companies with substantial coal reserves subsequently found that they could no longer continue to mine economically and merged in various ways with larger established coal mining concerns. As the seats of top management and authority were removed from the mines to large metro centers such as New York, Pittsburgh, and Chicago, the more personal relationship between mine workers and management that had existed prior to these mergers began to be eroded and replaced by " remote control " mine management. The disappearance of this face-to-face contact of upper management with mine employees tended to create barriers blocking simple effective communications between coal mine management and labor. In examining the human relations aspects of the coal mining industry, many elements, some concerned with work and others not, have depicted the industry as almost devoid of good applied human relations and communications practices, and, in truth, little has been done to alleviate this situation. In past years many coal producing companies, with the exception of one of the largest, failed to adequately define the term "communications" as it applied to their companies, whether internally or externally. Internally many still place heavy reliance on written communications such as company-wide newspapers to do the job of communicating with their employees which they feel ought to be done. One company puts an inordinate belief in its company "newspaper" as the primary instrument to stimulate its work force into increasing productivity. Primarily aimed at the workers, who greatly outnumber the salaried administrative people, this publication mainly documents the fortunes of individual mine workers who are felt to have achieved something with their lives, e.g., a mine worker who had managed to put four children through universities, the philosophy behind this being to inspire other workers to achieve worth- while goals.

Jan 1, 1981

By Clement K. Chase

Since the dawn of cyanidation leaching techniques for precious metals, certain manganese-bearing silver ores have been a problem due to low silver extraction. Since simultaneous occurrence of silver and manganese is common in nature, this situation has made many otherwise attractive silver deposits uneconomic in the past. Several older techniques have been useful but at $1.29 per ounce of silver, the economics were unfavorable. With the new look in silver prices and some improvements in processing technology, neglected silver districts offer new promise.

Jan 1, 1981

By Richard Lovat

INTRODUCTION Soft ground tunnels may be above the ground water table or they may be subaqueous. The ground may be clays, silts, sands, gravels, glacial deposits, boulder tills, and any of these in any combination. Because of the relatively low strength and deformability of soils, difficulties often arise in soft ground tunnelling. These soil characteristics and resultant tunnelling difficulties, have had a direct influence on the development of "Lovat" Tunnel Boring Machines. We have been required to recognize and adapt to unusual ground conditions and to follow through with design, fabrication, and field maintenance to ensure dependable, trouble-free operation. The basic "Lovat" machine is a fully shielded, wheel-type with the cuttinghead driven by a monorace type bearing with gear drive incorporated in the bearing. Mechanical innovations have been added to the basic machine which complement the resources of manpower, equipment, and materials available to the contractor for a specific operation. FULL FACE SUPPORT The installation of hydraulically operated closure doors or flood control doors, at the cuttinghead, is one of the early "Lovat" technical innovations. Flood control doors provide full face support in running or flowing ground. In water bearing sands and silts the excavated material can

Jan 1, 1981

By Robert F. Goss

OCAW appreciates the opportunity given to us by the sponsors of this Conference to present our position and policies on the issue of radiation hazards in mining. Our principal concern is the health impact that the mining of uranium has on our members. OCAW represents 1,500 underground uranium miners and more than 10,000 underground miners with 3,000 in the Rocky Mountain region. The U.S. Public Health Service has determined through mortality studies that the number one cause of death among uranium miners is lung cancer. It was also determined that exposure to radon daughters and mine dust correlates with the lung cancer experience of uranium miners. Data from the U.S. Mine Safety and Health Administration has also shown that not only uranium underground miners, but all underground miners, are exposed to radon daughters -- especially underground miners in the Rocky Mountain region. It is our position that any OCAW underground miner is at potential lung cancer risk. The dosages of radon daughters that our miners are exposed to are very many times the background levels of radon exposures in the communities where they live. We are also aware that cigarette smoking accelerates the onset of lung cancer; however, it has to be clear that the available scientific evidence shows that alpha radiation does initiate lung cancer and that cigarette smoke, as a recognized co-carcinogen, promotes cancer already initiated by radiation. It is true that cigarette smoke increases the risk of cancer significantly for miners exposed to radon, but nonsmoking miners have experienced lung cancer rates twice as high as the comparable members of the U.S. population. OCAW's position is that the occupational regulatory agencies should concentrate on the exposures that can be controlled; that is, occupational exposures rather than life-style exposures. Our Union has maintained a consistent posture in relation to carcinogens in the workplace -- that is, exposure to cancer-causing agents should be limited to the [lowest feasible level]. OCAW has interpreted lowest feasible level as the lower limit of detection of the collection and analytical method used to detect the carcinogen. Our posture is based on the available scientific information on carcinogenesis. We have asked the scientific community, many times, to provide us with safe levels of exposure to carcinogenic substances, including radon daughters. The answer has been: "We cannot determine levels of exposure low enough to assure that no cancer will occur." In short, there is not a "safe threshold" for any carcinogen. This statement does not come from one of the few so-called "pro-labor scientists," it comes from the National Cancer Institute and the National Institute for Occupational Safety and Health. I don't need to be a scientific sage, then, to conclude that the lowest level of exposure corresponds to the lowest risk of developing cancer. That is, then, our policy on exposure to carcinogens. It seems there has been an attempt to ignore the fact that lung cancer in uranium miners is the principal cause of death. Uranium miners are no exception from workers exposed to carcinogens. Our policy applies to them. Uranium miners should be exposed to the lowest feasible level of radon daughters and any decrease in the permissible exposure level is a decrease in their lung cancer risk. Accordingly, OCAW has petitioned the Department of Labor for a new permissible exposure limit to radon daughters in uranium mining, which lowers the current exposure standard from 4 Working Level Months (WLM) per year to 0.7 Working Level Months per year. We made our demand to the Department of Labor on April 20, 1980. We are still awaiting action from the Federal Government on our petition. OCAW is also very concerned with other important health impacts of uranium mining. We are concerned with a rate of disabling accidents and fatalities which is twice as high as the same rate in other underground mines, excluding coal. We are also concerned with the rate of respiratory disease fatalities among uranium miners which is almost four times the rate among a comparable U.S. population. We have expressed those concerns when the U.S. Senate proposed a Federal Compensation Act for uranium miners. That proposal, by Senator Dominici of New Mexico, found a quiet death in two Congressional sessions. In conclusion, our position on lung cancer induced by radon daughters is the same position we have taken with all other industrial carcinogens: The lower the exposure, the lower the risk. OCAW is demanding a drastic decrease of the permissible exposure limits. OCAW will never accept that a segment of our membership which mines uranium should take the lion's share of the risk while the uranium mining companies take all the benefits.

Jan 1, 1981

By Safdar A. Gill

The technique of installing small diameter caissons (drilled piers) through soft clays and water bearing ganular soil is well established for constructing building foundations. Over the past few years, the method has been utilized for constructing a large number of shafts extending into rock for the Chicago's Deep Tunnel Project. This paper will discuss design considerations for obtaining the most economic ground support system, the impact of construction procedures on the support and lateral pressures for design. Construction procedures will be described along with performance of the shafts.

Jan 1, 1981

By H. T. Miller, L. M. Scott

Radiation exposures in Uranium operations may result from external beta-gamma radiation emitted by Uranium and its progeny, internal exposure to alpha and beta radiation due to the inhalation and ingestion of Uranium ores, Radon gas, and Radon progeny in mine, mill, and laboratory atmospheres and from the contamination of environmental working surfaces and clothing by Uranium-bearing compounds and ore. This paper summarizes occupational experience with reference to the exploration, surface mining, underground mining, milling and transport of Uranium by one company in the U.S. and Canada.

Jan 1, 1981

By L. H. Munson, E. H. Carbaugh, D. E. Hadlock, L. F. Munson, R. L. Gilchrist

As a result of the Three Mile Accident and because of evidence indicating radiation protection problems, the U.S Nuclear Regulatory Commission (USNRC) undertook a major effort, with the assistance of the Pacific Northwest Laboratory (PNL), to analyze radiation protection programs at 47 commercially operated nuclear power plants. This effort, the health physics appraisal program (HPAP), using a modified management oversite and risk tree analytical logic methodology (MORT) which consisted of analytical trees with applicable questions for each tree, was subsequently extended to include USNRC licensed uranium mills. In the uranium mill appraisal, a team of four senior radiation safety professionals spent a week at each mill evaluating the total health physics program. Prior to the HPAP, the USNRC inspection efforts were designed to determine if the licensees were fulfilling the requirements of the code of federal regulations and the mills source material license. The HPAP, however, was designed and structured to facilitate an integrated look at the total program. It is also directed into areas for which explicit NRC regulatory requirements may not currently exist. The latitude of the HPAP was designed to allow professional judgement in the evaluation of program adequacy, because merely meeting the explicit regulatory requirements does not necessarily ensure an adequate and effective health physics program. The results of the first eight site visits and the generic health physics problems identified within the uranium milling industry will be identified in this paper.

Jan 1, 1981

By W. Setzepfandt, J. Henneke

PREFACE Debris disposal can very often be a severe problem and major restriction on tunnel boring projects, especially for small diameter tunnels and in underground mines. Hydraulic transport could provide a suitable solution. Investigations have therefore been made in connection with a full-scale project of 4.8 km length and 2,3 m diameter, to obtain the required technical and economical data for planning an optimized transport system, e.g. for a tunnel boring drivage of 6 - 7 m diameter in underground coal mines. INTRODUCTION The Radau-Tunnel, chosen for the investigations, has been designed for transferring flood peaks between the rivers Radau and Grosse Romke in the Harz-Mountain of Lower Saxony. A DEMAG TVM 20/23 H tunnel boring machine was used to drive the tunnel on a rising gradient of 0,53 %. The rock consisted of shale and hornblende (55 %), granite (15 %), diabase (15 %), chert (8 %) and gabbro (7 %). The project has been sponsored by the Federal Ministry of Research and Technology.

Jan 1, 1981

By C. Arthur Lefler

The hydrometallurgical processes for recovery of gold and silver in use at Round Mountain, Nevada and the practical aspects of the operation are discussed. Included are heap leaching by cyanidation, upgrading of solutions by adsorption of values on activated carbon and desorption (stripping) for electrowinning and subsequent refining steps to produce dore metal.

Jan 1, 1981

By V. K. Kakaria

As you know most of the gold and silver is produced by one of the following processes: (1) Agitated Leaching - Carbon adsorption or Merrill-Crowe (2) Heap Leaching - Carbon adsorption or Merrill-Crowe The figure 1 shows a typical flowsheet for recovery of gold and silver using Agitated or Pachuca Leaching Operation. The ore is crushed and ground and then leached in cyanide tanks solution using either Pachucas with air agitation or tanks with mechanical agitation. The soluble metal values are separated from the pulp by counter-current washing. The precious metals from cyanide solution are either recovered by zinc dust (Merrill-Crowe Process) or by loading on carbon and stripping with hot caustic cyanide solution. Gold and silver are electrowon on steel wool cathodes.

Jan 1, 1981

By Richard J. Waxweiler, Frank E. Lundin, Robert J. Roscoe, Victor E. Archer, Michael J. Thun, Joseph K. Wagoner

[Introduction] Since excess lung cancer mortality was first noted in the late 1800's among Joachimsthal-Schneeberg miners, there have been a number of studies of the long term health effects among various types of miners exposed to elevated levels of radon and its radioactive decay daughters. Substantial excesses of lung cancer have been noted among miners in the Joachimsthal mines (Sevc, 1976) , lead-zinc miners in Sweden (Axelson, 1979) , fluorspar miners in Canada (DeVilliers, 1971) , iron miners in Sweden (Renard, 1974) , uranium miners in Canada (Hewitt, 1976), and metal (Wagoner, 1963) and uranium miners in the United States (Lundin, 1971; Archer, 1976). The latter prospective cohort has also been shown to be at an excess risk of death due to tuberculosis, nonmalignant respiratory disease, and accidents when followed through September 30, 1974 (Archer, 1976). This report extends the followup of this cohort of miners through December 31, 1977 and expands the mortality analysis to investigate more cause-specific categories. [Methods] During the decade beginning with July, 1950, medical teams from the United States Public Health Service (USPHS) examined 3362 white and approximately 780 nonwhite males who had worked underground in uranium mines in the Colorado Plateau at least one month by January 1, 1964. Occupational, medical, and smoking histories were obtained during the examinations and often updated/confirmed during subsequent annual censuses of the miners conducted by the USPHS. The white miners now have been followed-up through December 31, 1977 using the Social Security Administration, Internal Revenue Service, direct telephoning and various other sources. Death certificates were obtained for the deceased and coded directly into the Seventh Revision of the International Classification of Diseases, Adapted, using the rules in effect at the time of death. Deceased miners for whom no certificate has yet been located were assumed dead on the date specified by the reporting agency, cause of death unknown. The uranium miners cohort was analyzed using a modified life-table system developed by the National Institute for Occupational Safety and Health (NIOSH). Person-years at risk of dying (PYAR) were calculated for each miner from his first USPHS medical examination date or date upon completion of one month of underground uranium mining if that was later. PYAR were calculated specific for five-year age groups, calendar periods, and periods after first underground uranium mining. The numbers of cause-specific observed deaths among the cohort occurring by December 31, 1977 were compared to the numbers of expected deaths. The expected deaths were calculated by multiplying the appropriate PYAR by the United States death rates for white males specific for five-year age groups, five-year calendar periods, and cause. The results were summed over the age and calendar period specific categories to obtain the total expected deaths for each cause. Standardized Mortality Ratios (SMR's) were calculated for each cause by dividing the observed number of deaths by the expected number of deaths and multiplying by 100. In some tables, two-sided 95% confidence intervals for the SMR's were computed using either Fisher exact confidence limits, if the observed frequency was less than eight, or approximate confidence limits, if the observed frequency was eight or greater, to indicate statistical significance. Because a priori hypotheses had been well established, one-sided lower confidence limits were used for tuberculosis, lung cancer, other nonmalignant respiratory disease (ONMRD), accidents, and total mortality. [Results] The cohort included 589 miners first examined in either 1950, 1951 or 1953; 753 first examined in 1954; 1235 first examined in 1957; 5 first examined in 1958; and 782 first examined in 1960. In Figure 1 the distribution of the cohort by first year of underground uranium mining indicates that 13.7% started before 1947 and would have thus had an opportunity to be followed beyond 30 years

Jan 1, 1981

By Paul F. Gnirk, Ralph A. Wagner, Joe L. Ratigan

This thermomechanical analysis used the finite element method to investigate the behavior of crushed salt backfill in a waste disposal room situated in a salt dome repository. The first of two objectives was to determine the transient temperature rise and degree of thermomechanical consolidation that occur in the backfill as a function of drillhole depths. The second objective involved the evaluation of closure due to salt creep of unlined emplacement drillholes and the determination of pressure on steel sleeve liners in the drillholes should liners become necessary for canister retrieval. The retrievability period was considered to extend for 25 years after waste emplacement. The canisters were assumed to contain ten-year old high level waste with a thermal output of 4.3 kW at the time of emplacement.

Jan 1, 1981

By W. Clark Ashby

Productivity is a fascinating concept. Like motherhood or apple pie, we know it as a good thing. Just what it means is not so clear. To a coal miner we assume it means tons of coal hauled from the mine. To the company president it means profit after capital, labor, and other costs have also been reckoned. To the government economist it means output in a balance of payments. What does it mean to the biologist, and can reclamation really be productive? In this paper we discuss productivity from a biological viewpoint, give some yield data for various types of reclamation plantings, and discuss how our demand for or acceptance of differing kinds of productivity is tied up in bigger questions of land use, environmental stability, and resource allocation.

Jan 1, 1981

By W. Jacobi, B. Haider, D. Regulla, J. Huber

[Introductory Remarks] Thermoluminescence (TL) detectors are widely used for the dosimetry of X- and[ y]-rays. Also filter devices for radon daughter monitoring have been developed in which the a activity on the filter was measured with TL-detectors (Breslin et al., 1977). For this purpose normal LiF-tablets with a thickness of 0.4 - 1 mm were used. However the lower detection limit of such TLmonitors for radon daughters is relative high, especially in areas with a high [y]-background, due to the low [a /-y]-sensitivity ratio of such thick LiF-detectors. This [a/y]-sensitivity ratio can be increased if TL-detectors are used whose thickness is comparable with the range of [a]-particles. On the basis of this consideration we have developed a simple light weighted and sensitive TL-monitor for the measurement of the cumulative radon daughter exposure in air. [Description of the "Monitor] The monitor consists of two parts: The sampling pump with the accumulator, and the sampling probe which contains the air filter and TL-detector system. Both parts are connected with a plastic tube. For operation in mines a light weight, portable air sampler with a built-in accumulator (DuPont model 125 and 200, 400 g) is used which enables an adjustable, constant flow rate in the range of 7.5 -12 1/h. These air samplers allow a sampling period of 10 hours before recharging is necessary. For radon daughter measurements in houses this pump is replaced by a larger, netoperated pump with a flow rate of 180 1/h. Figure 1 shows a schematic cross section through the sampling probe whose weight is 40 g. The radon daughters are collected on a hydrophob membrane filter (Sartorius) with an effective filter diameter of 11 mm and a pore diameter of 3 µm; its collection efficiency for radon daughters is [>] 95%. Above the filter the detector system is mounted. It consists of two thin Tm-activated CaSO4-TL films of 8 mm diameter on a Al-carrier foil manufactured by Matsushita Inc., Japan. The thickness of the TL-film is 6 mg/cm2, which is comparable with the range of a rays. The first detector is faced in 3.5 mm distance above the filter; in addition to the ambient y background this detector is exposed to the [a] and ß radiation from the radon daughters on the filter. Between the first and the second TL-detector is an Al-absorber of 0.5 mm thickness which shields this detector against the [a] radiation and partly also to the ß radiation from the filter. Both detectors have the same [y] shielding. After air sampling both TL-detectors are read-out with a commercial, hot-air reader (Matsushita Inc. / Japan, Model 505 A). The glow-curves are identical for [a and y] rays (Regulla et al., 1980). The integral TLsignal from both detectors is displayed in mR-units (or mR-equivalent). The difference between the response of the unshielded TL-detector above the filter and the shielded TL-detector is proportional to the time-integral of the filter activity, integrated over the sampling period. Calibration and Intercomparison Measurements] The linearity of the a response was checked with a 241Am-source for an [a] fluence on the detector surface of 5400 [a's/cm2•s] in the range of 102 -105 mR-equivalent. Within the experimental error of 15% the response function is linear. The TLD-monitor was calibrated for radon daughters in air by comparison with a calibrated integrating, monitor (WLM-meter) equipped with a Si-surface barrier detector and a direct electronic read-out; this instrument was developed by us for area monitoring some years ago (Haider et al., 1976). The results of simultaneous measurements with the TL-monitor and the electronic WLM-meter in mine areas and in indoor air of houses are shown in figure 2. On the abscissa the mean potential [a] energy concentration (in WL) during the sampling period is given which was derived from the measurements with the electronic WLM-meter. On the ordinate the corresponding response of the TLDmonitor to radon daughters (difference between both TL-detectors) is displayed, expressed in terms of mRequivalent per liter sampled air. It follows from this comparison a linear relationship over the whole range of 0.005 - 5 WL with a standard deviation of 10%. The resulting calibration factor for the TLD-monitor is 18± 2 mRequiv per WL • 1.

Jan 1, 1981

By Paul Eimon

The 1981 Fall field trip of the Denver Region Exploration Geologists' Society focuses on Creede. That is appropriate - because significant mining history has been made and is being made in this off-the-beaten track, high-country mining district. Creede is one of the few Colorado bonanza towns which was big in the 19th Century, had its ups and downs, and produced almost continuously since its discovery. Creede is important to geologists for its: precious and base metal production, current exploration activity, and research into near-surface hydrothermal systems. United States Geological Survey research and field geologists zeroed in on Creede some 25 years ago and their steady, consistent work is now being spotlighted and appreciated.

Jan 1, 1981

By D. H. Lynch

Prompted by the need to conserve energy and reduce operating costs, Agrico Mining Company has made two significant improvements in the transportation of phosphate ore from the mine to the beneficiation plant. One improvement involves a change in a slurry pipeline system which substantially reduced pumping energy, and the other improvement is a major innovation for the phosphate mining industry which involves the transportation of the ore by railroad. This paper briefly describes these two projects.

Jan 1, 1981

By George M. Anderson

The extraction of industrial minerals is usually confined to relatively small mining operations. The recent COSMAR (Committee on Surface Mining and Reclamation) report found that 93% of all mines in the United States were of the small unit variety. Also, of the total number of mines in the U.S. (15,279) 96% were in the industrial minerals (non-metals excluding coal) category. To break it down further, 86% were sand and gravel, and crushed stone operations. Therefore, we are talking about a very large number of small mining operations. If these small miners can afford to hire a college graduate, what kind of training should this person have beyond the normal mining engineering curriculum to best serve the problems that he or she will encounter?

Jan 1, 1981

By Donald M. Podobnik

The Cuajone Concentrator of the Southern Peru Copper Corporation is located approximately 900 kilometers southeast of Lima, Peru, near the 500 year old town of Moquegua, in an area that has been occupied since antiquity. Since the plant was started in July, 1976, the throughput has steadily increased from 36,000 to 46,000 metric tons per day. The widely distributed molybdenite content of the ore body ranges from 0.02 to 0.04% MoS2. The molybdenite content of the copper concentrate has always been sufficient to justify operation of a byproduct molybdenite plant. During the first nine months of 1980, the average grade of the ore was 1.169% copper and 0.026% molybdenite.

Jan 1, 1981

By G. R. Laurer, J. W. Neton, C. Pomroy, N. Cohen, M. Eisenbud

INTRODUCTION In uranium miners, a causal relationship between exposure of the lung to high levels of alpha radiation and the consequential induction of bronchial carcinoma is now well-established (Wagoner, et al., 1965). Quantitation of this cause-effect association presents considerable difficulty, however, as the result of various confounding factors such as the contributing effects of smoking and/or arsenic exposure (Archer, Gillam, and Wagoner, 1976), normal metabolic variability and, perhaps most important of all, the absence of accurate radon/radon daughter exposure data. Estimates of cumulative lung exposures suffer from inaccuracy due to critical factors such as 1) unknown ventilation rates; 2) difficulties in obtaining representative mine air samples; 3) the variable character and magnitudes of the exposure sources; and 4) specific differences in metabolism and job histories that exist among miners. It was with considerable enthusiasm, therefore, that investigators readily embraced the idea of using skeletal burdens of the relatively longlived descendants of radon and its short-lived daughters, i.e., 210 Pb and 210Po (Archer, et al., 1968), to provide a measure of cumulative past exposure wherein the body acts as an integrating dosimeter. Early studies considered excretion rates of 210Pb and 210Po in urine, blood and hair (Sultzer and Hursh, 1954; Black, et al., 1968; Jaworowski, 1965; Bell and Gilliland, 1964) as well as their concentrations in bone samples, if and when they became available (Blanchard, Archer, and Saccomanno, 1969). These methods were ultimately complemented by in vivo, whole-body counting techniques using low background, NaI-Csl(T1) detectors (Eisenbud, et al., 1969). By this latter method, it would be possible to measure the skeletal burden of 210Pb directly, thereby avoiding the many difficulties associated with the relation between nuclide excretion rates and body burden. The rationale was simple; by knowing the skeletal burden of 210Pb it should be possible, by the judicious use of an applicable metabolic model, to estimate the cumulative lung exposure to alpha-emitting radon daughters (Fig. 1). Various models that were consequently constructed, however (Fisher, 1969), all suffered from the same limitation, i.e., the assumption that the source of 210 Pb in the skeleton and the source of lung exposure to the short-lived radon daughters were simply related and, if not, were at [ ] least not too variable (Raabe, 1970). By now, the difficulty with this assumption has been recognized and more sophisticated modeling techniques have been attempted which presumably present a more realistic picture of exposure conditions (Holtzman and Rundo, 1981). There is, nevertheless, the pessimistic view that due to the variety and variability (in time as well as in character) of sources that may exist for the origin of 210Pb in bone, it may [never] be possible to estimate past lung exposures accurately by an indirect, predictive model. For example, the origin of 210 Pb in the skeleton may include such sources as: 1) the decay of short-lived 222Rn daughters, inhaled and ingested; 2) the decay of 222Rn dissolved in body fluids and tissues; 3) directly from 210 Pb present in air, inhaled and ingested; and 4) 210Pb from non-occupational sources, e.g., food, water, smoking and endogenous 226Ra. The contribution of each of these sources may vary depending upon specific site conditions such as ventilation and mining operation. On the other hand, empirical evidence seems to indicate a trend reflecting the simplest of direct

Jan 1, 1981

By Thomas B. Borak, Keith J. Schiager, Janet A. Johnson

INTRODUCTION Several major factors introduce uncertainties into the assessment of radon progeny exposure to miners using time-weighted average radon progeny concentrations: uncertainty in the measurement of radon progeny concentrations in specific areas, assignment of an individual miner's time to those areas, variation in radon progeny concentration between measurements and potential human errors involved in calculating concentrations and handling data. The currently available grab-sampling methods for determining working level were analyzed to determine the magnitude of the uncertainty due to each of these factors. For all measurement methods studied, the variation in the airborne concentration with time in operational areas of a mine is the dominant factor in the uncertainty in determining annual radon progeny exposures for individual miners. Uncertainties relating to accuracy of the method and precision of measurement were found to contribute a significantly greater portion of the total uncertainty than human errors. Under normal conditions, if the technicians performing the measurements are conscientious and well trained, human error contributes little to the total uncertainty of the radon progeny exposure determination. The primary goal of radiation monitoring is the reduction of radiation exposure to the lowest reasonably achievable level below regulatory limits. Monitoring personnel in mines should be trained not only to obtain accurate estimates of miner radiation exposures but also to recognize and, when possible, to implement correction of situations which result in unnecessarily high radon progeny exposures. ESTIMATION OF UNCERTAINTY DUE TO HUMAN ERRORS Human errors affecting the assignment of annual radon progeny exposure to individual miners can be placed in two categories: those related to the measurement of radon progeny concentration in specific mine areas and those related to estimation of occupancy time for individual miners and transcribing data to permanent records. The former are specific for the measurement method used; the latter are common to all methods. Errors in Determination of Working Level All systems for determining radon progeny concentration require measurement of several parameters, which include volume of air sampled, count rate and decay time. These quantities and appropriate constants are used in a basic equation, specific to the system, which estimates working level. An unintentional random mistake in measurement of any one of these parameters or in the selection of proper constants will contribute to the uncertainty in the determination of working level. In our analysis of human error we separated each measurement method into a sequence of independent operations, with each step subject to operator error. For each operation we estimated the probability of occurrence and the consequence of errors to obtain a resulting uncertainty. Certain types of errors result in specific consequences. For example, we assumed that an error of 5 seconds in timing of a 5-minute sample results in a fractional error of 1/60 (1.7%). Other types of errors can result in a range of uncertainty. Transposing digits read from a scaler can produce errors ranging from near zero to approximately 60%. In these cases we calculated the statistical variance for the distribution of errors. We assigned the square root of the variance divided by the mean as the consequence factor for that type of error. This is essentially the same as a coefficient of variation. The product of the probability of occurrence and the consequence factor is the fractional uncertainty in the measurement due to that particular error. The total uncertainty due to human errors is calculated by taking the square root of the sum of the squares of the uncertainties generated by all manual operations. Uncertainties Due to Human Error for the Kusnetz Method One of the techniques most commonly used to estimate working level in U.S. uranium mines is the Kusnetz method. A generalized way to express the equation used to compute WL by this method is: WL = (Net Alpha Counts)/(V)(ST)(CT)(E)(K) where: V = sample flow rate in liters/min ST = sampling time in min CT = counting time in minutes E = absolute counting efficiency K = Kusnetz conversion factor (dis/min-L per WL), as a function of decay time in minutes. The example of human error analysis presented here is based on the Kusnetz procedure having a timing sequence of 5 minutes sampling time, 40 minute decay time, 2 minute counting time. During the sampling procedure a stop watch is used to determine the timing interval. We assume that it is common to make small timing errors of a few seconds, but larger timing errors occur infrequently. Errors greater than 30 seconds are considered to be essentially non-existent since we assume that the

Jan 1, 1981