Protection Against Radiation In Uranium Mines

[Music] [Music] the awesome color of the nuclear explosion has been harnessed that is being used to benefit all our lives [Music] nuclear power plants fueled with uranium are already producing electricity for millions of Americans and many more of these plants will be built in the future [Music] our country is dependent on the uranium industry and that the uranium miners for a continuing adequate supply of this magic element [Music] the magic of uranium stems from its property of radioactivity it is this same property however that endangers the health of workers who mined and handled uranium therefore special precautions must be taken to protect uranium miners from exposure to excessive radioactivity that's what this film is all about [Music] the property called radioactivity means that individual atoms decay at a certain rate and emit energy in the process each decay event results in a breakdown of the original atom into an atom of a different element that is accompanied by a characteristic release of energy beginning with its change to thorium-234 each atom of uranium is transformed in steps through 13 elements before becoming a stable atom of lead one element in this uranium decay series is a gas called radar thus radon is being gradually formed in all uranium bearing Rock being a gas radon can seep into the mine air from rock surfaces and cracks exposed by mine openings normal radioactive decay of radon then continues in the mine atmosphere [Music] radium a radium B radium C and radium C prime are the elements which immediately follow radon in the decay series although decay continues beyond the radium C prime to stable lead the letter changes require much more time the first four daughters of radon are believed to pose the principal threat to the health of uranium miners because they result in a relatively rapid release of alpha energy when a mixture of radon and its daughters is inhaled most of the radon atoms are exhaled before they have time to decay however many radon daughters are retained in the lungs where their decay and release of alpha particles can damage living tissue the hazard is therefore more directly related to the radon daughter concentration in the mine air than to the radon gas concentration [Music] about 1921 an early suspicion of the danger of radiation from radon and it's daughters came from Europe where uranium and radium were being mined in one district where radon dropper concentrations were very high and mine ventilation was poor about half of the deaths among underground miners was from cancer records are not available but it is assumed that early American uranium miners had a similar exposure to radon daughter's studies by the US Public Health Service indicate that radon daughters can be a health hazard in the form of lung cancer when the serious nature of the hazard in American mines became known action was taken to improve ventilation the most effective known defense the standard method of measuring concentrations of airborne radioactivity is by filtering the radon daughter's from a specific volume of air and Counting the decay events on the filter paper with a detection device the result is converted to working levels [Music] one working level is defined as any combination of short-lived radon gutters in one liter of air that will result in the ultimate emission of approximately 130 billion electron volts of alpha energy exposures of individual workers are expressed in working-level mouths this provides an estimate of the radon daughter's inhaled during a month a miner exposed to 5 working levels for 200 months has received 1,000 working-level months of exposure [Music] although medical findings indicate that the incidence of lung cancer among uranium miners increases greatly above 1,000 working-level months there are enough recorded cases at less than 1,000 working level months to indicate that some risk also exists at lower exposure one working-level for long periods of time was considered the maximum average level to which man should be exposed more recent health data has prompted some authorities to recommend that the radiation protection guide for long-term exposure be no more than for working-level months for you the highest incidence of lung cancer has been observed among uranium miners who are believed to have worked in concentrations above 10 working levels for 10 or more years this incidence of cancer also appears to be related to cigarette smoking very few non-smoking uranium miners have contracted lung cancer therefore it is recommended that uranium miners do not smoke radon and its daughters are also found in other mines but usually in low concentrations they may be present in any underground excavation where minerals containing uranium or radium are present in the rock formations the first concern in the radon daughter control program should be proper mind planning to limit the contamination of mine air the less radon and daughter products allowed to enter air currents upstream from occupied mine areas the less ventilation and other measures are required the erection of seals can limit contamination from areas previously mined on the advance seals can also prevent short-circuiting on intake air [Music] seals should be airtight they must be built to withstand concussion from blasting and they must be made of or coated with materials that will the passage of radon gas [Music] urethane rigid foam asphaltic materials and certain plastic films have proven to be effective coverings or coatings for seals a reduced pressure behind seals will prevent contaminants from leaking into active areas such in by a surface fan exhausting from a hole drilled into the sealed area reduces the pressure even with good planning and use of seals some radon and its daughter products will enter active areas the most effective way of controlling this problem is by means of conventional ventilation for adequate control it is necessary to have fans capable of providing plenty of fresh air to all work areas proper air distribution requires advanced planning the primary or main ventilation system handles the total volume of they are exchanged between the surface and underground work [Music] auxiliary fans direct air to active mining areas such as Stopes or dead ends which are not reached by primary air currents well designed and installed mechanical ventilation systems are a necessity for radon daughter control but unless these systems overcome natural graphed effects fresh air volumes may not be adequate and air reversals accompanied by a rapid buildup of radon daughter's may take place the total volume of air required varies with the type of operation and the degree of contamination [Music] the primary air supply must always exceed the combined auxilary fan capacities otherwise recirculation will occur in all but the simplest ventilation systems doors stopping or regulators are needed to control the flow of air these components are often as vital as the fan itself doors left open or damaged and police toppings make the difference between a safe atmosphere one which can be a serious threat to help changing a regulator or opening a door can result in short-circuiting air intended for another work area auxiliary ventilation systems are an aide to the primary systems it is essential that they be correctly installed and maintained Stokes and headings are often impossible to ventilate without auxilary fans the auxilary system must pick up air from the primary system and move it into the mining areas miners ordinarily spend most of their time in face areas hence proper ventilation in such areas is vital an auxilary fan with vent tubing is the most common way of delivering air to working phases [Music] auxilary systems may operate in different ways both metal and plastic tubing are used each type has certain advantages and disadvantages the blowing system is common in uranium mine [Music] the application of a fan blowing air through tube seems simple however studies of ventilation effectiveness show that auxilary systems can be critical sources of trouble if they're not properly installed and maintained [Music] ventilation problems fall into two major categories the first is the delivery of adequate volumes of fresh air to effectively sweep radioactive contaminants from the face area the other problem is that of maintaining the quality of air discharged into the work area even a very small amount of radon daughter's in the intake air greatly increases the air requirements as contamination of the air delivered approaches the maximum recommended concentrations control by ventilation becomes more and more difficult here larger tubing was required and installed to assure adequate air quantities proper fans selection is important the fan was produced sufficient pressure to overcome the maximum system resistance and is satisfied flow and volume requirements because system resistance changes with the length and diameter of the tubing the fan should be compatible with current and projected mining plants tubing type and diameter effects system resistance and the amount of leakage which occurs leakage reduces the amount of air delivered to the working place oversize tubing for example may be more easily damaged this susceptibility to damage may offset the advantage of greater air flow and the fluid system resistance selection of metal or plastic duck should be based on practical considerations metal ducks are more durable however adapting them to irregularities along the mine opening may be more difficult leaks around joints are a common problem encountered when using metal ducts ends may be damaged when ducts are stored a move and joints may leak after they're connected taping joints is one way to minimize leakage [Music] plastic tubing while flexible is more easily damaged than metal belts [Music] unless plastic tubing is properly suspended it may kink and get out of alignment they're buying increasing the resistance tubing should be hung and supported to minimize distortion messenger wires or slings can be used for this purpose sharp turns resultant kinking therefore elbows should be used where sharp angle turns cannot be avoided [Music] to help protect against the health hazard from airborne silica dust air water sprays may be needed in face areas during and immediately following blasting blasting is a common cause of tubing damage when Iraq is naturally dry wetting it at both face and or transfer points is necessary why rock can be thrown many feet from the face metal and plastic ducks are often ruined in this manner tubing ends can be pulled back out of the way at blasting time if a pigtail hung from a messenger wire is provided the discharge velocity of air should be sufficient to sweep the face the maximum distance that air can be expected to travel from the end of tubing is about 25 feet tubing ends must be kept within this distance from the face and the air must be directed at the workers holding down tubing ends with rocks or tying them with wire restricts the air flow [Music] air discharged from tubing at high velocities into large Stokes may rapidly draw contaminated air into the moving Airstream this often results in the air quickly losing its dilution capacity only a short distance from the end of the tooth one way of obtaining greater dilution in the working area is by diffusing the discharged air close to the man in all directions through a section of perforated tubing however this practice restricts airflow and reduces air volume delivered by the fan therefore it is recommended only when there is an abundance of air recirculation of air within individual and between multiple auxilary systems should be avoided when used air from one system enters the intake of another the second system will receive pre contaminated air and may not protect the man smoke clouds can often be used to detect where recirculation is occurring whenever possible all fan inlets should be located eight to ten feet upstream from the first entrance of return air into the air course where it is impractical to prevent all recirculation the primary air current must be adequate to dilute to safe limits the recirculated air constant maintenance is an important requirement for auxilary systems leaky or damaged sections of tubing or ducts should be repaired or replaced promptly we're primary air becomes too contaminated to use for auxilary systems the capacity of the primary system must be increased or the auxilary fan inlets moved closer to fresh air sources if an auxilary system is operating near capacity and a further increase of air volume is needed inline booster fans may be utilized booster fans are often the best way to increase air volume flow through tubing high-pressure leakage can be minimized by proper location of booster fans auxilary systems must be checked regularly by measuring and comparing the intake and discharge air but when leakage becomes excessive the condition should be remedy [Music] if the radon daughter level in the working place is not being controlled a sample taken at the fan Inlet or tubing discharge End will indicate that improvement of intake air quality or quantity is needed [Music] filtration units are sometimes attached to auxilary systems to temporarily cleanse intake air of radon such units do not remove radon gas therefore daughter products may redevelop in the filtered air quickly depending upon the amount of radon present because of the radon buildup factor it is usually impractical to recycle air through filtration units air quality is necessary to adequately ventilate working areas vary with the size of opening the amount of ore exposed and the inflow of radon and its daughter's from adjacent areas experience indicates the two to three thousand cubic feet of uncontaminated air per minute delivered in each production heading will usually control radon daughter concentrations to acceptable levels [Music] the quantity of air delivered should cause an air change in the working areas about every four to five minutes [Music] ventilation should be the concern of everyone who works in a mine fans and other ventilation controls are installed to ensure that an atmosphere is provided which is not endanger health misused or damaged ventilation components can result in hazardous health conditions for everyone working in the affected area lands should be operated continuously while men are underground when a fan is not running radon Daughter concentrations in mine air will build up planted [Music] preferably fans should be operated 24 hours a day where this is not practical they should be restarted soon enough to reduce radon daughter levels to recommended values before men go underground the best way to determine the time needed to reduce this level is to take radon daughter samples at key locations after fans are started even under the best conditions there may be times when men must enter poorly ventilated [Music] in recognition of this problem the Bureau of Mines has tested and approved respirators which should be worn for protection against radon daughters where environmental control is impractical however respirators are only recommended for short-term use and not as a substitute for practical control measures also proper fitting and maintenance are a must if respirators are to fulfil their intended purpose [Music] here a split system of ventilation is then designed to course appropriate quantities of uncontaminated air into each mining section contaminated air from each section is collected in a returned airway and exhausted from the mine without passing through other active mining areas we know that proper ventilation is a practical Hanser ventilation not only dilutes radioactive contaminants but also minimizes weight on daughter-in growth potential we occupational hazard from lung cancer among uranium miners can be avoided but never before in the history of mining has there been so great a need for teamwork between management and employees to combat this problem control of this health hazard is within our grasp we can and must meet this challenge [Music]