Working level uranium mines

Khan, A. and C.R. Phillips, A Simple Two-Count Method for Routine Monitoring of Radon and Thoron Progeny Working Levels in Uranium Mines, Health Phys. 50 381-388 (1986). 

This concentration is equivalent to a partial pressure of radon of 6.6x10 atmospheres. Yet this value is an elevated radon concentration. If all of the decay products formed by the decay of the radon remain in the air, then there would also be 10 pCi/1 of Po-218, Pb-214, etc. Such a mixture would be said to be in secular equilibrium. From the monitoring of uranium mines, an equilibrium mixture of these decay products at 100 pCi/1 is called a working level (WL). Thus, a 10 pCi/1 equilibrium mixture represents 0.1 working level. 

In the uranium mining industry, the Working Level (WL) is defined as a concentration of decay products having PAEC equal to that of decay products in equilibrium with 100 pCi l-1 (3.7 x 103 Bq m-3) of radon. The Working Level Month (WLM) is defined as exposure to decay products equivalent to 1 WL for 170 h, this being the nominal number of hours worked per month in a mine. The WLM is still used in discussions of the epidemiology of lung cancer in relation to exposure to radon and its decay products. 

Kazakhstan has a nuclear scientific-industrial complex which was set up as a part of a nuclear infrastructure of the former USSR. More than 50% of the uranium resources of the former Soviet Union are in Kazakhstan, with seven uranium mines. Two UO2 plants produced up to 35% of the total uranium in the USSR in 1990. There are extensive facilities for producing UO2 pellets for VVER fuel elements from Russian enriched uranium. Kazakhstan has several research reactors and one operating nuclear power plant, the BN-350 fast reactor, which started operation in 1973 with a design life of 20 years. Work on its lifetime extension has the intention of bringing it into compliance with current safety standards. 1995 and 1996 were devoted to this work. In October 1996. experimental investigation on accident-proofdecay heat removal by natural circulation was carried out. The reactor BN-350 was restarted in February 4, 1997 at a power level of 420 MW(th). 

Seven-state Uranium Mining Conference on Health Hazards established "working levels" of radon and radon daughters in uranium mines. 

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