working level

{{Short description|Unit of concentration of radioactive decay products}}

Working level (WL) is a historical unit of concentration of radioactive decay products of radon, applied to uranium mining environment.{{cite journal|last1=Vaillant|first1=Ludovic|last2=Bataille|first2=Céline|title=Management of radon: a review of ICRP recommendations|journal=Journal of Radiological Protection|date=September 2012|volume=32|issue=3|page=R3|doi=10.1088/0952-4746/32/3/R1|pmid=22809956|bibcode=2012JRP....32R...1V|s2cid=2423305}} One working level refers to the concentration of short-lived decay products of radon in equilibrium with 3,700 Bq/m{{sup|3}} (100 pCi/L) in air. These decay products would emit 1.3 × 10{{sup|5}} MeV in complete decay.{{cite book |last=Shapiro|first=Jacob |date=June 2002|title=Radiation Protection: A Guide for Scientists, Regulators, and Physicians |edition=4th |publisher=Harvard University Press |page=444 |isbn=9780674007406|url=https://books.google.com/books?id=Ber3ENERfGwC&pg=444 |access-date=September 16, 2016}} The Nuclear Regulatory Commission uses this definition.{{cite web|title=NRC Regulations Title 10, Code of Federal Regulations Part 20.1003 |url=https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1003.html|website=United States Nuclear Regulatory Commission|accessdate=16 September 2016}}

Working level month (WLM) is a closely related quantity, referring to exposure to one working level for 170 hours per month. This comes from assuming a 40-hour work week.

In 2002, the NRC regulations limited exposure in mines to 0.3 WL, which was comparable with the standards of International Commission on Radiological Protection at the time.