Representative Shape of a Typical FN Curve A mathematical property of FN curves is that they are either flat or sloping downward as N increases but never upward sloping. An FN curve is typically shown on graphing paper with logarithmic scales on both the vertical and horizontal axes. An FN curve can be either derived from empirical accident data or represented by probabilistic models, which in turn are usually based on empirical data. Since an FN curve represents the potential physical risk to society at a fixed point in time, an FN curve can change shape or shift based on any circumstances that affect the calculation of risk. When an FN curve is constructed with the same units of measurement as an ALARP diagram, the two can be superimposed onto each other. (For more detail, see the ALARP White Paper.) FN Curve with ALARP Diagram Overlay Applicability In the U.S., the ALARP principle has been employed by the U.S. Army Corps of Engineers since 2009. The U.S. Nuclear Regulatory Commission has used a principle similar to ALARP since the 1950s to regulate exposures to radiation (where it goes by the name As Low As Reasonably Achievable, ALARA). In 1972 and 1977 the ALARA principle was adopted into two U.S. federal regulations (10 CFR 835 and 10 CFR 20) to regulate radiation exposures at Department of Energy and NRCregulated facilities.
Representative Shape of a Typical FN Curve A mathematical property of FN curves is that they are either flat or sloping downward as N increases but never upward sloping. An FN curve is typically shown on graphing paper with logarithmic scales on both the vertical and horizontal axes. An FN curve can be either derived from empirical accident data or represented by probabilistic models, which in turn are usually based on empirical data. Since an FN curve represents the potential physical risk to society at a fixed point in time, an FN curve can change shape or shift based on any circumstances that affect the calculation of risk. When an FN curve is constructed with the same units of measurement as an ALARP diagram, the two can be superimposed onto each other. (For more detail, see the ALARP White Paper.) FN Curve with ALARP Diagram Overlay Applicability In the U.S., the ALARP principle has been employed by the U.S. Army Corps of Engineers since 2009. The U.S. Nuclear Regulatory Commission has used a principle similar to ALARP since the 1950s to regulate exposures to radiation (where it goes by the name As Low As Reasonably Achievable, ALARA). In 1972 and 1977 the ALARA principle was adopted into two U.S. federal regulations (10 CFR 835 and 10 CFR 20) to regulate radiation exposures at Department of Energy and NRCregulated facilities.
165862363.docx