Decontamination Factor Calculator

DF compounds multiplicatively, not additively — if each pass cuts contamination by the same factor, the total DF after n passes is (DF per pass) raised to the nth power, not n times the per-pass DF. So finding the average per-pass DF from a known total requires taking the nth root, and the calculator's projection of additional passes needed likewise uses logarithms rather than simple division, since it's solving for an exponent.

The per-pass DF is an average computed by assuming every pass removed contamination at the same geometric rate. In practice, early passes typically remove loosely-held surface contamination quickly, while later passes are left fighting harder-to-reach fixed or embedded contamination that comes off much more slowly — so real per-pass DF usually declines as you go, even though the calculator's model treats it as constant.

It's a single simplified comparison: is your final contamination level below 1,000 Bq/cm²? Real unrestricted-release limits are considerably more nuanced — they vary by specific radionuclide, by whether the emission is alpha, beta, or gamma, and by the regulatory framework governing the site, so this flag is meant as a quick directional check, not a substitute for the actual release-survey criteria that apply to your facility.

Efficiency is derived from DF using η = (1 − 1/DF) × 100, so the two describe the same cleanup result in different scales. A DF of 10 corresponds to 90% efficiency, a DF of 100 to 99% efficiency, and a DF of 1,000 to 99.9% — efficiency approaches but never reaches 100% since that would require an infinite DF, i.e., zero remaining contamination.