半衰期T_(1/2)是指某放射性核素的原子数目衰变到一半所经历的时间。用半衰期估计长时间内由某放射性核素做成的放射源的衰减是非常方便的。如经历的时间f=nT_(1/2),式中n是数值,则衰变修正因数K_d=(1/2)~n。经过时间t后,放射源的活度A=A_oK_d,A_o为零时刻(某起始时刻)的放射源活度。 测量工作中,经常需要确定短时间内的衰变修正,利用5‰衰变时间参数T_(o·o5)能非常方便的解决这一问题。T_(o·o5)是指某放射性核素的原子数目衰减到原来的0.995倍 The half-life T_ (1/2) is the time elapsed from decaying the number of atoms in a radionuclide to half. It is very convenient to estimate the decay of a radioactive source made of a radionuclide over a long period of time using the half-life. If the elapsed time f = nT_ (1/2), where n is a numerical value, then the decay correction factor K_d = (1/2) ~ n. After the time t, the activity of the radioactive source A = A_oK_d, A_o is the activity of the radioactive source at time 0 (a starting moment). In the measurement work, it is often necessary to determine the decay correction in a short period of time. This problem can be easily solved by using the 5 ‰ decay time parameter T_ (o · o5). T_ (o · o5) refers to the number of atoms of a radionuclide decay to the original 0.995 times