Table 3 Average masses of fissile isotopes for the time periods indicated in Fig. 2a, b

From: Stand-off nuclear reactor monitoring with neutron detectors for safeguards and non-proliferation applications

a
Time Period U-235 (g) Pu-239 (g) U-238 (g) Pu-241 (g) Relative calculated <ϕ>/Ptot Relative measured count rate/power Percentage difference (%) [|meas − calc| / (meas + calc) / 2]
11/2014 to 12/2014 23045.49 434.74 182879.33 32.20 1 1 0.0
04/2016  + 3223.14 (13.98%)  + 36.55 (8.41%)  + 73842.34 (40.38%) -11.06 (-34.35%) 0.879 0.843 4.3
07/2016 to 08/2016  + 2634.01 (11.43%)  + 107.11 (24.64%)  + 77463.17 (42.36%) -8.77 (-27.24%) 0.895 0.920 2.7
  1. Using Eq. (3), the relative neutron flux per unit reactor power is estimated from masses of fissile isotopes which contribute greater than 99.9% of the neutron flux in the reactor core. The estimated relative neutron flux is compared against the average relative detector count rate per unit reactor power for the corresponding time period, measured with (a) the BCS detector at location A, and (b) the B10 + detector at location B. All changes in mass amounts (and corresponding percentage changes indicated in parentheses) are relative to the 2014/11 to 2014/12 time period
b
Time Period U-235 (g) Pu-239 (g) U-238 (g) Pu-241 (g) Relative calculated < \(\phi\) > /Ptot Relative measured count rate/power Percentage difference (%) [|meas – calc | /(meas + calc) / 2]
09/2016 to 10/2016  + 1857.57 (8.06%)  + 620.66 (142.76%)  + 290566.29 (158.88%)  + 41.98 (130.37%) 0.896 0.896 0.0
10/2016 to 11/2016  + 2386.76 (10.36%)  + 793.51 (182.53%)  + 277483.17 (151.73%)  + 80.94 (251.37%) 0.868 0.837 3.6
  1. Using Eq. (3), the relative neutron flux per unit reactor power is estimated from masses of fissile isotopes which contribute greater than 99.9% of the neutron flux in the reactor core. The estimated relative neutron flux is compared against the average relative detector count rate per unit reactor power for the corresponding time period, measured with (a) the BCS detector at location A, and (b) the B10 + detector at location B. All changes in mass amounts (and corresponding percentage changes indicated in parentheses) are relative to the 2014/11 to 2014/12 time period