def calc_thermal_fission_functions(t0, ts, read_data)
      total_times = t0 + ts
      ff = { ts: 0.0, ts_add_t0: 0.0 }

      (0..read_data.theAn.size - 1).each do |i|
        p_p0_tinf2ts        = (1.0 / 200.0) * read_data.theAn[i] * Math.exp(-read_data.thean[i] * ts)

        p_p0_tinf2ts_add_t0 = (1.0 / 200.0) * read_data.theAn[i] * Math.exp(-read_data.thean[i] * total_times)

        ff[:ts] = ff[:ts] + p_p0_tinf2ts
        ff[:ts_add_t0] = ff[:ts_add_t0] + p_p0_tinf2ts_add_t0
      end
      ff
    end
def calc_thermal_fission_functions(t0, ts, read_data)
      total_times = t0 + ts
      ff = { ts: 0.0, ts_add_t0: 0.0 }

      (0..read_data.theAn.size - 1).each do |i|
        p_p0_tinf2ts        = (1.0 / 200.0) * read_data.theAn[i] * Math.exp(-read_data.thean[i] * ts)

        p_p0_tinf2ts_add_t0 = (1.0 / 200.0) * read_data.theAn[i] * Math.exp(-read_data.thean[i] * total_times)

        ff[:ts] = ff[:ts] + p_p0_tinf2ts
        ff[:ts_add_t0] = ff[:ts_add_t0] + p_p0_tinf2ts_add_t0
      end
      ff
    end
Calculate thermal fission functions from ASB9-2.
 need t0, ts and data with thermal fission(from class DataForASB_9_2)
 ts: Time after remove (sec)
 t0: Cumulative reactor operating time (sec)

 calc_thermal_fission_functions(t0, ts, read_data)

 return { :ts          => P/P0(t_inf, ts)
          :ts_add_t0   => P/P0(t_inf, ts + t0) }