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**Published:** 01 November 2018

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.RIS For RefWorks, EndNote, ProCite, Reference Manager, Zoteo, and many others. .DOCX For Microsoft Word

The process of determining the uncertainty in the neutron fluence from the measured activity of a dosimetry monitor is reviewed and the importance of treating the energy-dependent correlation is illustrated using several representative neutron fields. The process of determining the uncertainty in the neutron fluence when a transfer calibration is used is then detailed. The conversion factor, when a transfer calibration is used, has a term that has an integral over the cross section appearing in both the numerator and the denominator. This term introduces a nonlinear dependence on the cross section within the conversion factor and an explicit correlation between the terms appearing in the numerator and denominator of the conversion factor. A method for rigorously treating this nonlinear uncertainty propagation is presented. This method is based upon utilizing the covariance matrix for the cross section and utilizing a statistical sampling approach based on a Cholesky transformation of this covariance matrix. This methodology is then applied to the determination of the uncertainty from a transfer calibration for a set of nine neutron spectra based upon using the ^{32}S(n,p)^{32}P reaction and a transfer calibration in a ^{252}Cf standard benchmark neutron field. A very strong correlation is found in the cross-section terms as they appear in the numerator and in the denominator. When a rigorous treatment is used to propagate the uncertainty due to the cross section for the dosimetry monitor, the uncertainty in the conversion factor is reduced by a factor of more than ten times from a worst-case approach that treats the uncertainty components in the numerator and denominator as uncorrelated. This ten times difference is also seen when the comparison is made between a rigorous treatment and a treatment of the cross-section contributions where the numerator and denominator are treated as uncorrelated (i.e., when compared to a root-mean-square approach).

**Keywords:**

uncertainty, covariance, transfer calibration, dosimetry, sulfur, activation, neutron fluence, error propagation

**Author Information:**

Griffin, Patrick J.*Sandia National Laboratories, Radiation and Electrical Sciences Center, Albuquerque, NM*

Vehar, David W.*Sandia National Laboratories, Applied Nuclear Technologies, Albuquerque, NM*

Parma, Edward J.*Sandia National Laboratories, Applied Nuclear Technologies, Albuquerque, NM*

Hahn, Kelly D.*Sandia National Laboratories, Neutron and Particle Diagnostics, Albuquerque, NM*

**Committee/Subcommittee:** E10.05

**DOI:** 10.1520/STP160820170043