# Adjustment of the (235)U Fission Spectrum

## Abstract

The latest nuclear data are used to examine the sensitivity of the least squares adjustment of the {sup 235}U fission spectrum to the measured reaction rates, dosimetry cross sections, and prior spectrum covariance matrix. All of these parameters were found to be very important in the spectrum adjustment. The most significant deficiency in the nuclear data is the absence of a good prior covariance matrix. Covariance matrices generated from analytic models of the fission spectra have been used in the past. This analysis reveals some unusual features in the covariance matrix produced with this approach. Specific needs are identified for improved nuclear data to better determine the {sup 235}U spectrum. An improved {sup 235}U covariance matrix and adjusted spectrum are recommended for use in radiation transport sensitivity analyses.

- Authors:

- Publication Date:

- Research Org.:
- Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)

- Sponsoring Org.:
- US Department of Energy (US)

- OSTI Identifier:
- 14027

- Report Number(s):
- SAND98-2362C

TRN: US0110952

- DOE Contract Number:
- AC04-94AL85000

- Resource Type:
- Conference

- Resource Relation:
- Conference: Tenth International Symposium on Reactor Dosimetry, Osaka (JP), 09/12/1999--09/18/1999; Other Information: PBD: 14 Sep 1999

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; URANIUM 235; CROSS SECTIONS; DOSIMETRY; FISSION SPECTRA; RADIATION TRANSPORT; DATA COVARIANCES; NUCLEAR DATA COLLECTIONS; ADJUSTMENT; LEAST SQUARES; FISSION; BENCHMARK FIELD; (235)U; MADLAND-NIX; SPECTRUM COVARIANCE; SPECTRUM UNCERTAINTY

### Citation Formats

```
GRIFFIN,PATRICK J., and WILLIAMS,J.G.
```*Adjustment of the (235)U Fission Spectrum*. United States: N. p., 1999.
Web.

```
GRIFFIN,PATRICK J., & WILLIAMS,J.G.
```*Adjustment of the (235)U Fission Spectrum*. United States.

```
GRIFFIN,PATRICK J., and WILLIAMS,J.G. Tue .
"Adjustment of the (235)U Fission Spectrum". United States. https://www.osti.gov/servlets/purl/14027.
```

```
@article{osti_14027,
```

title = {Adjustment of the (235)U Fission Spectrum},

author = {GRIFFIN,PATRICK J. and WILLIAMS,J.G.},

abstractNote = {The latest nuclear data are used to examine the sensitivity of the least squares adjustment of the {sup 235}U fission spectrum to the measured reaction rates, dosimetry cross sections, and prior spectrum covariance matrix. All of these parameters were found to be very important in the spectrum adjustment. The most significant deficiency in the nuclear data is the absence of a good prior covariance matrix. Covariance matrices generated from analytic models of the fission spectra have been used in the past. This analysis reveals some unusual features in the covariance matrix produced with this approach. Specific needs are identified for improved nuclear data to better determine the {sup 235}U spectrum. An improved {sup 235}U covariance matrix and adjusted spectrum are recommended for use in radiation transport sensitivity analyses.},

doi = {},

journal = {},

number = ,

volume = ,

place = {United States},

year = {1999},

month = {9}

}