RSICC CODE PACKAGE PSR-491

1. NAME AND TITLE

NRCPAGE: Code System to Detect Recurring Loss of Nuclear Materials.

2. CONTRIBUTORS

Los Alamos National Laboratory, Los Alamos, New Mexico, through the Energy Science and Technology Software Center, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

Fortran 77; DEC VAX11/780 (P00491DVX1100).

4. NATURE OF PROBLEM SOLVED

NRCPAGE is used in safeguards applications to detect a recurring loss of special nuclear material by frequent evaluation (sequential analysis) of accountability data. Standard sequential testing procedures are traditionally based on sequences of independent and normally distributed measurements. This same approach can be applied to materials balance (MB) data. Here, the term materials balance has a meaning similar to inventory difference and represents a materials loss indicator localized in time and space. However, distinct Mbs cannot be reasonably treated as statistically independent and may not always be reasonably treated as normally distributed. Furthermore, the covariance structure associated with a given MB sequence is not known and must be estimated. Nonindependence is treated by converting the MB sequence to the innovation sequence, sometimes called the ITMUF sequence or the sequence of MUF residuals, which are statistically independent and amenable to sequential test procedures. A one-sided page's test, effective for a wide range of recurring loss scenarios, is applied to the standardized innovation sequence. The program can be easily modified to suit particular needs; the models for the assumption of multivariate normality for MBs when computing the innovation sequence or the test procedure can be changed as can the input/output format, dimensioning, local error checking, and simulation work. Input files can be sequentially constructed using local text editors to update existing files. Output files can be read by graphics, report writer, or other stand-alone utility routines.

5. METHOD OF SOLUTION

Given an input vector of MBs and the associated covariance matrix, NRCPAGE uses subroutines from the LINPACK (NESC 800) program library to obtain the Cholesky factor (the unique lower triangular matrix of the covariance matrix) and then back-solves the triangular system to obtain the vector of standardized innovations based on the normal model for MBs. The standardized innovation sequence is analyzed using a one-sided Page's test. The Page's test is a CUSUM procedure with a restart mechanism, which allows for detection of long-term, lower-level losses as well as shorter term, higher-level losses.

6. RESTRICTIONS OR LIMITATIONS

Maximum length of material balance sequence is 100.

7. TYPICAL RUNNING TIME

The sample problem execution requires 3.94 CPU seconds on a DEC VAX.

8. COMPUTER HARDWARE REQUIREMENTS

The code was developed on a DEC VAX11/780.

9. COMPUTER SOFTWARE REQUIREMENTS

NRC Page was developed under VMS 4.2 with a Vax Fortran 77 compiler. This package was first released by the National Energy Software Center at Argonne National Laboratory in June 1988. It was not tested when it was transferred to RSICC and released in August 2001.

10. REFERENCE

R.R. Picard, "NRCPAGE Applications Manual," NUREG/CR-4497 (April 1986).

11. CONTENTS OF CODE PACKAGE

Included are the reference document and software on DS/HD diskette containing a PkWare® WINDOWS® self-extracting executable, housing source and sample files. The NRC Page files were downloaded to PC, but the software was not converted to run on PC.

12. DATE OF ABSTRACT

August 2001.

KEYWORD: NUCLEAR SAFETY