**1. NAME AND TITLE OF DATA LIBRARY**

VITAMIN-J/COVA: Neutron Cross-Section Covariance Data in Multigroup Form

**2. NAME AND TITLE OF DATA RETRIEVAL PROGRAMS**

ANGELO2: A program which expands or collapses the cross-section covariance matrices from the energy group structure of the input library into the form required by the user.

PSR-171/NJOY89: A Code system for producing pointwise and multigroup neutron and photon cross sections from evaluated nuclear data in ENDF/B-4 or -5 format (available from RSIC)

**3. CONTRIBUTORS**

NEA Data Bank, Gif-sur-Yvette Cedex, France.

**4. HISTORICAL BACKGROUND AND INFORMATION**

In recent years an increased interest was shown in the use of uncertainty analysis not only for dosimetry and radiation shielding but also for fast reactor and fusion applications. In order to encourage the wider use of sensitivity and uncertainty analysis, the NEA Data Bank was charged by different NEA working groups to collect information available on neutron cross section covariance data and devise a procedure to make the use of such data to be user convenient and friendly. The resulting data library of neutron cross section covariance data was produced from a joint effort at NEA Data Bank, in cooperation with IKE Stuttgart and CEA Cadarache in the frame of the JEF project.

**5. APPLICATION OF THE DATA**

The library is designed for radiation shielding applications.

**6. SOURCE AND SCOPE OF DATA**

The library contains the multigroup relative covariance matrix data for 11 materials: H-1, Li-6, Li-7, Be-9, C, N-14, O-16, Na-23, Cr, Fe, and Ni. In general, the covariances for the total, elastic, inelastic, and nonelastic scattering cross sections and for the cross sections making a significant contribution to the total absorption cross sections are included. The multigroup covariance data are based on: JEF-1, ENDF/B-IV, ENDF/B-V and other evaluations. They were extracted from EURLIB (DLC-35), BABEL(DLC-104), PROPANE, VITAMIN-J, COVFILS (DLC-91), COVFILS-2-I (DLC-138) and SUSD (CCC-501). The data from COVFILS were read off the graph and are therefore approximate. For each material, the energy group structure, relative standard deviations, and relative covariance matrices for different reactions are provided.

**7. DISCUSSION OF THE DATA RETRIEVAL PROGRAMS**

The program ANGELO2 will expand or collapse the multigroup covariance data to a user defined energy structure. This can then be used as input to the COVR module of NJOY to produce a BOXER formatted library. The NJOY module BOXR can convert the resulting data to binary form. An auxiliary program LAMBDA can compute the eigenvalues of the covariance matrices.

**8. DATA FORMAT AND COMPUTER**

Card images; VAX 8810, IBM 9377.

**9. TYPICAL RUNNING TIME**

To produce a 175 group covariance library for H-1 at NEA Data Bank on the VAX 8810, it took: ANGELO2 - about 2 minutes, NJOY COVR - 12 minutes, LAMBDA - over 6 minutes for a 175 group data.

**10. REFERENCES**

**a. Included in the package:**

I. Kodeli and E. Sartori. *Covariance Data Library, ZZ-VITAMIN-J/COVA*, NEA-1264, NEA Data
Bank, France, November 1990.

**11. CONTENTS OF PACKAGE**

The package contains the reference listed above, and the data library and sample input and output. The data library is transmitted on one ds/hd 5.25-inch diskette (1.2 mb).

**12. DATE OF ABSTRACT**

January 1991.

**KEYWORDS: ** BASED ON ENDF/B-V; COVARIANCE MATRICES; MULTIGROUP CROSS
SECTIONS BASED ON ENDF/B; NEUTRON CROSS SECTIONS