Information Notice 1991-26, Potential Nonconservative Errors in the Working Format Hansen-Roach Cross-Section Set Provided with Keno and Scale Codes

Potential Nonconservative Errors in the Working Format Hansen-Roach Cross-Section Set Provided with Keno and Scale Codes

ML031190642
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	04/02/1991
From:	Cunningham R, Rossi C NRC/NMSS/IMNS, Office of Nuclear Reactor Regulation
To:
References
IN-91-026, NUDOCS 9103270361
Download: ML031190642 (8)

9 -

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION &

OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS

WASHINGTON, D.C. 20555 April 2, 1991 NRC INFORMATION NOTICE NO. 91-26: POTENTIAL NONCONSERVATIVE ERRORS IN THE

WORKING FORMAT HANSEN-ROACH CROSS-SECTION

SET PROVIDED WITH THE KENO AND SCALE CODES

Addressees

All fuel cycle licensees and other licensees, including all holders of operating

licenses for nuclear power reactors, who use physics codes to support criticality

safety in the use of fissile material.

Purpose

This information notice is intended to alert addressees to. potential problems

resulting from errors in a common calculational method used in the support of

criticality safety. These errors could result in nonconservative calculations

forming the bases for criticality safety limits and practices. It is expected

that recipients will review the information for applicability to their

facilities and consider actions, as appropriate, to avoid similar problems.

However, suggestions contained in this information notice do not constitute

Nuclear Regulatory Commission (NRC) requirements; therefore, no specific action

or written response is required.

Description of Circumstances

Various users of the KENO family of codes have noticed anomalous results when

using some parts of the neutron cross-section data distributed with the KENO

code. The KENO code, a three-dimensional Monte Carlo physics tool, has become

the dominant method for nuclear criticality safety calculations in the U.S. fuel

cycle industry. In the past, the various versions of KENO were commonly used in

a "stand-alone" mode and used a version of the 16-group Hansen-Roach cross- section set. Users referred to this as the "stand-alone" Hansen-Roach set; code

developers referred to the set as the "working-format" library. Dozens of

criticality safety organizations developed a library of benchmark calculations

based on this "working-format" library data set. The developers of the KENO

codes also released a system of codes (SCALE) to process physics data into

problem-dependent cross-section sets for KENO to use. The SCALE package also

included the "working-format" library, to allow running the code-manual's sample

cases and to check past calculations with the current version of the KENO code.

At this time, KENO IV and KENO V.a are the most commonly used versions of the

criticality code. For the code system, SCALE-4 has been recently released;

SCALE-3 remains the most widely used.

Since the release of the SCALE system some years ago, the "working-format"

library was not intended to be used for safety calculations. It has, however,

9103270361 A

IN 91-26 April 2, 1991 remained in wide use to support criticality safety. Recently, an NRC licensee

used the full SCALE-3 system to check a safety evaluation that had used the

"working-format" set. The latter was shown to be 3 percent nonconservative in

k f.The licensee did not pursue finding examples of larger nonconservatism.

Iflconversation with the code developers, the licensee learned that there were

known errors, for various nuclides, in the cross-section "working-format" data

set, that had not been corrected because the data set was not intended for

safety calculations.

In response to this conversation and others, a warning from the code developers

to SCALE users and users of the PC version of the code (KENO5a-PC) was published

in the December 1990, RSIC Newsletter. As a SCALE PC version is not available, PC users need to know about errors in the "working-format" library.

The January 1991, SCALE Newsletter contained the announcement reprinted below:

HANSEN-ROACH WORKING FORMAT LIBRARY

"In addition to the AMPX master format libraries utilized by SCALE,

all releases have included a Hansen-Roach 16 group AMPX working

format cross section library provided for use with the KENO V.a

and XSDRNPM sample problems. All releases prior to SCALE-4 contain

errors in this working-format cross section libraryfor ethe following

nuclides: Mg (12100), SI (14100), S (16100), Mn (25100), Pu-242

(94200), U-238 SIGP=400 (92834), and U-238-6R SIGP=400 (92861). The

impact of these errors depends on the amount of the nuclide present

and the geometric conditions of the problem. One problem utilizing

Mg, Si, and S in a mixture was observed to experience a 3 percent

increase in k-effective when it was run using the corrected cross

sections."

"It was recently recognized that some of the premixed mixtures on the

working format library (all releases, including SCALE-4) were created

using the incorrect-nuclide cross sections mentioned above. These

mixtures include Stainless Steel 304 (200), Oak Ridge Concrete (300),

Ordinary Concrete (301), Magnuson Concrete (302), and Magnuson

Vermiculite (701). The corrected working format library is now being

distributed by RSIC. To date, no statistically significant differences

due to the changes in these mixtures have been observed. However, it

is recommended that those who have utilized one or more of these

mixtures reverify their results using the new working format library."

"Note that only the working format library contains the above errors.

This library was never intended for any use other than running KENO

V.a and XSDRNPM sample problems. The working library will be removed

from the next release of SCALE-4."

Discussion of Safety Significance:

There may exist a large number of criticality safety evaluations that are based on

the "working-format" (also called stand-alone) Hansen-Roach data set distributed

with the KENO or SCALE codes. It is possible that some of these evaluations are

IN 91-26 April 2, 1991 significantly nonconservative. User review of those evaluations for continuing

operations would ensure that adequate safety margins are retained. Note that a

corrected version of the data is available. Versions of the Hansen-Roach data

from other sources may not have these errors.

For safety calculations, it is important for users to adequately validate the

code, physics data, and modeling methods for the intended application with

appropriate experiments. Had appropriate experiments been performed, the

error described above would likely have been discovered earlier.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate NRC project manager.

PaJ '

ChIrles E. Rossi, D(rector Richard E. Cunningham, Director

Division of Operational Events Assessment Division of Industrial and

Office of Nuclear Reactor Regulation Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Robert E. Wilson, NMSS

(301) 492-0126 Attachments:

1. List of Recently Issued NRC Information Notices

2. List of Recently Issued NMSS Information Notices

'.'ttachment 2

0

IN 91-26 April 2, 1991 LIST OF RECENTLY ISSUED

NMSS INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

91-23 Accidental Radiation Over- 03/26/91 All Nuclear Regulatory Com- exposures to Personnel due mission (NRC) licensees

to Industrial Radiography authorized to use sealed

Accessory Equipment Malfunc- sources for industrial

tions radiography.

91-16 Unmonitored Release Pathways 03/06/91 All fuel cycle facilities.

from Slightly Contaminated Re- cycle and Recirculation Water

Systems At A Fuel Facility

91-14 Recent Safety-Related Inci- 03/05/91 All Nuclear Regulatory

dents at Large Irradiators Commission (NRC) licensees

authorized to possess and

use sealed sources at

large irradiators.

91-03 Management of Wastes Contam- 01/07/91 All medical licensees.

inated with Radioactive

Materials ("Red Bag" Waste

and Ordinary Trash)

91-02 Brachytherapy Source Management 01/07/91 All Nuclear Regulatory

Commission (NRC) medi- cal licensees author- ized to use byproduct

material for medical

purposes.

90-82 Requirements for Use of 12/31/90 All registered users

Nuclear Regulatory Comm- of NRC-approved

ission-(NRC-)Approved packages.

Transport Packages for

Shipment of Type A Quanti- ties of Radioactive Materials.

90-81 Fitness for Duty 12/24/90 All U.S. Nuclear

Regulatory Commission

(NRC) materials and

non-power reactor

licensees.

1t4ttachment 2 IN 91-26 April 2, 1991 LIST OF RECENTLY ISSUED

NMSS INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

91-23 Accidental Radiation Over- 03/26/91 All Nuclear Regulatory Com- exposures to Personnel due mission (NRC) licensees

to Industrial Radiography authorized to use sealed

Accessory Equipment Malfunc- sources for industrial

tions radiography.

91-16 Unmonitored Release Pathways 03/06/91 All fuel cycle facilities.

from Slightly Contaminated Re- cycle and Recirculation Water

Systems At A Fuel Facility

91-14 Recent Safety-Related Inci- 03/05/91 All Nuclear Regulatory

dents at Large Irradiators Commission (NRC) licensees

authorized to possess and

use sealed sources at

large irradiators.

91-03 Management of Wastes Contam- 01/07/91 All medical licensees.

inated with Radioactive

Materials ('Red Bag" Waste

and Ordinary Trash)

91-02 Brachytherapy Source Management 01/07/91 All Nuclear Regulatory

Commission (NRC) medi- cal licensees author- ized to use byproduct

material for medical

purposes.

90-82 Requirements for Use of 12/31/90 All registered users

Nuclear Regulatory Comm- of NRC-approved

ission-(NRC-)Approved packages.

Transport Packages for

Shipment of Type A Quanti- ties of Radioactive Materials.

90-81 Fitness for Duty 12/24/90 All U.S. Nuclear

Regulatory Commission

(NRC) materials and

non-power reactor

licensees.

IN 91-26 April 2, 1991 significantly nonconservative. User review of those evaluations for continuing

operations would ensure that adequate safety margins are retained. Note that a

corrected version of the data is available. Versions of the Hansen-Roach data

from other sources may not have these errors.

For safety calculations, it is important for users to adequately validate the

code, physics data, and modeling methods for the intended application with

appropriate experiments. Had appropriate experiments been performed, the

error described above would likely have been discovered earlier.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below or the appropriate NRC project manager.

Charles E. Rossi, Director Richard E. Cunningham, Director

Division of Operational Events Assessment Division of Industrial and

Office of Nuclear Reactor Regulation Medical Nuclear Safety

Office of Nuclear Material Safety

- and Safeguards

Robert E. Wilson, NMSS

(301) 492-0126 Attachments:

1. List of Recently Issued NRC Information Notices

2. List of Recently Issued NMSS Information Notices

EKraus: 3/04/91

• See previous concurrence

OFC:IMUF.* IMUF:* IMUF:* IMSB:* DD/IMNS:*

NAME:RWilson:mh: VLTharpe: GHBidinger: CHaughney: GSJoblom:

DATE:3/05/91: 3/06/91: 3/06/91: 3/06/91: 3/07/91:

OFC:D/DST:NRR* BC/OGCB:NRR* DENS: D/DOEA:NRR:

NAME:ACThadani: CHBerlinger: RECunninham: G

DATE:3/26/91: 3/26/91: 3/.7/91: 3/AJ91:

OFFICIAL RECORD COPY

4.

IN 91- March , 1991 significantly nonconservative. Users should consider reviewing those evaluations

for continuing operations and ensure that adequate safety margins are retained.

Note that a corrected version of the data is available. Versions of the

Hansen-Roach data from other sources may not have these errors.

For safety calculations, it is important for users to adequately validate the

code, physics data, and modeling methods for the intended application. If

applicable experiments are not available, they need to be commissioned.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

the technical contact listed below.

Charles E. Rossi, Director Richard E. Cunningham, Director

Division of Operational Events Assessment Division of Industrial and

Office of Nuclear Reactor Regulation Medical Nuclear Safety

Office of Nuclear Material Safety

and Safeguards

Robert E. Wilson, NMSS

(301) 492-0126 Attachments:

1. List of Recently Issued NRC Information Notices

2. List of Recently Issued NMSS Information Notices

EKraus: 3/04/91

• See previous concurrence

OFCsIMUF:* IMUFs* IMUF:* IMS5B:* UVILMNb:w

NAME:Rrilson:mh: VLTharpe: GHBidinger: CHaughney: GSJoblom:

DATE:3/05/91: 3/06/91: 3/06/91: 3/06/91: 3/07/91:

-31X

=5 OFC:D/DST BC 0 F-D/IMNS: NRR:

---

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E MMan: C H r inger: RECunninhams CRossis _;

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______ --------------------------- tp --

DATE:3tik /91: 3*>/91: 3/ /91s 3/ /91:

OFFICIAL RECORD COPY

IN 91- March , 1991

- I

I //

significantly nonconservative. Users should consider reviewing those evaluations

for continuing operations and ensure that adequate safety margins are retained.

Note that a corrected version of the data is available. Versions of the

Hansen-Roach data from other sources may not have these errors.

For safety calculations, it is important for users to adequate validate the

code, physics data, and modeling methods for the intended ap ication. If

applicable experiments are not available, they need to be iommssioned.

This information notice requires no specific action o wrtten response. If

you have any questions about the information in thi notice, please contact

the technical contact listed below.

Richard . Cunningham, Director

Divisi of Industrial and

Me cal Nuclear Safety

Off ce of Nuclear Material Safety

and Safeguards

Robert E. Wil n, NMSS

(301) 492-0 6 Attachments:

1. List of Recently IssueV NRC Information Notices

2. List of Recently Issu d NMSS Information Notices

EKraus: 3/04/91 OFC:IMBFj, IMUF: I MUF: IMSB s' DD/IMNS: D/IMNS:

NAME:RWilson:mh: VYL ipe: GHBidinger: CHaughney: 6 1 oms RECunningham:

DATE3/SC/91: 3/b /91: 3/b /91: 3/6 /91: 3/7 /91: 3/ /91:

OFFICIAL RECORD COPY