ML20151M586

Forwards Fuel Accountability Nodal 3 Dimensional Validation Rept,Per 880417 Discussion.Description of Anticipated Use of Sys Also Encl

ML20151M586
Person / Time
Site:	Fort Saint Vrain
Issue date:	07/22/1988
From:	Brey H PUBLIC SERVICE CO. OF COLORADO
To:	Calvo J NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM), Office of Nuclear Reactor Regulation
Shared Package
ML20151M591	List: ML20151M586 ML20151M597
References
P-88224, TAC-69028, NUDOCS 8808050250
Download: ML20151M586 (4)

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2420 W. 26th Avenue, Suite 1000, Denver, Colorado 80211 July 22, 1988 Fort St. Vrain Unit No. 1 P-88224 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Attention: Mr. Jose A. Calvo Director, Project Directorate IV Docket No. 50-267

SUBJECT:

Submittal of FAN 30 Plidation Report

Dear Mr. Calvo:

On April 17, 1988, PSC discussed the FAN 3D (Fuel Accountability Nodal, 3 Dimensional) effort with you and Mr. Dan Fieno. FAN 3D is a system of computer programs that produces three dimensional flux, power, and fuel accountability information for the Fort St. Vrain nuclear core. Previously, the GATT system of codes was utilized to provide this information. Based on the conversations with NRC to date. PSC currently intends to use the FAN 3D code for the next semi-annual fuel accountability report per the requirements of 10CFR74.13.

At present, PSC is preparing internal engineering guidelines and procedures for the use of the FAN 3D code package. Once NRC approval is obtained, PSC plans to use the code for safety-related analysis and design.

NRC requested during the April 17 discussion that PSC provide additional information on the history, overall scope, and objectives of the FAN 3D program. In addition, NRC requested that PSC provide a description of the anticipated uses that this system of codes will have for FSV applications. This information is provided in Attachment 1. Attachment 2 (General Atomics (GA) Report No. 909436) is the final product of the joint PSC/GA program under which the FAN 3D system of codes was developed, V

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P-88224-Page 2 July 22, 1988 PSC requests that NRC review the enclosed material. We would like to have NRC approval to use FAN 3D for safety related design and analysis by December 31, 1988. In-the meantime,_PSC will._use'the code only for monitoring and informational purposes - and .for providing fuel accountability information.

PSC is currently reviewing our in-house _ controls for the use of this code-package. As a result of this review, the_ proper PSC software controls will be implemented along -with the appropriate user guidelines for the code package. PSC intends to implement these controls prior to any official use of the code package.

If you have any questions concerning this submittal or our plans, please contact Mr. M. H. Holmes at (303) 480-6960.

Very truly yours,

&C H. L. Brey, Manager Nuclear Licensing and Resource Management HLB /SEF:pa Attachments l

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Attachment to P-88224 Page 1 ATTACHMENT 1 DESCRIPTION OF CORE PHYSICS COMPUTER CODES BACKGROUND In the fall of 1985, PSC commenced negotiations with GA concerning the cooperative development of a -new three dimensional core physics analysis program. PSC was interested in obtaining three

. dimensional core physics capability for in-house use. PSC had long been capable of performing in-house two dimensional analysis (with the GAUGE code) since 1983. The tool- for performing three dimensional analysis for Fort St. Vrain involved the use of the GATT system of codes. This system of codes principally consisted of the P0KEGT, GZINT, GATMAC, GATT, and BUGATT codes (See Section 5 of Attachment (2) for code description). In addition, -there were a number of other data editing and data transfer codes that were utilized in tandem with the principal codes. The GATT code itself performed the three dimensional diffusion calculation for FSV and was written specifically for the GA UNIVAC mainframe. It was GA's opinion that this code was, for all practical purposes, not transferrable to another machine. In addition, this code can take as long as 1 CPU hour of time to run. The other codes in the GATT system were amenable to adaptation on another computer system. At that time, nodal methodology (in additional to standard finite difference) for hexagonal geometry was available to users in the form of the DIF3D code (See Attachment (2), Sections 1 and 5 for description).

To address these issues, PSC and GA decided to enter into a cooperative program to adapt the DIF3D code for Fort St. Vrain applications. A letter of agreement was signed by both parties (dated January 14,1986). In the first part of the program, the DIF3D code was "spliced" into the GATT system of codes by PSC to perform the diffusion calculation. The basic cross-section and burnup methodology were unchanged. PSC would first convert the codes and models to PSC's inhouse IBM machine (utilizing a FORTRAN 77 compiler). After testing on the PSC IBM machine, GA utilized a CRAY machine to run the converted package of codes over a significant amount of burnup history. The results of these analyses were benchmarked against the result of GATT analyses to validate the new code package.

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Attachment to P-88224 Page 2 Tt was decided to name the entire package of codes FAN 30 (Fuel Accountability Nodal, 3 Dimensions). In essence, the technology and experience gained from the program as well as the final product would be shared between the two companies. The final product would include a validation report that documents the suitability of using the FAN 3D system of codes for Fort St. Vrain applications.

APPLICATIONS The GATT system of codes has been traditionally used for a number .

of applications. It is used to perform three dimensional fuel accountability calculations for Fort St. Vrain. In addition, it is the tool with which three dimensional power distributions are calculated. It is a principal source of axial power distribution information for both fuel design applications and -core follow-on analysis. In addition, neutron leakage, core reactivity, and radial power distributions can be determined from the GATT results.

However, due to the great expense and complexity associated with running the GATT system of codes, it is only uc2d when absolutely necessary.

In general, most of the core analysis is performed using the two dimensional (radial) GAUGE code (See Attachment (2), Section 5).

However, when a new reload segment is designed, the GATT system of codes is used as a final check of the axial power shape of the core throughout the cycle for technical specification compliance verification.

The FAN 3D system will be used to perform the same applications as identified above for the GATT system. The nodal solution is roughly an order of magnitude faster than the GATT solution. In addition, it is generally accepted that the one node per block nodal solution used in the FAN 3D code system is significantly more accurate than the standard radial seven points / hex finite difference solution currently used in both the GATT and GAUGE codes for Fort St. Vrain. These features make the nodal option very attractive for performing three dimensional (or two demensional) analysis for Fort St. Vrain. It is likely that the three dimensional tool will be run more often to take advantage of these features.