ML20137W101

Forwards Yankee Atomic Electric Co Application of FIBWR2 Core Hydraulics Code to BWR Reload Analysis

ML20137W101
Person / Time
Site:	Vermont Yankee
Issue date:	04/14/1997
From:	Duffy J VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20137W107	List: ML20137W101 ML20137W130
References
BVY-97-46, NUDOCS 9704180034
Download: ML20137W101 (2)

Text

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[ ENGINEERING OFFICE 580 MAIN STREET - +

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, '(506) 779-6711 April 14, .1997 - -

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'.' . United States Nuclesr Regulatory Commission  :

JATTNi Document Control Desk i, = Washington, DC: 20555 z l

1 References; (a)_ License No. DPR-28 (Docket No. 50-271) .

. . (b) YAEC.1299P, " Methods for the Analysis of Boiling Water Reactors Transient

' . Critical Power Ratio Analysis RETRAN - TCPYA01," Yankee Atomic Electric

. Company, March 30,1982. . .

' (c) EPRI NP-1923, FIBWR,"A Steady State Core Flow Distribution Code for .

Boiling Water Reactors, Code Verification and Qualification Report," Electric

- Power Research Institute, July 1981. ,

, (d) EPRI NP-1580, RETRAN, "A Program for One-Dimensional Transient ' .

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Thermal Hydraulic Analysis of Complex Fluid Flow Systems," Electric Power - ,,

Research Institute, December 1978.

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Subject:

Submittal of YAEC-1339," Yankee Atomic Electric Company Application of FIBWR2 Core Hydraulics Code to BWR Reload Analysis"

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Attached for NRC review is YAEC-1339, " Yankee Atomic Electric Company Application of FIBWR2 Core Hydraulics Code to BWR Reload Analysis."_ Vermont Yankee intends to use FIBWR2, a new version of FIBWR, to validate reload analyses which include new fuel types

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- with part length fuel rods and varied water tube designs. The subject report describes the  ;

modifications to the transien.t Critical Power Ratio (CPR) methods [ Reference (b)], which ,

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determine the limiting fuel bundle or " hot channel" response to an Abnormal Operational Transient (AOT). The most limiting AOT provides the largest transient CPR response from

-.which the plant's CPR operating limits are detsrmined. Since Vermont Yankee will use a fuel  ;

assembly with part length fuel rods in the next operating cycle, Cycle 20, it is our intention to

< applyLthis methodology in the Cycle 20 and subsequent reload analyses.

Current Transient CPR Methodoloov ;  ;

!The present YAEC BWR reload mMhodology for determination of CPR operating limits is based 1

, y on the FIBWR and RETRAN thermal h'ydraulics codes [ References (c) and (d)]. This .  :

- methodology empbys a.three_ step process for determining the plant response to an AOT. The i initial step determines the steady. state thermal hydraulic parameters for the core design for  !

' input as initial conditions for RETRAN. The overall plant response to the initiating event of the  !

, ,  : AOT is then simulated with RETRAN. The reactor core power and thermal hydraulic response -

of the system model are then applied as boundary conditions to the hot channel RETRAN g i i model.1 The hot channel response determines the transient CPR via a post processor, *

il TCPYA01, which contains the vendor critical power correlation. '

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1 I - VERMONT YANKEE NUCLEAR POWER CORPORATION f United States Nudear Regulatory Commission -

' April 14,1997 .

Page 2 of 2 l l j

Use of FIBWR2 for CPR Determination .  !

' The FIBWR2 code " hot channel" methodology has been qualified to replace the L RETRAN/TCPYA01 method. The qualification, documented in the attached report, has been .

implemented by: .

• ! comparison to analytic derivations of a flow decay and sinusoidal flow oscillation transients.

e benchmarks to the General Electric ATLAS test facility critical heat flux experiments.  ;

e 1 comparison to the approved YAEC CPR methodology u' sing RETRAN.

Based on the results of this qualification effort, FIBWR2 is an equivalent replacement for the

.RETRAN/TCPYA01 method.' .j Steady-State Anolication of FIBWR2. ;i

Vermont Yankee will also use FIBWR2 as the replacement for FIBWR, the existing computer

i code for the BWR steady-state reload methodology and the foundation of FIBWR2. Vermont 1 Yankee found that FIBWR2 performs identically to the FIBWR code for calculation of steady-

state thermal hydraulics. The steady-state qualification of FIBWR2 has been included by ,

' reference in the attached report.  ;

1 Reauested Review Schedule . . _

Completion of your review is requested by November 30,1997. This will allow time to .

incorporate a reference to the NRC's evaluation of FIBWR2 into the Vermont Yankee Technical .

Specifications so that FIBWR2 can be used for validating Vermont Yankee's Cycle 20 reload l analysis being performed by General Electric. Vermont Yankee will submit an administrative l Technical Specification proposed change by May 30,1997 to incorporate this reference. This l will allow a parallel review of this submittal and the subsequent Technical Specification l proposed change, in this way reference to the NRC's safety evaluation can be promptly added l 1 to the Vermont Yankee Technical Specifications once the NRC's evaluation is complete.  !

We trust that this submittal provides sufficient information for your review. However, if additional information is required,' please contact this office. 1 Sincerely, VERMONT YANKEE NUCLEAR POWER CORPORATION -

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L James J. Duffy

l Licensing Engineer l

c:. USNRC Region 1 Administrator .

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lUSNRC Resident inspector ~-VYNPS  !

USNRC. Project Manager-VYNPS i

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