B14660, Informs of Changes to & Errors in ECCS Evaluation Model or Application of Model for Mnps Unit 3 Per 10CFR50.46(a)(3)(ii)

Informs of Changes to & Errors in ECCS Evaluation Model or Application of Model for Mnps Unit 3 Per 10CFR50.46(a)(3)(ii)

ML20059J064
Person / Time
Site:	Millstone
Issue date:	11/04/1993
From:	Opeka J NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
B14660, NUDOCS 9311120003
Download: ML20059J064 (7)

Text

,

7 NOitTHEAST UTILITIES o.ner.i Onice. . seioen sir 1. serien. Connecticoi 9 I N* I P.O. SOX 270

• * " * * *

• HART FORD, CONNECTICUT 06141-0270 k k J 'c7$ CZ),22, (203) G65-5000 November 4, 1993 Docket No. 50-423 B14660 Re:10CFR50.46(a)

U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Gentlemen:

Millstone Nuclear Power' Station, Unit No. 3  :

Reporting of Changes to, and Errors in, Emeraency Core Coolina System Models or Acolications In accordance with 10CFR50.46(a) (3) (ii), transmitted herewith are the changes to, and errors in, the Emergency Core Cooling System (ECCS) evaluation model- or application of the model for Millstone Unit No. 3. .

.The last annual update was submitted to the NRC on February 26 , 1993.'" Since that time, Westinghouse Electric Corporation, by gpy of its September 22, 1993, l etter, t2' and its September 27, 1993, letter, notified Northeast Nuclear  :

Energy Company (NNECO) of two changes to, or errors in, the small break loss of.

coolant accioent (SBLOCA) analysis performed for Millstone Unit No. 3. The ,

absolute magnitudes of the peak cladding temperature changes was calculated to be greater than 50*F. The changes or errors were: 1) a change in the assumption -

for safety injection (SI) into the reactor coolant system (RCS) broken loop using i the NOTRUMP ECCS SBLOCA evaluation model; and 2) a coding error in the NOTRUMP ECCS SBLOCA evaluation model vertical flow regime map.

(1) J. F. Opeka letter to U.S. Nuclear Regulatory Commission, " Reporting of Changes to and Errors in, Emergency Core Cooling System Models or l Applications," February 26, 1993.

l letter No. NEU-93-218 from J. R. Gasperini (Westinghouse) to F. R. Dacimo j

.(2)

(NNECO), " Millstone Nuclear Power Station Unit No. 3 - Safety Injection i

in the Broken loop," dated September 22, 1993.  ;

(3) Letter No. NEU-93-220 from J. R. Gasperini (Westinghouse).to F. R. Dacimo  ;

(NNECO), " Millstone Nuclear Power Station Unit No. 3 - -10 CFR 50.46 ' i i

Notification and Reporting Information," dated September 27, 1993.

<nnnn, 00 '

"" "E V * ** 9311120003-931104 B t i'1 PDR P

ADOCK 05000423 ppg D g i I i

U.'S. Nuclear Regulatory Commission B14660/Page 2 November 4, 1993 In previous NOTRUMP SBLOCA analyses, S1 flow into the broken loop was modeled as spilling directly into the containment sump to provide conservative peak clad temperature (PCT) results. Results from recent evaluations indicate that for-SBLOCA events using the NOTRUMP ECCS SBLOCA evaluation model, modeling SI flow into the broken loop will actually result in an increase in PCT of 150*F. While the change in assumption for SI into the RCS broken loop results in a significant change as defined by 10CFR50.46 (a) (3) (i), Westinghouse has identified an offsetting steam condensation benefit which more than offsets the increase in PCT. Westinghouse, by copy of its October 11, 1993, letter,"8 provided NNEC0 with NRC feedback on the issue of SI in the broken loop. It was noted that additional effort would be required to resolve this issue. The Westinghouse Owners Group is reviewing this issue and the possible development of a generic program for resolution . NNECO will provide a schedule for resolution subsequent to the February 1994 Westinghouse Owners Group meeting.

The correction to the coding error in the NOIRUMP ECCS SBLOCA evaluation model vertical flow regime map resulted in PCT effects ranging from -13*F to -55*F.

For the purposes of tracking PCT, the minimum benefit of -13*F has been assigned to this error. Since it has been demonstrated that the effect of this error may exceed 50*F, this error is considered significant with respect to 10CFR50.46 (a)

(3) (i) requirements.

The individual changes to or errors in the NOTRUMP ECCS SBLOCA evaluation model resulted in significant changes to the PCT as defined by 10CFR50.46 (a) (3) (i) and, as such, are being reported as required by 10CFR50.46 (a) (3)(11).

The attachment to this letter provides an ECCS Evaluation Model Margin Assessment which accounts for (A) the analysis of record, (B) permanent 10CFR50.46 LOCA Model Assessments prior to 1993, (C) margin utilization attributable to 10CFR50.59 evaluations up to the present and (D) 1993 10CFR50.46 Model assessments for which this notification is being performed. Considering these changes, the corrected PCT for the limiting SBLOCA remains below the 2200*F limit as defined by 10CFR50.46(6)(1).

I (4) Letter No. NEU-93-222 from J. R. Gasperini (Westinghouse) to F. R. Dacimo (NNECO), " Millstone Nuclear Power Station Unit No. 3 - NRC Feedback on the Safety Injection in the Broken Loop," dated October 11, 1993.

l l

1 l

______________________________________.____________u

i

. . . i i

U.S. Nuclear Regulatory Commission  :

814660/Page 3 l November 4, 1993  :

We trust that this information satisfies the reporting requirements of 10CFR50.46  !

(a) (3) (ii).

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY l FOR: J. F. Opeka  ;

Executive Vice President  !

i BY: b M.1. 6 E. A. DeBarba Executive Vice President  :

Attachment ,

cc:- T. T. Martin, Region I Administrator  ;

V. L. Rooney, NRC Project Manager, Millstone Unit No. 3  :

P. D. Swetland, Senior Resident Inspector, Millstone Unit Nos. 1, 2, I and 3  :

I i

i P

i h

Docket No.' 50-423 B14660

-i i

k Attachment 1 Millstone Nuclear Power Station, Unit No. 3 Reporting of 10CFR50.46 Margin Utilization Small Break LOCA f

I L

i j

i November 1993

'l i

i

i u

e . .

U.S. Nuclear Regulatory Commission B14660/ Attachment 1/Page 1 November 4, 1993 Reporting of 10CFR50.46 Margin Utilization [

Small Break LOCA i I

Millstone Unit No. 3 PLANT NAME:

Clad Temnerature Notes l A. Analysis of Record (6/90) '

l Eval. Model:

NOTRUMP Fuel: VANTAGE SH PCT - 1891*F FQ-2.6 FAH-1.7 SGTP-10%

B. Prior Permanent LOCA Model Assessment APCT= 27'F C. 10 CFR 50.59 Safety Evaluations

1. Increased Pressurizer Pressure Uncertainty APCT= 14*F

2. Effect of ZIRLO Fuel cladding APCT- 24*F

3. Fuel Rod Crud APCT- '2*F Total 10 CFR 50.59 Small Break Assessments APCT= 40*F D. 1993 10 CFR 50.46 Model Assessments  !

(Permanent Assessment of PCT Margin)

1. Effect of SI in Broken Loop APCT- 150*F

2. Effect of Improved Condensation Model APCT= -150*F '

3. Drift Flux Flow Regime Model Errors 6 PCT = -13*F i

LICENSING BASIS PCT + MARGIN ALLOCATIONS PCT = 1945*F l

Docket No. 50-423 B14660 1

P 4-s t

t I

t Attachment 1 .)

Hillstone Nuclear Power Station, Unit No. 3 l Reporting of 10CFR50.46 Margin Utilization Small Break LOCA j '

?

3 i

e t

't 1

i i

November 1993  !

P N

i

U.'S. Nuclear Regulatory Commission  !

B14660/ Attachment 1/Page 1 November 4, 1993 j Reporting of 10CFR50.46 Margin Utilization Small Break LOCA PLANT NAME: Millstone Unit No. 3 Clad Temperature Notes A. Analysis of Record (6/90) ,

Eval. Model: NOTRUMP Fuel: VANTAGE SH PCT = 1891*F FQ-2.6 FAH-1.7 SGTP=10%

l B. Prior Permanent LOCA Model Assessment APCT= 27'F C. 10 CFR 50.59 Safety Evaluations

1. Increased Pressurizer Pressure Uncertainty APCT= 14*F

2. Effect of ZlRLO Fuel Cladding APCT= 24*F  !

3. Fuel Rod Crud APCT= 2*F Total 10 CFR 50.59 Small Break Assessments aPCT= 40*F  :

D. 1993 10 CFR 50.46 Model Assessments (Permanent Assessment of PCT Margin)

1. Effect of SI in Broken Loop APCT= 150*F

2. Effect of Improved Condensation Model APCT= -150*F

3. Drift Flux Flow Regime Model Errors APCT= -13*F l LICENSING BASIS PCT + MARGIN ALLOCATIONS PCT = 1945*F

+

_., > _ _ _ _ _ - --a- -..