ML20039D273

LER 81-056/99T-0:on 811208,possible Error in LOCA Analysis Found Which Could Have Permitted Less Conservative than Assumed Reactor Operation.Caused by Exxon Nuclear Co Failure to Perform Reanalysis of Small Break Loca.Explanation Encl

ML20039D273
Person / Time
Site:	Cook
Issue date:	12/21/1981
From:	Palmer R INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20039D268	List: ML20039D267 ML20039D273
References
LER-81-056-99T, LER-81-56-99T, NUDOCS 8112310480
Download: ML20039D273 (4)

Text

-

LICENSEE EVENT REPORT

. *C NTROL BLOCK: l 1

l l l' ,

lh 6

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) to lil*l F 8 9 M I ILICENSEt' I D l COoE C I c I1411@l 15 0101010101010101010 LICENSE NUMBER lo26l@l411 26 11 1111 LICENSE TYPE JOl@l61 C A r b8 I l@

> CON'T 10111 "L' e'"E LL_Ql 0 l 510 l 010 l 3 l 1 l 685 l@l 1 El DENY 2 l OATE 018 l 8 l 1 l@l lREPORT 75 12 lDAT 2 El I l 811 80 l@

) 8 60 66 DQGEET NUMBER 69 le TVENT DESCRIPTtON AND PROBAB'LE CONSEQUENCES O'o 10 l 2 l l, DURING NORMAL OPERATION, PLANT PERSONt4EL WERE NOTIFIED BY AEPSC 0F A POSSIBLE ERRORl ,

IN THE LOCA ANALYSIS WHICH IS THE BASIS FOR THE FQ TECHNICAL SPECIFICATION, 3.2.2, i lo i3i i io;[ilWHICHCOULDHAVEPERMITTEDREACTOROPERATIONINAMANNERLESSCONSERVATIVETHAN l THIS OCCURRENCE WAS THE FIRST.0F THIS TYPE. l ioisi l ASSUMED IN THE ANALYSIS.

l iO is i l (SEE SUPPLEMENT) l 10171 l I

10181 l C DF COCL SLBC E COMPONENT CODE SUB D'E SU E ITITI l Z l Z l@ l X i@ [Z_l@ l Z l Zl Z l Zl Z I Z l@ W@ [Z_j 20 7 8 9 10 11 17 13 18 19 ggp po EVENTYEAR RE OR CODE N O arg 18 il l _ 26 22 l-l 23 lo l5 l6 l 24 26 M

27 l 9l 9l 28 29 LT_j JJ

[---j 31 l 0l 32 K N AC ON ON L NT 1T HOURS S8 iTT FO 8. SUPPL MAN FACTURER L EJ @34LZJ @ lZl@ LZ_j@ l 0l 0l Oi 01 LYj @ l42N l@ [Z_j@ lZl91919l@ 4; 32 36 4 3/ 40 41 43 44 CAUSE OESCRIPTION AND CONRECTIVE ACTIONS h Iil0ll EXXON NUCLEAR COMPANY (ENC) DID NOT PERFORM A REANALYSIS OF THE SMALL BREAK LOCA.l 1, li t i SUBSE0 VENT CORRESPONDENCE FROM ENC INDICATES THAT A SMALL BREAK ANALYSIS WAS NOT I i,i2i lNECESSARY. ACCORDING TO ENC THE INCREASE IN FQ LIMIT AT THE TOP 0F CORE IS JUSTIFIED:

l

1. ii3l l AS (hERE IS SUFFICIENT PEAK CLADDING TEMPERATURE MARGIN IN THIS REGION.

l pl l (SEE SUPPLEMENT) l

2EY S seOwER OTsE R STATUS @ EisSURv' O SCOvERv oESCRipTiON @

li Is l [E_J@ ll 1010 l@ln NA j 44

[D l@l NOTIFICATION FROM AEPSC e- 80 l

i

' ' i2  %

ACTiviiv C5 RENT '

RELE ASED OF RELEASE AMOUNT OF ACTIVITv LOCATION OF RELE ASE

' [d6j [Z,] @ [Z_j @ l, NA l 'l NA l

' pERSONNe"t ExpoSOES N' ' VB E R DESCRIPTION ,

1 i I 7 I [0_[ tlj' 0]@. TYPE l Zl @l NA l 9 -

' pE/ziNNEt i

iNau'R'iES  %

NU esER 1

t s 8 :9' 10101 Ol@lOESCRiPTiOs@NA 11 12 V' 80 l

~

e '#,i ' " f*CT,'Tio'y '^"'* @ N ,

I i 9

'lZl@lO NA . . ,

80 av ' "' ' '

I issue oESCRIPTION '.@~'[ ~ 5'8112310400 811221 '

i NRC USE ONLY F'DR ADOCK 05000 '

u : nl LN_[@l _

NA S.- l lllllllllllllf 1 9' 9 to

~

G8 69 80 5 PHONE:

616-465-5901 2, NAME OF PREPARER V -

"W-f ,

a - ,

, s ATTACHMENT TO LER# 81-056/99T-0 i

SUPPLEMENT TO CAUSE DESCRIPTION' ,

' g:

, JUSTIFIC4 TION FOR USE OF CURRENT K(z) FUNCTION FOR D. C. COOK UNIT'l In early 1981, Exxon Nuclear' Company. (ENC) performed large break LOCA analyses for; O D.' C. Cook Unit 1 using the ENC-WREM IIA PWR ECCS Evaluation Models(I) . The results 1[ of these analyses showed that the allowed total peaking, Fq, could be increased by 6 to 8% and still- remain within the NRC ECCS criteria. The increased F q as a func-

?# tion of exposure was implemented in the D. C. Cook Unit 1 Technical Specifications.

Also contained in the D. C. Cook Technical Specifications-is an axial peaking _ func-

, tion K(z) which is normalized to the maximum allowed Fg (2) . The-ENC large break analyses performed support-the allowed increase in F q over the bottom eleven feet

' ;of the twelve-foot long D. C. Cook Unit 1 core.

iV. y

\ .

The topcone-foot'of the core has-peaking. limits established based on small break ECCS r _.

I# '

analyses. Since ENC has not performed small' break analyses for D. C. Cook Unit 1, j thebasisforthepeakinglimitinthisregionremainsthesmallbreakanalysisper-I formed by Westinghouse and reported in the D. C. Cook Unit 1 FSAR(3) . ENC believes that sufficient margins exist in the kestinghouse small break results to justify the

- 2 use of the existing _K(z) function with the ENC increased qF mul tiplier.

If Examinatior 4 thenreported sm l1 break results for D. C. Cook Unit 1 reveals that

' the' allowed axial peaking limit results from a very conservative application of the

<' Specifically, the calculated worst small break was a 6-inch

$small' break ECCS models.

- break which gave a i:alculated peak cladding temperature (PCT) of 14930F, based on

~~

'I f - an ECCS analysis performed at 102% of " Engineered Safeguards Design Rating Power" t (3382MWt). The licensed thermal power is 3250 MWt. The quoted peaking factor at

( s.- ' license rating was 2.32. Clearly, the calculations were performed at a' conservative y - ,

q ,

u e . . _  %

I t .e ",

h 1'_I._______m_-; ._fi___.____h.__ .__._________ _/ f_,

, ATTACHMENT TO LER# 81-056/99T-0 power level-and yielded PCT values well .below the allowed 2200 F maximum.

The current combination of the' ENC total peaking and Westinghouse K(z) raised the allowed peaking including the topmost ore-foot of the core smal' break region.

However, this small increase in peaking will increase the worst break temperature rise (PCT-Tsat) approximately in proportion to the peaking increase. Since the-minimum pressure during the temperature transient is about 300 psia (T sat- = 4178 F),

the temperature rise (1493 - 417 = 10760) could be increased b3 3% to ll620F, thus giving a PCT of about 15800F. Clearly, a small peaking increase of this order of magnitude can be readily accommodated within available PCT margin in the small break results.

4 The degree of- conservatism contained in the D. C. Cook Unit 1 small break results -

is further borne out by the more recent Westinghouse calculated small break results for D. C. Cook Unit 2, which is a twin NSSS system to D. C. Cook Unit 1. These results showed PCT's of 1668'F for operation at 3391 MWt, and allowed total-peaking substantially higher than those in the current D. C. Cook Unit 1 Technical Specifications.

As a result of notification of a possible non-conservative Fq limit in the top -

of core, a temporary change sheet was written to 1 THP 4030 STP.330 (Surveillance of Core-Power Distribution Limits) lowering the qF limit to the value used in the previous cycle. A reanalysis of the most limiting full core flux maps for this cycle was. conducted using'the conservative0F limit. The reanalysis indicated no. violations. Subsequentto receint of ENC's explanation for the justification of the higher F qlimit, the aforementioned temporary change sheet was cancelled.

i

. ATTACHMENT TO LERf 81-056/99T-O' e i .

r

} -

REFERENCES:

-(l) Exxon' Nuclear Company, "LOCA ECCS Reanalysis. for 3. C. Cook Unit i using -the ENC WREM IIA PWR ECCS Evaluation-Model",

XN-NF-S1-07, February 1981.

(2) "D. C. Cook Nuclear Plant Unit 1 Technical Specifications Appendix 'A' to License No.-DPR-58", Figure 3.2-2.

(3) Donald C. Cook Final Safety Analysis Report (Amendaent. 56)

Pages P.1-3 through P.1-7 and Figure P.1-1 through P.1-llb,

' September 1974.

9