ML19095A644

LER 1976-002-00 for Surry Unit 1 Inaccurate Thermal Transient Analysis of Worst Break LOCA Core

ML19095A644
Person / Time
Site:	Surry
Issue date:	03/26/1976
From:	Stallings C Virginia Electric & Power Co (VEPCO)
To:	Moseley N NRC/IE, NRC/RGN-II
References
LER 1976-002-00
Download: ML19095A644 (3)

Text

ee VIRGINIA ELECTRIC AND POWER COMP.A.NY RIOHMOND, VIRGINIA 23261 March 26, 1976'.

Mr. Norman c. Moseley, Director Office of Inspection and Enforcement

u. s. Nuclear Regulatory Cormnission Region II - Suite 818 Docket No. 50-280 230 Peachtree Street, Northwest License No. DPR-32 Atlanta, Georgia 30303

Dear Mr. Moseley:

Pursuant to Surry Power Station Technical Specification 6.6.2, the Virginia Electric and Power Company hereby submits forty (40) copies of Re-portable Occurrence No. AO-Si-76-02.

The substance of this report has been reviewed by the Station Nu-clear Safety and Operating Cormnittee and will be placed on the agenda for the next meeting of the System Nuclear Safety and Operating Cormnittee.

Very truly yours,

c. M. Stallings Vice President-Power Supply and Production Operations Enclosures 40 copies AO-S1-76-02 cc: Mr. Robert w. Reid, Chief Operating Reactors Branch 4

,LIME, AO-Sl-76-02 EVENT REPORT CONTROL BLOCK: I [PLEASE PRINT ALL REQUIRED INFORMATION]

1 6 LICENSEE LICENSE EVENT NAME LICENSE NUMBER TYPE TYPE 7

@El 8 9 I vi Al slP ls.l..iJ 14 I o I o 1-1 15 ol o Io I o I o 1-1 oI 25oI 14 26 Ii I 111 lo30I Io 31 I 132I REPORT REPORT CATEGORY TYPE. SOURCE DOCKET NUMBER EVENT DATE REPORT DATE

@ElcoN'T I MI 1 I lIJ L!J I oI s I o I~ Io I2 1.s Io I lol311!3l7l61 lol3!2l6!1l6I 7 8 57 58 59 60 61 68 69 74 75 80 EVENT DESCRIPTION

!0!2! I The worst break LOCA core thennal transient analysis is inaccurate in that it does 7 8 9 80

@@] I not include the effects of steam generator tube plugging. This is reported pur- I 7 8 9 80 joj4j I suant to Technical Specification 6. 6. 2 *. a. 8 (A0-S1- 76-02) I 7 8 9 80 rn 7 8 9 80

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7 8 9 PRIME 80 SYSTEM CAUSE COMPONENT COMPONENT CODE CODE COMPONENT CODE SUPPLIER MANUFACTURER VIOLATION 1°171lz I z I LFJ 7 8 9 10 11

!HIT IE Ix I cl HJ 12 17 ULl 43 lw!i!2!ol 44 47 w48 CAUSE DESCRIPTION

@Jfil  !steam generator tube deterioration has resulted in the need to plug a number of tubes 7 8 9 80

~ lin Surry steam generators. Surry Unit No. 1 has 5.19% of its steam generator tubes I 7 8 9 80

• 7IT@8 sI plugged, and Surry Unit No. 2 has 3. 37% of its tubes plugged. The cause for (cont'd)

---"~-=a<..-.----------'-----'80 I

FACILITY METHOD OF STATUS  % POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION 7

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9 Io 10 Io I o12I 13I NA 44 w45 46 NA 80 FORM OF ACTIVITY CONTENT rn w RELEASED OF RELEASE AMOUNT OF ACTIVITY LOCATION OF RELEASE 7 8 9 WI 10 11 NA 44 45 NA 80 PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION ITEi Io I oI ol W 1

--=NA;.;;.___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _-....J 7 8 9 11 12 13 80 PERS'ONNEL INJURIES NUMBER DESCRIPTION EEi Io I oI ol ~N_A_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _--'

7 '8 9 11 12 80 OFFSITE CONSEQUENCES liJaj  !*There are no offsite consequences associated with this event.

7 8 9 80 LOSS OR DAMAGE TO FACILITY TYPE DESCRIPTION Glsl_

~~ sW NA 1'-0--------------------------------------------sb j

PUBLICITY IT08 9I. . N . . , _ , A ~ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 7 80 ADDITIONAL. FACTORS EJfil I The nuclear steam supply system vendor bas recently perfonned a LOCA analysis to j.

7 8 9 80

~ I examine the effects of plugging 6% of the steam generator tubes on each Surry unit. I 7 8 9 80 NAME: _ _ _E_._"t-_1_._S_\_ve_e_'n_ey;:....c..,_J_r_.__________ PHONE: (804) 357-3184 GPO S 61

• o 67

CAUSE DESCRIPTION (CONT'D) ee steam generator,tube deterioration at Surry has not been isolated. The nuclear steam

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supply system vendor is conducting exhaustive research into this generic problem with PWR steam generators.

ADDITIONAL FACTORS (CONT'D)

The major effect of the plugged tubes occurs during the* reflooding phase whereby increasing loop flow resistance results ih decreasing flooding rate.

The approved ECCS Evaluation Model (March 15, 1975 version) was used to perform the analysis using the sequence SATAN/WREFLOOD/LOGTA. The resulting peak clad temperature for 6% plugged tubes was 2142°F using the current technical speci-fication F0 limit of 2.1. These results show that the ECGS criteria, peak clad tem-perature 2200°F, are met for Surry Unit Nos. 1 and 2 with the inclusion of 6%

plugged tubes.

Therefore, the health and safety of the general public was not affected by this occurrence.

Follow up analysis is being conducted by the nuclear steam supply system vendor. This analysis will define the allowable percentage of steam generator tubes that may be plugged in each Surry unit. A supplementary report will be submitted when the results of this analysis are known.