ML20210J437

Discusses 970717 Licensee Ltr on 10CFR50.46 30 Day Rept of Significant Changes to Accepted ECCS Model for Units 1 & 2. Info Faxed from Licensee Encl

ML20210J437
Person / Time
Site:	South Texas
Issue date:	08/12/1997
From:	Alexion T NRC (Affiliation Not Assigned)
To:	NRC (Affiliation Not Assigned)
References
NUDOCS 9708180086
Download: ML20210J437 (25)

Text

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August 12, 1997 NOTE-TO:

PD IV-1 File FROM:

Tom Alexion ORIGINAL SIGNED BY:

Project Directorate IV-1 Division of Reactor Projects III/IV

-Office of Nuclear Reactor _ Regulation

SUBJECT:

LICENSEE'S JULY 17, 1997. LETTER ON 10.CFR 50.46 THIRTY DAY REPORT OF SIGNIFICANT CHANGES TO THE ACCEPTED EMERGENCY CORE COOLING SYSTEM MODEL, SOUTH TEXAS PROJECT, UNITS 1 AND 2 During my absence from the' office on' July 31, 1997, the backup-Project Manager

- and the Reactor Systems Branch reviewer had 'a call with the licensee on-the above subject.

The attached information was faxed _ from the_-licensee prior to the phone call to focus the discussion.

As a result of the call and comments from the staff, the licensee indicated that they would revise the subject report and formally submit it to the staff.

Docket Nos. 50-498 and 50-499

Attachment:

Fax from licensee

' DISTRIBUTION:

Docket File-PUBLIC (PDR)

JClifford TAlexion Document Name: STP5046.N0T OFC-PM/PD64Ti$h NAME TAlexionk DATE

/97 COPY (YE}/N0 0FFICIALWCORD COPY

/

1 9708180086 970812 PDR ADOCK 05000498 P

PDR I

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pn na:q%

umso m.

j NUCLEAR REGULATORY COMMISSION.

wAswinovow, o.c. sosewoo$

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August 12, 1997 NOTE TO:

PD IV-1 File i

A h om Alexion FROM:

Project Directorate IV-1 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation

SUBJECT:

LICENSEE'S JULY 17, 1997, LETTER ON 10 CFR 50.46 THIRTY DAY

(

1 REPORT OF SIGNIFICANT CHANGES TO THE ACCEPTED EMERGENCY CORE i

COOLING SYSTEM MODEL, SOUTH TEXAS PROJECT, UNITS 1 AND 2 i

During my absence from the office on July 31, 1997, the backup Project Manager i

and the Reactor Systems Branch reviewer had a call with the licensee on the above subject.- The attached information was faxed from the licensee prior to l

the phone call to focus the discussion.

As a result of the call and coments from the staff, the licensee indicated that they would revise the subject report and formally submit it to the staff.

I Docket Nos. 50-498 and 50-499

Attachment:

Fax from licensee I

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South Texas SBLOCA Analysis - AOR i

Reconstitution s

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E July 1997 9a

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d July 29,1997

- South Texas' AOR Reconstitution 1

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l Purpose a

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discuss the STP SBLOCA reana ysis-o

'wlich is the basis for recent submittals1:o :1e h 9C:

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- 10 CFR 50.46 report 9

- Proposed Tech Spec change i

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July 29,1997 South Texas AOR Peconstitution 2

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-w....ii....,.in 4

er Introduction / Background

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a The SBLOCA Analysis' of Record (AOR) was recerr:ly "reconstitu::ed" (reanalyzed?

The recons 1:ituted AOR, waich wil; be directy a

8 substitlJ:ed for the current AOR in te S"o JFSAR, is based on the same basic models a

l

. and assumptions as the current JFSAR.

analysis 8

h July 29,1997 South Texas AOR Reconstitution 3

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Introduction / Background

~

a

\\OTRL'MP Evaluation IVode. (EM? clanges l

since the L FSAR analysis were included in the reconstitutec AOR or.evaluatec' on a plant-specific aasis, as appropriate-8 Asymme': ries resulting " rom 11e unique Sou':n g

i Texas design were evaluated to reaf"irm 1:ne conservatism of the SBLOCA results repor:ec in ':1e UFSAR with explicit considera': ion of y

f:he unic ue STP design features

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d July 29,1997 South Texas AOR Reconstitution 4

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4 a

a Basis for Reconstitution

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Preliminary SBLOCA studies in support o" :he A94 RSG suggested a reevaluation o" tie unique STP design features i

Similar c uestions were raisec' rela:'ive to the g

AOR, warranting some stucy to affirml:he-

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continuec' applicability / conservatism o" :he UFSAR analysis E

8 En k

July 29,1997 South Texas AOR Reconstitution 5-

G

,9 i

8 Basis for Reconstitution

E

,2 Given the expected differences shown ' y a

preliminary runs, it was decidec that a reanalysis (AOR reconstitutionJ wou d ae s

more appropriai:e than evaluating the indivic ual APCT ef"ec:s "or :he various l

mode.ing 4eatures, and a33 lying the results to t1e current UFSAR analysis 9

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d July 29,1997 South Texas AOR Reconstitution 6

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STP Design Versus Typical i

4-loop Plant South

, exas has.a unique plant configuration i

compared to a typical Westinghouse 4-loop NSSS design

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E

- 14 foot core

- One loop wit' no ECCS a

1

- Unheaderec ECCS 1

- Safety-grade SG PORVs

- No safety-grade clarging delivery on an SI E

actuation signa

- Unheadered'AFW (assuming no operator action).

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d July 29,1997 South Texas AOR Reconstitution 7

V 8

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STP Design Features

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lese desig n fea:ures were evaluatec to ensure both an accurate modeling o" :le STP design, anc appropriate conserva:: isms g

consistent with regu'ai:ory requiremen:s i

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E 8

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July 29,1997 South Texas AOR Reconstitution 8-

fn-I Scenarios i

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2 The combinations of single failures of "he (unheadered) ECCS equipment, (unheadered} AFW, anc' 3ORVs, along with

!ocations for the broken loop (for 30th S1 in a

the broken loop or no Si in ':he broken loop},

[

ead to identification of multip e SB _OCA scenarios

= Unique to S P

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S

- Required careful consideration / study to establish the appropriate limiting scenario 9

d July 29,1997 South Texas AOR Reconstitution

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2

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Asymmetry l

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~"ie significant asymmetries resulting " rom

ae various scenarios required multiple intact loo as for aaproariate mode'ing-e g

-~he AOR reconstitu': ion includes three Joops j

(one broken, one unlumpec' intac': & one i

um aed intact} to ca31ure the effects of asymme::ry. This is consistent with the curren: UFSAR analysis 8

IR 5

hd July 29,1997 South Texas AOR Reconstitution 10

f i

1 Typical 4-loop ECCS i

e f&

ACC A ACCB l

Pumped SI Train A l

SGA o

e SGB 3

Prr L

1 i

SGO l SGC i

9 Pumped St Train B g

ACC D ACC C h

I July 29,1997 South Texas AOR Reconstitution 11

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STP ECCS a

u 1

in Pumped St Train A Neped St Tesin B O

O HHSI HHSI

( ACC A )

( ACC 8 )

LHSI N-LHSI POHV A PORYB E

AFWTrainA A; W Teafn 5 (Prosauffreth PORYD PORV C SGD SGC AW/ Trafn D AFW T* C q

[ Accc }

m ms y

P% si T<.in c h

July 29,1997 South Texas AOR Reconstitution 12 1

5 l

Modeling Features

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i T1e '4 foot STP core was explicitly moc'elec' One loop wi"h no ECCS, unheaderec ECCS, and unheadered AFW were addressed-j

hrough explici': calcu'ation of fle various-scenarios to establisi the limiting case i

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8 si k

d July 29,1997 South Texas AOR Reconstitution 13

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Modeling Features.

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= Safety-grade SG PORVs were modeled in the SBLOCA studies after ciscussion wih FL&P

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- Assumed to be in automatic mode

- Mocelec' in NOTRUMP in the same way as the

,j atmosp1eric relief described in t7e model topical 3

(MSSVs), including conservative application of f

uncertainties and consideration of limiting single failures y

• t Charging flow was not assumed since STP g

has no safety-grade c7arging deJivery on an Si actuation signal h

July 29,1997 SouthTexas AOR Reconstituilon 14

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Modeling Features

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Si in ~:ae broken loop was not exp icil:ly inc,uded in the case calcu ation

- moc'eling. imitations in the 3-loop (i.e.., current E

UFSAR1 model E loop model was used as an evaluation tool to a

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assess PCT effects of Si in the. broken loop

- evaluated effects were applied to tie base results (as in the current AOR) 8

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d July 29,1997 South Texas AOR Reconstitution 15

8

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Modeling Features l

2

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l COSI condensa: ion model was includec in l

base calcu.ation anc assessment of Siin the oroken oop e'fects, a" hough system j

j aressures calculated for the imiting 2" ec uivalent c.iameter break severely imited a

l benefits o" this model A saectrum of breaks was analyzec, aased 9

on current plant peaking " actors, core power, L':

etc., as reflec:ed by the plant Tech Specs and gj current UFSAR SBLOCA analysis N

July 29,1997 South Texas AOR Reconstitution 16

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a Limiting Scenario

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l Based on t1ese s":ucies,':he imiting scenario was "ound to be:

- Break in 1000 B

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- Common moc'e failure (loss of an emergency ciesel generator) !eads to 'oss of:

• TDAFW to loop D (assuming no operator action) c*

• MDAFW to loop A

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HHSI to loop A, and 9

• Loop A & D sG PORV (assuming no operator action) 8 h

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July 29,1997 South Texas AOR Reconstitution 17

.i...i.,....,,,-,,i.i..

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i Limiting Scenario fo'r STP s

g Application i -

Psmped St Tenh a

{

4 O

i Brook g

( ACC A j

( ACC8 )

POW 5 g

n f

AFWTsch 8 4

c P.-_ )

1 f

s\\p 1

i 5

m Si Pwaped St Treh C July 29,1997 South Texas AOR Reconstitudon 18

1 8

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Results - AOR Reconstitutior a

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l 1.51n l

2in 3 in Peak Clad Temperature, F 1464 1671 1969 Elevation, ft 13.75 13.75 13.00 Maximum Local Zr/H O Reaction, %

1.45 1.89 0.05 2

8 Elevation,it 13.75 13.75 12.75 f

Total Zr/H O Reaction, %

< 1.0

<1.0

<1.0 2

Hot Rod Burst Time,see N/A N/A N/A g

Elevation, ft N/A N/A N/A P CT, 'F W/O BL SI 1670A sj i

(3 Loop)

W/ BL SI 1806.2 h

(4 Loop) h N

July 29,1997 South Texas AOR Reconstitution 19

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8 Results

- AOR Reconstitution E

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Revised Licensing Basis PCT (SBLOCA Reanalysis PCT) 1671 F i

l Impact of ZIRLO Cladding

+

1F i

Safety injection into the Brokerr Loop

+136 F g

Cold Leg Temperature Measurement Uncertainty

+ 20 F 5

Burst and Blockage / Time in Life Penalty

+ 30 F h

Error in VERITRACK Transmitter uncertainty

+2 F I

ij Future Licensing Basis PCT + Margin Allocations 1860 F Previous PCT result 2158 F 3

et changein SBLOCA PCT

-198 F 8

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d July 29,1997 South Texas AOR Reconstitution 20

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Plant / Licensing Changes IE "ech Specs j

- As a result of the changes in tie AOR, only one spec was identified for modification - TS 3.7.1.6, 8

SG PORVs

• To ensure that the SG PORVs rernain in automatic g

during Mode 1 & 2 operation N

- Typical operating mode, but not identified in TS

- Consistent with SB analysis, and conservative compared to expected operator action times

= To clarify the TS BASIS, which already included g

SBLOCA I

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July 29,1997 South Texas AOR Reconstitution 21

l e

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Plant / Licensing Changes i

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Tech Specs (continued)

- Adds new surveillance requirement to perform channel calibration every 18 months S

- Administrative controls currently in place pending Tech Saec Amendment aparoval B

I y

8 X

July 29,1997 South Texas AOR Reconstitution 22

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s Licensing Cons.derations -

i

.Il-AOR I

50.46 r,

- Since results of the AOR reconstitution produced effects > 50 F, these changes have been reported, j

E as required, under the 1~0 CFR 50.46 30-day clock l!

(submitted July 17,1997) l[

• L!FSAR i

- The AOR reconstitution will be included in the STP UFSAR, replacing the current SBLOCA analysis information in Section 15.6. Implementation of this i

g change is scheduled for late 1997 l

3 h

July 29,1997 South Texas AOR Reconstitution 23 s

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