ML17179B059

Discusses Use of Shex Computer Program & Ansi/Ans 5.1-1979 Decay Heat Source Term for Containment long-term Pressure & Temp Analyses

ML17179B059
Person / Time
Site:	Dresden
Issue date:	07/13/1993
From:	Thadani A Office of Nuclear Reactor Regulation
To:	Sozzi G GENERAL ELECTRIC CO.
Shared Package
ML17179B060	List: ML17179B059
References
NUDOCS 9309020124
Download: ML17179B059 (5)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION W~61'Uf4U10N. o.c. :os"'"°°°'

Mr~ Go.ry L. Sou1 *::oManagar Technical Services~*

Gineral El ectr1c: Nuclear £nergy

• 175 Curtne~ Avenu**

San Jose. Ca11for:nia 95125

Dear Hr. Sozzi:

.JW.y 13, 1993 P.2/15

SUBJECT:

USE Of SHEX COMPUTER PROGRAM ANO ANSI/ANS 5.l-1979 DECAY HEAT SOURCE TERM FDA CONTAIHMENT LONG:""TERM PRESSURE AND TEMPERATURE ANALYSIS I

~our ~arch 12, 199l latter reQuested that the staff clarify the requirements for 'tt:~ usage of the SHEX computer coda and ANSI/ANS 5.1-1979 decay heat model in the lna1ys1s of long-term containreent pressure and temperature response to Los*s-of... Cao1ant-Accidents (lOCAs).

As part cf the gener;c BotHng Water

..<eact;;r-(BW~) power uprate program, the staff auproved the use of SHEX (and the ANS S.l deeay*heat raodel) on a plant~spet1ftc basis, provided that confirmatory c.aleulat1ons for validation of the results were included 1n the plant-specific:: reqLlest.

Subsequent 1 y, the staff has expanded that approval to 1nclude all SWRs Wh1c:h have a neeo to update tt!eir containment pressure and temperature ana1Y~9s.

Due to the wide range of -possible 1 r.put assumpt1ons and mode111 ng options

. available wheri usfng the cod~. and* the. ccrrespo~dingly w1de range of potential results o:>tainable when using the cot:e.. the staff has chosen not_ to review and Jpprove ~HEX fer gener;c use.

However, this code can.be used on a plant-

pec-

fic 04$lS by*'those licensees ;.,ishinq ta U$e tt for eHher docketed i1cer.sir.g corresp~ndence or 10 CFR 50.59 evaluations.

tle woul: lHce ta:t)c1nt out that a plant mod1fkat1on mace based uoon the t"esults cbtain~d using SHEX couid'fotroduce an unreviewed safety question.

The staff beihV9$ that license~ Safety Evaluations supporting changes made pursuant ta 10 CF~ 50.S9 uslng SHEX*as part of a new conta;n~ent evaluation.

should i~clude a benchmark analys~s* performed using both SHEX and the prev.1ous coae {:f known), as well as an evaluat1on of any input assumotion* or parameter changes ~ade fram*the analys1s using the previous* cod~.

Your ~taff has also requested d ari ficat.1on of the staff's.reQuirements for the use of a zq $tatist1cal uncertainty when us1ng the ANSI/ANS 5.l-1979decay heat r::~ael when performing c~ntainment evaluations. The staff agrees wtth yµur assert1on t~t the ANSI mcae~ contains adequate conservatisms such that

• the *JsS *..:f an add5tiona1 uncertainty t;en11 may not be necessary.

However, we w\\11

--~iy on indiv1dual ncensees to r.iak*e the determination of what, tf any.

uncH'tl1rty terni heeos tobc usea o;o maint:iin cons1stency '1'1th other analyses.

I t

1~,~}D (f1}-

~

~***.'*.****JRN 17 *,97 11=10AM GE NA:-Qk> ENERGY JUJ.y J..;,

-J-~

P.3/15

. Mr. ~ary L. :iozzi ~ I trust t~at th1s letter aaeQuately expresses the staff ~os1t1on on the u~e

.*~or t::a SHE.l computer cade and the ANSI/ANS S*;J-1979 *decay heat model.

If you

!'lave any quest~ans., p1ease contact J~: ~udrick of _my staff at (301) *so4-2B7L

.., I.

• t..

• ~*

S1ncer ly,

.,row~-

Ash -Thadan1 ;'(Q,~rectol:

01V s1on of Systems Safety and Analysis Off e of Nucla'ar' Reactor Regulat1on.

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I

. Attachment 2 Graphs of Available and Credited Containment Overpressure

• 25 20 Cl

'iii S: 15

~

J en en

~

Q. 10 c

Cl.I E

c s 5 c

0

(.)

0

-5 (After 10 minutes: CS@ nominal flow, LPCI throttled to 5000 gpm/Hx)

\\ \\

Pool Pressure Available

\\

Credited Pool Pressure

---

-- --- :\\

I I\\.

I ~

I - -

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10 100 1000 Peak PCT 10 minutes

(< 200 sec)

Reflood

(< 300 sec)

Time (sec) 10000 DRESDEN STATION UNITS 2 & 3 100 obo MINIMUM CONTAINMENT PRESSURE AVAILABLE AND CREDITED CONTAINMENT PRESSURE FOR PUMP NPSH FIGURE 1

(After 10 minutes: CS@ nominal flow, LPCI throttled to 5000 gpm/Hx) 25 20

.~

UI Q. 15 I!:!

s UI UI I!:! 10

a.

~------------- - - --- -

c I

QI E c

---~~

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'iU 5

c 0

...-~-

I u

L 0

-~

-5 10 100 1000 Peak PCT 10 minutes

(< 200 sec)

Reflood

(< 300 sec)

Iii Pool Pressure Required -

Core Spray

• Pool Pressure Required -

LPCI Credited Pool Pressure Time (sec) r---

--.~-7::-

10000 DRESDEN STATION UNITS 2 & 3 100 ODO CREDITED CONTAINMENT PRESSURE FOR PUMP NPSH FIGURE 2

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