ML12093A095

Initial Assessment of Pilgrim Safety Enhancement Program

ML12093A095
Person / Time
Site:	Pilgrim, EA-12050
Issue date:	04/02/2012
From:	Varga S Office of Nuclear Reactor Regulation
To:	Bird R Boston Edison Co
SECY RAS
References
Commission-1, RAS 22182, EA-12-050
Download: ML12093A095 (4)

Text

e Docket No. 50-293 Boston Edison Company ATTN:

Ralph G.

B i r d Senior Vlce President - Nuclear 800 Boylston Street Boston, Massachusetts 02199

SUBJECT:

INITIAL ASSESSMENT OF PILGRIM SAFETY ENHANCEMENT PROGRAM

Dear M r. Bird:

On July 8. 1987. Boston Edison Company (BEC ! submitted a detailed description o f the P i l g r i m Safety Enhancemtnt Program 9 SEP) t o the NRC.

This l e t t e r transmits the staff's i n i t i a l assessment Of t h i s program (Enclosure).

The s t a f f ' s i n i t i a l assessment has been conducted t o provfde an understanding o f the modifications and assess the safety sf(rnificance of those chanoes, when considered s i n g u l a r l y o r along w i t h other changes.

A d d i t i o n a l l y the-staff examined your evaluations of these changes and the BECo schedule f o r implementation of the modifications.

The staff's review fncluded a v j s i t t o BECo offices i n Braintree on July 22, 1987, conversations w i t h representatives o f your s t a f f over the past few weeks. and a meeting w i t h BECo representatives i n Bethesda on August 4, 1987.

The staff expects t o continue f t s dialogue w i t h BECo regardfng the SEP program a s part of i t s l a r g e r effort on severe accidents.

The generic issue o f containment venting has been under consideration by BUR owners and the NRc f o r several years.

It fs a complex issue fraught w i t h c o n f l i c t i n g safety objectives.

Because the severe accident effort i s ongoing. the s t a f f i s n o t prepared t o endorse the use of the Direct Torus Vent System (DLS) a t t h i s time.

To assist the s t a f f i n i t s consideratfon of the OTVS, we request you provide the

-r s t a f f your w r i t t e n response t o the questions contained i n the enclosure.

0 I n s t a l l a t i o n of the DTVS under the provisions of 10 CFR 50.59 i s precluded by.

the need f o r Technical Specifications On a containment i s o l a t i o n valve.

The s t a f f s t i l l has questions regarding the proposed modfficatlon t o the reactor core i s o l a t i o n cooling (RCIC system.

P r i o r t o implementing t h i s d

modification the s t a f f requests a t BECo conduct an assessment o f hydrodynamic loads on the R C I C piping and supports, based on the proposed exhaust pressure o f 46 psig, and make the r e s u l t s of t h a t assessment available t o the staff.

The s t a f f requests c l a r i f j c a t i o n regarding the function o f one valve i n the backup nftrogen supply system.

As described i n t h e enclosure, valve A0-4356 appears t o be a containment l s o b t f o n valve and, consequently, would be approprfate f o r inclusion i n the Technical Specfffcations.

Nov 14 05 11'54a p.1 I August 21, 1387 The s t a f f a r i f i c a t i o n regarding the

.L~oI: to the RHR system t o provide additional sources of water for RPV inje

'an and contafnrnent spray.

Thls modification may require a change to Technfcal Specifications.

AS described i n the enclosure, the valves to be a t. 1 t o the RHR system become part o f the reactor coolant pressure bounda y dur 4 operation o f the RHR system and, consequently, are subject t o surveillance tr.ing.

Ue comnend your efforts and leadershfp on t h i s

,gram.

The quallty of your

~ u l y 8, 1987 submittal i s impressive and the c

.>eration o f your staff i s appreciated.

As you are aware, the NRC wtll contfnue Its spection of SEP mfr'difications, review o f affected plant procedures, and of rvhticr! o f related onsite activities.

We w f l l keep you i n f o m d,

S'

.Id we have additional concerns about t h l s program.

Please contact the '. PI-aject Manager if you,have any questions.

Sincerely.

/5/

Steven A.

Varga, Dfrector Dlvision of Reactor Projects 1/11 Office o f Nuclear Reactor Regulation

Enclosure:

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Enclosure P INITIAL ASSESSMENT OF PILGRIft IANCEHENT PROGRAM Note:

Section numbers r e f e r t o Section nur' ',

i n t h e BECo submittal o f July 8. '1987.

1.

Sect. 3.2 - I n s t a l l a t i o n o f Direct.orus Vent System (DTVS)

The proposed design modificatio7 ssociated w i t h the d i r e c t ~.

torus vent system (DTVS) provldes a dlreci dent path from the torus a i r mace t o the main stack. I n p a r a l l e l w i t h

.d bypassing the Standby Gas Treatment System (SGTS).

The DTVS provides new 8" l i n e branching o f f the ex.isting torus purge exhaust l i n e betwee- ;he containment isolation valves (outside containment) w i t h a recahrrnction t o the e x i s t i n g torus purge exhaust l i n e downstream of the SGTS.

The new torus vent l i n e i s also provided w i t h i t s own containment i f e l a t i o n valve and a rupture dlsc, set t o r e l i e v e The i n s t a l l a t i o n r an additional branch l i n e and containrent 5rn.d-L..

k..-CC PC(+,

i s o l a t i o n valve ~ o u l d require a change t o the p l a n t Technical L *k.%

~ ~ e c i f i c a t i o n s. Therefore, i t i s our view t h a t i n s t a l l a t i o n of the DTVS Y r,h.

lfi,l cannot be fmplemented under the provisions o f 10 CFR 50.59.

IZ-To assist the staff i n i t s consideration of the proposed DTVS. we reouest a w r i t t e n response t o the following concerns:

11 Provide comprehensive analyses of accident sequences, w i t h t h e i r e s t f m t e d frequency of occurrence, f o r which the vent would be c a l l e d upon t o operate.

2)

Provide estimate of the fraction of those sequences where the vent would be operated but where the accident would have been termfnated short o f contalnrnent f a i l u r e without vent operatfon.

Consider the following situations i n the accident sequences:

(a) e l e c t r i c power returned t o service (b) equfpment returned t o service (c) rnls-diagnosed s i t u a t i o n corrected by operators

3 1 P r ~ ~ v i d e comprehensive analysis of t'o52 accident sequences that:

( a )

could be itIIpr0ved by correct.se of the vent, or (b) could be i n i t i a t e d o r made Jrse by incorrect operatfon of the vent.

L.

4)

Provide analysis of sequent that could lead t o containment f a i l u t e

,T) by operation of the vent itowed by excessive pressure d i f f e r e n t i a l (buckling).

5 )

Provide analysis of

~e probability of vent f a i l u r e when called upon.

6) Provide analysis of maintenance o r surveillance errors on the vent system t h a t could induce accidents.

7 )

Provide an estimate of the radioactivity released for a l l sequences when the vent could be opened, including both correct usage according t o procedures and incorrect usage due t o human error o r equipment malfunction.

2.

Sect. 3.3 - Containment S ~ r a v Header Nozzles The objectfve of i n s t a l l i n g new containment spray header nozzles i n the dryuell i s t o improve the performance of drywell spray under severe accident conditions and t o provide greater f l e x i b i l i t y o f use o f the sprays under a variety of accident conditions.

The replacement spray nozzles ark identical t o the existing nozzles excep'i that the replacement nozzle assemblies had a l l 7 nozzle outlets open.

The effect of capping I nozzle a s s e d l y has 6 out o f 7 nozzle outlets capped while the origfnal,

nozzles i s t o reduce drywell spray flow when the spray water i s provided by the RHR pumps (5000 gpm) and Preserve a basic spray pattern when the spray