ML20236F507

Provides Followup to 871021 Telcon & Re Containment Safety.Nrc Continuing to Develop Resolution to Issue of What Improvements Needed for BWR Mark I Containments.Planning Milestones Listed

ML20236F507
Person / Time
Site:	Vermont Yankee
Issue date:	10/23/1987
From:	Murley T Office of Nuclear Reactor Regulation
To:	Tarrant G VERMONT, STATE OF
References
NUDOCS 8711020174
Download: ML20236F507 (2)

Text

vi u < y ,,.y , .y -

..A

%,pvg, , , ;g ;

>g_,_,

-y Q

• f,l. <) < 114 - ,

u3 n;\ y:p _ , ', , ,

7)

. v32 s 7-

--en w m 4 3 e <

c g . . , -

q;gg < , ,

vu r ,

J-

,s' ;n

. jfg r _

d, g& y ,

[ h fh .  : UNITND SYATES ' M ' N J' ,

[

4 cE-

' NUCLEA'R REGULATORY COMMISSION :

' WASHINGTON, D; C 20665 , -'

l kWe[

r I

(

. v.

' 00T13 407 mi

', s

~,. -

.< ^ n 9 y;m

' bi sitr. Gerald & Tarrant, ComissionerL' ' '

M iState of' Vermont 1 M Department'of Public Service' > ,

"' a 120 State Streett j State Office Buil_ ding . ... .

1

~

W 4

-Montpelier,.VermontJ 05602.'

M

, , ~ ,

Dear.Gerry:

m B

' This is a follow-up to our telephone conversatiioniofL0ctober).21?andlyourj N - -

letter;to me' dated September 1, 1987, regarding containment lsafetye '~

, < %g i

iWearecontinuihgto.developia;-resolutiontojhe51ssuefofl:whh11mprovement's) are needed for BWR Mark 11 containmentstof.the' type:found at~~ Vermont Ya'nk'ee.: *

((I >

i

.Last ~ year the NRC, under the leadership of Mr. Harold 'Dentoniand.Mr. Robert: -1 Bernero,. had proposed several improvements; to, Mark?IJcontainmentif that wepe e thought;to provide edditional assurance that thel consequences.oftaLsevere'co s .

1 L.

damagiaccident would. be substantially mitigated. ! After a; goodideal-;offstudy'.

and' peer review,-they concluded last'Aprilethat' "On-the~one handFtheilndu.stry.: , *

analysts say that changestare not justified'.70n theLother hand the Researchi . q scientists-indicateithat the changes are'no_t effective'.." >In other.words, the.L 1 technical consensus on the proposed improvements) evaporated, even amonglthe; s 1

NRC staff. L J Primarilyduetothosedevelopments,ourfscheduleforfdeveloping' recommended' d improvements for Mark I containments has slipped. Our ksy planning' milestones cm !

-are now the following: '

~

a l November 1987 - Planifor Developing lRe' solution- '

auly 1988- -

Preliminary l Recommendations ..

September 1988 -- . Final recommendations' to Comission; ,  ;

~

With regard to the: containment venting issue, we havefasked: Vermont' Yankee andv '

d y other' licensees.to proceed with caution.1 When backfitting design;changesito" #'

H such an important safety structure as the containment,7 1 t-is essential that '

O all:the ramifications.be considered carefully.;:It was for this reason that wei L '

l 'sent the enclosed letter to:VermontsYankee.asking thatithey;considerca1 .. . d number of questions in their evaluation of a containment vent for/the pla_nt.; '

j

, s c

4 l

-l y

1

! :i ' g gq

• B711020174 871023 $ 4

!PD ~ ADOCK 05000271 O V' :9"R PDR %-

i p-g.. y t

.t

( ' - -*

f,.., , .1 l_ _ _ -

5 '

1 F

}

' ~ ' '

'3] -., t

-'yi ' s ; .; t y' -

,q 79 x

, -. y i;!

e .-

1 fir. Gerald R. Tarrant' -2 :

• M y:'c '

m [9 "4

'f.-

1 t  ?

9.

-I-have instructed my staff to keep you/ informed'of all Eey-. developments on 1 H

fi s

~this issuerelated to. Vermont Yankee.

y lours [truly,1 '

',. K l

1 M

i-.

Original F ciM h7 -n '\ '

nais ac r>

's -

Thomas E. Hurley, Director 4 m_.. >

Office,ofNuclearfReactorTReg'ulation/- ~-

, )'d d

Enclosure:

m q

Ltr to R..W. Capstick fm S. Varga dtd 8/24/87 si d 4 ,1 cc:

J.. Gary Weigand,.. Vermont Yankee- ' ^ ~'

.. o

{

1. 1 E

, -,o DISTRIBUTION / >

I Central Files /  ;

PDR ~1' TEMurley '

JHSniezek a FJMiraglia ' l RStarostecki d 5Varga il WRussell, R-I Local PDR o

.i i

y l!

< -i

.,k?

? :'

l l.: -

l( 1 I '.

s < ;3,,

o .1 * :N  : ,

l : -: .......

~~~~~~~~~*~~~~~~~~---- ' L - '

,j

--------....:......----'--:--.........;.I~ h

. , ~~~~~~~

h  ::.Egurley:kb $ - ,

a L ,-. :...............~~~~~~~~~~

10-23-87.- .:

~~----------i----- ......'.-'------.....':.......,,,. 1

' 1, a;

~L.OFFICIALERECOR0!C0py1., _- , . l^ 7.g ,

• ql

gy

, iggy. ,

1 1 August- 24 198'7-

',.. Docket No.: 50-271 H l Mr. ;R. W. Capstick '

' Licensing Engineer. ._ . .i Vermont Yankee' Nuclear Power Corporation -

l 1617 Worcester Road Framingham, . Massachu setts ' ' 01701

Dear'Mr. Capstick:

~

SUBJECT:

': VERMONT YANKEE: CONTAINMENT SAFETY INITIATIVE;(TAC N0." 62753)l ~

On June ~25,1987,: Vermont. Yanke'e Nuclear Power Corporation L(VYNPC) submitted a -

status update and: design description for the Vermont Yankee Containment'= Safety; i

Initiative. We are: studying with interest your' plans to . proceed with . ,

l ' improvements -related to containment spray, and :look' forward to receiving more ,

infonnation. about -your. containment venting . plans. 1

..I Because we consider there- are' sev'eral unanswered . questions: concerning the . _ . '

j containment venting issue, we 1 ppreciate your thoughtfu1Ede11 berate; approach.'

We' note that you intend a thorough rereviewcof containment vent-~designiand.

implementation issues, and that you will notify us ofLthe results-of your:

review by March 1,11988. . We have,enclos'edfa list-of several considerations.

related to containment venting analysis that we woul.d like you> to ' consider in conducting your: review.

1 l Should you .have any questions regarding this please contact: the NRR Pmject -

L Manager, V. Rooney (301-492-8344).

Sincerely,'

h .

l.

- Steven A..- Varga', Director.

Division of, Reactor Projects:I/II . -

Office of Nuclear Reactor Regulation .,_

As stated

o l

l erv$8t76$57 Off.

4)t .(~

i e _ _2 : _ ,---  :- s

)

• g3=; 6 s

. Encl os u re. h CONTAINMENT VENTING' CONSIDERATIONS ,

Athoroughreviewof; con'siderationsinvolvedincont'ainmentventindwould'. ,

include: )

1). . A' comprehensive analysis of accident. sequences,-with their. estimated. .

frequency 'of occurrence, . for..which the vent.would be : called upon'. to -

't operate.:

2) - An estimate of the' fraction of.those. sequences where'the vent would be ,

m operated but where the accident would, have been.tenninated short'.of,

- containment failure without. vent operation:

a) . elhetric power returnhd to service -

b) equipment returned to service

i. c) mis-diagnosed. situation corrected by operators

3) A comprehensive analysis.of sequences:that i

(a) could be improved by correct use'of .the vent, or (b) could be-initiated or made worse by incorrect operation of the vent l L 4) An analysis of sequences-that could lead to containment failure by.

l operation of the vent ~followed by excessive pressure differential l

(buckling).

5) Analysis of the probability of vent failure when called upon. q

6) Analysis 'of maintenance or surveillance errors on the.. vent system that could induce accidents. . I

7) An estimate of. the radioactivity._ released for"all sequences when the vent could be opened, including both correct usage according to procedcres. 3nd 1 incorrect usage due to human' error or eouipment malfunction. ,

i I:

p o , _

__-__.-____._-mi