ML20054D520
| ML20054D520 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 04/15/1982 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Kerry J MAINE, STATE OF |
| Shared Package | |
| ML20054D521 | List: |
| References | |
| NUDOCS 8204230090 | |
| Download: ML20054D520 (5) | |
Text
.- -
i N
APR 151982 e.
1 y
RECENED a
APR 2019825 E a amm senem summe The Honorable John M. Kerry mam mumma l
State of Maine Senate s
Augusta, Maine 04333 9
Dear Mr. Kerry:
Your March 23, 1982 letter to Chairman Palladino regarding the Maine Yankee plant and the pressurized thermal shock issue has been referred to me for response. The Office of Nuclear Reactor Regulation is the part of the NRC staff that is charged with resolution of generic safety issues such as this one.
I share your concern about the pressurized thermal shock issue for the Maine Yankee plant as well as other pressurized water reactors (PWR).
As a result of operating experience, it is recognized that there could.
be transients in PWRs in which the reactor vessel could be subjected to severe overcooling (thermal shock) followed by repressurization. ~ s In these pressurized thermal shock transients, vessels would be subjected to pressure stresses superimposed upon the thermal stresses resulting l
from the temperature difference across the vessel wall. The Rancho Seco event of March 20, 1978 is believed to be the most severe and prolonged l
overcooling transient experienced to date.
l The NRC staff is involved in a significant program to evaluate this generic issue. Oar program includes a short-term reassessment of the pressurized thermal shock issue to be completed in the summer of 1982. This will be based on detailed information we have recently obtained from several of l
the owners of older PWRs, including the Maine Yankee plant, regarding their present and projected vessel material properties, the probability and severity of the transients that could challenge the integrity of em-brittled vessels, and tiie desirability of several potential corrective i
actions. Maine Yarkee Atomic Power Company provided this information for the Maine Yankee plant in their letters of November 2,1981 and January 21, 1982. These responses conclude that the Maine Yankee reactor pressure vessel will retain its integrity throughout its design 11fe. Our re-assessment will conclude whether or not the pressurized thermal shock concern warrants corrective actions at any operating plant, and if so we will take the necessary steps to require those corrective actions.
Our program also includes a long-term independent assessment of this issue utilizing our own staff as well as experts at several of our national labo-
.ratories. Upon completion of that assessment in approximately two years, Ok' we will propose appropriate criteria that all nuclear power plants must 3
meet to assure that pressurized thermal shock is not a safety concern at any plant through the life of the plant.
Dg e t
f l
l omer >
sun-e >
9204230090 820415 PDR ADOCK 05000309 I NRC FO H PDR FFICIAL RECORD COPY usceo: m i-m m
g
~1 l
_2 At the outset of our program we considered the questions you raised, specif-ically: is Maine Yankee, as well as other PWRs safe to continue operating during resolution of this issue? Our review of this question included the i
likelihood of a " Rancho Seco" type event.
Our review also included: (1)other types of transients or accidents that could lead to overcooling of the reactor system; (2) the probability that overcooling events will occur; (3) experience with transients that have occurred at PWRs in the United States; (4) initial and irradiated reactor vessel material properties; and (5) the capability of l
reactor vessels to withstand these transients based on fracture mechanics calculations.
As a result of our review we have concluded that the probability of a severe overcooling transient (similar in magnitude to the Rancho Seco event) is relatively low.
For Babcock & Wilcox plants, such as Rancho Seco, this probability is about 10-3 per reactor per year.
For Combustion Engineering designed reactors, such as the Maine Yankee plant, and Westinghouse plants, this probability is lower perhaps by l
an order of magnitude.
In addition fracture mechanics analytical results shou that, assuming preexisting cracks in the reactor vessel and the occurrence of a severe transient such as the Rancho Seco event, reactor vessel failure would be unlikely even in the most vulnerable plants within the next few years. Accordingly we have concluded that continued operation of PWRs, including Maine Yankee, is acceptable pending resolution of the pressurized thermal shock issue.
1 I trust the information provided above is responsive to your request.
Sincerely.
Origini reed W
( 11. It D "in Harold R. Denton, Director Office of Nuclear Reactor Regulation l
WDirks Docket File w/ incoming KCornell NRC PDR w/ incoming TRehm Local PDR w/ incoming l
RMinogue E00 Reading WKerr OELD SHanauer MBridgers (E00-11728)
RMattson Program Support Ataff, NRR RVollmer MJambor HThompson DEisenhut I
PCheck JHeltemes, AE00 RSnyder CNels,on w/ incoming EDC g DCtiRRingham PKreutzer g gb g bd, P' Denton l
4/ /82 L
.d omce>..D.L:.QRBD..... QL1,0BSD........ DL.;0RBl.4....... AD.:.0R................ D/ DST,,,,,,,,,,,,,0,;,p,L,,,,,,,,,,,,p,;gggj,,,,,,,,,,
CNe,,s on/,dy,d.,,G,Vig,q,jn,q,,,,,,,,J,N0 yak
,,,,,S,H,a n,a u e,r,,,,,,,p.Eb.Mhut...
. C,a,s,e,,,,,,,,,,,,,,,
1 5= = >.gr,eutzen,
.4Lb#.2.,,,,,, 4/hj,82,,,,,,,, 4/&f,0,2,,,,,,,,,,418&.............. 4./dJM.... 4.4.7 /.82...... 4 $l82,,,,,,,,,
our>
sac ronu ais oom) Nacu ono OFFICIAL RECORD COPY usam,,,im
/
/
/
[ /
At the outset of our program we considered the questions you# raised, speci-fically: is Maine Yankee, as well as other PWRs, safe to continue operating during resolution of this issue? Our review of this question included the likelihood of a " Rancho Seco" type event. Our review also included: (1) other types of transients or accidents that could lead to overt.coling of the reactor system; (2) the probability that overcooling events will occur; (3) experience with transients that have occurred at PWRs in the' United States; (4) initial and irradiated reactor vessel material properties; and (5) the capability of reactor vessels to withstand these transients' based on fracture mechanics calculations, f
As a result of our review we have concluded that the probability of a severe overcooling transient (similar in magnitude to the Rancho Seco event) is relatively low.
For. Babcock & Wilcox plants, such as Rancho Seco, this probability is about 10 per reactor per year.
For Combustion Engineering designed reactors, such as the Maine Yankee plant, and Westinghouse plants; this probability is lower perhaps by an order of magnitude.
In addition fracture mechanics analytical results show that, assuming preexisting cracks in the reactor vessel and the occurrence of a severe transient such as the Rancho Seco event, reactor vessel failure would be,unlikely even in the most vulnerable plants within the next few years. Accordingly we have concluded that continued operation of PWRs, including Maine Yankee, is acceptable pending resolution of the pressurized thermal shock issue.
j I trust the information provided above is responsive to your request.
[
Sincerely,
/
/
/
Harold R. Denton, Director Office of Huclear Reactor Regulation PPAS HDenton ORB #3 Rdg GCunningham Docket File w/ incoming RAClark ECase NRC POR w/ incoming 7
ORB #3, Green Ticket Local PDR w/ incoming File EDO Reading (if signed bt Case or above)
WDircks OELD KCornell MBridgers (E00-11728)
TRehm Program Support Staff, NRR RMinogue MJambor WKerr MStine l
SHanauer DEisenhut RMattson JHeltemes AE0D D:NRR RVollmer CNelson w/ incoming Denton HThompson PKreutzer 4/ /82 PCheck
{@
RSnyder ggg n
p
.D.:ka/,,,,,
- oma,
. 9.L.:0RBy3
%,;0Rf#I,,,,
, DL 0,RB,#,4_,,j g.[
.D/DS.TI;h. ':-
1
...Py,f,y,'h,,z,e,,,,,,
,, N,h,,on,/dy,d,,G,y[s sj n9,,,,,,Uf,de,,,,,,
...S H a,.
,,,g Ei s enh ut,,,,, C a s e,,,,,,,,,,,,
,,C,
, r,,
wR ~- >
l
....&za2,,,,,,,,,wyn,,,,,,,,,4 /j.;jg,2,,,,,
- g. gag.,,,, 4g ja.
.41.1. pag...
,4m,82...,.
4 em>
NRC FORM 318 (1480) NRCM ono OFFICIAL RECORD COPY usad i m
0
\\
J f
l'
~
]
g
' ggN FROM:
ACTION CONTROL DATES CONTROL NO.
?[l([M COMPL DEAOLINE t
,Jg tt5 4. YCfry DATE OF DOCUMENT
$I3If $CHRtGr DlM
' '.LKNOWLEDGMENT lr4T ERIM RE PLY
)fbfh,2 T O:
PREPARE FOR SIGNATURE OF:
~,
FINAL REPLY
/
O CHAIRMAN (b3ITL*O EcIlad{$3 FILE LOCATION
< /,/
ECTOH O EXECtg'f OTH E R :
DESCHIPTION
$ LE1TEH OMEMO O ntPORT O OTHER SPECI AL INSTRUCTIONS OR REMARKS Concm re serious proble of pressurl:e1 thercsl shcci & Safety of tM Maine Yanhte (Tant CLASSIFIED DATA oOCuMENT/ COPY NO.
CLASS'FICATIONl NUMUE R OF PAGES CATEGORY bdYaN+DY*)
"OsT A L n u.isT nY No.
O Nsi O no O rnD ASSIGNED TO.
DATE INFORMATION ROUTING LEG AL REVIEW U FINAL U COPY sNd3 s ERA N h 6N U$ rCYs CASOMcDten /psicr r0 To:
DATE NO LEG AL OBJLCTIONS IIIsenhut 4/6/82 Cornell 1.
PPAS
'+
" *P 3 Gil NOTIFY:
._..~. -
Te?C 2.
lianauiFr-6.-Cheel.
o EDO AOuiN s CORnEs as MicFiua 3. !aatt:6ndrM*T COMMENTS, NO T FY t err, $P 4.
Vollmer Ex t.
(OCI4-)DL ED JCAE NOTIFICATION RECOMMENDED:.
U YES U NO DO NOT REMOVE T)Tr$qY N
W EXECUTIVE DlHECiOR FOR OPERATIONS PRINCIPAL CORRESPONDENCE CONTROL 8
h t
0
A o
'l e
t s
1-e 0361 too,in, oate 4/i/82 N
No.
NRC SECRETARIAT TO:
Commissioner Date
@ E mec. Dir./Oper.
Gen. Counsel O Cons. Liaison O soiicitor O eueiic 4ffairs O secretary inspector & Auditor Policy Eweluation John M. Kerry
,,co,,;g.
state of Maine p,,.
7, Palladino 3/23/82 o t.
the hazaI,. ref 4/10/81 ltr to Udall fm D, Basdekas*ds' of Pressurized thermal sh su re concerned about the safety of the Maine Yankee facility Prepare reply for signature of:
Chairman O Commissioner E DO, GC, CL, SO L, P A, SE CY, I A, PE signature block omitted Return original of incoming with response Xh For direct reply
- Suspense: Apix April 16 For appropriate action For information Hemarks:
RF. an c ie o +
For the Commission:
hillio l
- Send three (3) copies of rept to Se Corres ndence and Records Brar' h i
ec'd ff. E Date,,, f.2,/f, 2
..eegeTION SLIP wer)qu e:A Time,,,, /l d,,,,,y
.,