ML20041F566
| ML20041F566 | |
| Person / Time | |
|---|---|
| Issue date: | 03/05/1982 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | |
| Shared Package | |
| ML20041F565 | List: |
| References | |
| REF-10CFR9.7, TASK-PII, TASK-SE SECY-82-097, SECY-82-97, NUDOCS 8203170163 | |
| Download: ML20041F566 (9) | |
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h SECY-82-97 March 5,1982 POLICY ISSUE (Information) v-o; N
S 2cy Afgg ED
~
4 For:
The Commissioners g
to F rom:
William J. Dircks, Executive Director for Operations
Subject:
COMMISSION BRIEFING ON PRESSURIZED THERMAL SH0CK Pu rpose:
To provide the Commissioners with an advance summary of the i
Pressurized Thennal Shock Briefing scheduled for March 9,1982.
l l
Discussion:
The conmission has requested to be briefed on the status of staff efforts to resolve the Pressurized Thennal Shock issue.
The enclosure to this infonnation paper presents an assessment of staff review of the 60 and 150 day response from licensees and vendors and status of staff review.
-bd William J. Dircks, Executive Director for Operations
Enclosure:
Summary of March 9 Commission Briefing on PTS
Contact:
R. Woods, NRR 492-4714 DISTRIBUTION Commissioners Commission Staff Offices ACRS Secretariat 8203170163 820309 PDR 10CFR PT9.7 PDR
e SLNMARY OF MARCH 9 COMMISSION BRIEFING ON PRESSURIZED THERMAL SH0CK (PTS), (USI A-49)
The 60 and 150 day responses to our August 21, 1981 letters to eight licensees, together with the Owner's Group responses, have provided:
(1) Better knowledge of plant-specific fluence and materials properties; (2) More detailed plant-specific analyses of certain standard design basis accidents (DBAs) and standard abnormal operational occurrences (A00s), including specificaticn of the event sequences, pressure and temperature calculations, and fracture mechanics calculations using plant-specific material properties; and (3) Some additional information about plant-specific operational procedures and operator education / training regarding PTS events.
These submittals present each licensee's conclusions that the events analyzed do not represent a significant risk to vessel integrity from PTS or any plant and therefore no substantive corrective actions are needed.
We have not completed our reviews, but we will probab.y ultimately agree with at least a considerable portion of the licensees' and Owner's Group conclusions regarding the effects on vessel integrity of PTS events arising from standard DBAs and A00s.
s However, we continue to believe that the majority of the PTS risk is due to events that involve multiple failures and operator errors, as opposed to the standard DBA and A00 events so far considered in the referenced submittals.
We note that all of the PTS precursor events that have occurred have been multiple problem events and not standard DBAs and A00s.
A typical way for these multiple problem events to occur is when an overcooling event becomes severe enough to cause contraction which drops water level' out of the pressurizer.
This creates a steam bubble elsewhere in the system which causes system behavior that is less familiar to the operator.
The operator is then more likely to make the multiple errors necessary to cause development of a severe PTS event.
Of course, this has not in fact occurred. We believe there are many scenar'os, same involving the above example, that can lead to PTS events.
The large number of such sequences creates the potential for a risk that is not negligible, even though each individual sequence may be calculated to have a very low probability.
s The above-described difficulty in defining the events creating PTS risk is currently the major uncertainty in the PTS program. For example, deciding when to allow credit for warm prestress is strongly dependent on the detailed sequence of the events analyzed.
It is the uncertainty in definition of the course of the event (s) that causes us to question whether warm prestress will be effective in actual events, i
s We do not currently have proper identification and analyses of the multiple problem events.
Our longer range procedures development and PTS programs are designed to provide such infonnation by mid-1983, but results will not be available for the June 1982 reassessment.
Without such information, we do not feel that we can achieve a finn basis for reaching long-tenn conclusions about PTS risk for the June 1982 reassessment.
We will continue to urge the industry to provide more complete information regarding multiple problem events while we complete review of the submitted material leading tavard our June 1982 reassessment of the PTS issue to the Commission. We will also obtain coordinated review assistance of a panel of technical experts from outside the NRC staff in the several relevant fields involved in PTS.
Additionally, we will undertake a program to verify that existing operating procedures contain the steps necessary to prevent and/or mitigate PTS events, and to verify that operator education / training programs regarding PTS are acceptably thorough.
Our June 1982 reassessment is the near tenn objective of our review efforts.
In June, we must answer the question:
"Are corrective actions required at any plant that must be initiated before the longer tenn PTS program provides generic resolution and acceptance criteria?"
If our staff reviewers, together w a our panel of outside experts, cannot establish a finn basis to answer the above question either "yes" l
. or "no," then we would plan to take the conservation approach and recommend to the Commission (in June) those corrective actions we believe necessary to e
provide an acceptably conservative safety margin during the interim period pending completion of the long term PTS program.
Attachment:
Summary of "150 day" Responses Concerning PTS including a Summary of Generic Reports Concerning PTS
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f StM4ARY Of "150 DAY" Rt SPON$ts C0t4Ct kNING Pl5 AIIACIM NT
_ g,3,y
,75pg,3, PHl'.lktSSlHG OPlHAION ACll0NS PLANI IO ((IlfRS &.
(O$$$ VINDOH)
C.CN. CONIENIS CONCLUSIONS LIMillNG IRANSIENIS CRITEklA Of ACCIPI.
t ofs litt kt o Cot 4SIDikto M Mf 0l A8' Afflui-ft. Calhoun I.T hermal-Itydro. Integrity will be MSLB most limiting, over-for MStB (tow peo' ability) Benefit in Yes
- 1. Will impit= cut Jan.18, 1982 Eval.
maintained for cooling A00- stucit open
- crack. arrest.
W.P. not fur MStB - 30 min. to reduced s adial (a) stb lifetime of plant.
dump valve.
fo-A00 t Single failure considered, reduce itPSI flow, leatage duct (CE)
(b) Overcool-(SBLOCA + L0fW analyzed
- crack arrest, however, it for MStB - trip HC ut.eme in Cycle Ing (anti-in CEN 189) for A00 - No crack was not pumps in 30 seconds 8
cipated initiation needed. it for A00 trip RCP in
'. Will study othes occur-would have 10 min. Reouce llPSI fuel arrange-been credites in 90 min.
ment schem es rences) t fracture Mech if needed I. Ib not plant and critesla inc rea st-in Analy. tor SLB met.
[CC wa ter taup.
a
- 1. Response to
- 4. Ivaluating Dec. 18 Itr.
sainica. ing
[
- 4. fluence data 3
Program plan will evaluate (ontsul systems, sose1..es &
epotential design 4
mod >.
Maine Vankee APP A - response Vessel will retain MSLB most limiting No crack init.ation.
I:esi':li t fri les I. tow leakage 1/21/82 to 4-150 day integrity through- (cooldown below 300 )
Reslunse references Cf N W.P. not f ur M'al b fuel management 0
guestions out design-11fe.
189 Report. Prob. of runsidered, Irtp RCP 9 30 sec.
for Cycle 1 APP B - response MSLB is very low.
however, i t Terminate. flPSI (8
'. Will operate f(W1 (cg) to RFI of 8/21/8; was not 30 min.
to maintain APP C - response needed. It higher temp. not to 12/13/31 ltr.
would have for ADO to entee.1 80" L,cen credited Trip RCP 9 10 min.
- l. Will keep 8 " '
if needed lerminate itPSI 9 90 informe.1 on N
and criteria nii n.
asuecalisag,
met.
- 1. Will evaluate control sisategy alter plant spec i f ic eval-uation is in place.
- Dun' t address '
selection of events causing highest PIS rl: k.
s e
SIM4ARY Of "150 DAY" Ri$PON5f5 CONClkN!NG Pl$
--~ llARM -
~ ~ ~ -
7 EXPON5L PRESIRISSING OPLRA103 ACil0NS 4 ANI TO LETIERS &
CONCLUSIONS LIMITING TRANSI[NTS CRITtRIA Of ACCEPI.
LONS IDI Rf D CONSIDlHfD (C555 VtNDOR)
GE,N. CONIENIS Yss 1.scops,y!)Al A Q lotts Rt Mil stujies oT roeg CIThr t T 7 4s respon-ho crack initta-
~H511 most limiting, lo crack initTition for Venefl~t l~m Cllifs sive Lion for assumed A00
- single failure, A00 W.P. rent for Mst u
.a,g ga.n t.
Jaa. 28, 1902 2. fluence cal.
plant life for SBLOCA t L0fW analysis Crack arrest for M5tu considered, Trip RCP v30 sec.
2.Do not plan to increa.e (Resp. to
- 3. Systuos SBLOCA + L0fW.
in CE It19 however, it Reduct liPSI flow v30 kWSI towperature.
was not min.
3.No dis (union on aime.al-12/18/111 Itr Analysis Same for stuck needed. it for A00 3,,j,
valve open dump!
1/21/82)
- 4. fracture would have' Trip RCP e 10 min.
4 Control syston (haeme.
(A00) mechanics been credite<l Ierminate AfW e 10 may le (unsidered.
(Cf) for MSLB, satist if needed 491 min. Reduce itP51 factory perfor-criteria met
- 90 min.
mance for 21 addt' I O PY.,
Oconee 1
- 1. Overcooling Vessel failure is SBLOCA
- 10fW Crack initiation with Yes,tur Sut 00A + I Ol W l.Its month fuel tycle Jaa. IS,1982 transient not calculated to Overcooling transient arrest within 1/4 I
$B10CA. No Trip RC C lhrottle provides decrease in for over--
liplS 6893 miti, leakage ilua.
andlysis. **
result from post-coollwJ tulated transient:
- 2. Current water towpes.s tua.
transtent sufficient, Oye!1mlied lrgns tent 2, SBLOCA With mintoal down Trlp RCP. Isolate 3,gnplace annegging nog analysis comer mixing, no.
tlWS v20 min.
reiluired.
(D&W)
- 3. Mixing credit for minir>J lhrottle itPIS.
analysis in h9L leg, no 4.No control sys tem than le
- 4. Vessel well credit for W.P..
are necessary.
thermal 16 [fPY. With dualysis Credit for W.P.,
Orily assumeij above S Materidl
+for SBLOCA-32 actions where properties IfPY. For over-i,nessary to mittigat.
- 6. Pluence cooling transient conse.luences arkt determination 25 EffY (Design achieve acceptable
- 7. fracture life - approx,
.gffy.
mechavitcs 21[ffY) dnalysis
- 8. frequency determinatlosi e
- 9. $LB dnalysis
- Turbine b>-
i pass systW
- failures, overiill tr nitents
s
/
SLM4ARY Of "lSO DAY" RtSPON$f5 CONCtRNING PIS 7 ESPONSL MAhH
~~~
Pt ANT 10 LEllERS &
PHtSikt'. SING Off RAIOR ACil0NS (N5SS VINDOR)
GEN. CON 1[NIS CONCLUSIONS LIMITING IRANSl[NIS CRIllRIA Of ACCLPI.
CONS Itt kE D CONSIDiktD kitglil Al Mllons tobinson 2
- 1. Irradiation 31 cal, yrs, of Itpt. provided a table of Min, flaw depth for crack Yes, for all Refers to WCAP 10019. 1. Will lave low lea ka.3c U n. 25, 1982 date Vessel life ristin transler.ts considered initiation is greater trans ients Credit is taken for core'in 1982.
- 2. Weld sisterial in9 for all which include following:
than 1.0 inches, considered.
1518. AFW teswinated 2. Will beep abreast on (W)
Info.
transients con-1.
Large LOCA 11 PSI terwinated in drua aling develo6*'ent'.
- 3. Casis for sidered.
2 SBLOCA Crack arrest occurs 10 wise.
- 3. Studying besielits us (ef ere Ked continued 3.
LSLB within ?SZ of vessel wall heatting kW51.
WCAP 10019 operation 4
SSLD
- 4. Verification 4 wlysi.
5 Rancho Seco by (PHl.
- 4. Operator dctions
- 5. Rcmedl41 actions Turkey Pt. 4
- 1. Irradiation Reactor vessel in-Rpt, provided a table of Min, flaw depth for Yes, all Carieunt determine but Since integrity h.ns becu Jan. 21, 1982 jnforwallon tegrity will be transients considered crack initiation is transients WCAP 10019 provides' dmonstrated, ex need tier
- 2. Weld unalntained through which include following:
greater than 1.0".
except SSLB following:
action plan.
(W) siaterial info out design life
- 1. Large LOCA C"M M
- 3. Transient
- 2. SBLOCA Crack arrest occurs Referenced fracture
- 3. LSLB within 751 of vessel KAP 10019 analysis
- 4. $$t B wall thick.
showing lessis
- 5. Rancho Seco for guntinued operation,
- xa Onofre.
- 1. Irredletion Reactor vessel Rpt. Provided a table of Min, flaw depth for Yes, f or f or I St B Plan f or remedial ac tion.
Jin. 25, 1982 effects integrity will be transients considered crack inillation is large asid leswirsite HPSI not warranted. L ow le.it.a.3
- 2. Material maintained beyond which loclude following greater.than 1.0.
smult toCAs ie:winate AiW to core is in place.
design life tlsse.
1.
Large 1,0CA orily.
faulteil SG.
(W)
- 3. property' info Bests'for 2.
SBLOCA Crack arrest occurs Rzferenced continued 3
LSLB within 7S1 of vessel
[or SSt B WCAP 10019 operation.
4.
SSLB wall thick.
Isolatebreak(l'UHV)
- 4. Oper4tton 4.
Rancho Seco Teiwliate llPSI actions
- 5. Remedial Actfons
\\
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6 e
SUMMARY
OF CINERIC REPOHl$ CONCt RNING PIS General Limiting Criteria of Wars Prestressing Operator Action Potential am. r5 Cr oup Contents Conclusions Iransients*
Acceptance Considered Conaldered Revedial Action Westinghouse UULM00W
- l. Limited transient All plants
"*l. Small
- 1. No ini tia tion Benefit of W.P.
Yes-Control AfW
- l. Heating RW5T to O
December 1981 development can continue
' Steam Line of flows less considered for Trip RCPs as BO -provide increase "Stannery
- 2. Fluence Calc.
operation a Break than 1 inch 5810CA and some examples-Neport af 3 to 30 Ef PV of Report on
- 1. Stress & Fracture ntmber of
- 2. Rancho Sea deep.
large LOCA and is not very aperation.
Re:ctor Vesse'.
Mechanics for yrs. (3 for
- 3. Large (Flaws 71 inch large SL Lreaks.
dettnitive.
!. Limit AfW Integrity for Transients the lea'st).
Steam Line deep not Benefit was not
- 1. Control 5) stems to Westinghouse
- 4. Vessel Integrity before Break assumed to considered for nitigate transients Operating Evaluations acceptance
- 4. Small LOCA exist) or other transients.
4 RC Press. Rettet Plints"
- 5. Potential Remedial -
criteria is
- 5. Large LOCA 2. Crack Arrest System Actions violated. A Occurs within L. Safety injection table pro-75% of wall Control f,. Conclusions (for each operating plent) wides no. of "In order of thickness.
c.
AfW Control
- 4. Core tiodifications
- 1. Don't address identi-yrs. for each severity.
fication of events plant. Eight
- a. tow leakage loading causing highest PTS plants are "Most Limiting S. Annealing Vessel risk.
5 yrs, or less.
- 4. Is feasible Cumbus tion Engineering CEN-T89
- 1. Only addresges 5BLOCA Each plant's
- 1. Only con-
- 1. No inittetfun Benefit of WP was Yes:
None considered
~~
"Lvaluation with loss of all fW vessel can siders of flows of considered I. PORVs opened of Pressurized Transient safely with-SBt0CAeL0fW credible size, in 10 min.
Thermal Shock 2. Thermal Hydro snalysis stand SBLOCA*
or if it'does
'2. AIW reinstated E f f1c ts Due
- 3. Discussions on mixing L0fW for
- initiate, af ter 30 min.
to small Break Additional studies design life
- 2. Arrest after LOCAs with are expected to pennit without crack limited exten-1 Loss of feed-removal of certain initiation.
'slon.
Water for CE conservatisms NS$$'*
- 4. Scoping studies indi-i December 1981 cate range of ilPSI
- (Ihis is flows must be consider-the Post-ed
"(Note that IMI " feed &
- 5. Fluence Calculation MSL break is blerd' rpt.- 5. Materidi Properties most Ilmiting it is not a
/. Vessel Integrity but was only Generic PIS Evaluation considered in report.)
- 1. ' Plant ! w.ftc the 150 day AralysN tesponses)
No B&W Re, sort --prua seo plan-specific f nalyses. No pueric report p omised.
,