ML18082A421
| ML18082A421 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 05/09/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Schneider F Public Service Enterprise Group |
| References | |
| NUDOCS 8005200129 | |
| Download: ML18082A421 (11) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION REGION I 631 PARK AVENUE KING OF PRUSSIA, PENNSYLVANIA 19406 Docket No. 50-272 50-311 Public Service Electric and Gas Company ATIN:
Mr. F. W. Schneider Vice President - Production 80 Park Place Newark, New Jersey 07101 Gentlemen:
May 9, 1980 6:b.J~F~
. 800521012'1 p
The enclosed IE Bull et in No. 80-12, 110ecay Heat Removal System Operability, u is forwarded to you for action.
A written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely,
~~~
(/7~ Director
Enclosures:
- 1.
- IE Bulletin No. 80-12 with Attachment
- 2.
List of Recently Issued IE Bulletins CONTACT:
W. H. Baunack (215-337-5253) cc w/encls:
F. P. Librizzi, General Manager - Electric Production E. N. Schwalje, Manager - Quality Assurance R. L. Mittl, General Manager - Licensing and Environment H. J. Midura, Manager - Salem Gen~rating Station 1
ENCLOSURE 1 UNITED STATES SSINS No.:
6820 NUCLEAR REGULATORY COMMISSION Accession No.:
OFFICE OF INSPECTION AND ENFORCEMENT 8005050053 WASHINGTON, D.C. 20555 IE Bulletin No. 80-12 Date:
May 9, 1980 Page 1 of 3 DECAY HEAT REMOVAL SYSTEM OPERABILITY
==
Introduction:==
The intent of this Bulletin is to improve nuclear power plant safety by re-ducing the likelihood of losing decay heat renioval (OHR) capability in operating pressurized water reactors (PWRs).
PWRs are most susceptible to losing DHR capability when their steam generators or other diverse means of removing decay heat are not readily available.
Such. conditions often occur when the plants are in a refueling or cold shutdown mode, and during which time con-current maintenance activities are being performed.
There is a need to assure that all reasonable means have been taken to provide redundant or diverse means of OHR during all modes of operation.
(Note: A redundant means could be provided by having OHR Train A AND Train B operable; a diverse means could be provided by having either DHR Train A OR Train B operable AND a steam generator available for OHR purposes.) There is also need to assure that all reasonable means have been taken to preclude the loss of DHR capability due to common mode failures during all modes of operation.
Background:
On several occasions, operating PWRs have experienced losses of DHR capability.
In each instance, except that of the Davis-Besse Unit l incident of April 19, 1980, DHR capability was restored prior to exceeding the specified RCS temperature limit for the specific mode of operation.
Nonetheless, the risk and frequency associated with such events dittate that positive actions be taken to preclude their occurrence or at least ameliorate their effects.
The most noteworthy example of total loss of DHR capability occurred at Davis-Besse Unit 1 on April 19, 1980.
(See IE Information Notice No. 80-20, attached hereto as Attachment 1).
Two factors identified as major contributors to the Davis-Besse event in* the Information Notice are:
(1) extensive mainten-ance activities which led to a loss of redundancy in the DHR capability, and (2) inadequate procedures and/or administrative controls which, if corrected, could have precluded the event or at least ameliorated its effects.
ACTIONS TO BE TAKEN BY LICENSEES OF PWR FACILITIES:
- 1.
Review the circumstances and sequence of events at Davis-Besse as des-cribed in Attachment 1.
IE Bulletin No. 80-12 Date:
May 9, 1980 Page 2 of 3
- 2.
Review your.facility(ies) for all DHR degradation events experienced, especially for events similar to the Davis-Besse incident.
- 3.
Review the hardware capability of your facility(ies) to prevent DHR loss events, including equipment redundancy, diversity, power source reliability, instrumentation and control reliability, and overall rel i abi 1 ity during the refueling and cold shutdown modes of operation.
- 4.
Analyze your procedures for adequacy of safeguarding against loss of redundancy and diversity of OHR capability.
- 5.
Analyze your procedures for adequacy of responding to OHR loss events.
Special emphasis should be placed upon responses when maintenance or refueling activities degrade the OHR capability.
- 6.
Until further notice or until Technical Specifications are revised to resolve the issues of this Bulletin, you should:
- a.
Implement as soon as practicable administrative controls to assure that redundant or diverse OHR methods are available during all modes of plant operation.
(Note: When in a refueling mode with water in the refueling cavity and the head removed, an acceptable means could include one OHR train and a readily ac~essible source of borated water to replenish any loss of inventory that might occur subsequent to the loss of the available OHR train.)
- b.
Implement administrative controls as soon as practicable, for those cases where single failures or other actions can result in only one DHR train being available, requiring an alternate means of OHR or expediting the restoration of the lost train or method.
- 7.
Report to the NRC within 30 days of the. date of this Bulletin the results of the above reviews. and analyses, describing:
- a.
Changes to procedures (e.g., emergency, operational, administrative, maintenance, refueling) made or initiated as a result of your reviews and analyses, including the scheduled or actual dates.of accomplish-ment; (Note: NRC suggests that you consider the following: (1) limiting maintenance activities to assure redundancy or diversity and integrity of DHR capability, and (2) bypassing or disabling, where applicable, automatic actuation of ECCS recirculation in addition to disabling High Pressure Injection and Containment Spray preparatory to the cold shutdown or refueling mode.)
- b.
The safeguards at your facility(ies) against OHR degradation, including your assessment of their adequacy.
l IE Bulletin No. 80-12 Date:
May 9, 1980 Page 3 of 3 The above information is requested pursuant to 10 CFR 50.54(f).
Accordingly, written statements addressing the above items shall be signed under oath or affirmation and submitted within the time specified above.
Reports shall be submitted to the director of the appropriate NRC regional office, and a copy forwarded to the Director, Division of Reactor Operations Inspection, NRC Office of Inspection and Enforcement, Washington, D. C. 20555.
Approved by GAO, 8180225 (R0072); clearance expires 7-31-80.
Approval was given under a blanket clearance specifically for identified generic problems.
Attachment:
IE Information Notice No. 80-20
Attachment to IE Bu~tin No. 80-12 ENCLOSURE 1 SSINS No.: 6870 UNITED STATES Acces.sion No.:
NUCLEAR REGULATORY COMMISSION 8002280671 OFFICE OF INSPECTION AND ENFOR.CEMENT WASHINGTON, D. C. 20555 IE Information Notice 80-20 Date:
May 8, 1980 Page 1 of 3 LOSS OF DECAY HEAT REMOVAL CAPABILITY AT DAVIS-BESSE UNIT 1 WHILE IN A REFUELING MOOE Description of Circumstances:
On April 19, 1980, decay heat removal capability was lost at Davis-Besse Unit l for approximately two and one:..half hours.
At the time of the event, the unit was in a Y..efueling mode (e.g., RCS temperature was 90F; decay heat was being removed by.Decay Heat Loop No. 2; the vessel head was detensioned with bolts in place; the reactor coolant level was slightly below the vessel head flanges; and the manway covers on top of the once through steam generators were removed).
(See Attachment A, Status of Davi s-B.esse l Prior to Loss of Power to Busses E-2 and F-2 for additional details regarding this event.)
Since the plant was in a refueling mode, many systems or components were out of service for maintenance or testing purposes.
In addition, other* systems
-and components were deactivated to preclude their inadvertent actuation while in a refueling mode.
Systems and components that were not in service or deactivated included:
Containment Spray System; High Pressure Injection System; Range Channel 2; Decay Heat Loop No. l; Station Battery lP and lN; Emergency Diesel-Generator No. 1; KV Essential Switchgear Bus Cl; and 13.8 KV Switchgear Bus A bus was energized but not aligned).
Source.
4.16 (this In brief, the event was due to the tripping of a non-safeguards feeder breaker in 13.8 KV Switchgear Bus B. Because of the extensive maintenance and testing activities being conducted at the time, Channels 1 and *3 of the Reactor Protection System (RPS) and Safety Features Actuation System (SFAS) were bei n*g energized from only one source, the source emanating from the tripped breaker.
Since the SFAS logic used at Davis-Besse is a two-out-of-four input scheme in which the loss (or actuation) of any two input signals results in the actuation of all four output channels (i.e., Channels 1 and 3, and Channels 2 and 4), the loss of power to Channels l and 3 bistables also resulted in actuation of SFAS Channels 2 and 4.
The actuation of SFAS. Channels 2 and 4, in turn, affected Decay Heat Loop No. 2, the operating loop.
Since the initiating event was a loss of power event, all five levels of SFAS were actuated (i.e., Level 1 - High Radiation; Level 2 - High Pressure Injec-tion; Level 3 - Low Pressure Injection; Level 4 - Containment Spray; and I
IE Information Notice No. 80-20 Date:
May 8, 1980
- page 2 of 3 Level 5 - ECCS Recirculation Mode).
Actuation of SFAS Level 2 and/or 3 resulted in containment isolation and loss of normal decay heat pump suction from RCS hot leg No. 2.
Actuation of SFAS Level 3 aligned the Decay Heat Pump No. 2 suction to the Borated Water Storage Tank (BWST) in the low pressure injection mode.
Actuation of SFAS Level 5 represents a low level in the BWST; therefore, upon its actuation, ECCS operation was automatically transferred from the Injection Mode to the Recirculation Mode.
As a result, Decay Heat Pump No. 2, the operating pump, was automatically aligned to take suction from the containment sump rather than from the BWST or the reactor coolant system.
Since the emergency containment sump was dry, suction to the operating decay heat pump was lost~
As a result, the decay heat removal capability was lost for approxi-mately two and *one-half hours, the time required to vent the system.
Furthermore, since Decay Heat Loop No. 1 was down for maintenance, it was not available to reduce the time required to restore decay heat cooling..
MAJOR CONTRIBUTORS TO THE EVENT:
The rather extended loss of decay heat removal capability at Davis-Besse Unit 1 was due to three somewhat independent factors, any one of which, if corrected, could have precluded this event.
These three factors are:
(i) Inadequate procedures and/or administrative controls; (i-i) Extensive maintenance activities; and (iii) The "two-out-of~four. SFAS logic.
Regarding inadequate procedures and/or administrative controls, it. should be noted that the High Pressure Injection Pumps and the Containment Spray Pumps were deactivated to preclude their inadvertent actuation while in the. refuel-ing mode.
In a similar vein, if the SFAS -Level 5 scheme had been by-passed or deactivated while in the refueling mode, or if the emergency sump isolation valves were closed and their breakers opened, this event would have been, at most, a minor interruption of decay heat flow.
Regarding the extensive maintenance activities, it appears that this event would have been precluded, or _at least ameliorated, if the maintenance activi-ties were substantially reduced while in the refueling mode.
For example, if the maintenance activities had been restricted such that two SFAS channels would not be lost by a single event (e.g., serving Channels 1 and 3 from separate sources), this event would have been precluded.
Likewise, if mainten-ance activities had been planned or restricted such that a backup decay heat removal system would have been readily available, the consequences of the loss of the operating decay heat removal loop would have been ameliorated.
Regarding the two-out-of-four SFAS logic used at Davis-Besse, even under normal conditions, it appears that this type of logic is somewhat more suscep-tible to spurious actions than other logic schemes (e.g., a one-out-of-two taken-twice scheme).
This susceptibility is amplified when two SFAS channels are served from one source.
Consequently, when the source feeding SFAS Channels IE Information Notice No. 80-20 Date:
May 8, 1980 Page 3 of 3 1 and 3 _was lost, all five levels of SFAS were actuated.
As stated previously,*
this particular event would have been precluded if SFAS Channels 1 and 3 were being served from separate and independent sources.
In a similar vein, this specific event would have been precluded by a one-out-of-two taken twice type of logic that requires the coincident actuation of or loss of power of an even numbered SFAS.Channel and an odd numbered SFAS Chann~l.
Since* each LWR can be expected to be in a refueling mode many times during its lifetime, licensees should evaluate the susceptibility of their plants to losing decay heat removal capability by the causes described in this Informa-tion Notice.
No specific action or response is requested at this time.
Licensees having questions regarding this matter should contact the director of the appropriate NRC Regional Office.
Attachm~nt A
Attachment A to r8nformati.;n Notice No. Bo~2o-**
F.nclosure A DAVIS-BESS~ EVENT OF APRIL 19 1 1980 STATUS or DAV'!S-BESSE 1 PRIOR TO LOSS OF POw"'ER TtLB,!tSS'ES E-2 Afm 7-2:
0 l.. Refuel.ills mode with B.CS ~emperat.ure at 90 F and leve1 slightly belO"W" vessel head flange.
Bead detensioriad vith bol:s in p.t..ce.
Man~ay cover cm top of O'!SG removed.
Tygon tubing ai:t*ched ta lower vent:s of :R.C'S hct leg far RCS level. indication.
Dei:.s.y heat lcop 2 ~- $errl.ce for RCS cooling.
- l. ill. nou-tn,1cle.ar inst:rucent: (mtI) power and Static Voltage '.Regula.tor Y..\\..~
supplied f:cm 13.8 F:'1 Bus B 'Tia BBBF2.
l.3.8 K. B\\:.S A energized bu~ not c:ca:mec:tad..
RPS and. S]"AS Ch~nels l-. aud 3 bein,g suppl:lc!ld fx-om Y.AR *
.3.
Equipment* Out cf Sel:"\\7ic:e
- 4.
!raa~e:s for ccu:a~nc spray and. mI pu::ps racl<.ed cue.
2:00 p.m.
2:33 p.m.
SEQUENCE OF EV!?tTS Loss cf powe-r*to Busses E-1 and F-2 (oon-e.ssentia.l 480 **
VAC)
CAUSZ/COMMENTS
~rouud shor~ on 13.8 KV braaker HBBF2
~hich caus~d b=eaker to op.en.. This intarrupt~d pover tc busses E-2 and P-2 wltic:l:l wera supplying all non-nuclear**
inst~~nt: (N!1I) pewer,_ cban12els l and 3 o-£ the Reactol:' PTotect::i.ou Sys :.em (lU'S) and
.tha Saf.sty features.Act"Uat::!.on Signal (S7...\\S),
the computer, aud nch of the coutrol roo-c ind~cators.
SFAS Levei 5 (recircu-
?'we out of fclll" log~c ~r.I.pped upon loss
.la1:j,C':l ~ode) actua-cf 3usses Z-2 ~r..d F-2.
Ac-:uat:!.ou c.au~ed
- tion.
~ccs Pl.Z:? ~u~:~on val~~3 frcm contai~c~nt sump _~o open and ECCS pump $u~:ion valves
- from Bora~ed Water Stor:ge Tank to closa.
During valve travel tim~s, gravity flo~
pau existed f-rotll :B~ST to coutai::im~t sg::p.
Decay Heat "(low Operator turned off only operating DB pressure sa!ety in-pu~p to £voi.d s~illagQ of ~CS water to jeccion) f~ov secured cac.taill!:lc~~ via ~h~ t:ygcn tub~g for ~CS
. by cperator level indicstion and open SG ma.nvay.
Partial rest.oration of power P~e: ta ~us E-2*a~a SYAS. channels land 3 restored a.lo-ng with one channel of h~I. This
~estcred.z.1.1 ~~~P~~~-1 R-*--
~--
-A-~
~-----
1 I
f
_\\'
- , 2:44 p.m.
- .3:34 p.m.
4:00 p.:.
to 4:06 ~.m.
4:25 p.m.
4:46 p.m.
5:40 p.m.
'*~ ;;~ *..:..... ;
Attachment to IE ~ormation Notice No. 80-20
- 2. -
EVENT
. At:empt. co reestab~
- lish DH flow Scurce ltaTige Channel 2 energi.2:ed.
CAUSE/ COM?inrrs Started DH p~mp 1-2 than stn~ped it ~en ic was deter.mined that air was in suct:lott l.:ina.
Fump secured to p~eveut-da~ge.
Restorat~on of Busses Busses rest:ored seq,uentually as efforts (4SO VAC) F-2., F-21, progressed t:o i.sol.ata g-round falllt.
- F-2.2, and, F-23 DB flew restored i
Ccntain:men-c sump pu::p breaka:rs op~ned DH pump 1-2 sta~~eg af te~ ~~nting. RCS telllperature at 170 F. DB fl~ bypass~ng
.fgoi;56F*. Inc:cre TC' a b~ing taken and ~:d.~
Precautionary m~a..sur-e to as.sure containment:..
S'tJmP ~at~r =~=~ ~~ST r=-::.ained ~ sontai~ent~
Incore TC's range frQm 161 to 164 F.
C01nputer re~u:rned to Incore TC's. range from l.SS to* 160°F.
- . ser.vi.ce...
- ~
6:24 p.m.
DB f lcw direc~ed
'through cgolar*
- RCS eooldet.-n established_ a~ less Shan 25°F pe-r hour.
RCS t.emp~'t"atu:re *t l.50 F. I:i::u:cre.o.C'~
- j.*:-~.
PCn.ier ~ompletely
- -,restored
. -* ~.---
- ,,...~ --
..:~.-:..--*
range frc~ 151 to ~acr.
RCS temper.atu~e ae app-ro:dJ::iat:ely ll5°l".
~. ~.
STATUS OF DAVIS-BESSE l A.~ RECOVERY FROM LOSS OF POYER. TO BUSS'ES E-2 AND :F-2:
..j;
- .. ~
- I>!
. *:'l~
- ..71..**
0
. Refuali:ag mode with RCS. tet:1Perature at 115 F and level slightly below vessel head, flange.
Head detznsio;ied with bol~s in place. Hanway cove~ Qn tcp cf O'!SG re-coved.
Tygon t:ubitig-attached to lcwer vents cf n.cs hoe leg fo-r RCS level indicaEio~. Decay heat loop 2 in service for RCS cooling.
~~
-~-.. =~~-: ~~~S: --.
- 2. Bus E be-~g*;:°St.-rpplied frg:: l3. 8 "rV 3us A via breaker HAAE2 and Eus F-2 being sup-plied fr~ 13. S KV B1'.1s ! via breaker H.BB:F2.
- 3..... :l)ec:ay beat loop filled.., all tags c1ear. Haintanance wcrk restricted so
'restorat::icn of sys'tem ¢11 be less than tvo hours.
- 4. ECCS p'l,l.mp suction valv~ "(DB-9A and DB-9B) frcm ccnt~ent Sw:::tp closed and b~eakers racked out.
T"nis vil.l pr~vent the suction of air into the decay
- 1
,'.:\\.-*
. ~I, Attachme.nt to IE eormation Notice No. ao:...20.
.. *i
{..
t heat loop during a level S act:ua.t1.cn (recirculation mode) "When there is no vaeer in ehe.sutnp.
S.
Equip~ent Out of Service:
'E?nergency Diesel Generator l - maintmuince
- 6.
Breake~s for con~ainment spray and EPI pumps raekad ouee
~.. *-*
~ :_......
~:.~.**
____ L
Bulletin No.
80-06 79-03A ao.:.01 80-08 80-09 80-10 80-11 ENCLOSURE 2 RECENTLY ISSUED IE BULLETINS Subject Date Issued Engineered Safety 3/13/80 Feature (fSF) Reset Controls longitudinal Weld 4/4/80 Defects in ASME SA-312, Type 304 Stainless Steel Pipe BWR Jet Pump Assembly 4/4/80 Failure Examination of Con-4/7/80 tai nment Liner Penetration Welds Hydromotor Actuator 4/17/80 Deficiencies Contamination of
.5/6/80 Nonradioactive System and Resulting Potential for Unmoni-tored, Uncontrolled Release to Environment Masonry Weld Design 5/8/80 IE Bulletin No. 80-12 Date: May 9, 1980 Page 1 of 1 All Power Reactor Facilities with an Operating.License (OL) (For Action)
Al1 Power Reactor
~acilities with a Construction Permit (CP) (For Information)
All Power Reactor Facilitie~ with an*
. BWR 3 & 4 1 s with 0 L (For Action)
BWR 1s with CP (For Information)
All Power Reactor Facilities with an OL or CP All Power Reactor Facilities with an OL or CP All Power Reac-tors with OL (for action) with CP (for information)
All Power Reactor Facilities with an OL, Except Salem 2