ML18139A281

Forwards IE Bulletin 80-12, Decay Heat Removal Sys Operability. Requires Action & Response within 30 Days. IE Info Notice 80-20, Loss of Decay Heat Removal Capability at Davis-Besse Unit 1 While in Refueling Mode Encl

ML18139A281
Person / Time
Site:	Surry, North Anna
Issue date:	05/09/1980
From:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:	Ferguson J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
References
NUDOCS 8006040248
Download: ML18139A281 (13)

Text

• .

I I e

e UN.ITED STATES NUCLEAR REGULATORY COMMISSION REGION II In Reply Refer To:

RII:JPO QJF-2ao. sO:Zat:::,

50-338 101 MARIETTA ST., N.W., SUITE 3100 ATLANTA, GEORGIA 30303 MAY 9 1980

'Virginia Electric and Power Company Attn:

J. H. Ferguson Executive Vice President-Power P. 0. Box 26666 Richmond, Virginia Gentlemen:

23261 Enclosed is IE Bulletin No. 80,:..12 which requires action by you with regard to your PWR power reactor facility(ies) with an operating license.

Should you have any questions regarding the Bulletin or the actions required by you, please contact this office.

Enclosures:

1.

IE Bulletin No. 80-12 2.-

List of Recently Issued IE Bulletins Sincerely,

_ James P. O'Reilly Director

~

I I

L

Virginia Electric and Power Company cc w/encl:

e W.R. Cartwright, Station Manager Post Office Box 402 Mineral, Virginia 23117 P. G. Perry Senior Resident Engineer Post Office Box 38 Mineral, Virginia 23117 J. L. Wilson, Manager Post Office Box 315 Surry, Virginia 23883

~

. --: ";'"""*-*--*~-.. -

IYIAY 9 1980 e

UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 May 9, 1980 DECAY HEAT REMOVAL SYSTEM OPERABILITY

==

Introduction:==

. SSINS No. :

6820 Accession No.:

8005050053 IE Bulletin No. 80-12 The intent of this Bulletin is to improve nuclear power plant safety by reducing

, the likelihood of iosing decay heat removal (DHR) capability in operating pressµrized 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 concurrent 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 DHR during all modes of operation.

(Note: A redundant means could be provided by having DHR 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 DHR 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 1 incident of April 19, 1980, DHR capability was restored prior to exceeding the specified RCS temper-ature limit for the specific mode of operation.

Nonetheless, the risk and frequency associated with such events dictate 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 Enclosure 1).. Two factors identified as major contributors to the Davis-Besse event in the Information Notice are:

(1) extensive maintenance 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.

I ACTIONS TO BE TAKEN BY LICENSEES OF PWR FACILITIES:

1.

Review the circumstances and sequence of events at Davis-Besse as des-cribed in Enclosure 1.

2.

Review your facility(ies) for all DHR degradation events experienced, especially for events similar to the Davis-Besse incident.

e IE Bulletin No. 80-12 May 9, 1980 Page 2 of 3

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 reliability during the refueling and cold shutdown modes of operation.

4.

Analyze your procedures for adequacy of safeguarding a$ains_t loss of redundancy and diversity of DHR capability.

5.

,'Analyze your procedures for adequacy of responding to* DHR loss events.

Special emphasis should be placed upon responses when maintenance or refueling activities degrade the DHR 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 DHR 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 DHR train and a readily accessible source of borated water to replenish any loss of inventory that might occur subsequent to the loss of the available DHR 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 DHR 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 considerc-the following: (1) limiting maintenanGe 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) ag~inst DHR degradation, including your assessment of their adequacy.

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 affir-mation and submitted within the _time specified above.

Reports shall be submitted

e IE Bulletin No. 80-12 May 9, 1980 Page 3 of 3 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, B180225 (R0072); clearance expires 7-31-80.

Approval was given under a blanket clearance specifically for identified generic problems.

Enclosure:

IE Information Notice No.;80-20

'*'J' ¥ *: * *~* :.. 4:: ~..,li,.

~

IE Bulletin No. 80-12 May 9, 1980 RECENTLY ISSUED IE BULLETINS Bulletin No.

80-12 80-11 80-10 80-09 80-08 80-07 80-06 80-05 79-0lB 80-04 Subject Decay Heat Removal System Operability Masonay Wall Design Contamination of Nonradioactive System and Resulting Potential for Unmonitored, Uncontrolled Release to Environment Hydramotor Actuator Deficiencies Examination of Containment Liner Penetration Welds BWR Jet Pump Assembly Failure Engineered Safety Feature (ESF) Reset Controls Vacuum Condition Resulting In Damage To Chemical Volume Control System (CVCS) Holdup Tanks Environmental Qualification of Class IE Equipment Analysis of a PWR Main Steam Line Break With Continued Feedwater Addition Date Issued 5/9/80 5/8/80 5/6/80 4/17/80 4/7/80 4/4/80 3/13/80 3/10/80 2/29/80 2/8/80 Enclosure Issued To Action for all JJWR'.s w/01.

Infor-mation for all PWR's with Construction Permit and all BWR's.

All power reactor facilities with an 01, except Trojan All power reactor facilities with an 01 or CP All power reactor operating facilities and holders of power reactor construction permits All power reactors with a CP and/or OL no later than April 7, 1980 All GE BWR-3 and BWR-4 facilities with an OL All power reactor facilities with an OL All PWR power reactor facilities holding OLs and to those with a CP All power reactor facilities with an 01 All PWR reactor facilities holding OLs and to those nearing licensing

e e

UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C. 20555 May 8, 1980 SSINS*No.:

6870 Accession No.:

8002280671 IE Information Notice 80-20 LOSS OF DECAY HEAT REMOVAL CAPABILITY AT DAVIS-BESSE ONIT--i. WHILE IN A REFUELING MODE Descri~tion of Circumstances:

On April 19, 1980, decay heat removal capability was lost at Davis-Besse Unit 1 for approximately two and one-half hours.

At the time of the event, the unit was in a refueling 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 Enclosure A, Status of Davis-Besse 1 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; Source Range Channel 2; Decay Heat Loop No. 1; Station Battery IP and IN; Emergency Diesel-Generator No. l; 4.16 KV Essential Switchgear Bus Cl; and 13.8 KV Switchgear Bus A (this bus was energized but not aligned).

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 Protec-tion System (RPS) and Safety Features Actuation System (SFAS) were being ener-gized 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

.. 111hich the loss (or actuation) of any two input signals results in the actuation of all four output channels (i.e., Channels'! and 3, and Channels 2 and 4), the

.Joss of power to Channels 1 and 3 bistables also resulted in actuation of SFAS

• channels 2 and 4.

• The actuation of SFAS Channels 2 and 4, in tµm, affected Decay Heat Loop No. 2, the opera~ing 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 - C~ntainoient Spray; and....-,,...c--,~--*~**""...

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e IE Information Notice No. 80-20 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*cooiant 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 approximately 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; (ii) 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 bad been restricted such that two SFAS channels would -not be lost by a s'in;gie event (e.g., serving Channels 1 and 3 from separate sources), this event would have been precluded.

Likewise, if maintenance 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-

~ible to spurious actions than other logic schemes (e.g., a one-out-of-two taken-twice scheme).

This suscep.tibility is amplified when: two SFAS channels are served from one source.

Consequently, when the source feeding SFAS Channels.I.and 3 was lo~t, ~ll*~ive levels of SFAS were actuated.

As stated

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e IE Information Notice No. 80-20 May 8, 1980 Page 3 of 3 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 Channel.

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.

Enclosure:

Davis-Besse Event of April 19, 1980

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e Enclosure A DAVIS-BESSE EVENT OF APRIL 19 1 1980

. -* -.*~,

STATUS OF DAVIS-BESSE l PRIOR TO LOSS OF POWER TO BUSSES E-2 AND F-2:

l. Refueling mode with RCS temperature at 90°F and level slightly below vessel head flange.

Head detensioned with bolts in place.

Hanway cover on tcp of OTSG removed.

T)'gon tubing attached to l~weY vents of RCS hot leg for RCS level indication. Decay heat loop 2 ~n service for RCS co~ling.

~

2'.

All* non-nuclear instrument (NNI) power.and Static Voltage Regulator YAR supplied from 13.8 KV Bus B via ltBBF2.

13.8 K Bus A energized but not connected.

R.PS and SFAS Channels l. and 3 being supplied from YAR..

3.

Equipment Out of Service

a.

Source. lange Channel 2 - Surveillance i

b.

Emergency Diesel Generator l - Maintenance.

c.

Dec:ay Beat Loop 1 - Maintenance.

4.

.Breakers for TIME 2:00 p.m.

containment spray and HPI pumps ~acked ou~.

SEQUENCE OF EVENTS EVENT Loas of power to Bussea E-2 and F-2

{non-essential 480 VAC)

~

.1..,

...... /

~

CAUSE/COMMENTS Ground short on 13 *. 8 KV breaker HB'BF2 which caused breaker to open. This interrupted power to busses E-2 and F-2 vhich vere supplying all non-nuclear*

instrument (NNI) power, channels land 3 of the Reactor Protection Syste= (RPS) and

.the Safety Features Actuation Signal (SFAS) 1 the compuEer 1 and ~uch of the control room indi.cators

• 2:00 p.m.

SFAS Level S (recircu-

~o out of four logic tripped upon loss lation mode.) 'act:ua-of Busses E-2 and F-2.

Actuation caused *

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ECCS Pl.mlP suction valves from containment

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sump to open and ECCS pump suction valves fr01D Borated Yater Storage Tank to close.

During val'V'e travel t:imes *. gravity flaw * *.* *. *

• path existed from ~~ST to containment sump *

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Decay Beat (1°"1.

Operator turned,:,ff only.operating DB..

. pressure safety in-pump to avo:Ld spillage of RCS water co*

L....... ~~.... :---~~---N-.,,..:..--'~-"""*""'... -.. --......... Je~c:l~) fl.o.wJ* se~_ure.d..... cont.ainment v.La the tygon t:_ubin& for ACS -~;:$f.:~_,..;;

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cil;~-~ : level indication and open SG manway...

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2:33 p.m... .. Parc_ial restoration..,;,;:;:(i=>-"'-f:\\::<'i;*:: ..... "-... "*'*/

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• of powar ::

,- Power to Bus E-2 and SFAS ch.ann@ls i ancJ 3, */1 :, ,,,:\\, ; ':~*;\\_*.:. ,. *'restored along vith one ~ha.nnel of NNI. This

• '4 restored all essential power for ECCS.

I' ! I . TI.Ml: 2:44 p.m. .* 3:34 p.m. 4:00 p.m. to 4:06~p.m. 4:2S p.m9 4:46 p.m. S:40 p.m. 6:24 p.m.

• 9:50 p.m.

e e 2 - EVENT Attempt to reestab-lish DH flaw Source llange Channel 2 energized. CAUSE/COMMENTS Started DH pump 1-2 ~en stopped it when. it was determined that air vas in suction line. Pump secured to prevent datna.ge. Restorat~on of Busses Busses restored se~uentually as efforts (480 VAC) F-2, F-21, progressed to isolate ground fault. F-22., and F-23 DB flow restored Conta1nme1't aump pump breakers opened DB pump 1-2 starteg after ~enting. acs temperature at 170 F.DH flow bypassing ~o1,06F~lncore TC's being take~ and maxim~ Precautionary measure to assure containment. sump water from BWST remained 1.n gontainment. Inco~e TC's range from 161 to 164 F. Computer returned to Iucore TC's range from 158 to 160°F.

• erv:1.ce.

DB flow directed -through cooler Power completely restored ~,.,

• *tJ**:

RCS cooldovn established at less than 2S°F per hour. RCS temperature at 1S0°F. Incore TC's range from 151 ~o 1580F. RCS teinperature at approxima~ely l1S°F. ... ?t STATUS OF DAVIS-BESSE 1.AFTER kECOVERY FROM LOSS O'.F POWER TO BUSS£S E-2 At-."'D J'.. 2:

1.

0 Refueling mode vi th JlCS temperature at 115 F anc:! level slightly below vessel head flange. Bead detei1s1oned vitb bolts in place. Hanway cover on top of OTSG removed. Tygon tubing attached t:o lower vents of RCS hot leg for RCS level.

• indication.

Decay baa~ loop_ 2 in a_ervice for RCS cooling.

he:~'

,,-;2 *.. Bus 'E-2 be.ins supplied from.13. 8 EV Bus A via breaker HAAE2 -.nd Bus F*2 being ~~3 ct~ 'i1.)i~1~:;;!~~-~-lied __. from 13.,.8 -~::!t'r:f }'ia. b.~~,~~~r.. -~~F3,~~;t(:t)t } i: :)Wl::*\\1r:::'. *...

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• ' t>eeay beat loop fU1ec1~.all t*gs clear.
• Maintenance w,,ri{res.tricted so
  • • *,~*.:*

restorat.ion of aystem v.l.11 _be leas than aro hours.*.:.: i:*~-~::-:-:. F~-, ~;*:.* i *; ~, -~/\\,**~.. \\.' '. ~

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• ECCS pump au~~iou Yalves (DH-9A and DB-9B). from containment sump closed and 1

~ ~:;_.;;.~.,,~:........ breakers racked.. aut *.,. *..

• vi.11 prevE>>.11,t.the.suction... Df air.. into *.the decay -**-~,.,,.. ~

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heat loop du~ing a level 5 &ctuation (recirculation mode) when there 1s no ~ater in the sump.

5.

Equipcent Out of Service: t~ergency Diesel Ge~erator 1 - maintenance

6. Breakers fer containment spray and BPI pumps racked out *

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e IE Information Notice No. 80-20 May 8, 1980 RECENTLY ISSUED IE INFORMATION NOTICES Information Notice No. Subject Date Issued 80-20 80-19 80-18 80-17 80-16 80-15 80-14 80-12 80*11 Loss of Decay Heat Removal 5/8/80 Capability at Davis-Besse Unit 1 While in a Refueling Mode NIOSH Recall of Recircu-5/6/80 lating-Mode (Closed-Circuit) Self-Contained Breathing Apparatus (Rebreathers) Possible Weapons Smuggling 5/5/80 Pouch Potential Hazards Associated 5/5/80 With Interchangable Parts On Radiographic Equipment Shaft Seal Packing 4/29/80 Causes Binding In Main Steam Swing Check And Isolation Valves Axial (Longitudinal) Oriented Cracking In Piping Safety Suggestions From Employees General Electric Type SBM -Control Switches - Defective Cam Followers Instrument Failure Causes Opening of PORV and Block Valve 4/21/80 _4/2/80 4/2/80 3/31/80 . 7**;>_c-:.*

• • General Problems, with ASCO 3/14/80 -

__ - _ Valves in Nuclear Application -:, ;-~~:***,.-Including Fire Protection Systems ... - " - -*-.,:~.. i-,;. -.. -..;*

• .......::::~~..:--:* -* ~:.' -..

Enclosure Issued To All holders of power reactor operation Lic~nses or construc-tion permit All holders of a power reactor OL, Research Reactor License, Fuel Cycle Facility License and Priority I Material License All power reactor facilities with an OL, fuel fabrication and processing facilities and Materials Priority I licensees (processors and distributors) All radiography Licenses All power reactor facilities in your Region with an OL or CP All Light Water Reactor Facilities holding power reactor OLs or CPs All power reactor facilities with an 01 or CP All light water reactor facilities holding power reactor OLs or CPs Ail holders of power reactor OLs and CPs All holders of Reactor OL, CP, fuel fabrica-tion and processing facilities '}}