Information Notice 1987-49, Deficiencies in Outside Containment Flooding Protection

Deficiencies in Outside Containment Flooding Protection

ML031130305
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	10/09/1987
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-87-049, NUDOCS 8710050371
Download: ML031130305 (7)

SSINS No.: 6835 IN 87-49 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 October 9, 1987 NRC INFORMATION NOTICE NO. 87-49: DEFICIENCIES IN OUTSIDE CONTAINMENT

FLOODING PROTECTION

Addressees

All nuclear power reactor facilities holding an operating license or a con- struction permit.

Purpose

This notice is provided to alert recipients to a potentially significant problem

pertaining to the flooding of safety-related equipment as a result of the inade- quate design, installation, and maintenance of features intended to protect

against flooding. It is expected that recipients will review the information

for applicability to their facilities and consider action,'if appropriate, to

preclude a similar problem. However, suggestions contained in this notice do

not constitute NRC requirements; therefore, no specific action or written'

response is required.

Description of Circumstances

Beaver Valley Power Station, Unit 2 In September 1986, during an Engineering Assurance Program, an incorrect, non- conservative assumption in the outside containment flooding analysis was dis- covered. After this assumption was corrected, a reanalysis showed that without

operator action, (1) higher flooding levels would occur in the auxiliary and

service buildings than were originally expected and (2) essential Class lE

floor-mounted switchgear in the-service building could be affected, jeopard- izing safe shutdown capability.

The analysis in question addresses A double-ended rupture of a main feedwater

line in the service building in which it was erroneously assumed that 100 percent

0F would flash to steam as it exited the rupture.

of the process fluid above 212 Reanalysis showed that, in fact, only about 25 percent of the escaping feedwater

would flash, leaving the remaining 75 percent in a liquid form 'that would

contribute to flooding.

8710050371

IN 87-49 October 9, 1987 The Class lE equipment threatened in this scenario is not located in the im- mediate vicinity of the postulated feedwater line break, but is several levels

lower in the service building and would be flooded-by water flowing through

door openings.

To limit the consequences of this postulated flooding event to an acceptable

level, the licensee changed plant operating procedures to require manual trip- ping of the main feedwater pumps if a reactor trip occurs on steam flow/feed

flow mismatch. Since a reactor trip on this signal could indicate a feedwater

line break, securing the main feed pumps would minimize the amount of water

pumped out of the break. Also, the licensee installed gaskets on doors to

prevent the flood water from reaching Class lE equipment. In addition, a

service building wall blowout panel, previously determined as necessary to

mitigate the temperature and pressure effects of a main steam line break, has been installed at floor level to also provide for flooding protection.

Trojan Nuclear Plant

In March 1987, during a review of the turbine building flooding design basis

analysis it was found that the flood relief louvers in the turbine building

wall would not pass sufficient flow to prevent flooding of safety-related

equipment in the event of a break of the main circulating water system.

The major assumptions used in the main circulating water system break analysis

were that (1) full-diameter breaks would occur simultaneously in both circu- lating water pipes at the condenser inlet and (2)the motor-operated valves at

the suction and discharge of both main circulating water pumps would fail to

close. It was originally believed that the flooding expected under these

conditions--would -be-shunted to-the exterior- of-the-turbine-bui4ding with-ruv.

detrimental effect. Further review has shown, however, that the flooding

relief capacity called for in the original plant design would be too small

to prevent overflow of flood barriers in the turbine building. Overflow of

these barriers would flood the auxiliary feedwater pumps and emergency diesel

generators.

In addition to the turbine building flooding concern described above, omission

or degradation of originally installed flood protection design features were

identified in several other areas: (1) drains in the auxiliary feedwater pump

room and service water strainer pit did not have required check valves installed;

(2) although the emergency diesel generator room drain line check valve was

properly installed, it was blocked open by a 1-foot long wooden 2 X 4; and

(3) an auxiliary building pipeway flood barrier intended to protect a centri- fugal charging pump had not been installed. In each case, the potential existed

for equipment important to the plant's safe shutdown capability to become

disabled as a consequence of a flooding event.

IN 87-49 October 9, 1987 To correct these problems, the licensee installed the missing check valves and

flood barrier, and removed debris from drain lines as necessary. A preventive

maintenance program is being developed to ensure that flood protection features

are inspected periodically. The flood relief louver problem was addressed by

building up the turbine building flood barriers an additional 12 inches.

Pending development of a modified design, the portion of the turbine building

wall that formerly housed the louvers will remain open. Since the licensee's

reassessment led to the conclusion that the assumption of simultaneous rupture

of both circulating water lines was overly conservative, the turbine building

flooding analysis in the Final Safety Analysis Report will be revised to

postulate the rupture of a single circulating water line. This change, in

conjunction with the programmatic and design changes described above, will

ensure that engineered safeguards features equipment will be protected from

a circulating water line failure.

Nine Mile Point Nuclear Station. Unit 2

In December 1986, it was discovered that a main circulating water piping

failure could disable Class lE electrical equipment and both trains of the

service water system.

An electrical system manhole cover located in the decontamination area of

the turbine building was not watertight. Since electrical duct banks and

conduit running from the manhole also were found not to be fully sealed, flooding paths existed that could make the safety-related service water

pumps and Class lE electrical equipment in the control building inoperable.

This flood protection deficiency was corrected by the installation of a

redesigned, watertight manhole cover, which would prevent entry of flood

water into the affected manhole.

Discussion:

The events described above illustrate the potential for the loss of safe

shutdown capability as a consequence of potential flooding of safety-related

equipment outside containment. A break in the main circulating water system

or main feedwater system has the potential to release an extremely large

volume of water in a very short period of time. Serious consequences may

result if the design features of the plant are not adequate to direct the

resulting flood water safely away from important equipment. Such design

inadequacies may result from (1)the inadvertent use of nonconservative

assumptions in the flooding design analysis, (2) the failure to recognize

all possible flooding flow paths, (3)the failure to install flood protection

features that have been determined to be necessary, or (4) the failure to

properly maintain installed flood protection features.

No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate NRC regional office or this office.

'harles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Kevin P. Wolley, AEOD

(301) 492-8373 Attachment: List of Recently Issued NRC Information Notices

Attachment

IN 87-49 October 9. 1987 LIST OF RECENTLYISSUED

INFORMATION NOTICES1987

---

-A_n

lnrorr tlon

._ -

Dte oT

Notice No. Subject Issuance Issued to

87-48 Information Concerning the 10/9/87 All nuclear power

Use of Anaerobic Adhesive/ reactor facilities

Sealants holding an OLor CP.

87-47 Transportation of Radio- 10/5/87 All NRC licensees

graphyDevices authorized to ans- facture, distribute

and/or oporate radio- graphicexposure

devices and/or

source changers.

87-46 Undetected Loss of Reactor 9/30/87 All PWRfacilities

Coolant holding on OL or CP.

87-45 Recent Safety-Related 9/25/87 All NRClicensees

Violations of NRC authorized to possess

Requirements by Industrial and use sealed sources

Radiography Licensees for industrial radio- graohy.

87-44 Thimble Tube Thinning in 9/16/87 All PR facilities

Westinghouse Reactors employing a W nuclear

steaasupply systen

holding an OL or CP.

87-43 Gaps in Neutron-Absorbing 9/8/87 All nuclear pouer

Materialin High-Density reactor facilities

Spent Fuel Storage Racks holding an OL or CP.

87-42 Diesel Generator Fuse 9/4/87 All nuclear power

Contacts reactor facilities

holding an OL or CF.

87-41 Failuresof Certain 8rosn 8/31/87 All nuclear power

Boveri ElectricCircuit reactorfacilities

Breakers holding an OL or CP.

87-40 Rackseatlng ValvesRoutinely8/31/87 All nuclear power

to Prevent Packing Leakage reactor facilities -

holding an OL or CP.

OL* Operating License

CP* Construction Permit

UNITED STATES FIRST CLASS MAIL

NUCLEAR REGULATORY COMMISSION POSTAGE E FEES PAID

USNRC

WASHINGTON, D.C. 205557 PERMIT No. G-R7 OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE. S300

IN 87-49 October 9, 1987 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate NRC regional office or this office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Kevin P. Wolley, AEOD

(301) 492-8373 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

• C/OGCB:DOEA:NRR *PPMB:ARM

CHBerlinger TechEd

Y' 5/.87 10/01/87 09/23/87

• OGCB:DOEA:NRR *IRB: DOA: AEOD *IRB:DOA:AEOD *C/IRB:DOA:AEOD *D/DOA:AEOD

RJKiessel KPWolley EWeiss KEPerkins RLSpessard

09/14/87 09/15/87 09/15/87 09/15/87 09/17/87 I LAf'

IN 87-XX

October xx, 1987 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate NRC regional office or this office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Kevin P. Wolley, AEOD

(301) 492-8373 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES "O

D/DOEA:NRR C/OGCB:DOEA:NRR *PPMB:ARM

CERossi CHBerlinger TechEd

09/ /87 3/ / /87 09/23/87

• OGCB:DOEA: NRR *IRB:DOA:AEOD *IRB:DOA:AEOD *C/IRB:DOA:AEOD *D/DOA:AEOD

RJKlessel KPWolley EWeiss KEPerkins RLSpessard

09/14/87 09/15/87 09/15/87 09/15/87 09/17/87

IN 87-XX

September xx, 1987 Nine Mile Point Nuclear Station, Unit 2 In December 1986 it was discovered that the potential existed for a main

circulating water piping failure to disable Class 1E electrical equipment and

both trains of the service water system.

An electrical manhole located in the decontamination area of the turbine

building, which would be exposed to flood water from a postulated main circu- lating water pipe break, was found to have a nonwatertight manhole cover.

Electrical duct banks and conduit running from the manhole to the control

building and to the service water pump bays were also found not to be fully

sealed. Therefore, flooding paths were established such that, in the event of

a circulating water piping failure, the safety-related service water pumps and

Class 1E electrical equipment in the control building could have been rendered

inoperable.

This flood protection deficiency was corrected by the installation of a rede- signed, watertight manhole cover, which would prevent entry of flood water Into

the affected manhole.

Discussion:

The events described above illustrate the potential for the loss of the plants'

safe shutdown capability due to flooding of safety-related equipment outside

containment. A break in the main circulating water system or main feedwater

system has the potential to release an extremely large volume of water in a

very short period of time into the area around the break. Serious consequences

may result if the design features of the plant are inadequate to direct the

resulting flood safely away from important equipment. Such inadequacies may

result from the inadvertent use of nonconservative assumptions in the flooding

analysis, failure to recognize all possible flooding flow paths, failure to

install flood protection features that have been determined to be necessary, or

failure to properly maintain installed flood protection features.

No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate NRC regional office or this office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Kevin P. Wolley, AEOD

(301) 492-8373 Attachment: List of Recently Issued NRC Information Notices

D/DOEA:NRR C/OGCB:DOEA:NRR PPMB:ARM 4 CERossi CHBerlinger TechEd

09/ /87 09/ 09/_2487 OGCB:DOEA:NRR IRBDOA:AEOD IRBXJA :AEOD C/I EOD D/DOt;4gtr

RJKiessel KPWolley EWeis KEP Ts RLSpbssa d,

09liq /87 09/6/87 09// /87 09/e /87 O9//7/87