Information Notice 1987-49, Deficiencies in Outside Containment Flooding Protection
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
of the process fluid above 2120F would flash to steam as it exited the rupture.
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
Technical Contact:
Kevin P. Wolley, AEOD
(301) 492-8373 Attachment:
List of Recently Issued NRC Information Notices
Attachment
October 9. 1987
LIST OF RECENTLY
ISSUED
INFORMATION
NOTICES 1987
-A_n
._ -
lnrorr tlon
Dte oT
Notice No.
87-48
87-47
87-46
87-45
87-44
87-43
87-42
87-41
87-40
Subject
Issuance
Information
Concerning the
10/9/87 Use of Anaerobic Adhesive/
Sealants
Transportation of Radio-
10/5/87 graphy Devices
Undetected Loss of Reactor
9/30/87 Coolant
Recent Safety-Related
9/25/87 Violations
of NRC
Requirements by Industrial
Radiography
Licensees
Thimble Tube Thinning in
9/16/87
Westinghouse Reactors
Gaps in Neutron-Absorbing
9/8/87 Material
in High-Density
Spent Fuel Storage Racks
Diesel Generator Fuse
9/4/87 Contacts
Failures
of Certain 8rosn
8/31/87 Boveri
Electric
Circuit
Breakers
Rackseatlng Valves Routinely 8/31/87 to Prevent Packing Leakage
Issued to
All nuclear power
reactor facilities
All NRC licensees
authorized to ans- facture, distribute
and/or oporate radio- graphic
exposure
devices and/or
source changers.
All PWR facilities
All NRC licensees
authorized to possess
and use sealed sources
for industrial radio- graohy.
All PR facilities
employing a W nuclear
steaa supply systen
All nuclear pouer
reactor facilities
All nuclear power
reactor facilities
All nuclear power
reactor
facilities
All nuclear power
reactor facilities
-
- Operating License
- Construction Permit
UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 205557
OFFICIAL BUSINESS
PENALTY FOR PRIVATE USE. S300
FIRST CLASS MAIL
POSTAGE E FEES PAID
PERMIT No. G-R7
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
Technical Contact:
Kevin P. Wolley, AEOD
(301) 492-8373 Attachment:
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCES
Y' 5/.87
- IRB:DOA:AEOD
EWeiss
09/15/87
- C/OGCB:DOEA:NRR *PPMB:ARM
CHBerlinger
TechEd
10/01/87
09/23/87
- C/IRB:DOA:AEOD
- D/DOA:AEOD
KEPerkins
RLSpessard
09/15/87
09/17/87
- OGCB:DOEA:NRR
RJKiessel
09/14/87
- IRB: DOA: AEOD
KPWolley
09/15/87 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
Technical Contact:
Kevin P. Wolley, AEOD
(301) 492-8373 Attachment:
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCES
- OGCB:DOEA: NRR
RJKlessel
09/14/87
- IRB:DOA:AEOD
KPWolley
09/15/87 D/DOEA:NRR
CERossi
09/ /87
- IRB:DOA:AEOD
EWeiss
09/15/87
"O
C/OGCB:DOEA:NRR
CHBerlinger
3/ / /87
- C/IRB:DOA:AEOD
KEPerkins
09/15/87
- PPMB:ARM
TechEd
09/23/87
- D/DOA:AEOD
RLSpessard
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
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
Technical Contact:
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
I RBDOA:AEOD
IRBXJA :AEOD
C/I
D/DOt;4gtr
RJKiessel
KPWolley
EWeis
KEP Ts
RLSpbssa d,
09liq /87
09/6/87
09// /87
09/e /87 O9//7/87