Information Notice 1996-60, Potential Common-Mode Post-Accident Failure of Residual Heat Removal Heat Exchangers: Difference between revisions

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{{#Wiki_filter:K>I UNITED STATES NUCLEAR REGULATORY
{{#Wiki_filter:I


COMMISSION
K>
                                        UNITED STATES


===OFFICE OF NUCLEAR REACTOR REGULATION===
NUCLEAR REGULATORY COMMISSION
WASHINGTON, DC 20555-0001 November 14, 1996 NRC INFORMATION


NOTICE 96-60: POTENTIAL
OFFICE OF NUCLEAR REACTOR REGULATION


COMMON-MODE
WASHINGTON, DC 20555-0001 November 14, 1996 NRC INFORMATION NOTICE 96-60: POTENTIAL COMMON-MODE POST-ACCIDENT


POST-ACCIDENT
FAILURE OF RESIDUAL HEAT REMOVAL HEAT


===FAILURE OF RESIDUAL HEAT REMOVAL HEAT EXCHANGERS===
EXCHANGERS


==Addressees==
==Addressees==
All holders of operating
All holders of operating licenses or construction permits for nuclear power reactors.
 
licenses or construction
 
permits for nuclear power reactors.


==Purpose==
==Purpose==
The U.S. Nuclear Regulatory
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert


Commission (NRC) is issuing this information
addressees to a potential common-mode post-accident failure of boiling water reactor


notice to alert addressees
(BWR) residual heat removal (RHR) heat exchangers. It is expected that recipients will


to a potential
review the information for applicability to their facilities and consider actions, as


common-mode
appropriate, to avoid similar problems. However, suggestions contained in this information


post-accident
notice are not NRC requirements; therefore, no specific action or written response is


failure of boiling water reactor (BWR) residual heat removal (RHR) heat exchangers.
required.


It is expected that recipients
Background


will review the information
The NRC staff issued Information Notice 96-45, 'Potential Common-Mode Post-Accident


for applicability
Failure of Containment Coolers," on August 28, 1996, to alert licensees to a potential


to their facilities
failure mechanism of containment coolers during a design-basis loss-of-coolant accident


and consider actions, as appropriate, to avoid similar problems.
(LOCA) with a concurrent loss of offsite power or with a delayed sequencing of safety- related equipment. Specifically, if the containment coolers are exposed to forced


However, suggestions
convection in a post-LOCA environment without cooling water flow, boiling may occur on


contained
the stagnant cooling water side of the containment coolers. When cooling water flow is


in this information
subsequently reinitiated, the steam voids will collapse and may create significant


notice are not NRC requirements;
hydrodynamic loads (waterhammer). The waterhammer may threaten the integrity of the
therefore, no specific action or written response is required.Background


The NRC staff issued Information
containment cooler or the associated cooling water piping. Generic Letter 96-06,
"Assurance of Equipment Operability and Containment Integrity During Design-Basis


Notice 96-45, 'Potential
Accident Conditions," issued on September 30, 1996, also addressed this issue.


Common-Mode
==Description of Circumstances==
A potential waterhammer scenario in the service water side of the RHR heat exchanger


Post-Accident
was identified at the LaSalle Nuclear Station. The postulated phenomenon is analogous


Failure of Containment
to that identified for containment coolers in Information Notice 96-45 and Generic


Coolers," on August 28, 1996, to alert licensees
Letter 96-06.


to a potential failure mechanism
9611070081
                    96110460                                            7008 t04do                                  aa{\


of containment
IN 96-60
                                                                          November 14, 1996 At LaSalle, a BWR 5 plant, the top of the vertical RHR heat exchanger is the high point of


coolers during a design-basis
the RHR service water system and is at an elevation that is higher than that of the ultimate


loss-of-coolant
heat sink by approximately 9 meters (30 feet) for normal lake levels. The resultant


accident (LOCA) with a concurrent
pressure in the heat exchanger tubes in a standby condition is estimated to be between


loss of offsite power or with a delayed sequencing
7000 and 21,000 pascals (1 and 3 psia), with associated saturation temperatures between


of safety-related equipment.
430 and 600 C (1100 and 1400 F). Boiling will occur in these tubes if these temperatures


Specifically, if the containment
are exceeded. Under low lake levels, the licensee found that voiding would occur in the


coolers are exposed to forced convection
top of the tubes regardless of temperature.


in a post-LOCA
At LaSalle, the RHR system is lined up so that flow will go through both the RHR heat


environment
exchanger and a bypass valve whenever the RHR system is initiated in its safety injection


without cooling water flow, boiling may occur on the stagnant cooling water side of the containment
(low pressure coolant injection) mode. The RHR service water flow to the tube side of the


coolers. When cooling water flow is subsequently
RHR heat exchangers does not start automatically on a safety injection signal. Emergency


reinitiated, the steam voids will collapse and may create significant
operating procedures direct that the RHR service water pumps be started manually within


hydrodynamic
the first 10 minutes of an accident.


loads (waterhammer).
It is postulated that during a LOCA, water from the suppression pool, which could start


The waterhammer
from the technical specification allowable 41 0 C (1050 F), could quickly be heated to


may threaten the integrity
88OC (1900 F). When the relatively hot suppression pool fluid would be pumped through


of the containment
the RHR heat exchanger, it would boil the stagnant low pressure service water. When


cooler or the associated
RHR service water flow would subsequently be manually initiated, the steam voids would


cooling water piping. Generic Letter 96-06,"Assurance
collapse and might create significant hydrodynamic loads. The hydrodynamic loads might


of Equipment
impair the integrity of the heat exchangers or the associated service water piping. This


Operability
scenario does not occur during normal operation of the RHR system in the shutdown


and Containment
cooling mode because the RHR service water system is started first to ensure that cooling


Integrity
flow is established before h~ot fluid is introduced into the heat exchangers.


During Design-Basis
Both units at the LaSalle Nuclear Station are currently shut down. The licensee continues


Accident Conditions," issued on September
to assess this issue and will ensure operability of the RHR heat exchangers before restart.


30, 1996, also addressed
The licensee is considering the installation of a keep-fill system on the RHR service water


this issue.Description
system to keep the heat exchangers pressurized.


of Circumstances
Discussion
 
A potential
 
waterhammer
 
scenario in the service water side of the RHR heat exchanger was identified
 
at the LaSalle Nuclear Station. The postulated
 
phenomenon
 
is analogous to that identified
 
for containment


coolers in Information
The RHR heat exchangers provide an important safety function for long term heat removal.


Notice 96-45 and Generic Letter 96-06.96110460 7008 9611070081 t04do aa{\
The postulated failure scenario could cause a common failure of the RHR heat exchangers, thereby potentially challenging this function. In addition, a structural failure of the RHR
IN 96-60 November 14, 1996 At LaSalle, a BWR 5 plant, the top of the vertical RHR heat exchanger


is the high point of the RHR service water system and is at an elevation
heat exchangers could create a containment bypass release path and divert low pressure


that is higher than that of the ultimate heat sink by approximately
coolant injection flow. An individual plant vulnerability to these postulated failures


9 meters (30 feet) for normal lake levels. The resultant pressure in the heat exchanger
depends on a number of factors. The physical configuration of the RHR service water


tubes in a standby condition
system and RHR heat exchanger, the operational alignment of the heat exchanger isolation


is estimated
valves, the sequencing of the RHR service water pumps, and other site-specific parameters


to be between 7000 and 21,000 pascals (1 and 3 psia), with associated
have an effect on facility vulnerability to this potential failure mode.


saturation
IN 96-60
                                                                      November 14, 1996 This information notice requires no specific action or written response. If you have any


temperatures
questions about the information in this notice, please contact one of the technical contacts


between 430 and 600 C (1100 and 1400 F). Boiling will occur in these tubes if these temperatures
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.


are exceeded.
I    Thomas T. Martin, Director


Under low lake levels, the licensee found that voiding would occur in the top of the tubes regardless
Division of Reactor Program Management


of temperature.
Office of Nuclear Reactor Regulation
 
At LaSalle, the RHR system is lined up so that flow will go through both the RHR heat exchanger
 
and a bypass valve whenever the RHR system is initiated
 
in its safety injection (low pressure coolant injection)
mode. The RHR service water flow to the tube side of the RHR heat exchangers
 
does not start automatically
 
on a safety injection
 
signal. Emergency operating
 
procedures
 
direct that the RHR service water pumps be started manually within the first 10 minutes of an accident.It is postulated
 
that during a LOCA, water from the suppression
 
pool, which could start from the technical
 
specification
 
allowable
 
41 0 C (1050 F), could quickly be heated to 88OC (1900 F). When the relatively
 
hot suppression
 
pool fluid would be pumped through the RHR heat exchanger, it would boil the stagnant low pressure service water. When RHR service water flow would subsequently
 
be manually initiated, the steam voids would collapse and might create significant
 
hydrodynamic
 
loads. The hydrodynamic
 
loads might impair the integrity
 
of the heat exchangers
 
or the associated
 
service water piping. This scenario does not occur during normal operation
 
of the RHR system in the shutdown cooling mode because the RHR service water system is started first to ensure that cooling flow is established
 
before h~ot fluid is introduced
 
into the heat exchangers.
 
Both units at the LaSalle Nuclear Station are currently
 
shut down. The licensee continues to assess this issue and will ensure operability
 
of the RHR heat exchangers
 
before restart.The licensee is considering
 
the installation
 
of a keep-fill
 
system on the RHR service water system to keep the heat exchangers
 
pressurized.
 
Discussion


The RHR heat exchangers
Technical contacts: V. Patricia Lougheed, Region IlIl


provide an important
(630) 829-9760
                      E-mail: vpl@nrc.gov


safety function for long term heat removal.The postulated
James Tatum, NRR


failure scenario could cause a common failure of the RHR heat exchangers, thereby potentially
(301) 415-2805 E-mail: jetl @nrc.gov


challenging
John Tappert, NRR


this function.
(301) 415-1167 E-mail: jrt@nrc.gov


In addition, a structural
Attachment: List of Recently Issued NRC Information Notices


failure of the RHR heat exchangers
/f 7A~4*a,,                            9ikE


could create a containment
I,-ACED


bypass release path and divert low pressure coolant injection
f)
                                                                    Attachment


flow. An individual
IN 96-60
                                                                    November 14, 1996 -
                                      LIST OF RECENTLY ISSUED


plant vulnerability
NRC INFORMATION NOTICES


to these postulated
Information                                      Date of


failures depends on a number of factors. The physical configuration
Notice No.           Subject                      Issuance    Issued to


of the RHR service water system and RHR heat exchanger, the operational
96-59          Potential Degradation of         10/30196  All holders of OLs or


alignment
Post Loss-of-Coolant                          CPs for nuclear power


of the heat exchanger
Recirculation Capability                      reactors


isolation valves, the sequencing
as a Result of Debris


of the RHR service water pumps, and other site-specific
96-58            RCP Seal Replacement with        10/30/96  All holders of OLs or


parameters
Pump on Backseat                            CPs for pressurized-water


have an effect on facility vulnerability
reactors


to this potential
96-57          Incident-Reporting Require-        10/29/96  All U.S. Nuclear


failure mode.
ments Involving Intakes,                      Regulatory Commission


IN 96-60 November 14, 1996 This information
During a 24-Hour Period                      licensees


notice requires no specific action or written response.
That May Cause a Total


If you have any questions
Effective Dose Equivalent


about the information
in Excess of 0.05 Sv


in this notice, please contact one of the technical
(5 rems)
96-56          Problems Associated with          10/22/96  All holders of OLs or


contacts listed below or the appropriate
Testing, Tuning, or Reset-                    CPs for nuclear power


Office of Nuclear Reactor Regulation (NRR) project manager.I Thomas T. Martin, Director Division of Reactor Program Management
ting of Digital Control                      reactors


===Office of Nuclear Reactor Regulation===
Systems While at Power
Technical


contacts: V. Patricia Lougheed, Region IlIl (630) 829-9760 E-mail: vpl@nrc.gov
OL = Operating License


James Tatum, NRR (301) 415-2805 E-mail: jetl @nrc.gov John Tappert, NRR (301) 415-1167 E-mail: jrt@nrc.gov
CP = Construction Permit


Attachment:
N;
List of/f 7A~4*a,, Recently Issued NRC Information
                                                                            IN 96-60
                                                                            November 14, 1996 This information notice requires no specific action or written response. If you have any


Notices I,-ACED 9ikE
questions about the information in this notice, please contact one of the technical contacts


f)Attachment
listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.


IN 96-60 November 14, 1996 -LIST OF RECENTLY ISSUED NRC INFORMATION
original signed by D. B. Matthews


NOTICES Information
homas T. Martin, Director


Date of Notice No. Subject Issuance Issued to 96-59 96-58 96-57 96-56 Potential
/      Division of Reactor Program Management


Degradation
Office of Nuclear Reactor Regulation


of Post Loss-of-Coolant
Technical contacts: V. Patricia Lougheed, Region III


Recirculation
1630) 829-9760
                          E-mail: vpl@nrc.gov


Capability
James Tatum, NRR


as a Result of Debris RCP Seal Replacement
(301) 415-2805 E-mail: jetl @nrc.gov


with Pump on Backseat Incident-Reporting
John Tappert, NRR


Require-ments Involving
(301) 415-1167 E-mail: jrt@nrc.gov


Intakes, During a 24-Hour Period That May Cause a Total Effective
Attachment: List of Recently Issued NRC Information Notices


===Dose Equivalent===
*SEE PREVIOUS CONCURRENCE
in Excess of 0.05 Sv (5 rems)Problems Associated


with Testing, Tuning, or Reset-ting of Digital Control Systems While at Power 10/30196 10/30/96 10/29/96 10/22/96 All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for pressurized-water
Tech Editor reviewed 10/29 DOCUMENT NAME: 96-62.IN


reactors All U.S. Nuclear Regulatory
OFFICE  Contacts*          C/SPLB:DSSA        C/PECB:DRPM      D/DR'I      j


Commission
NAME    PLougheed          TMarsh              AChaffee          Ma


licensees All holders of OLs or CPs for nuclear power reactors OL = Operating
JTatum


License CP = Construction
JTappert                              _  _  _t            -
      DATE    10/30/96            11/04/96          11/06/96          11/1/96 Official Record Copy


Permit
K>
                                                                                                                      IN 96-xx


N;IN 96-60 November 14, 1996 This information
November xx. 1996 This information notice requires no specific action                                            or written response. If


notice requires no specific action or written response.
ss ...                    n


If you have any questions
la  hnir LI t+h    infnrmntinn                  inI. I thic        nnticp                nleacp cnntact


about the information
yJU lidVu alli %4UCaL IUII      aU&IUb    11 1%  I I I Il W Iu


in this notice, please contact one of the technical
14% 1. Il WI I          .1.  l


contacts listed below or the appropriate
.        v      . 1>1w  - -        _
one of the technical contacts listed below or the appropriate Office of                                                                  /
Nuclear Reactor Regul ation (NRR) project manager.


Office of Nuclear Reactor Regulation (NRR) project manager.original signed by D. B. Matthews homas T. Martin, Director/ Division of Reactor Program Management
Thomas T. Martin, Dire                                        r


===Office of Nuclear Reactor Regulation===
Division of Reactor rogram Management
Technical


contacts: V. Patricia Lougheed, Region III 1630) 829-9760 E-mail: vpl@nrc.gov
Office of Nucle                              eactor Regulation


James Tatum, NRR (301) 415-2805 E-mail: jetl @nrc.gov John Tappert, NRR (301) 415-1167 E-mail: jrt@nrc.gov
Technical Contacts:           V. Patricia Lougheed. Re                                n III


Attachment:  
(630) 829-9760
List of Recently Issued NRC Information
                              E-mailt: vpl@nrc. v


Notices*SEE PREVIOUS CONCURRENCE
James Tatum.                  R


Tech Editor reviewed 10/29 DOCUMENT NAME: 96-62.IN OFFICE Contacts*
(301) 415g20
C/SPLB:DSSA
                              E-mail: jetl@nrc.gov


C/PECB:DRPM
Jo zTap ert. NRR


D/DR'I j NAME PLougheed
301) 415-1167 E-mail: jrt@nrc.gov


TMarsh AChaffee Ma JTatum JTappert -_ _ _t DATE 10/30/96 11/04/96 11/06/96 11/1/96 Official Record Copy
Attachment:
1. List of                    Issued NRC Information Notices


K>IN 96-xx November xx. 1996 This information
*SEE PREVIOUS CONCURRENCE


notice requires no specific action or written response.
Tech Editor reviewed 10/29                                      ,24t nrij%      I            4r


If ss ... n hnir t+h infnrmntinn
DOClUMFNT vvv


in thic nnticp nleacp cnntact yJU lidVu alli %4UCaL IUII one of the technical Nuclear Reactor Regul Technical
NAME:    G:\JRT\LSALRHR.IN


Contacts: la aU&IUb LI 11 1% I I I Il W Iu 14% 1. Il WI I I. I .1. .l v w --_ .1>1 contacts listed below or the appropriate
-                          r. - _ .        .    .    ..........


Office of /ation (NRR) project manager.Thomas T. Martin, Dire r Division of Reactor rogram Management
OFFICE      Contacts*        C/SPLB:DSSA*                    C/PECB:DRPM                            D/DRPM


===Office of Nucle eactor Regulation===
NAME      PLougheed        TMarsh                          AChaffee                                Thartin
V. Patricia Lougheed.


Re n III (630) 829-9760 E-mailt: vpl@nrc. v James Tatum. R (301) 415g20 E-mail: jetl@nrc.gov
JTatum


Jo zTap ert. NRR 301) 415-1167 E-mail: jrt@nrc.gov
____  __  Tappert                                                                                  _    _  _  _  _ _ _
      DATE        10/30/96          11/04/96                      11/L& /96                                  11/ /96 UTTIClal Kecr'u                      LUpy


Issued NRC Information
nj


Notices Attachment:
IN 96-xx
1. List of*SEE PREVIOUS CONCURRENCE


Tech Editor reviewed 10/29 DOClUMFNT
November xx. 1996 This information notice requires no specific action or written response. If


NAME: G:\JRT\LSALRHR.IN
you have any questions about the information in this notice. please conta


,24t I nrij% 4r vvv -r. -_ .............OFFICE Contacts*
one of the technical contacts listed below or the appropriate Office of
C/SPLB:DSSA*
C/PECB:DRPM


D/DRPM NAME PLougheed
Nuclear Reactor Regulation (NRR) project manager.


TMarsh AChaffee Thartin JTatum____ __ Tappert _ _ _ _ _ _ _DATE 10/30/96 11/04/96 11/L& /96 11/ /96 UTTIClal Kecr'u LUpy
Thomas T. Martin, Dir dor


IN 96-xx November xx. 1996 This information
Division of Reactor rogram Management


notice requires no specific action or written response.
Office of Nuclear eactor Regulation


If you have any questions
Technical Contacts:  V. Patricia Lougheed. Region    i


about the information
(630) 829-9760
                        Internet: vpl@nrc.gov


in this notice. please conta one of the technical
James Tatum, NRR


contacts listed below or the appropriate
(301) 415-2805 Internet: jetl@nrc.go


Office of Nuclear Reactor Regulation (NRR) project manager.Thomas T. Martin, Dir dor Division of Reactor rogram Management
John Tappert. NRR


===Office of Nuclear eactor Regulation===
(301) 415-1167 Internet: jrt@nr    gov
Technical


Contacts:  
Attachment:
V. Patricia Lougheed.
  1. List of Recently Issued NRC I ormation Notices


Region i (630) 829-9760 Internet:  
Tech Editor re ewed 10/29 DOCUMENT NAME    G:\JRT\LSALRHR.IN
vpl@nrc.gov


James Tatum, NRR (301) 415-2805 Internet:  
OFFICE C9tacts          C/SPLB:DSSA    C/PECB:DRPM    D/DRPM
jetl@nrc.go


John Tappert. NRR (301) 415-1167 Internet:
l ME  Loughee        TMarsh          AChaffee      TMartin
jrt@nr gov Attachment:
1. List of Recently Issued NRC I ormation Notices Tech Editor re ewed 10/29 DOCUMENT NAME G:\JRT\LSALRHR.IN


OFFICE C9tacts C/SPLB:DSSA
JTatum


C/PECB:DRPM
DATE  10/30/96        11/ 4/96      11/  /96        11/  /96 Official Record Copy


D/DRPMl ME Loughee TMarsh AChaffee TMartin JTatum DATE 10/30/96 11/ 4/96 11/ /96 11/ /96 Official Record Copy.,}}
.,}}


{{Information notice-Nav}}
{{Information notice-Nav}}

Latest revision as of 04:39, 24 November 2019

Potential Common-Mode Post-Accident Failure of Residual Heat Removal Heat Exchangers
ML031050550
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, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant  Entergy icon.png
Issue date: 11/14/1996
From: Martin T
Office of Nuclear Reactor Regulation
To:
References
IN-96-060, NUDOCS 9611070081
Download: ML031050550 (7)
v • d • e


I

K>

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, DC 20555-0001 November 14, 1996 NRC INFORMATION NOTICE 96-60: POTENTIAL COMMON-MODE POST-ACCIDENT

FAILURE OF RESIDUAL HEAT REMOVAL HEAT

EXCHANGERS

Addressees

All holders of operating licenses or construction permits for nuclear power reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert

addressees to a potential common-mode post-accident failure of boiling water reactor

(BWR) residual heat removal (RHR) heat exchangers. It is expected that recipients will

review the information for applicability to their facilities and consider actions, as

appropriate, to avoid similar problems. However, suggestions contained in this information

notice are not NRC requirements; therefore, no specific action or written response is

required.

Background

The NRC staff issued Information Notice 96-45, 'Potential Common-Mode Post-Accident

Failure of Containment Coolers," on August 28, 1996, to alert licensees to a potential

failure mechanism of containment coolers during a design-basis loss-of-coolant accident

(LOCA) with a concurrent loss of offsite power or with a delayed sequencing of safety- related equipment. Specifically, if the containment coolers are exposed to forced

convection in a post-LOCA environment without cooling water flow, boiling may occur on

the stagnant cooling water side of the containment coolers. When cooling water flow is

subsequently reinitiated, the steam voids will collapse and may create significant

hydrodynamic loads (waterhammer). The waterhammer may threaten the integrity of the

containment cooler or the associated cooling water piping. Generic Letter 96-06,

"Assurance of Equipment Operability and Containment Integrity During Design-Basis

Accident Conditions," issued on September 30, 1996, also addressed this issue.

Description of Circumstances

A potential waterhammer scenario in the service water side of the RHR heat exchanger

was identified at the LaSalle Nuclear Station. The postulated phenomenon is analogous

to that identified for containment coolers in Information Notice 96-45 and Generic

Letter 96-06.

9611070081

96110460 7008 t04do aa{\

IN 96-60

November 14, 1996 At LaSalle, a BWR 5 plant, the top of the vertical RHR heat exchanger is the high point of

the RHR service water system and is at an elevation that is higher than that of the ultimate

heat sink by approximately 9 meters (30 feet) for normal lake levels. The resultant

pressure in the heat exchanger tubes in a standby condition is estimated to be between

7000 and 21,000 pascals (1 and 3 psia), with associated saturation temperatures between

430 and 600 C (1100 and 1400 F). Boiling will occur in these tubes if these temperatures

are exceeded. Under low lake levels, the licensee found that voiding would occur in the

top of the tubes regardless of temperature.

At LaSalle, the RHR system is lined up so that flow will go through both the RHR heat

exchanger and a bypass valve whenever the RHR system is initiated in its safety injection

(low pressure coolant injection) mode. The RHR service water flow to the tube side of the

RHR heat exchangers does not start automatically on a safety injection signal. Emergency

operating procedures direct that the RHR service water pumps be started manually within

the first 10 minutes of an accident.

It is postulated that during a LOCA, water from the suppression pool, which could start

from the technical specification allowable 41 0 C (1050 F), could quickly be heated to

88OC (1900 F). When the relatively hot suppression pool fluid would be pumped through

the RHR heat exchanger, it would boil the stagnant low pressure service water. When

RHR service water flow would subsequently be manually initiated, the steam voids would

collapse and might create significant hydrodynamic loads. The hydrodynamic loads might

impair the integrity of the heat exchangers or the associated service water piping. This

scenario does not occur during normal operation of the RHR system in the shutdown

cooling mode because the RHR service water system is started first to ensure that cooling

flow is established before h~ot fluid is introduced into the heat exchangers.

Both units at the LaSalle Nuclear Station are currently shut down. The licensee continues

to assess this issue and will ensure operability of the RHR heat exchangers before restart.

The licensee is considering the installation of a keep-fill system on the RHR service water

system to keep the heat exchangers pressurized.

Discussion

The RHR heat exchangers provide an important safety function for long term heat removal.

The postulated failure scenario could cause a common failure of the RHR heat exchangers, thereby potentially challenging this function. In addition, a structural failure of the RHR

heat exchangers could create a containment bypass release path and divert low pressure

coolant injection flow. An individual plant vulnerability to these postulated failures

depends on a number of factors. The physical configuration of the RHR service water

system and RHR heat exchanger, the operational alignment of the heat exchanger isolation

valves, the sequencing of the RHR service water pumps, and other site-specific parameters

have an effect on facility vulnerability to this potential failure mode.

IN 96-60

November 14, 1996 This information notice requires no specific action or written response. If you have any

questions about the information in this notice, please contact one of the technical contacts

listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

I Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: V. Patricia Lougheed, Region IlIl

(630) 829-9760

E-mail: vpl@nrc.gov

James Tatum, NRR

(301) 415-2805 E-mail: jetl @nrc.gov

John Tappert, NRR

(301) 415-1167 E-mail: jrt@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

/f 7A~4*a,, 9ikE

I,-ACED

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Attachment

IN 96-60

November 14, 1996 -

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

96-59 Potential Degradation of 10/30196 All holders of OLs or

Post Loss-of-Coolant CPs for nuclear power

Recirculation Capability reactors

as a Result of Debris

96-58 RCP Seal Replacement with 10/30/96 All holders of OLs or

Pump on Backseat CPs for pressurized-water

reactors

96-57 Incident-Reporting Require- 10/29/96 All U.S. Nuclear

ments Involving Intakes, Regulatory Commission

During a 24-Hour Period licensees

That May Cause a Total

Effective Dose Equivalent

in Excess of 0.05 Sv

(5 rems)

96-56 Problems Associated with 10/22/96 All holders of OLs or

Testing, Tuning, or Reset- CPs for nuclear power

ting of Digital Control reactors

Systems While at Power

OL = Operating License

CP = Construction Permit

N;

IN 96-60

November 14, 1996 This information notice requires no specific action or written response. If you have any

questions about the information in this notice, please contact one of the technical contacts

listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

original signed by D. B. Matthews

homas T. Martin, Director

/ Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: V. Patricia Lougheed, Region III

1630) 829-9760

E-mail: vpl@nrc.gov

James Tatum, NRR

(301) 415-2805 E-mail: jetl @nrc.gov

John Tappert, NRR

(301) 415-1167 E-mail: jrt@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

  • SEE PREVIOUS CONCURRENCE

Tech Editor reviewed 10/29 DOCUMENT NAME: 96-62.IN

OFFICE Contacts* C/SPLB:DSSA C/PECB:DRPM D/DR'I j

NAME PLougheed TMarsh AChaffee Ma

JTatum

JTappert _ _ _t -

DATE 10/30/96 11/04/96 11/06/96 11/1/96 Official Record Copy

K>

IN 96-xx

November xx. 1996 This information notice requires no specific action or written response. If

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one of the technical contacts listed below or the appropriate Office of /

Nuclear Reactor Regul ation (NRR) project manager.

Thomas T. Martin, Dire r

Division of Reactor rogram Management

Office of Nucle eactor Regulation

Technical Contacts: V. Patricia Lougheed. Re n III

(630) 829-9760

E-mailt: vpl@nrc. v

James Tatum. R

(301) 415g20

E-mail: jetl@nrc.gov

Jo zTap ert. NRR

301) 415-1167 E-mail: jrt@nrc.gov

Attachment:

1. List of Issued NRC Information Notices

  • SEE PREVIOUS CONCURRENCE

Tech Editor reviewed 10/29 ,24t nrij% I 4r

DOClUMFNT vvv

NAME: G:\JRT\LSALRHR.IN

- r. - _ . . . ..........

OFFICE Contacts* C/SPLB:DSSA* C/PECB:DRPM D/DRPM

NAME PLougheed TMarsh AChaffee Thartin

JTatum

____ __ Tappert _ _ _ _ _ _ _

DATE 10/30/96 11/04/96 11/L& /96 11/ /96 UTTIClal Kecr'u LUpy

nj

IN 96-xx

November xx. 1996 This information notice requires no specific action or written response. If

you have any questions about the information in this notice. please conta

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Thomas T. Martin, Dir dor

Division of Reactor rogram Management

Office of Nuclear eactor Regulation

Technical Contacts: V. Patricia Lougheed. Region i

(630) 829-9760

Internet: vpl@nrc.gov

James Tatum, NRR

(301) 415-2805 Internet: jetl@nrc.go

John Tappert. NRR

(301) 415-1167 Internet: jrt@nr gov

Attachment:

1. List of Recently Issued NRC I ormation Notices

Tech Editor re ewed 10/29 DOCUMENT NAME G:\JRT\LSALRHR.IN

OFFICE C9tacts C/SPLB:DSSA C/PECB:DRPM D/DRPM

l ME Loughee TMarsh AChaffee TMartin

JTatum

DATE 10/30/96 11/ 4/96 11/ /96 11/ /96 Official Record Copy

.,


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