Information Notice 1996-41, Effects of a Decrease in Feedwater Temperature on Nuclear Instrumentation: Difference between revisions

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{{#Wiki_filter:K) K)UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555-0001July 26, 1996NRC INFORMATION NOTICE 96-41: EFFECTS OF A DECREASE IN FEEDWATER TEMPERATUREON NUCLEAR INSTRUMENTATION
{{#Wiki_filter:K) K) UNITED STATES NUCLEAR REGULATORY
 
COMMISSION
 
===OFFICE OF NUCLEAR REACTOR REGULATION===
WASHINGTON, D.C. 20555-0001 July 26, 1996 NRC INFORMATION
 
NOTICE 96-41: EFFECTS OF A DECREASE IN FEEDWATER
 
TEMPERATURE
 
===ON NUCLEAR INSTRUMENTATION===


==Addressees==
==Addressees==
All holders of operating licenses or construction permits for pressurizedwater reactors (PWRs).
All holders of operating
 
licenses or construction
 
permits for pressurized
 
water reactors (PWRs).


==Purpose==
==Purpose==
The U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice to alert addressees to the potential for operation above licensed poweras a result of a decrease in feedwater temperature event affecting nuclearinstrumentation. It is expected that recipients will review the informationfor applicability to their facilities and consider actions, as appropriate, toavoid similar problems. However, suggestions contained in this informationnotice are not NRC requirements; therefore, no specific action or writtenresponse is required.
The U.S. Nuclear Regulatory
 
Commission (NRC) is issuing this information
 
notice to alert addressees
 
to the potential
 
for operation
 
above licensed power as a result of a decrease in feedwater
 
temperature
 
event affecting
 
nuclear instrumentation.
 
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.Description
 
of Circumstances
 
On February 14, 1996, the licensee for the Comanche Peak Steam Electric Station was operating
 
Unit 2 at 95 percent rated thermal power near end-of-core life when a significant
 
reduction
 
in feedwater
 
temperature
 
occurred because of the loss of feedwater
 
heaters. This reduction, in turn, caused a reduction
 
in the reactor coolant system cold-leg temperatures.
 
The colder reactor coolant temperature, with a large negative moderator
 
temperature
 
coefficient, caused reactor power to increase to approximately
 
102 percent according
 
to ex-core nuclear instrumentation.
 
The nitrogen-16 (N-16)detection
 
system reached the overpower
 
turbine runback setpoint (109 percent)and initiated
 
a turbine runback. The N-16 detection
 
system measures N-16 activity in the primary coolant as a measure of the total power generation.
 
This system is a substitute
 
for the resistance
 
temperature
 
detector over-temperature
 
and over-power
 
reactor trip functions
 
used at other Westinghouse
 
PWRs. The plant stabil zed at an indicated
 
power of approximately
 
97 percent according
 
to the ex-core nuclear instrumentation.
 
After approximately
 
90 minutes, a second similar turbine runback occurred while restoring
 
balance-of-plant
 
equipment.
 
Following
 
this runback, reactor power was stabilized
 
at approximately
 
100 percent according
 
to nuclear instrumentation.
 
During the next 30 minutes, the reactor was operated at approximately
 
100 percent power as indicated
 
by nuclear instrumentation, with reactor coolant temperatures
 
below normal. The licensee noted that the N-16 9 6 0 7 2 2 0l 6 0 ujo i 7 9,oi4 (R ~IE ctG
 
IN 96-41 July 26, 1996 detection
 
system indicated
 
approximately
 
106 percent power and the computer-based plant calorimetric
 
system indicated
 
approximately
 
102 percent power.Subsequently, the reactor power was reduced to less than 100 percent by all indications.
 
Discussion
 
There are three aspects of this event which have generic implications.
 
First, with a loss of secondary
 
plant efficiency, programmed
 
T e can no longer reliably represent
 
core thermal power. Second, the venturi-based
 
input into the computer-based
 
calorimetric
 
system may not be accurate with cold feedwater.
 
And third, the final safety analysis report had not analyzed this transient
 
accurately.
 
Following
 
the second runback, operators
 
noted that reactor power indicated<100 percent according
 
to nuclear instrumentation.
 
Although the operators knew that cold feedwater
 
could cause an increase in the amount of neutron attenuation, they believed that the nuclear instrumentation
 
indicated conservatively (i.e., higher than actual) because they were maintaining
 
TA"e approximately
 
1.7 eC [3 OF] above T Ref. The licensee could not use the computer-based
 
calorimetric
 
until some time after the second turbine runback due to maintenance
 
activities.
 
Te , based on the main turbine impulse pressure, is programmed
 
as a functlon of turbine load and, for normal efficiency, is a good representation
 
of thermal power. When the unit lost the feedwater
 
heaters, the plant efficiency
 
decreased.
 
Because the main turbine electro-hydraulic
 
control system maintained
 
generator
 
output, core thermal power increased
 
to account for the loss of efficiency, and thus, TRef no longer accurately
 
represented
 
the core thermal power.The cold-leg temperature
 
is a more appropriate
 
indicator
 
of the accuracy of the nuclear instrumentation
 
than programmed
 
TY.e. As the cold-leg temperature
 
decreased, the amount of neutron attenuation
 
in the downcomer
 
area surrounding
 
the core increased
 
and hence affected the amount of neutrons reaching the detectors.
 
The licensee analysis showed that for every 0.6 C (1 OF] of cold-leg temperature
 
change, the nuclear instrumentation
 
was affected by 0.6 to 0.8 percent power. A review of the second transient
 
showed that the cold-leg temperature
 
was approximately
 
2.5 &deg;C [4.5 OF] lower than when the detectors were last calibrated.
 
This corresponded
 
to a 3 to 4 percent error, which corresponded
 
to the difference
 
in the actual versus the indicated
 
power (104 percent actual versus 100 percent indicated).
 
During the review, the licensee noted that the computer-based
 
calorimetric
 
was 4 percent lower than the actual thermal power (N-16 power monitor).
 
The calorimetric
 
was based on feedwater
 
flow measured by venturis.
 
Although the calorimetric
 
calculation
 
used feedwater
 
temperature
 
as an input, temperatures
 
significantly
 
different
 
than the normal 227 OC [440 OF] introduced
 
errors into the calculation.
 
Finally, the actual events involved temperature
 
and power levels that exceeded those in the analysis of the Decrease in Feedwater
 
Temperature" event presented
 
in Chapter 15 of the licensee final safety analysis report. In that
 
IN 96-41 July 26, 1996 analysis, the inadvertent
 
opening of the low-pressure
 
heater bypass valve, coupled with the trip of the heater drain pumps, resulted in a feedwater temperature
 
drop of less than 19 'C (35 OF], and a corresponding
 
power increase of less than 10 percent. In the actual event, the feedwater temperature
 
dropped by approximately
 
111 &deg;C (200 OF], and the licensee calculated
 
that reactor power would have increased
 
by approximately
 
35 percent without operator or protective
 
actions. The licensee determined
 
that although the initiating
 
events were the same, the Chapter 15 analysis did not account for the loss of extraction
 
steam to the high-pressure
 
heaters, which was the cause of the temperature
 
difference.
 
During the event, a level imbalance occurred between the two heater drain tanks, which resulted in the isolation of extraction
 
steam.The NRC staff review of analyses of feedwater
 
temperature
 
events at similar facilities
 
revealed that most of these analyses assumed similar initiating
 
events as the Comanche Peak analysis and had similar conclusions
 
concerning
 
the amount of feedwater
 
temperature
 
drop. The licensee has reanalyzed
 
the event to include a 119 OC [246 OF] feedwater
 
temperature
 
drop and concluded that all accident analysis parameters
 
remained within requirements.
 
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
 
project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
contacts:
Harry A. Freeman, RIV (817) 897-1500 E-mail: haf~nrc.gov
 
Chu-Yu Liang, NRR (301) 415-2878 E-mail: cylenrc.gov
 
Attachment:
List Of Recently Issued HRC Information
 
Notices A1h4 Stir A Je6tQ
 
K> KJ Attachment
 
IN 96-41 July 26, 1996 LIST OF RECENTLY ISSUED NRC INFORMATION
 
NOTICES Information
 
Date of Notice No. Subject Issuance Issued to 96-40 96-09, Supp. 1 96-39 96-38 Deficiencies
 
in Material Dedication
 
and Procure-ment Practices
 
and in Audits of Vendors Damage in Foreign Steam Generator
 
Internals Estimates
 
of Decay Heat Using ANS 5.1 Decay Heat Standard May Vary Signi-ficantly Results of Steam Generator Tube Examinations
 
Inaccurate
 
Reactor Water Level Indication
 
and Inad-vertent Draindown
 
During Shutdown Degradation
 
of Cooling Water Systems Due to Icing Failure of Safety Systems on Self-Shielded
 
Irradia-tors Because of Inadequate
 
Maintenance
 
and Training Hydrogen Gas Ignition during Closure Welding of a VSC-24 Multi-Assembly
 
Sealed Basket 07/25/96 07/10/96 07/05/96 06/21/96 06/18/96 06/12/96 06/11/96 05/31/96 All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for pressurized-water
 
reactors All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for pressurized
 
water reactors All pressurized
 
water reactor facilities
 
holding an operating
 
license or a construction
 
permit All holders of OLs or CPs for nuclear power reactors All U.S. Nuclear Regulatory
 
Commission
 
irradiator
 
licensees
 
and vendors All holders of OLs or CPs for nuclear power reactors 96-37 96-36 96-35 96-34 OL -Operating
 
License CP -Construction
 
Permit
 
*~ -K> K IN 96-41 July 26, 1996 analysis, the inadvertent
 
opening of the low-pressure
 
heater bypass valve, coupled with the trip of the heater drain pumps, resulted in a feedwater temperature
 
drop of less than 19 *C [35 OF], and a corresponding
 
power increase of less than 10 percent. In the actual event, the feedwater temperature
 
dropped by approximately
 
111 *C [200 OF], and the licensee calculated
 
that reactor power would have increased
 
by approximately
 
35 percent without operator or protective
 
actions. The licensee determined
 
that although the initiating
 
events were the same, the Chapter 15 analysis did not account for the loss of extraction
 
steam to the high-pressure
 
heaters, which was the cause of the temperature
 
difference.
 
During the event, a level imbalance occurred between the two heater drain tanks, which resulted in the isolation of extraction
 
steam.The NRC staff review of analyses of feedwater
 
temperature
 
events at similar facilities
 
revealed that most of these analyses assumed similar initiating
 
events as the Comanche Peak analysis and had similar conclusions
 
concerning
 
the amount of feedwater
 
temperature
 
drop. The licensee has reanalyzed
 
the event to include a 119 *C [246 OF] feedwater
 
temperature
 
drop and concluded that all accident analysis parameters
 
remained within requirements.
 
This information
 
notice requires no specific action or written response.


==Description of Circumstances==
If you have any questions
On February 14, 1996, the licensee for the Comanche Peak Steam ElectricStation was operating Unit 2 at 95 percent rated thermal power near end-of-core life when a significant reduction in feedwater temperature occurredbecause of the loss of feedwater heaters. This reduction, in turn, caused areduction in the reactor coolant system cold-leg temperatures. The colderreactor coolant temperature, with a large negative moderator temperaturecoefficient, caused reactor power to increase to approximately 102 percentaccording to ex-core nuclear instrumentation. The nitrogen-16 (N-16)detection system reached the overpower turbine runback setpoint (109 percent)and initiated a turbine runback. The N-16 detection system measures N-16activity in the primary coolant as a measure of the total power generation.This system is a substitute for the resistance temperature detector over-temperature and over-power reactor trip functions used at other WestinghousePWRs. The plant stabil zed at an indicated power of approximately 97 percentaccording to the ex-core nuclear instrumentation.After approximately 90 minutes, a second similar turbine runback occurredwhile restoring balance-of-plant equipment. Following this runback, reactorpower was stabilized at approximately 100 percent according to nuclearinstrumentation. During the next 30 minutes, the reactor was operated atapproximately 100 percent power as indicated by nuclear instrumentation, withreactor coolant temperatures below normal. The licensee noted that the N-169607220l60ujo i 7 9,oi4(R ~IE ctG


IN 96-41July 26, 1996 detection system indicated approximately 106 percent power and the computer-based plant calorimetric system indicated approximately 102 percent power.Subsequently, the reactor power was reduced to less than 100 percent by allindications.DiscussionThere are three aspects of this event which have generic implications. First,with a loss of secondary plant efficiency, programmed T e can no longerreliably represent core thermal power. Second, the venturi-based input intothe computer-based calorimetric system may not be accurate with coldfeedwater. And third, the final safety analysis report had not analyzed thistransient accurately.Following the second runback, operators noted that reactor power indicated<100 percent according to nuclear instrumentation. Although the operatorsknew that cold feedwater could cause an increase in the amount of neutronattenuation, they believed that the nuclear instrumentation indicatedconservatively (i.e., higher than actual) because they were maintaining TA"eapproximately 1.7 eC [3 OF] above TRef. The licensee could not use thecomputer-based calorimetric until some time after the second turbine runbackdue to maintenance activities. Te , based on the main turbine impulsepressure, is programmed as a functlon of turbine load and, for normalefficiency, is a good representation of thermal power. When the unit lost thefeedwater heaters, the plant efficiency decreased. Because the main turbineelectro-hydraulic control system maintained generator output, core thermalpower increased to account for the loss of efficiency, and thus, TRef nolonger accurately represented the core thermal power.The cold-leg temperature is a more appropriate indicator of the accuracy ofthe nuclear instrumentation than programmed TY.e. As the cold-leg temperaturedecreased, the amount of neutron attenuation in the downcomer area surroundingthe core increased and hence affected the amount of neutrons reaching thedetectors. The licensee analysis showed that for every 0.6 C (1 OF] of cold-leg temperature change, the nuclear instrumentation was affected by 0.6 to 0.8percent power. A review of the second transient showed that the cold-legtemperature was approximately 2.5 &deg;C [4.5 OF] lower than when the detectorswere last calibrated. This corresponded to a 3 to 4 percent error, whichcorresponded to the difference in the actual versus the indicated power (104percent actual versus 100 percent indicated).During the review, the licensee noted that the computer-based calorimetric was4 percent lower than the actual thermal power (N-16 power monitor). Thecalorimetric was based on feedwater flow measured by venturis. Although thecalorimetric calculation used feedwater temperature as an input, temperaturessignificantly different than the normal 227 OC [440 OF] introduced errors intothe calculation.Finally, the actual events involved temperature and power levels that exceededthose in the analysis of the Decrease in Feedwater Temperature" eventpresented in Chapter 15 of the licensee final safety analysis report. In that
about the information


IN 96-41July 26, 1996 analysis, the inadvertent opening of the low-pressure heater bypass valve,coupled with the trip of the heater drain pumps, resulted in a feedwatertemperature drop of less than 19 'C (35 OF], and a corresponding powerincrease of less than 10 percent. In the actual event, the feedwatertemperature dropped by approximately 111 &deg;C (200 OF], and the licenseecalculated that reactor power would have increased by approximately 35 percentwithout operator or protective actions. The licensee determined that althoughthe initiating events were the same, the Chapter 15 analysis did not accountfor the loss of extraction steam to the high-pressure heaters, which was thecause of the temperature difference. During the event, a level imbalanceoccurred between the two heater drain tanks, which resulted in the isolationof extraction steam.The NRC staff review of analyses of feedwater temperature events at similarfacilities revealed that most of these analyses assumed similar initiatingevents as the Comanche Peak analysis and had similar conclusions concerningthe amount of feedwater temperature drop. The licensee has reanalyzed theevent to include a 119 OC [246 OF] feedwater temperature drop and concludedthat all accident analysis parameters remained within requirements.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation project manager.Brian K. Grimes, Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: Harry A. Freeman, RIV(817) 897-1500E-mail: haf~nrc.govChu-Yu Liang, NRR(301) 415-2878E-mail: cylenrc.govAttachment: List Of Recently Issued HRC Information NoticesA1h4 Stir A Je6tQ
in this notice,-please


K> KJAttachmentIN 96-41July 26, 1996 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to96-4096-09,Supp. 196-3996-38Deficiencies in MaterialDedication and Procure-ment Practices and inAudits of VendorsDamage in Foreign SteamGenerator InternalsEstimates of Decay HeatUsing ANS 5.1 Decay HeatStandard May Vary Signi-ficantlyResults of Steam GeneratorTube ExaminationsInaccurate Reactor WaterLevel Indication and Inad-vertent Draindown DuringShutdownDegradation of CoolingWater Systems Due to IcingFailure of Safety Systemson Self-Shielded Irradia-tors Because of InadequateMaintenance and TrainingHydrogen Gas Ignitionduring Closure Weldingof a VSC-24 Multi-AssemblySealed Basket07/25/9607/10/9607/05/9606/21/9606/18/9606/12/9606/11/9605/31/96All holders of OLs or CPsfor nuclear power reactorsAll holders of OLs or CPsfor pressurized-waterreactorsAll holders of OLs or CPsfor nuclear power reactorsAll holders of OLs or CPsfor pressurized waterreactorsAll pressurized waterreactor facilities holdingan operating license or aconstruction permitAll holders of OLs or CPsfor nuclear power reactorsAll U.S. Nuclear RegulatoryCommission irradiatorlicensees and vendorsAll holders of OLs or CPsfor nuclear power reactors96-3796-3696-3596-34OL -Operating LicenseCP -Construction Permit
contact one of the technical


*~ -K> KIN 96-41July 26, 1996 analysis, the inadvertent opening of the low-pressure heater bypass valve,coupled with the trip of the heater drain pumps, resulted in a feedwatertemperature drop of less than 19 *C [35 OF], and a corresponding powerincrease of less than 10 percent. In the actual event, the feedwatertemperature dropped by approximately 111 *C [200 OF], and the licenseecalculated that reactor power would have increased by approximately 35 percentwithout operator or protective actions. The licensee determined that althoughthe initiating events were the same, the Chapter 15 analysis did not accountfor the loss of extraction steam to the high-pressure heaters, which was thecause of the temperature difference. During the event, a level imbalanceoccurred between the two heater drain tanks, which resulted in the isolationof extraction steam.The NRC staff review of analyses of feedwater temperature events at similarfacilities revealed that most of these analyses assumed similar initiatingevents as the Comanche Peak analysis and had similar conclusions concerningthe amount of feedwater temperature drop. The licensee has reanalyzed theevent to include a 119 *C [246 OF] feedwater temperature drop and concludedthat all accident analysis parameters remained within requirements.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice,-please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation project manager.Original signed by Brian K. GrimesBrian K. Grimes, Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: Harry A. Freeman, RIV(817) 897-1500E-mail: haf@nrc.govChu-Yu Liang, NRR(301) 415-2878E-mail: cyl~nrc.govAttachment: List of Recently Issued NRC Information NoticesDOCUMENT NAME: G:\SSK2\INFONOT.C PTo receive a copy of this docunent, tndicate in the box CO~opy So attachment/enclosure EsCopy with attachment/enctosure N
contacts listed below or the appropriate


* NocopsOFFICE C BC:SRXB I BC:LPECB lI (A) DW M iNAME CYLiang* RJones* AChaffee*HAFreeman* ____ _DATE 16/ 3/96 16/21/96 17/08/96 17LI/96 IOFFILIAL MLLUM LWUF* See previous concurrence Tech Editor reviewed & concurred on 05/28/96
Office of Nuclear Reactor Regulation
~1~1 -,K)IN 96-XXJuly XX, 1996 *See previous concurrence


IN 96-XXJuly XX, 1996 for the loss of extraction steam to the high-pressure heaters, which was thecause of the temperature difference. During the event, a level imbalanceoccurred between the two heater drain tanks, which resulted in the isolationof extraction steam.The NRC staff review of analyses of feedwater temperature events at similarfacilities revealed that most of these analyses assumed similar initiatingevents as the licensee analysis and had similar conclusions concerning theamount of feedwater temperature drop. The licensee has reanalyzed the eventpursuant to Section 50.59 of Title 10 of the Code of Federal Regulations toinclude a 119 'c [246 OF] feedwater temperature drop and concluded that allaccident analysis parameters remained within requirements.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation project manager.Brian K. Grimes, Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: Harry A. Freeman, RIV(817) 897-1500E-mail: haftnrc.govChu-Yu Liang, NRR(301) 415-2878E-mail: cyl~nrc.govAttachment: List of Recently Issued NRC Information NoticesDOCUMENT NAME: G:\SSK2\INFONOT.C PTo receive a copy of this document, indicate in the box C-Topy u/o attachment/enclosure E=Copy with attachment/enclosure N NocopyOFFICE CONT:i kd l BC:SRXBLl BC:iPECB lI (A)iD:iDRPM I _NAME CYLiang* RJones* AChaffee* BGrimesl _ HAFreeman*DATE 6/ 3/96 6/21/96 7/08/96 7/ /96* See previous concurrenceOFFICIAL KLLUKV UV X!
project manager.Original signed by Brian K. Grimes Brian K. Grimes, Acting Director Division of Reactor Program Management
IN 96-XXJuly XX, 1996 for the loss of extraction steam to the high-pressure heaters, which was thecause of the temperature difference. During the event, a level imbalanceoccurred between the two heater drain tanks, which resulted in the isolationof extraction steam.The NRC staff review of analyses of feedwater temperature events at similarfacilities revealed that most of these analyses assumed similar initiatingevents as the licensee analysis and had similar conclusions concerning theamount of feedwater temperature drop. The licensee has reanalyzed the eventpursuant to Section 50.59 of Title 10 of the Code of Federal Regulations toinclude a 119 *C [246 *F] feedwater temperature drop and concluded that allaccident analysis parameters remained within requirements.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation project manager.Brian K. Grimes, Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: Harry A. Freeman, RIV(817) 897-1500Internet:haf@nrc.govChu-Yu Liang, NRR(301) 415-2878Internet:cyl nrc.govAttachment: List of Recently Issued NRC Information NoticesDOCUMENT NAME: G:\SSK2\INFONOT.C PTo receive a copy of this document, Indicate in the box Conopy w/c attachment/enclosure EnCopy with attachment/enclosure N


* NoOFFICE CONT: Ekd BC: SLB BC:PECB (A)D:DRPMNAME CYLiang* RJones* ACh)f BGrimesl ~~HAFreeman*tVtDATE 6/ 3/96 6/21/96 7/7/96 7/ /96OFFICIAL RECOR COPY* See previous concurrence
===Office of Nuclear Reactor Regulation===
Technical


K-, /IN 96-XXJune XX, 1996 Ioith attachment/enclosure 1
contacts:
Harry A. Freeman, RIV (817) 897-1500 E-mail: haf@nrc.gov
 
Chu-Yu Liang, NRR (301) 415-2878 E-mail: cyl~nrc.gov
 
Attachment:
List of Recently Issued NRC Information
 
Notices DOCUMENT NAME: G:\SSK2\INFONOT.C
 
P To receive a copy of this docunent, tndicate in the box CO~opy So attachment/enclosure
 
EsCopy with attachment/enctosure
 
N
 
* No cops OFFICE C BC:SRXB I BC:LPECB lI (A) DW M i NAME CYLiang* RJones* AChaffee*HAFreeman*
____ _DATE 16/ 3/96 16/21/96 17/08/96 17LI/96 I OFFILIAL MLLUM LWUF* See previous concurrence
 
Tech Editor reviewed & concurred
 
on 05/28/96
~1~1 -,K)IN 96-XX July XX, 1996 for the loss of extraction
 
steam to ti cause of the temperature
 
difference.
 
occurred between the two heater drain of extraction
 
steam.he high-pressure
 
heaters, which was the During the event, a level imbalance tanks, which resulted in the isolation The NRC staff review of analyses of feedwater
 
temperature
 
events at similar facilities
 
revealed that most of these analyses assumed similar initiating
 
events as the Comanche Peak analysis and had similar conclusions
 
concerning
 
the amount of feedwater
 
temperature
 
drop. The licensee has reanalyzed
 
the event to include a 119 'C [246 'F] feedwater
 
temperature
 
drop and concluded that all accident analysis parameters
 
remained within requirements.
 
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
 
project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
contacts: Harry A. Freeman, RIV (817) 897-1500 E-mail: haf~nrc.gov
 
Chu-Yu Liang, NRR (301) 415-2878 E-mail: cyl~nrc.gov
 
Attachment:
List of Recently Issued NRC Information
 
Notices DOCUMENT NAME: G:\SSK2\INFONOT.C
 
P To receive a copy of this document, indicate in the box CzAopy w/o attachment/enclosure
 
E-Copy with attachment/enclosure
 
N
 
* No OFFICE l kd BC: SRXB BC:PECB )D:DR NAME CYLiang* RJones* AChaffee*
BGrimes HAFreeman*
DATE 6/ 3/96 6/21/96 7/08/96 7/ /96 OFFICIAL RECORD COPY*See previous concurrence
 
IN 96-XX July XX, 1996 for the loss of extraction
 
steam to the high-pressure
 
heaters, which was the cause of the temperature
 
difference.
 
During the event, a level imbalance occurred between the two heater drain tanks, which resulted in the isolation of extraction
 
steam.The NRC staff review of analyses of feedwater
 
temperature
 
events at similar facilities
 
revealed that most of these analyses assumed similar initiating
 
events as the licensee analysis and had similar conclusions
 
concerning
 
the amount of feedwater
 
temperature
 
drop. The licensee has reanalyzed
 
the event pursuant to Section 50.59 of Title 10 of the Code of Federal Regulations
 
to include a 119 'c [246 OF] feedwater
 
temperature
 
drop and concluded
 
that all accident analysis parameters
 
remained within requirements.
 
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
 
project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
contacts:
Harry A. Freeman, RIV (817) 897-1500 E-mail: haftnrc.gov
 
Chu-Yu Liang, NRR (301) 415-2878 E-mail: cyl~nrc.gov
 
Attachment:
List of Recently Issued NRC Information
 
Notices DOCUMENT NAME: G:\SSK2\INFONOT.C
 
P To receive a copy of this document, indicate in the box C-Topy u/o attachment/enclosure
 
E=Copy with attachment/enclosure
 
N No copy OFFICE CONT:i kd l BC:SRXBLl
 
BC:iPECB lI (A)iD:iDRPM
 
I _NAME CYLiang* RJones* AChaffee*
BGrimes l _ HAFreeman*
DATE 6/ 3/96 6/21/96 7/08/96 7/ /96* See previous concurrence
 
OFFICIAL KLLUKV UV X!
IN 96-XX July XX, 1996 for the loss of extraction
 
steam to the high-pressure
 
heaters, which was the cause of the temperature
 
difference.
 
During the event, a level imbalance occurred between the two heater drain tanks, which resulted in the isolation of extraction
 
steam.The NRC staff review of analyses of feedwater
 
temperature
 
events at similar facilities
 
revealed that most of these analyses assumed similar initiating
 
events as the licensee analysis and had similar conclusions
 
concerning
 
the amount of feedwater
 
temperature
 
drop. The licensee has reanalyzed
 
the event pursuant to Section 50.59 of Title 10 of the Code of Federal Regulations
 
to include a 119 *C [246 *F] feedwater
 
temperature
 
drop and concluded
 
that all accident analysis parameters
 
remained within requirements.
 
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
 
project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
contacts:
Harry A. Freeman, RIV (817) 897-1500 Internet:haf@nrc.gov
 
Chu-Yu Liang, NRR (301) 415-2878 Internet:cyl
 
nrc.gov Attachment:
List of Recently Issued NRC Information
 
Notices DOCUMENT NAME: G:\SSK2\INFONOT.C
 
P To receive a copy of this document, Indicate in the box Conopy w/c attachment/enclosure
 
EnCopy with attachment/enclosure
 
N
 
* No OFFICE CONT: Ekd BC: SLB BC:PECB (A)D:DRPM NAME CYLiang* RJones* ACh)f BGrimes l ~~HAFreeman*tVt
 
DATE 6/ 3/96 6/21/96 7/7/96 7/ /96 OFFICIAL RECOR COPY* See previous concurrence
 
K-, /IN 96-XX June XX, 1996 for the loss of extraction
 
steam to ti cause of the temperature
 
difference.
 
occurred between the two heater drain of extraction
 
steam.he high-pressure
 
heaters, which was the During the event, a level imbalance tanks, which resulted in the isolation The NRC staff's review of analyses of feedwater
 
temperature
 
events at similar facilities
 
revealed that most of these analyses assumed similar initiating
 
events as the licensee's
 
analysis and had similar conclusions
 
concerning
 
the amount of feedwater
 
temperature
 
drop. The licensee has reanalyzed
 
the event pursuant to Section 50.59 of Title 10 of the Code of Federal Regulations
 
to include a 119 'C [246 OF] feedwater
 
temperature
 
drop and concluded
 
that all accident analysis parameters
 
remained within requirements.
 
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
 
project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
contacts: Harry A. Freeman, RIV (817) 897-1500 Internet:haffnrc.gov
 
Chu-Yu Liang, NRR (301) 415-2878 Internet:cyl@nrc.gov
 
Attachment:
List of Recently Issued NRC Information
 
Notices DOCUMENT NAME: G:\SSK2\INFONOT.CP
 
To receive a copy of this document, indicate in the box Ciropy w/dattachmeft1/enctosure
 
EnC OFFICE CONT:jkd _l BC: SRXB E C:PECB I _ A)D:DRPM I NAME CYLiang* RJones AChaffee BGrimes HAFreeman*
I- _DATE 6/ 3/96 6/2j /96 6/ /96 6/ /96 OFFICIAL RECORD COPY I oith attachment/enclosure
 
1
* No copy* See previous concurrence
* No copy* See previous concurrence


IN 96-XXJune XX, 1996 detection system. The licensee believed that this system would probably notbe significantly affected by feedwater temperatures because of a differentmass flow rate determination method.Finally, the licensee's final safety analysis report did not accuratelyanalyze this transient. The actual events were similar to the analysis of the'Decrease in Feedwater Temperature event presented in Chapter 15. In thatanalysis, the inadvertent opening of the low-pressure heater bypass valve,coupled with the trip of the heater drain pumps, resulted in a feedwatertemperature drop of less than 35 OF, and a corresponding power increase ofless than 10 percent. In the actual event, the feedwater temperature droppedby approximately 200 OF, and the licensee calculated that reactor power wouldhave increased by approximately 35 percent without operator or protectiveactions. The licensee determined that although the initiating events were thesame, the Chapter 15 analysis did not account for the loss of extraction steamto the high-pressure heaters, which was the cause of the temperaturedifference. During the event, a level imbalance occurred between the twoheater drain tanks, which resulted in the isolation of extraction steam.The NRC staff's review of analyses of feedwater temperature events at similarfacilities revealed that most of these analyses assumed similar initiatingevents as the licensee's analysis and had similar conclusions concerning theamount of feedwater temperature drop.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation project manager.Brian K. Grimes, Acting DirectorDivision of Reactor Program ManagementOffice of Nuclear Reactor RegulationTechnical contacts: Harry A. Freeman, RIV(817) 897-1500Internet:haf@nrc.govChu-Yu Liang, NRR(301) 415-2878Internet:cyl nrc.govAttachment: List of Recently Issued NRC Information NoticesDOCUMENT NAME: G:\SSK2\INFONOT.C PTo receive a copy of this docunent, indicate in the box Catopy w/o attachment/enclosure E-C with attachment/enclosure N
IN 96-XX June XX, 1996 detection
 
system. The licensee believed that this system would probably not be significantly
 
affected by feedwater
 
temperatures
 
because of a different mass flow rate determination
 
method.Finally, the licensee's
 
final safety analysis report did not accurately
 
analyze this transient.
 
The actual events were similar to the analysis of the'Decrease
 
in Feedwater
 
Temperature
 
event presented
 
in Chapter 15. In that analysis, the inadvertent
 
opening of the low-pressure
 
heater bypass valve, coupled with the trip of the heater drain pumps, resulted in a feedwater temperature
 
drop of less than 35 OF, and a corresponding
 
power increase of less than 10 percent. In the actual event, the feedwater
 
temperature
 
dropped by approximately
 
200 OF, and the licensee calculated
 
that reactor power would have increased
 
by approximately
 
35 percent without operator or protective
 
actions. The licensee determined
 
that although the initiating
 
events were the same, the Chapter 15 analysis did not account for the loss of extraction
 
steam to the high-pressure
 
heaters, which was the cause of the temperature
 
difference.
 
During the event, a level imbalance
 
occurred between the two heater drain tanks, which resulted in the isolation
 
of extraction
 
steam.The NRC staff's review of analyses of feedwater
 
temperature
 
events at similar facilities
 
revealed that most of these analyses assumed similar initiating
 
events as the licensee's
 
analysis and had similar conclusions
 
concerning
 
the amount of feedwater
 
temperature
 
drop.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
 
project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management
 
===Office of Nuclear Reactor Regulation===
Technical
 
contacts:  
Harry A. Freeman, RIV (817) 897-1500 Internet:haf@nrc.gov
 
Chu-Yu Liang, NRR (301) 415-2878 Internet:cyl
 
nrc.gov Attachment:  
List of Recently Issued NRC Information
 
Notices DOCUMENT NAME: G:\SSK2\INFONOT.C
 
P To receive a copy of this docunent, indicate in the box Catopy w/o attachment/enclosure
 
E-C with attachment/enclosure


* No copyOFFICE lCONT:kd l BC:SRXB l BC:PECB l (A)D:DRPMNAME CYLiang 9 RJones AChaffee BGrimesHAFreema r _ _DATE /96 /96 6/ /96 6/ /96OFFICIAL RECORD COPY
N


}}
* No copy OFFICE lCONT:kd l BC:SRXB l BC:PECB l (A)D:DRPM NAME CYLiang 9 RJones AChaffee BGrimes HAFreema r _ _DATE /96 /96 6/ /96 6/ /96 OFFICIAL RECORD COPY}}


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

Revision as of 14:07, 31 August 2018

Effects of a Decrease in Feedwater Temperature on Nuclear Instrumentation
ML031060009
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: 07/26/1996
From: Grimes B K
Office of Nuclear Reactor Regulation
To:
References
IN-96-041, NUDOCS 9607220160
Download: ML031060009 (10)
v • d • e


K) K) UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 July 26, 1996 NRC INFORMATION

NOTICE 96-41: EFFECTS OF A DECREASE IN FEEDWATER

TEMPERATURE

ON NUCLEAR INSTRUMENTATION

Addressees

All holders of operating

licenses or construction

permits for pressurized

water reactors (PWRs).

Purpose

The U.S. Nuclear Regulatory

Commission (NRC) is issuing this information

notice to alert addressees

to the potential

for operation

above licensed power as a result of a decrease in feedwater

temperature

event affecting

nuclear instrumentation.

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.Description

of Circumstances

On February 14, 1996, the licensee for the Comanche Peak Steam Electric Station was operating

Unit 2 at 95 percent rated thermal power near end-of-core life when a significant

reduction

in feedwater

temperature

occurred because of the loss of feedwater

heaters. This reduction, in turn, caused a reduction

in the reactor coolant system cold-leg temperatures.

The colder reactor coolant temperature, with a large negative moderator

temperature

coefficient, caused reactor power to increase to approximately

102 percent according

to ex-core nuclear instrumentation.

The nitrogen-16 (N-16)detection

system reached the overpower

turbine runback setpoint (109 percent)and initiated

a turbine runback. The N-16 detection

system measures N-16 activity in the primary coolant as a measure of the total power generation.

This system is a substitute

for the resistance

temperature

detector over-temperature

and over-power

reactor trip functions

used at other Westinghouse

PWRs. The plant stabil zed at an indicated

power of approximately

97 percent according

to the ex-core nuclear instrumentation.

After approximately

90 minutes, a second similar turbine runback occurred while restoring

balance-of-plant

equipment.

Following

this runback, reactor power was stabilized

at approximately

100 percent according

to nuclear instrumentation.

During the next 30 minutes, the reactor was operated at approximately

100 percent power as indicated

by nuclear instrumentation, with reactor coolant temperatures

below normal. The licensee noted that the N-16 9 6 0 7 2 2 0l 6 0 ujo i 7 9,oi4 (R ~IE ctG

IN 96-41 July 26, 1996 detection

system indicated

approximately

106 percent power and the computer-based plant calorimetric

system indicated

approximately

102 percent power.Subsequently, the reactor power was reduced to less than 100 percent by all indications.

Discussion

There are three aspects of this event which have generic implications.

First, with a loss of secondary

plant efficiency, programmed

T e can no longer reliably represent

core thermal power. Second, the venturi-based

input into the computer-based

calorimetric

system may not be accurate with cold feedwater.

And third, the final safety analysis report had not analyzed this transient

accurately.

Following

the second runback, operators

noted that reactor power indicated<100 percent according

to nuclear instrumentation.

Although the operators knew that cold feedwater

could cause an increase in the amount of neutron attenuation, they believed that the nuclear instrumentation

indicated conservatively (i.e., higher than actual) because they were maintaining

TA"e approximately

1.7 eC [3 OF] above T Ref. The licensee could not use the computer-based

calorimetric

until some time after the second turbine runback due to maintenance

activities.

Te , based on the main turbine impulse pressure, is programmed

as a functlon of turbine load and, for normal efficiency, is a good representation

of thermal power. When the unit lost the feedwater

heaters, the plant efficiency

decreased.

Because the main turbine electro-hydraulic

control system maintained

generator

output, core thermal power increased

to account for the loss of efficiency, and thus, TRef no longer accurately

represented

the core thermal power.The cold-leg temperature

is a more appropriate

indicator

of the accuracy of the nuclear instrumentation

than programmed

TY.e. As the cold-leg temperature

decreased, the amount of neutron attenuation

in the downcomer

area surrounding

the core increased

and hence affected the amount of neutrons reaching the detectors.

The licensee analysis showed that for every 0.6 C (1 OF] of cold-leg temperature

change, the nuclear instrumentation

was affected by 0.6 to 0.8 percent power. A review of the second transient

showed that the cold-leg temperature

was approximately

2.5 °C [4.5 OF] lower than when the detectors were last calibrated.

This corresponded

to a 3 to 4 percent error, which corresponded

to the difference

in the actual versus the indicated

power (104 percent actual versus 100 percent indicated).

During the review, the licensee noted that the computer-based

calorimetric

was 4 percent lower than the actual thermal power (N-16 power monitor).

The calorimetric

was based on feedwater

flow measured by venturis.

Although the calorimetric

calculation

used feedwater

temperature

as an input, temperatures

significantly

different

than the normal 227 OC [440 OF] introduced

errors into the calculation.

Finally, the actual events involved temperature

and power levels that exceeded those in the analysis of the Decrease in Feedwater

Temperature" event presented

in Chapter 15 of the licensee final safety analysis report. In that

IN 96-41 July 26, 1996 analysis, the inadvertent

opening of the low-pressure

heater bypass valve, coupled with the trip of the heater drain pumps, resulted in a feedwater temperature

drop of less than 19 'C (35 OF], and a corresponding

power increase of less than 10 percent. In the actual event, the feedwater temperature

dropped by approximately

111 °C (200 OF], and the licensee calculated

that reactor power would have increased

by approximately

35 percent without operator or protective

actions. The licensee determined

that although the initiating

events were the same, the Chapter 15 analysis did not account for the loss of extraction

steam to the high-pressure

heaters, which was the cause of the temperature

difference.

During the event, a level imbalance occurred between the two heater drain tanks, which resulted in the isolation of extraction

steam.The NRC staff review of analyses of feedwater

temperature

events at similar facilities

revealed that most of these analyses assumed similar initiating

events as the Comanche Peak analysis and had similar conclusions

concerning

the amount of feedwater

temperature

drop. The licensee has reanalyzed

the event to include a 119 OC [246 OF] feedwater

temperature

drop and concluded that all accident analysis parameters

remained within requirements.

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

project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

contacts:

Harry A. Freeman, RIV (817) 897-1500 E-mail: haf~nrc.gov

Chu-Yu Liang, NRR (301) 415-2878 E-mail: cylenrc.gov

Attachment:

List Of Recently Issued HRC Information

Notices A1h4 Stir A Je6tQ

K> KJ Attachment

IN 96-41 July 26, 1996 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Date of Notice No. Subject Issuance Issued to 96-40 96-09, Supp. 1 96-39 96-38 Deficiencies

in Material Dedication

and Procure-ment Practices

and in Audits of Vendors Damage in Foreign Steam Generator

Internals Estimates

of Decay Heat Using ANS 5.1 Decay Heat Standard May Vary Signi-ficantly Results of Steam Generator Tube Examinations

Inaccurate

Reactor Water Level Indication

and Inad-vertent Draindown

During Shutdown Degradation

of Cooling Water Systems Due to Icing Failure of Safety Systems on Self-Shielded

Irradia-tors Because of Inadequate

Maintenance

and Training Hydrogen Gas Ignition during Closure Welding of a VSC-24 Multi-Assembly

Sealed Basket 07/25/96 07/10/96 07/05/96 06/21/96 06/18/96 06/12/96 06/11/96 05/31/96 All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for pressurized-water

reactors All holders of OLs or CPs for nuclear power reactors All holders of OLs or CPs for pressurized

water reactors All pressurized

water reactor facilities

holding an operating

license or a construction

permit All holders of OLs or CPs for nuclear power reactors All U.S. Nuclear Regulatory

Commission

irradiator

licensees

and vendors All holders of OLs or CPs for nuclear power reactors 96-37 96-36 96-35 96-34 OL -Operating

License CP -Construction

Permit

  • ~ -K> K IN 96-41 July 26, 1996 analysis, the inadvertent

opening of the low-pressure

heater bypass valve, coupled with the trip of the heater drain pumps, resulted in a feedwater temperature

drop of less than 19 *C [35 OF], and a corresponding

power increase of less than 10 percent. In the actual event, the feedwater temperature

dropped by approximately

111 *C [200 OF], and the licensee calculated

that reactor power would have increased

by approximately

35 percent without operator or protective

actions. The licensee determined

that although the initiating

events were the same, the Chapter 15 analysis did not account for the loss of extraction

steam to the high-pressure

heaters, which was the cause of the temperature

difference.

During the event, a level imbalance occurred between the two heater drain tanks, which resulted in the isolation of extraction

steam.The NRC staff review of analyses of feedwater

temperature

events at similar facilities

revealed that most of these analyses assumed similar initiating

events as the Comanche Peak analysis and had similar conclusions

concerning

the amount of feedwater

temperature

drop. The licensee has reanalyzed

the event to include a 119 *C [246 OF] feedwater

temperature

drop and concluded that all accident analysis parameters

remained within requirements.

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

project manager.Original signed by Brian K. Grimes Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

contacts:

Harry A. Freeman, RIV (817) 897-1500 E-mail: haf@nrc.gov

Chu-Yu Liang, NRR (301) 415-2878 E-mail: cyl~nrc.gov

Attachment:

List of Recently Issued NRC Information

Notices DOCUMENT NAME: G:\SSK2\INFONOT.C

P To receive a copy of this docunent, tndicate in the box CO~opy So attachment/enclosure

EsCopy with attachment/enctosure

N

  • No cops OFFICE C BC:SRXB I BC:LPECB lI (A) DW M i NAME CYLiang* RJones* AChaffee*HAFreeman*

____ _DATE 16/ 3/96 16/21/96 17/08/96 17LI/96 I OFFILIAL MLLUM LWUF* See previous concurrence

Tech Editor reviewed & concurred

on 05/28/96

~1~1 -,K)IN 96-XX July XX, 1996 for the loss of extraction

steam to ti cause of the temperature

difference.

occurred between the two heater drain of extraction

steam.he high-pressure

heaters, which was the During the event, a level imbalance tanks, which resulted in the isolation The NRC staff review of analyses of feedwater

temperature

events at similar facilities

revealed that most of these analyses assumed similar initiating

events as the Comanche Peak analysis and had similar conclusions

concerning

the amount of feedwater

temperature

drop. The licensee has reanalyzed

the event to include a 119 'C [246 'F] feedwater

temperature

drop and concluded that all accident analysis parameters

remained within requirements.

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

project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

contacts: Harry A. Freeman, RIV (817) 897-1500 E-mail: haf~nrc.gov

Chu-Yu Liang, NRR (301) 415-2878 E-mail: cyl~nrc.gov

Attachment:

List of Recently Issued NRC Information

Notices DOCUMENT NAME: G:\SSK2\INFONOT.C

P To receive a copy of this document, indicate in the box CzAopy w/o attachment/enclosure

E-Copy with attachment/enclosure

N

  • No OFFICE l kd BC: SRXB BC:PECB )D:DR NAME CYLiang* RJones* AChaffee*

BGrimes HAFreeman*

DATE 6/ 3/96 6/21/96 7/08/96 7/ /96 OFFICIAL RECORD COPY*See previous concurrence

IN 96-XX July XX, 1996 for the loss of extraction

steam to the high-pressure

heaters, which was the cause of the temperature

difference.

During the event, a level imbalance occurred between the two heater drain tanks, which resulted in the isolation of extraction

steam.The NRC staff review of analyses of feedwater

temperature

events at similar facilities

revealed that most of these analyses assumed similar initiating

events as the licensee analysis and had similar conclusions

concerning

the amount of feedwater

temperature

drop. The licensee has reanalyzed

the event pursuant to Section 50.59 of Title 10 of the Code of Federal Regulations

to include a 119 'c [246 OF] feedwater

temperature

drop and concluded

that all accident analysis parameters

remained within requirements.

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

project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

contacts:

Harry A. Freeman, RIV (817) 897-1500 E-mail: haftnrc.gov

Chu-Yu Liang, NRR (301) 415-2878 E-mail: cyl~nrc.gov

Attachment:

List of Recently Issued NRC Information

Notices DOCUMENT NAME: G:\SSK2\INFONOT.C

P To receive a copy of this document, indicate in the box C-Topy u/o attachment/enclosure

E=Copy with attachment/enclosure

N No copy OFFICE CONT:i kd l BC:SRXBLl

BC:iPECB lI (A)iD:iDRPM

I _NAME CYLiang* RJones* AChaffee*

BGrimes l _ HAFreeman*

DATE 6/ 3/96 6/21/96 7/08/96 7/ /96* See previous concurrence

OFFICIAL KLLUKV UV X!

IN 96-XX July XX, 1996 for the loss of extraction

steam to the high-pressure

heaters, which was the cause of the temperature

difference.

During the event, a level imbalance occurred between the two heater drain tanks, which resulted in the isolation of extraction

steam.The NRC staff review of analyses of feedwater

temperature

events at similar facilities

revealed that most of these analyses assumed similar initiating

events as the licensee analysis and had similar conclusions

concerning

the amount of feedwater

temperature

drop. The licensee has reanalyzed

the event pursuant to Section 50.59 of Title 10 of the Code of Federal Regulations

to include a 119 *C [246 *F] feedwater

temperature

drop and concluded

that all accident analysis parameters

remained within requirements.

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

project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

contacts:

Harry A. Freeman, RIV (817) 897-1500 Internet:haf@nrc.gov

Chu-Yu Liang, NRR (301) 415-2878 Internet:cyl

nrc.gov Attachment:

List of Recently Issued NRC Information

Notices DOCUMENT NAME: G:\SSK2\INFONOT.C

P To receive a copy of this document, Indicate in the box Conopy w/c attachment/enclosure

EnCopy with attachment/enclosure

N

  • No OFFICE CONT: Ekd BC: SLB BC:PECB (A)D:DRPM NAME CYLiang* RJones* ACh)f BGrimes l ~~HAFreeman*tVt

DATE 6/ 3/96 6/21/96 7/7/96 7/ /96 OFFICIAL RECOR COPY* See previous concurrence

K-, /IN 96-XX June XX, 1996 for the loss of extraction

steam to ti cause of the temperature

difference.

occurred between the two heater drain of extraction

steam.he high-pressure

heaters, which was the During the event, a level imbalance tanks, which resulted in the isolation The NRC staff's review of analyses of feedwater

temperature

events at similar facilities

revealed that most of these analyses assumed similar initiating

events as the licensee's

analysis and had similar conclusions

concerning

the amount of feedwater

temperature

drop. The licensee has reanalyzed

the event pursuant to Section 50.59 of Title 10 of the Code of Federal Regulations

to include a 119 'C [246 OF] feedwater

temperature

drop and concluded

that all accident analysis parameters

remained within requirements.

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

project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

contacts: Harry A. Freeman, RIV (817) 897-1500 Internet:haffnrc.gov

Chu-Yu Liang, NRR (301) 415-2878 Internet:cyl@nrc.gov

Attachment:

List of Recently Issued NRC Information

Notices DOCUMENT NAME: G:\SSK2\INFONOT.CP

To receive a copy of this document, indicate in the box Ciropy w/dattachmeft1/enctosure

EnC OFFICE CONT:jkd _l BC: SRXB E C:PECB I _ A)D:DRPM I NAME CYLiang* RJones AChaffee BGrimes HAFreeman*

I- _DATE 6/ 3/96 6/2j /96 6/ /96 6/ /96 OFFICIAL RECORD COPY I oith attachment/enclosure

1

  • No copy* See previous concurrence

IN 96-XX June XX, 1996 detection

system. The licensee believed that this system would probably not be significantly

affected by feedwater

temperatures

because of a different mass flow rate determination

method.Finally, the licensee's

final safety analysis report did not accurately

analyze this transient.

The actual events were similar to the analysis of the'Decrease

in Feedwater

Temperature

event presented

in Chapter 15. In that analysis, the inadvertent

opening of the low-pressure

heater bypass valve, coupled with the trip of the heater drain pumps, resulted in a feedwater temperature

drop of less than 35 OF, and a corresponding

power increase of less than 10 percent. In the actual event, the feedwater

temperature

dropped by approximately

200 OF, and the licensee calculated

that reactor power would have increased

by approximately

35 percent without operator or protective

actions. The licensee determined

that although the initiating

events were the same, the Chapter 15 analysis did not account for the loss of extraction

steam to the high-pressure

heaters, which was the cause of the temperature

difference.

During the event, a level imbalance

occurred between the two heater drain tanks, which resulted in the isolation

of extraction

steam.The NRC staff's review of analyses of feedwater

temperature

events at similar facilities

revealed that most of these analyses assumed similar initiating

events as the licensee's

analysis and had similar conclusions

concerning

the amount of feedwater

temperature

drop.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

project manager.Brian K. Grimes, Acting Director Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical

contacts:

Harry A. Freeman, RIV (817) 897-1500 Internet:haf@nrc.gov

Chu-Yu Liang, NRR (301) 415-2878 Internet:cyl

nrc.gov Attachment:

List of Recently Issued NRC Information

Notices DOCUMENT NAME: G:\SSK2\INFONOT.C

P To receive a copy of this docunent, indicate in the box Catopy w/o attachment/enclosure

E-C with attachment/enclosure

N

  • No copy OFFICE lCONT:kd l BC:SRXB l BC:PECB l (A)D:DRPM NAME CYLiang 9 RJones AChaffee BGrimes HAFreema r _ _DATE /96 /96 6/ /96 6/ /96 OFFICIAL RECORD COPY


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