Information Notice 1990-78, Previously Unidentified Release Path from Boiling Water Reactor Control Rod Hydraulic Units: Difference between revisions

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| issue date = 12/18/1990
| issue date = 12/18/1990
| title = Previously Unidentified Release Path from Boiling Water Reactor Control Rod Hydraulic Units
| title = Previously Unidentified Release Path from Boiling Water Reactor Control Rod Hydraulic Units
| author name = Rossi C E
| author name = Rossi C
| author affiliation = NRC/NRR
| author affiliation = NRC/NRR
| addressee name =  
| addressee name =  
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| page count = 11
| page count = 11
}}
}}
{{#Wiki_filter:UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555December 18, 1990NRC INFORMATION NOTICE NO. 90-78: PREVIOUSLY UNIDENTIFIED RELEASE PATH FROMBOILING WATER REACTOR CONTROL ROD HYDRAULICUNITS
{{#Wiki_filter:UNITED STATES
 
NUCLEAR REGULATORY COMMISSION
 
OFFICE OF NUCLEAR REACTOR REGULATION
 
WASHINGTON, D.C. 20555 December 18, 1990
NRC INFORMATION NOTICE NO. 90-78:   PREVIOUSLY UNIDENTIFIED RELEASE PATH FROM
 
BOILING WATER REACTOR CONTROL ROD HYDRAULIC
 
UNITS


==Addressees==
==Addressees==
:All holders of operating licenses or construction permits for boiling waterreactors (BWRs).
:
All holders of operating licenses or construction permits for boiling water
 
reactors (BWRs).


==Purpose==
==Purpose==
:This information notice is intended to alert addressees to potential problemspertaining to a previously unidentified release path from the control rod drivehydraulic systems in boiling water reactors that may lead to design basisaccident radiation doses significantly exceeding the values specified in theFinal Safety Analysis Report. It is expected that recipients will review theinformation for applicability to their facilities and consider actions, asappropriate, to avoid similar problems. However, suggestions contained in thisinformation notice do not constitute NRC requirements; therefore, no specificaction or written response is required.
:
This information notice is intended to alert addressees to potential problems
 
pertaining to a previously unidentified release path from the control rod drive
 
hydraulic systems in boiling water reactors that may lead to design basis
 
accident radiation doses significantly exceeding the values specified in the
 
Final Safety Analysis Report. 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 do not constitute NRC requirements; therefore, no specific
 
action or written response is required.


==Description of Circumstances==
==Description of Circumstances==
:In June 1989, a design review for unmonitored release paths at WashingtonNuclear Power Plant Unit 2 resulted in the discovery of a previously unidenti-fied radiation release path in the control rod drive hydraulic system. Thispath is postulated to result from the following sequence of conditions. Thetwo control rod drive pumps are shut down following a design basis accident.There is a break outside of the reactor building (secondary containment) inthe non-seismically qualified piping or tankage to which the control rodhydraulic system is connected (see Figure 1). Reactor coolant leaks past thedouble seals in any of the 185 control rod drives and the valves in theirassociated hydraulic control units. The leakage flows back through one ormore of the four headers connecting each of the 185 hydraulic control units tothe common control rod drive (CRD) pump header. The leakage then flows throughthe CRD pump header and the control rod drive pumps to the break or the conden-sate storage tank located outside of the reactor building.Much of the pathway to the condensate storage tank lies outside of the reactorbuilding and includes piping that is not seismically qualified. In addition,this piping passes close to the air intakes for the control room ventilationsystem. Consequently, a failure of the supply piping for the drive pumpss3 -1D8W- /'C
:
In June 1989, a design review for unmonitored release paths at Washington
 
Nuclear Power Plant Unit 2 resulted in the discovery of a previously unidenti- fied radiation release path in the control rod drive hydraulic system. This
 
path is postulated to result from the following sequence of conditions. The
 
two control rod drive pumps are shut down following a design basis accident.
 
There is a break outside of the reactor building (secondary containment) in
 
the non-seismically qualified piping or tankage to which the control rod
 
hydraulic system is connected (see Figure 1). Reactor coolant leaks past the
 
double seals in any of the 185 control rod drives and the valves in their
 
associated hydraulic control units. The leakage flows back through one or
 
more of the four headers connecting each of the 185 hydraulic control units to
 
the common control rod drive (CRD) pump header. The leakage then flows through
 
the CRD pump header and the control rod drive pumps to the break or the conden- sate storage tank located outside of the reactor building.
 
Much of the pathway to the condensate storage tank lies outside of the reactor
 
building and includes piping that is not seismically qualified. In addition, this piping passes close to the air intakes for the control room ventilation
 
system. Consequently, a failure of the supply piping for the drive pumps
 
s3                                                                -1D8W-       /'C
 
IN 90-78 December 18, 1990 during an accident would not only greatly increase the potential external
 
release, but could increase the radiation dose to the control room operators.
 
General Electric-Nuclear Energy performed calculations for the newly postulated
 
release path for a design basis accident with concurrent failure of the
 
non-seismically qualified supply piping for the control rod drive system at
 
Washington Nuclear Power Plant Unit 2. The calculations incorporated the
 
source terms specified in Regulatory Guide 1.3 and assumed that 10% of the
 
iodine would escape as a gas from the liquid release. These calculations
 
produced a 30-day thyroid dose for control room operators of 121 rem per gpm of
 
leakage, a 30-day thyroid dose at the outer boundary of the low-population zone
 
of 86 rem per gpm of leakage, and a 2-hour thyroid dose at the exclusion zone
 
boundary of 36 rem per gpm of leakage. A generic communication discussing this
 
concern was sent by General Electric-Nuclear Energy to each BWR utility in
 
July 1989.
 
Discussion:
For the control rod hydraulic systems at General Electric boiling water reac- tors, the inboard isolation for the primary containment is provided by the
 
double seals in the control rod drives, and the outboard isolation for the
 
primary containment is provided by valves within the hydraulic control units.
 
However, past leak tests of the rod drive seals that were performed by General
 
Electric produced a maximum of 5 gpm per drive. Leakage from the hydraulic
 
control units can also be significant.
 
As shown in Figure 1, four paths lead from each of the 185 hydraulic control
 
units to the common CRD pump header. Three of these paths, the accumulator
 
charging header, the drive header and the cooling header include check valves
 
to prevent the return of water from the hydraulic units. In addition, water
 
escaping through the accumulator charging header must leak through the insert
 
side scram valve, and water escaping through the drive header must leak through
 
one of the directional control valves. However, the check valve in the exhaust
 
header is oriented so as to permit the flow of water back to the CRD pump header.
 
The exhaust water then flows via the CRD pump header back to the reactor vessel
 
(or, as at Washington Nuclear Power Plant Unit 2, to the reactor water cleanup
 
system) along with the excess pump flow. Therefore, only one normally closed
 
valve prevents water that is leaking out of each of the 185 control rod drives
 
from returning through the associated exhaust header to the CRD pump header.
 
During startup testing at Limerick Unit 1, and at Susquehanna Unit 1, the total
 
leakage from all of the hydraulic control units combined was measured at 5 gpm
 
and 11 gpm, respectively. Both of these reactors include additional check valves
 
at the discharge of the control'rod drive pump (area A in Figure 1). A partial
 
audit by the NRC staff indicates that many of the newer BWR plants have check
 
valves installed in the discharge pipe of the control rod drive pumps. However, this audit also showed that other BWR plants, mostly the earlier ones, did not
 
have such check valves. The control rod drive system for BWR/6 plants is de- signed with a testable check valve and a motor-operated isolation valve. There- fore, this pathway is applicable to pre-BWR/6 plants only.
 
Ie
 
IN 90-78 December 18, 1990 Combining the General Electric dose calculations for the postulated path with
 
the leak rates measured from the hydraulic units at either Limerick or
 
Susquehanna produces dose rates significantly in excess of the values in the
 
Final Safety Analysis Report. Independent calculations by the NRC staff pro- duced offsite dose values that were comparable to the General Electric results.
 
Radiation release by this path is not possible as long as the control rod drive
 
pumps are kept running. However, continued operation of these pumps following
 
an accident cannot be assured, particularly if the non-seismically qualified
 
suction piping were to fail.
 
This problem was resolved at Washington Nuclear Power Plant Unit 2 by the
 
installation of two check valves in series in the common discharge pipe from
 
the control rod drive pumps (at area A in Figure 1) to prevent backflow out of
 
the reactor building (secondary containment). The Washington Nuclear Power
 
Plant Unit 2 installation includes provisions for leak testing the valves and
 
a leak rate criterion of 0.01 gpm was established for these valves.
 
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 NRR project manager.
 
Division of Operational Events Assessment
 
Office of Nuclear Reactor Regulation
 
Technical Contacts:  Charles R. Nichols, NRR
 
(301) 492-0854 Donald C. Kirkpatrick, NRR
 
(301) 492-1849 Attachments:
1. Figure 1. BWR Control Rod Drive System
 
2. List of Recently Issued NRC Information Notices
 
Note: At Washington Nuclear Power
 
Plant, Unit 2, the control rod drive
 
return water Is piped to the reactor w
 
water cleanup system
 
SvITE..t.                                                .... \SECONDONDARY
 
OAin4Z(                      EXHAUST            CWHIOL VALV(S                CONTAINMENT
 
~I ~>*PCV                                      "(E
 
S                CU
 
OUTSIDE OF                                        DRV
 
BUILDINGA-H
 
AREA
 
A                                                    SCIM VALVIE
 
6TaLQUT1                            COTROL4MmuMRG
 
RMOO140MIX        ROD
 
To              OTHE
 
CONTARNEN R-OD                                                        -.                    I.-AJ___
                                                                                                                  CrI
 
DRIVEPUMPSM
 
0
                                                                                                                    ~j
 
c
 
Figure 1. BWR CONTROL ROD DRIVE SYSTEM
 
Attachment 2 IN 90-78 December 18, 1990 LIST OF RECENTLY ISSUED
 
NRC INFORMATION NOTICES
 
Information                                    Date of
 
Notice No.              Subject                Issuance      Issued to
 
90-77          Inadvertent Removal of Fuel    12/12/90 All holders of OLs or
 
Assemblies from the Reactor              CPs for pressurized- Core                                    water reactors (PWRS).
 
88-23,        Potential for Gas Binding of 12/10/90    All holders of OLs or
 
Supp. 3        High-Pressure Safety Injection          CPs for pressurized- Pumps During A Loss-Of-Coolant          water reactors (PWRs).
 
Accident
 
90-76          Failure Of Turbine Overspeed    12/7/90  All holders of OLs or
 
Trip Mechanism Because Of                CPs for nuclear power
 
Inadequate Spring Tension                reactors.
 
90-75          Denial Of Access To Current    12/5/90  All Michigan holders
 
Low-Level Radioactive Waste              of NRC licenses.
 
Disposal Facilities
 
90-74          Information on Precursors To    12/4/90  All holders of OLs or
 
Severe Accidents                        CPs for nuclear power
 
reactors.
 
90-73          Corrosion Of Valve-To-          11/29/90 All holders of OLs or
 
Torque Tube Keys In                      CPs for nuclear power
 
Spray Pond Cross Connect                reactors.
 
Valves
 
90-72          Testing of Parallel Disc        11/28/90 All holders of OLs or
 
Gate Valves In Europe                    CPs for nuclear power
 
reactors.
 
90-71          Effective Use of Radi-          11/6/90  All NRC licensees
 
ation Safety Committees                  authorized to use by- to Exercise Control Over                product material for
 
Medical Use Programs                    medical purposes.
 
90-70          Pump Explosions Involving      11/6/90  All uranium fuel
 
Ammonium Nitrate                        fabrication and
 
conversion facilities.
 
90-38,        License and Fee Require-        11/6/90  All fuel facility and
 
Supp. 1        ments for Processing Fin-                materials licensees.
 
ancial Assurance Submittals
 
for Decommissioning
 
OL = Operating License
 
CP = Construction Permit
 
IN 90-78 December 18, 1990 Combining the General Electric dose calculations for the postulated path with
 
the leak rates measured from the hydraulic units at either Limerick or
 
Susquehanna produces dose rates significantly in excess of the values in the
 
Final Safety Analysis Report. Independent calculations by the NRC staff pro- duced offsite dose values that were comparable to the General Electric results.
 
Radiation release by this path is not possible as long as the control rod drive
 
pumps are kept running. However, continued operation of these pumps following
 
an accident cannot be assured, particularly if the non-seismically qualified
 
suction piping were to fail.
 
This problem was resolved at Washington Nuclear Power Plant Unit 2 by the
 
installation of two check valves in series in the common discharge pipe from
 
the control rod drive pumps (at area A in Figure 1) to prevent backflow out of
 
the reactor building (secondary containment). The Washington Nuclear Power
 
Plant Unit 2 installation includes provisions for leak testing the valves and
 
a leak rate criterion of 0.01 gpm was established for these valves.
 
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 NRR project manager.
 
Origina Signkd IN
 
Charles E Rossi
 
Charles E. Rossi, Director
 
Division of Operational Events Assessment
 
Office of Nuclear Reactor Regulation
 
Technical Contacts:    Charles R. Nichols, NRR
 
(301) 492-0854 Donald C. Kirkpatrick, NRR
 
(301) 492-1849 Attachments:
1. Figure 1. BWR Control Rod Drive System
 
2. List of Recently Issued NRC Information Notices
 
*12/11/90
                                                                NJDi*C/OGCB:DOEA:NRR
 
CHBerlinger
 
12/L~/jW 111/09/90
*OGCB:DOEA:NRR *SPLB:DST:NRR    *C/SPLB:DST:NRR        *D/U ST:NRR *RPB:ADM
 
DCKirkpatrick CRNichols        CMcCracken              AThadani    TechEd
 
08/17/90      08/20/90        09/24/90                10/30/90    08/06/90
DOCUMENT NAME:  IN 90-78
 
IN 90-XX
 
August xx, 1990 for these and other plants produced offsite dose values that were comparable
 
to the General Electric results and that could also significantly exceed the
 
values specified in the Final Safety Analysis Report. Radiation release by
 
this path is not possible as long as the control rod drive pumps are kept
 
running. However, continued operation of these pumps following an accident
 
cannot be ensured, particularly if the non-seismically qualified suction piping
 
were to fall.
 
This problem was resolved at Washington Nuclear Power Plant Unit 2 by the


IN 90-78December 18, 1990 during an accident would not only greatly increase the potential externalrelease, but could increase the radiation dose to the control room operators.General Electric-Nuclear Energy performed calculations for the newly postulatedrelease path for a design basis accident with concurrent failure of thenon-seismically qualified supply piping for the control rod drive system atWashington Nuclear Power Plant Unit 2. The calculations incorporated thesource terms specified in Regulatory Guide 1.3 and assumed that 10% of theiodine would escape as a gas from the liquid release. These calculationsproduced a 30-day thyroid dose for control room operators of 121 rem per gpm ofleakage, a 30-day thyroid dose at the outer boundary of the low-population zoneof 86 rem per gpm of leakage, and a 2-hour thyroid dose at the exclusion zoneboundary of 36 rem per gpm of leakage. A generic communication discussing thisconcern was sent by General Electric-Nuclear Energy to each BWR utility inJuly 1989.Discussion:For the control rod hydraulic systems at General Electric boiling water reac-tors, the inboard isolation for the primary containment is provided by thedouble seals in the control rod drives, and the outboard isolation for theprimary containment is provided by valves within the hydraulic control units.However, past leak tests of the rod drive seals that were performed by GeneralElectric produced a maximum of 5 gpm per drive. Leakage from the hydrauliccontrol units can also be significant.As shown in Figure 1, four paths lead from each of the 185 hydraulic controlunits to the common CRD pump header. Three of these paths, the accumulatorcharging header, the drive header and the cooling header include check valvesto prevent the return of water from the hydraulic units. In addition, waterescaping through the accumulator charging header must leak through the insertside scram valve, and water escaping through the drive header must leak throughone of the directional control valves. However, the check valve in the exhaustheader is oriented so as to permit the flow of water back to the CRD pump header.The exhaust water then flows via the CRD pump header back to the reactor vessel(or, as at Washington Nuclear Power Plant Unit 2, to the reactor water cleanupsystem) along with the excess pump flow. Therefore, only one normally closedvalve prevents water that is leaking out of each of the 185 control rod drivesfrom returning through the associated exhaust header to the CRD pump header.During startup testing at Limerick Unit 1, and at Susquehanna Unit 1, the totalleakage from all of the hydraulic control units combined was measured at 5 gpmand 11 gpm, respectively. Both of these reactors include additional check valvesat the discharge of the control'rod drive pump (area A in Figure 1). A partialaudit by the NRC staff indicates that many of the newer BWR plants have checkvalves installed in the discharge pipe of the control rod drive pumps. However,this audit also showed that other BWR plants, mostly the earlier ones, did nothave such check valves. The control rod drive system for BWR/6 plants is de-signed with a testable check valve and a motor-operated isolation valve. There-fore, this pathway is applicable to pre-BWR/6 plants only.
installation of two check valves in series in the common discharge pipe from


IeIN 90-78December 18, 1990 Combining the General Electric dose calculations for the postulated path withthe leak rates measured from the hydraulic units at either Limerick orSusquehanna produces dose rates significantly in excess of the values in theFinal Safety Analysis Report. Independent calculations by the NRC staff pro-duced offsite dose values that were comparable to the General Electric results.Radiation release by this path is not possible as long as the control rod drivepumps are kept running. However, continued operation of these pumps followingan accident cannot be assured, particularly if the non-seismically qualifiedsuction piping were to fail.This problem was resolved at Washington Nuclear Power Plant Unit 2 by theinstallation of two check valves in series in the common discharge pipe fromthe control rod drive pumps (at area A in Figure 1) to prevent backflow out ofthe reactor building (secondary containment). The Washington Nuclear PowerPlant Unit 2 installation includes provisions for leak testing the valves anda leak rate criterion of 0.01 gpm was established for these valves.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.Division of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: Charles R. Nichols, NRR(301) 492-0854Donald C. Kirkpatrick, NRR(301) 492-1849Attachments:1. Figure 1. BWR Control Rod Drive System2. List of Recently Issued NRC Information Notices
the control rod drive pumps to prevent back flow out of the secondary contain- ment. The Washington Nuclear Power Plant Unit 2 installation includes provisions


Note: At Washington Nuclear PowerPlant, Unit 2, the control rod drivereturn water Is piped to the reactor wwater cleanup systemSvITE..t. .... \SECONDONDARYOAin4Z( EXHAUST CWHIOL VALV(S CONTAINMENT~I ~>*PCV "(ES CUOUTSIDE OF DRVBUILDINGA-HAREAA SCIM VALVIE6TaLQUT1 COTROL4MmuMRGRMOO140MIX RODTo OTHECONTARNEN R-OD I.-AJ___ -. CrIDRIVEPUMPSM ~j0 cFigure 1. BWR CONTROL ROD DRIVE SYSTEM
for leak testing the valves. Washington Nuclear Power Plant Unit 2 planned to


Attachment 2IN 90-78December 18, 1990 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to90-7788-23,Supp. 390-7690-7590-7490-7390-7290-7190-7090-38,Supp. 1Inadvertent Removal of FuelAssemblies from the ReactorCorePotential for Gas Binding ofHigh-Pressure Safety InjectionPumps During A Loss-Of-CoolantAccidentFailure Of Turbine OverspeedTrip Mechanism Because OfInadequate Spring TensionDenial Of Access To CurrentLow-Level Radioactive WasteDisposal FacilitiesInformation on Precursors ToSevere AccidentsCorrosion Of Valve-To-Torque Tube Keys InSpray Pond Cross ConnectValvesTesting of Parallel DiscGate Valves In EuropeEffective Use of Radi-ation Safety Committeesto Exercise Control OverMedical Use ProgramsPump Explosions InvolvingAmmonium NitrateLicense and Fee Require-ments for Processing Fin-ancial Assurance Submittalsfor Decommissioning12/12/9012/10/9012/7/9012/5/9012/4/9011/29/9011/28/9011/6/9011/6/9011/6/90All holders of OLs orCPs for pressurized-water reactors (PWRS).All holders of OLs orCPs for pressurized-water reactors (PWRs).All holders of OLs orCPs for nuclear powerreactors.All Michigan holdersof NRC licenses.All holders of OLs orCPs for nuclear powerreactors.All holders of OLs orCPs for nuclear powerreactors.All holders of OLs orCPs for nuclear powerreactors.All NRC licenseesauthorized to use by-product material formedical purposes.All uranium fuelfabrication andconversion facilities.All fuel facility andmaterials licensees.OL = Operating LicenseCP = Construction Permit
establish a leak rate criterion for these valves of 0.01 gpm.


IN 90-78December 18, 1990 Combining the General Electric dose calculations for the postulated path withthe leak rates measured from the hydraulic units at either Limerick orSusquehanna produces dose rates significantly in excess of the values in theFinal Safety Analysis Report. Independent calculations by the NRC staff pro-duced offsite dose values that were comparable to the General Electric results.Radiation release by this path is not possible as long as the control rod drivepumps are kept running. However, continued operation of these pumps followingan accident cannot be assured, particularly if the non-seismically qualifiedsuction piping were to fail.This problem was resolved at Washington Nuclear Power Plant Unit 2 by theinstallation of two check valves in series in the common discharge pipe fromthe control rod drive pumps (at area A in Figure 1) to prevent backflow out ofthe reactor building (secondary containment). The Washington Nuclear PowerPlant Unit 2 installation includes provisions for leak testing the valves anda leak rate criterion of 0.01 gpm was established for these valves.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.Origina Signkd INCharles E RossiCharles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: Charles R. Nichols, NRR(301) 492-0854Donald C. Kirkpatrick, NRR(301) 492-1849Attachments:1. Figure 1. BWR Control Rod Drive System2. List of Recently Issued NRC Information Notices*12/11/90NJDi *C/OGCB:DOEA:NRRCHBerlinger12/L~/jW 111/09/90*OGCB:DOEA:NRR *SPLB:DST:NRR *C/SPLB:DST:NRR *D/U ST:NRR *RPB:ADMDCKirkpatrick CRNichols CMcCracken AThadani TechEd08/17/90 08/20/90 09/24/90 10/30/90 08/06/90DOCUMENT NAME: IN 90-78 IN 90-XXAugust xx, 1990 for these and other plants produced offsite dose values that were comparableto the General Electric results and that could also significantly exceed thevalues specified in the Final Safety Analysis Report. Radiation release bythis path is not possible as long as the control rod drive pumps are keptrunning. However, continued operation of these pumps following an accidentcannot be ensured, particularly if the non-seismically qualified suction pipingwere to fall.This problem was resolved at Washington Nuclear Power Plant Unit 2 by theinstallation of two check valves in series in the common discharge pipe fromthe control rod drive pumps to prevent back flow out of the secondary contain-ment. The Washington Nuclear Power Plant Unit 2 installation includes provisionsfor leak testing the valves. Washington Nuclear Power Plant Unit 2 planned toestablish a leak rate criterion for these valves of 0.01 gpm.The control rod drive system for BWR/6 plants is designed with a testablecheck valve and a motor-operated isolation valve, therefore this pathway isapplicable to only pre-BWR/6 plants.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact thetechnical contact listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: Charles R. Nichols, NRR(301) 492-0856Donald C. Kirkpatrick, NRR(301) 492-1849Attachments:1. Figure of Control Rod Hydraulic System2. List of Recently Issued NRC Information NoticesDocument Name: UNIDENTIFIED RELEASE PATH IN*SEE PREVIOUS CONCURRENCESD/DOEA:NRR C/OGCB:DOEA:NRRCERossi CHBerlinger10/ /90 10/ /90OGCB:DOEA:NRR SPLB:DST:NRR C/SPLB:DST:NRR D/DST:NRRK4 RPB:ADMDCKirkpatrick* CRNichols* CMcCracken* AThadani TechEd*08/17/90 08/20/90 09/24/90 10M /90 08/06/90  
The control rod drive system for BWR/6 plants is designed with a testable
1990Page 3 f 3Combining the General Electric dose calculations for the postulated path withthe leak rates measured from the hydraulic units at either Limerick orSusquehanna produces dose rates significantly in excess of the values specifiedin the Final Safety Analysis Report. Independent calculations by the NRC staffproduced offsite dose values that were comparable to the General Electricresults and that could also significantly exceed the values specified in theFinal Safety Analysis Report. Radiation release by this path is not possibleas long as the control rod drive pumps are kept running. However, continuedoperation of these pumps following an accident cannot be assured, particularlyif the non-seismically qualified suction piping were to fail.This problem was resolved at Washington Nuclear Power Plant Unit 2 by theinstallation of two check valves in series in the common discharge pipe fromthe control rod drive pumps (at area A) to prevent backflow out of the reactorbuilding secondary containment. The Washington Nuclear Power Plant Unit 2installation includes provisions for leak testing the valves and a leak ratecriterion of 0.01 gpm was established for these valves.This information notice requiresyou have any questions about theof the technical contacts listedno specific action or written response. Ifinformation in this notice, please contact onebelow or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:Charles R. Nichols, NRR(301) 492-0854Donald C. Kirkpatrick, NRR(301) 492-1849Attachments:1. Figure 1. BWR Control Rod Drive System2. List of Recently Issued NRC Information NoticesDocument Name:RELEASE PATH NOTICED/DOEA:NRRCERossi11/ /90*D/DST:NRRAThadani10/30/90ok 1vko .*C/OGCB:DOEA:NRRCHBerlinger11/09/90*RPB:ADMTechEd08/06/90*OGCB:DOEA:NRRDCKirkpatrick08/17/90*SPLB:DST:NRRCRNichols08/20/90*C/SPLB:DST:NRRCMcCracken09/24/90  
 
IN 90-XXAugust xx, 1990 this path is not possible as long as the control rod drive pumps are keptrunning. However, continued operation of these pumps following an accidentcannot be ensured, particularly if the non-seismically qualified suction pipingwere to fail.This problem was resolved at Washington Nuclear Power Plant Unit 2 by theinstallation of two check valves in series in the common discharge pipe fromthe control rod drive pumps to prevent back flow out of the secondary contain-ment. The Washington Nuclear Power Plant Unit 2 installation includes provisionsfor leak testing the valves. Washington Nuclear Power Plant Unit 2 planned toestablish a leak rate criterion for these valves of 0.01 gpm.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact thetechnical contact listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:Charles R. Nichols, NRR(301) 492-0856Donald C. Kirkpatrick, NRR(301) 492-1849Attachments:1. Figure of Control Rod Hydraulic System2. List of Recently Issued NRC Information NoticesDocument Name:UNIDENTIFIED RELEASE PATH IN*SEE PREVIOUS CONCURRENCESOGCB:W EA:NRRDOrirkpathick08/e 9/90 VC<SPLB:DST:NRRCRNichols08AV2/9M;*^CISPLB:DST:NRRCMcCrackenOF/p/90D/DOEA:NRRCERossi08/ /90D/DST:NRRAThadani408/ /90V1C/OGCB:DOEA:NRRCHBerlinger08/ /90*RPB:ADMTechEd08/06/90  
check valve and a motor-operated isolation valve, therefore this pathway is
IN 90-XXAugust xx, 1990 The Washington Nuclear power installation includes provisions for leak testingthe valves. Washington Nuclear Power has established a very low leak ratecriterion for these valves (.01 gpm was indicated). A partial check by the NRCstaff indicates that many of the newer BWR plants already have check valvesinstalled in the control rod drive pump discharge pipe. However, this checkalso showed that other BWR plants, mainly the earlier ones, did not have suchcheck valves.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact thetechnical contact listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor Regulation
 
applicable to only pre-BWR/6 plants.
 
This information notice requires no specific action or written response. If
 
you have any questions about the information in this notice, please contact the
 
technical contact listed below or the appropriate NRR project manager.
 
Charles E. Rossi, Director
 
Division of Operational Events Assessment
 
Office of Nuclear Reactor Regulation
 
Technical Contacts:   Charles R. Nichols, NRR
 
(301) 492-0856 Donald C. Kirkpatrick, NRR
 
(301) 492-1849 Attachments:
1. Figure of Control Rod Hydraulic System
 
2. List of Recently Issued NRC Information Notices
 
Document Name: UNIDENTIFIED RELEASE PATH IN
 
*SEE PREVIOUS CONCURRENCES
 
D/DOEA:NRR     C/OGCB:DOEA:NRR
 
CERossi      CHBerlinger
 
10/   /90     10/ /90
OGCB:DOEA:NRR       SPLB:DST:NRR   C/SPLB:DST:NRR       D/DST:NRRK4 RPB:ADM
 
DCKirkpatrick*     CRNichols*     CMcCracken*         AThadani       TechEd*
08/17/90           08/20/90       09/24/90             10M /90       08/06/90
 
1990
                                                                Page 3 f 3 Combining the General Electric dose calculations for     the postulated path with
 
at  either  Limerick or
 
the leak rates measured from the hydraulic units in excess  of the values specified
 
Susquehanna produces dose rates significantly       calculations    by the NRC staff
 
in the Final Safety Analysis Report. Independent to the General Electric
 
produced offsite dose values that were comparable the values specified in the
 
results and that could also significantly exceed by this path is not possible
 
Final Safety Analysis Report. Radiation release running. However, continued
 
as long as the control rod drive pumps are kept cannot be assured, particularly
 
operation of these pumps following an accident were to fail.
 
if the non-seismically qualified suction piping
 
This problem was resolved at Washington Nuclear   Power Plant Unit 2 by the
 
installation of two check valves in series   in the common discharge pipe from
 
the control rod drive pumps (at area   A) to prevent backflow out of the reactor
 
building secondary containment. The Washington Nuclear     Power Plant Unit 2 and a leak rate
 
installation includes provisions for leak testing the valves
 
criterion of 0.01 gpm was established for these valves.
 
or written response. If
 
This information notice requires no specific action
 
in this notice, please contact one
 
you have any questions about the information appropriate NRR project manager.
 
of the  technical contacts listed below or the
 
Charles E. Rossi, Director
 
Division of Operational Events Assessment
 
Office of Nuclear Reactor Regulation
 
Technical Contacts:   Charles R. Nichols, NRR
 
(301) 492-0854 Donald C. Kirkpatrick, NRR
 
(301) 492-1849 Attachments:
  1. Figure 1. BWR Control Rod Drive System
 
2. List of Recently Issued NRC Information Notices
 
Document Name:   RELEASE PATH NOTICE                                ok      1vko .
 
D/DOEA:NRR *C/OGCB:DOEA:NRR
 
CERossi      CHBerlinger
 
11/  /90     11/09/90
                                  *C/SPLB:DST:NRR      *D/DST:NRR    *RPB:ADM
 
*OGCB:DOEA:NRR *SPLB:DST:NRR                                        TechEd
 
DCKirkpatrick CRNichols        CMcCracken            AThadani
 
08/20/90       09/24/90              10/30/90      08/06/90
    08/17/90
 
IN 90-XX
 
August xx, 1990 this path is not possible as long as the control rod drive pumps are kept
 
running. However, continued operation of these pumps following an accident
 
cannot be ensured, particularly if the non-seismically qualified suction piping
 
were to fail.
 
This problem was resolved at Washington Nuclear Power Plant Unit 2 by the
 
installation of two check valves in series in the common discharge pipe from
 
the control rod drive pumps to prevent back flow out of the secondary contain- ment. The Washington Nuclear Power Plant Unit 2 installation includes provisions
 
for leak testing the valves. Washington Nuclear Power Plant Unit 2 planned to
 
establish a leak rate criterion for these valves of 0.01 gpm.
 
This information notice requires no specific action or written response. If
 
you have any questions about the information in this notice, please contact the
 
technical contact listed below or the appropriate NRR project manager.
 
Charles E. Rossi, Director
 
Division of Operational Events Assessment
 
Office of Nuclear Reactor Regulation
 
Technical Contacts:   Charles R. Nichols, NRR
 
(301) 492-0856 Donald C. Kirkpatrick, NRR
 
(301) 492-1849 Attachments:
1. Figure of Control Rod Hydraulic System
 
2. List of Recently Issued NRC Information Notices
 
Document Name: UNIDENTIFIED RELEASE PATH IN
 
*SEE PREVIOUS CONCURRENCES
 
D/DOEA:NRR    C/OGCB:DOEA:NRR
 
CERossi      CHBerlinger
 
08/ /90      08/ /90
OGCB:W EA:NRR SPLB:DST:NRR    CISPLB:DST:NRR      D/DST:NRR    *RPB:ADM
 
DOrirkpathick CRNichols      CMcCracken          AThadani      TechEd
 
08/e 9/90VC< 08AV2/9M;*^      OF/p/90            408/ /90       08/06/90
                                                V1
 
IN 90-XX
 
August xx, 1990 The Washington Nuclear power installation includes provisions for leak testing
 
the valves. Washington Nuclear Power has established a very low leak rate
 
criterion for these valves (.01 gpm was indicated). A partial check by the NRC
 
staff indicates that many of the newer BWR plants already have check valves
 
installed in the control rod drive pump discharge pipe. However, this check
 
also showed that other BWR plants, mainly the earlier ones, did not have such
 
check valves.
 
This information notice requires no specific action or written response. If
 
you have any questions about the information in this notice, please contact the
 
technical contact listed below or the appropriate NRR project manager.
 
Charles E. Rossi, Director
 
Division of Operational Events Assessment
 
Office of Nuclear Reactor Regulation


===Technical Contact:===
===Technical Contact:===
Charles R. Nichols, NRR(301) 492-0854Attachments:1. Figure of Control Rod Hydraulic System2. List of Recently Issued NRC Information NoticesDocument Name:UNIDENTIFIED RELEASE PATH IND/DOEA:NRRCERossi08/ /90D/DST:NRRAThadani08/ /90C/OGCB:DOEA:NRRCHBerlinger08/ /90RPB:ADMTechEd J ai P08/C /90OGCB:DOEA:NRR SPLB:DST:NRRDCKirkpatyi .- CRNichols08/' /9 xF 08/ /goC/SPLB:DST:NRRCMcCracken08/ /90  
 
}}
===Charles R. Nichols, NRR===
                    (301) 492-0854 Attachments:
1. Figure of Control Rod Hydraulic System
 
2. List of Recently Issued NRC Information Notices
 
Document Name: UNIDENTIFIED RELEASE PATH IN
 
D/DOEA:NRR  C/OGCB:DOEA:NRR
 
CERossi      CHBerlinger
 
08/ /90      08/ /90
OGCB:DOEA:NRR SPLB:DST:NRR    C/SPLB:DST:NRR     D/DST:NRR    RPB:ADM
 
DCKirkpatyi .-CRNichols      CMcCracken          AThadani    TechEd J ai P
 
08/' /9     xF 08/ /go        08/ /90            08/ /90      08/C /90}}


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

Latest revision as of 04:04, 24 November 2019

Previously Unidentified Release Path from Boiling Water Reactor Control Rod Hydraulic Units
ML031130145
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: 12/18/1990
From: Rossi C
Office of Nuclear Reactor Regulation
To:
References
IN-90-078, NUDOCS 9012120148
Download: ML031130145 (11)
v • d • e


UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 December 18, 1990

NRC INFORMATION NOTICE NO. 90-78: PREVIOUSLY UNIDENTIFIED RELEASE PATH FROM

BOILING WATER REACTOR CONTROL ROD HYDRAULIC

UNITS

Addressees

All holders of operating licenses or construction permits for boiling water

reactors (BWRs).

Purpose

This information notice is intended to alert addressees to potential problems

pertaining to a previously unidentified release path from the control rod drive

hydraulic systems in boiling water reactors that may lead to design basis

accident radiation doses significantly exceeding the values specified in the

Final Safety Analysis Report. 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 do not constitute NRC requirements; therefore, no specific

action or written response is required.

Description of Circumstances

In June 1989, a design review for unmonitored release paths at Washington

Nuclear Power Plant Unit 2 resulted in the discovery of a previously unidenti- fied radiation release path in the control rod drive hydraulic system. This

path is postulated to result from the following sequence of conditions. The

two control rod drive pumps are shut down following a design basis accident.

There is a break outside of the reactor building (secondary containment) in

the non-seismically qualified piping or tankage to which the control rod

hydraulic system is connected (see Figure 1). Reactor coolant leaks past the

double seals in any of the 185 control rod drives and the valves in their

associated hydraulic control units. The leakage flows back through one or

more of the four headers connecting each of the 185 hydraulic control units to

the common control rod drive (CRD) pump header. The leakage then flows through

the CRD pump header and the control rod drive pumps to the break or the conden- sate storage tank located outside of the reactor building.

Much of the pathway to the condensate storage tank lies outside of the reactor

building and includes piping that is not seismically qualified. In addition, this piping passes close to the air intakes for the control room ventilation

system. Consequently, a failure of the supply piping for the drive pumps

s3 -1D8W- /'C

IN 90-78 December 18, 1990 during an accident would not only greatly increase the potential external

release, but could increase the radiation dose to the control room operators.

General Electric-Nuclear Energy performed calculations for the newly postulated

release path for a design basis accident with concurrent failure of the

non-seismically qualified supply piping for the control rod drive system at

Washington Nuclear Power Plant Unit 2. The calculations incorporated the

source terms specified in Regulatory Guide 1.3 and assumed that 10% of the

iodine would escape as a gas from the liquid release. These calculations

produced a 30-day thyroid dose for control room operators of 121 rem per gpm of

leakage, a 30-day thyroid dose at the outer boundary of the low-population zone

of 86 rem per gpm of leakage, and a 2-hour thyroid dose at the exclusion zone

boundary of 36 rem per gpm of leakage. A generic communication discussing this

concern was sent by General Electric-Nuclear Energy to each BWR utility in

July 1989.

Discussion:

For the control rod hydraulic systems at General Electric boiling water reac- tors, the inboard isolation for the primary containment is provided by the

double seals in the control rod drives, and the outboard isolation for the

primary containment is provided by valves within the hydraulic control units.

However, past leak tests of the rod drive seals that were performed by General

Electric produced a maximum of 5 gpm per drive. Leakage from the hydraulic

control units can also be significant.

As shown in Figure 1, four paths lead from each of the 185 hydraulic control

units to the common CRD pump header. Three of these paths, the accumulator

charging header, the drive header and the cooling header include check valves

to prevent the return of water from the hydraulic units. In addition, water

escaping through the accumulator charging header must leak through the insert

side scram valve, and water escaping through the drive header must leak through

one of the directional control valves. However, the check valve in the exhaust

header is oriented so as to permit the flow of water back to the CRD pump header.

The exhaust water then flows via the CRD pump header back to the reactor vessel

(or, as at Washington Nuclear Power Plant Unit 2, to the reactor water cleanup

system) along with the excess pump flow. Therefore, only one normally closed

valve prevents water that is leaking out of each of the 185 control rod drives

from returning through the associated exhaust header to the CRD pump header.

During startup testing at Limerick Unit 1, and at Susquehanna Unit 1, the total

leakage from all of the hydraulic control units combined was measured at 5 gpm

and 11 gpm, respectively. Both of these reactors include additional check valves

at the discharge of the control'rod drive pump (area A in Figure 1). A partial

audit by the NRC staff indicates that many of the newer BWR plants have check

valves installed in the discharge pipe of the control rod drive pumps. However, this audit also showed that other BWR plants, mostly the earlier ones, did not

have such check valves. The control rod drive system for BWR/6 plants is de- signed with a testable check valve and a motor-operated isolation valve. There- fore, this pathway is applicable to pre-BWR/6 plants only.

Ie

IN 90-78 December 18, 1990 Combining the General Electric dose calculations for the postulated path with

the leak rates measured from the hydraulic units at either Limerick or

Susquehanna produces dose rates significantly in excess of the values in the

Final Safety Analysis Report. Independent calculations by the NRC staff pro- duced offsite dose values that were comparable to the General Electric results.

Radiation release by this path is not possible as long as the control rod drive

pumps are kept running. However, continued operation of these pumps following

an accident cannot be assured, particularly if the non-seismically qualified

suction piping were to fail.

This problem was resolved at Washington Nuclear Power Plant Unit 2 by the

installation of two check valves in series in the common discharge pipe from

the control rod drive pumps (at area A in Figure 1) to prevent backflow out of

the reactor building (secondary containment). The Washington Nuclear Power

Plant Unit 2 installation includes provisions for leak testing the valves and

a leak rate criterion of 0.01 gpm was established for these valves.

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 NRR project manager.

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Charles R. Nichols, NRR

(301) 492-0854 Donald C. Kirkpatrick, NRR

(301) 492-1849 Attachments:

1. Figure 1. BWR Control Rod Drive System

2. List of Recently Issued NRC Information Notices

Note: At Washington Nuclear Power

Plant, Unit 2, the control rod drive

return water Is piped to the reactor w

water cleanup system

SvITE..t. .... \SECONDONDARY

OAin4Z( EXHAUST CWHIOL VALV(S CONTAINMENT

~I ~>*PCV "(E

S CU

OUTSIDE OF DRV

BUILDINGA-H

AREA

A SCIM VALVIE

6TaLQUT1 COTROL4MmuMRG

RMOO140MIX ROD

To OTHE

CONTARNEN R-OD -. I.-AJ___

CrI

DRIVEPUMPSM

0

~j

c

Figure 1. BWR CONTROL ROD DRIVE SYSTEM

Attachment 2 IN 90-78 December 18, 1990 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

90-77 Inadvertent Removal of Fuel 12/12/90 All holders of OLs or

Assemblies from the Reactor CPs for pressurized- Core water reactors (PWRS).

88-23, Potential for Gas Binding of 12/10/90 All holders of OLs or

Supp. 3 High-Pressure Safety Injection CPs for pressurized- Pumps During A Loss-Of-Coolant water reactors (PWRs).

Accident

90-76 Failure Of Turbine Overspeed 12/7/90 All holders of OLs or

Trip Mechanism Because Of CPs for nuclear power

Inadequate Spring Tension reactors.

90-75 Denial Of Access To Current 12/5/90 All Michigan holders

Low-Level Radioactive Waste of NRC licenses.

Disposal Facilities

90-74 Information on Precursors To 12/4/90 All holders of OLs or

Severe Accidents CPs for nuclear power

reactors.

90-73 Corrosion Of Valve-To- 11/29/90 All holders of OLs or

Torque Tube Keys In CPs for nuclear power

Spray Pond Cross Connect reactors.

Valves

90-72 Testing of Parallel Disc 11/28/90 All holders of OLs or

Gate Valves In Europe CPs for nuclear power

reactors.

90-71 Effective Use of Radi- 11/6/90 All NRC licensees

ation Safety Committees authorized to use by- to Exercise Control Over product material for

Medical Use Programs medical purposes.

90-70 Pump Explosions Involving 11/6/90 All uranium fuel

Ammonium Nitrate fabrication and

conversion facilities.

90-38, License and Fee Require- 11/6/90 All fuel facility and

Supp. 1 ments for Processing Fin- materials licensees.

ancial Assurance Submittals

for Decommissioning

OL = Operating License

CP = Construction Permit

IN 90-78 December 18, 1990 Combining the General Electric dose calculations for the postulated path with

the leak rates measured from the hydraulic units at either Limerick or

Susquehanna produces dose rates significantly in excess of the values in the

Final Safety Analysis Report. Independent calculations by the NRC staff pro- duced offsite dose values that were comparable to the General Electric results.

Radiation release by this path is not possible as long as the control rod drive

pumps are kept running. However, continued operation of these pumps following

an accident cannot be assured, particularly if the non-seismically qualified

suction piping were to fail.

This problem was resolved at Washington Nuclear Power Plant Unit 2 by the

installation of two check valves in series in the common discharge pipe from

the control rod drive pumps (at area A in Figure 1) to prevent backflow out of

the reactor building (secondary containment). The Washington Nuclear Power

Plant Unit 2 installation includes provisions for leak testing the valves and

a leak rate criterion of 0.01 gpm was established for these valves.

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 NRR project manager.

Origina Signkd IN

Charles E Rossi

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Charles R. Nichols, NRR

(301) 492-0854 Donald C. Kirkpatrick, NRR

(301) 492-1849 Attachments:

1. Figure 1. BWR Control Rod Drive System

2. List of Recently Issued NRC Information Notices

  • 12/11/90

NJDi*C/OGCB:DOEA:NRR

CHBerlinger

12/L~/jW 111/09/90

  • OGCB:DOEA:NRR *SPLB:DST:NRR *C/SPLB:DST:NRR *D/U ST:NRR *RPB:ADM

DCKirkpatrick CRNichols CMcCracken AThadani TechEd

08/17/90 08/20/90 09/24/90 10/30/90 08/06/90

DOCUMENT NAME: IN 90-78

IN 90-XX

August xx, 1990 for these and other plants produced offsite dose values that were comparable

to the General Electric results and that could also significantly exceed the

values specified in the Final Safety Analysis Report. Radiation release by

this path is not possible as long as the control rod drive pumps are kept

running. However, continued operation of these pumps following an accident

cannot be ensured, particularly if the non-seismically qualified suction piping

were to fall.

This problem was resolved at Washington Nuclear Power Plant Unit 2 by the

installation of two check valves in series in the common discharge pipe from

the control rod drive pumps to prevent back flow out of the secondary contain- ment. The Washington Nuclear Power Plant Unit 2 installation includes provisions

for leak testing the valves. Washington Nuclear Power Plant Unit 2 planned to

establish a leak rate criterion for these valves of 0.01 gpm.

The control rod drive system for BWR/6 plants is designed with a testable

check valve and a motor-operated isolation valve, therefore this pathway is

applicable to only pre-BWR/6 plants.

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

you have any questions about the information in this notice, please contact the

technical contact listed below or the appropriate NRR project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Charles R. Nichols, NRR

(301) 492-0856 Donald C. Kirkpatrick, NRR

(301) 492-1849 Attachments:

1. Figure of Control Rod Hydraulic System

2. List of Recently Issued NRC Information Notices

Document Name: UNIDENTIFIED RELEASE PATH IN

  • SEE PREVIOUS CONCURRENCES

D/DOEA:NRR C/OGCB:DOEA:NRR

CERossi CHBerlinger

10/ /90 10/ /90

OGCB:DOEA:NRR SPLB:DST:NRR C/SPLB:DST:NRR D/DST:NRRK4 RPB:ADM

DCKirkpatrick* CRNichols* CMcCracken* AThadani TechEd*

08/17/90 08/20/90 09/24/90 10M /90 08/06/90

1990

Page 3 f 3 Combining the General Electric dose calculations for the postulated path with

at either Limerick or

the leak rates measured from the hydraulic units in excess of the values specified

Susquehanna produces dose rates significantly calculations by the NRC staff

in the Final Safety Analysis Report. Independent to the General Electric

produced offsite dose values that were comparable the values specified in the

results and that could also significantly exceed by this path is not possible

Final Safety Analysis Report. Radiation release running. However, continued

as long as the control rod drive pumps are kept cannot be assured, particularly

operation of these pumps following an accident were to fail.

if the non-seismically qualified suction piping

This problem was resolved at Washington Nuclear Power Plant Unit 2 by the

installation of two check valves in series in the common discharge pipe from

the control rod drive pumps (at area A) to prevent backflow out of the reactor

building secondary containment. The Washington Nuclear Power Plant Unit 2 and a leak rate

installation includes provisions for leak testing the valves

criterion of 0.01 gpm was established for these valves.

or written response. If

This information notice requires no specific action

in this notice, please contact one

you have any questions about the information appropriate NRR project manager.

of the technical contacts listed below or the

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Charles R. Nichols, NRR

(301) 492-0854 Donald C. Kirkpatrick, NRR

(301) 492-1849 Attachments:

1. Figure 1. BWR Control Rod Drive System

2. List of Recently Issued NRC Information Notices

Document Name: RELEASE PATH NOTICE ok 1vko .

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

CERossi CHBerlinger

11/ /90 11/09/90

  • C/SPLB:DST:NRR *D/DST:NRR *RPB:ADM
  • OGCB:DOEA:NRR *SPLB:DST:NRR TechEd

DCKirkpatrick CRNichols CMcCracken AThadani

08/20/90 09/24/90 10/30/90 08/06/90

08/17/90

IN 90-XX

August xx, 1990 this path is not possible as long as the control rod drive pumps are kept

running. However, continued operation of these pumps following an accident

cannot be ensured, particularly if the non-seismically qualified suction piping

were to fail.

This problem was resolved at Washington Nuclear Power Plant Unit 2 by the

installation of two check valves in series in the common discharge pipe from

the control rod drive pumps to prevent back flow out of the secondary contain- ment. The Washington Nuclear Power Plant Unit 2 installation includes provisions

for leak testing the valves. Washington Nuclear Power Plant Unit 2 planned to

establish a leak rate criterion for these valves of 0.01 gpm.

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

you have any questions about the information in this notice, please contact the

technical contact listed below or the appropriate NRR project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Charles R. Nichols, NRR

(301) 492-0856 Donald C. Kirkpatrick, NRR

(301) 492-1849 Attachments:

1. Figure of Control Rod Hydraulic System

2. List of Recently Issued NRC Information Notices

Document Name: UNIDENTIFIED RELEASE PATH IN

  • SEE PREVIOUS CONCURRENCES

D/DOEA:NRR C/OGCB:DOEA:NRR

CERossi CHBerlinger

08/ /90 08/ /90

OGCB:W EA:NRR SPLB:DST:NRR CISPLB:DST:NRR D/DST:NRR *RPB:ADM

DOrirkpathick CRNichols CMcCracken AThadani TechEd

08/e 9/90VC< 08AV2/9M;*^ OF/p/90 408/ /90 08/06/90

V1

IN 90-XX

August xx, 1990 The Washington Nuclear power installation includes provisions for leak testing

the valves. Washington Nuclear Power has established a very low leak rate

criterion for these valves (.01 gpm was indicated). A partial check by the NRC

staff indicates that many of the newer BWR plants already have check valves

installed in the control rod drive pump discharge pipe. However, this check

also showed that other BWR plants, mainly the earlier ones, did not have such

check valves.

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

you have any questions about the information in this notice, please contact the

technical contact listed below or the appropriate NRR project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contact:

Charles R. Nichols, NRR

(301) 492-0854 Attachments:

1. Figure of Control Rod Hydraulic System

2. List of Recently Issued NRC Information Notices

Document Name: UNIDENTIFIED RELEASE PATH IN

D/DOEA:NRR C/OGCB:DOEA:NRR

CERossi CHBerlinger

08/ /90 08/ /90

OGCB:DOEA:NRR SPLB:DST:NRR C/SPLB:DST:NRR D/DST:NRR RPB:ADM

DCKirkpatyi .-CRNichols CMcCracken AThadani TechEd J ai P

08/' /9 xF 08/ /go 08/ /90 08/ /90 08/C /90


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