ML20205H875
| ML20205H875 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 10/25/1988 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20205H874 | List: |
| References | |
| TASK-2.K.3.05, TASK-TM GL-86-06, GL-86-6, NUDOCS 8810310197 | |
| Download: ML20205H875 (12) | |
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4 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR RECULATION RELATING TO IMPLEMENTATION OF THI ACTION ITEM II.K.3.5 "AUTOMATIC TRIP 0F REACTOR COOLANT PUf1PS"
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ARKANSAS POWER & LIGHT COMPANY ARKANSAS NUCLEAR ONE,,U, NIT,,2 T
00CKET f!0. 50-368 1.0 },UgtA,R,Y InGenericLetter86-06(Ref.1),wereportedthattheinformationprovidedby the CE Owners Group (CEOG) in support of alternative Reactor Coolant Pur:p (RCP) trip criteria was acceptable on a generic basis. The review noted that a number of considerations were assigned plant specific status. Accordingly, we requested that operating reactor licensees select and implenent an appro-priate RCP trip criterion based upon the CECG nethodology. This Safety Evalua-tion (SE) contains the staff's findings concerning this issue for Arkansas Power & Light Company's ANO-2.
Reference I required owners of CE Nuclear Stean Generating Systers to evaluate their plants with respect to RCP trip. The objectives was to detonstrate that their proposed RCP trip setpoints assure pump trip for small break LOCAs, and in addition to provide reasoriable assurance that RCPs are not tripped unnecessarily during non-LOCA events. A nurber of plant specific itenis were identified which were to be considered by applicants ar.d licensees, including the selected RCP trip parar,eter, instrumentation quality and redundancy, instrur.:entation uncertainty, possible adverse environments, calculational uncertainty, potential RCP and RCP associated problems, operator training, and operating procedures.
The licensee has addressed the Generic Letter (GL) 86-06 criteria ar.d we have reviewed this infornation with assistance from consultants at EG8G. We find the material submitted by the licensee to be acceptable and find that the licensee has satisfied the requirements in regard to TMI Action Item II.K 3.5.
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Tit! Action Plan Item II.K.3.5 of NUREG-0737 required all licensees to consider other solutions to the small-break loss-of-coolant-accident (LOCA) problems since tripping the reactor coolant pumps (RCPs) was not considered the ideal solution. Automatic trip of the RCPs in the case of a small-break LOCA was recommended until e better solution was found. A summary of both the industry i
programs and the ilRC programs concerning RCP trip is provided in Generic Letters83-10a through f, which are included in the llRC report, SECY-82-475 A
(Ref.2). SECY-82-475 also provided the NRC guidelines and criteria for the l
resolution of Tit! Action Iten II.K.3.5, "Automatic Trip of Reactor Coolant Pumps."
The CEOG proposes using a trip-two/ leave-two (T2/L2) strategy.
The T2/L2 trip strategy consists of tripping two RCPs, located in diametrically opposed I
coolant loops, very early in a transient on a low reactor coolant system (RCS)
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t pressure signal independent of the nature of the event. The ren.aining two i
RCPs are tripptd subsequently af ter trip setpoints indicating a LOCA are reached.
l The licensee addressed this issue in Reference 3, 4, and 5, which we have f
reviewed with the assistence of EC&G censultants. is the
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technical evaluatiun report (TER) prepared by EG8G. We have revieved their recccrendations and concur that tbc licensee's submittal n>cets the requiremcnt r
of Iten 11 K.3.5.3.0 4
r As discussed in detail in the TER, the licensee has satisfied the requiret'er.ts of GL 86-06. The staff finds that Arkansas Power & Light Co. has j
corplied with the requirements of Generic Letter 66-C6 and that they have.
therefere, c;et the requirenents in regard to inplen,entation of TMI Action Iter.
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II.K.3.5.
l These requirements include:
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Determination of RCP Trip Criteria 1
The first two RCPs are tripped if the pressurizer pressure falls below 1400 psia.
The last two RCPs are tripped if the RCS subccoling nargin falls below 30*F and the secondary system reactivity alarms do not actuate. This agrees with the approved CEOG guidelines and hence is acceptable.
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B.
Instrunentation Uncertaintics for Normal and Adverse Environments
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The licensee has denenstrated that the instrument uncertainties are
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conservatively bounded in the plant specific analyses. We conclude these uncertainties are acceptable.
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C.
Generic and Plant-Specific Analyses Uncertainties The licensee has demonstrated that the results of the CE0G generic analyses are conservative for At:0-2. Therefore, we consider these acceptable.
D.
Operator Training and Procedures The licensee has provided operator training and procedures, which are consistent with the Generic Letter 86-06 guidelines. We, thus conclude, these are acceptable.
4.0 00pCLUS!0tl Each of the points identified in Reference 1 has been satisfactorily addressed by the licensece. The staff finds the licensee treatment of RCP trip to be acceptable tod the licer:see has satisfied the requirenents of Tl:1 Action Iten II.K.3.5.
5.0 RE F E R Eli,C,E S 1.
F. J. Miraglia, UStiRC, letter to all applicants and lictnsees with CE designed fluclear Stearr Supply Systeris (except f*aine Yankee),
"Irplementation of TII Acticn Iten !!.K.3.5, Automatic Trip of Reactor Coolant Purps," Gentric Letter 86-06, May 29, 1986.
2.
U. J. Dircks, Executive Director for Operations, UStiRC, "Staff Resolution of the Reacter Coolant Purp Trip Issue," SECY-82-475, fiRC Accessicn f!ur ber 830603070, fioverrber 30, 1907, 3.
J. T. Enos, APil, ltr to F. J. Miraglia, i:RC, "Arkansas i:uclear One -
lirit 2, Docket !!o. 50-368, license f o. I:PF-6, Inplementatier, of Tit!
Action Iten II.K.3.5, Autcriatic Trip of Reactor Coolant Purps, Pesper,se 3
to Generic Letter 86-06." 2CAtt118608, ioverber 24, 1986.
4 D. R. Howard, AP&L, ltr to U. S. f:uclear Regulatcry Corrsission, Occurent Control Desk, "Arkansas i:uclear One - Unit 2, Occket flo. 50-368, License fio, flPF-6, Additional Infornation Response, RCP Trip Criteria (TAC i:o.
49676)," 2CAtiO68806, June 3, 1988.
5.
J. R. Marshall, AP&L, ltr to Director of I;uclear Peactor Regulation, f1RC, "Arkansas i:uclear One - Unit 2, Docket flo. 50-368, license flo f PF-6, Reactor Coolant Pump Trip - Generic Letter 83-10," 2CAft9489409, April 20, 1984 Principal contributor: S. Wu Dated:
ENCLOSURE 2
TECHNICAL EVALUATION REPORT CONFORMANCE TO GENERIC LETTER 86-06 IMPLEMENTATION OF NUREG-0737. TN! ACTION ITEM 11.K.3.5 ARKANSAS NUCLEAR ONE. UNIT 2 DOCKET NO. 50-368 i
1.
INTRODUCTION TMI Action Plan Item II.K.3.5 of NUREG-0737 requires all licensees to consider other solutions to small break loss-of-coolant accident (LOCA) problems because tripping the reactor coolant pumps (RCPs) was not considered to be the ideal solution. NRC report SECY-82-4751 sumarized the industry and NRC programs concerning RCP trip.
In Generic Letter 86-062 the staff accepted the Combustion Engineering owners Group (CEOG) trip-two/ leave-two staggered RCP trip strategy 3.4
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i The CEOG developed a trip-two/ leave-two (T2/L2) strategy as the basis for RCP trip. The T2/L2 strategy consists of tripping two RCPs, located in diametrically opposed coolant loops, early in a transient on a low reactor i
coolant system (RCS) pressure signal regardless of the nature of the event.
The remaining two RCPs are later tripped if setpoints indicating a LOCA are j
reached. The goal of the T2/L2 trip strategy is to trip all four RCPs in the case of a small break LOCA but to have two or more RCPs operating for l
non-LOCA events. These would include steam line breaks, steam generator l
tube ruptures, or an anticipated operational occurrence.
1 The CE0G reports addressed the selection of trip parameters, evaluation of LOCA and non-LOCA events, evaluation of NRC criteria, justification of l
manual RCP trip, and instrumentation capabilities. The generic information l,
presented by the CE0G, however, did not address plant specific concerns abput instrumentation uncertainties, potential RCP problems, and operator l
training and procedures. This information, specifically identified in 1
Generic Letter 86-06, was requested from each C-E licenses to enable the staff to tassess implementation of the RCP trip criterion..
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DISCUSSION Arkansas Power & Light's (Ap&L's) response to Generic Letter 86-06,Section IV, for Arkansas Nuclear One, Unit 2, (ANO-2) was provided in a letter dated November 24, 1986.5 AP&L's response to a NRC request for additional information was contained in Reference 6.
Additional information provided by AP&L in Reference 7 was also reviewed. These references were reviewed to verify ApAL provided the required information. This review found the licensee endorsed the CEOG reports and provided plant specific details, such as subcooling margin, emergency operating procedures, and instrument uncertainties. A sumary of Ap&L's response to Generic Letter (GL) 86-06 and EG&G Idaho's basis for acceptance is provided below.
2.1 GL 86-06. Item 1 - Reactor Coolant pump Trio Criteria The NRC requested the licensee to identify the instrumentation used to determine the RCp trip setpoints, including the degree of redundancy for each measurement needed for the criteria chosen.
Response for ANO-2:
The first two RCPs are tripped if the pressurizer pressure falls below 1400 psia. The last two.,RCPs are tripped if the.RCS subcooling margin falls below 300F and the secondary system reactivity alarms do not actuate.
RCS wide range pressure is available from four loops of instrumentation. This information is also used in the reactor protection system (RPS) and the engineered safety features actuation system (ESFAS) and is environmentally and zeismically qualified. RCS wide range pressure is also available from the safety parameter display system (SPDS). Secondary system reactivity can be determined due to high radiation alarms from the condenser offgas radiation monitor, two steam generator sample cooler radiation monitors, two main steam line radiation monitors, or two secondary radiation recorders.
In addition, steam generator sample reactivity is available on a more delayed basis.
Subcooled margin is available from the SPOS, the plant computer, and from the RCS pressure and temperature (in 2
conjunction with steam tables). The primary indication of subcooled margin, however, is two subcooled margin monitors. The subcooled margin monitors were installed to meet the requirements of NUREG-0737, Item !!.F.2, and are environmentally qualified.
EG&G Idaho evaluation:
The licensee identified the pump trip criterion and setpoints for ANO-2. The setpoints discussed above (the first two pumps are tripped at a primary pressure of 1400 psia and and the second two pumps are tripped if the subcooled margin drops below 300F and there is no secondary radiation alarm) are based on the CEOG analyses. The licensee also identified the instrumentation needed to implement the chosen pump trip criterion.
Adequate redundancy is available for this instrumentation. The response to item 1 is acceptable.
2.2 GL 86-06. Item 2 - Instrumentation and Environment The NRC requested the licensee to identify instrumentation uncertainties, adverse containment conditions, and the effects of localized f actors (such as fluid jots or pipe whips) on instrument reliability.
Response for ANO-2:
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For the small break LOCA analyses (0.1 to 0.02 ft2 breaks) where tripping the second set of pumps was required to prevent fuel clad temperatures from exceeding licensing limits, Ap&L noted that the criterion for tripoing the second set of pumps is reached in a maximum of 94 s.
In addition, the emergency operating procedures (EOPs) direct the operators to check the RCP trip criterion as one of the first steps after a reactor trip. Therefore, not only will the trip criterion be reached in a short period of time, but the need to trip the second set of pumps will be noticed by the operators in this short time period as well.
In this short time period, containment environmental conditions for this range of small breaks will be only slightly more adverse than normal. Thus, normal instrument uncertainties can be used in determining the setpoints for the RCP trip criterion.
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For the pressure measurement, an uncertainty of 156 psi was used based on a 1980 analysis by C-E.
Subcooling margin uncertainty varies with system pressure.
In CEN-268, it was noted that the low pressure setpoint for tripping the first set of pumps (assumed to be 1300 psia) and the subcooled margin setpoint were reached nearly simultaneously. At 1300 psia, the uncertainty in the subcooled margin is 180F.
AP&L's setpoints of 1400 psia to trip the first set of pumps and subcooled margin less than 300F for tripping the second two pumps considered these uncertainties. The pressure setpoint included a margin of 80 psi above the C-E recommended setpoint of 1320 psia for ANO-2.
T.', e subcooled margin setpoint of 300F included a margin of 120F above the 180F error identified by AP&L.
The pressure transmitters of interest are mounted on the outside of the secondary shield wall in containment. Thus, they are not in an area subject to pipe whip or fluid jets. The same pressure measurements are input to the subcooled margin monitors. Temperature input from the hot legs to the subcooling margin monitors comes from two channels in each of two hot legs.
The hot legs are sufficiently separated so that local conditions cannot affect the temperature measurements in both hot legs simultaneously.
EG&G Idaho evaluation:
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For the small breaks where tripping the second set of pumps is recuired i
to maintain fuel clad temperatures below licensing limits, the licensee demonstrated that the criterion for tripping the second set of pumps is reached quickly enough that containment conditions would not be significantly different from normal conditions. Therefore, normal uncertainties were used. This aeproach was reviewed and found acceptable.
The uncertainties identified, 156 psi for pressure and 180F for subcooled margin, were considered by the licensee in determining the setpoints used in ANO-2. The pressure setpoint for tripping the first set of pumps, 1400 psia, accommodates an uncertainty of 80 psi based on the recommended setpoint of 1320 psia for ANO-2 in CEN-268. The subcooled margin setpoint of 300F conservatively bounds the subcooled margin uncertainty of 180F, 4
The licensee also stated local conditions will not impact the measurements required to implement the T2/L2 strategy. Based on the information provided by the licensee, the response is considered acceptable for the temperature inputs to the subcooled margin monitor. For the pressure transmitters, the licensee stated the transmitters were outside the secondary shield wall where they would not be affected by fluid jets or pipe whip. However, the licensee's response did not consider the sensors, cables, and other components that may be required to connect the transmitters to the primary system nor were the secondary radiation monitors discussed. The licensee's response is still considered adequate because the use of redundant equipment (as indicated by having the pressure measurement meet the requirements of NUREG-0737, Item II.F.2, and having several ways of detecting secondary radiation) indicates that single failures of instrument hardware can be tolerated, regardless of the cause of failure.
Thus, the response to this item is considered acceptable.
2.3 GL 86-06, item 3 - Generic and plant Specific Analyses The NRC requested the licensee to identify uncercainties associated with the CEOG generic analyses and atypical plant specific features.
Response for ANO-2:
The lice,nsee referenced Section 3 of the CEOG report, CEN-268. This section described the models and assumptions used in the analyses and discussed the applicability of the analyses to the spectrum of C-E plants.
In response to the NRC request for information, the licensee noted that the core power for ANO-2 was 115 Wg higher than for the 2700 Wg reference plant. However, the ANO-2 high pressure safety injection (HPSI) capacity, low pressure safety injection capacity, and the safety injection tank pressure are higher than those used in the reference analysis.
In addition, the cutoff head for the ANO 2 HPSI pumps is higher than in the reference analysis. Therefore, the licensee concluded the reference plant analysis is conservative for ANO-2.
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EG&G Idaho evaluation:
Based on the information provided by AP&L, EG&G Idaho agrees the reference plant analysis should be conservative for ANO-2.
In additian, EG&G Idaho compared the maximum HPSI flows for ANO-2 and the 2700 MW t
reference plant. The value provided in Reference 6 for ANO-2 was approximately twice that used in the reference plant analysis as provided in Reference 4.
This indicates the conservative nature of the reference plant analysis.
With respect to the analysis performed by C-E to determine the recomended pressure setpoint for tripping the first two pumps. EG&G Idaho noted that a separate recommendation was made for ANO-2 in CEN-268.
Because' ANO-2 was the only plant is this group, EG&G Idaho concluded plant specific information for ANO-2 would have been used in the equation provided in Reference 4 to determine the recomended pressure setpoint for ANO-2.
Therefore, the pressure recomended would be directly applicable to ANO-2.
The response to Item 3 is considered acceptable.
2.4 GL 86-06. Item 4 - Operator procedures and Trainino The NRC requested the licensee to identify plant procedures that require RCP trip guidelines and describe the training and procedures that provide direction for use,of individual steam generators with and without operating RCPs.
Res,sonse for ANO-2:
E0P 2202.01 was identified as the only E0P requiring the use of RCP l
trip guidelines. This procedure is based on the current revision of the l
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ANO-2 Emergency Operating Procedure Technical Guidelines that was submitted as part of the Procedures Generation Package in response to NUREG-0737, l
Item 1.C.1.
In this E0P there are sections dealing with the following types I
of transients and accidents:
reactor trip, recovery actions for emergency reactivity control, recovery actions for degraded power, recovery actions for (station) blackout, recovery actions for overcooling (event), recovery t
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actions for MSIS (main steam isolation), recovery actior.s for S!AS (safety injection actuation), recovery actions for steam generator tube rupture within charging pump capacity, recovery actions for steam generator tube rupture greater than charging pump capacity, and actions for inadequate core cooling.
Operator training was also described in the Procedures Generation Package submitted to the NRC.
In Reference 6, AP&L stated that operator training on use of the E0P is included in both the initial licensing training and also as part of annual recualification training.
Detailed classroom lectures and plant simulator sessions are included in both phasws.
With respect to procedures and training of operators for use it w ngle i
steam generators witn and without operating R"Ps, AP&L stated in Referince o that use of individual steam generators with operating pumps is covered in the sections of the E0P dealing with operator response to a steam generator tube rupture and main steam isolation signal.
EG&G Idaho evaluation:
AP&L identified the procedure requiring use of the 1CP trip guidelines, E0P 2202.01, and identified the plant situations where E0P 2202.01 would be ured. AP&L also identified those sections in the E0P covering the use of single steam-generators.. Operator training was also discussed. The f.
response to this item is acceptable.
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3.
CONCLUStvN AP&L's responses for Arkansks Nuclear One, Unit 2, to Generic Letter 86-06 were reviewed. The information in ti,ese responses clarifies the plant specific implementation of the CEOG strategy for reactor coolant pump trip. The review found the submittal for Arkansas Nuclear One, Unit 2 meets the NRC position established in the review of the CE0G report.
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REFERENCES 1.
W. J. Dircks, NRC, "Staff Resolution of the Reactor Coolant Pump Trip Issue," SECY-82-475, November 30, 1982, 2.
F. J. Miraglia, NRC, 1tr to All Applicants and Licensees with CE Designed Nuclear Steam Supply Systems (Except Maine Yankee),
"!mslementation of TM! Action Item !!.K.3.5, Automatic Trip of Reactor Coolant Pumpt," Generic Letter 86-06, May 29, 1986.
3.
Justification of Trip-Two/ Leave-Two Reactor Coolant Pump Trio Stratecy Durino Transients, CEN-268, March 1984.
4.
Response to NRC Recuest for Additional information on CEN-268, CEN-268 Supplement 1-NP, November 1984.
5.
J. T. Enos, AP&L, 1tr to F. J. Miraglia, NRC, "Arkansas Nuclear One -
Unit 2. Docket No. 50-368, License No. NPF-6, Implementation of TM!
Action Item II.K.3.5, ' Automatic Trip of Reactor Coolant Pumps,'
Response to Generic Letter 86-06," 2CAN118608, November 24, 1986.
6.
D. R. Howard, AP&L, ltr to U. S. Nuclear Regulatory Commission, Document Control Desk, "Arkansas Nuclear One - Unit 2, Docket No. 50-368, License No. NPF-6, Additional Information Response, RCP Trip Criteria (TAC No. 49676)," 2CAN068806, June 3, 1988.
7.
J. R. Marshall, AP&L, ltr to Director of Nuclear Reactor Regulation, NRC, "Arkansas Nuclear One - Unit 2 Docket No. 50-368, License No.
NPF-6, Reactor Coolant Pump Trip - Generic Letter 83-10," 2CAN948409, April 20, 1984, t.
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