ML20127D981
| ML20127D981 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 01/13/1993 |
| From: | Horn G NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NSD930061, TAC-M83768, NUDOCS 9301190114 | |
| Download: ML20127D981 (8) | |
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- u. m t NSD930061 January 13, 1993 U. S. Nuclear Regulatory Cormnission Attention:
Document Control Desk War.hington, D.C.
20555 Centlemen:
Subject:
Ret ponse to Request for Additional Information Related to Proposed Change No. 100 to the Cooper Nuclear Station Technical Specifications, "Ellinination of Main Stearn Line Radiation Monitor Scram and Isolation Functions," (TAC No.M83768)
Cooper Nuclear Station, NRC Docket 50 298, DPR-46
References:
1.
Letter froin 11.
Rood (NRC) to C.
R.
Horn (NPPD) dated Deceinber 1,1992, sarne subject 2.
Letter from G.
R.
Horn (NPPD) to NRC dated May 4,
- 1992,
" Proposed Change NO.
100 to Technical Specifications, Elimination of Main Stearn Line Radiation Monitor Scram and Isolation Functions, Cooper Nuclear Station, NRC Docket 50 298, DPR 46" 3.
Letter from A.
C. Thadani (NRC) to C. J.
Beck (BWROC) dated May 15, 1991, " Acceptance for Referencing of Licensing Topical Report NEDO-31400,
' Safety Evaluation for Eliminating the Boiling Water Reactor Main Steam Line Isolation Yalve Closure Function and Scram Function nf Main Steam Line Radiation Monitor'"
The Nebranka Public Power District (District) hereby provides its response to the NRC Staff's Request for Additional Information (RAI) (Reference 1) relating to the District's Proposed Change No. 100 (Reference 2) to the Cooper Nuclear Ste. tion (CNS) Technical Specifications. Proposed Change No.100 would remove the Technical Specifications associated with the Main Steam Line Radiation Monitor (MSijU() scram and Main Steam Line Isolation Valve (MSIV) isolation functions.
The District's proposed change is based, in part, on the results of a Boiling Water Reactors Owners' Croup (BWROC) effort, which performed an evaluation of the radiological consequences for the postulated Control Rod Drop Accident (CRDA),
assuming elimination of the MSLRM scram and MSIV isolation functions.
This evaluation is documented in Licensing Topical Report NED0-31400, " Safety Evaluation for Eliminating the Boiling Water Reactor Main Steam Isolation Valve Closure Function and Scram Function for the Main Steam Line Radiation Monitor,"
dated Msy 1987.
Following NRC review of this evaluation, the NRC Staff issued its evaluation documenting its acceptance for referencing the licensing topical report for use in license amendment applications (Reference 3).
The NRC's evaluation identified several conditions which licensees must meet to demonstrate the acceptability of referencing NEDO 31400 in license amendment 9bO139' Oil 4 930111
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U,'S. Nuclear Regulatory Commission January 13, 1993 Page 2 of 8 applications. As stated in the District's Proposed Change 100, the assumptions used in the evaluation documented by NEDO.31400 bound those used in the CNS CRDA i
analysis which form part of the CNS licensing basis. The NRC's RAI requests the District to compare the CNS licensing basis assumptions to those used in the NEDO 31400 analysis, and identify the procedural controls which will be in place to minimize occupational doses, and control environmental releases.
The following discussion provides the District's response to the NRC Staff's request for additional infortnation.
DE*iTIQ1L1 9
The Staff SE requires that "The applicant demonstrated that the assumptions with regard to input values (including power por assembly, Chi /Q, and decay times) that are made in the generic analysis bound those for the plant." Your response to this is the statement that "The District hus also evaluated the CRDA [ Control Rod Drop Accident) analysis for CNS and concludes that the assumptions used in NED041400 bound those used in the CNS CRDA accident analysis."
This statement asserts, but does not demonstrate, that the CNS assumptions are bounded by the generic analysis. To permit the staff to evaluate your compliance with this requirement, we request that you demonstrate that the CNS input values are bounded by the NEDO 31400 values by providing a list of the input values used in the analysis of CNS and those used in the NEDO 31400 analysis, and a discussion of any values for which the CNS value is not bounded by the NEDO.31400-analysis.
RESPONSE
As demonstrated in the table below, the District's CRDA analysis is bounded by the assumptions used in the NEDO.31400 evaluation.
The NEDO-31400 evaluation utilized the conservative radiological source term assumptions provided in the Standard Review Plan, Section 15.4.9, " Spectrum of Rod Drop Accidents (BWR). _"
CNS was licensed based on a General Electric analysis documented in APED 5756,
" Analytical Methods for Evaluating the Radiological Aspects of the General Electric Boiling Water Reactor," Harch 1969. The APED 5756 source term, although conservative, is significantly smaller than obtained using the source term assumptions provided in the Standard Review Plan; hence the NEDO 31400 analyses are more conservative than, and accordingly, bound the CNS licensing basis. A comparison of key input assumptions is provided in the table below.
ASSUMPflON NEDO 31400 CNS UCENSING BASIS SOURCE TERM
- 1) Numbor of Fallod Fuot 850 330 originalty for 7X7 fuoi adjusted to 850 for Rods 8XS fuel (CNS USAR p. XIV-6-7)
U.'S, Nuclear Regulatory Comrnission January 13, 1993 Pago 3 of 8 ASSUMPTION NEDO-31400 CNS LICENSING BASIS
- 2) Dasis for Fissbn Product Baed on provbus long-term oporation The reactor is assumed to have sporated at inventory at full pocer with no allowanco for dotagn power for 1000 days until 30 minutos docay pnor to initiation of the event tefore event.
- 3) Assunwd Power Levol of 1.5 tinsa cort, everage fuel rod power Nondnnity 1.3 timos everage fuel rod poww Failed Fuo' Rods (CNS USAR p. XIV 6-7)
- 4) Effectivo Rolosse Fractions 0.107 (nobios) 0.0190 (noblos) for Fallod Fuel Rods 0103 (40dinos) 0.0032 (halogons)1#
- 5) Power Loyol of Rods 012 MW/ rod The power level of the fuel rods assurved to Assuned to Fait fall are not addressed in the CNS USAR; however, baaod on the NEDO assumptions of oporallon 0105% of hconood core thormal power (2381 MWth), and a 1.5 peaking factor, the CNS power / rod with 648 assemblies of BXO design (Hmiting assombty design of 60 plus one water rod por assombly)is 0.11 MW/ rod.
c) Finalon Products 100% nobles released to coolant 100% nobles roloased to coolant Transported to Condonsor 10% lodinos rtdoased to coolant (90%
No platoout of lodinos assumod; lowever of lodinos reaching condonsor are -
sorno washout assurredM assumod to be removod duo to washout /platoout).
- 7) Roduction of Soutco Term NO NO Due to MSIV closure?
DOSE ASSESSMENT
These release fractions are based on and conservatively bound the results of moasutomont made in actual defective fuel experimonta. This ovaluaten is docunwnted in APED-5758,' Analytical Methods for Evaluating the Radblogical Aspocts of the Gerwral Electric Boiling Water Reactor," March,1969,
- 2. The assumptions concerning washout /platoout of lodines have llttic impact on the evaluation as the NEDO-31400 evaluation of a CROA without MSIV closure assumos negligible lodino release because of rotontion in the AOG charcoal beds.
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U. 'S, Nuc1 car Regulatory Conunission January 13, 1993 Page 4 of 8 ASSUMPTION NEDO-31400 CNS LICENSING BASIS
- 9) Otspors6on coeffc6nnt 2.6 x 10 e*c/m' (2. hour ground level)
< 5.3 x 10** soc /m'(240ur ground lovel) at 4
(Chl/0) at exclusion area boundary alto boundary
< 1.4 x 10 soc /m' (2-hour clovated roloaso) 3.0 x 10 coc/m' (2-hour cluvated at tillo boundary foloa90) at exclusion atos boundary (CNS SER p. 2-8)2'
- 10) 2-hout Dosce With MSIV 4.3 Rom thyroid 4
Ckasure 2 0 x 10 rom thytold 0.31 Rom whole-body 1.0 M 10"' Itan whole body (CNS USAR p, XIV 6-12 multiplied by two por GESTARi# p. U9-13)
- 11) Potcontage of 10 Cf R 100 5 7% of thyroid hnt!
u 1% thyroid guidohnos 6 2% of whole-body hmrt
<< 1% wholo body
- 12) Augmonted Off-Gas Kryptons - 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> trinimum Kiyptons - 44.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> System Hobio Gas Holdup Xenons - 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> trinimum for low Xenons - 37 days Tnnes inmpetsture AOG System (CNS USAR p. IX-5-0)
QUESTION 2 The Staff SE requires that "The applicant includes sufficient evidence (impicmented or proposed operating procedures, or equivalent comrnitments)_
to provide reasonabic assurance that increar.ed significant IcVels of radioactivity in the main steam lines will be controlled expeditiously to liinit both occupational dosen and environinental releases. " Your responne is the staternent that "The District commits to revise its procedures as necessary to ensure that adequate controls exist to provido prompt control:of significant. increased in Main Steam Line activity..."
In order to determine whether or not this requirement will be snet at CNS, we request that you provide a discussion of any procedure changes that you plan to inake in response to this requirement, and how the revised (or existing, if no changes are planned) procedures ensure that significant increases in Main Steam Line activity will be promptly controlled in the absence of automatic containment 3,
"Safoty Evaluarkin Dy the Daocto;sto of Uconsing U, S. Atonic Enorgy Contrisswn, in the Manor of Nebraska Pubhc Power Dmtrtct Cooper Nuclear Station, Nomaha County, Nobraska, Docket No.60-298," issued February 14,1973.
4.
"Gonoral Ekctric Standard Application for Reactor Fuel (Supplomont for United Statos), General Electilo Document No. NEDE-24011-P-A-10-US, dated March,1991,
U.'S Nuclear Regulatory Commission January 13, 1993 Page 5 of 8 isolation on high HSIM signal. Also, we request that you provide an evaluation of the time that it takes to isolate, and the occupational doses and environmental release with and without automatic isolation on a MSIM signal so that we inay review this aspect of the proposed change.
RESPONSE
CNS has two independent radiation monitoring systerns which provide prompt indication of increased reactor coolant activity. These include the Main Steam Line Radiation Monitoring (HSIM) and the Stearn Jet Air Ejector Off Can Radiation Monitor (Off cas Monitor). These two systeins each have a liigh alarm setpoint, as well as a liigh liigh trip setpoint. While Proposed Change No. 100 will remove the HSIM liigh liigh MSIV and reactor scram trip, a liigh liigh alarrn will be installed in its place. The Off Gas Monitor currently initiates an alarm at the liigh alarin setpoint, and an Off Gas System isolation at the liigh liigh_ setpointl these functions will be retained.
The MSiRM and the Of f Gas radiation monitor together provide the operators with prompt identification, via control room annunciation, of increased levels of reactor coolant activity, while the CN3 Station Procedures, discussed below, provide the necessary guidance to provide rapid response to indication of increased levels of activity in the reactor coolant.
These radiation monitoring systems and associated procedures provide rapid indication and response to increased reactor coolant activity levels and together minimize the radiological consequences associated with increases in reactor coolant activity.
As part of the design change implementing the physical plant changes associated with removing the MSiRM MSIV isolation and scram functions, the _Off Cas radiation monitor alarm (lligh) will be set at slightly greater than 1.5 times backgroundlU the MSIM alarm (lligh) will be retained at 1.5 times background.
While the District already has-in place procedures for controlling increased activity levels as identified at the MSIMs and the Off-Gas Radiation monitor,-
some revision to these procedures will be necessary to reflect the physical plant changes planned to be implemented and comrnitments made in the District's proposed Change 100. Although a number of station procedures collectively contribute to the process of controlling increased coolant -activity, the significant controlling procedures are discussed below.
The initial operator actions taken in response to the alarm conditions are outlinad in existing Annunciator Alarm Procedure 2.3.2.24, " Panel 9 41."
(The MSIM liigh Rad Trip which is now annunciated on Panel 9-5 2 will be removed and l
_a MSIM llich liigh alarm will be provided on panel-9 4-1 with the MSiM-liigh i
l 5.-
The District has. determined that setting the Off-Gas radiation monitor-at 1.5 times the normal background would create the potential for nuisanc_o l
alarms in the control. Room while performing weekly grab _ sampling and monthly source checks.
Therefore, the District will set - the alarm slightly higher-to provide additional margin to avoid unnecessary control room distractions.
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U. 'S. Nuclear Regulatory Comrnission January 13, 1993 Page 6 of 8 alarra) This procedure provides immediate operator actions and refers to several other existing procedures which provide more detailed guidance for investigatin5 the cause of the alarms, and taking appropriate actions to reduce activity, or shutdown the plant. Briefly, Annunciator Alarm Procedure 2.3.2.24 will identify the following immediate operator actions (asterish denotes revisions to procedure);
MSLRM Radiation Ilich Alarrn 1.
Verify alarm 2.*
Infor:n chernistry to sample the reactor coolant 3.
Reduce power as necessary to reduce radiation levelc 4.
Refer to Procedure 2.4.1.2, " Fuel Element Failure" Off-cas Radiation Monitor liigh Alarm 1.
Verify alarin 2.*
Inform chemistry to sample the reactor coolant 3.
Take necessary action to reduce off gas radiation level to below alarm setting 4.*
Refer to Procedure 2.4.7.1, "High Off Gas Activity or Abnormal Off Gas Flow" tiSiRM 111gh-111ch Alarm 1.*
Verify alarm 2.*
Reduce power as necessary to reduce radiation levels 3.*
Refer to Procedure 2.4.1.2 " Fuel Element Failure" Of f-Gas 111gh liigh Alarm (Off-Gas Timer Initiated) 1.
Reduce power to clear alarm 2.
Refer to Procedure 2,4.7.1, "lligh Off Ges Activity or Abnormal Of f Gas Flow" Abnormal' Procedure 2.4.1.2,
" Fuel Element Failure," directs operators to 1)' determine if an Emergency Action Level has.been reached, and 2) obtain frorn Reactor Engineering recommended actions in accordance with Nuclear. Performance Procedure 10.31
" Fuel Reliability," and provides detailed steps to assist-operators in determining the cause of the elevated main steam line activity and to trend key process parameters.
-_ Abnormal Procedure 2.4.7.1, "lligh Off Gas Activity or Abnormal Off-Gas. Flow,"-
directs operators to perform several actions to reduce snain steam line activity,
- and if the Off-Gas Systeto isolates from inain steam line high high radiation. to scram the reactor and isolate-the main steam lines.
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4' U. 'S. Nuclear Regulatory Commission January 13, 1993 Page 7 of 8 Nuclear Performance Procedure 10.31, " Fuel Reliability," provides guidance for.
determining the appropriate course of action based on increasing steps of Off Cas j
activity readings.
Based on the applicable activity level, actions include reduction of reactor power level /derate, and evaluation of reactor shutdown.
These and other supplementary station procedures with the identified revisions thereto will provide the necessary controls to promptly respond to increased activity levels in the main steam line.
l The time required to isolate the main steam lines will depend on the applicable conditions at the time.
In the event an Off Cas System isolation occurs, Proceduro 2.4.7.1, discussed above, directs operators to scram the reactor and isolato the MSIVs.
Therefore, following the 15 minute off Cas isolation timer delay, the MSIVs would be isolated within a matter of minutes.1' This procedure has been and will remain in place, and the Off-Cas timer setpoint is tied to CNS Technical Specification 3.21.C.6.a. which limits Air Ejector effluent rate to s 1 C1/sec. In addition, CNS Technical Specification 3.6.B " Coolant Chemistry,"
l provides additional limitations on coolant activity and specifies _ appropriate actions, up to and including plant shutdown.
The time required for this evolution is dependant upon the conditions prevailing.
-Howevor, as the i
procedural guidance, with the exceptions of the changes identified above has been and will remain in place, the occupational and radiological consequences of an event resulting in increased reactor coolant activity and without MS1V closure will not significantly differ from the same event with MSIV closure.
Since the District has shown, in the response to Question 1 above, that the NEDO-31400 analyses bound the CNS CRDA analysis, comparison of the environmental 1
doses for a CRDA with and without the HSIV isolation can be provided by utilizin5
~
Figures 2, 3, and 4 of NED0 31400 and the CNS Chi /Q values and Augmented off-Gas System Noble cas holdup times. Using thic means of comparison, the 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> doses for a CRDA -with MSIV elocurg is approximately 1 rem thyroid and 7 X 10~8 rem whole body, while the 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> doses for CRDA without MSIV closure is less than 2 X 10-8 rem whole body.I' Although this comparison is not entirely based.on the current CNS licensing basis analytical methods, the comparison is based on the NEDO 31400 evaluation which the which the NRC has already evaluated and accepted.
Based on the above discussion, the procedures already in place collectively with the-applicable supporting procedures and the planned revisions thereto provide' i
ample guidance for timely disposition and mitigation of increased - coolant activity levels.and will continue to ensure that expeditious actions will-be 4
e 6.
Fif teen minutes following a Steam Jet Air-Ejector Radiation Monitor-Hight High trip (Off Cas Timer initiated) the O!f Cas 30"ninute holdup. line will be isolated if the trip cannot be cleared.
7.
The dose for a CRDA without MS1V closure does not consider a separate thyroid dese, because it.is assumed that 100% of the iodines are held up in the charcoal beds.
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U.'S. Nuclear Regulatory Commission January 13, 1993 Page 8 of 8 t
taken to minirnize both occupational exposure and environrnental releases during periods when increased coolant activity is experienced, i
OUESTION 1 W
The staff SE requires that the MSIM and the offgas radiation rnonitor alarm setpoint be standardized at 1.5 tirnes the nc. inal full power nitrogen 16 background dose rate at the rnonitor locations, and trust the applicant cormnits to c
promptly sample the reactor coolant to determine possible contamination levels in the plant reactor coolant if the MSIM or offgas radiation rnonitors exceed their alarm setpoints. Your response to this requirement states that the MSLRM alarm setpoint will be retained at 1.5 times the nominal background, and commits to promptly sarnple the reactor coolant if this setpoint is excevded.
- However, you inake no mention of the offgas radiation monitor. We request that you explain how this aspect of requirement 3 is met at CNS.
RESPONSE
t As discussed in the response to Question 2 abovo, the Off. Gas Radiation Monitor 1
will be set at slightly greater than 1.5 times background to provent control room nuisance alarms during radiation monitor survei.ance testing. The District will a
revise CNS Annunciator Alarm Procedure 2.3.2.24, " Panel 9 4 1,"
as described above, to require reactor coolant sampling if this alarm actuates, i
Picase contact me if you have any questions on the above or require any additional information.
t Sin ere y, j
i G(R\\_.QW<a llorn Nuclear Power Group Manager 1
GRil/MJB 4
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NRC Regional Administrator Region IV
. Arlington, TX NRC Resident Inspector Cooper Nuclear Station
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