ML20011D558
| ML20011D558 | |
| Person / Time | |
|---|---|
| Issue date: | 12/22/1989 |
| From: | Tam P Office of Nuclear Reactor Regulation |
| To: | NRC OFFICE OF THE SECRETARY (SECY) |
| References | |
| TAC-40577, NUDOCS 8912270396 | |
| Download: ML20011D558 (10) | |
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'o UNITED STATES g
E NUCLEAR REGULATORY COMMISSION o-g
<t WASHINGTON, D. C. 20555 December 22, 1989 MEMORANDUM FOR : /PublicDocumentTRoomPersonnel??
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FROM :
Peter S. Tam, Senior Project Manager, Project Directorate T
I-4, Division of Reactor _ Projects I/II SUBJECT :-
REQUEST TO MAKE AN INFORMAL DOCUME.'!T PU3LICLY AVAILABLE
-- STATION BLACK 0UT NATTERS (TAC 40577)
We received on December 20, 1989 a telecopied document from NUMARC. The document consists o. two parts titled "NUMAP,C 87-00 Supplemental Questions /
Answers" and "NUMARC 87.00 Assumptions". We marked up the document with j
our_ comments and transmitted it _ back, wf thout a cover 1etter, to NUMARC.
' Enclosed is a copy of that document as marked up by the NRR staff. Please put it in the Public Document Room immediately.
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Pe r_ S. Tam, Senior Project Manager Project Directorate I-4 Division of Reactor Proie:ts I-II l
1 ec. F. Rosa J. Knight A. Gill
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e NUMARC 87-00 SUPPLEMENTAL QUESTIONS / ANSWERS l'
GENERAL OUESTIONS 0.1 Qr Are utilities reauirod to apply the NUMARC 87-00 assumptions and methodology to their station b"ackout calculations and supporting documentation?
A:
NUMARC 87-00 consists of guidance acceptable to the NRC for demonstrating compliance with the station blackout rule. Alternative methodologies may be used by utilities, but will be reviewed indeoendently by the Staff.
It is recognized that utilities may have used alternative Q N methodologies' that conservatively bound those of NUMARC 87-00.
Virtually all utilities utilized the approved generic response format in providing to NRC information required under the station blackout rule. The generic response contains a statement that.the utility used NUMARC 87-00 methodology and technical bases in preparing the submittal. Where this was not the case, it is important to identify and document the alternative methodology used.
If this has not been done, utilities should consider providing additional information to the NRC.
0.2 Q:
What level of planning must be complete to support modifications (if'any) which a licensee proposed in the station blackout submitt ?
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Licensees should have identifidc the nature ofvany modifications required to meet the station blackout-ruitfand a proposed schedule for implementation. The implementation status of proposed modifications should conform to ICCFR50.63 Sections C(1)(iii) C(3) and C(4).
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SECTION 1:
INTRODUCTION 1.1 Q:
Is it necessary to perform further analyses tn verify that baseline l.
assumptions of NUMARC 87-00 are valid for each plant, or is an assumotion a L
"given"?
A:
Section 1.3 of NUMARC 87-00 suggests that utilities ensure beseline assumptions are applicable to their plants. Per Question / Answer 3 from Responses to Questions Raised at the NUMARC 87-00 Seminars (NUMARC 87-00
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October 1988),"utilitiesarenotexpectedtoperformrigorousanalysesor g" O N evaluations in verifying the assumptions of NUMARC 87-00." However, the validity of assumptions for each plant should be established and documented.
A list of major assumptions among those to be verified has been provided to utilities by NUMARC.
Each assumption on the list should be reviewed to assure applicability to individual plants.
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RECTION 2:
SENERAL CkITERIA AND mAMLINE AstlttPTions 2.5 Reneter Coolant Inventory Loss 2.1 Q: Must the assumed 25gpm reactor coolant pump seal leak rate be used by all plants (BWR and PWR)?
A:
No.
It is acceptable to NRC to use 18gpm for BWR recirculetion Leakage rates lower than 25 gpm for PWRs or 18 gpm for BWRs may be pumps.
g bv used, provided a justification exists and the NRC is informed that lower rates are being utilized.
2.7 Effects of Laan VentilatiGD 2.2' Q:
Is it necessary to provide reasonable assurance of equipment E
i operabil_ity in dominant areas of concern where temperatures are below 120F?
i The need to establish reasonable assurance of equipment operability A:
applies only to dominant areas of concern. ing Section 2.7.1 of NUMARC 87-I Adominantareaofconcern(DAC)existswhen,basedondocumented 00.
arcineerina iudaement. areas containing station blackout response equipment hve substantial heat generation tems and lack adequate heat removal systems due to the blackout. Egg NUMARC 87-00, p. 7-18.
' If temperatures in the DAC are calculated to be equal to or less than i
L 120 degrees F, this establishes reasonable assurance of equipment operability without further analysis.
If temperatures in the DAC are calculated to be in excess of 120 degrees F, reasonable assurance of equipment operasility NUMARC 87-00, Appendix F, and its accompanying topical must.be provided.
report provide acceptable methods for assuring equipment operability.
I For the control room, even though it may not meet the DAC criteria, a heat-up analysis should be documented to demonstrate that temperatures do not exceed 120 degrees F.
If temperatures exceed 120F, reasonable assurance of station blackout response equipment operability must then be provided. NUMARC 87 00, Appendix F, and its accompanying topical report provide methods for l((
assuring equipment operability.
In the control room, cabinet doors should be opened within 30 minutes l
of the onset of SB0 to pnwide adequate air mixing to maintain internal cabinet Refer to temperatures in equilibrium with the control room temperature.
L NUMARC 87-00, Section 2.7.1, p. 2-9 and 2-10.
For additional information, refer to Question / Answer Nos. 4, 6, and 82 67-00 56minars (NUMARC, from the Responses to Questions Raised at the NUMARC L'
October,1988).
2.3 Q:
May masonry, sheet metal or gypsum walls be assumed as heat sinks
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The NUMAT.C 87-00 methodology assumes poured concrete walls to be
() b; the heat sinL -Other wall materials are not addressed by the methodology.
If other wall materials are used, additional calculations must be performed and the use of such calculations should be identified to the NRC.
2.4 Q:
May air volumes above drop ceilings, such as in the control room, be used for calculation of room temperatures using the NUMARC 87-00 methodology?
A:
Generally, no. A continuous ceiling is assumed by the methodology to inhibit any heat transfer to the volume above unless ceiling tiles are removed, by procedure, at the start of the blackout. If air volumes above g p^
drop ceilings are ured and ceiling tiles are not removed by procedure, additional heat transfer calculations would be necessary and the basis of such calculations should be identified to the NRC.
2.5 Q:
What wall temperatures may be assumed when applying *.he NUMARC 87-00 methodology to poured concrete walls acting as heat sinks in air conditioned rooms?
A:
'If the room on the outside of the wall is warmer than the room on the inside, the average wall temperature should be used. The wall, in this
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dese, will not be as effective a heat sink as a wall uniformly at the inside h.
room temparature.
2.6 Q:
Are any restrictions placed on taking credit for opening doors to j
sn out5ide room?
A:
Yes. To allow credit for opening doors for cooling, the outside room should be cooler than the room being analyzed and should be sufficiently n
large that hot air from the inside room will not appreciably alter the Opening the control room door to a closet v
temaerature of the outside room.
Oh or-(itchen for example will not provide a sufficient heat sink and should not be credited. Furthermore, blackout response procedures-should identify the doors to be opened.
Are there circumstances where cabinet doors need not be opened as 2.7 Q:
provided in Question / Answer No. 82 of Responses to Questions Raised at NUMARC l
87-00 Seminars (October,1988) to ensure that the control room is not a DAC?
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A:
Yes.
For example, cabinet doors need not be opened where fans are l
powered during SB0 to provide forced ventilation of cabinets or if HVAC is
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provided during SB0 t: emt2 tb ::r.tr:1 r:= hh; 200F.
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l SECTION_U REQUIRED COPING _DURATIDH CATECORY 3.2. Part 1D. Evaluatino Indeoendence of Off-site Power Svstem 3.1 Q:
How quickly must manual transfers be made, when evaluating the
.independenceofoffsitepowercystems(IGroup)?
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Any manual method of transferring power sources for all safe shutdown buses is acceptable >roviding the transfer can be accomplished in a reasonable C,k.
time, such as less tun one hour.. Thus, a manual transfer involving operation of a disconnect link requiring several hours to complete is not acceptable.
3.2 Q:
How independent must switchyards be for the purpose of I Group determinations?
A:
A 'no" answer to Criterion A, p. 3-11 of NUMARC 87-00 requires tnat multiple switchyards must be physically and electrically independent.
Electrical independence can be provided by normally open breakers, i.e., two open breakers in series, between switchyards or busses.
Physical independence O k would be satisfied by two separate and distinct switchyards each bounded by multiple voltage transformations occurring within a single switchyard (area, a perimeter fence. Supplying power to plant unit safety busses via, 1) or (2) via designated switchyard busses originating from a single switchyard, does not satisfy the intent for physical switchyard indepandence.
3.3 Q:
Where normal AC power is provided by the unit main generator and only one of two safe shutdown buses is automatically or manually transferred to preferred or alternate off-site sources, does that qualify as a transfer f
of all safe shutdown buses?
i A:
No. AllsafeshutdownbusesmustbetransferredperCriteriaB(1) and,B(2).p.-3-11,ofNUMARC87-00.
l 3.2.2. Part f.B Determine __the N W r of Necessary EAC Standby Power Systems 3.4 Q:
When determining the number of EAC standby power sources necessary to operate safe shutdown equipment, what safe shutdown loads should be consicered?
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From NUMARC 87-00, p. 3-15:
The number of necessary EAC standby power sources should be r
determined by accounting for the individual safe shutdown 4 g loads or inferred from the site's design basis for operating i
Class IE equipment without off-site power.
However, if the safe shutdown loads selected for operating Class IE equipment during a LOOP event are different from the design basis safe shutdowp loads, the utility must determine that the shutdown loads powered are capable /
of maintaining the plant in a safe condition for an extended period (i.e.,
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er than the coping duration).
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.4 3.5 Q:
Does safe shutdown mean cold shutdown?
DA A:
No. The plant should be brought to the desien basis safe shutdown condition, which may be hot standby, hot shutdown, or cold shutdown.
Q:
At a multi-unit site, if an EAC source is used as an AAC source, 3.6 should that EAC/AAC source be excluded from the number of EAC standby power supplies used to determine the blacked-out unit's EAC Group?
A:
Yes. An AAC source which is also an EAC source must be subtracted
' A from the number of EAC sources available as EAC standby power supplies.
To do otherwise would be double-counting as discussed in NU4 ARC 87-00, p. 3-14.
SECTION 4:
STATION BLACKni_fT RESP 0NEF PROCEDURES 4.t.1 Station Blackout Resnonse Cufdelines 4.1 Q:
Is it acceptable to dispatch an operator from the control room to the remote shutdown panei for the put ose of providing power from the Appendix R diesel or the safe shutdown facilit ?
A:
Yes. However, the control room should not be abandoned.
It is
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SECTION 7:
COPING WITH A STATION BLACK 0UT EVENT 7.1 Q:
When ensuring containment integrity, can normally closed valves be excluded from consideration similar to valves normally lected closed duri':g operationperNUMARC87-00,Section7.2.5, Step 1(1).
A:
No. A normally closed valve may not be considered to be a normally locked closed vsive unless some action is taken to prevent valve operaticr.,
j, Such actions would include removing control power fuses or racking out breakers C r(
supplying power to motor operators.
7.2 Q:
Can the main control room be disabled and evacuated to reduce the battery loads when assessing battery capacity to support decay heat removal during SB07 i
A:
No. The plant monitoring and electrical system controls'are an
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integral part of the control room and are considered essential for successfully Therefore, it is unacceptable for
) j coping with and-recovering from the SBO.;lrol room for the purpose of_miuc.ing gr a utilit to disable and av he ce
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APPENDfX B:
ALTERNATE AC POWER CRITERIA What single failure considerations are applicable at a multi-unit B.1 0:
site where EAC sources are utilized for AAC7 When a Class IE emergency AC (EAC) source is used as an AAC source, a single failure is applied to one of the EAC power sources in the non-black A:
If the remaining EAC source meets the criteria of NUMARC 87-00 Appendix B, AAC power is assumed to be available to the blacked out unit.
out unit.
Refer to NUMARC 87-00, p. 2-2 through 2-4.
ortant that utilities verify that baseline assumptions are applicable to t1eir plants. Chapter 2 of NUMARC B7-00 discusses baseline assumptions; however, other chapters include additional assumptions, as weil. Many assumptions are verified in the course of performing the various coping calculations, but some assumptions require specific verification.
The rigor to be applied by licensees in verifying assumptions is stated in Question / Answer 3 of Responses to Questions Raised at the NUMARC 87-00 Seminars (October 1988): " utilities are not expected to perform rigorous analyses or evaluations in veri,fying the assumptions of NUMARC 87 00."...
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Ever"ut51IEies'are exp5cieU5"eviluate Ue'appiieAilit[of the i
assumptions to individual plants and this evaluation should be documented and available for NRC review.
Listed below are ma.ior assumptions which in some cases have not been l
satisfactorily verified. Preceding each assumption is the number of the applicable NUMARC 87-00 section.
i 2.4.1(1) The' event ends when AC power is restored to shutdown busses
-l from any source. To support AC power restoratien it will be necessary to close breakers. This can be done either manually or electrically O V via DC power.
For those utilities utilizing DC power, the ability to A
close breakers at the and of the blackout should be included in the battery calculation. The first available power source can be an EDG; therefore flashing of the EDG field should also be included in the calculation, j
2.5.2 Reactor coolant pump seal leakage is assumed not to exceed 25 It is recognized that BWRs do not have reactor coolant gpm per pump.
pumps; however recirculation pump leakage should be evaluated. The NRC pJ y staff has indicated that 18 gpm is an accestable assumed leakage rate x
for BWR recirculation pumps. BWRs/PWRs ta<ing credit for lower leakage rates should have documentation to support use of the low 6r rates.
2.7 Loss of ventilation effects.
2.7.1 Temperatures resulting from loss of ventilation are enveloped by LOCA and HELB profiles.
LOCA/hELBtransientsdump large amounts of energy into a containment in a short time, thus, this assumption may seem intuitive. However, LOCA/HELB analyses assume fans and coolers are operating. During SBO, containment fans
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'and coolers may not be available. This assumption, therefore, should be verified.
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4 2.7.1(2) (a)
Control room temperature does not exceed:120F.
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Utilities usually verify this assumption, but sometimes misapply the methodology of NUl%RC 87-00, Section 7.2.4.
See below.
Typical problems encountered with utility use of the methodology of Section 7.2.4 to calculate SB0 temperatures in the control room and dominant areas of concern are as follows:
6 K-1)
Initial wall temperatures assumptions are not verified by actual measurement;
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Wall temperatures for walls acting as heat sinks in air conditioned rooms are assumed to be at the initial room temperature.
This is l
valid if the rooms on both sides of the wall are air conditioned to the same temperature.
If the outside wall temperature is hotter, L
1.e., not air conditioned, the average wall temperature, not the l-air conditioned room temperature, should be used; I
3)
Where a continuous drop ceiling prevents free passage of air out of the dominant area of concern, air volumes above can not be 0 K, included in the analyzed room's free volume when using the NUMARC L
87-00 methodology. Other analyses can properly take credit for c
heat transfer across the ceiling tiles, and these additional analyses should be identified to NRC; 4)
Only poured concrete walls may be used as heat sinks, not cinder l
block or wa11 board (Section E.3.1).
Other analyses can properly
_ U p-take credit for other types of wall materials, and these additional ansilyses should be identified to NRC; In order to take credit for opening doors to an adjacent room, the 5) adjacent room must be large and at a lower temperature relative to the room in question.
(Sag Section E.3.3.)
Opening a closet door, ry' for example will not provide a significant heat sink and can not be credited.
2.7.1(2) (b)
Loss of heating in the battery room is assumed not to affect battery capacity. Provided battery capacity calculations used the lowest electrolyte temperature anticipated under normal operating C((
conditions, further consideration of loss of battery capacity is not required, per NUMARC 87-00, p.7-7.
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