ML20005F009
| ML20005F009 | |
| Person / Time | |
|---|---|
| Issue date: | 01/03/1990 |
| From: | Thadani A Office of Nuclear Reactor Regulation |
| To: | Marion A NUCLEAR ENERGY INSTITUTE (FORMERLY NUCLEAR MGMT & |
| References | |
| NUDOCS 9001120175 | |
| Download: ML20005F009 (2) | |
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JM 3 1990 Mr. Alex Marion Manager Technical Division-Nuclear._ Management and Resources Council (NUMARC)
-1776 Eye. Street,'N.W., Suite 300 Washington..D.C. 20006-2496
Dear Mr. Marion,
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Your letter of December 28,l1989(Enclosure).-transmittedthefollowingsupple.
mental guidance docunents for-addressing the station blackout issue:
P 1.
NUMARC 87-00 Supplemental Questions / Answers, dated December 27, 1989.
2.
NUMARC 87-00 Major Assumptions, dated December 27, 1989.
We'have reviewed these documents and conclude that they accurately reflect the resolution of all the remaining supplemental guidance issues as discussed in.
the publicly-noticed meeting of December 27, 1989.- Therefore, these documents -
will provide acceptable clarification to the previously approved guidance for addressing the station blackout issue.
As discussed in all our meetings on supplemental guidance, in order to affect the resolution of the station blackout issue in accordance with the established program and with minimum impact on schedule, the NRC requires confirmation from licensees'that: (1)analyseswereconductedinaccordancewithestablished guidance..-(2)~ the results are accurately reflected-in the licensee resp (4) a
- onse, (3) technically sufficient supporting documentation is available, and f
reliability program has been or will be implemented to attain and maintain the targeted level of emergency diesel generator reliability. We expect that
- licensees will expeditiously review and. revise their response to the station blackout rule as necessary to provide-this confirmation.
j Sincerely,
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H t-Ashok C. Thadani, Director Division of Systems Technol_ogy.
L Office of Nuclear Reactor Regulation
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3 ENCLOSURE NUCLEAR MANAGEMENT AND RESOUeCES COUNCIL V
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December 28, 1989 Mr. Ashok C. Thadani Director of Systems-Technology Office of Nuclear Reactor Regulation U.. S.- Nuclear Regulatory Commission Washington, D. C.
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Dear Mr. Thadani:
e This letter transmits supplemental documents relating to clarifications in utility application of NUMARC 87-00, Guidelines and Technical L jes-for NUMARC Initiatives Addressina Station Blackout at Licht Water Re m.
- contains a series of questions and answers relating to portions of the NUMARC 87-00 document dealing with aspects of the coping analysis, AAC configurations and equipment operability.. Enclosure 2 lists and describes We believe i
major assumptions and bases contained in the NUMARC 87-00 document.
these enclosures address and clarify areas of misunderstanding and g
misapplication of the accepted: guidance as noted during the NRC Staff audits t
of seve_ral utility SB0 responses,
-These enclosures were reviewed and discussed with you and members of your staff at publicly noticed meetings held December 15 and 27,1989.
We consider Detailed comments from you and your staff have been. incorporated.
these enclosures to be final in that they reflect both the NRC We
. supplemental guidance for complying with the NRC station blackout rule views.
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request your concurrence in this position.
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each document, we request your confirmation of the following:
L NUMARC 87-00 Sucolemental Ouestions/ Answers, dated December 27, 1989 - That they serve as appropriate clarification to existing 1.
acceptable guidance for addressing the station blackout issue; and s
27, 1989 - That NUMARC 87-00 Maior Assumotions, dated December they serve as appropriate clarification to existing acceptable 2.
guidance for addressing the station blackout issue.
L We wish to provide the clarifying information contained in the enclosures It is important that we receive NRC to industry by January 5, 1990.
concurrence on the content prior to that date so that we can include your letter as part of that package. We appreciate your prompt attention.
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Ashok C. Thadani 1
December 28, 1989-j Page 2 We believe that the efforts undertaken by NUMARC, together with the attention that has been given to this matter by you and members of your staff, will address the concerns raised by the NRC and industry.
Sincerely, f
k& YY Alex Marion Manager, Technical Division am/
Enclosures:
NUMARC 87-00 Supplemental Questions / Answers, dated December 1.
27, 1989 2.
NUMARC 87-00 Major Assumptions, dated December 27, 1989 l
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NUMARC 87-00 SUPPLEMENTAL QUESTIONS / ANSWERS GENERAL QUESTIONS Q:
Are utilities reauired to apply the NUMARC 87-00 assumptions and 0.1
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methodology.to their station blackout calculations and supporting l
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 independently by the Staff.
It is recognized that utilities may have used alternative methodologies that conservatively bound those of NUMARC 87-00.
Virtually all-utilities utilized the approved generic response format The in providing to NRC information required under the station blackout rule.
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.
(if any) which. level of planning must be complete to support modi 0.2 Q:
What a licensee proposed in the' station blackout submittal?
A:
Licensees should have identified the nature and objectives of any
. modifications required to meet the station blackout rule and a proposed schedule for implementation. The implementation status of proposed modifications should conform to 10CFR50.63 Sections C(l)(iii), C(3) and C(4).
.SECTION 1:
INTRODUCTION 1.1 Q:
Is it necessary to perform further analyses to verify that baseline assumptions of NUMARC 87-00 are valid for each plant, or is an assumption a L
"given"?
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A:
Section 1.3 of NUMARC 87-00 suggests that utilities ensure baseline assumptions are applicable to their plants.
Per Question / Answer 3 from Responses to Questions Raised at the NUMARC 87-00 Seminars (October 1988),
" utilities are not expected to perform rigorous analyses or evaluations in verifying the assumptions of NUMARC 87-00."
However, the validity of I
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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GENERAL CRITERIA AND BASELINE ASSLMPTIONS SECTION 2:
2.5 Reactor Coolant Inventory Loss Must the assums) 25gpm reactor coolant pump seal leak rate be used 2.1 Q:
by all plants (BWR and P'4)?
It is acceptable to NRC to use 18gpm for BWR recirculation No '.
/.: Leakage rates lower than 25 gpm for PWRs or 18 gpm for BWRs may be used, provided a justification exists and the NRC is informed that lower-pumps.
L rates are being utilized.
s 2.7 Effects of loss Ventilation Is it necessary to provide reasonable assurance of equipment 2.2 Q:
operability in dominant areas of concern where temperatures are below 120F7 The need to establish reasonable assurance of equipment operability A:
Sag Section 2.7.1 of NUMARC 87-applies only to dominant areas of concern.A dominant area of concern (DAC) 00.
enaineerina.iudaement, areas containing station blackout response equipment have substantial heat generation terms and lack adequate heat removal systems due to the blackout. Sag NUMARC 87-00, p. 7-18.
If temperatures in the DAC are calculated to be equal to or less than
-120 degrees F, this establishes reasonable assurance of equipment operability If temperatures in the DAC are calculated to be without further analysis.
in excess of 120 degrees F, reasonable assurance of equipment operability NUMARC 87-00, Appendix F, and its accompanying topical must be provided.
report provide acceptable methods for assuring equipment operability.
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 If temperatures exceed 120F, reasonable assurance of exceed 120' degrees F.
NUMARC station blackout response equipment operability must then be provided.
87-00, Appendix F, and its accompanying topical report provide methods for assuring equipment operability.
In the control room, cabinet doors should be opened within 30 minutes of the onset of SB0 to provide adequate air mixing to maintain internal cabinet Refer to temperatures in equilibrium with the control room temperature.
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 from the Responses to Questions Raised at the NUMARC 87-00 Seminars (October, 1988).
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May masonry, sheet metal or gypsum walls be assumed as heat sinks
.3 Q:
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- in the NUMARC 87-00 room heat-up ca cu at ons?
. The NUMARC 87-00 methodology assumes poured concrete walls to be A:
Other wall materials are not addressed by the methodology.
the heat sink.
If other wall materials are used,- additional-calculations must be performed and the use of such calculations should be identified to the NRC.
May air volumes above drop ceilings, such as in the control room, 2.4.Q:
be used for calculation of room temperatures using the NUMARC 87-00 methodology?
Generally, no. - A continuous ceiling is assumed by the methodology A:
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 drop ceilings are used 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.
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2.5 Q:
What wall temperatures may be assumed when applying the NUMARC j
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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 wall, in this the inside, the average wall temperature should be used.
case, will not be as effective a heat sink as a wall uniformly at the inside l
L room temperature.
2.6 Q:
Are any restrictions placed on taking credit for opening doors to an outside room?
To allow credit for opening doors for cooling, the outside A:
Yes.
room should be cooler than'the room being analyzed and should be sufficiently large that hot air from the inside room will not appreciably alter the temperature of the outside room. Opening.the control room door to a closet or kitchen 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 87-00 Seminars (October, 1988) to ensure that the control room is not a DAC?
i A:
Yes.
For example, cabinet doors need not be opened where fans are powered during SB0 to provide forced ventilation of cabinets or if HVAC is provided during SBO.
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' REQUIRED COPING DURATION CARGQBY
' SECTION 3:
i 3.2. Part 10. Evaluatina Indecer.hr.ce of Off-site Power Systa f
How quickly must manual transfers be made, when evaluating the 3.1 Q:
independenceofoffsitepowersystems(IGroup)?
Any manual method of transferring power sources for all safe shutdown buses is acceptable aroviding the transfer can be accomplished in a reasonable A::
Thus, a manual transfer involving operation time, such as less tian one hour.of a disconnect link requiring several hours ti How independent must switchyards be for the purpose of I Group
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determinations?
A "no" answer to Criterion A, p. 3-11 of NUMARC' 87-00 requires that multiple switchyards must be physically and electrically independent.
A:
Electrical independence can be provided by normally open breakers. i.e., twoPh open breakers in series, between switchyards or busses.
would be satisfied.by two separate and distinct switchyards each bounded > by Supplying power to plant unit safety busses via, (1) a perimeter fence.
multiple voltage transformations occurring within a singic does nol satisfy the intent for physical switchyard independence.
L Where normal AC power is provided by the unit main generator and
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only one of two safe. shutdown buses is automatically or manually transferred 3.3 Q:
to preferred or alternate off-site sources, does that qualify as a transfer I-l of all safe shutdown buses?
El safe shutdown buses must be transferred per Criteria B(1) l A:
No.
l and B(2), p. 3-11, of NUMARC 87-00.
Detemine the Number of Necessary EAC Standby Power Systems t
3.2.2. Part 2.B When determining the number of EAC standby power sources necessary to operate safe shutdown equipment, what safe shutdown loads should be 3.4 Q:
considered?
A:
From NUMARC 87-00, p. 3-15:
The number of necessary EAC standby power sources should be determined by accounting for the individual safe shutdown loads or inferred from the site's design basis for operating L
Class 1E equipment without off-site power.
This determination does not need to take into consideration a simu Furthermore, any design basis event (other than loss of offsite power). variations (
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power loads should be identified in SB0 responses to NRC and. fully justified
- b with documentation available.
Additionally, the shutdown loads powered must be capable of maintaining
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~the_ plant'ir a safe condition for an extended period (i.e., longer than the requiredcopingduration).
Does safe shutdown mean cold shutdown?
3.5 -Q:
The plant should be brought to the desian basis safe shutdown A:
No.
condition, which may be hot standby, hot shutdown, or cold shutdown.
At a multi-unit site, if an EAC source is used as an AAC source, 3.6-Q:
should that EAC/AAC sourcc be excluded from the number of EAC standby power supplies used to determine the blacked-out unit's EAC Grosp?
An AAC source which is also an EAC source must be subtracted To A:-.Yes.
from the number of EAC sources available as EAC standby power supplies.
do otherwise would be double-counting as discussed in NUMARC 87-00, p. 3-14.
SECTION 4:
STATION BLACK 0lfT RESPONSE PROCEDURES 4.2.1 Station Blackout Response Guidelines Is it acceptable to dispatch an operator from the control room to the remote shutdown panel-for the purpose of providing power from the Appendix 4.1 Q:
R-diesel-or the safe shutdown facility?-
It is However, the control room should not be abandoned.
anticipated that recovery from a station blackout may require operator action A:
Yes.
l or monitoring from the control room.
SECTION 7:
COPING WITH A STATION BLACKOUT,EVENI When ensuring containment integrity, can ncrmally closed valves be 7.1. Q:d from consideration similar to valves normally locked closed during exclude operation per NUMARC 87-00, Section 7.2.5, Step 1 (1).
A normally closed valve may not be considered to be a normally A:
No.
locked closed valve unless some action is taken to prevent supplying power to motor operators.
Can the main control room be disabled and evacuated to reduce the battery loads when assessing battery capacity to support decay heat removal 7.2 Q:
during SB0?
The norral battery-backed plant monitoring and electrical A:
No.
integral part of the control room and are considered system controls are at 5
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.e h 500. Therefore, essential for successfully coping with and recovering from t e it. is unacceptable for a utility to disable and evacuate the control room N
for the purpose of reducing battery loads.
APPENDIX B:
ALTERNATE AC POWER CRITffd8 What single failure considerations are applicable at a multi-unit B.1 Q:
site where EAC sources are utilized for AAC7 When a Class IE emergency AC (EAC) source is used as an AAC sourco, a single failure is applied to one of the EAC power sources in the non blacked-A:
If the remaining EAC source meets the criteria of NUMARC out (NBO) unit.
87-00 Appendix B, AAC power is' assumed to be available to the blacked-out 8
unit.
Refer to NUMARC 87-00, p. 2-2 through 2-4.
What single failure considerations are applicable to SB0 AAC power B.2 Q:
systems?
Per Criterion B.8.e of NUMARC 87-00, the AAC power source must not L
be susceptible to a single point vulnerability whereby a likely weather-related A:
ovent or single active failure could disable any portion of the on-site emergency AC. power sources or the preferred (off-site) power sources, and Random failures other than the simultaneously fail the AAC power source.
type addressed by Criterion B.8.e are not contemplated and need not be considered. See also Question / Answer C.1, below.
What loads must be carried by an AAC source which is also an EAC B.3 -Q:
source?
A:
The AAC source must carry:
(1) the loss of off-site power safe shutdown loads on the non-blacked-out (NBO) unit as described in i,
Question / Answer 3.4, above and (2) the station blackout loads on theThe capac blacked-out unit for the required coping duration.
source of the NB0 unit to be credited as an AAC source for the blacked-ou unit can only be the excess capacity above the loss of off-site power loads Shedding of any loads sho'uld not-lead to degradation of of the NB0 unit.
Beyond the the NB0 unit's loss of off-site power safe shutdown capability.
duration of SBO, the NB0 unit should retain the capability to support its loss of off-site power safe shutdown loads.
Criterion B.9 of NUMARC 87-00 states, "The AAC power system shall be sized to carry the required shutdown loads for the required coping duration determined in Section 3.2.5, and be capable of maintaining voltage and frequency within limits consistent with established industry standards that At a will not degrade the performance of any shutdown systems or component.
multi-unit site, except for 1/2 Shared or 2/3 emergency AC power configurations, an adjacent unit's Class IE power source may be used as an AAC power source for the blacked-out unit if it is capable of powering the required loads at both units."
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It'is expected.that AAC sizing. determinations censider both steady state and dynamic loading effects.
APPENDIX C:
-SAMPLE AAC CONFIGURATIONS C.1 ' Q:'
Is it acceptable to connect the AAC source to the blacked out unit j
by a single cross-tie?
However, when the AAC source is one of the available Class lE EAC sources, the cross-tie must be able to supply power to the blacked-out A:
Yes.
unit from any EAC/AAC source.
A single cross-tie connected to either of two EAC sources Examole 1. Figures A and B, Attachment 1, show two.such cross-tie is accentable.
configurations, although acceptable configurations are not lim examples.
use of the second EAC_ source for AAC power.
Figure C, attached, illustrates a potentially unacceptable Examole 2.
single cross-tie connecting one EAC source to a-second EAC source, and then conne: ting the second EAC source to the blacked-out unit.
In Figure C, assume Unit 1 is the blacked-out unit. Thus, diesels 11 and 12 are not available, and either diesel 21 or 22 is assumed to fail per the The remaining diesel (21 or 22) may be designated as an EDG single failure.
However, a single AAC source provided Appendix B criteria are satisfied.
- active failurc of Bus 21 would violate Criterion B.8.e regardless of which EAC source (21 or 22) is the AAC source.
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December 27, 1989 ET 87-00 RW ASSLMPTIONS
-As stated in NUMARC 87-00 Section 1.3, it is important that utilities i
Chapter 2 verify that-baseline assumptions are applicable to their plants.of i
Many assumptions are verified in the course additional' assumptions, as well.
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
" utilities are not expected to perform rigorous Seminars (October 1988):
analyses or evaluations in verifying the assumptions of NUMARC 87-00."
i However, utilities are expected to evaluate the applicability of the assumptions to individual plants, and this evaluation should be documented and available for NRC review.
Listed below are major assumptions which in some cases have not been I-
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satisfactorily verified. Preceding each assumption is the number of the applicable NUMARC 87-00 section.
The event ends when AC power is restored to shutdown busses
'2.4.l(1)
.To support AC power restoration it will be necessary from any source.
This can be done either manually or electrically to close breakers.
For those utilities utilizing DC power, the ability to via DC power.
close breakers at the end of the blackout should be included in the The' first available power source can be an EDG; battery calculation.
therefore flashing of the EDG field should also'be included in the calculation.
Reactor coolant pump seal leakage is assumed not to exceed 25 2
2.5.2 It is recognized that BWRs do not have reactor coolant The NRC gpm per pump.
pumps; however recirculation pump leakage should be evaluated.
staff has indicated that 18 gpm is an acceptable assumed leakage rate BWRs/PWRs taking credit for lower le,akage L
for BWR recirculation pumps.
rates should have documentation to support use of the lower rates.
2.7 Less-of ventilation effects.
2.7.1 Temperatures resulting from loss of ventilation are LOCA/HELB transients dump enveloped by LOCA and HELB profiles.
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 SB0, containment fans and coolers may not be available. This assumption, therefore, should be verified.
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Control room temperature does not exceed 120F.
l 2.7.l(2) (a)
Utilities usually verify this assumption, but sometimes misapply l
See below.
the methodology of NUMARC 87-00, Section 7.2.4.
l Typical problems encountered with utility use of the methodology of Section 7.2.4 to calculate $80 temperatures in the control room and dominant areas of, concern are as follows:
Initial wall temperatures assumptions are not verified by actual 1) measurement; Wall temperatures for walls acting as heat sinks in air conditioned This is 2) rooms are assumed to be at the initial room temperature.
valid if the rooms on both sides of the wall are air conditioned
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If the outside wall temperature is hotter, to the same temperature.
1.e., not air conditioned, the average wall temperature, not the air conditioned room temperature, should be used; Where a continuous drop ceiling prevents free lassage of air out 3) of the dominant area of concern, air volumes a>ove can not be included in the analyzed room's free volume when using the NUMARC Other analyses can properly take credit for 87-00 methodology.
heat transfer across the ceiling tiles, and these additional analyses l
should be identified to NRC; Only poured concrete walls may be used as heat sinks, not cinder 4)
Other analyses can properly i
block or wa11 board (Section E.3.1)l materials, and these additional take credit for other types of wal i
analyses 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 (it.t Section E.3.3.) Opening a closet door, the room in question.
for example will not provide a significant heat sink and can not be credited.
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Loss of heating in the battery room is assumed not to 2.7.1(2) (b)
Provided battery capacity calculations used affect battery capacity.
the lowest electrolyto temperature anticipated under normal operating j
conditions, further consideration of loss of battery capacity is not required, per NUMARC 87 00, p.7-7.
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