ML20012E903
| ML20012E903 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 03/28/1990 |
| From: | Devincentis J YANKEE ATOMIC ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BYR-90-039, BYR-90-39, NUDOCS 9004090043 | |
| Download: ML20012E903 (16) | |
Text
lYANKEEATOMCELECTMC COMPANY
- y*"',@?l@,'l" i
580 Main Street, Bolton, Massachusetts 017401398 wm w e-t
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Harch 28, 1990 i
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BYR 90-039 f
United States Nuclear Regulatory Commission t
Document Control Desk Washington, DC 20555 References (a) License No. DPR-3 (Docket No. 50-29)
(b) 10CFR50.63, " Loss of All Alternating Current Power" i
(c) YAEC Letter, BYR 89-70, to NRC, dated April 13, 1989 i
(d) NUMARC Letter N90-005, to NUMARC Board of Directors, j
dated January 4, 1990
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Subject:
Response to Station Blackout Rule 10CrR50.63 - Supplement 1 i
Dear Sirt i
On July 21, 1988, the Nuclear Regulatory Commission (NRC) amended its l
regulations in 10CFR, Part 50. A new section, 50.63, was added which requires that each light water-cooled nuclear power plant be able to withstand and
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recover f rom a Station Blackeut (SBO) of a specified duration.
Utilities are r
expected to have the base line assumptions, anslyses, and related information i
used in their coping evaluation available for NRC rev'ew, It also identifies the factors that must be considered in specifying the SB0 duration.
i Section 50.63 requires that, for the SB0 duration, the plant be capable of maintaining core cooling and appropriate containment integrity.
Section 50.63 further requires that each licensee submit the following informations 1.
A proposed SB0 duration, including a justification for the selection i
based on the redundancy and reliability of the on-site emergency ac power sources, the expected frequency of loss of off-site power, and the probable time needed to restore off-site povert 2.
A description of the procedures that will be implemented for SB0 s
events for the duration (as determined in Item 1 above) and for recovery therefromt and 3.
A list and proposed schedule for any needed modifications to 1
equipment and associated procedures necessary for the specified SB0
- duration, i
i The NRC has issued Regulatory Guide 1.155, " Station Blackout," which describes a means acceptable to the NRC staff for meeting the requirements for 10CFR50.63.
Regulatory Culde 1.155 states that the NRC staff has determined that NUMARC 87-00 " Guidelines and Technical Bases for NUMARC Initiatives i
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a 00mited States Nuclear Regulatory Commission March 28, 1990 Attention: Document Control Desk Page 2 l
Addressing Station Blackout at 1,ight Water Reactors," also provides guidance that is, in large part, identical to the Regulatory Guide 1.155 guidance and r
f-is acceptable to the NRC staff for meeting these requirements.
i i
Table 1 to Regulatory Guide 1.155 provides a cross-reference between L
Regulatory Guide 1.155 and NUMARC 87-00 and notes where the regulatory guide takes precedence.
Yankee evaluated the Yankee Nuclear Power Station (YNPS) against the requirements of the SB0 rule using guidance from NUMARC 87-00 except where L
Regulatory Guide 1.155 takes precedence. The results of this evaluation were j
transmitted to the NRC in Reference (c).
t i
By letter dated January 4, 1990, NUMARC provided an update of activities l
to address NRC concerns regarding utility SB0 Rule responses and implementation of guidance contained in NUMARC 87-00. These concerns are
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presented in two attachments to the NUMARC letter.
NUMARC requested that each utility review their responses to the SB0 Rule,10CTR50.63, and supporting documentation in light of these concerns and i
verify thatt
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t 1.
Implementation is consistent with the supplemental guidance provided I
by the attachments.
t 2.
Applicability of NUMARC 87-00 assumptions is documented in utility L
files.
i 3.
Departures from the accepted NUMARC 87-00 methodology are identified.
4 Diesel Generator target reliability is being maintained.
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Yankee has conducted a review of the YNPS SB0 analysis, supporting doctunentation, and NRC submittal in light of the above issues identified by
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i As a result of this recent review we have concluded thatt
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i 1.
Our previous submittal was prepared based on the use of the p
NUMARC 87-00 guidance and the applicability of NUMARC 87-00 l
assumptions is documented in our files.
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t 2.
Any deviations from the NUMARC 87-00 guidance have been clearly
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identified in this supplemental submittal.
, provides a dis;ussion of the applicability of each issue presented in the NUMARC letter and attachments to the YNPS SB0 analysis.
You will note that we have revised our loss of ventilation calculations to reflect the clarifications in Reference (d). No additional " dominant areas of I
concern" were identified as a result of the calculation revisions.
i In addition, as requested by Reference (d), Yankee confirms that the diesel generator target reliability of.975 as identifled in Reference (c) shall be maintained.
I f
,pt~
. United States Nuclear Regulatory Commission March 28. 1990 Attentient Document Control Desk Page 3 We trust this information is satisfactoryt however, if you have any questions, please contact us.
Sincerely.
YANKEE ATOMIC E1.ECTRIC COMPANY f f. Yoda
J. DeVincentis Vice President
.I JD/gj t /h'PP79/16 Enclosure i
L C0ft90Nh'EALTH OF MASSACHUSETTS) l
)ss i.
WORCESTER COUNTY
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Then personally appeared before me J. DeVincentis, who, being duly sworn, did state that he is a Vice President of Yankee Atomic Electric Company, that he is duly authorised to execute and file the foregoing document in the name and on the behalf of Yankee Atomic Electric Company and that the statements therein are true to the best of his knowledge and belief.
AsA t v r -n tn t.LA)
Helen D. Sasunarco Notary Public My Commission Expires November 7, 1991 0
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N ENCLOSgtF 1
- 1.._)UMARC_87-00 Supplemental Questlon/ Answer i
i
$tetton 0 - General i
The supplemental questions and an6vera on this section address documentation, f
verification, and use of NUMARC 87-00 assumptions and methodologies and i
recommend that all departures f rom these methodologies be clearly identified l
to the NRC.
i The YNPS SD0 analysis has been perforned and documented in accordance with the assumptions and methodologies in NUMARC 87-00. Additional heat transfer,
calculations have also been perforned consistent with the guidance in this i
attachment.
Section 1 - Introduction Each supplemental question and answer from this section is reproduced below l
followed by an applicability statement for YNPS.
1.1 Q:
Is it necessary to perform further analyses to verify that base line assumptions of NUMARC 87-00 are valid for each plant, or is an assumption a "given"?
At Section 1.3 of NUMARC 87-00 suggested that utilh ies ensure base line assuniptions are applicable to their plants. Per Question / Answer 3 from Responses to Questions Raised at the
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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
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validity of assumptions for each plant should be established and documented. A list of major assumptions among those to
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F be verified has been provided to utilities by NUMARC. Each t
assumption on the list should be reviewed to assure applicability to individual plants.
i YNPS Applicability 1
I I'
The applicability of each assumption is docunented in Section 2 of the YNPS SB0 analysis.
l Section 2: General Criteria and Base Line Assumptions f
2.5 Reactor Coolant Inventory Loss t
2.1 Q:
Must the assumed 25 gpm reactor coolant pump seal leak rate be used by all plants (BWR and PWR)?
l At No.
It is acceptable to NRC to use 18 gpm for BWR recirculation pumps.
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 rates are being
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utilized.
r s WFP79/16 I
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ENCICSVRE 1 (continued)
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YWPS Applicability As documented in Section 2 of the YNPS SB0 analysis, the YNPS i
reactor coolant pumps have no mechanical seals and, therefore, have no seal leakage.
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2.7 Effects of Loss Ventilatiou I
2.2 Q:
Is it necessary to provide reasonable assurance of equipment operability in (.ominant areas of concern where temperatures are below 120*Ff At The need to establish reasonable assurance of equipment operability applies only to dominant areas of concern.
Eeg Section 2.7.1 of NUMARC 87-00. A Dominant Area of Concern (DAC) exists when, based on documented engineerina judgment, creas containing SB0 response equipment have substantial heat generation terms and lack adequate heat removal systems due to the blackout. See NUMARC 87-00. P. 7-18.
If temperatures in the DAC are calculated to be equal to or less than 120'F, this establishes reasonable assurance of equipment operability without further analysis.
If temperatures in the DAC are calculated to be is excess of 120'F reasonable assurance of equipment operability must be provided. NUMARC 87-00, Appendix F, and its accompanying topical report provide acceptable methods for assuring equipment operability.
For the Control Room, even though it may not meet the DAC criteria, a heatup analysis should be documented to demonstrate that temperaturWh do not exceed 120'F.
If temperatures exceed 120'F reasonable assurance of SB0 response equipment operability must then be provided.
NUMARC 87-00. Appendix F and its accompanying topical report provide methods for assuring equipnent 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 temperatures in equilibrium with the Control Room temperature. Refer to NUMARC 87-00 Section 2.7.1, P. 2-9 and 2-10.
for additional inforamtion, refer to Question / Answer Nos. 4, 6 and 82 from the Responses to Questions Raised at the NUMARC 87-00 Seminars (October 1988).
~2-WPP79/16
ENC 146URE I (continued)
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YNPS Applicab_11(.ty l
1.
All areas containing SB0 equipnent have been evaluated f or f
loss of ventilation. With the exception of the Auxiliary i
Boiler Room (ABR) (LIN pump area), the maximum temperature l
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will be less than 120'F. NUMARC 87 00. Appendix F. has been utilised to demonstrate reasonable assurance of the turbine-driven ene.tgency f eed pump operability at the calculated ABR temperature.
Actual test data is available to demonstrate that the Control Room temperature will not exceed 120'F during the SB0 event.
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2.
The control Room ventilation fan will be started within one
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hour following initiation of the SB0 event.
3.
Control board doors are opened at the beginning of the SB0 event by plant procedures.
2.3 Q:
May Masonry, sheet metal, or gypsum walls be assumed as heat I
sinks in the NUMARC 87-00 room heatup calculations?
1 At The NUMARC 87-00 methodology assunes poured concrete walls to i
be the heat sink. Other wall materials are not addressed by the methodology.
If other wall materials are used.
I additional calculations must be performed and the use of such calculations should be identified to the NRC.
YNPS Applicability f
The initial YNPS loss of ventilation analysis credited the f
masonry walls as heat sinks using the NUMARC methods.
The l
area calculations have been revised to reflect this clarification.
2.4 Q:
May air volumes above drop ceilings, such as in the Control r
Room, be used for calculation of room temperatures using the NUMARC 87-00 methodology?
At 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 drop ceilings are used j
and ceiling tiles are not removed by procedure, additional t
i heat transfer calculations would be necessary and the basis of such calculations should be identified to the NRC.
I i
WPP79/16
F.NC1,0$t'RE !
(continued)
YWPS Applicability Actual area heatup test data have been used to verify that l
the Control Room temperature will temmin below 120'F during
$50.
t 2.5 Q:
What wall temperatures may be assuned when applying the NtMARC 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 I
room on the inside, the average wall temperature should be used. The wall, in this case, will not be as effective a heat sink as a wall uniformly at the inside room temperature.
YNPS Appilcability I
The Control Room is the only air conditioned area containing SB0 equipment.
Initial calculations used an aversge wall i
l temperature of 78'F.
This value has been revised using the j
average recorded temperature data.
2.6 Q:
Are any restrictions placed on taking credit for opening doors to an outside room?
j As Yes. To allow credit for opening de, ors for cooling, the l
outside room should be cooler than the room being analyzed and should be sufficiently large that hot air f rom the inside j
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 I
procedures should identify the doors to be opened.
YNPS Applicability i
The YNPS analysis is consistent with this response.
Plant
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procedures identify all doors required to be opened.
I 2.7 Q:
Are there circumstances where cabinet doors need not be
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opened as provided in Question / Answer No. 82 of Responses to j
Questions Raised at NUMARC 87-00 Seminars (October 1988) to i
ensure that the Control Room is not a DACT I
As 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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WPP79/16
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ENCLOSURE I
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(continued)
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F YNPS Applicability I'
l' Plant procedures call for opening the Main Control Board doors.
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Section 3: Required Coping Duration Category 3.2. Part 1D. Evaluating Independence of Off-Site Power System 3.1 Q:
How quickly.must manual transfers be made when evaluating the independence of off-site power systems (I Uroup)?
A Any manual method of transferring power sources for all safe shutdown buses is acceptable providing the transfer can be accomplished in a reasonable time, such as less than one hour. Thus, a manual transfer involving operation of a disconnect link requiring several hours to complete is not e,eceptable.
YNPS Applienbility As indicated in Section 3 of the YNPS SB0 analysis, there is i
no fast transfer upon loas of the main generator to reserve station transformers. Upon loss of the YNPS main generator, t
two 011 Circuit Breakers (OCBs) trip and two normally aligned independent off-site sources provide power to separate 3
station buses. Subsequent menual transfers are accomplished i
within minutes from the' Control Room to provide power to the third or center bus from one of the' independent supplies.
r 3.2-Q:
How independent must switchyards be for the purpose of I Group determinations?
At A "no" answer to Criterion A P. 3-11 of NUMARC 87-00 requires that 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 buses.
Physical independence would be satisfied by two separate and distinct switchyards each bounded by a perimeter fence.
Supplying power to plant unit safety buses via (1) multiple voltage transformations occurring within a single switchyard area, or (2) via designated switchyard buses originating from a single switchyard, does not satisfy the intent for physical switchyard independence.
YNPS Applicability Section 3 of the YNPS SB0.malysis indicates that all off-site power sources are connected to the unit's safe shutdown buses through one switchyard.
(Yes answer to Criterion A, P. 3-11.1 '
UPP79/16
l.
I, ENCLOSURE I
[3 (continued) l-t i
3.3 Q-Where normal ac power is provided by the unit main generator l'
and only one of two safe shutdown buses is automatically or g
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manually transferred to preferred or alternate off-site L
sources, does that qualify as a transfer of all safe shutdown busest l
l
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At No. All safe shutdown buses must be transferred per Criteria B(1) and B(2), P. 3-11, of NUMARC 87-00.
)
YNPS Applicability f
c.
The YNPS configuration is unique with respect to this issue.
l However, functionally, alt safe shutdown buses are automatically and manually transferred to the preferred off-site sources. See response to 3.2 above.
i 3.2.2. Part 2.B. Determine the Number of Necessary EAC Standby Power
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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 considered?
At 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 f roin the site's design basis for operating Class 1E equipment without off-site power.
This determination does not need to take into consideration a L
simultaneous design basis event (other than loss of off-site power).
Furthermore, any variations (from the design basis) in the assumptions for loss of off-site power loads should be identified in SB0 responses to the NRC and fully justified with documentation availabic.
Additionally, the shutdown loads powered must be capable of maintaining the plant in a safe condition for an extended period (i.e., longer than the required coping duration).
YNPS Applicability Section 3 of the YNPS SB0 analysis provides a listing of all SB0 safe shutdown loads. Diesel loading calculations for the SB0 case are pcesented in Section 7 of the SB0 analysis and l
conclude that a single EDG is capable of providing power to all required loads for an extended period.
Plant procedures have buen revised to include these results.
3.5 Q:
Does safe shutdown mean cold shutdown?
l WPP79/16
tr rc F'
t ENCLOSURE I (continued)
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l As.
No.
The plant should be brought to the desian basis safe
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shutdown condition, which may be hot standby, hot shutdown, or cold shutdown.
YNPS Appilcability The YNPS SB0 analysis is consistent with this response. SB0 response procedures estat11sh stable hot standby plant I
conditions.
3.6 Q:
At e uulti+nh site, if an EAC source is used as an AAC searce, abould that EAC/AAC source be excluded from the r.e*r of EAC standby Mwet supplies used to determine the blacked-out unit's EAC Growp?
As Yes. An AAC source which is also an EAC source must be
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subtracted from the number of EAC sources available as EAC standby power supplies.
To do otherwise would be double-counting as discussed in NUMARC 87-00, P. 3-14.
YNPS Applicability
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This issue is not applicable to YNPS.
1 Section 4: Station Blackout Response Procedures 4.2.1 Station Blackout Response Guidelines 4.1 Q:
Is it acceptable to dispatch an operator from the Control Room to the remote shutdown panel for the purpose of I
providing power from the Appendix R diesel or the safe shutdown facility?
A:
Yes. However, the Control Room should not be abandoned.
It is anticipated that recovery from an SB0 may require. operator action or monitoring from the Control Room.
l YNPS Applicability The YNPS SB0 response procedures are implemented from the Control Room. The Control Room is not abandoned.
L' Section 7: Coping with a Station Blackout Event 7.1 Q:
When ensuring containment integrity, can normally clor,ed valves be excluded from consideration similar to valves normally locked closed during operation per NUMARC 87-00, Section 7.2.5, Step 1 (1).
' WPP79/16
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ENCLOSURE I (continued's fe i.
At No.
A normally closed valve may not be considered to be a
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normally locked closed valve unless some action is taken to
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l prevent valve operation. Such actions would include removing a
control power fuses or racking out breakers supplying power to motor operators.
YNPS Applicabili,t,y l
All appropriate containraent isolation valves at YNPS are either air operated, manual, or manually closed MOVs with power removed. All manual valves are normally closed. All air-operated valves close upon loss of air or initiation of containaent isolation.
7.2 Q:
Can the main Control Room be disabled and evacuated to reduce the battery loads when assessing battery capacity to support
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decay heat removal during SBO?
At No.
The normal battery-backed plant monitoring and electrical system controls are an integral part of the Control Room and are considered essential for successfully coping with and recovering from the SBO. Therefore, it is unacceptable for a utility to dlsable and evacuate the Control Room for the purpose of reducing battery loads.
YNPS Applicability The YNPS SB0 anulysis and response procedures are consistent I
with this response.
APPENDIX Bt Alternate AC Power Criteria B.1 Q:
What single failure considerations are applicable at a multi-unit site where EAC sources are utilized for AAC7 j
At When a Class 1E 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-Blacked-Out (NBO) unit.
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. Refer to NUMARC 87-00, P. 2-2 through 2-4.
YNPS Applicability This issue is not applicable to YNPS.
B.2 Q:
What single failure considerations are applicable to SB0 AAC power systems? WPP79/16
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ENCLOSURE I (continued)
At Per Criterion B.8.e of NUMARC 87-00, the AAC power source I
must not be susceptible to a single point vulnerability whereby a likely weather-related event or single active failure could disable any portion of the on-site EAC power i
sources or the preferred (off-site) power sources, and simultaneously fail the AAC power source.
Random failures other than the type addressed by Criterion B.8.e are not contemplated and need not be considered. See also Question / Answer C.1, below.
YNPS Applicab111ty Appendix B of the YNPS SB0 analysis is consistent with this f
position.
B.3 Q:
What loads must be carried by an AAC source which is also an EAC source?
A The AAC source must carry:
(1) the loss of off-site power safe shutdown loads on the NB0 unit as described in Question / Answer 3.4, above, and (2) the SB0 loads on the blacked-out unit for the required coping duration. The capacity of the EAC source of the NB0 unit to be credited as an AAC source for the blacked-out unit can only be the excess capacity above the loss of off-site power loads of the NB0 unit. Shedding of any loads should not lead to degradation of the NB0 unit's loss of off-site power safe shutdown capability. Beyond the duration of SB0, 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 will not degrade the performance of any shutdown systems or component. At a multi-unit site, except for 1/2 shared of l
2/3 emergency AC power configurations, an adjacent unit's l
Class 1E power source may be used as an AAC power source fot l.
the blacked-out unit if it is capable of powering the required loads at both units."
1.
It is expected that AAC sizing determinations consider both I.
steady state and dynamic loading effects.
t YNPS Applicability l
l The above response refers to multi-unit site configurations and is only partially applicable to YNPS in that any one of three installed EDGs is credited at an AAC source.
(Refer to Question / Answer 3.4 for loading during SBO.),
WPP79/16 l
c ENCLOSURE 1 i
(continued) l f
APPENDIX C: Sample AAC Configurations i
c C.1 Qt Is it acceptable to connect the AAC source to the blacked-out unit by a single crosstie?
i At Yes. However, when the AAC source is one of the available Class 1E EAC sources, the crosstic must be able to supply power to the blacked-out unit f rom any EAC/AAC source.
i Example 1 - A singic crosstie connected to either of two EAC sources is acceptable. Figures A and B, Attachment 1, show two such crosstie configurations, although acceptable configurations are not limited to these examples.
In this case, a single failure of one EAC source does not prevent use of the second EAC source for AAC power.
l Example 2 - Figure C, attached, illustrates a potentially unacceptable single crosstie connecting one EAC source to a second EAC course, and then connecting 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 EDG single failure. The remaining diesel (21 or 22) may be designated as an AAC source provided Appendix B criteria are satisfied.
- However, a single active failure of Bus 21 would violate Criterion B.8.e regardless of which EAC source (21 or 22) is the AAC source.
YNPS Applicability l
The YNPS AAC configuration is clearly shown and described in l'
the initial NRC SB0 response letter.
II. to Reference (b) NUMARC 87-00 Maior Assumptions As stated in NUMARC 87-00, Section 1.3, it is important that utilities' verify I
that base line assumptions are applicable to their plants. Chapter 2 of l
NUMARC 87-00 discusses base line assumptionst however, other chapters include i
additional assumptions as well. Many assumptions are verified in the course of performing the various coping calculations, but some assumptions require specific verification.
i l
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 l
Seminars (October 1988):
" utilities are not expected to perform rigorous l
analyses or evaluations in verifying the assumptions of NUMARC 87-00."
lL However, utilities are expected to evaluate the applicability of the l
assumptions to individual plants, and this evaluation should be documented and available for NRC review. WPP79/16-
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ENCLOSURE I j
(continued)
YNPS_ Applicability This assumption has been addressed in Section 2.0 of the YNPS SB0 analysis.
2.7.1(2)(a) Control Room temperature does not exceed 120'F. Utilities usually verify this assumption, but sometimes misapply the methodology of NUMARC 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 t
dominant areas of concern are as follows:
1.
Initial wall temperatures assumptions are not verified by actual measurement.
2.
Wall temperatures for walls acting as heat sinks in air conditioned rooms are assumed to be at the initial room temperature. This is valid if the rooms on both sides of the wall are air conditioned to the same temperature.
If the outside wall temperature is hotter, i.e., not air conditioned, the average wall temperature, not the air conditioned room temperature, should be used; 3.
Where a continuous drop ceiling prevents free passage of air out of the dominant area of concern, air volumes above cannot be included in the analyzed room's free volume when using the NUMARC 87-00 methodology. Other analyses can properly take credit for heat transfer across the ceiling tiles, and these additional analyses should be identified to the NRC.
4.
Only poured concrete walls may be used as heat sinks, not cinder block or wall board (Section E.3.1).
Other analyses can properly take credit for other types of wall materials, and these additional analyses should be identified to the NRC.
5.
In order to take credit for opening doors to an adjacent room, the adjacent room must be large and at a lower temperature relative to the room in question.
(See Section E.3.3.)
Opening a closet door, for example, will not provide a significant heat sink and cannot be credited.
YNPS Applicability 1.
Plant temperature data has been used in the revised loss of ventilation calculations.
2.
Average wall temperature has been utilized in the Control Room loss of ventilation analysis. WPP79/16
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ENCLOSURE I (continued) b Listed below are major assumptions which in some cases have not been I
satisfactorily verified.
Preceding each assumption is the number of the applicable NUMARC 87-00 section.
2.4.1(1)
The event ends when ac power is restored to shutdown buses from any source. To support ac power restoration it will be necessary to close breakers. This can be done either j
manually or electrically via de power. For those utilities utilizing DC power, the ability to close breakers at the end of the blackout should be included in the battery calculation. The first availabic power source can be an EDG; therefore, flashing of the EDG field should also be included in the calculation.
YNPS Applicability This issue is cicarly addressed in Section 2 of tha YNPS SB0 i
analysis.
YNPS utilized an EDG as an AAC source. This unit will start immediately upon loss of power. Switching both inside and outside the Control Room will be conducted to power all SB0 shutdown loads within one hour.
A single battery charger will also be energized to provide power to all required de loads within two hours following initiation of the SB0 event. Existing battery capacity calculations demonstrate adequate capacity of all station batteries for greater than two hours.
2.5.2 Reactor coolant pump seal leakage is assumed not to exceed 25 gpm per pump.
It is recognized that BWRs do not have reactor coolant pumps; however, recirculation pump leakage should be evaluated. The NRC staf f has indicated that 18 gpm r
is an acceptable assumed leakage rate for BWR reqirculation pumps.
BWRs/PWRs taking credit for lower leakage rates should have documentation to support use of the lower rates.
YNPS Applicability See Question / Answer 2.1, 2.7 Loss of ventilation effects.
2.7.1 Temperatures resulting f rom loss of ventilation are enveloped by LOCA and HELB profiles. LOCA/HELB transients dump large amount of energy into a containment in a short time, thus, this assumption may seem intuitive.
However, LOCA/HELB analyses assume f ans and coolers are operating. During SBO, containment fans and coolers may not be available. This assumption, therefore, should be verified. WPP79/16
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ENCLOSURE I
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(continued) 3.
In the revised analysis, the continuous dropped ceiling in jij the Control Room is assumed to inhibit heat transfer to the l ~
concrete slab above.
This clarification combined with limited poured concrete heat transfer area in the Control i
Room have resulted in overly conservative calculated temperatures using the NUMARC methodology. Therefore, actual Control Room test data has been used to demonstrate that the Control Room temperature will remain below 120'F.
4.
The impact of heat transfer to masonry block walls has been incorporated into the area heatup calculations.
5.
The YNPS analysis is consistent with this position.
2.7.1(2)(b) Loss of heating in the Battery Room is assumed not to affect battery capacity.
Provided battery capacity calculation used the lowest electrolyte temperature anticipated under normal operating conditions, further consideration of loss of battery capacity is not required, per NUMARC 87-00, P. 7-7.
YNPS Applicability This issue is addressed in Section 2 of the YNPS SB0 analysis.
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