ML20207G819
| ML20207G819 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 12/23/1986 |
| From: | Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE |
| To: | Noonan V Office of Nuclear Reactor Regulation |
| References | |
| SBN-1261, NUDOCS 8701070405 | |
| Download: ML20207G819 (7) | |
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.A SEABROOK STATION Engineering Office December 23, 1986 SBN-1261 New Hampshire Yankee Division T.F.
Q2.2.2, B7.1.3 United States Nuclear Regulatory Commission Washington, DC 20555 Attention:
Mr. Vincent S. Noonan, Project Director PWR Project Directorate No. 5
References:
(a)
Facility Operating License NPF-56, Construction Permit CPPR-136, Docket Nos. 50-443 and 50-444 (b) NRC Letter, "Ouestions in Regard to Seabrook Unit 1 Pertaining to 10CFR50.55(e) Report on Emergency Core Cooling Deficiency (Reactor Systems Branch Standard Review Sections 5.4.7, 6.3.15.)", V. Nerses to R. J.
Harrison Subj ect :
Additional Information on Emergency Core Cooling Design
Dear Sir:
Enclosed please find New Hampshire Yankee (NHY's) response to the Staff's questions provided in Reference (b). In this regard, it is NHY's understanding that these questions were the basis of a prior telephone discussion with the Staff on or about October 9,1986. As such the enclosed responses are, to some degree, a confirmation of this earlier discussion.
If the Staff requires any further clarification or information, do not hesitate to contact the NHY Bethesda Licensing Office.
Very truly yours, y
j John DeVincentis Director of Engineering Enclosure cc: Atomic Safety and Licensing Board Service List h
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S PDR -
P.O. Box 300. Seabrook, NH 03874. Telephone (603) 474 9574
6 Dicn2 Curr n, Etquira P2 tar J. Mathiws, Maysr Harmon & Welco City H211
.2001 S. Street, N.W.-
Newburyp3rt, MA 01950 Suite 430
~
Washington, D.C.
20009 Judith H. Mizner Silvergate, Gertner, Baker, Sherwin E. Turk, Esquire Fine, Good & Mizner Office of the Executive Legal Director 88 Broad St.
U. S. Nuclear Regulatory Commission Boston, MA 02110 Tenth Floor Washington, DC 20555 Calvin A. Canney City Manager Robert A. Backus, Esquire City Hall 116 Lowell. Street 126 Daniel Street P. O. Box 516 Portsmouth, NH 03801
. Manchester,.NH 03105 Stephen E. Merrill, Esquire
. Philip Ahrens, Esquire Attorney General Assistant Attorney General George Dana Bisbee, Esquire Department of the Attorney General Assistant Attorney General Statehouse Station #6 25 Capitol Street Augusta, PE 04333 Concord, NH 03301-6397 Mrs.' Sandra Gavutis Mr. J. P. Nadeau Chairman, Board of Selectmen Selectmen's Of fice RFD 1 - Box 1154 10 Central Road Kensington, NH 03827 Rye, NH 03870 Carol S. Sneider, Esquire Mr. Angie Machiros Assistant Attorney General Chairman of the Board of Selectmen Department of the Attorney General Town of Newbury One Ashburton Place,19th Floor Newbury, MA 01950 Boston, MA 02108 Mr.. William S. Lord Senator Gordon J. Humphrey Board of Selectmen U. S. Senate Town Hall - Friend Street Washington, DC 20510 Amesbury, MA 01913 (ATTN:
Tom Burack)
Richard A. Hampe, Esquire Senator Gordon J. Humphrey Hampe and McNicholas 1 Pillsbury Street 35 Pleasant Street Concord, NH 03301 Concord, NH 03301
( ATTN:
Herb Boynton)
Thomas F. Powers, III H. Joseph Flynn, Esquire Town Manager Office of General Counsel Town of Exeter Federal Emergency Management Agency 10 Front Street 500 C Street, SW W shington, DC 20472 Exeter, NH 03833 a
Brentwood Board of Selectmen Paul McEachern, Esquire RFD Dalton Road Fbtthew T. Brock, Esquire Brentwood, NH 03833 Shaines & McEachern 25 Maplewood Avenue Gary W. Holmes, Esquire P. O. Box 360 Holmes & Ells Portsmouth, NH 03801 47 Winnacunnet Road Hampton, NH 03842 Mr. Ed Thomas Robert Carigg FEMA Region I Town Office 442 John W. McCormack PO & Courthouse Atlantic Avenue Boston, MA 02109 North Hampton, NH 03862
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ENCLOSURE 1 TO SBN-1261 1.
NRC OUESTION/RE0UEST Please define the magnitude of the problem (ECCS design deficiency) a.
with respect to NPSH.
b.
What is the actual head provided to the high pressure SI pumps and to the charging pumps with the deficiency uncorrected and how does this compare to the pump requirements?
c.
What pump suction and containment sump conditions are assumed in arriving at these values and how do these compare to the conditions which exist when suction is from the RWST?
d.
What is the actual head provided to the high pressure SI pumps and to the charging pumps with the deficiency corrected?
RESPONSE
Assuming an active failure of the Train ' A' low head safety injection a.
(RHR) pump with both centrifugal charging pumps (CCPs) and both high head safety injection pumps (SIPS) operating, the NPSH provided to the active RHR pump is only slightly less than that required. This deficiency would have resulted in damage to the pump if allowed to persist for an extended period of time. Essentially no NPSH would be provided to the CCPs resulting in almost immediate pump damage. The NPSH provided to the SIPS would be greater than that required.
b.
For the scenario described in the response to (a), the actual NPSH provided to the SIPS is 81.6 ft.
For the same scenario, however involving the failure of the Train 'B' RHR pump, the NPSH provided to the SIPS is 59.7 ft.
The SIPS require an NPSH of 9 ft. each with both pumps operating.
For the scenario described in the response to (a), the actual NPSH provided to the CCPs is (-) 1.9 ft.
The CCPs require an NPSH of 18 ft. each with both pumps operating.
c.
The containment sump is assumed to be saturated with the water at a flood level calculated from the available volume of cooling water and and with consideration for the structural configuration of containment.
Given these conditions, the suction pressure for the active RHR pump is 8.6 psig. The NPSH available to the pump is 20.6 f t.
These pump suction conditions apply only to the cold leg recirculation mode of ECCS oper-ation. The RHR pumps take suction from the RWST only during the cold leg injection mode. Because the subject deficiency and system realignment do not af fect the injection mode, pump suction conditions which exist when suction is from the RWST are irrelevant.
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- s ENCLOSURE 1 TO SBN-1261.
(Continued) 4 d.
Assuming a failure of the Train 'A' RHR pump with both SIPS and both CCPs operating, the NPSH provided is 132 f t. to the SIPS and 65 f t.
to the CCPs.
Although information provided in response to Question #1 generally corresponds to most as limiting single failure scenarios, it should be noted that all possible failure scenarios were analyzed for the modified system alignment in determining the acceptability of the 1
modification.
2.
NRC QUESTION / REQUEST Changes in valve alignment are described by submitting a marked up copy of portions of FSAR Figure 6.3-2.
This figure does not provide specific valve identifications, nor does it allow the Staff to satisfactorily identify valves involved due to differences in nomenclature and the schematic nature of the figure.
Please identify the valves listed in sheets 2 and 3 of the notes to Figure 6.3-2.
It would be helpful if this information could be additionally provided on a marked up copy of FSAR Figure 6.2-78 in a form that shows which valves are open and which are closed for the injection mode, the cold leg recirculation mode, and the hot leg recirculation mode.
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RESPONSE
FSAR Figure 6.3-2 is a simplified process flow diagram intended to illustrate the operation of the ECCS. It is not a detailed piping and instrumentation diagram (P&ID) and as such the designated valve numbers do not correspond to actual valve tag numbers.
In order to f acilitate review, the Staff should utilize FSAR Figures 5.4-10 (RHR System), 6.2-77 (Containment Spray System), 6.2-78 (Engineered Safety Features), and 6.3-1 (Safety Injection System). Correlation of these figures to Figure 6.3-2 should provide adequate clarification for the Staf f's review.
3.
NRC QUESTION / REQUEST If the ortginal accident begins as an RHR line break, please describe l
how the response is affected by the new configuration.
Please also I
show where this response is covered by procedures.
Include consider-l ation of the time that pumps can operate while discharge takes place into the break and the impact of that operation upon pump operability if pump NPSH requirements are not met.
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r-ENCLOSURE 1 TO SEN-1261
( Continued)
RESPONSE
The response is not affected if the initiating event involves an RHR line break. Operational procedures mandate establishing the system alignment (previously discussed with the NRC) upon switchover to cold leg recircu-lation. Given this system alignment, all pump NPSH requirements are met and core cooling requirements satisfied regardless of whether or not an RHR injection path is lost as a result of the LOCA.
4.
KRC QUESTION /RE0UEST Please contrast system performance as analyzed and describe in the FSAR as approved by the Staff, and system performance with the system modified as described in References 1 and 2.
Identify all differenes.
RESPONSE
The system modification described does not affect the ECCS during the in-jection and hot leg recirculation modes. During the cold leg recirculation mode, the system as modified satisfies NPSH requirements for all ECCS pumps for all failure scenarios postulated in accordance with the FSAR.
This satisfies the intent of the original system design. Although certain flow paths and some specific flourates are altered by the realignment, the system as modified satisfies core cooling requirements for all failure scenarios postulated in accordance with the FSAR. It follows that no differences in the ability of the ECCS to perform its intended design function exist between the system as modified and the system as previously analyzed and described in the FSAR.
5.
NRC QUESTION / REQUEST If an RHR pump fails af ter the system has been configured to the recirc-ulation mode, please indicate the actions that are taken by the operator.
Include reference to specific applicable procedures that are in place, timing of operations, and times during which pumps are operating with inadequate NPSH. Also describe the potential impact of such operation on pump operability.
RESPONSE
With the ECCS configured to the modified cold leg recirculation alignment (previously discussed with the NRC) no additional operator action is re-quired in the event of an RHR pump failure. The RHR pump which remains operating will provide adequate NPSH to the operating CCPs and SIPS.
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ENCLOSURE-1 TO SBN-1261 (Continued) 6.
NRC QUESTION / REQUEST a.
The ' proposed changes to the FSAR include addition of words " redundant motor operated valves arranged in series are provided for this isolation function". Please identify the valves.
b.
Could these valves be required to operate under accident conditions where closure would be necessary against significant RCS pressure or under dynamic conditions associated with flow from the RCS at significant pressure? If so, will the valve operators close the valves under the identified conditions? If yes, what information i
supports closure reliability.
RESPONSE
a.
This statement was added to the FSAR only to emphasize the fact that the two RHR trains are separable in the event of a passive failure (i.e., pump seal leak). The valves being referred to are RH-V21,V22 (Reference FSAR Figure 5.4-10) and CS-V460,V461,V475 (Reference FSAR Figure 6.3-1,Sht. 2).
b.
These valves will only be required to close against RRR system pressure to separate the trains in the event of a passive failure.
The modified system alignment has no affect on the ability of these valves to perform this function.
7.
NRC QUESTION / REQUEST Step 3 of Table 6.3-7, Sheet 1, has been changed to indicate that one valve should be closed. Would it be better to identify a specific valve or to provide wording that more strongly indicates that both valves should not normally be closed at this time?
(Note:
the modified Table 6.3-10 entry for times 115-145 and 145-160). Please address accident conditions, such as accident initiation by failure of one of the injection lines at the RCS, as part of the response.
RESPONSE
The eme rgency operating procedure which governs the switchover to cold leg recirculation specifically requires that RH-V14 be closed.
In the event that RH-V14 f ails to close, the procedure requires closure of RH-V26 prior to continuing the switchover sequence.
Failure of an RHR injection line as an accident initiating event has no impact on the switchover sequence or the system alignment during cold leg recirculation. NPSH requirements for all operating pumps will still be met and core cooling requirements will be satisfied.
It should be noted that, during the cold leg recirculation mode, core cooling requirements can be satisfied without any cooling water being delivered to the RCS directly from the active RHR pump. That is, all four RHR injection paths can be isolated and core cooling requirements satisfied for any postulated f ailure scenarios.
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o-g ENCLOSURE I TO SBN-1261 (Continued) 8.
NRC QUESTION / REQUEST Change over to the recirculation mode leaves two RHR pumps running, two SI pumps running, and two charging pumps running, with all injecting into the RCS.
What procedures exist for reduction of the number of pumps in operation and how are these affected by the changes described in References 1 and 27
RESPONSE
Reduction of the number of operating ECCS pumps during accident mitiga-tion is unnecessary. As such, no operating procedures exist which man-date this reduction.
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