ML20196K617
| ML20196K617 | |
| Person / Time | |
|---|---|
| Site: | Millstone, Haddam Neck, 05000000 |
| Issue date: | 06/30/1988 |
| From: | Mroczka E NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| 88-4, IEB-88-004, IEB-88-4, NUDOCS 8807070053 | |
| Download: ML20196K617 (6) | |
Text
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- NORTHEAST UTILITIES cenera: ottices seiden street. seriin. connecticut 1
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P.O. BOX 270
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C2'b$N*,'7 HARTFORD. CONNECTICUT 06141-0270 k
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(203) 665-5000 June 30, 1988 Docket V 3.
50-213 50-245 50-336 50-423 A07218 Re:
NRC Bulletin 88-04 U.S.
Nuclear Regulatory Commission Attn:
Document Control Desk Washington, D.C.
20555
Reference:
(1)
C.
E.
Rossi letter to Licensees dated May 5, 1988 transmitting NRC Bulletin 88-04, "Potential Safety-Related Pump Loss".
Gentlemen:
Haddam Neck Plant Millstone Nuclear Power Station, Unit Nos.
1, 2,
and 3 Response to NRC Bulletin 88-04,"Potential Safety Related Pump Loss" Reference (1) requested licensees to evaluate safety-related centrifugal pumps to ensure that pump damage will not occur during normal or emergency operation due to operation at or near shutoff head with inadequately designed minimum flow lines.
The specific actions requested, and Connecticut Yankee Atomic Power Company (CYAPCO) and Northeast Nuclear Energy Company (NNECO) responses follow.
1.
Promptly determine whether or not its facility has any safety-related system with a pump and piping system configu-ration that does not preclude pump-to-pump interaction during miniflow operation and could therefore result in dead-heading of one or more of the pumps.
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Nucl@er R33ulatory Com31ssion U
A07218/Pags 2
- June 29, 1988
Response
A review was done of all safety-related centrifugal pumps.
This review conservatively determined that 27 pumps at the Haddam Neck
- Plant, 44 at Millstone Unit No.
1, 32 at Millstone Unit No. 2, and 55 at Millstone Unit No. 3 could be affected.
Most of these pumps are not susceptible to this type of problem due to one or more of the following reasons:
o System lineup and/or operational procedures do not allow the pump to run near shutoff conditions.
o The pump has its own unshared minimum flow line.
o The pump does not operate simultaneously in parallel with another pump in the same system piping loop. provides a list of those pumps that u := ne ISH excluded for the above reasons.
Of the total potentially affected pumps, additional work on 15 in toquired to complete our evaluation (6 at Millstone Unit No.
1, 5 at Millstone Unit tio.
2, and 4 at Millstone Unit No. 3).
2.
If the situation described in Item 1 exists, evaluate the system for flow division taking into consideration (a) the actual line and component resistances for the as-built configuration of the identified system; (b) the head versus flow characteristics of the installed pumps, including actual test data for "strong" and "weak" pump flows; (c) the effect of test instrument error and reading error; and (d) the worst case allowances for deviation of pump test parameters as allowed by the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)
Section XI, Paragraph IWP-3100.
Response
Evaluations for pumps listed in Attachment 1 are underway.
All pumps listed in Attachment I have minimum flow lines containing flow restricting orifices or throttle valves.
These flow restrictions are located such that a significant pressure drop occurs prior to the point at which the separate l
minimum flow lines discharge to a common section of piping.
l This configuration should ef fectively preclude dead heading l
of any pumps.
Therefore, CYAPCO and NNECO conclude no justification for continued operation is required prior to completion of the requested evaluations.
3.
Evaluate the adequacy of the minimum flow bypass lines for safety-related centrifugal pumps with respect to damage resulting from operation and testing in the minimam flow mode.
This evaluation should include consideration of the effects of cumulative operating hours in the minimum flow l
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.S.
Nucloar R0gulatory Commission U
A07218/Page 3 J.une 29, 1988 mode over the lifetime of the plant and daring the postulated accident scenario involving the largest time spent in this mode.
The evaluation should be based on best current estimates of potential pump damage from operation of the specific pump models involved, derived from pertinent test data and field experience on pump damage.
The evaluation should also include verification from the pump suppliers that current miniflow rates (or any proposed modifications to miniflow systems) are sufficient to ensure that there will be no pump damage from low flow operation.
If the test data do not justify the existing capacity of the bypass lines (e.g.,
if the data do not come from flows comparable to the current capacity) or if the pump supplier does not verify the adequacy of the current miniflow
- capacity, the licensee should provide a plan to obtain additional test data and/or modify the miniflow capacity as needed.
Response
Of the safety-related centrifugal pumps, those whose system lineup and/or operating procedures do not allow the pump to run near shutoff condition were excluded from this evalu-ation.
The remaining
- pumps, which require the above evaluation, are listed in Attachment 2.
All of these pumps are Emergency Core Cooling System (ECCS) pumps.
CYAPCO and NNECO believe that operation of (and therefore minimum flow requirements of) these pumps differs significantly from the Reference (1) conditions.
They operate at minimum flow only briefly during surveillance testing or, during a Loss of Coolant Accident (LOCA), only long enough for Reactor Coolant System pressure to decrease below shutoff head or until manually shut off.
The 25% to 50% minimum flow for extended operation, which was mentioned in Reference (1),
is not applicable in these situations.
Preliminary conversations with several pump vendors confirm that original design minimum flows of 5% to 15% of rated flow are adequate for short durations at shutoff head.
Again, CYAPCO and NNECO conclude that no justification for continued operation is required prior to completion of the requested evaluations.
Conclusion CYAPCO and NNECO have determined that problems similar to those cited in Reference (1) have a low probability of existing at any of our plants.
Evaluations necessary to confirm this conclusion will be completed and the results reported to the NRC Staff not later than December 30, 1988.
The principal activity covering this span of time is obtaininng required information from pump vendors.
Past experience has shown that requests for such infor-mation are not always answered in a timely fashion.
Since this is substantially out of our control, the completion date has oeen conservatively set.
If vendor response is prompt, our evalu-LLions will be reported sooner.
If any reportable conditions are identified, we will notify the NRC Staff per the requirements
' U. ' S. Nuclear Regulatory Commission A07218/Paga 4 June 29, 1988 of 10CFR50.72 and 10CFR50.73.
Justifications for continued operation and plans for corrective action will be provided as necessary.
Very truly yours, CONNECTICUT YANKEE ATOMIC POWER COMPANY NORTHEAST NUCLEAR ENERGY COMPANY fa/
-E.'U /Mr6czhi f
Senior Vice President STATE'OF CONNECTICUT
)
) ss. Berlin COUNTY OF HARTFORD
)
Then personally appeated before me, E.
J.
Mroczka, who being duly sworn, did state that he is Senior Vice President of Connecticut Yankee Atomic Power Company and Northeast Nuclear Energy Company, Licensees herein, that he is authorized to execute and file the foregoing information in the name and on behalf of the Licensees herein, and that the statements contained in said information are true and correct to the best of his knowledge and belief.
th/Mtnb b
47H<'
Mota ry P'fplic MyCommission Epres March 31,1993 cc:
W.
T.
Russell, Region 1 Administrator M.
L.
Boyle, NRC Project Manager, Millstone Unit No. 1 D.
H.
Ja f. f e, NRC Project Manager, Millstone Unit No. 2 R.
L. Ferguson, NRC Project Manager, Millstone Unit No. 3 A. B. Wang, NRC Project Manger, Haddam Neck Plant W.
J.
Raymond, Senior Resident Inspector, Millstone Unit Nos.
1, 2,
and 3 J.
T. Shedlosky, Senior Resident Inspector, Haddar Neck Plant
(
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-Attachment 1 L
Potential' Pump' Minimum Flow Interaction naddam Neck High Pressure Safety Injection Pumps "A"
and "B" (P-15-1A, B)'II Low Pressure Safety Injection Pumps "A" and "B" (P-92-1A, B)II' Millstone Unit No. 1 Low Pressure Coolant Injection Pumps "A",
"B",
"C",
and "D" (M8-75A, B,
C, D)
Millstone Unit No.__2 High Pressure Safety ~ Injection Pumps "A",
"B",
and "C",
-(P-41A, B,
C)
Low Pressure Safety Injection Pumps "A" and "B" (P-42A, B)
Millstone Unit No. 3 Safety Injection Pumps "A" and "B"
(3SIH*PlA, B)
(1) Evaluations for these pumps have been completed.
Adequate minimum flow is assured for all conditions.
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x 4
. Attachment 2
%'Q,.
Potent'ially Inadequate Pump Minimum Flow
=
Haddam Neck High Pressure Safety. Injection Pumps "A" and "B" (P-15-1A, B): s i Low Pressure Safety Injection Pumps "A" and "B" (P-92-1A, B)III Residual Heat Removal' Pumps "A" and "B" -(P-14-1A, B)I Millstone Unit No. 1 Core Spray Pumps "A" and "B"
(M8-74A, B)
Low Pressure Coolant Injection Pumps "A",
"B",
"C",
"D" (M8-75A, B,
C, D)
Millstone Unit No. 2 High Pressure Safety Injection Pumps "A",
"B" and "C"
- (P-41A, B,
C)
Low Pressure Safety Injection Pumps "A" and "B"
(P-42A, B)
. Millstone Unit No. 3 Safety Injection Pumps "A" and "B"
(3SIH*P1A, B)
Residual Heat Removal Pumps "A" and "B" (3RHS*PlA, B)
(1) Evaluations for these pumps have been completed.
Adequate minimum flow is assured for all conditions.
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l s.