ML20246N563
| ML20246N563 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 05/08/1989 |
| From: | Capstick R VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BVY-89-42, IEB-88-004, IEB-88-4, NUDOCS 8905190472 | |
| Download: ML20246N563 (3) | |
Text
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VERM'ONT YANKEE NUCLEA,R POWER CORPORATION l
HD 5, Box 169 Ferry Road, Brattleboro, VT 05301
.- g ENGINEERING OFFICE 580 MAIN STREET Y g' 9
BoLToN, MA 01740 BVY 89-42 (3083779 87s1 United States Nuclear Regulatory Commission Washington, DC 20555 Attention:
Document Control Desk
References:
(a) License No. DPR--26 (Docket No. 50-271)
(b) Letter, USNRC to All Licensees for Nuclear Power Plants Holding an Operating License or a Construction Permit, NVY 88-075, "NRC Bulletin No. 88-04:
Potential Safety-Related Pump Loss," dated May 5, 1988 (c) Letter, VYNPC to USNRC, FVY 88-57, " Vermont Yankee's Response to NRC Bulletin No. 88-04, " Potential Safety-Related Pump Loss," dated July 11, 1988 (d) Letter, VYNPC to USNRC, FVY 88-86, "Results of Vermont Yankee's Long-Term Resolution Action Items: USNRC Bulletin No. 88-04," dated October 14, 1988 (e) Letter, BWROG to USNRC, BWR0G-8836, " Response to NRC Bulletin 88-04, " Potential Safety-Related Pump Loss,"
dated June 29, 1988
Subject:
Supplemental Vermont Yankee Response to USNRC Bulletin j
No. 88-04:
" Potential Safety-Related Pump Loss"
-l
Dear Sir:
l USNRC Bulletin No. 88-04, dated May 5, 1988 [ Reference (b)], requested l
all licensees to investigate and correct, as applicable, two minimum flow design concerns. The first concern involved the potential for deadhecding of one or more pumps in safety-related systems that have a minimum flow line common to two or more pumps, or other piping configurations that do not preclude pump-to-pump interaction during minimum flow operation. A second concern was whether or not the installed minimum flow capacity was adequate for even a single pump in operation.
Vermont Yankee responded to Bulletin No. 88-04 by letter, dated July 11, 1988 [ Reference (c)] and provided its long-term resolution action items on October 14, 1988 [ Reference (d)].
In Reference (d), Vermont Yankee committed to evaluate the RHR and Core Spray procedures for ways to minimize l
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h 8905190472 890508 PDR ADOCK 05000271 I
g 9
PNU i
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United States Nuclear Regulatory Commission May 8, 1989 Attention: Document Control Desk Page 2 the time the pumps are operated in the minimum flow mode and to evaluate methods of increasing the minimum flow rates of the RHR and Core Spray pumps, should it be necessary. Accordingly, the results of these evaluations are provided as Enclosure 1 to this letter.
We trust this letter and enclosure complete Vermont Yankee's response to the subject Bulletin; however, should you have any questions or require additional information concerning this matter, please contact this office.
Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION Y
+$
R. W. Ca stick Licensing Engineer RWC/sf/0304w cc: USNRC Regional Administrator, Region I USNRC Resident Inspector, VYNPS l
ENCLOSURE 1 Supplemental Vermont Yankee Response to USNRC Bulletin No. 88-04 l'otential Safety-Related Pump Loss One of Vermont Yankee's long-term resolution action items in response to USNRC
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Bulletin No. 88-04, was to evaluate the RHR and Core Spray Systems to j
determine the necessity of increasing their minimum flow rates. Additionally,
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Vermont Yankee evaluated the RHR and Core Spray procedures for ways to further
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decrease the time the pumps are operated in the minimum flow mode. As a j
result of these evaluations, Vermont Yankee provides the following:
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1.
The plant operating procedures were previously revised to address the i
most recent information on minimum flow limitations received from the pump vendors. The current procedures caution the operators to minimize the time that the pumps are run at minimum flow. Therefore, no further procedure changes are necessary at this time.
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The plant operators are trained to minimize the time that Emergency Core Cooling System (ECCS) pumps are run in minimum flow mode.
3.
Potential methods to increase the minimum flow rates were evaluated.
In order to increase the minimum flow rates of the RHR and Core Spray pumps, either the orifice sizes or the piping line sizes would have to be increased. Vermont Yankee has determined that these modifications are not necessary at this time based upon the following:
A.
Industry Experience - es documented in the BWR Owner's Group response [ Reference (e)) to this Bulletin, there has not been any indications that pump damage results from operation at minimum flow rates in the 5% to 10% range.
B.
Vendor Experience - The vendor has verified that the pump minimum flow rates at Vermont Yankee are acceptable for surveillance testing. However, the vendor (Bingham) does not have available data for operation in the minimum flow range for all time durations.
C.
Vermont Yankee Experience - minimum flow operation at Vermont Yankee I
has been of short duration and is expected to remain the same due to procedural controls and operator training (1 and 2 above).
D.
Engineering Judgement - There is a tradeoff between the reduced amount of CS/RHR flow available for injection due to increasing the minimum flow rate, should the minimum flow valve fail open versus the potential pump damage from running in r,inimum flow for an extended period oF time. Vermont Yankee has determined that it is more desirable to maintain the existing minimum flow rate as the appropriate measures have been implemented to minimize operation in this mode. Vermont Yankee's approach in minimizing the time the pumps are in the minimum flow mode, coupled with our preventative maintenance p'cogram history, ensures that the CS/RHR pumps will remain reliable.
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