05000271/LER-1999-001, :on 990105,determined That Pump Curves Used in Assessing RHRSW Pump Performance Had Not Been Correctly Applied to Vynp Configuration.Caused by Inadequate Communication.Sw Task Established.With
| ML20203C044 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 02/04/1999 |
| From: | Balduzzi M VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BVY-99-025, BVY-99-25, LER-99-001, LER-99-1, NUDOCS 9902110154 | |
| Download: ML20203C044 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) |
| 2711999001R00 - NRC Website | |
text
e l-L ; VERMONT YANKEE
' NUCLEAR POWER CORPORATION I
i r3 -
P.O. Box 157. Governor Hunt Road
{
vernon, vermont. 05354-0157 sv (802) 257-7711 1
)
l February 4,1999 BVY 99-025 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington D.C. 20555
Subject:
Vermont Yankee Nuclear Power Station License No. DPR-28 (Docket No. 50-271)
Reportable Occurrence No. LER 99-001, Rev. O As defined by 10CFR50.73, we are reporting the attached Reportable Occurrence as LFR 99-001, Rev. O.
1 Sincerely, VERMONT YANKEE NUCLEAR POWEft CORPORATION Y$N'
/
Michael A Balduzzi Plant Manager cc:
USNRC Region I Administrator USNRC Resident inspector-VYNPS USNRC Project Manager-VYNPS VT Dept. of Public Service 9902110154 990204 7
PDR ADOCK 05000271*
S PDR h
l S
L
APPROVED BY OMB NO. 3150-0104 EXPlRES 06/30/2001 NRC FIRM 366 U.S. NUCLEAR REGULATORY COMZlSSION (6-1998)
Estimated burden per r:sponse to comply with this mandatory a
information collection rrquest: 50 hrs.
RIportid icssons leimed cra incorporated into the lic:nsing proc:ss tnd fed bick to industry. Forward comments regarding burden estimate to LICENSEE EVENT REPORT (LER) the Records Management Branch (T-6 F33). U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, and to the Paperwork Reduction Projec. 13150-0104), Office of Management and Budget, Washing _ - DC 20503, if an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
FACILRY NAME (1)
DOCKET NUMBER (2)
PAGE (3)
Page 1 of 4 VERMONT YANKEE NUCLEAR POWER CORPORATION (VY) 05000271 mumi INADEQUATE COMMUNICATION BETWEEN LICENSEE AND EQUIPMENT MANUFACTURER RESULTS IN THE INCORRECT APPLICATION OF A MANUFACTURER SUPPLIED PUMP CURVE AND AN UNANALYZED CONDITION.
EVENT DATE (5)
LER NUMBER (6)
REPORT DATE (7)
OTHER FACIL(TIES INVOWED (8) so RE 8 N MONTH DAY YEAR YEAR MONTH DAY YEAR FACILITY NAME DOCKET NUMBER U
R 01 05 99 99 01 00 02 04 99 N/A OPERATING THIS REPORT lts SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR : (Check of;e or more) (11)
MODE (9)
)
N 20.2201(b) 3 20.2203(aH2)(v) 50.73(a)(2)(i) 50.73(aH2Hviii)
]
20.2203(aH1) 20.2203(a)(3Hi)
X 50.73(aH2)(ii) 50.73(aH2)(x)
L V L 10) 34-20.2203(aH2Hi) 20.2203(aH3Hii) 50.73(aH2Hiii) 73.71 I
20.2203(a)(2Hii) 20.2203(aH4) 50.73(aH2)(iv)
OTHER 20.2203(aH2Hiii) 50.36(c)(1) 50.73(aH2)(v) 20.2203(aH2Hiv) 50.36(c)(2) 50.73(aH2)(vii)
$c krNN'6k*
- ' i" LICENSEE CONTACT FOR THIS LER (12)
NAME TELEPHONE NUMBER (include Area Code)
Michael A. Balduzzi, Plant Manager (802) 257-7711 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (12)
RE RT LE RE
CAUsE
SYSTEM COMPONENT MANUFACTURER
CAUsE
SYSTEM COMPONENT MANUFACTURER EP N/A N/A i
1 N/A N/A l
SUPPLEMENTAL REPORT EXPECTED (14)
MONTH DAY YEAR EXPECTED i
SUBMISSION I
YES X
NO DATE (15)
(if yes, complete EXPECTED SUBMISSION DATE).
ABSTRACT (Limit to 1400 spaces,i.e., approximately 15 single-spaced typewritten lines) (16)
On 01/05/99 VY determined that pump curves used in assessing Residual Heat Removal Service Water Pump p:rformance had not been correctly applied to the VY configuration. The curves supplied by the manufacturer were for ths VY pump design when installed in a standing pool. The pumps supplied to VY for this application were of a "c:nned" design. The can, which houses the pump casing, allows a piped connection to the pump suction. The canned disign introduces a pressure drop that should be included during NPSH calculations. It was not understood by VY that thtra was an adjustment necessary when applying the curves to the pumps provided to VY. The reduction in available NPSH, caused by the canned design was not considered in subsequent calculations. The effect of that reduction is i>cing assessed in a calculation. RHRSW safety functions relating to accident mitigation, as described in the VY FSAR, era not challenged by this condition. The issue of concern relates to the RHRSW pumps running in the Alternate Cooling System (ACS) mode. This mode would be employed in the event of a loss of access to the Connecticut River es the plant's normal heat sink. VY had previously established administrative limits upon plant operation with elevated supply temperatures (>73 F) that ensured adequate RHRSW pump NPSH while calculations were being performed. It is exp:cted that calculations will demonstrate that the RHRSW system as-built configuration supports all system safety functions including the ACS mode. Therefore, this event did not increase the risk to public health and safety.
NRCFoRM 366 (6-1998) u <
j
... ~ -
- U.S. NUCLEAR REGULATORY COMMISSION (6-1998)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION SEoU T AL REVS N f.,oCKET YEAR FACIUTY NAME (1) a VERMONT YANKEE NUCLEAR POWER CORPORATION 05000271 99 01 00 Page 2 of 4 TEXT ttimore space e reewrent, use acwtoorralcopes of NRC Form 366N n1)
DESCRIPTION
On 01/05/99, while operating at 34% of rated thermal power, VY was reviewing Residual Heat Removal Service Wetar (RHRSW) pump performance data and related calculations to address concerns raised by RHRSW pump digradation revealed during in-service testing. During that review, VY identified that pump curvas used in assessing RHRSW (Ells =BI) Pump performance had not been correctly applied to the VY configuration.
During 1994 work efforts to better understand and possibly improve RHRSW pump capabilities, VY obtained pump curves from the pump manufacturer.
Tha curves supplied by the manufacturer were specific to the VY pump design, if the pumps were installed in a standing pool. However, the pumps (Ells =P) supplied to VY for the RHRSW application were of a " canned" design.
j The can, which houses the pump casing, allows a piped connection to the pump suction. The canned design introduces a pressure drop that should be included during Net Positive Suction Head (NPSH) calculations. It had not i
bun understood by VY that there was an adjustment necessary when applying information obtained from the curves to the pumps provided to VY. Therefore, the reduction in available NPSH, caused by the canned design was not considered in related calculations.
CAUSE
1.
Inadequate communication between VY and the pump manufacturer failed to identify that adjustments were necessary when applying the information within manufacturer-supplied pump curves to the VY as-built configuration.
Because of the unique configuration of the RHRSW pump and suction can, VY considers the variance between the information provided in the pump curves and the expected pump performance / requirements to be an isolated condition. The VY RHRSW pumps are Byron Jackson, Model VTP, type 16CGH pumps.
Tha investigation for this event continues. Should additional information bo identified which significantly changes the id:ntified cause or corrective actions from the preliminary conclusions communicated here, a revision to this report will be issued.
ANALYSIS OF THE EVENT
Ths VY RHRSW pumps perform safety functions in two different applications. First, they function within the RHRSW sysh hself to provide adequate flow to achieve the safety design bases of that system. Additionally, the VY Alttrnate Cooling System employs the RHRSW pumps in achieving its design functions.
Tha VY Final Safety Analysis Report identifies the fol!owing Safety Design Bases for the RHRSW system.
1.
Provide sufficient cooling capacity for the RHR System during a design basis accident.
2.
Minimize the probability of a release of radioactive contaminants to the environs.
L sn operating to support these two safety design bases, the RHRSW pumps take their suction from an operating (prs, surized) Station Service Water (SSW) System supply header, in this configuration adequate suction head is czrtally available and the ability of potentially affected systems to fulfill their safety design bases is assured.
The challenge to the RHRSW pump functionality is restricted to RHRSW pumps operating in the " Alternate Cooling" mode. Postulated events that would necessitate ACS initiation are:
1.
A loss of SSW, due to a failure of a downstream dam in the Connecticut River (Vernon Dam),
2.
A fire in the intake structure which disables all four Station Service Water pumps 3.
An external flood of a magnitude that disables all 4 SSW pumps.
During these events, the Station Service Water (SSW) Pumps would no longer be capable of supplying plant cooling nMds. Nor would they provide a pressurized supply to the suction of the RHRSW pumps. Under such conditions plint procedures direct the operating crew to align the affected systems in the Alternate Cooling mode. This manual dignment entails arranging the RHRSW pumps to take a suction from a dedicated, safety class cooling tower deep.
lU.S. NUCLEAR REGULATORY COMMISSION (6-1993)
UCENSEE EVENT REPORT (LER)
TEXT CONTINUATION 3E FACluTY NAME (1)
DOCKET YEAR U
U R
PAGE (3) 1
)
VERMONT YANKEE NUCLEAR POWER CORPORATION 05000271 99 01 00 Page 3 of 4 uxs or,,we umco a,.wma un esa,r,ow cop,n or ec rorm seem on bisin, delivering the required cooling water to essential loads, and returning that water to the cooling tower for heat i
rej:ction. VY had previously recognized that the margins for RHRSW pump suction head available were most l
rsstrictive during alternate cooling operation. In this operating mode the system relies upon a gravity feed for the
]
we.tsr stored in the deep basin to flow to the suction of the RHRSW pumps.
)
i Th3 design bases of the Alternate Cooling System, as described in the FSAR state that the " design of the Alternate Cooling System shall make provisions for the following:
1.
An adequate heat sink to remove decay heat and sensible (cooldown] heat from the primary system so that the reactor can be safely shut down in the event of a loss of the Vemon Pond, flooding of the service water intake structure...
or fire in the service water intake structure which disable all four service water pumps.
2.
An adequate heat sink for removing decay heat from the spent fuel elements in the fuel pool and other miscellaneous heat loads generated while maintaining safe shutdown conditions.
3.
Sufficient on-site water storage, in the event of a loss of Vernon Pond, to accommodate Alternate Cooling System losses for a period of one week.
4.
The electrical power necessary for Alternate Cooling System operation is to be within the capacity of the station standby diesel generators.
5.
Earthquake ground motions shall not impair the ability of the Alternate Cooling System to fulfill Safety Design Bases 1,2, and 3, for the foss of Vemon Pond [Vernon Dam] scenario. "
Dus in part to the limited margin afforded by system arrangement, relative to RHRSW pump suction head rsquirements, VY tested the system's ability to provide the required flow in 1994. That test was used to gather data from actual system operation in configurations as near as practicable to the demands that would be placed upon the systsm were ACS to be required. Pumps performed as designed, providing the required flow rates. Data obtained wcs then extrapolated to assess the system's capabilities under the extreme conditions postulated in the plant design t
b:sss. That assessment concluded that the ACS could be expected to perform as designed during the design basis scanarios.
None of the previously described ACS necessitating events are postulated to occur coincident with any other plant transient or accident. The VY FSAR states, "the Alternate Cooling System is not classified as an Engineered Safaguard System and is not designed to accept the consequences of a design basis loss-of-coolant accident, it is clso not single failure-proof." Therefore, the task of the operating crew would be to align the system to remove diccy heat, while providing the needed cooling for the plant emergency diesel generators, and the spent fuel storage pool. System design would allow ACS operation under these conditions for a period of 7 days without the need to rsplenish the water inventory.
l On 01/05/99, when it was recognized that the effects of the pump suction can had not been considered in previous calculations, VY had administrative controls in place restricting plant operation with deep basin temperatures in l
cxc:ss of 73 degrees Fahrenheit (F). These administrative controls had been imposed because VY in-service testing l
(IST) of the RHRSW pumps had indicated degradation in pump performance. Although it was concluded that the tpptrently degraded pumps remained capable of satisfying all IST and design basis requirements,it had been decided to impose these operating restrictions to restore the margin desired between the pump "as-found" condition and the minimum acceptable performance. VY continues to investigate to determine the cause for the RHRSW pump
).
performance degradation.
L A rsview of the in-place administrative controls, imposed due to the apparently degraded condition of the RHRSW pumps, revealed that adequate NPSH would be assured pending resolution of the questions raised by the flow j
r:striction introduced by the RHRSW pump suction can.
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- U.S. NUCLEAR REGULATORY COMMISSION 16 1998)
UCENSEE EVENT REPORT (LER)
TEXT CONTINUATION sE FACluTV NAME (1)
DOCKET YEAR Nu R
U R
PAGE (3)
VERMONT YANKEE NUCLEAR POWER CORPORATION 05000271 99 01 00 Page 4 of 4 TEXT Ut rnare space on reousted, use acidotronalcopies of NRC Form 366At (11)
)
Additional assessments of the VY current licensing basis (CLB) for ACS operation have identified that the heat load Essumed in previous calculations may exceed that required to support plant operation consistent with the VY CLB.
Sp cifically,it was recognized that some plant coo! down rates assumed in determining the flow requirements of ACS may exceed the system performance requirements established by VY's CLB. VY is continuing to assess its CLB ral:tive to ACS as part of a Service Water task team mission.
Conclusion l
RHRSW safety functions relating to accident mitigation, as described in the VY FSAR, are not challenged by the previously unidentified flow restriction introduced by the RHRSW pump suction can. The issue of concern relates to thip RHRSW pumps running in the ACS mode. Assessments have shown that there is a reasonable expectation that til system safety functions, including those performed by the ACS mode, would have been achieved if called upon.
Additionally, it is expected that calculations will demonstrate that the RHRSW system as-built configuration supports til system safety functions including those related to the ACS mode of operation. Therefore, this event did not incrsase the risk to public health and safety.
CORRECTIVE ACTIONS
1.
A VY internal event report was initiated to ensure that a formal cause determination is performed and that appropriate corrective actions are implemented. The expected completion date for the event investigation and corrective action recommendation is 03/15/99.
2.
A Basis for Maintaining Operation (BMO) had been approved which ensured that adequate margin was available relative to RHRSW pump performance capabilities and system minimum performance requirements. That BMO is i
being revised to document that adequate margin is also maintained between RHRSW pump NPSH required and NPSH available. The BMO is expected to be revised by 02/17/98.
3.
The effect of the reduction in available NPSH is being assessed in a calculation. The expected completion j
date is 06/30/99.
1 4.
A Service Water task team has been established. The task team will explore operational, maimenance, and 4
technical solutions to the apparently degraded ACS performance. The efforts of the Task Team will augment the ongoing efforts of the VY System Engineering Department in monitoring and improving the performance of the ACS system.
ADDITIONAL INFORMATION
VY has reported one similar event during the previous 5 years as LER 94-02, " Alternate Cooling System Water Temperature Greater Than Design Basis During Warm Weather Circ Water System Operation Due to inadequate Antlysis of the Alternate Cooling System" (dated 06/30/94)..~