05000305/LER-2002-001, Re Unanalyzed Condition: Strong Pump - Weak Pump Interaction Between Component Cooling Water Pumps
| ML020790506 | |
| Person / Time | |
|---|---|
| Site: | Kewaunee  |
| Issue date: | 03/11/2002 |
| From: | Coutu T Nuclear Management Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC-02-022 LER-02-001-00 | |
| Download: ML020790506 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(viii) 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(B) |
| 3052002001R00 - NRC Website | |
text
Kewaunee Nuclear Power Plant N490 Highway 42 Kewaunee, WI 54216-9511 920.388.2560 Point Beach Nuclear Plant 6610 Nuclear Road Two Rivers, WI 54241 920.755.2321 Committed to Nuclear Excellence Kewaunee I Point Beach Nuclear Operated by Nuclear Management Company, LLC NRC-02-022 March 11, 2002 10CFR 50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Ladies/Gentlemen:
Docket 50-305 Operating License DPR-43 Kewaunee Nuclear Power Plant Reportable Occurrence 2002-001-00 In accordance with the requirements of 10 CFR 50.73, "Licensee Event Report System," the attached Licensee Event Report (LER) for reportable occurrence 2002-001-00 is being submitted. This report contains no new commitments.
Sincerely, Thomas Coutu Manager-Kewaunee Plant ADB Attach.
cc -
INPO Records Center US NRC Senior Resident Inspector US NRC, Region III
NRC FORM 366 U.S. NUCLEAR REGULATORY APPROVED BY OMB NO. 3150-0104 EXPIRES 7-31-2004 (1-2001)
COMMISSION Estimated burden per response to comply with this mandatory information collection request:
50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Records Management Branch LICE NEE "E ENT REPORT (LER)
(T-6 E6), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by intemet LICENSE EVENT R T (LER) e-mail to bjsl @nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202 (3150-0104), Office of Management and Budget, Washington, DC 20503. If a (See reverse for required number of means used to impose information collection does not display a currently valid OMB control digits/characters for each block) number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
FACILITY NAME (1)
DOCKET NUMBER (2)
PAGE (3)
Kewaunee Nuclear Power Plant 05000305 1 of 5 TITLE (4)
Unanalyzed Condition: Strong Pump - Weak Pump Interaction Between Component Cooling Water Pumps EVENT DATE (5)
LER NUMBER (6)
REPORT DATE (7)
OTHER FACILITIES INVOLVED (8)
FACILITY NAME DOCKET NUMBER SEQUENTIAL REV MO DAY YEAR YEAR NUMBER NO MO DAY YEAR 01 10 2002 2002 001 00 03 11 2002 FACILITY NAME DOCKETNUMBER OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 9: (Check all that apply) (11)
MODE (9)
N 20.2201(b) 20.2203(a)(3)(ii)
X 50.73(a)(2)(ii)(B) 50.73(a)(2)(ix)(A)
POWER 100 20.2201 (d) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(x)
LEVEL (10) 20.2203(a)(1) 50.36(c)(1)(i)(A) 50.73(a)(2)(iv)(A) 73.71 (a)(4) 20.2203(a)(2)(i) 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(5) 20.2203(a)(2)(ii) 50.36(c)(2) 50.73(a)(2)(v)(B)
OTHER 50.73(a)(2)(v)(C)
_ Specify in Abstract below or in 20.2203(a)(2)(iii) 50.46(a)(3)(ii) 50.73(a)(2)(v)(N) 0 t3 044 00; ti;00 0
10
_20.2203(a)(2)(iv) 50.73(a)(2)(i)(B)
_50.73(a)(2)(v)(D)
________________________j0000000000Xt000 20.2203(a)(2)(v) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii)()
20.2203(a)(2)(vi) 50.73(a)(2)(i)(C) 50.73(a)(2)(viii)(
__________________________0X_
20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(B)
_______i:______________________
LICENSEE CONTACT FOR THIS LER (12)
NAME TELEPHONE NUMBER (Include Area Code)
Anthony David Bolyen - Compliance J
(920) 388-8864 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)
MANU-REPORTABLE l
i MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX I
CAUSE
SYSTEM COMPONENT FA CTURER TO EPIX SUPPLEMENTAL REPORT EXPECTED (14)
EXPECTED MONTH DAY YEAR YES (If yes, complete EXPECTED SUBMISSION DATE).
X NO SUBMISSION II IDATE (15)
ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)
On 1/1 0/02, Nuclear Management Company (NMC) personnel determined that under certain operating conditions, the 'A' Component Cooling Water (CCW) pump discharge capacity overpowered the 'B' CCW pump. Consequently, with both pumps operating in parallel, the 'B' CCW pump was "dead-headed" against the unopened discharge check valve. At 1601 CST, on 1/1 0/02, NMC conservatively reported this condition to the Nuclear Regulatory Commission (NRC) in accordance with 1 OCFR50.72(b)(3)(ii)(B) as a condition that results in the plant being in an unanalyzed condition that significantly degrades plant safety.
The design of the CCW system has been in place since original plant construction. It is apparent that the original designers failed to realize the potential design interaction from both pumps automatically starting on a Safety Injection signal or loss of offsite power condition. Additionally, NRC Bulletin 88-04 provided industry notice of the potential of this pump design interaction under minimum flow conditions. However, plant engineering staff failed to recognize the vulnerability of parallel pump operation under moderate system flow requirements. This condition was assessed with an incremental core damage frequency of 8.5E-7, which corresponds to a very low risk significance. NMC plans to implement a design change to prevent this pump-to-pump interaction. Kewaunee's root cause evaluation continues. Further cause determination efforts may reveal the need for additional administrative corrective actions.
- - U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE (3)
YEAR ISEQUENTIAL REVISION Kewaunee Nuclear Power Plant 05000305 Y
NUMBER NUMBER 2 of 5 2002 001 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
DESCRIPTION
On January 10, 2002, while the plant was in normal operation at 100 percent power, Nuclear Management Company (NMC) personnel determined that under certain operating conditions, the 'A' Component Cooling Water (CCW) [CC] pump [P] discharge capacity overpowered the 'B' CCW pump. Consequently, with both pumps operating in parallel, the 'B' CCW pump was "dead-headed" against the unopened discharge check valve M, CC-3A. Because this condition could have eventually caused the "dead-headed" pump to fail, a single failure in the opposite, or strong, train would have resulted in a complete loss of CCW. Thus, NMC concluded that this condition could have impacted the ability of safety related components to perform their intended function.
As stated in the Kewaunee Updated Safety Analysis Report (USAR) Section 9.3, the CCW system consists of two CCW pumps, two CCW heat exchangers [HX], a CCW surge tank [TK], cooling lines to various components to be cooled, and associated piping, valves, and instrumentation. CCW piping to various components is arranged in parallel flow circuits. During normal operation, the CCW pumps and heat exchangers are operated as needed to accommodate the heat removal loads. One pump and one heat exchanger can provide 100% heat removal capability during normal operation. Two pumps and two heat exchangers are used to remove the residual and sensible heat during plant shutdown. If one of the pumps or one of the heat exchangers is not operative, safe shutdown of the plant is not affected; however, the time for cool-down is extended.
Each CCW pump discharges through a check valve and a discharge isolation valve into a common header (see Figure 1). At Kewaunee, both CCW pumps automatically start on a Safety Injection (SI) signal or a loss of offsite power. Because of the common header, if the discharge head capacity of the operating CCW pump is greater than that of the stand-by CCW pump, the stand-by pump's discharge check valve may not open when the stand-by pump starts. At higher CCW flow rates, both pumps will share the load and this "dead-heading" condition is not a concern.
At 1601 CST, on January 10, 2002, NMC conservatively reported this condition to the NRC (EN 38621) in accordance with 1 OCFR50.72(b)(3)(ii)(B) as a condition that results in the plant being in an unanalyzed condition that significantly degrades plant safety.
CAUSE OF THE EVENT
The design of the CCW system has been in place since original plant construction. It is apparent that the original designers failed to realize this potential design interaction. Although single pump testing was performed following the system's installation and is routine to date, dual pump testing was not performed to assure pump performance under low to moderate flow conditions.
NRC Bulletin 88-04 provided additional insights to pump-to-pump interaction. However, the Kewaunee response to Bulletin 88-04 did not identify this issue as being a concern with the Kewaunee CCW system.
(see Additional Information).
Kewaunee is continuing to complete a full root cause evaluation. Efforts to date show the need to modify the system design to assure minimum flow requirements for the pumps is always available. However, because of the time that the condition has existed, the root cause or causes are more difficult to determine.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1l DOCKET NUMBER (2)
LER NUMER (6)
AGE 3 (A
SEQUENTIAL REVISION Kewaunee Nuclear Power Plant 05000305 YEAR NUMBER NUMBER 3 of 5 2002 001 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
ANALYSIS OF THE EVENT
NMC has evaluated the risk-insights from the site-specific Probabilistic Risk Assessment (PRA). As a result of this evaluation, this condition was assessed with an incremental core damage frequency of 8.5E-7, which corresponds to a very low risk significance.
This design issue alone did not result in redundant trains of CCW being inoperable. Therefore, this condition is not reportable as a Safety System Functional Failure under I OCFR50.73(a)(2)(v). However, because this event did result in one train of CCW being considered inoperable, it is being reported in accordance with 10CFR50.73(a)(2)(ii)(B) as a unanalyzed condition that significantly degraded plant safety.
CORRECTIVE ACTIONS
NMC has completed the following corrective actions:
Preliminary reviews of the other systems called out in Kewaunee's response to Bulletin 88-04 show adequate mini-flows are assured and no dead heading concerns.
NMC implemented compensatory administrative controls requiring Operators to stop one CCW pump in the event that the stand-by CCW pump starts during low CCW system demand.
NMC initiated a root cause evaluation to determine why this condition exists and why it was not recognized sooner.
NMC plans to perform the following corrective actions:
NMC plans to perform further reviews of plant systems to ensure this condition does not exist elsewhere.
NMC plans to implement a design change to prevent this pump-to-pump interaction.
Should the root cause evaluation determine the need for additional administrative corrective actions, NMC will include them as additional corrective actions according to the Kewaunee corrective action program.
SIMILAR EVENTS
There have been no similar events within the last three years.
ADDITIONAL INFORMATION
On May 5, 1988, the NRC issued Bulletin 88-04, "Potential Safety-Related Pump Loss". The purpose stated in the Bulletin was:
"The purpose of this bulletin is to investigate and correct as applicable two miniflow design concerns.
The first concern involved the potential for the dead-heading of one or more pumps in safety-related systems that have a miniflow line common to two or more pumps or other piping configurations that do not preclude pump-to-pump interaction during miniflow operation. The second concern pertained to whether or not the installed miniflow capacity is adequate for even a single pump in operation."U.S. NUCLEAR REGULATORY COMMISSION (1-200 1)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER 2 LER NUMBER (6)
PAGE (3)
YEAR ISEQUENTIAL IREVISION Kewaunee Nuclear Power Plant 05000305 l
I NUMBER 4of 5 2002 001 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
The Kewaunee response to NRC Bulletin 88-04 stated, in part, "The component cooling pumps do not have miniflow recirculation lines. System design and normal operating practices are such that the pumps are always supplying the main component cooling loads; therefore, recirculation flow to the pumps is not required, and pump-to-pump interaction is not a concern.
"The component cooling pumps do not have miniflow recirculation lines. System design and normal operating practices are such that when a pump is operating, it is sufficiently loaded to component cooling loads. Pump damage due to low flow conditions is not a concern for the component cooling pumps."
ENS notification 38621 provided on January 10, 2002 stated that the Kewaunee response to NRC Bulletin 88-04 "indicated that the CCW system was not vulnerable to this particular type of system failure." As such, the ENS notification provided the NRC with a report in accordance with I OCFR50.9. However, as described in the Bulletin, the interaction between the CCW pumps is not during miniflow recirculation operation, per se.
Rather, the interaction reported in this LER occurs under normal system steady state flow conditions which could be the same during the initial stages of an SI condition or a loss of offsite power. It is unclear whether this distinction was used during the review of NRC Bulletin 88-04, resulting in dismissing the CCW system from further evaluation of possible pump-to-pump interaction.
Under normal operating conditions, flow in the CCW system is around 1000 gpm. It seems that the evaluation for the response to the Bulletin did not recognize this as a low flow condition that could result in a dead-heading condition.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6)
PAGE 3 YE SEUENTIAL REVISION Kewaunee Nuclear Power Plant 05000305 YEAR SEQ NUMBER 5 of 5 2002 001 00 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
Figure 1: Simplified CCW Sketch U 0U 0
of I 0-WU c
afar: