05000249/LER-2004-001, Hearing - Entergy Exhibit 14, LER 2004-001-00, Dresden, Unit 3 Automatic Scram During Testing of the Main Turbine Master Trip Solenoid Valves
ML062640099 | |
Person / Time | |
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Site: | Dresden, Vermont Yankee ![]() |
Issue date: | 03/24/2004 |
From: | Bost D Exelon Generation Co, Exelon Nuclear |
To: | Document Control Desk, NRC/SECY |
Byrdsong A T | |
References | |
50-271-OLA, Entergy-Licensee-14, RAS 12264, SVPLTR# 04-0009 LER 04-001-00 | |
Download: ML062640099 (5) | |
Event date: | |
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Report date: | |
2492004001R00 - NRC Website | |
text
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Exelon Generation Dresden Generating Station 6500 North Dresden Road Morris. IL 60450-976S Tel I15-942-2920 www.exeloncorp.com Nuclear 10 CFR 50.73 DOCKET NUMBER PROD. & UTIL FAO.
March 24, 2004 I
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SVPLTR # 04-0009 C_'
U. S. Nuclear Regulatory Commission C
ATTN: Do.cument Control Desk
- - _WashinrgtorGn-DC-20555-0001 Dresden Nuclear' Power Station, Unit 3 Facility Operating License No. DRP-25 NRC Docket NO. 50-249 La) mN Cc-)
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Subject Licensee Event Report 2004-001-00, "Unit 3 Automatic Scram During Testing of the Main Turbine Master Trip Solenoid Valves" Enclosed is Licensee Event Report 2004-001-00, "Unit 3 Automatic Scram During Testing of the Main Turbine Master Trip Solenoid Valves." for Dresden Nuclear Power Station. This event is being reported in accordance with 10 CFR 50.73(a)(2XIv)(A), "Any event or condition that resulted In manual or automatic actuation of any of the systems listed In paragraph (aX2)(iv)(B) of this section."
Should you have any questions concerning this report, please contact Jeff Hansen, Regulatory Assurance Manager, at (815) 416-2800.
Respectfully, DannyGQ2ost Site Vice President Dresden Nuclear Power Station Enclosure.
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Interveor_____
NRC Staff Other cc:
Regional Administrator - NRC Region III NRC Senior Resident Inspector - Dresden Nuclear Power Station.
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- 3. PAGE Dresden Nuclear Power Station Unit 3 05000249 101`4 4.TITLE Unit 3 Automatic Scram During Testing of the Main Turbine Master Trip Solenoid Valves
- 5. EVENT DATE L. LER NUMBER
- 7. REPORT DATE LO~THER FACILITIES INVOLVED 0N R
FACILITY NAME DOCKET NUMBER MO DAY YEAR YEAR
~
MO AYEAR N/A N/A I
FACILITY NAME I OCKETiNUMBER 01 24 2004 2004 - 001-00 03 24 2004 N/A N/A
- 9. OPERATING 111.
THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 0 CFR 1: (Check 0ll that pply
- - MODE 1
20.2201(b) 20.2203(aY3)ii)
- - 50.73(aX2)(ri)(B) 50.73(a)(2XIxXA)
- 10. POWER 120.2201(d) 20.2203(aX4) 50.73(a)2)(111) 50.73(aX2Xx)
LEVEL 096
- 20.2203(aX1) 50.36(cX1)(l)(A)
X 50.73(a)(2p A A
73.71(a)4)"
- =...;,,r.*
20.2203(a)(2)(1) 6 0.36{c)(1)(11)(A) 50.73(02)W2vA)
- 73.71(aX5)
§ 120.2203(a)(2ff,)
50.36(cX)2) 50.?3(aX2XvXB)
OTHER Specify InAstract below orkIn
,..20.2203(a)(2)(0ii1)
S0.48(aX3)(I) 50.73(aX2XvXC)
Abstract
On January 24, 2004, at 0037 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br /> (CST), with Unit 3 at 96 percent power In Mode 1, an automatic scram occurred while performing the weekly surveillance of the Main Turbine Master Trip Solenoid Valves. The suNveillance testing was performed in accordance with procedure DOS 5600-02, "Periodic Main Turbine, EHC and Generator Tests." The event was caused by a malfunction of the Main Turbine Master Trip Solenoid Valves, which resulted in the depressurizatlon of the Emergency Trip Supply hydraulic header and the resulting momentary closure of the Main Turbine Stop Valves below 90 percent full open.. The Reactor Protection System actuated as a result of the Main Turbine Stop Valve position and, as designed, automatically scrammed the reactor. The plant responded as expected to the automatic scram.
The root cause of the malfunction of the Main Turbine Master Trip Solenoid Valves was attributed to an improperly designed position switch rod and its associated housing by the Original Equipment Manufacturer, General Electric. The corrective actions to prevent reoccurrence are to replace the Main Turbine Master Trip Solenoid Valves with valves of a different design.
The safety significance of this event was minimal. All control rods fully inserted and all systems responded as expected to the automatic scram. There were no subsequent major equipment malfunctions.
bm r. NARRATIVE (It more space Is required, use Dresden Nuclear Power Station Unit 3 isa General Electric Company Boiling Water Reactor with a licensed maximum power level of 2957 megawatts thermal. The Energy Industry Identification System codes used in the text are Identified as
'P091.
A.
Plant Conditions Prior to Event:
Unit: 03 Event Date: 01-24-2004 Event Time: 0037 CST Reactor Mode: I Mode Name: Power Operation Power Level: 96 percent Reactor Coolant System Pressure: 1000 pslg B.
Description of Event
Dresden Nuclear Power Station (Dresden) and other Exelon stations have been experiencing performance Issues with their Main Turbine Master Trip Solenoid Valves (MTSVs) [TG] (SOL]. The cause of the poor solenoid performance was determined to be a "silting" phenomenon. General Electric (GE), the Original Equipment Manufacturer, wasrequested to evaluate the "siltingr condition and find an alternate design to improve the solenoid performance. GE responded to this request by proposing the use of poppet solenoid MTSVs to replace the
'existing spool solenoid MTSVs. GE Indicated that, unlike the spool valve, a poppet valve Is not prone to stick due to its Inherent design. The poppet solenoid valve has a line-contact on its seating surface verses a sliding surface contact with tight clearance tolerances on a spool solenoid valve.
GE successfully tested the poppet solenoid MTSVs. However, after completing the testing, GE modified the position switch on the original poppet solenoid valve assembly. This modification was done to eliminate the need of additional cables to power the position switch. The modified position switch was never tested on the test assembly. GE's evaluation concluded that the new poppet solenoid MTSV was a direct replacement for the currently used spool solenoid MTSV.
In September 2003, LaSalle County Station (LaSalle) was preparing for a Unit 2 outage and performed pre Installation testing of the poppet solenoid MTSVs. During pre-installation testing, LaSaile Identified that the position switch on the poppet valve assembly was not functioning. GE-suspected that the target area at the end of the switch rod was too small for It to function properly and decided to Increase the target area of the switch.
LaSalle returned the poppet solenoid MTSVs for switch modification and the poppet solenoid MTSVs were not installed.
In October 2003, Dresden performed pre-installation testing on the poppet solenoid MTSVs and found that the limit switch was still not functioning properly, even after the target area on the rod end had been Increased based on the LaSalle experience. Further Investigation revealed that the switch adapter material should have been stainless steel Instead of carbon steel. GE.agreed to make the adapter material change but additional testing following the change by GE was not performed.
On October 21,2003, Dresden Unit 2 was In a refueling outage and the MTSVs were replaced with the poppet solenoid MTSVs. Post maintenance testing was performed satisfactorily without any problems.
On November 18, 2003, during weekly testing on Unit 3 per procedure DOS 5600-02. *Periodic Main Turbine, EHC and Generator Tests," MTSV WA failed to trip. 'The cause of this MTSV failure to trip was determined to be "sllting.u Based on this, Dresden engineering recommended that the Unit 3 MTSVs be replaced with poppet solenoid MTSVs during the upcoming maintenance outage in December 2003.
(It more space Is required, use additional copies of (it more space Is required, use additional copies of NRC Form 366A)
MTSVs design momentarily ties the pressure end drain ports together. If the ports are tied together for a sufficient time, the Emergency Trip Supply hydraulic header will depressurize. One of the poppet solenoid MTSVs removed from Dresden Unit 3 had a response time of 200 milliseconds.
An optical microscope Inspection of the poppet solenoid MTSVs did not reveal any foreign material around the valve seat area. Additionally, the inspection found no Indication of tearing or deterioration of the Internal o-rings and backing rings.
The overall visual Inspection revealed that the Internal position switch rod was bent on all four valves.
Further examination revealed that the target could catch on threads within the switch housing. This defect would cause the observed delay in the response time of the valves; GE determined that the damage to the Internal components most probably occurred during manufacturing.
The high response time of the poppet valves onr Unit 3 caused the pressure and drain ports to be tied together for a sufficient time to cause the Emergency Trip Supply hydraulic header to depressurize and resulted In the momentary closure of the Main Turbine Stop Valves below 90 percent full open.
D.
Safety Analysis
The safety significance of this event was minimal. All control rods fully Inserted and all systems responded as expected to the automatic scram. There were no subsequent major equipment malfunctions. Therefore, the consequences of this event had minimal impact on the health and safety of the public and reactor safety.
E.
Corrective Actions
The poppet solenoid MTSVs were replaced with spool solenoid MTSVs on Dresden Unit 3.
The poppet solenoid MTSVs will be replaced with the spool solenoid MTSVs during a scheduled maintenance outage on Dresden Unit 2.
An engineering evaluation was completed to permit the suspension of MTSV testing on Unit 2 until the poppet solenoid MTSVs are replaced with spool solenoid MTSVs.
F.
Previous Occurrences
A review of Dresden Nuclear Power Station Licensee Event Reports (LERs) and operating experience over the previous five years did not find any similar MTSV occurrences.
G.
Component Failure Data
GE poppet solenoid MTSV Part Number 378A3294P0001