05000321/LER-2007-002, Regarding ATTS Card Failure Results in High Pressure Coolant Injection System Isolation
| ML071280115 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 05/07/2007 |
| From: | Madison D Southern Nuclear Operating Co |
| To: | Document Control Desk, Plant Licensing Branch III-2 |
| References | |
| NL-07-0921 LER 07-002-00 | |
| Download: ML071280115 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3212007002R00 - NRC Website | |
text
D. R. Madison (Drnaisl
=rn Nuclrrr Wce President - Hatch Opmrting Company, lnc.
Plant Edwin I. Hatch 11028 Hatch Parkway, North Baxley, Georgia 31513 Tel912.537.5859 Fax 912.366.2077 May 7,2007 Docket Nos.:
50-321 Enrw to Serve Your World' U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant - Unit 1 Licensee Event Report ATI'S Card Failure Results in High Pressure Coolant Iniection Svstem Isolation Ladies and Gentlemen:
In accordance with the requirements of 10 CFR 50e73(a)(2)(v)(B), Southern Nuclear Operating Company is submitting the enclosed Licensee Event Report (LER) concerning the failure of an Analog Transmitter Trip System trip unit which resulted in the isolation of the High Pressure Injection System.
This letter contains no NRC commitments. If you have any questions, please advise.
Sincerely,
. R. Madiso Vice President - Hatch Edwin I. Hatch Nuclear Plant 1 1028 Hatch Parkway North Baxley, GA 3 15 13 Enclosure: LER 50-32 112007-002 cc:
Southern Nuclear Omrating Com~anv Mr. J. T. Gasser, Executive Vice President Mr. D. R. Madison., Vice President - Hatch Mr. D. H. Jones, Vice President -.Engineering RTYPE: CHAO2.004 U. S. Nuclear Regulato~ Commission Dr. W. D. Travers, Regional Administrator Mr. R. E. Martin, NRR Project Manager - Hatch Mr. J. A. Hickey, Senior Resident Inspector - Hatch
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- 1. C r n I U I Y Edwin I. Hatch Nuclear Plant Unit 1 On March 7,2007 at 850 pm EST Hatch Unit 1 was in the run mode at approximately 100 percent of rated thermal power. At that tim during the performance of the Analog Transmitter Trip System (ATI'S) panel Functional Test and Calibration procedure the High Pressure Coolant Injection (HPCI) inboard isolation valve 1E41-F002 closed. The HPCI system was declared inoperable and the appropriate Technical Specifications Required Action Statement was entered.
2DOCllllNUYbEn I
a. C M E 05000321 1 OF4 Troubleshooting of the HPCI isolation logic circuit was performed. The most probable cause of the valve closure was determined to be a faulty ATTS card, 1E41-N670A. The board was inspected and evidence of chipped insulation and fractured solder connections of the board's components were found. These faults contributed to an erroneous trip signal being sent, resulting in the valve closure.
The failed ATI'S card and an associated A'ITS card were replaced. In addition, related AlTS Agastat relays were replaced to avoid age-related problems or failures.
NRC FORM S8M U.S. NUCLEAR REQULATORY COMMlSSlON u-m)
LICENSEE EVENT REPORT (LER)
- 1. FmUTY NAME 11 2 DOCKET 1
- 6. LER NWB(IR I
3.P-Edwin I. Hatch Nuclear Plant - Unit 1 05000321 I
I B
- 17. NARRATIVE (If m ~ r e space ip r~qrdrred, additbnaI oqpies of NRC F o
~
386.4)
I PJ ANT AND SYSTEM IDENTIFICATION General Electric - Boiling Water Reactor Energy Industry Identification System codes appear in the text as (Ens Code XX).
JXXRIPTION OF EVENT On March 7,2007 at 8:50 pm EST Hatch Unit 1 was in the run mode at approximately 100 percent of rated thermal power. At that time during the performance of the Analog Transmitter Trip System (ATTS) panel Functional Test and Calibration procedure the High Pressure Coolant Injection (HPCI) inboard isolation valve 1E41-F002 closed. The HPCI system was declared inoperable and the appropriate Technical Specifications Required Action Statement was entered. Troubleshooting of the HPCI isolation logic circuit was performed. The most probable cause of the valve closure was determined to be a faulty A'ITS card.
1E41-N670A. The failed A'ITS card and an associated ATTS card were replaced. In addition, related ATTS Agastat relays were replaced to avoid age-related problems or failures.
The circuitry was functionally tested and HPCI was declared operable on March 10,2007, at 4:25 p.m. EST I
CAUSEOFEVENT The most probable cause of the HPCI isolation was an erroneous trip signal being sent by ATTS card 1E41-N670A. 1B1-N670A serves as the AlTS master trip unit (MTU) for the 'A' channel of the HPCI area high temperature isolation, which causes closure of the inboard isolation valve, 1B1-F002.
As a part of the investigation, all inputs feeding into the HPCI 1E41-F002 closure logic were investigated.
There are four different inputs that energize the applicable relays to initiate the HPCI isolation valve closure signal. Ten percent of the Unit 1 ATT'S cards and ten percent of the Unit 2 A'ITS cards have been inspected, with no other card damage noted. The inspections were initiated in 2006 to look for "tin whiskers". These inspections would identify the type of damage seen on the two E41 ATTS cards described in this LER. In addition the recent failure rate of ATTS cards is approximately 0.3 percent per year. It is concluded that the A'ITS cards, on a whole, are highly reliable.
Visual inspections of ATTS cards IB1-N670A and penetration room high temperature MTU 1E41-N671A revealed damage to components on the cards. For example, components found on card 1E41-N670A had fractured solder connections, and chipped insulation. Furthermore. relays 1E21-K36 1C and 1E2 1 -K362C, which are Agastat relays located in the logic circuitry downstream of 1E41-N670A and 1E41-N671A.
respectively, were bench-tested and noise was seen across the voltage signal of the relays. This disturbance is an early indication of aging.
I """'
LICENSEE EVENT REPORT (LER)
- 1. f ACUJTY NAME 2
DOCKEI' a LER NUMBER
- 3. PAQE Edwin I. Hatch Nuclear Plant - Unit 1 05000321 I
I
- 17. NARRATIVE ftf mom spec8 k requred, use addlfkml c o w d NRC Form 3&?A)
REP RTAB This event is reportable per 10 CFR 50.73 (a)(2)(v) because an event occurred in which the HPCI system, a single train safety system, was rendered inoperable.
The HPCI system consists of a steam turbinedriven pump and the necessary piping and valves to transfer water from the suppression pool or the condensate storage tank (EIIS Code KA) to the reactor vessel. The system is designed to inject water to the reactor vessel over a range of reactor pressures from 160 psig through full rated pressure. The HPCI system starts and injects automatically whenever low reactor water level or high drywell pressure indicates the possibility of an abnonnal loss of coolant inventory. The HPCI system in particular, is designed to replace lost reactor coolant inventory in cases where a small line break occurs which does not result in full depressurization of the reactor vessel.
The backup for the HPCI system is the Automatic Depressurization System (ADS) together with two low pressure injection systems: the Low Pressure Coolant Injection (LPCI, EIIS Code BO) system and the Core Spray (CS, EIlS Code BM) system. The CS system is composed of two independent, redundant, 100 percent capacity subsystems. Each subsystem consists of a motor driven pump. its own dedicated spray sparger located above the core, and piping and valves to transfer water from the suppression pool to the sparger.
Upon receipt of an initiation signal, the CS pumps in both subsystems start. Once ADS has reduced reactor pressure sufficiently, CS system flow begins.
LPCI is an operating mode of the Residual Heat Removal (EIIS Code BO) system. There are two independent, redundant, 100 percent capacity LPCI subsystems, each consisting of two motor driven pumps and piping and valves to transfer water from the suppression pool to the reactor vessel. Upon receipt of an initiation signal, all four LPCI pumps automatically start. Once ADS has reduced reactor pressure sufficiently, the LPCI flow to the reactor vessel begins.
ADS consists of 7 of the 11 Safety Relief Valves (SRV). It is designed to provide depressurization of the Reactor Coolant System during a small break loss of coolant accident (LOCA), if HPCI fails or is unable to maintain required water level in the Reactor Pressure Vessel (RPV). ADS operation reduces the RPV pressure to within the operating pressure range of the low pressure Emergency Core Cooling System subsystems (CS and LPCI), so that these subsystems can provide coolant inventory makeup.
In this event, the HPCI system was declared inoperable when the 1E41-F002 inboard isolation valve closed.
During the time the HPCI system was inoperable, the Reactor Core Isolation Cooling (RCIC, EIlS Code BN) system was available to inject high pressure water into the reactor vessel. Although not an emergency core cooling system the RCIC system is designed, maintained, and tested to the same standards and requirements as the HPCI system and therefore should reliably inject water into the reactor vessel, when required. Ifa break had exceeded the capacity of the RCIC system (400 gpm), the ADS was available to depressurize the reactor vessel to the point that either the Core Spray or LPCI systems could have been used to provide water to the reactor core. The capacity of one loop of the Core Spray system is equal to that of the HPCI system (4250 gpm, each); the capacity of one loop of the LPCI system is approximately three times that of the HPCI system. Therefore, any one of the four loops of the low pressure injection systems would have provided sufficient injection capacity for replacement of the HPCI flow.
EIIS System Code: BJ Reportable to E P K Yes Root Cause Code: X EIIS Component Code: PB NRC FORM 388A U.S. NUCLEAR REGULATORY COMMISSION (1.2Q01)
LICENSEE EVENT REPORT (LER)
- 1. FAClUTY NAME Edwin I. Hatch Nuclear Plant - Unit 1 2 DOCKET
- 6. LER NUMsER
- 3. PAOE 0500032 1
- 17. M T l V E (If more spclce Is requid, use additimal w88 of NRC Fom, 36M)
Based on this analysis, it is concluded that this event had no adverse impact on nuclear safety. This analysis is applicable to all power levels and operating modes in which a LOCA is postulated to occur.
CORRECTIVE ACTIONS
ATI'S cards 1E41-N671A and 1E41-N670A were replaced.
ATI'S Agastat relays 1E21A-K361C and lE21AK362C were replaced to avoid age-related problems or failures.
Inspection of all HPCI system AlTS cards will be performed during the next HPCI system outage. This will be tracked under the plant's Corrective Action Program.
Replacement of all ATTS Agastat relays is in progress and will be tracked under the plant's Corrective Action Program.
All A'ITS cards are now inspected prior to installation into the plant.
ADDlTIONAL INFORMATION Other Systems Affected: None
Failed Components Information
Master Parts List Number: 1E41 -N670A Manufacturer: General Electric Model Number: 184C5988G101 Type: Board, Printed Circuit Manufacturer Code: GO82 Commitment Information:
This report does not create any permanent licensing commitments.
Previous Similar Events
LER 2-2006-001 documents a similar event where the HPCI system was rendered inoperable due to the failure of an ATCS card.
NRC FORM 3OM (1-2001)