ML18059A682

LER 93-005-01:on 930720,discovered Both Emregency Diesel Generators Started After Receiving Undervoltage Signal Due to de-energization of Electrical Bus 1C.Caused by Lack of Vendor Information.Procedures revised.W/940204 Ltr

ML18059A682
Person / Time
Site:	Palisades
Issue date:	02/04/1994
From:	Hillman C, Slade G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-005, LER-93-5, NUDOCS 9402280061
Download: ML18059A682 (6)

Text

. consumers Power GB Slade General Manager POWERIN&

MICHl&AN'S PRO&RESS Palisades Nuclear Plant: 27780 Blue Star Memorial Highway, Covert. Ml 49043 February 4, 1994 Nuclear Regulatory Commissio~

Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT - LICENSEE EVENT REPORT 93-005 ENGINEERED SAFETY FEATURE ACTUATION - EMERGENCY DIESEL GENERATOR START DUE TO AN INADVERTENT LOSS OF POWER ,TO SAFEGUARDS BUS IC - SUPPLEMENTAL REPORT Lic~nsee Event Report (LER)93-005, Supplement 1, is attached . .This supplemental report includes the results of the multidis~iplinar~ review group's root ca~se analysis of this event. This information was also supplied to the NRC in our reply to the Notice of Violation (IR 93016), dated December 23' 1993.

This event was originally reported in accordance with 10 CFR 50.73(a)(2)(iv).

No further supplements to this LER are expected.

~~~~

Gerald B Slade Genera 1. Manager CC* Administrator~ Region Ill, USNRC NRC Resident Inspector - Palisades Attachment A CM5 ENERGY COMPANY

NRC Form 3118 U.S. NUCLEAR REGULATORY COMMISSION 111*831 APPROVED OMB NO. 3160-01Cl' EXPIRES: B/31186

.. LICENSEE EVENT REPORT (LERI FACILITY NAME 111 DOCKET NUMBER 121 PAGE 131 Palisades Plant 016101010121615 1 I oF Io 1 s TITLE 141 ENGLNEERED SAFETY FEATURE ACTUATION - EMERGENCY DIESEL GENERATOR START DUE TO AN TNAnVRRTRNT T.nss 01" POtJRR TO SAl<'Rr.ITARns RTlS 1 r. - SITPPTRMRN'T'AT RJ<'.PORT EVENT DATE 161 LER NUMBER 1111 REPORT DATE 1111 OTHER FACILITIES INVOLVED IBI MONTH DAY YEAR YEAR

SEQUENTIAL NUMBER

(> REVISION NUMBER MONTH DAY YEAR FACILITY NAMES N/A 0161010101 I

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60.731111211viiillAI 60.731111211viiillBI 60.731*11211xl below ~ in Text, NRC Form 388AI LICENSEE CONTACT FOR THIS LER 1121 NAME TELEPHONE NUMBER Cris T. Hillman. Staff Licensing Engineer sARrA,Cr~ I7 I 6 I 4 I - I 8 I 9 I , I 3 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 1131 MANUFAC* REPORTABLE *.*:*::.'.:,::.-. MANUFAC* REPORTABLE CAUSE SYSTEM COMPONENT TUR ER TO NPROS *:'.:{*:,::*:* CAUSE SYSTEM COMPONENT TUR ER TO NPRDS I I I .1 I I I I I I I I I I

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I I I I I I I I I I I I I I SUPPLEMENTAL REPORT EXPECTED 1141 ***************************** MONTH DAY YEAR EXPECTED

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ABSTRACT ILJmit ID 1400 - *

• i.e., -inMr.f>t rfftHn hi NO ling>>--* typewrittM line1I 1181 SUBMISSION DATE 1161 I I I Abstract On July 20, 1993, at 1743 hours0.0202 days <br />0.484 hours <br />0.00288 weeks <br />6.632115e-4 months <br />, both ~mergency diesel generators started after receiving an undervoltage signal due to the de-energization of electrical Bus IC.

Simultaneous with this inadvertent ESF actuation, a spare breaker was being i nsta 11 ed

. in the cubicle for the Start-up Transformer breaker. As the spare breaker was inserted into the Start-up Transformer cubicle, the Safeguards Transformer I-I feeder breaker opened, de-*energizing Bus IC. An undervoltage condition resulted which initiated an emergency diesel gerierator start. Shutdown cooling was not affected since safeguards electrical loads were being supplied by the opposite channel safeguards bus.

The cause of this event is attributable to inadequate design information.

The remaining corrective action for this event is developing a methodology for the I control of spare breakers.  ;

NRC Fotm 3811A U.S. NUCLEAR REGULATORY COMMISSION 19-831 APPROVED OMS NO. 3160-0104 EXPIRES: 8131/86 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant

- 0 I5 I0 I0 I0 I2 I5 I5 9 I3 - 0 I0I 5 - 0 I 1 0 I2 OF 0 I 5 EVENT DESCRIPTION On July 20, 1993, at 1743 hours0.0202 days <br />0.484 hours <br />0.00288 weeks <br />6.632115e-4 months <br />, both emergency diesel generators [EK] started after receiving an undervoltage signal due to the de-energization of electrical Bus IC. At the time of the event, the reactor was shutdown for refueling.* Simultaneous with this engineered safety feature (ESF) actuation (inadvertent diesel ~enerator start), an auxiliary operator was installing a spare breaker into the cubicle for the Start-up Transformer breaker 152-106 [EL; BKR] as part of scheduled breaker preventive I maintenance. As the spare breaker was inserted into the 152-106 cubicle, Safeguards Transformer 1-1 feeder breaker (152-105) opened, de-energizing Bus lC. An undervoltage condition resulted which initiated an emergency diesel generator start. The diesel generator breaker (152-107) for Bus lC closed re-energizing Bus lC, the Normal Shutdown Sequencer operated, and equipment required to start was re-started in proper sequence. I Shutdown cooling was not affected by this event since shutdown cooling electrical loads I were being supplied by Bus lD, the opposite channel safeguards bus.

Operators responded to the ESF actuation by entering Off Normal Operating (ONP)

Procedure ONP 2.1, "Loss of AC Power." The spare breaker that had been placed in breaker cubicle 152-106 was completely removed from the breaker cubicle. Safe~uards Transformer 1-1 feeder breaker 152-105 was inspected and verified to be in satisfactory condition, therefore, breaker.152-105 was closed and the electrical load was transferred from Diesel Generator 1-1 to the Safeguards Bus.

This event is reportable to the NRC in accordance with 10 CFR 50.73(a)(2)(iv) as an unplanned automatic actuation of an engineered safety feature.

CAUSE OF THE EVENT In response to electrical design deficiency issues identified in the plant corrective action system, a multidisciplinary review group was formed to review the deficiencies.

The group was tasked with identifying the root cause(s) for each of the deficiencies and to develop corrective action(s) to preclude similar conditions in the future. The multidisciplinary review group's report was discussed at the NRC Enforcement Conference on December 3, 1993. The *reconfiguration of the contacts of the auxiliary switch in the spare b~eaker was one of the topics in the report.

The multidisciplinary review group determined that three root causes were attributable to this event. The three root causes are:

1. Lack of vendor information on the spare breaker internals.

The vendor file provided conflicting information re~arding the functional similarity of the two breakers. The final disposition from the vendor was that the spare hreaker was " ... completely electrically and mechanically interchangeable ... " with the original breaker. An i..nternal wirin~

schematic of the spare breaker was not maintained in the vendor file.

NRC F0tm 3.88A U.S. NUCLEAR REGULATORY COMMISSION

" 18*831 APPROVED OMB NO. 3160-0104 EXPIRES: 8/31186 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 01 01 5 - 0 11 0I 3 OF 0 I5

2. The modification process was not used.

Initially, both the electrical repairpersons and the systems engineer questioned the physical dis-similarity between the spare breaker and the original breaker. The systems engineer researched the available vendor file information and concluded that the breakers were similar and that the contacts could be re-configured with no resulting change in equipment or system function. As previously stated, the re-configuration did result in a change in function, providing an undesirable fast transfer trip signal to breaker 152-105. Changing contact configuration should have been recognized as likely affecting equipment function and, therefore, should have prompted the initiation of the modification process ..

3. An invalid assumption was used that physical similarity represented functional similarity.

After reviewing the vendor documentation on the spare breaker, the systems engineer assumed the. vendor file information to be correct and complete, and proceeded to re-confi~ure the contacts to be similar to the contact configuration on the original breaker. The engineer should have recognized that vendor information does not necessarily represent a component's service when installed within a plant system.

ANALYSIS OF THE EVENT On July 9, 1993 the spare breaker for Start-up Transformer breaker 152-106 underwent inspection. During the breaker inspection, a modification to chan~e a "normally open" auxiliary switch contact to a "normally closed" contact connected in the manua 1 transfer I trip circuit was performed. When the spare 152-106 breaker was moved into the breaker cubicle beyond the "disconnect" position towards the "test" position, the "normally closed" auxiliary switch contact actuated the br.eaker transfer trip circuitry and opened I the Safeguards Transformer 1-1 feeder breaker 152-105. This actuation was in accordance with system design to minimize paralleling of two sources of AC power.

The spare breaker had been in service in the 152-105 breaker cubicle since the 1992 refueling outage. On June 25, 1993, the spare breaker was removed from the cubicle so that the original 152-105 breaker could be re-installed. Durin~ re-installation of the ori~inal 152-105 breaker, it was determined that the configuration of four of the auxiliary contacts was different between the original and spare breakers. The system engineer researched the function of the four contacts on the 152-105 breaker and concluded that they were all unused spare contacts and had no significance to the operation of the breaker; Based on his research and the desire to prevent future confusion with using the spare breaker, the system engineer-directed that the four auxiliary switch contacts on the spare breaker be re-configured to match the auxiliary I switch contacts of the original breaker. This re-configuration was performed on July 9, 1993. In particular, the fourth contact, which had been configured as "normally open" was changed to "normally closed." When the auxiliary contacts were reconfi~ured, it was thought that no additional controls were needed since the contacts in question were being changed ~o match the existing design. *

' NRC Fa<m 388A u.s~ NUCLEAR REGULATORY COMMISSION 18*831 APPROVED OMS NO. 3160-0104 EXPIRES: 8/31/86 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR . NUMBER NUMBER Palisades Plant 010 15 - 0 11 014 OF The or~ginal break~r was an Allis-Chalmers model MA 250B. The spare breaker, a Siemans-Allis model MA 250Cl, was purchased in 1984. The spare breaker was initially placed in I

a "QA hold" status by Quality Assurance receipt inspection because a vendor letter identified a difference in the use of a special internal switch and because a temp,orary tag attached to the breaker did not match the purchase order. Resolution of the 'QA I

hold" was based on review of vendor drawings and on a new vendor letter which stated that the model MA 250C breaker was "completely electrically and mechanically I interchangeable" with the model MA 250B breaker. The new vendor letter also stated that the previous vendor letter was not correct regarding the special internal switch.

The system engineer methodically reviewed the consequences of changing the auxiliary contact configuration and concluded that no circuit changes were being made, and that reconfiguration of the contacts would prevent future confusion when using the spare breaker. The four spare contacts are shown on Stored Energy Circuit Breaker schematic diagram E-129i Sheet 1 indicating that they are not used. The drawing does not indicate that a specia limit switch is also used. The contact from the special limit switch is identified on the schematic diagrams for the Station Power Transformer Incoming Breakers (E-131, Sheet 1) and Start-up Transformer Incoming Breakers (E-132, Sheet 1). These schematics were reviewed while determining the usage of the auxiliary contacts. The system engineer knew of the existence and use of the special limit switch in the installed breakers, but was not aware that the spare breaker used an auxiliary switch contact instead of the special limit switch, to perform the same function. Furthermore, there were no drawin~s in the vendor file for the internal wiring of the spare breaker which would have indicated the use of the auxiliary switch contact as opposed to the special limit switch to affect the transfer trip function. I CORRECTIVE ACTION The following corrective actions have been taken and .were described in reply to Notice of Violation,. NRC Inspection Report 93026.

I

1. Systems Engineers, Design Engineers, Procurement fngineers, and Chemistry Department Engineers were trained on the lessons learned from this event and the other events reviewed by the multidisciplinary review group. Emphasis was on the common causes of the event and corrective actions. A memo was also issued specific to* this event to-reiterate the lessons learned which are: assumptions must be verified; testing must be comprehensive and verify the intended result (additional testing may have detected the functional difference of the spare breaker); vendor information was not available in the vendor file, and; the design control process was not used. *

2. An electrical schematic diagram for the spare breaker*has been obtained, reviewed, and added to the vendor file. An expectation has also been re-emphasized that purchase orders for new equipment must specify that documentation also be supplied and that the supplied documentation be placed in the vendor file.

3. Unique equipment identification numbers have been assigned to all spare 4160/2400 volt breakers and have been added to the Equipment Data Base.

NRC Form 388A U.S. NUCLEAR REGULATORY COMMISSION 19*83)

APPROVED OMB NO. 3160-0104 EXPIRES: 8/31 /86 LICENSEE EVENT REPORT (LE.RI TEXT CONTINUATION FACILITY NAME 111 DOCKET NUMBER 121 LEA NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 01 o I s - o 11 0I5 OF 0 I 5

4. The contact configuration for the spare breaker has been returned to the as found, pre-event, configuration and verified to be the correct configuration for*use of the breaker. . .

The modification process is also being strengthened as a result of the multidisciplinary review group findings. Policy memos outlining the expectations for these reviews have been issued. These policy memos direct that facility changes and specification changes will undergo a multidisciplinary team review prior to release; that all specification changes be approved by an engineering manager (NECO or Systems Engineering) prior to their release for installation, and; that NECO will perform a technical review of all specification changes. Administrative procedures will be changed to incorporate these policies; however, in the interim, each engineering supervisor is expected to assure that the previously mentioned expectations are met before recommending approval of a facility change or specification change. Emphasis is on the quality of design change work. With respect to this event, the design change process will require multidisciplinary design review, including review of the intended test plans.

ADDITIONAL INFORMATION None