Part 21 Report - 1998-121

 
 

ACCESSION #:  9803100298

                       LICENSEE EVENT REPORT (LER)



FACILITY NAME:  Point Beach Nuclear Plant, Unit 1         PAGE: 1 OF 5



DOCKET NUMBER:  05000266



TITLE:  Emergency Diesel Generator Air Start Motor Solenoid

        Valves Found with Springs not in Accordance with Design



EVENT DATE:  02/03/98   LER #:  98-008-00   REPORT DATE:  03/05/98



OTHER FACILITIES INVOLVED:  Unit 2                  DOCKET NO:  05000301



OPERATING MODE:  N   POWER LEVEL:  84



THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR

SECTION:

50.73(a)(2)(ii)



LICENSEE CONTACT FOR THIS LER:

NAME:  James Knorr, Regulation &            TELEPHONE:  (920) 755-6863

       Compliance Manager



COMPONENT FAILURE DESCRIPTION:

CAUSE:      SYSTEM:       COMPONENT:       MANUFACTURER:

REPORTABLE NPRDS:



SUPPLEMENTAL REPORT EXPECTED:  NO



ABSTRACT:



On January 26, 1998, with Unit 1 at 84 percent power and Unit 2 in cold

shutdown, a 10 CFR 21 notification was received from Engine Systems, Inc.

The letter discussed a defect with the air start solenoid valves used on

Emergency Diesel Generators (EDGs).  The solenoid valves do not meet the

minimum DC voltage requirements when inlet pressures below 200 psig are

applied to the valve.  Seven of the valves were sold to Wisconsin

Electric.  On February 3, 1998, the valves were found on all four EDGs at

Point Beach Nuclear Plant.  Calculations performed to assess available DC

voltage at the air start solenoid valves concluded that only one of the

EDGs (G03) had sufficient post-accident voltage.  Since G03 was only

connected to one of the safeguards buses, the plant was considered to be

outside the design basis.  The valves have been modified or replaced and

EDGs G02, and G04 have been returned to service.  G03 will be modified to

maintain similar design between air start systems.  G01 will be modified

as part of its overhaul effort.



END OF ABSTRACT



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Event Description:



Engine Systems, Inc.  (ESI) issued a 10 CFR Part 21 report on January 26,

1998 that notified Point Beach Nuclear Plant (PBNP) of a defect with the

air start solenoid valves [EK:FSV] used on the Emergency Diesel

Generators (EDGs)(EMD #9513134/Graham-White #712-015 and #712-065)

[EK:DG].  At the time of the notification, Unit 1 was operating at 84

percent power, and Unit 2 was in the cold shutdown condition.  The valves

do not meet the minimum DC voltage requirements when inlet pressures

below 200 psig are applied to the valve.  The list attached to the Part

21 report indicated that Wisconsin Electric (WE) had purchased seven (7)

of these valves.  The solenoid valve relies on system air pressure to

assist the coil in overcoming the force of the spring and thus operating

the valve plunger.  The original valve design assumed air pressure at 200

psig and therefore, a weaker spring than now supplied with the 275 psig

rated valve.  The EDG air start motor solenoid valves operate with air

pressure under the seat at a minimum of 165 psig for G01 and G02 (Train

A)and for G03 and G04 (Train B).  The valves are supplied with DC control

power [EJ].  The voltage at the valve is dependent on the battery load

during an accident scenario that uses the battery [EJ:BTRY] alone under

assumed accident load conditions.  In the case of these valves, the

recommended minimum voltage for the valves was 105 V DC.  Therefore, the

effect of control power voltages less than that recommended by the vendor

would not assure the valve would open due to the stronger spring in the

275 psig rated valve if the air pressure at the valve was less than 200

psig.  Initial calculations for the expected voltage at each air start

assuming accident DC load conditions resulted in voltages less than 105 V

DC for G01, G02 and G04.



Based upon the information supplied by the vendor of the airstart

solenoid valves for EDGs G01, G02 and G04, each was declared inoperable

at 2030 CST on February 3, 1998.  Since "03 was aligned to supply power

to only a single safeguards bus (1A06 - Train B vital power), the plant

was in a condition outside its Technical Specification requirements.

This condition lasted for approximately 30 minutes.  An operability

determination was prepared for G03.  A Wisconsin Electric calculation

dated 3/15/95 shows that terminal voltage in the G03 start circuit does

not fall below 108.7 V DC during the time when the air start solenoids

are required to operate in response to a design basis accident.  The

minimum calculated accident voltage available at the solenoid valves for

each of the remaining emergency diesels is, G01:92.93 V DC, G02:93.52 V

DC, G04:102.13 V DC.



G04 was removed from service to 2A06, and G03 was then aligned as the

standby emergency power supply to 1A06 and 2A06.  This action restored

standby emergency power for Train B and returned the plant to its

Limiting Condition for Operation (LCO) for a maximum of seven days by

Technical Specification 15.3.7.B.1.h.  G02 was declared inoperable but

considered available and aligned to supply 1A05 and 2A05 (Train A),



TEXT                                                          PAGE 3 OF 5



while G04 was declared inoperable but functional and removed from service

to 2A06 (Train B).



G01 was out of service for routine inspection when the Part 21 report was

received.  G02 was aligned to Train A buses 1A05 and 2A05 but was

declared inoperable.  Therefore, after G03 was tied to both 1A06 and 2A06

standby emergency power was considered to be in a seven (7) day limiting

condition of operation (LCO) per Technical Specification 15.3.7.B.1.h.



G01 air start solenoid valves are currently being worked in concert with

the G01 overhaul/inspection.  WO 9801735 documents work performed on the

solenoid valves.  This work will be completed prior to returning G01 to

service.



G02 air start solenoids were modified in accordance with the instructions

provided in 10CFR21-0077.  Work was performed per WO 9801736.  Both

valves were tested per criteria provided in the Part 21 report.  G02 was

subsequently returned to service to 1A05 and 2A05, and the LCO exited on

February 6, 1998.



G04 air start solenoid valves were modified in a similar fashion to G02,

except there was no LCO constraint since G03 was aligned to the Train B

buses.  Work was completed per WO 9801738, and G04 restored to service to

bus 2A06.



G03 air start solenoid valves will be modified via WO 9801737.  Since the

G03 valves satisfy the Part 21 voltage criteria, this WO is

discretionary.  The valves will be modified to be consistent with the

other EDGs, and the work will be scheduled with the next scheduled G03

inspection.



Component and System Description:



The Train A EDGs (G01 and G02) are automatically started by either one of

two pairs of air motors.  Each EDG has its own independent starting

system including two banks of three air storage tanks fed by two air

compressor systems.  Each bank of air receivers has sufficient storage to

crank the engine five times for the normal cranking duration of three

seconds.  The starting system is completely redundant for each EDG.



Starting air for each Train A EDG is admitted from the storage tanks at a

nominal working pressure of 175 psig to the starting systems through the

subject solenoid valves.



The control voltage for the air start system is backed up by a manually

switched 125 V DC power supply for the alternate station battery.



TEXT                                                          PAGE 4 OF 5



The Train B emergency diesels are automatically started by two pairs of

air motors.  Each bank Unit has its own independent starting system,

including two banks of two air storage tanks and two compressors.  Each

bank of air receivers has sufficient storage to crank the engine five

times for the normal cranking duration of five seconds.  The starting

system is completely redundant for each diesel generator.



Starting air for each Train B EDG is admitted from the storage tanks to

the starting systems through the subject solenoid valves through a 200

psi pressure regulator.



The control voltage for the diesel starting system is backed up by a

manually switched 125 VDC power supply from an alternate station battery.



Cause:



The cause of the event is the use of a 275 psig solenoid valve which does

not meet the minimum DC voltage available during an accident relying on

the station batteries for control power.  This deficiency was reported to

the Commission via a 10 CFR Part 21 notification by Engine Systems, Inc.

Report No. 10CFR21-0077, on January 22, 1998.  Wisconsin Electric

received notification as of January 26, 1998 and discovered the valves

installed on the EDGs on February 3, 1998.



Corrective Actions:



1.   G02 start solenoids were modified in accordance with the

     instructions provided in the Engine Systems, Inc.  Report No.

     10CFR21-0077.  Work was performed per WO 9801736.  Both valves were

     tested per criteria provided in the Part 21 report.  G02 was

     subsequently returned to service to 1A05 and 2A05, and the LCO was

     exited on February 6, 1998.



2.   G04 solenoid valves were modified in a similar fashion to G02,

     except there was no LCO constraint since G03 was aligned to the

     Train B buses.  Work was completed per WO 9801738, and G04 aligned

     to bus 2A06.



3.   G03 solenoid valves will be modified to ensure that the four EDGs

     remain the same in this respect during its next scheduled

     inspection.



4.   G01 solenoid valves are currently being worked in concert with the

     G01 overhaul/inspection.  WO 9801735 documents work performed on the

     solenoid valves.  This work will be completed prior to G01 being

     returned to service from its presently ongoing overhaul outage.



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Reportability



On February 3, 1998 at 2130 CST a notification to Commission was made in

accordance with 10 CFR 50.72(b)(1)(ii)(B) at 2130, "Any event or

condition that resulted in the condition of the nuclear plant, including

its principal safety barriers, being seriously degraded; or that resulted

in the nuclear power plant being in a condition that was outside the

design basis of the plant." This report is being filed in accordance with

10 CFR 50.73(a)(2)(ii)(B), "Any event or condition that resulted in the

condition of the nuclear power plant being ... in a condition that was

outside the design basis of the plant."



Safety Assessment:



Based upon calculation, the DC voltages reached during an accident would

have resulted in voltages less than the 105 V DC which has been concluded

to be the acceptable limit at which the valve would work with a high

degree of assurance.  The air pressures under the valve seat assumed in

the vendor testing of the 275 psig rated valves were as low as 125 psig.

The lowest pressure allowed for the EDGs is 165 psig.  The valves were

modified in accordance with the Part 21 recommendations and tested

satisfactorily at 100 psig and 90 V DC.  Therefore, the diesels would be

expected to start with voltages less than the 105 V DC.



Similar Occurrences:



LER            Description



266/98-006-00  TDAFWP Low Suction Pressure Trip (Seismic) outside Design

               Basis



System and Component Identifiers



The Energy Industry Identification System component function identifier

for each component or system referred to in this Licensee Event Report

are designated as [EIIS System Code:Component Identifier}



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