05000245/LER-1996-057, :on 961113,temporary Equipment Configuration Jeopardized Operability of 4 Kv Sys.Caused by Lack of Recognition of Interaction Potential of Breakers During Postulated Earthquake.Secured Breaker in Cubicle W/Hardware

:on 961113,temporary Equipment Configuration Jeopardized Operability of 4 Kv Sys.Caused by Lack of Recognition of Interaction Potential of Breakers During Postulated Earthquake.Secured Breaker in Cubicle W/Hardware

ML20132C026
Person / Time
Site:	Millstone
Issue date:	12/13/1996
From:	Robert Walpole NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20132C020	List: 05000245/LER-1996-057, :on 961113,temporary Equipment Configuration Jeopardized Operability of 4 Kv Sys.Caused by Lack of Recognition of Interaction Potential of Breakers During Postulated Earthquake.Secured Breaker in Cubicle W/Hardware
References
LER-96-057, LER-96-57, NUDOCS 9612180072
Download: ML20132C026 (3)

LER-1996-057, on 961113,temporary Equipment Configuration Jeopardized Operability of 4 Kv Sys.Caused by Lack of Recognition of Interaction Potential of Breakers During Postulated Earthquake.Secured Breaker in Cubicle W/Hardware

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(ii)
2451996057R00 - NRC Website

text

.

+

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150 0104 (4-95)

EXPlRES 04/30/98 NONAY Co$IECTIO ME LES 50 HRS f0TD NS hin"90 "MP# **P!.so Yo,=;' ofna,'4 ^=8

^

LICENSEE EVENT REPORT (LER)

I'm^u'? 'Oc"K"#o?n'#.v"40" ASS'!! ("E'&Y"R MnWM' ttaa!?l#1u"n"f. #MZ"oCP#%e"'*

(See reverse for required number of digits / Characters for eaCh block)

U.CluTY NAME (13 DOCKET NUMBER (2)

PAGE (3)

Millstone Nuclear Power Station Unit 1 05000245 1 of 3 TITLE (4)

Temporary Equipment Configuration Jeopardizing Operability of 4kV System EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR SEQUENTIAL REVISION MONTH DAY YEAR FACluTY NAME DOCILET NUMBER i

NUMBER 11 13 96 96 057 00 12 13 96 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Check one or more) (11)

MODE m N

20.2201(b) 20.2203(a)(2Hv) 50.73(a)(2)(i) 50.73(a)(2)(viii)

LEVEL (101 000 20.2203(aH1) 20.2203(aH3Hi)

X 50.73(a)(2)(ii>

50.73(a)(2)(x)

POWER 20.2203(aH2Hil 20.2203(aH3Hii) 50.73(aH210ii) 73.71 20.2203(a)(2)0i) 20.2203(a)(4) 50.73(a)(2)(iv)

OTHER 20.2203(a)(2Hiii) 50.36(CH1) 50.73(a)(2)(v) spec,f y in Abstract below or in NRC Form 366A 20.2203(aH2)(iv) 50.36(cH2) 50.73(a)(2Hvii)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER tinclude Area Codel Robert W. Walpole, MP1 Nuclear Licensing Manager (860)440-2191 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE I

TO NPRDS To NPRDS SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MONTH DAY YEAR SUBMISSION

[

YES NO (If yes, Complete EXPECTED SUBMISSION DATE).

ABSTRACT (Limit to 1400 spaces, i.e.. approximately 15 single-spaced typewritten lines) (16)

On November 13,1996, with the plant in the COLD SHUTDOWN condition, it was determined that the storage of racked out 4kV circuit breakers within their associated switchgear enclosure could jeopardize the operability of the associated switchgear. This condition resulted in the plant being outside of its design basis, and a prompt report was made pursuant to 10CFR50.72(b)(1)(ii)(B). This event is reportable pursuant to 10CFR50.73(a)(2)(ii) as a condition outside the desis 1 basis of the plant.

The cause of this event is the lack of recognition of the interaction potential of the 4kV breakers during a postulated l

certhquake. The displacement of the breaker within the cubicle could result in pounding loads to the side panels or j

tha cubicle door. This type of load can result in contact chatter of relays within the switchgear.

Thzre were no safety consequences as a result of this event.

The seismic interaction issue will be addressed and physical and/or procedural changes completed to preclude this intsraction prior to declaring 4kV system operable. Immediate corrective actions include use of existing hardware within the switchgear to secure the breaker within the cubicle.

9612180072 961213 PDR ADOCK 05000245 S

PDR

i j

=n kRC FORM 367A U.S. NUCLEAR REGULATORY COMMISSION 14 95)

LICENSEE EVENT REPORT (LER) 1 TEXT CONTINUATION FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL REVISION Millstone Nuclear Power Station Unit 1 05000245 NUMBER NUMBER 2 of 3 96 057 00 i

TEXT tif more space is required, use additional copies of NRC Form 366Al (17>

1.

Descrintion of Event On November 13, 1996, with the plant in the COLD SHUTDOWN condition, it was determined that the storage of racked out 4kV circuit breakers within their associated switchgear enclosure could jeopardize the operability of the associated switchgear. Currently, the 4kV system is not operable due to issues with the Emergency Diesel Generator and the Gas Turbine.

The breakers are racked out as part of equipment tag out for maintenance and other activities. While this condition is most prevalent during refueling activities, breakers are also racked down while the Unit is operating. The displacement of the breaker within the cubicle could result in pounding loads to the side panels or the cubicle door. The loadings which the breakers can impart to the switchgear are high frequency l

impact loads and are typical " seismic interaction" loads which can cause relays to chatter. This chatter i

could result in protective relays activating and locking out a particular bus, jeopardizing the operability of the loads on that bus.

This condition resulted in the plant being outside of its design basis, and a prompt report was made pursuant to 10CFR50.72(b)(1)(ii)(B) on November 13, 1996. There were no automatic or manually initiated safety system responses as a result of this event.

11.

Cause of Event

The cause of this event is the lack of recognition of the impact of this plant cond. tion on the operability of i

associated equipment. This configuration was not addressed in any design reviews of the switchgear and l

thus was not evaluated previously.

i til. Analysis of Event The plant condition associated with outatp conditions typically involves the maintenance of plant equipment.

In order to support these activities, equipment is tagged out and protective measures taken to preclude inadvertent operation. The protective measures include actions such as racking down of breakers to prevent the loads from being energized. Additionally, there is a small population of breakers which are normally racked down during plant operations. With the breakers in the racked down position, the mechanism which l

secures the breaker in the switchgear cubicle is disengaged and the breaker free to move within the cubicle.

i l

This unrestrained motion can impart loads into the switchgear causing inadvertent momentary change of i

state (chatter) possibly resulting in loss of the associated 4kV bus. This condition violates the design basis of the 4kV system which is required to be operable during a design basis earthquake. This condition is reportable pursuant to 10CFR50.73(a)(2)(ii).

There were no safety consequer1ces as a result of this event. The safety implications are that historically, in j

the worst cases scenario, there could have been a breaker racked out in each of the 4kV division rendering the whole 4kV system not operable. In the event that an earthquake had occurred with the switchgear in this configuration, there may have been damage to the cubicle containing the racked out breaker and spurious action of relays in adjacent cubicles. This spurious action could necessitate operator action to restore the affected bus. The cubicles which could have sustained any damage were not serving a critical i

function as the breakers were racked down and the loads not energized. The cubicles (4160-14E-13 " Diesel Generator to Bus 14E" and 4160-14D-16 "D to G Tie Breaker") which contain breakers normally racked down during power operation contain no door mounted relays.

~~

~

.~-

• i s ',

,U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

I TEXT CONTINUATION FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL ALVISION Millstone Nuclear Power Station Unit 1 05000245 NUMBER NUMBER 3 of 3 96 057 00 TEXT (11more space is required. use additional copies of NRC Form 366A) (17)

IV. Corrective Action

3 3

The breakers which are racked down will be secured within the cubicle to prevent movement using existing

[

hardware associated with the elevator mechanism by December 30, 1996. This immediate-corrective 4

measure will be reviewed to assess its suitability for a long term solution to the interaction concern.

I The 480v system has been reviewed and although breakers are also racked out for similar reasons to the f

4kV system, there is not the potential interaction issue due to the physical restraint of the breaker in the l

Test and Disconnect position.

Northeast Nuclear Energy Company will address the seismic interaction issue and provide appropriate permanent physical and/or procedural changes to preclude this interaction of racked down breakers prior to 1

declaring 4kV system operable.

V.

Additional Information

i

Similar Events

t There are no similar events involving seismic interactions on the 4kV system.

Manufacturer Data None.

i i

d i

i i

a 1

l 4

1 1

\\

j 4,

I