05000245/LER-1996-055, :on 961023,failure to Verify Emergency Diesel Air Start Requirements Occurred.Caused by Failure to Properly Identify & Verify Design Basis of EDG Air Start Sys.Procedures Revised

:on 961023,failure to Verify Emergency Diesel Air Start Requirements Occurred.Caused by Failure to Properly Identify & Verify Design Basis of EDG Air Start Sys.Procedures Revised

ML20134N072
Person / Time
Site:	Millstone
Issue date:	11/22/1996
From:	Robert Walpole NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20134N071	List: 05000245/LER-1996-055, :on 961023,failure to Verify Emergency Diesel Air Start Requirements Occurred.Caused by Failure to Properly Identify & Verify Design Basis of EDG Air Start Sys.Procedures Revised
References
LER-96-055, LER-96-55, NUDOCS 9611260156
Download: ML20134N072 (3)

LER-1996-055, on 961023,failure to Verify Emergency Diesel Air Start Requirements Occurred.Caused by Failure to Properly Identify & Verify Design Basis of EDG Air Start Sys.Procedures Revised

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)(ii) 10 CFR 50.73(a)(2)(iii) 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)(vii), Common Cause Inoperability
2451996055R00 - NRC Website

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

EXPIRES 04/30/98 m[oYA1 LECT R UE T: SO HS E O TED L'a"9o^"Ao"ul?# "*L*Tol'oMia" aina$A^N!

LICENSEE EVENT REPORT (LER) 15WeV2'L*M"#o*JtrW'c?"uJ"s'o'e 'nWes"&

Dinh^~".osEL"Rer!"r?Er3?s%lf"o;."8fsa" -

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

F ACIUTY NAME (1)

DOCKET NUMBER (2)

PAGE (3)

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

Failure To Verify The Emergency Diesel Air Start Requirements EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR SEQUENTIAL REVISION MONTH DAY YEAR FAc UTY NAME DOCKET NUMBER NUMBER 10 23 96 96 055 00 11 22 96 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 5: (Check one or more) (11)

MODE (9)

N 20.2201(b) 20.2203(a)(2)(v) 50.73(a)(2)(i) 50.73(a)(2)(viii)

LEVEL (10) 000 20.2203(a)(1) 20.2203(a)(3)(i)

X 50.73(a)(2)(ii) 50.73(a>(2><x)

POWER 20.2203(a)(2)(i) 20.2203(a)(3)(ii) 50.73(a)(2)(iii) 73.71 20.2203(a)(2)(ii) 20.2203(a)(4) 50.73(a)(2)(iv)

OTHER

, m

" ^

20.2203(a)(2)(iii) 50.36(c)(1) 50.73(a)(2)(v) specify in Abstract below

~

~

20.2203(a)(2)(iv) 50.36(c)(2) 50.73(a)(2)(vii)

LICENSEE CONTACT FOR THIS LER (12)

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

C/.USE SYSTEM COMPONENT MANUFACTURER REPORTABLE

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDs TO NPRDs 4,

SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MONTH DAY YEAR SUBMISSION YES g NO

""'~

(if yes, complete EXPECTED SUBMISSION DATE).

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

On October 23,1996, with the plant shutdown and the reactor in the COLD SHUTDOWN condition, an audit of op rating procedures identified that the acceptance criteria for air receiver pressure in the Emergency Diesel G nerator (EDG) air start system may not have been in accordance with the Updated Final Safety Analysis Report (UFSAR). On November 12,1996, investigation determined that the starting air system had been operated outside ths Plant's Design Basis, and therefore, it was reported pursuant to 10 CFR 50.72(b)(2)(i). There were no automatic not manually initiated safety system responses as a result of this event.

This LER is being reported in accordance with the requirements of 10 CFR 50.73(a)(2)(ii). The cause of this event is th3 failure to properly identify and verify the design basis of the EDG eir start system. The safety consequence is minimal since it was demonstrated during the original preoperational testing that at least two EDG starts had been available, while the safety analysis assumes that given one unsuccessful EDG start, the gas turbine is relied upon for acccident mitigation.

Th3 pressure requirements of the air receivers will be established through a special test and the UFSAR and the surveillance procedures will be revised accordingly. Additionally, a review to determine other possible discrepancies b5 tween the UFSAR and surveillance procedures is ongoing.

N?C FORM 366 (4-95) 9611260156 961122 PDR ADOCK 05000245 S

PDR

NRC FORM'366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

UCENSEE EVENT REPORT (LER)

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

)

96 055 00 TEXT (11more space is required, use additional copies of NRC Form 36CA) (17) 1.

Description of Event

On October 23,1996, with the plant shutdown and the reactor in the COLD SHUTDOWN condition, an audit of operating procedures as part of the design basis verification effort identified that the DC compressor on the EDG l

rir start system may not have started at the 225 psig as described in the UFSAR. It was discovered that the 1

surveillance test, SP 668.1, " Diesel Generator Operational Readiness Demonstration," documented that the DC compressor has started at a pressure as low as 215 psig.

I On November 12, 1996, investigation determined that, the preoperational test, that was performed to d:monstrate that the EDG air start system was capable of three EDG starts, is the only documenting evidence of tha pressure requirements of the EDG air start system. This test initiated the first of three EDG starts at 250 psig.

Thus, it was determined that the EDG air start system had been operated outside the Plant's Design Basis. A l

riport was made pursuant to 10 CFR 50.72(b)(2)(i). There were no automatic nor manually initiated safety system responses as a result of this event. This LER is being reported in accordance with the requirements of 10 CFR 50.73(a)(2)(ii).

The operational status of the EDG was inoperable at the time of this event and the EDG will remain inoperable l

until the EDG air start system pressure requirements have been established and validated by test.

II.

Cause of Event

l The cause of this event is the failure to properly identity and verify the design basis of the EDG air start system.

The original FSAR did not clearly identify the design basis, subsequent revisions to the UFSAR did not clarify this d: sign basis and the preoperational and subsequent surveillance testing failed to adequately verify the design bisis.

Ill. Analvsis of Event The EDG is one of two sources of emergency power, the other being a Gas Turbine Generator, utilized to mitigate j

ths consequences of a Loss of Normal Power.

The EDG system is designed with a compressed air system to achieve a diesel start. This consists of two air r:ceivers, two air compressors, valves and interconnecting piping. One air compressor is powered from the normal 480 VAC supply, while the other, a smaller, backup compressor, is powered from the 125 VDC supply.

The diesel generator operational readiness surveillance, includes a section that demonstrates that the DC powered j

compressor starts between 215 - 220 psig. However, the UFSAR states that "The two air compressors are stirted if the pressure in the reservoirs falls to 225 psig".

Investigation into this discrepancy has revealed that the original FSAR stated that the starting air pressure is 250 psig and that each air receiver contains sufficient inventory to start the diesel three times, without recharging.

This was successfully demonstrated in the preoperational test by performing three starts, beginning with the initial start at an air pressure of 250 psig and subsequent starts at 200 psig and 175 psig. During the prrparation of the UFSAR, a statement was added that the compressors start at 225 psig, however, no supporting documentation was found that provides reasonable assurance that the receivers would still contain sufficient inventory for three starts when the air receiver pressure is as low as 215 psig.j

4 NRC FOR 366A U.S. NUCLEAR REGULATORY COMMISSloN (4-90 LICENSEE EVENT REPORT (LER) i 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 3 of 3 i

j 96 055 00 l

TEXT lif more space is required, use additional copies of NRC Form 366A) (17) l The start and stop setpoints of the DC compressor are 220 and 245 psig respectively. However, the surveillance data indicates that the DC compressor started at a pressure as low as 215 psig.

The current statement in the UFSAR also implies that the two air compressors are started if the pressure in the receivers falls to 225 psig. This is misleading in that the AC compressor is preferred and cycles as necessary to maintain the air receiver pressure at 225 to 250 psig. The DC compressor is designed to be the backup air compressor and will automatically start upon failure of the AC compressor and is set to maintain the receiver prassure at 220 to 250 psig.

The safety consequence is minimal since it was demonstrated, through the preoperational test, that at least two j

j EDG starts had been available by the EDG air start system. Meanwhile, the safety analysis assumes that given i

one unsuccessful EDG start, the gas turbine is relied upon for accident mitigation.

1 3

IV. Corrective Action

i As a result of the event described in this LER and the subsequent investigation, the following corrective action is required:

d

1) The design basis of the EDG air start system will be established and it will be ensured that it is met.

This will be completed prior to declaring the EDG operable.

t 1

2)

The UFSAR and surveillance procedures will be revised as necessary prior to Cycle 16.

3) A review of other systems to identify and resolve design basis discrepancies is ongoing as part of the i

design basis verification program to address 10 CFR 50.54(f) concerns. The 10 CFR 50.54(f) review i

and recommendation implementation will be completed before startup for Cycle 16.

i V.

Additional Information

i

Similar Events

Review of LERs has revealed no similar design control events involving the EDG air start system in the last two years.

Manufacturer Data None.

NRC FoHM 366A (4-95)