ML20059C494

NPDES Noncompliance Notification:On 930907,cooling Tower Blowdown Water Discharged Into Possum Hollow Creek Due to Loss of Two of Four Operating Circulating Water Pumps. Procedures for Performing Excavations Revised

ML20059C494
Person / Time
Site:	Limerick
Issue date:	10/26/1993
From:	Boyce R PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Bauer R PENNSYLVANIA, COMMONWEALTH OF
References
NUDOCS 9311010173
Download: ML20059C494 (6)

Text

.

}

, q L -

PIIILADELPHIA EIECTRIC COMPANY LIMERICK GENERATING STATION  !

P. O. BOX 2300 ,

SANATOGA, PA 19464-2300 (215) 327-1200 EXT,2000 ROBERT W fr#CE N a^Gm October 26, 1993 LIMERICK GENERAlohC STATION

~

Robert Beuer, Jr. j Department of Environmental Resources l Bureau of Water Quality Management Suite 6010, Lee Park 555 North Lane Conshohocken, Pts 19428

SUBJECT:

Limerick Generating Station, Units 1 and 2 Noncolapliance with NPDES Permit No. PA-0051926, Cooling Tower Blowdown Manhole Overflow to Possum Hollow Creek

Dear Mr Bauer:

I DESCRTPTIOM OF THE EVENT On September 7, 1993, a noncompliance of the National Pollutant ,

Discharge Elimination System (NPDES) permit for the Limerick )

Generating Station (LGS) occurred after Unit 1 and Unit 2 Cooling Tower blowdown water was discharged into the Possum Hollow Creek. i This discharge condition resulted in the unpermitted release of l chemically treated water from an unmonitored discharge point. l On September 7, 1993, both LGS Units 1 and 2, were operating at 100% power. At approximately 1433 hours0.0166 days <br />0.398 hours <br />0.00237 weeks <br />5.452565e-4 months <br />, an interruption of the offsite electrical power supply tu the 10 Station Auxiliary Bus led to a Unit 1 Reactor Feedwater System (FWS) anomaly resulting in slowly decreasing reactor level. Before Operations personnel could reduce power or control FWS operation, an automatic shutdown of the Unit 1 Reactor occurred due to low reactor water level (i.e., level 3) During a normal reactor shutdown, internal station house electrical loads, which are normally powered from the Main Generator, automatically transfer to the two offsite power sources. As a result of this transient, the 10 Station Auxiliary bus was deenergized and some of the internal station house loads could not be transferred to the offsite power 9311010173 931026 I -l

$DR ADOCK 05000352 h h i PDR h

N N

- Page 2 . <

acurce. This resulted in the. loss of various plant equipment, including two of the four operating circulating water pumps. -

While actions were immediately being taken by Operations personnel in response to the transient, plant personnel discovered water discharging from a manhole on the cooling ~ tower . ,

blowdown line (i.e., Outfall 001). The Main Control Room was notified and Operations personnel reduced the makeup flow to the ,

cooling tower, thereby reducing the blowdown finw rate. Plant personnel estimated that the blowdown line manhole discharged I water into the Possum Hollow Creek for a time period of '

approximately 20 minutes.  :

The chemical makeup of the water discharged into the Possum Hollow Creek was analyzed on September 7, 1993, prior to the transient. The pH of the discharge was 7.67, and the total zinc  !

concentration was 0.64 ppm. All values were within the permitted limitations for Outfall 001, and therefore, the environmental impact as a result of this noncompliance was minimal.

i PAUSE OF THE NONCOMPLTANCE I J

The cause of this noncompliance was due to a loss of two of the four operati'ng circulating water pumps, and the Unit 1 reactor shutdown from the partial loss of offsite power. After the two ,

circulating water pumps tripped, an instantaneous decrease of approximately 250,000 gpm occurred in the water being withdrawn

! from the Unit 1 cooling tower basin. The decrease in circulating water flow combined with the rapid decrease in power evaporative losses due to the reactor shutdown, caused the Unit 1 cooling i

, tower basin level to rapidly increase. Since blowdown flow is

proportional to cooling tower basin level, blowdown flow also 4 increased. The increase in blowdown flow from the Unit 1 cooling tower combined with the normal blowdown flow from the Unit 2 l cooling tower resulted in a blowdown rate in excess of the l capacity of the blowdown pipe. As a result, Operations personnel were not able to reduce makeup flow quickly enough to prevent the resultant surge in cooling tower level and the unpermitted discharge from the vented manhole.

The root causes of the trip of the 10 Station Auxiliary Bus which )

led to the FWS anomaly resulting in the shutdown of the Unit 1 reactor are less than adequate control of non-routine work processes, unclear supervision and worker expectations, and less ,

than adequate control of excavations including inadequate choring  !

procedural guidance. The primary cause of the Unit 1 FWS anomaly I which resulted in the reactor shutdown on low water level was due to the failure of the Unit 1 D114-G-D Motor Control Center Feeder Breaker to reclose following the reeneraization of the D11 Safeguard Bus. The failure of the Feeder Breakor to reclose is inde t e rmina t e ..

+ .- ,- . . - - - . , - . - , - .. . - . - _ , . . - - _ - . , . ., ,.

% i I

Fage 3  ;

i On August 3, 1993, a contrac..: work group started scheduled -

excavation to repair a fire protection system pipe leak ,

associated with a fire hydrant. By August 26, 1993, the '

contractor work group had completed all the excavation work with only trench backfilling work remaining. On August 27, 1993,-the * '

contractor work group was relieved by a station work group. On September 7, 1993, the station work group utilized a beckhoe to

'aquare off' the excavated trench to assist in the upgrading of existing shoring. During the trench rework, damage to the 10  !

Station Auxiliary Bi 'C' phase cable occurred.

The initiation of t. .rench rework was beyond the normal responsibilities and training of the station work group. The ,

station work group supervision and workers, however, did not .

realize that the change in job scope was outside their area of i qualification and authority, and that insufficient work instructions existed. Additionally, the excavation program, including shoring procedural guidance, did not provide adequate  ;

controls to ensure this type of work is performed by the appropriate qualified personnel with adequate work instructions.  ;

Finally, the shoring previously installed by the contractor work group and in,apected by the station safety group was inadequate.

The station safety instructions for shoring did not provide the level of detail needed to comply with the corporate policy for. .

shoring. j PREVENTTON OF FUTURE OCCURPENCES ,

Shutdown of a circulating water pump normally results in an increase in cooling tower blowdown flow for a short period of -

time until the basin water level transient subsides. Existing station operating procedures provide Operations personnel instructions to monitor cooling tower blowdown flow when securing a circulating water pump.

The combination of events leading to this permit noncompliance 'I' resulted from a complicated sequence involving the loss of an offsite power source, the failure of a Feeder Breaker to reclose, and the automatic shutdown of an operating unit. An unusual transient such as this will result in an overflow of the blowdown  ;

line until the transient subsides and makeup flow to the cooling l tower is reduced.

To prevent the recurrence of a similar plant transient the <

following corrective actions have been implemented.

1. On September 8, 1993, a letter to all Station Supervisors.

from the LGS Vica President was issued to establish a ,

designated station excavation coordinator. This letter

'l

- r. h.,,,. +y., w.-, , n,-, , . . . . . , , -

3 4

. i l

Page 4 requires all curr ent and tuture. excavation activities to be authorized by the Contract service Manager who will. serve as - '

the excavation coordinator until additional personnel are -

trained. )

2. An " All Hands" meeting was conducted on Sev: ember 20, 1993,. -

for the station Support Services Division, with a clear  ;

discussion on open communication between the werker and.

supervision, and the expectation that a worker shall not 1 proceed beyond their abilities or administrative controls.

3. The station procedure for performing excavations was revised <

to cover shoring instructions, assignment of ex.cavation I shoring coordination, and training and qualification for appropriate station individuals. Additionally, the maintenance work planning guideline was revised to require j the usage of the excavation procedure to ensure that a q competent excavation / shoring coordinator is assigned for all .

related activities. Finally, the station safety instruction 1 for shoring was revised to provide detail consistent with J the corporate policy for shoring.  ;

4. A letter from the LGS Vice President has been issued to all station' supervision to reinforce the expectation on work ,

control adherence, work turnovers, training and '

qualification requirements, division of responsibilities, and proper work instructions. A follow-up "For Your ,

Information (FYI)" Bulletin will be issued to further communicate these expectations.

1

5. The D114-G-D MCC Feeder Breaker reclosure control circuit components were replaced to increase reliability.

Additionally, a Breaker Diagnostic Testing Program has been established to verify continued proper control circuit  !

operation of all Feeder Breakers similar to and including  !

Dll4-G-D. l If you have any questions please contact Jim Kantner at 327-1200 extension 3400.

F Si nce r ely ,,. l

\

gg xg> .

DMS:cah 1

1

-)

k - _ _ _ . -_ ._ _ . , _ . _ -,

l{

.... r s

j  ;

Page.5

'q cc: -U.S. Nuclear Regulatory Commission- -

t Document Control Desk' Docket Nos. 50-352/353 Washington, D.C. 20555 T. T. Martin Administrator, . Region I, USNRC Docket Nos. 50-352/353 N. S. Perry USNRC Senior Resident Inspector, LGS Docket Nos. 50-352/353 P Program Management Section (3WM52) '

Permits Enforcement Branch ,

Environmental Protection Agency Water Management Division Environmental Protection Agency Water P,ermits Section Region III 841 Chestnut Building Philadelphia, PA 19107 t

B 4

i l

1

_m______ - _______ .__ _,

- , .. .. . ._ . . . - .. .. _ -= . .. .- - . . . . , ,

, Page 6- '

i,

. bec: D. R. Helwig - SMB1-3 -

)

K. S. Kemper - SSB2-1 J. .A. Muntz - SSB3-1 G. A. Hunger, Jr. - 52A-5 G. M. Morley, Jr. - N4-10 .

C. S. Markle - SSB3-1 ,

Commitment Coordinator - 52A-5 '

l PA DER BRP Inspector - SMB2-4 Correspondence Release Point - SMB1-2 ,

t 4

k b

F t

a y p , 3 .- i,.-- ,r. ~.,m. _____ ._ __ ___a