ML20217C213

NPDES Noncompliance Notification:On 910629,chillers at Bedminster Water Processing Facility for Bradshaw Reservoir Tripped Due to Unexpected Failure of Logic Control Unit. Chiller Control to Primary Computer Restored

ML20217C213
Person / Time
Site:	Limerick
Issue date:	07/08/1991
From:	Doering J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Noll P NESHAMINY, PA
References
NUDOCS 9107150003
Download: ML20217C213 (4)

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. PHILADELPHIA ELECTRIC COMPANY LIMERICK GENER ATING STATION P. O. BOX A S AN ATOG A, 'ENNSY LV ANI A 19464 (215) 327 1200 rav. 2000

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.....u......n..'"" July 8, 1991 Mr. Peter G. Noll Department of Health Neshaminy Manor Center Doylestown, PA 18901

Subject:

Noncompliance with NPDES Permit Bradshaw Reservoir .

NPDES Permit No. PA-0052221

Dear Mr. Noll:

DESCRIPTION OF NONCOMPLIANCE On June 29, 1991, at approximately 1450 hours0.0168 days <br />0.403 hours <br />0.0024 weeks <br />5.51725e-4 months <br />, all three operatir.g chillers at the Bedminster Water Processing Facility (WPF) for the Bradshaw Reservoir tripped due to the unexpected failure of a logic control unit (LCU). Subsequent attempts to restart the chillers were unsuccessful. At approximately 1533 hours0.0177 days <br />0.426 hours <br />0.00253 weeks <br />5.833065e-4 months <br />, two of three operating Bradshaw pumps tripped. The 'B' pump tripped due to high vibration and the 'C' Tump tripped (spuriously) due to instantaneous over-current. At 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br />, the discharge temperature at the outfall to the East Branch of the Perkiomen Creek was 75.69 degrees F which exceeded the permitted instantaneous temperature of 74 degrees F. At 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br />, the measured discharge temperature was 78.07 degrees F, with an East Branch Perkiomen Creek flow of 34 cfs.

At 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br />, the discharge temperature was 66.11 degrees F and flow was 13 cfs. This was a result of the restart of the 'A' chiller combined with the operation of one Bradshaw pump.

Discussions between Limerick Generating Station'(LGS) Operations personnel, the Delaware River Basin Commission (DRBC) personnel and the Pennsylvania Department of Environmental Resources (PA DER) led us to conclude that, in this instance, operation of three Bradshaw pumps should be maintained to minimize impact an the environment in lieu of significantly decreasing flow to mainta n temperature. Once three Bradshaw pumps were returned to service, the discharge temperature remained below the 74 degrees F permitted due to the changing atmospheric conditions (rainfall and nighttime). The 'A' and 'B' WPF chillers were returned to service but the 'C' chiller remained out-of-service pending repair / replacement of the LCU. In accordance with NPDES Permit No. PA-0052221, a 24-hour notification 9107150003 910700

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Pane 2 of the noncompliance was completed on June 29, 1991, at approximately 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br />.

On Sunday, June 30, 1991, at approximately 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br />, the discharge temperature from the Bedminster WPF exceeded the NPDES permit limit of 74 degrees F. Based on the discussions from the previous day, we decided to maintain operation of three Bradshaw pumps in order to maintain constant flow. The cause of the temperature excursion was the inability to maintain operation of the 'C' chiller at the WPF.

The highest instantanenus temperature reading was 75.7 degrees F at 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br />. Upon furtner review we determined that it was prudent to reduce flow in order to reduce the discharge temperature, and augment the water supply with a release from the Tamaqua Reservoir.

We returned within permit limits at 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> when the temperature reading was 73.9 degrees F, after we shut down one of the threa operating Bradshaw pumps. In accordance with NPDES Permit No. PA-0052221, a 24-hour notification of this noncompliance was completed on July 1, 1991, at 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br />.

CAUSE OF THE NONCOMPLInNCE The cause of the noncompliance on Saturday, June 29, was the unexpected failure of an LCU on the 'C' chiller at the WPP. The failure was not a complete failure; the LCU failed in such a way that it caused the primary computer to swap control of all the chillers to a non-operational backup computer. Due to swap, the WPF operator could not restart the chillers.

The cause of the noncompliance on Sunday, June 30, was the unavailability of the 'C' chiller due to the failed LCU. It was not possible to maintain the discharge temperature below 74 d grees F while continuing operation of three Bradshaw pumps.

DURATION OF THE NONCOMPLIANCE The period o. noncompliance began at approximately 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on June 29, 1991, and ended at approximately 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br /> that same day.

The discharge temperature was restored to below the permitted 74 degrees F.by 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br />, yet permit noncompliances were experienced at 1600, 1700, 1800, 1900, and 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br /> in that the discharge temperatures changed by greater than 2 degrees F in a one hour period. We exceeded the permitted discharge temperature again from approximately 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> to 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on June 30, 1991.

CORRECTIVE ACTIONS The WPF operator obtained technical support to restore cniller control to the primary computer which permitted restart of the 'A' chiller at 1730 hours0.02 days <br />0.481 hours <br />0.00286 weeks <br />6.58265e-4 months <br /> on June 29, 1991. The LCD oa the 'C' chiller was. replaced on July 1, 1991.

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Page 3 PREVENTION OF FUTURE OCCURRENCES l The computer system at the WPF has been modified to provide notification to the operator when the computer has swapped over to the backup. This notification will allow the operator to recognize the condition and restore system control to the primary computer.

Additional direction has been provided to Shift Supervision on operation of the Bradshaw punips and the WPP in response to pump and/or chiller trips. Further clarification of the DPBC Docket and DER Permit is ongoing.

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l Sincerely, J. Doering, Jr.

DCS:cah 1 cc: U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 T. T. Martin Administrator, Region 1, USNRC T. J. Kenny USNRC Senior Resident Inspector, LGS Program Management Section (3WMS2)

Permits Enforcement Branch Water Management Division Environmental Protection Agency Water Permits Section Region III 841 Chestnut Building Philadelphia, PA 19107 Joseph A. Peola Regional Water Quality Manager Department of Environmental Resources Lee Park, Suite 6010 555 N. Lane, Conshohocken PA 19428

4 bcci G. M. Leitch - #200 J. Doering, Jr. - AS-1 R. W. Dubiel - AS-1 T. J. Jackson - SB3-3 G. J. Madsen - SB3-4 G. M. Morley, Jr. - S9-2 J. A. Muntz - 338 G. D. Edwards - AS-1 G. J. Beck - 52A-5 Commitment Coordinator - 52A-5 PA DER DRP Inspector - SD3-2 Correspondence Release Point - 340 NRMS

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