RA-11-067, Non-Routine Operating Report of Important Environmental Event

Non-Routine Operating Report of Important Environmental Event

ML11279A178
Person / Time
Site:	Oyster Creek
Issue date:	08/26/2011
From:	Massaro M Exelon Generation Co, Exelon Nuclear
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RA-11-067
Download: ML11279A178 (10)

Text

Oyster Creek Generating Station www.exeloncorp.com Exelmn. Nuclear Route 9 South PO Box 388 Forked River, NJ 08731 10 CFR 50.4 RA-1 1-067 August 26, 2011 United States Nuclear Regulatory Commission Document Control Desk Washington DC 20555-0001 Oyster Creek Nuclear Generating Station Facility Operating License No. DPR-16 NRC Docket No. 50-219

Subject:

Non-Routine Operating Report of Important Environmental Event On July 28, 2011, the Oyster Creek Nuclear Generating Station (OCNGS) Unit 1 experienced a loss of the 34.5 kV 'B' bus supplying offsite power to the dilution plant. Although two dilution pumps were restarted after restoration of power to the dilution plant, more than 100 fish were stunned or killed. The fish kill was reported to New Jersey Department of Environmental Protection (NJDEP) as required by NJ Admin Code 7:14A-6.10(c) and to the U.S. Nuclear Regulatory Commission in accordance with reporting requirements of OCNGS Environmental Technical Specifications §3.5.2. The results of this event are detailed in the enclosed report.

Please advise Malcolm Browne, Environmental Specialist, at 609.971.4124 of any further information you may require in regards to the environmental aspects of this event.

Sincerely, Michael J. Ma saro Vice President - OCNGS Enclosure cc: New Jersey Department of Environmental Protection (3 addressees)

NRC Administrator, Region I NRC Senior Project Manager NRC Senior Resident Inspector

ENCLOSURE OYSTER CREEK NUCLEAR GENERATING STATION FISH KILL MONITORING REPORT JULY 2011 Exelon Generation August 2011

Enclosure to RA-1 1-067 Page 2 of 9 Executive Summary During the evening of Thursday July 28, 2011, Oyster Creek Nuclear Generating Station (OCNGS) was operating at 100% power level when the site experienced a loss of power to the dilution plant and various other station equipment at 2003 hrs due to a fault on the "B" 34.5 kV electrical bus in the Oyster Creek/JCP&L substation. Although Exelon performed a power reduction to 70% power, restarted the dilution pumps, followed by a further power reduction to 53% power, a fish kill totaling 1801 fish occurred beginning at approximately 2115 hrs.

Exelon contacted the DEP Hotline at 2301 hrs as required by NJ Admin Code 7:14A-6.10(c) to report the loss of the thermal dilution plant and the dead fish.

Exelon dispatched its ecological consultants Normandeau Associates (ecological experts contracted by Exelon) to monitor for and remove all stressed or dead fish from the discharge canal. The discharge canal was monitored by OCNGS personnel and environmental contractors subsequent to the discovery of the fish kill until completion of the monitoring efforts at noon on July 31.

Exelon is performing an investigation to determine cause(s) of the event and corrective actions will be assigned based on the results of that investigation.

Introduction This report documents the results of aquatic monitoring conducted between July 28 and July 31, 2011, by Exelon and its contractors following a thermal shock fish kill that occurred in the OCNGS discharge canal subsequent to an unplanned and unanticipated loss of power on July 28, 2011 to the thermal dilution plant. The objectives of the monitoring program were to:

1) Determine the species composition, relative abundance and distribution of fish in the OCNGS discharge canal following the loss of power to the dilution pumps, and

2) Quantify the extent of any fish mortalities.

Results During the evening of Thursday July 28, 2011, OCNGS was operating at 100% power level when a fault occurred on a JCP&L- owned power line that resulted in a partial loss of 34.5 kV power in the Oyster Creek substation that tripped all 34.5KV "B" bus related breakers at 2003 hrs. This fault resulted in the loss of power to the J-69361, R-144, Q-121 and Z-52 electrical feed lines, as well as the Bank 5 and Bank 7 transformers. Because the Bank 5 transformer provides power to the dilution pumps, this electrical fault resulted in the loss of all power to the dilution plant as well as other station equipment. Main Control Room personnel responded to these events by initially reducing power to 70% power level as well as a subsequent power drop to 53% power level, and restarting the dilution pumps shortly after power to them was restored. Two dilution pumps were restarted at 2121 hrs and 2129 hrs, respectively, which resulted in a reduction of discharge canal temperatures (Figures 1-4). The failure of an electrical cross-connect disconnect switch in the Oyster Creek /JCP&L substation at 2218 hrs resulted in another loss of power to the dilution

Enclosure to RA-1 1-067 Page 3 of 9 pumps and required Exelon to work with JCP&L to establish the seldom-used Q-121 line as an electrical alternate feed to re-energize the dilution pumps. Following the restoration of power to the dilution pumps via the Q-121 alternate feed, Exelon restarted two dilution pumps at 0235 hrs and 0304 hrs, respectively, during the early morning of July 29.

Normandeau fishkill monitoring activities began early in the morning of July 29 and continued until 1200 hrs July 31. With the unit at nearly full power prior to the initial loss of power to the dilution pumps, the Main Condenser discharge temperature had been approximately 19 to 20OF above ambient in the days leading up to July 28. In contrast, the dilution discharge provides a substantial flow of ambient temperature water for thermal dilution of the discharge canal. Fish that are typically heat-sensitive, such as striped bass, may have been residing in areas of the discharge canal cooled by the large volume of ambient water temperature provided by the dilution pump discharge. The sudden removal of this moderate temperature water source following loss of power to the dilution pumps caused a sudden change in discharge canal temperature and resulted in thermal shock to these fish, resulting- in the observed fishkill.

Plant personnel and Normandeau boat crews collected a total of 1801 dead fish, predominantly striped bass and menhaden, during the early morning of July 29 and the following two days. A total of 13 fish species ranging in length from 80 mm to 1000 mm was collected during the three-day monitoring period (Table 1). Single individuals of black sea bass, northern kingfish and northern searobin were recovered along with large numbers of striped bass and menhaden. A random subsample of these fish was measured to determine approximate average lengths.

Discussion and Conclusions Field observations indicate that the fish mortalities on July 28, 2011, were likely caused by the sudden change in the temperature in the discharge canal. *These fish, primarily striped bass, were probably residing in the ambient temperature dilution pump discharge or other moderate temperature areas of the discharge canal at the time of the plant shutdown. They were probably attracted to these areas in the discharge canal earlier in the year and remained there. The death of these fish is consistent with what is known about their.thermal tolerances and upper lethal temperature limits, and past observations of heat-shock events.

The July 28, 2011 fish kill resulted from the inability of some of the fish species inhabiting the OCNGS discharge canal to tolerate the'relatively warm water temperatures they encountered in the discharge canal subsequent to the loss of power to the dilution pumps. Intake canal temperatures were about 28.3 °C (83.0 OF), at the time of the dilution pump loss of (Figure 1). The Main Condenser discharge temperature at the time the dilution pumps became de-energized was approximately 39.4 °C (103.0 OF), resulting in a temperature difference of about 11.1 °C (20 OF).

The discharge canal temperature reached a peak temperature of about 38.0 °C (100.5 0 F) at the Route 9 bridge approximately 1.75 hours8.680556e-4 days <br />0.0208 hours <br />1.240079e-4 weeks <br />2.85375e-5 months <br /> following the loss of dilution pump power.

RA-1 1-067 Page 4 of 9 At OCNGS, se, enhaden, and bluefish) have I iible to observe that species otl ,i the discharge canal but unaff fish kill monitoring, the ;Iwas the Atlantic needle , been the first species to repc the peak water temperatures.

Enclosure to RA-1 1-067 Page 5 of 9 Figuu .Losf 4k 3'S , 0br CWMDIA = Main Condenser Discharge (DSNOOI) Water Tenmerature CWMD2B = Route 9 Bridge Water Temperature DTI 5AVG = Main Condenr - Intake Water Temperature Differential (Delta T)

HBCTP = Reator Core Thenmal Power (Percent)

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