RA-08-001, Non-Routine Operating Report of Important Environmental Event

Non-Routine Operating Report of Important Environmental Event

ML080230579
Person / Time
Site:	Oyster Creek
Issue date:	01/18/2008
From:	Rausch T AmerGen Energy Co, Exelon Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RA-08-001
Download: ML080230579 (8)

Text

AmerGen Energy Company www.exeloncorpco0m AmerGe n An Exelon Company Oyster Creek US Route 9 South, P.O. Box 388 Forked River, NJ 08731-0388 10 CFR 50.4 RA-08-001 January 18, 2008 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 December 19, 2007, the Oyster Creek Nuclear Generating Station (OCNGS) was manually scrammed due to a partial loss of feedwater event. The subsequent reduced outfall temperature resulted in more than 100 fish stunned or killed, which 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 (NRC) in accordance with reporting requirements of OCNGS Environmental Technical Specifications §3.5.2. The results of this occurrence are detailed in the enclosed report.

Please advise Malcolm Browne, Environmental Specialist, at 609.971.4124 of any further information you may require regarding the environmental aspects of this event. AmerGen will submit a Licensee Event Report to the NRC at a future date in accordance with 10 CFR § 50.73 detailing the reactor scram leading to this environmental event.

Sincerely, ijc Pr 'gco Ti otthy S. Rausch ice 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 AmerGen Energy Company, LLC January 2008

Fishkill Monitoring Report Page 2 of 7 Executive Summary During the morning of Wednesday December 19, 2007; Oyster Creek Nuclear Generating Station (OCNGS) was operating at a stable reduced power level of 54 percent to perform scheduled on-line plant maintenance. The power level had been reduced earlier in the morning in a slow manner to protect aquatic life. At the beginning of power reduction the intake temperature was approximately 38°F and the discharge temperature was approximately 58 0 F.

AmerGen Energy Company, LLC (AmerGen) monitored the discharge canal for thermally stressed fish and no stressed or dead fish were observed during the downpower.

At 11:45 a.m. on December 19, 2007, AmerGen initiated a manual reactor scram following loss of the "A" Main Feed Pump (MFP). The "B" MFP had been secured earlier during a pre-planned power reduction for on-line maintenance. With only the "C" MFP running, control room operators preemptively initiated a manual reactor scram due to lowering reactor water level. All systems actuated and performed as expected following the reactor scram. Water temperatures in the discharge canal declined as a result of the scram and consequently, the first stressed bluefish were observed at the discharge canal early in the afternoon of December 19, 2007.

On December 19, 2007, at 2:33 p.m. AmerGen contacted the DEP Hotline as required by NJ Admin Code 7:14A-6.10(c) to report the unplanned reactor shutdown and the dead fish observed in the discharge canal.

Normandeau Associates, ecological experts contracted by AmerGen, were dispatched to monitor and remove all dead and dying fish from the discharge canal. The discharge canal was monitored during daylight hours during the downpower and following the unplanned shutdown by OCNGS personnel and environmental contractors.

AmerGen commenced restart of the unit on the morning of December 20, 2007, in order to return the source of heated water to the discharge canal as soon as safely possible and thereby relieve the potential for thermal stress to fish still in the canal. AmerGen is conducting an investigation to determine cause(s) of the event and corrective actions will be assigned based on the results of that investigation. AmerGen will submit a Licensee Event Report (LER) to the NRC in accordance with 10 CFR 50.73 detailing results of the root cause evaluation of the reactor scram and corrective actions assigned from that evaluation.

Scope This report documents the results of aquatic monitoring conducted by AmerGen prior to and following a thermal shock fish kill which occurred between December 19 and December 21, 2007, in the discharge canal of OCNGS following an unplanned reactor scram. The objectives of the monitoring program were to:

1) determine the species composition, relative abundance, and distribution of fishes in the OCNGS discharge canal during the planned power reduction and following the reactor scram; and

2) quantify the extent of any fish mortalities.

Fishkill Monitoring Report Page 3 of 7 Results During the morning of Wednesday December 19, 2007, OCNGS was ramping down from 100 percent power to approximately 55 percent power to conduct scheduled on-line maintenance on two motor-generator units and a condenser waterbox. This gradual downpower from 100 percent power at a rate of only about 5 percent per hour was commenced at 1:00 a.m. on December 19, 2007, and OCNGS achieved 55 percent power at approximately 10:00 a.m. the same morning.

AmerGen contracted Normandeau Associates, Inc. (Normandeau) to monitor fish activity during and following the downpower at multiple locations from just downstream of the OCNGS discharge to just upstream of Barnegat Bay. Normandeau staff used an underwater camera to determine the type and relative number of fish in the canal. Striped bass and bluefish were observed to be the predominant fish species in the canal. Striped bass can withstand water temperatures down to about 36 0F. Bluefish are more sensitive to cold and need water temperatures in the upper 40s to survive. Water temperatures were recorded by the plant computer system and are shown in Figure 1 for three locations. Reactor power (percent of full power) and temperature (degrees Fahrenheit) rise across the condenser are also plotted on Figure 1.

Figure 1. Dec 19- 21, 2007 Power/Temperature 120 100 80 INTAKE TEMPI, 15-MIN AVG

--- DISCHARGE TBIRP,15-MIN AVG 60 CORE THE-IMAL POWER (PERCJENT)

PIT 9 BRIDGE TEP1 5-MIN AVG CIRC WATER DELTA T;1 5-MIN AVG 40 20 Hours CMt co: on 12 / 'I O)

Hours after 00:00 on 12/19/07

Fishkill Monitoring Report Page 4 of 7 The ambient water temperature was about 38.5°F when the downpower was commenced on December 19, 2007, and with the unit at full power the discharge temperature was approximately 20°F above ambient. Consequently, fish that were attracted to and had been living in the OCNGS thermal discharge water became acclimated to the warmer water temperature. Under natural conditions, warm season inhabitants of the mid-Atlantic region, such as bluefish, would have migrated to more southerly waters for the winter, but the warm water discharge provides a thermally attractive habitat in which they remained rather than migrating.

The unexpected tripping of a main feed pump at 11:45 a.m. on December 19, 2007, required Operators to manually scram the reactor from a stable power level of 54 percent due to lowering reactor water level. Following the reactor scram, there was an abrupt loss of thermal load in the condenser cooling water flow and a corresponding decrease in discharge temperature. The downpower was planned to reduce circulating water flow during the power reduction so that discharge temperature remained relatively constant to minimize the environmental impact to fish in the condenser discharge. These special operational considerations achieved the desired result of maintaining the discharge temperature relatively constant and as a result, no impact to fish was observed throughout the downpower by Normandeau or plant personnel. However, the subsequent scram caused an abrupt and rapid decrease in the heated discharge to the canal and measured temperature from the condenser outfall decreased from approximately 62 0 F to 40°F within two hours.

Two thermal effects in this type of situation can adversely affect fish. The rapid decrease in temperature, if large enough, can adversely affect fish if they are unable to adjust to the rapidly falling temperatures. This is termed cold-shock. The second effect is a decrease in water -

temperature to below a level that the species in question can tolerate. This temperature varies depending on the species and, if exposed to critically low temperatures for a long enough time, the fish will die.

Normandeau began seeing stressed fish - almost all bluefish - during the early afternoon following the reactor scram on Wednesday, December 19, 2007. The fish formed a large school or group that moved down the discharge canal with the last of the heated water. Gradually, many of these fish became visibly stressed as observed by fish coming to the surface, moving erratically, and otherwise appearing disoriented. A Normandeau boat crew in the discharge canal above the Route 9 bridge collected dead and dying fish as they moved downstream to where they were observed congregating in the area of the Route 9 bridge. Normandeau boat crews collected several hundred more fish into the early evening, eventually netting over 2,000 bluefish for the total count on Wednesday.

During the early morning of Thursday, December 20, 2007, dilution pumps and circulating water pumps were returned to service to support plant restart. AmerGen restarted the unit as quickly and safely as possible to provide warmer water in the discharge canal. The pump restarts -

together with the rising tide - moved the dead fish out into Barnegat Bay at the mouth of Oyster Creek and north toward Forked River. A Normandeau boat crew in Oyster Creek above the Route 9 bridge saw few remaining fish upstream of the Route 9 bridge at first light on Thursday morning. This crew moved to below the bridge after they collected all dead fish

Fishkill Monitoring Report Page 5 of 7 observed above the bridge and then joined boat crews searching lower Oyster Creek and Barnegat Bay between the discharge and intake canals for dead fish.

Four crews collected over 2,000 dead and dying bluefish on Thursday, December 20, 2007.

Most of the dead bluefish were collected downstream of the Route 9 bridge. As of 4:00 p.m. a majority of the visible dead bluefish had been collected. Around 4:30 p.m. large numbers of stressed fish were again observed in the lower section of Oyster Creek. All four boat crews continued to collect the stressed and disoriented bluefish; the collection was stopped at 6:00 p.m. due to the onset of nightfall.

On Friday morning, December 21, 2007, Normandeau boat crews again collected dead fish from the Route 9 bridge downstream to Barnegat Bay until around noon with several hundred more bluefish collected. Few remaining stressed bluefish were observed during this collection period. A station employee conducted additional surveys of the discharge canal on Saturday, December 22, 2007, with no further dead or stressed fish observed.

A total of four fish species were collected during the three-day monitoring period (Table 2).

Single individuals of northern kingfish, American eel, and spiny dogfish were recovered along with the larger number of bluefish. The spiny dogfish was observed in a disoriented state prior to the reactor scram and most likely did not die as a result of thermal shock resulting from the shutdown. Overall, Normandeau collected a total of 5,301 bluefish, which ranged in length from 322 to 895 mm. Of these, a random sample of 657 was measured for total length and 59 fish were weighed to collect weight distribution for various lengths.. Over 83 percent of the measured bluefish were between 400 and 479 mm total length (Figure 1). Table 2 provides the length distributions and mean weights of the bluefish.

Table 1. Total number and length range of disoriented or dead fish collected from the OCNGS discharge canal and vicinity from December 19 to 21, 2007.

Common Name Scientific Name Total Number Length Range (mm)

Bluefish Pomatomus saltatrix 5,301 322-895 Northern Kingfish Menticirrhussaxatilis 1 150 American Eel Anguilla rostrata 1 700 Spiny Dogfish Squalus acanthias 1 600 Discussion and Conclusions The evidence indicates that the observed fish mortalities on December 19, 2007, and the days immediately thereafter were caused by cold shock and exposures to lethal water temperatures following the unplanned plant shutdown. These fish, almost exclusively bluefish, were residing in the heated condenser discharge of the OCNGS and the discharge canal at the time of the plant shutdown. They were most likely attracted to the elevated temperatures in the discharge canal during summer or early fall, and remained there. Prior to the shutdown, Normandeau observed schools of bluefish and striped bass in the condenser outfall area. The death of these

Fishkill Monitoring Report Page 6 of 7 fish is consistent with what is known about their thermal tolerances, lower lethal temperature limits, and past observations of cold-shock events.

The December 19 - 21, 2007, fish kill event resulted from the inability of some of the fish species inhabiting the OCNGS discharge canal to tolerate the relatively cold water temperatures they encountered in the discharge canal subsequent to the unplanned plant shutdown. Intake canal temperatures were about 3.6'C (38.5 IF), at the time of the OCNGS power ramp down on December 19, 2007 (Figure 1). The main condenser discharge temperature at the time of the shutdown was approximately 14.4 0C (58 OF), resulting in a temperature difference of about 10.80C (19.6 °F). The special mitigating operational considerations for maintaining the discharge temperature relatively constant achieved the desired result of no environmental impact to fish during the downpower.

Several fish species collected during this fish kill event (including bluefish, northern kingfish, American eel, and spiny dogfish) have been involved in cold shock fish kills on previous occasions at OCNGS. Large numbers of striped bass and lesser numbers of winter flounder, however, were observed to be within the discharge canal both before and after the event and appear to have been entirely unaffected by the post-shutdown water temperature changes. Furthermore, bluefish have been seen in the condenser outfall area as of January 8, 2008, indicating that an unknown portion of the original bluefish school also survived the cold shock.

200 180 160 140

......L....

120 E 100 z

80 60 U -~ U 40 20 0 OU -T-0*

T 0 0

-4 0 LU 0

0 00 -4 0 0 0 0 0 0 0'0 0 A N '? 'W "9 0 0ý U U, V 00 00 0 0n ul to N U, 0W 0 N 0 0 W~ 0 AT COO W tD0 o LO ON- N Length Range (mm)

Figure 2. Length-frequency distribution of dead and stressed bluefish collected in Oyster Creek and vicinity from December 19 to 21, 2007.

Fishkill Monitoring Report Page 7 of 7 Table 2. Length distribution and mean weight of dead and stressed bluefish collected from Oyster Creek and vicinity from December 19 to 21, 2007.

Length Range (mm) Number1 Composition Mean weight (ounces) Number weighed

< 319 320-339 2 0.3 340-359 1 0.2 15 1 360-379 3 0.5 380-399 24 3.7 20 5 400-419 93 14.2 23 10 420-439 172 26.2 28 9 440-459 189 28.8 31 6 460-479 91 13.9 35 4 480-499 28 4.3 41 3 500-519 6 0.9 48 3 520-539 3 0.5 54 2 540-559 3 0.5 62 1 560-579 7 1.1 64 1 580-599 3 0.5 80 2 600-619 10 1.5 78 4 620-639 2 0.3 89 2 640-659 4 0.6 93 2 660-679 2 0.3 70 1 680-699 2 0.3 700-719 0.0 720-739 3 0.5 112 1 740-759 1 0.2

> 759 8 1.2 137 2 Total 657 59 1

Note that a random subsample of bluefish was selected for length measurements and a total of 5,301 bluefish were collected.