NL-18-0421, Results of Augmented Radiological Environmental Monitoring Program for the Years 2008 Through 2017

Results of Augmented Radiological Environmental Monitoring Program for the Years 2008 Through 2017

ML18088A212
Person / Time
Site:	Millstone, Hatch
Issue date:	03/29/2018
From:	Gayheart C Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-18-0421
Download: ML18088A212 (9)

Text

A Southern Nuclear Cheryl A. Gayheart Regulatory Affairs Otrector 40 Inverness Center Park I\ a~

Post Office Bo' 1295 Bmnmgham AL 35242 205 99~ 5316 tel MAR 2 9 2018 205 992 760 I fa:~.

caga) hea g southemco com Docket No.: 50-321 NL-18-0421 50-336 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant Results of Augmented Radiological Environmental Monitoring Program for the Years 2008 through 2017 Ladies and Gentlemen:

By letter to the NRC dated January 7, 1987, Georgia Power Company provided a description of an augmented Radiological Environmental Monitoring Program that was initiated following the release of radioactive water from the spent fuel storage pools at the Edwin I. Hatch Nuclear Plant to an onsite swamp in December 1986. Accordingly, the enclosed provides the latest summary of the program results for the years 2008 through 2017. The summary indicates that radioactivity levels in the swamp have continued to decrease to background levels. Monitoring of the swamp is being terminated with the submittal of this report.

This letter contains no NRC commitments. If you have any questions, please contact Ken McElroy at 205.992.7369.

Respectfully submitted, CAGffLE/cbg

Enclosure:

Assessment of the Results of Augmented Radiological Environmental Monitoring Program for the Years 2008 through 2018 Cc: Regional Administrator, Region II NRR Project Manager- Hatch Senior Resident Inspector- Hatch RTYPE : CHA02.004

Edwin I. Hatch Nuclear Plant Results of Augmented Radiological Environmental Monitoring Program for the Years 2008 through 2017 Enclosure Assessment of the Results of Augmented Radiological Environmental Monitoring Program for the Years 2008 through 2018

Enclosure Assessment of the Results of Augmented Radiological Environmental Monitoring Program for the Years 2008 through 201 7 On December 3 and 4, 1986, an event occurred at the Hatch Nuclear Plant (HNP) in which radioactive water from the spent fuel storage pools (SFSP) was released into the onsite swamp east of the cooling towers. As a result of this event, Georgia Power Company (GPC) initiated an augmented Radiological Environmental Monitoring Program concerning the swamp on December 15, 1986. This program, as described in a letter to the NRC dated January 7, 1987, calls for a periodic assessment to the program (including termination) as a result of the assessment.

Past assessments ofthe results of this program were provided to the NRC by letter as given below.

Period Date of Letter 12/15/86 through 1987 March 31, 1988 1988 April 3, 1989 1989- 1991 March 31, 1992 1992-1994 March 28, 1995 1995-1999 March 3, 2000 2000-2007 March 28, 2008 This report provides the program's result for the years 2008 through 2017, an assessment of those results, and the program modifications as a result thereof.

The program's current commitment calls for biennial collection of "muck" samples at locations A, PL-2, PL-3, MBC and a background location for gamma isotopic analysis. All ofthe sampling locations, except for the background location, are shown in Figure 1. The biennial collections were made on September 8, 2009, September 6, 2011, October 28, 2013, October 15, 2015, and September 5, 2017. Three samples were collected at location A and two at each of the other locations (including the upstream background location). The so-called muck samples are composed of substantial quantities of root and other organic material, as well as mud and sediment. Usually, each of the sampling locations are underwater for multiple weeks each year due to flood conditions. All laboratory analyses were performed at the GPC Environmental Laboratory in Smyrna, Georgia.

Sample location A is situated in the swamp pond in a representative location to the point where the water from the SFSP entered the swamp. Locations PL-2 and PL-3 lie along the plant's eastern property line.

Location PL-2 lies on the left bank of Bay Creek. Bay Creek provides a drain for the swamp; the mouth of Bay Creek is about three-quarters of a mile east of the plant's eastern property line. Location MBC lies along the right bank of Bay Creek adjacent to its entry into the Altamaha River.

The background location, like the swamp, lies in the floodplain of the Altamaha River but is positioned approximately 0.8 miles upstream of the plant's discharge and on the opposite side of the river.

The average manmade radionuclide activity at each sample location from 1987 through 2017 is provided in Table 1. Plots of the annual averages of the activities for Co-60 and Cs-137 are presented in Figure 2 and Figure 3, respectively. No other manmade radionuclides have been detected in samples collected from the onsite swamp since 1989. During this reporting period, only Co-60 and Cs-137 were identified.

Cs-134 (which has a 2.1-year radiological half-life) has not been identified since 1999 at location A and has not been found since 1990 in the other sampling locations.

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The activities found in the samples collected at location A were consistently higher than that of those collected elsewhere; however, there has been an evident downward trend present in the data since the previous report, indicating that weathering and decay are resulting in decreasing activity concentrations.

Figure 2 shows the Co-60 activity at location A, which dropped to below detection limit during the 2017 sampling event. No other locations showed activity above detection limit for Co-60. Figure 3 shows Cs-137levels at each location. The figure illustrates that while Cs-137 activity levels at location A were consistently above background over the past two decades, the values have been decreasing and ultimately returned to below background with this last sampling event.

Given the evident downward trends and most recent samples matching background levels, sample collection from the onsite swamp will be terminated and this will be the last report submitted under the Hatch Augmented REMP program. The existing REMP sampling program (air, water, sediment, etc.)

continues to indicate further justification for terminating the Augmented REMP program, given that no adverse effects have been observed in the surrounding environment at HNP. The results from the REMP sampling events are submitted in the Annual Radiological Environmental Operating Report (AREOR).

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Table I Average Activity of Manmade Radionuclides Found in Muck Samples Collected at Select Locations 1987 through 2017 (pCi/kg dry)

Location Nuclide 1987 1988 1989 1990 1991 J992 1993 1994 1995 1996 1997 1998 1999 Cs-137 342 369 708 280 418 428 335 452 302 172 170 178 178

Background

Eu-154 0 0 0 0 0 0 0 0 0 0 0 0 0 Mn-54 1684 183 513 0 0 0 0 0 0 0 0 0 0 Fe-59 430 0 0 0 0 0 0 0 0 0 0 0 0 Co-58 270 0 0 0 0 0 0 0 0 0 0 0 0 Co-60 6202 3628 4627 2567 1312 1733 961 835 549 570 1100 322 455 A

Zn-65 3118 631 0 0 0 0 0 0 0 0 0 0 0 Sb-125 658 0 0 0 0 0 0 0 0 0 0 0 0 Cs-134 10892 3642 3153 1400 576 718 326 229 79 83 0 0 0 Cs-137 19813 10708 12790 7667 5010 9763 4073 3855 2310 2767 1610 1580 5897 Co-60 0 27 0 0 49 0 0 0 0 0 0 0 0 PL-2 Cs-134 194 67 0 145 0 0 0 0 0 0 0 0 0 Cs-137 1457 927 558 1450 1205 916 582 650 318 93 211 394 230 Mn-54 24 0 0 0 0 0 0 0 0 0 0 0 0 PL-3 Cs-134 340 91 84 0 0 0 0 0 0 0 0 0 0 Cs-137 1488 862 76 870 967 288 128 134 507 0 0 0 54 Mn-54 47 0 0 0 0 0 0 0 0 0 0 0 0 Co-60 68 34 0 34 48 70 90 134 43 0 131 110 Ill MBC Zn-65 95 0 0 0 0 0 0 0 0 0 0 0 0 Cs-134 331 224 0 0 0 0 0 0 0 0 0 0 0 Cs-137 807 556 419 280 298 304 377 266 260 290 193 232 221 Note: Periods for which no detectable measurements were observed are listed in the table as zero.

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Table 1 (continued)

Average Activity of Manmade Radionuclides Found in Muck Samples Collected at Select Locations 1987 through 2017 (pCi/kg dry)

Location Nuclide 2000 2001 2002 2003 2005 2007 2009 2011 2013 2015 2017 Cs-137 132 178 174 204 128 163 132 132 132 132 132

Background

0 0 0 0 I

Eu-154 0 0 0 0 0 0 0 Mn-54 0 0 0 0 0 0 0 0 0 0 0 Fe-59 0 0 0 0 0 0 0 0 0 0 0 Co-58 0 0 0 0 0 0 0 0 0 0 0 Co-60 317 243 270 196 249 312 215 155 176 134 0 A 0 0 0 0 Zn-65 0 0 0 0 0 0 0 Sb- 125 0 0 0 0 0 0 0 0 0 0 0 Cs-134 0 0 0 0 0 0 0 0 0 0 0 Cs-137 1538 1405 2754 1654 1130 1360 1180 1473 917 1243 95 Co-60 0 0 0 0 0 0 0 0 0 0 0 PL-2 Cs-134 0 0 0 0 0 0 0 0 0 0 0 Cs-137 249 293 223 240 182 434 268 114 183 175 82 Mn-54 0 0 0 0 0 0 0 0 0 0 0 PL-3 Cs-134 0 0 0 0 0 0 0 0 0 0 0 Cs-137 0 34 37 63 29 177 12 37 45 71 62 Mn-54 0 0 0 0 0 0 0 0 0 0 0 Co-60 0 0

• 0 0 0 0 0 0 0 0 MBC Zn-65 0 0 0 0 0 0 0 0 0 0 0 Cs-134 0 0 0 0 0 0 0 0 0 0 0 Cs-137 133 89 158 208 92 78 19 71 268 18 29

• One sample showed no detectable activity and the other sample showed 1967 pCi/kg-dry which is thought to be an erroneous value.

Note: Periods for which no detectable measurements were observed are listed in the table as zero.

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Figure 2 Co-60 Yearly Average (Half-life 5.27 years) 350.0 300.0 1 _._ A I

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Note: Since 2000, Location A was the only sample location at which Co-60 was detected.

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Figure 3 Cs-137 Yearly Average (Half-life 30.17 years) 3000.0 ~ T r r r lr ...,._ A

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