ML20248K173

Rev 1 to App D, Special Ground & Well Water Samples, of 1994 Annual Radiation Environ Monitoring Program Rept

ML20248K173
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Site:	Prairie Island
Issue date:	12/31/1994
From:	NORTHERN STATES POWER CO.
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i Praire Island Nuclear RADIATION ENVIRONMENTAL Rev.1

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Generating Plant MONITORING PROGRAM 1994 ANNUAL REPORT Appendix D APPENDIX D Special Ground and Well Water Samples j

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Praire Island Nuclear RADIATION ENVIRONMENTAL Rev.I Generating Plant MONITORING PROGRAM 1994 ANNUAL REPORT Appendix D

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1.0 INTRODUCTION

This revision corrects the October 1994 tritium numbers that were reported in Tritium Units instead of pCi/L. One (1) Tritium Unit equals 3.2 pCi/L. All previously reported tritium numbers in October 1994 have been multiplied by 3.2.

This appendix to the Radiation Environmental Monitoring Program Annual Report to the United States Regulatory Commission summarizes and interprets results of the special well and surface water samples taken at the Prairie Island Nuclear Generating Plant, Red Wing, Minnesota, during the period January - December,1994. This supplement special sampling program was established -

in December of 1989 when tritium was detected in a nearby residence well sample.

Tabulations of the special sampling program individual analyses made during the year are included in this appendix. A summary table of tritium analyses is also included in this appendix.

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Praire Island Nuclear RADIATION ENVIRONMENTAL Rev.1 Generating Plant MONITORING PROGRAM 1994 ANNUAL REPORT Appendix D 2.0

SUMMARY

This special sampling program was established following the detection of tritium in a residence well water sample south of the PINGP during 1989. This program is described and the results for 1994 are summarized and discussed.

i Program findings detect low levels of tritium in nearby residence wells and some ground water seepage samples at or near the lower limit of detection (LLD), south of the plant. The tritium levels of the nearest resident south of the plant have shown a downward trend from 1430 pCi/L in 1989 to 51 pCi/L in 1994.

The analyses of the residence well water samples have been contracted to a laboratory capable of counting tritium levels to a lower limit of detection (LLD) corresponding to current expected natural background levels. Consequently, two (2) of the samples are reported as non-routine sample results. However, all results are far below the Environmental Protection Agency's drinking water standard of 20,000 pCi/L and present no harm to any members of the public.

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Generating Plant MONITORING PROGRAM 1994 ANNUAL REPORT Appendix D 3.0 Special Tritium Samoling Program 3.1 Program Design and Data Intemretation The pmpose of this sampling program is to assess the impact of the tritium leaching into the environment (ground water system) from the PINGP discharge canal. For this purpose, special water samples are collected and analyzed for radioactive content.

3.2 Program Description The sampling and analysis schedule for the special water sampling program is summarized in Table 4.1 and briefly reviewed below. Table 4.2 defines the additional sample locations and codes for the special water sampling program.

Special well and ground water was collected quarterly at eight locations: one sample from the PINGP Biology Station (P-30); one from the nearest residence deep well (P-24d, Suter residence); two ground water seepage from near Birch Lake (P-31 and P-32); well water from the Prairie Island Training Center (P-26); and three other nearby residences (P-27, Nauer residence; P-28, Allyn (Perkins) residence; P-29, Childs residence). The Rohl farm well (part of the quarterly REMP sampling) is used as a control location for these special samples.

3.3 Program Execution 1

1 The special water sampling was executed as described in the preceding section with the following exceptions:

l. No water sample was available during the second and fourth quarters from the Birch Lake locations (P-31 and P-32) due to high water levels in the lake. The ground seepage sample locations were under water.

2. The Allyn residence (P-28) had no renters living in the house for the first quarter of 1994.

The water sample was unattainable.

3.4 Program Modifications During the first three quarters, the sample analysis laboratory used an LLD of approximately 190 pCi/L. In order to detect low levels of tritium at or below natural background levels, starting in October 1994, analyses of the samples had been contracted to a laboratory (University of Waterloo Laboratories) capable of detecting tritium concentrations down to 19 D-4

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l Praire Island Nuclear RADIATION ENVIRONMENTAL Rev.I Generating Plant MONITORING PROGRAM

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1994 ANNUAL REPORT Appendix D l

pCi/L. Waterloo Laboratories report tritium analyses results in Tritium Units (1 TU = 3.2 pCi/L). The tritium results in this report are indicated in pCi/L.

3.5 Results and Discussion Results obtained continue to show very low levels of tritium in some well water and ground water samples. Table 4.4 provides the complete data table of results for each quarter and sampling location.

Results during the first two quarters of 1994 were below or near the analysis laboratory's lower limit of detection (LLD of approximately 190 pCi/L) with the exception of the Suter residence deep well and Birch Lake seepage samples. The Suter and Birch Lake sample results during the third quarter decreased to levels at the LLD and factor of two of the LLD, respectively. The fourth quarter samples were analyzed at the newly contracted laboratory, which used an LLD of approximately 19 pCi/L. These results were within the range of the expected natural tritium levels in shallow ground water and surface water, with the possible exception of the Allyn residence. The fourth quarter Suter resident sample results decreased to a level similar to the results of the control location.

The higher level results at Suter and Birch Lake were possibly due to the previous seepage from the PINGP discharge canal water into the ground water. This is thought to occur due to the elevation difference between the Vermillion River and the discharge canal. The Suter residence is located between the discharge canal and Birch Lake, which is attached to the Vermillion River. The PINGP discharge canal piping was lengthened during 1991, so that liquid discharges from the plant are released near the end of the discharge canal, diffused and discharged to the Mississippi River. In 1992, the underground liquid discharge pipe from the plant to the discharge canal piping was replaced with a double walled leak detectable piping system. It is expected that these modifications will eliminate the suspected radioactive effluent flow into the local ground water. Overall,1994 sample results show a c,ontinuing downward trend as compared to 1993 levels.

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I Praire Island Nuclear RADIATION ENVIRONMENTAL Rev.1 Generating Plant MONITORING PROGRAM 1994 ANNUAL REPORT Appendix D l

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Table D-4.1 Sample collection and analysis program for special well and surface water samples, Prairie Island Nuclear Generating Plant,1994.

l Medium No.

Location codes Collection type Analysis typec and frequencyb and typea l

Well water 7

P-24d, P-25 (C),

G/Q H-3 quarterly P-26, P-27, P-28, P-29, P-30 Ground water 2

P-31, P-32 G/Q H-3 l

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a Location codes are defined in table D-4.2. Control Station are indicated by (C). All other stations are indicators.

b Collection type is codes as follows: C/ = continuous; G/ = grab. Collection frequency is coded as follows: W = weekly; M = monthly; Q = quarterly; SA = semi-annually; A =

annually; X = no specified frequency or one time.

c Analysis type is coded as follows: GB = gross beta; GS = gamma spectroscopy; H-3 =

tritium; I-131 = iodine 131.

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Praire Island Nuclear RADIATION ENVIRONMENTAL Rev.1 Generating Plant MONITORING PROGRAM 1994 ANNUAL REPORT Appendix D Table D-4.2. Sampling locations for special well and surface water samples. Prairie Island Nuclear Generating Plant,1994.

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Code typea Collection site Type of sampleb Distance and direction from reactor l

P-24d Suter residence, deep well WW 0.6 mi. @ 158 /SSE P-25 C

Rohl farm WW 12.9 mi @ 352 /N P-26 PITC WW 0.4 mi. @ 258 /WSW P-27 Nauer residence WW 0.9 mi. @ l54 /SSE P-28 Allyn (Perkins)

WW 1.0 mi. @ 152 /SSE residence P-29 Childs residence WW 1.2 mi. @ 149 /SSE 1

P-30 PINGP Biology Station WW 0.2 mi. @ 32 /NNE P-31 Birch Lake j

Seepage #1 GW 0.7 mi. @ 179 /S P-32 Birch Lake Seepage #2 GW 0.8 mi. @ 169 /SSE a "C" denotes control location. All other locations are indicators.

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b Sample codes: WW = Well water; GW = Ground Water.

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Table D-4.3 Radiation Environmental Monitoring Program Summary: Special well and surface water samples.

Name of Facility Prairie Island Nuclear Power Station Docket No.

50 282, 50-306 Location of Facility Goodhue, Minnesota Reporting Period January - December 1994 (County, State)

Indicator Location with Highest Control Number Sample Type and Locations Quarterly Mean Locations Non.

Type Number of LLDb Mean (F)c Mean (F)c Mean (F)c Routine (Units)

Analyses Range Range c

Locationd a

c Range Resultse Well Water H-3 27 F,

280 (10/23)

P-24d, 370 (4/4) 61 (1/4) 1 (pCi/L)

(51-800)

Suter's deep well, (51-800) 61 0

0.6 mi. @ 158 /SSE Ground H-3 8

160 358 (4/4)

P-32, Birch Lake 400 (2/2) 61 (1/4) 1 Water (180-620)

Seepage #2, (180-620) 61 (pCi/L) 0.8 mi. @ 169 /SSE 0

a H-3 = tritium b

LLD = Nominal lower limit of detection based on 4.66 sigma error for background sample. Value shown is lowest for the period.

C Mean and range are based on detectable measurements only. Fraction of detectable measurements at specified locations is indicated in parentheses (F),

d Locations ars specified: (1) by name, and code (Table 2) and (2) by distance, direction and sector relative to reactor site.

8 Non-routine results are those which exceed ten times the control station value.

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1994 ANNUAL REPORT Appendix D Table D-4.4 Radiological Environmental Monitoring Program, Complete Data Table,1994.

SAMPLE DATES FEB.1994 MAY 1994 AUG.1994 OCT.1994 SAMPLE LOCATIONS pCi/L pCi/L pCi/L pCi/L Suter residence 800 470 160 51 Rohl Farm (Control)

<188

<186

<163 61 PITC

<l90

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<l60 96 Nauer residence

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<l60 99 Allyn (Perkin) residence 240 430 374 Child residence

<190

<190

<160 80 Environmental Lab

<!90

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<l9 Birch Lake Seepage #1 300 330 Birch Lake Seepage #2 620 180 l

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