ML043640215

Maine Yankee Final Status Survey Release Record FR-0111 Yard West Excavations Survey Unit 2

ML043640215
Person / Time
Site:	Maine Yankee
Issue date:	12/18/2004
From:	Donna Anderson, Dockins L N, Pillsbury G Maine Yankee Atomic Power Co
To:	NRC/FSME
References
MN-04-060, RA-04-118 FR-0111-02, Rev 0
Download: ML043640215 (19)

Text

MAINE YANKEE FINAL STATUS SURVEY RELEASE RECORD FR-01 11 YARD WEST EXCAVATIONS SURVEY UNIT 2 Prepared By: d. 4J O Date: fi~/4 (6 o FSS Engineer -Signature AAE.P, 50AJ Printed Name Reviewved By: AZP Date: iz -/ l oc 4 FSS'pecialist

-Signature Printed Name Reviewed By: -Signatur Date: Approved By.:A Date: 7Z/,7/ S-~penerntedevitr-eSignUe Printed Name /Approved By: __,Z__ / Date: "FSS, MOP -Signature Printed Name MAINE YANKEE FINAL STATUS SURVEY RELEASE RECORD FR-0 11I YARD WEST EXCAVATIONS SURVEY UNIT 2 A. SURVEY UNIT DESCRIPTION FR 01 I Yard West Excavations Survey Unit 2 consisted of a 32-ft. diameter excavation that was created following the discovery of potentially elevated sub-surface soil activity during characterization activities within the Restricted Area back yard. The excavation was centered at coordinates 407,837 N and 623,930 E using Maine State Coordinate System (West Zone) NAD 1927 and lay northeast of the former Primary Auxiliary Building (PAB).The location of the 114.5 m 2 survey unit in relation to the former Containment Building and the surrounding FR 0111 survey units is shown on map FROI 1I U2-01 (Attachment 1).During characterization activities, several locations within the Restricted Area back yard were identified as potentially containing plant-derived activity greater than the DCGL. One of the locations (S042 as identified in Characterization Package CR 5000) required extensive excavation, resulting in a large hole with an area of 1 14.5 m 2 and an average diameter of 9.75 meters (32 ft). The excavation was slightly elongated and notched around a storm drain manway with vertical walls approximately

1.2 meters

(4 ft.) deep. An abandoned concrete duct bank was also discovered during soil removal. The duct bank was approximately 2-ft.6-in. below grade and penetrated through and across the north edge of the survey unit. The exposed duct bank was surveyed as part of the survey unit direct points.B. SURVEY UNIT DESIGN INFORMATION Survey Unit 2 met the LTP Revision 3 definition for a Class I survey unit. The survey unit design parameters are shown in Table 1. Given an adjusted relative shift of 1.5, it was determined that 18 direct measurements were required for the Sign Test. Measurement locations were based on a systematic square grid with a random start point and are illustrated on map FROI 11 U2-03, Direct -Volumetrics (Attachment 1). Direct measurements consisting of soil samples or concrete samples (taken from direct locations on the abandoned concrete duct bank) were collected from required locations and analyzed with laboratory gamma spectroscopy instrumentation.

In accordance with the LTP, scans covering 100% of the 1 14.5 m 2 area were required for the Class 1 survey unit. This was accomplished by use of an in siltl gamma spectroscopy detector positioned at the surface plane of the excavation using a wvell geometry to perform the scans (approximate field of view of 100 m 2 at 2 m height). This scan survey ensured there were no unevaluated areas exceeding the DCGLENIC limit. Locations of the Unit 2 survey scans are shown on map FROI I 1U2-02.FR-0 111-02, Revision 0 Page 2 of 19 The survey instruments used are listed by model and serial number in Attachment 2 (Table 2-1). Scan MDCs are also listed in Attachment 2 (Table 2-2) and are compared to the DCGL, the investigation level, and the DCGLENIc.

As shown in this table, the scan MDC is less than the scan investigation level in all cases, thus providing high confidence (95% or higher) that an elevated area would be detected in the scanning process. Further, since the investigation level was always less than the design DCGLENC, no EMC sample size adjustment was necessary.

TABLE I SURVEY UNIT DESIGN PARAMETERS Survey Unit Dcsign Criteria l Basis Area 1 14.5 m' Class 1, < 2,000 m'Based on an adjusted LBGR of Number of Direct 18' 0.275 pCi/g, sigma 2 of 1.33 pCi/g, Measurements Required and a relative shift of 1.5.Type I = Type 11 = 0.05 Sample Area 6.36 m' 114.5 m'/ 18 = 6.36 mL Sample Grid Spacing 2.52 m (6.36)12h ISOCS scan at 2 m (8 m Scan Grid Area diameter hole) for 100 m 2 field of view Area Factor 3.1 Class I Area, LTP Table 6-12 Scan Area 114.5 m' Class I Area -100%Scan Investigation Level 3.70 pCi/g Cs-137 ISOCS investigation level set at Scan 50% of DCGLEM~C DCGL 2.39 pCi/g Cs-I 37 LTP Revision 3, Table 6-11 Design________________

7x(Reference 4)Design DCGLENIC 7.40 pCi/g Cs- 137 DCGL x Area Factor for Class 1____ ___ ____ ___ ____ _ _ ____ ___ ____ ___ ___ survey unit, per LTP Section 5.6.3 C. SURVEY RESULTS As required, a total of 18 direct measurements were performed in Survey Unit 2. All direct measurements were below the DCGL. The results are presented in Table 2.ISOCS gamma scans were performed at two locations using an investigation level of 3.70 pCi/g Cs-137 (50% of DCGLENMc).

Data was subsequently evaluated to 0.5 pCi/g (<DCGL).The gamma scans were performed for a sufficient count time to achieve a Minimum Detectable Activity of approximately 10% of the DCGL. All identified activity levels were below the investigation levels (i.e., < MDA). Therefore, no investigations were required.This survey unit was initially designed for N=40 samples. The design LBGR was developed by dividing the excavation area (Ae) by the maximum Class I area (Al) and applying a correction factor of 2 to determine the LBGR as a percentage of the DCGL.2 LTP Revision 3, Table 5-iC for RCA Yard West, ROI00.FR-O1 11-02, Revision 0 Page 3 of 19 TABLE 2 DIRECT MEASUREMENTS Sample Number Cs-137 (pCi/g)FRO111021SO01

< 2.22E-02 FR0111021S002

< 2.11 E-02 FR0111021S003

< 2.4813-02 FRO I 11021S004

< 2.2713-02 FR0111021S005

< 2.5313-02 FR0111021S006

< 2.08E-02 FRO 11021S007

< 2.5013-02 FRO111021SO08

< 2.49E-02 FRO111021SO09

< 2.1313-02 FROI11021SO10

< 2.911E-02 FR0111021SO1I

< 2.2813-02 FRO111021SO12

< 2.4213-02 FRO1I1021SO13

< 2.211E-02 FR0111021S014

< 2.3913-02 FROI1021S015 Concrete < 1.1413-01 FRO11021SO16 Concrete < 1.25E-01 FR0111021S017 Concrete < 9.94E-02 FR0111021S018

< 2.111E-02 Mean 3.83E-02 Median 2.41E-02 Standard Deviation 3.46E-02 Range 2.08E-02 to 1.25E-01"<" indicates MDA value. Samples were also analyzed for Co-60. All were less than MDA.D. SURVEY UNIT INVESTIGATIONS PERFORMED AND RESULTS No investigations were required.FR-0l l 1-02, Revision 0 Page 4 of 19 E. SURVEY UNIT DATA ASSESSMENT An analysis of the direct sample measurement results, including the mean, median, standard deviation, and sample result range, is provided in Table 2. Cs-137 and Co-60 were not present above the MDA in any of the 18 soil samples collected.

As noted in Table 1, the initial survey design required 40 samples with a density of I sample/2.9 mi 2.Due to the expected levels of contamination, 40 samples was deemed excessive and the LBGR was lowered to raise the relative shift. As showtn in Table 2, the actual survey unit mean is much less than the design LBGR. In addition, the final standard deviation was much less than the design sigma. Thus, the design relative shift remains valid, indicating a sufficient number of samples were taken.For illustrative purposes, as indicated in LTP Section 5.9.3, a simplified general retrospective dose estimate can be calculated from the average residual contamination level by subtracting the mean fallout Cs-137 value (0.19 pCifg)3 for disturbed soil from the survey unit sample mean activity (0.0383 pCi/g). This would equate to an annual dose rate of 0.0 mremlyear 4.However, for purposes of demonstrating compliance with the radiological criteria for license termination and the enhanced State criteria, background activity was not subtracted from the soil sample analysis activity values.F. ADDITIONAL DATA EVALUATION Attachment 4 provides additional data evaluation associated with this Survey Unit, including relevant statistical information.

Based on survey unit direct measurement data, this attachment provides the Sign Test Summary, Quantile Plot, Histogram, and Retrospective Power Curve.1. The Sign Test Summary provides an overall summary of design input (Table 1) and resulting calculated values used to determine the required number (N) of direct measurements (per LTP Section 5.4.2). The Sign Test Summary is a separate statistical analysis that also calculates the mean, median, and standard deviation of the direct measurements.

The critical value and the result of the Sign Test are provided in the Sign Test Summary table, as well as a listing of the key release criteria.

As is shown in the table, all of the key release criteria were clearly satisfied for the FSS of this survey unit.2. The Quantile Plot was generated from the unity value data listed in Table 2. The data set and plot are consistent with expectations for a Class 1 survey unit. All of the measurements are well below the DCGL of 2.39 pCi/g for land inside the Restricted Area.3 See Attachment E to Maine Yankee Procedure PMP 6.7.8 (Reference 5).4 This annual dose equivalent is based on LTP Table 6-11 which shows the RA contaminated soil contribution (for soils contaminated at the DCGL) to be 5.63 mrem/y. Therefore, the annual dose rate would equate to (0.0383 -0.19~Annual Dose Rate = 5.63 x 239 = 0.0 mrem / y 2.39 FR-Ol 11-02, Revision 0 Page 5 of 19

3. A Histogram Plot was also developed based on the unity values. This plot shows a distribution skewed by the three concrete measurements.

4. A Retrospective Power Curve was constructed, based on FSS results. The curve shows that this survey unit having a mean residual activity at a small fraction of the DCGL has a high probability

("power")

of meeting the release criteria.

Thus, it can be concluded that the direct measurement data support rejection of the null hypothesis, providing high confidence that the survey unit satisfied the release criteria and that the data quality objectives were met.G. CHANGES IN INITIAL SURVEY UNIT ASSUMPTIONS ON EXTENT OF RESIDUAL ACTIVITY The survey was designed as a Class I land survey area; the FSS results were consistent with that classification.

The direct measurement sample standard deviation was less than the design sigma. Thus, a sufficient number of sample measurements were taken and no additional measurements were required.lI. LTP CHANGES SUBSEQUENT TO SURVEY UNIT FSS The FSS of Survey Unit 2 was designed, performed and evaluated in March 2004. The design was performed to the criteria of the LTP Revision 3 (References 3 and 4). No subsequent LTP changes with potential impact to this survey unit need to be evaluated.

I. CONCLUSION The FSS of this survey unit was designed based on the LTP designation as a Class I area.The survey design parameters are presented in Table 1. The required number of direct measurements was determined for the Sign Test in accordance with the LTP. As presented in Table 2, all direct measurements were less than the DCGL of 2.39 pCi/g Cs-137.A Sign Test Summary analysis demonstrated that the Sign Test criteria wvere satisfied.

The direct measurement sigma was determined to be less than that used for design, thus indicating that a sufficient number of samples was taken.The Retrospective Power Curve shown in Attachment 4 confirmed that sufficient samples were taken to support rejection of the null hypothesis, providing high confidence that the survey unit satisfied the release criteria and the data quality objectives were met. Attachment 4 also revealed that direct measurement data represented essentially a skewed distribution with three outliers.The scan survey design for this survey unit was developed in accordance with the LTP Revision 3 Addenda (Reference

1) with significant aspects of the design discussed in Section B and Table 1. ISOCS scans performed using a well geometry did not identify activity above the scan investigation level of 0.5 pCi/g Cs-137 (< DCGL).It is concluded that FR 011 1 Survey Unit 2 meets the release criteria of I OCFR20.1402 and the State of Maine enhanced criteria.FR-0 I 1 1-02, Revision 0 Page 6 of 19

3. REFERENCES

1. Maine Yankee License Termination Plan, Revision 3, October 15, 2002 and Addenda provided by Maine Yankee letter to the NRC, MN-02-06 1, dated November 26, 2002 2. NRC letter to Maine Yankee, dated February 28, 2003 3. Maine Yankee letter to the NRC, MN-03-049, dated September 11, 2003 (LTP Supplement to LTP Revision 3)4. Issuance of License Amendment No. 170, NRC letter to Maine Yankee, dated February 18, 2004 5. Maine Yankee Procedure PMP 6.7.8, FSS Data Processing and Reporting, Attachment E, Approach for Dealing With Background Radioactivity for Maine Yankee Final Status Surveys FR- 1 11-02, Revision 0 Page 7 of 19 Attachment 1 Survey Unit Maps FR-01 11-02, Revision 0 Page 8 of 19

-.-In Maine Yankee Decommissionina Team._ _ _= _ _ _ _ ._Survey Type: _ Characterization

_ _ _ _ _ _Maine Yankee Decommissioning Project Survey Map Map ID# FRO1 11 U2-01h1 Turnover

• Final Status Survey Survey Area Name: Site Locator PreparedBy:

Larry N. Dockins Dote: 12/13/04\\ L,.oi0 sO lWoos NL LIEo07J°°14H }t .07 \ o\ \ \ ° ..gg _Lot at X CC \_O t90t C, 00 rn 0 0 M1 FR-O1 11-02, Revision 0 Page 9 of 19 Maine Yankee* Min e Yankee Decor missioning Team Survey Type: Characterizatlon Maine Yankee Decommissioning Project Survey Map Map ID# FRO 11 1 U2-02 Turnover i Final Status Survey Survey Area Name: Scans -ISOCS PieparedBy:

Larry N. Dockins Dwe: 3/3/04 Storm Drain Manwav Cover 1-I-m-, _ M , A IV4 4%I*I I I 10 ft.as .f sos; Wa ts'V..' /I%n J,I I I II I I I I( -t- o I I I I I I I I I I I I'4 I4.4 It.4 S020 I I I I I I I I---low r- --------I I I I I 4 4 4 loft.,m mim ..., _, _ .-0 10f t Abandoned Construction Phase Duct Bank (2' 6" below grade)FR-Oi 11-02, Revision 0 Page 10 of 19 Maine Yankee Maine Yonkee Decommissiong Team _Survey Type: Characterization Maine Yankee Decommissioning Project Survey Map Mop ID# FROl 11 U2-03 Turnover

• FinalStatus Survey SurveyArea Narme: Direct -Volumetrics Prepared By: Larry N. Dockins Date: 3/3/04 I I I I I I l I I I Io FR-O1 11-02, Revision 0 Page II of 19 lrOm Attachment 2 Survey Unit Instrumentation FR-01 11-02, Revision 0 Page 12 of 19 TABLE 2-1 INSTRUMENT INFORMATION ISOCS Detectors (Field Measurements)

Detector Number MDC (pCi/g)7722 1 0.1 to 0.2 HPGc Detectors (Laboratory Analysis)I Detector Number I MDC (pCi/g)I FSSI 0.02 to 0.03 FSS2 0.02 to 0.03 DET3 0.10 to 0.15 TABLE 2-2 INSTRUMENT SCAN MDC, DCGL, INVESTIGATION LEVEL, AND DCGLENIC Detector Instrument I Comments Scan MDC ISOCS: 0.1 to 0.2 pCi/g 10% DCGL 2.39 pCi/g Cs-I 37 Approved DCGL for land areas DCGL inside the Restricted Area, 0.86 pCi/g Co-60 (Reference 4)Investigation Level (ISOCS well geometry @ 2 m) 0.5 pCilg Cs-137 <DCGL 7.40 pCi/g Cs-1 37 DCGL x Area Factor for Class 1 Design DCCLEMc 2.67 pCi/g Co-60 survey unit, per LTP Section 5.6.3 FR-01 11-02, Revision 0 Page 13 of 19 Attachment 3 Investigation Table (No Investigations Performed)

FR-01 11-02, Revision 0 Page 14 of 19 Attachment 4 Statistical Data FR-O1 11-02, Revision 0 Page 15 of 19 Survey Package FR 0111 Unit 2 Soil Sign Test Summary i >ti;>,.5,E: .KE utio~nInput aluest,<i^-,g;'

a .-ornn'^'m Survey Package: FR 0111 Survey Unit: 02 Evaluator:

DA DCGL,: 2.39E+00 DCGLemc: 7.40E+00 LBGR: 2.75E-01 Sigma: 1.33E+00 Type I error: 0.05 Type II error: 0.05 Nuclide: CS-1 37 Soil Type: N/A Fs~.,~t,,g-^7.,3+~il~Ca cuaii~a.vaiues~,,

4, ; ,~' "<'-i; Zl, < 1.645 Za: 1.645 Sign p: 0.933193 Calculated Relative Shift: 1.5 Relative Shift Used: 1.5 Uses 3.0 if Relative Shift is >3 N-Value: 15 N-Value+20%:

18 2;i-s t~>-~i -'Sanmple DataVatlie a+ 5<.> *J e '8' Im ens 'Number of Samples: 18 Median: 2.41 E-02 Mean: 3.83E-02 Net Sample Standard Deviation:

3.46E-02 Total Standard Deviation:

3.46E-02 Maximum: 1.25E-01 Adjusted N Value: 18 S+ Value: 18 Critical Value: 12 Sign test results:, Pass_____________,! -Comm eht I Sufficient samples collected:

Pass Maximum value <DCGLw: Pass Median value <DCGLN: Pass Mean value <DCGLN: Pass Maximum value <DCGLemc:

Pass Total Standard Deviation

<=Sigma: Pass Criteria comparison results: Pass The survey unit passes all conditions Pass FR 011 1-SU2-SolSign.xls 12113104 5:02 PM FR-01 11-02, Revision 0 Page 16 of 19 FR-0111 SU-2 Quantile Plot 0.14 0.12 In.,C 0 OQ 0 <O x O 5.0 c 0._U*-I.U._U5 0.1 0.08 0.06 , ~-- _ ________ .-..Activity (pCi/g)-Median (pCi/g).0.04* -*-*-

• V IV * * +6 I A &0.02 0 0 25 50 75 100 Percent One-Sample T-Test Report Page/Date/Time Database Variable 2 12/13/044:01:10PM C2 Plots Section Histogram of FR-01 11, SU-2 U, Ca E.0 E z Activity (pCig)FR-01 11-02, Revision 0 Page 18 of 19 One-Sample T-Test Power Analysis Page/Date/Time 2 12/13/04 4:02:27 PM Chart Section Retrospective Power Curve 1.0---.---

--0.8 ---0.6-'0)0.4 .----0.2 ------0.0 a 0.0 0.5 1.0 1.5 2.0 2.5 Survey Unit Mean (pCilg)FR-OJ 11-02, Revision 0 Page 19 of 19