ML051050080

Final Status Survey Release Record FR-0111 Yard West Excavations Survey Unit 17

ML051050080
Person / Time
Site:	Maine Yankee
Issue date:	04/05/2005
From:	Dockins L, Olsen C, Packer J, Pillsbury G, Randall D Maine Yankee Atomic Power Co
To:	NRC/FSME
References
FR-0111-17, Rev 0
Download: ML051050080 (21)

Text

r MAINE YANKEE FINAL STATUS SURVEY RELEASE RECORD FR-0111 YARD WEST EXCAVATIONS SURVEY UNIT 17 Revision 0

MAINE YANKEE FINAL STATUS SURVEY RELEASE RECORD FR-0111 YARD WEST EXCAVATIONS SURVEY UNIT 17 A. SURVEY UNIT DESCRIPTION FR-0 111, Yard West Excavations Survey, Unit 17 was located southeast of the former Containment Building. The 1,563 m2 area was bordered on the north by FR-01 11 Survey Unit 18, on the wvest by FR-01 11 Survey Unit 13 and FR-01 00 Survey Units 2 and 3. Survey Area FR-0200 borders the unit to the East. The survey unit was centered near coordinates 407,386 N and 623,930 E using Maine State Coordinate System (West Zone) NAD 1927.

The location of the survey unit in relation to the Containment Building and the surrounding FR-01 11 survey units is shown on map FROI 1 U 17-SITE (Attachment 1). Details for the survey unit's size and topography are shown on map FROI I IU17-INFO.

B. SURVEY UNIT DESIGN INFORMATION Survey Unit 17 met the LTP Revision 4 definition for a Class I survey unit. The survey unit design parameters are shown in Table 1. Given a relative shift of 0.8, it was determined that 40 direct measurements were required for the Sign Test. The measurement locations were based on a systematic square grid with a random start point as illustrated on map FROI I 1U17-DIRT (Attachment 1). Direct measurements (soil samples) were collected from required locations and analyzed with laboratory gamma spectroscopy instrumentation.

In accordance with the LTP, scans covering 100% of the 1,563 m2 area were required for the Class I survey unit. This was accomplished by use of an in situ gamma spectroscopy detector (ISOCS) configured at a 2 or 3-meter distance from the surface to obtain overlapping 12 m2 or 28 m2 fields of view, respectively. The ISOCS detector was positioned perpendicular to the surface. Locations of the 95 survey scans are shown on maps FROI I U17-SCAN and FROI 1U17-CONC.

The ISOCS scans were configured to ensure 100% scan coverage of all exposed surfaces within Survey Unit 17. 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 DCGLEMC. The scan MDC is less than the scan investigation level, 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 DCGLEMC, no EMC sample size adjustment was necessary.

FR-O1 11-17, Revision 0 Page 2 of 21

TABLE I SURVEY UNIT DESIGN PARAMETERS Survey Unit Design Criteria Basis Area 1,563 m 2 Class 1, < 2,000 m2 Based on an LBGR of 1.2 pCi/g, Number of Direct 40 sigmal of 1.33 pCi/g, and a Measurements Required relative shift of 0.8.

Type I = Type II = 0.05 Sample Area 39.1 m 2 1,563 m 2 / 40 = 39.1 m 2 Sample Grid Spacing 6.2 m (39.1)112 Scan Grid Area ISOCS scan 2 and 3-meters See Section B Area Factor 1.6 Class I Area, LTP Table 6-12 Scan Area 1,563 m2 Class I Area - 100%

1.0 pCi/g Cs-137 ISOCS investigation levels with Scan Investigation Level detector at 2-meter and 3-meter 0.36 pCi/g Co-60 heights (Reference 3)

DCGL 2.39 pCi/g Cs-137 Reference 1

____ _____ ____ 0.86 pC i/g C o-60 _ _ _ _ _ _ _ _ _ _ _ _ _ _

3.82 pCilg Cs-137 DCGL x Area Factor for Class 1 Design DCGLEMC 1.38 pCiyg Co-60 survey unit, per LTP Section 5.6.3 C. SURVEY RESULTS A total of 40 direct measurements were performed in Survey Unit 17. Five samples contained detectable Cs-137 levels of residual activity below the DCGL. In addition, one sample contained detectable levels of Co-60 (this sample did not contain detectable levels of Cs-137). All other measurements were below the MDA. The results are presented in Table 2.

ISOCS gamma scans were performed at 95 locations using an investigation level of 1.0 pCi/g Cs-137 and 0.36 pCi/g Co-60 for the 28 m2 and 12 m2 field of view. Twelve of the locations scanned consisted of primarily concrete media, the balance were soil scan measurements.

Media-appropriate geometries were applied to each ISOCS measurement. The gamma scans were performed for a sufficient count time to achieve a Minimum Detectable Activity (MDA) below the respective investigation levels. All identified scan activity levels were below the investigation levels. Therefore, no investigation surveys were performed as a result of the scan surveys.

LTP Revision 4, Table 5-IC for RCA Yard West, ROIOO FR-O1 11-17, Revision 0 Page 3 of 21

TABLE 2 DIRECT MEASUREMENTS Cs-137 Uncert. Co-60 Uncert. Unitized Sample Number (Pi) PCi/g) (Pcilg) (pi/g) Value of (PClg)Unity Rule FRO11171 SOO1 < 4.72E-02 ' 4.91E-02 7.68E-02 FRO11117IS002 < 4.54E-02 < 5.62E-02 8.43E-02 FRO 11171S003 < 4.35E-02 < 4.63E-02 7.20E-02 FRO 11171S004 < 4.55E-02 < 4.82E-02 7.51E-02 FROI171S005 < 4.26E-02 < 4.89E-02 7.47E-02 FRO1III171SO06 < 5.57E-02 < 5.54E-02 8.77E-02 FRO 11171S007 < 6.25E-02 < 6.OOE-02 9.59E-02 FRO 1171S008 < 5.62E-02 < 6.04E-02 9.37E-02 FRO 11171SOO9 1.85E-01 3.66E-02 < 4.59E-02 1.31E-O1 FRO11171SOI0 < 4.95E-02 < 5.01E-02 7.90E-02 FRO11171SOI I < 4.92E-02 < 4.24E-02 6.99E-02 FR0111171S012 < 5.91E-02 < 5.84E-02 9.26E-02 FRO 11171SO13 < 5.98E-02 < 6.46E-02 l.OOE-01 FRO1171SO14 < 4.74E-02 < 4.58E-02 7.31E-02 FROII1171SO15 < 5.56E-02 < 5.OOE-02 8.14E-02 FR0111171S016 < 5.07E-02 < 5.31E-02 8.30E-02 FRO 11171SO17 < 6.38E-02 < 5.85E-02 9.47E-02 FROII1171S018 < 4.37E-02 < 4.51E-02 7.07E-02 FR0111171SO19 < 4.26E-02 < 4.80E-02 7.36E-02 FRO 11171S020 < 5.62E-02 < 6.23E-02 9.60E-02 FRO1171S021 < 4.51E-02 < 5.09E-02 7.81E-02 FR0111171S022 < 4.53E-02 < 4.18E-02 6.76E-02 FR0111171S023 < 5.96E-02 < 6.35E-02 9.88E-02 FR0111171S024 < 5.38E-02 < 5.52E-02 8.67E-02 FR0111171S025 1.13E-01 2.95E-02 < 6.48E-02 l.23E-O1 FR011171S026 < 5.94E-02 < 5.95E-02 9.40E-02 FR0111171S027 1.69E-01 4.03E-02 < 6.16E-02 1.42E-O1 FROI 1171S028 8.54E-01 8.41E-02 < 6.62E-02 4.34E-O1 FR0111171S029 I.41E-01 3.66E-02 < 6.24E-02 1.31E-O1 FRO 11171S030 < 3.77E-02 _ < 4.04E-02 6.28E-02 FROI 1171S031 < 4.96E-02 9.34E-02 2.94E-02 1.29E-OI FR0111171S032 < 4.62E-02 < 4.24E-02 6.86E-02 FR0111171S033 < 5.12E-02 < 5.27E-02 8.27E-02 FR0111171S034 < S.18E-02 < 5.81E-02 8.92E-02 FRO011171S035 < 5.34E-02 < 5.82E-02 9.OOE-02 FR0111171S036 < 4.82E-02 < 4.97E-02 7.80E-02 FR0111171S037 < 6.23E-02 < 6.06E-02 9.65E-02 FR0111171S038 < 6.28E-02 < 5.77E-02 9.34E-02 FR0111171S039 < 6.69E-02 < 6.32E-02 1.0lE-OI FR0111171S040 < 5.34E-02 < 3.93E-02 6.80E-02 Mean 8.21E-02 5.48E-02 9.80E-02 Median 5.34E-02 5.53E-02 8.72E-02 Deviation .29E-01 9.87E-03 5.78E-02 Range 3.77E-02 to 3.93E-02 to 6.28E-02 to g 8.54E-01 9.34E-01 4.34E-O1

"<" indicates MDA value. Bold indicates positive detection value.

FR-01 11-17, Revision 0 Page 4 of 21

D. SURVEY UNIT INVESTIGATIONS PERFORMED AND RESULTS Based on the scan results, no investigations were required.

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. Positively detected values are bolded in the table. Since Co-60 and Cs-137 are the primary nuclides of concern, non-detect values for these nuclides were assumed to be present at the MDA. Of the 40 soil samples collected, five identified detectable Cs-137 activity below the DCGL value of 2.39 pCi/g. In addition, one sample contained detectable levels of Co-60 (this sample did not contain detectable levels of Cs-I 37). All other values were below the MDA. Table 2 lists the greater of the identified sample activity or MDA for each sample. The mean and median activities were less than the DCGLs for Cs-137 and Co-60. The average of the DCGL unity fractions was 0.098, indicating that the direct measurements averaged 9.8% of the DCGL limit.

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 pCi/g) 2 for disturbed soil from the survey unit sample mean activity (0.082 pCi/g). This would equate to an annual dose rate of 0.0 mrem/year.

Taking into account the average residual contamination level for Co-60, the annual dose rate would equate to 0.49 mrem/year3 . For purposes of demonstrating compliance with the radiological criteria for license termination and the enhanced State criteria, background activity was not subtracted from the sample analysis activity values.

2 See Attachment E to Maine Yankee Procedure PMP 6.7.8 (Reference 2).

3 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 7.67 mnremfy. Therefore, the annual dose rate would equate to (0.0548)

Annual Dose Rate = 7.67 x ) =0-49 mrem / y FR-01 11-17, Revision 0 Page 5 of 21

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. The direct measurements clearly pass the Sign Test. In addition, all other key release criteria have been satisfied. The sample standard deviation is smaller than the design sigma; therefore, no additional samples were required.

2. The Quantile Plot was generated from the unity data listed in Table 2. The data set and plot are consistent with expectations for a Class I survey unit. All of the measurements are below the DCGLs of 2.39 pCi/g for Cs-1 37 and 0.86 pCi/g for Co-60 for land inside the restricted area.

3. A Histogram Plot was also developed based on the unity data values. This plot shows a log-normal distribution with one outlier.

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 1 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.

FR-O1 11-17, Revision 0 Page 6 of 21

Il. LTP CHANGES SUBSEQUENT TO SURVEY UNIT FSS The FSS of Survey Unit 17 was designed, performed, and evaluated in the March 2005 time frame. The design was performed to the criteria of the LTP Revision 4 (Reference 1). 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 DCGLs of 2.39 pCi/g Cs-1 37 and 0.86 pCi/g Co-60. No measurements exceeded the unitized DCGL.

A Sign Test Summary analysis demonstrated that the Sign Test criteria were 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 log-normal distribution with one outlier.

The scan survey design for this survey unit was developed in accordance with the LTP Revision 4 (Reference 1) with significant aspects of the design discussed in Section B and Table 1. ISOCS scans performed in a systematic grid pattern throughout the survey unit did not identify activity above the scan investigation levels. Therefore, no investigations were required as a result of the scan process.

It is concluded that FR-01 11 Survey Unit 17 meets the release criteria of IOCFR20.1402 and the State of Maine enhanced criteria.

J. REFERENCES

1. Maine Yankee License Termination Plan, Revision 4, February 28, 2005 provided by Maine Yankee letter to the NRC, MN-05-010

2. 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

3. Maine Yankee Calculation No. EC-003-04, Use of Canberra In Situ Object Counting System (ISOCS) for FSS Surveys FR-O1 11-17, Revision 0 Page 7 of 21

Attachment 1 Survey Unit Maps FR-O1 11-17, Revision 0 Page 8 of 21

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Attachment 2 Survey Unit Instrumentation FR-OI 11-17, Revision 0 Page 14 of 21

TABLE 2-1 INSTRUMENT INFORMATION ISOCS Detectors (Field Mcasurements)

Detector No. MDC (pCi/g) 7605 0.169 to 0.308 7607 0.128 to 0.454 7780 0.090 to 0.316 HPGe Detectors (Laboratory Analysis)

Detector No. MDC (pCi/g)

FSS1 j 0.037 to 0.067 FSS2 j 0.037 to 0.066 TABLE 2-2 INSTRUMENT SCAN MDC, DCGL, INVESTIGATION LEVEL AND DCGLEMC Parameter Instrument: ISOCS Comments Scan MDC 0.090 to 0.454 pCi/g 2.39 pCi/g Cs-137 Approved DCGL for land DCGL pCi/g Col60 a.86 reas inside the Restricted 0.86 ~i/go-60Area, (Reference 1)

Investigation Level 1.0 pCi/g Cs-137 (ISOCS @ 2 and 3 m) 0.36 pCi/g Co-60 (Reference 3) 3.82 pCi/g CI37 IDCGL x Area Factor for Design DCGLEMc 1.38 pCi/g Co-60 Class 1 survey unit, per LTP 1.38 ~i/go-60Section 5.6.3 FR-O 11-17, Revision 0 Page 15 of 21

Attachment 3 Investigation Table (not Used)

FR-O1 11-17, Revision 0 Page 16 of 21

Attachment 4 Statistical Data FR-O1 11-17, Revision 0 Page 17 of 21

Survey Package FRO111 Unit 17 UNITY Soil Sign Test Summary

• ;,Evaluation nrpoutsV lent<%g}. mif Survey Package: FRO111 Survey Unit: 17 Evaluator: DR DCGLW: 1.OOE+00 Unity DCGL,.: 1.60E+00 LBGR: 5.00E-01 Sigma: 5.56E-01 (1.33 pCi/g /2.39 pCVg)

Type I error: 0.05 Type II error: 0.05 Nuclide: UNITY Soil Type: N/A

' Zeu1.645 Z1.0: 1.645 Sign p: 0.788145 Calculated Relative Shift: 0.8 Relative Shift Used: .: 0.8 Uses 3.0 if Relative Shift Is >3 N-Value: 33 N-Value+20%: . 40 Number of Samples: 40 Median: 8.72E-02 Mean: 9.80E-02 Net Sample Standard Deviation: 5.78E-02 Total Standard Deviation: 5.78E-02 Sum of samples and reference Maximum: .4.34E-01 7, i. s' rewt . J'sK; Adjusted N Value:  ;- 40 S+ Value: 40 _

Critical Value: 25 Sign test results: . - Pass

4-,C ;ri . . ,- m Sufficient samples collected

Pass Maximum value <DCGL,: Pass Median value <DCGL,: Pass Mean value <DCGLW: Pass Maximum value <DCGLemc: Pass Total Standard Deviation <=Sigma: i .- Pass .-

Criteria comparison results: 1k:9i. Pass I FJn ' *-i I- __

The survey unit passes all conditions:l . - Pass SU Passes FROl 11-SU17-SoilSign-UNITY FR-OI 11-17, Revision 0 414105 12:25 PM Page 18 of 21

FRO111-17 Quantile Plot 5.E-01 4.E -:

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One-Sample T-Test Report Page/Date/Time 2 3/21/05 8:20:32 AM Database Variable C2 Plots Section Histogram of FR-i 1, SU-17 40-(A CD a- 30-E co 20.

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FR-01 11-17, Revision 0 Page 20 of 21

One-Sample T-Test Power Analysis Page/Date/Time 2 3/21105 8:21:45 AM Chart Section Retrospective Power Curve

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FR-01 11-17, Revision 0 Page 21 of 21