ML050590055

Final Status Survey Release Record FR-0100 RCA Yard West Survey Unit 1

ML050590055
Person / Time
Site:	Maine Yankee
Issue date:	02/17/2005
From:	Donna Anderson, Cooper W, Dockins L, Packer J, Pillsbury G Maine Yankee Atomic Power Co
To:	Document Control Desk, NRC/FSME
References
FR-0100-01, Rev 0
Download: ML050590055 (19)

Text

MAINE YANKEE FINAL STATUS SURVEY RELEASE RECORD FR-0100 RCA YARD WEST SURVEY UNIT I Prepared By: 0cr. ndto vex Date: a/o6 FSS Engineer - Signature D ./ Ama7ZoAJ Printed Name Reviewed By: G o d Date:

FS~e Specialist - Signature Lo0. 'v/ j)C. VI - S Printed Name Reviewed By: Date: _____

re-pendc Review - Signature Printed Na Approved By: / Date: V 7Avs

/ iFSS, MOP - Signature 7ds I MZ 'Yey Printed Name Revision 0

MAINE YANKEE FINAL STATUS SURVEY RELEASE RECORD FR-O100 RCA YARD WEST SURVEY UNIT I A. SURVEY UNIT DESCRIPTION FR-O1 00 RCA Yard West Survey Unit I occupied the southwest corner of the original Restricted Area "backyard." The 1,845 m2 area was previously excavated and remediated as part of the decommissioning process. After remediation, the remaining soils were surveyed under final survey packages FR-O I I I Survey Units 4, 5, 6 and 7. Following final survey of the excavations, the area was backfilled to grade (approximate 20-ft. El.). Construction debris from Containment demolition activities was temporarily stored in the backfilled area.

The debris and approximately 1 to 2 feet of fill material were subsequently removed. The footprint of this area became FR-01 00 Survey Unit 1. The southeast portion of this survey unit slopes gently towards the old Forebay area. FR-O 100 Survey Unit I is located at coordinates 407,450N and 623,650E, using Maine State Coordinate System (West Zone)

NAD 1927. The location of the survey unit in relation to the former Containment Building and the surrounding FR 0100 survey units is shown on Map FROlOOU1-SITE (Attachment 1).

B. SURVEY UNIT DESIGN INFORMATION Survey Unit I met the LTP Revision 3 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 and are illustrated on map FROIOOU1-DIRT (Attachment 1). Direct measurements (soil samples) wvere collected from required locations and analyzed with laboratory gamma spectroscopy instrumentation.

In accordance with the LTP, scans covering 100% of the 1,845 m2 area were required for the Class 1 survey unit. This was accomplished by use of an in siozx gamma spectroscopy detector (ISOCS) configured at a 3-meter distance from the surface to obtain overlapping 28-m2 fields of view. The detector was positioned perpendicular to the soil surfaces and used a 90-degree collimator to perform the surface scans. Locations of the 94 survey scans are shown on map FROIOOU I-SCAN.

The ISOCS scans were configured to ensure 100% scan coverage of all exposed surfaces within Survey Unit 1. 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, 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-0 I00-01, Revision 0 Page 2 of 19

TABLE I SURVEY UNIT DESIGN PARAMETERS Survey Unit Design Criteria Basis Area 1,845 m2 Class 1, < 2,000 m 2 Based on an LBGR of 1.2 Number of Direct 40 pCi/g, sigma' of 1.33 pCi/g and Measurements Required a relative shift of 0.8.

Tye I = Type I1= 0.05 1,845 m2 /40 =46.13m 2 Sample Area 46.13 m 2 Sample Grid Spacing 6.79 m (46.13)"2 Scan Grid Area ISOCS scan at 3-meters Reference 6 Area Factor 1.5 Class 1 Area, LTP Table 6-12 Scan Area 1,845 m2 Class I Area - 100%

1.0 pCi/g Cs-137 ISOCS investigation levels with Scan Investigation Level 0.36 pCi/g Co-60 detector at 3-meter height (Reference 6)

DCGL 2.39 pCi/g Cs-137 References 4 and 7 Design DCGL_________1__ pCifg Co-60 290.86 1_surveynit,_per ____Sectio Cs-1 37DCGL 3.59p~i/ x Area Factor for Class Design DCGLEMC 1.2 p~/ Co6I survey unit, per LTT Section 1.29 o-605.6.3

~i~g C. SURVEY RESULTS A total of 40 direct measurements were performed in Survey Unit 1. The results are presented in Table 2. All direct measurements were below the DCGL.

ISOCS gamma scans were performed at 94 locations using an investigation level of 1.0 pCi/g Cs-137 and 0.36 pCi/g Co-60. The gamma scans were performed for a sufficient count time to achieve a Minimum Detectable Activity (MDA) of approximately 40% of the DCGL. All identified scan activity levels were below the investigation levels. Therefore, no investigations were required.

LTP Revision 3, Table 5-1 C for RCA Yard West, R0100.

FR-O100-01, Revision 0 Page 3 of 19

TABLE 2 DIRECT MEASUREMENTS Sample Number Cs-137(pCi/g) Uncertainty (pCi/g)

FRO10001lSO001 <3.93E-02 FRO 1000 11S002 <3.65E-02 FROI 00011S003 <5.21E-02 FR0100011S004 <4.41E-02 FRO]0001 S005 <4.77E-02 _

FRO I00011S006 <4.83E-02 FRO 100011S007 <4.49E-02 FRO 100011S008 7.18E-02 2.99E-02 FROI0001 1S009 <4.94E-02 FRO100011SO10 1.98E-01 3.19E-02 FRO100011ISOI <5.26E-02 FROIO001ISO12 1.68E-01 3.28E-02 FROlOI001ISO3 <4.38E-02 FROI0001SOIS4 <3.78E-02 FROI00011SOI5 <4.41E-02 FROI000IISO16 <4.23E-02 FRO1000IISO17 <4.41E-02 FROI000IISO18 <6.13E-02 FRO100011S019 <5.20E-02 FROIOOO11S020 <4.55E-02 FROI000I IS021 <4.55E-02 FRO100011S022 <4.17E-02 FROIOO0IISO23 <3.55E-02 FROIOO011S024 <4.01E-02 FROIOO0IIS025 <4.28E-02 FRO100011S026 <3.77E-02 FRO100011SO27 4.59E-01 5.94E-02 FROIOOOIIS028 6.27E-02 2.44E-02 FRO 1000 11S029 7.69E-02 2.85E-02 FROIOO01IS030 <5.03E-02 FROIO0OISO31 <4.15E-02 FRO100011S032 <6.96E-02 _

FRO10001!S033 <5.88E-02 FRO100011S034 <5.90E-02 FR010001IS035 1.01E-O1 3.24E-02 FRO10001 1S036 3.52E-01 5.051E-02 FRO10001ISS037 <5.80E-02 FRO100011S038 <5.55E-02 FRO10001IS039 <4.44E-02 FRO10001IS040 4.29E-O1 5.43E-02 Mean 8.46E-02 Median 4.89E-02 Standard Deviation 1.O1E-OI Range 3.55E-02 to 4.59E-O1

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

Samples were also analyzed for Co-60. All were less than MDA.

FR-0100-0, Revision 0 Page 4 of 19

D. SURVEY UNIT INVESTIGATIONS PERFORMED AND 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. Of the 40 soil samples collected, 9 identified Cs-137 activity below the DCGL value of 2.39 pCi/g. All other values were below the MDA. Identified sample activities or Minimum Detectable Activities are listed in Table 2. The mean and median activities were less than the DCGL for Cs-137. The maximum reported value was less than 20% of the DCGL.

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-I 37 value (0.19 pCi/g) 2 for disturbed soil from the survey unit sample mean activity (0.0846 pCi/g). This would equate to an annual dose rate of 0.0 mrem/year.

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 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. 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 well below the DCGL of 2.39 pCi/g for Cs-1 37 for land inside the restricted area.

2 See Attachment E to Maine Yankee Procedure PMP 6.7.8 (Reference 5).

FR-O100-OI, Revision 0 Page 5 of 19

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

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.

1H. LTP CHANGES SUBSEQUENT TO SURVEY UNIT FSS The FSS of Survey Unit I was designed, performed, and evaluated in the December 2004 and January 2005 time frame. The design was performed to the criteria of the LTP Revision 3 (References 2 and 4). LTP Change No.05-001 (Reference 7) modified the Table 6-11 "Contaminated Material DCGL" to reflect an increased Deep Soil DCGL of 0.86 pCi/g for Co-60. This change resulted in an increased dose rate of 2.04 mrem/y from RA contaminated soils at depths greater than 15 cm. The LTP change directly impacted the retrospective dose calculation portion of release records dealing with Restricted Area excavations that were necessitated by radiological remediation.

FR-0100-01 consists of surface soils that cover the excavations previously surveyed under FR-0 11 Survey Units 4, 5, 6, and 7. The Deep Soil dose for underlying soils was accounted for in the release records of the FR-01 I I packages. As a result, the retrospective dose determination for FR-0100 Survey Unit I was based only on the contribution from surface soils within the top 15 cm. No subsequent LTP changes with potential impact to this survey unit need to be evaluated.

1. CONCLUSION The FSS of this survey unit was designed based on the LTP designation as a Class 1 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 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.

FR-O100-01, Revision 0 Page 6 of 19

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 several outliers.

The scan survey design for this survey unit was developed in accordance with the LTP Revision 3 Addenda (Reference I) with significant aspects of the design discussed in Section B and Table 1. ISOCS scans performed at a distance of 3 meters in a systematic grid pattern throughout the survey unit did not identify activity above the scan investigation levels of 1.0 pCi/g Cs-137 and 0.36 pCi/g Co-60.

It is concluded that FR 0100 Survey Unit I meets the release criteria of IOCFR20.1402 and the State of Maine enhanced criteria.

J. 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

6. Maine Yankee Calculation No. EC-003-04 (MY), Use of In Situ Object Counting System (ISOCS) for FSS Surveys

7. Maine Yankee LTP Change No.05-001, Deep Soil Co-60 DCGL FR-0 100-01, Revision 0 Page 7 of 19

Attachment 1 Survey Unit Maps FR-OI00-OI, Revision 0 Page 8 of 19

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FR-0100-01, Revision 0 Page 9 of 19

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Attachment 2 Survey Unit Instrumentation FR-0100-01, Revision 0 Page 12 of 19

TABLE 2-1 INSTRUMENT INFORMATION ISOCS Dctectors (Field Measurements)

Detector No. MDC (pCi/g) 7722 0. 14 to 0.75 7607 0.14 to 0.75 HPGe Detectors (Laboratory Analysis)

Detector No. MDC (pCi/g)

FSS1 0.03 to 0.075 FSS2 0.03 to 0.075 TABLE 2-2 INSTRUMENT SCAN MDC, DCGL, INVESTIGATION LEVEL AND DCGLEMIc Parameter Instrument: ISOCS Comments Scan MDC 0.14 to 0.75 pCi/g -40% DCGL 2.39 pCifg Cs-137 Approved DCGL for land DCGL 0.86 pCi/g Co-60 areas inside the Restricted Area, (References 4 and 7)

Investigation Level 1.0 pCi/g Cs-137 (ISOCS @ 3 m) 0.36 pCi/g Co-60 (Reference 6)

De3.59 pCi/g Co-60 DCGL x Area Factor for Design DCGLEMC 3.59 pCilg Cs-630 Class I survey unit, per 1.29 ~ilg o-60 LTP Section 5.6.3 NOTE: ISOCS scan MDCs were adjusted based on a thin layer of snow within the survey unit.

As a conservative measure, a snow layer equivalent to 4 inches of water (worst case) was added to the ISOCS configuration to determine the resulting instrument MDCs.

The ISOCS MDCs in Tables 2-1 and 2-2 reflect the conservative adjustment.

FR-0100-01, Revision 0 Page 13 of 19

Attachment 3 Investigation Table (No Investigations Performed)

FR-0100-01, Revision 0 Page 14 of 19

Attachment 4 Statistical Data FR-0100-01, Revision 0 Page 15 of 19

Survey Package FR 0100 Unit I Soil Sign Test Summary Survey Package: FR 0100 RCA Yard West Survey Unit: 01 Evaluator: DA DCGLW: 2.39E+00 Cs-1 37 DCGL DCGL.,: 3.59E+00 AF x DCGL LBGR: 1.20E+00 50% of DCGL Sigma: 1.33E+00 LTP Rev 3, Table 5-1 C for RCA Yd. W Type I error: 0.05 Type II error: 0.05 Nuclide: CS-1 37 Soil Type: N/A

§, %9-,^ s Calculaed VaIuis; * §4*

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Z: 1 1.645

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: . - ' 4.89E-02 Mean: .' , 8.$46E-02 Net Sample Standard Deviation: .1101E-01 1'

Total Standard Deviation: :' '-. 1.01 E-01 Maximum: .'4 s9E- _Oi_ _ __

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Adjusted N Value: .. . . 40 S+ Value: !40

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Critical Value: -5 ;, .'25 Sign test results: , . *': Pass U.g l.j~i4t'4.--.efl,'.SatIs'.obn eI.mmtA.s Sufficient samples collected: Pass Maximum value <DCGLW . e Pass Median value <DCGLw: * -* Pass Mean value <DCGL, ' .: Pass Maximum value <DCGLe- . -- Pass Total Standard Deviation <=Sigma: .'.:.. ,..: Pass Criteria comparison results: , Pass t.omjen The survey unit passes all conditions: Pass Survey Unit Passes FR 0100SU1-SoitSign.xis 214105 11:47AM FR-0100-01, Revision 0 Page 16 of 19

FR-0100 SU-1 Quantile Plot 5.OOE-01 4.50E-01 4.OOE-01 3.50E-01 C-) 3.00E-01

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One-Sample T-Test Report Page/Date/Time 2 2/2/05 5:17:02 AM Database C:\Program Files\NCSS97\FR0100 SU-1.S0 Variable C2 Plots Section Histogram of FR-01 00, SU-1 50-In n) 38 E

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0 13 0.000 0.125 0.250 0.376 0.500 Activity (pCIg)

FR-0100-01, Revision 0 Page 18 of 19

One-Sample T-Test Power Analysis Page/Date/Time 2 2/2105 5:20:33 AM Chart Section Retrospective Power Curve 1 .0. 4-0.8 - - - . _

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FR-0100-01, Revision 0 Page 19 of 19