ML043640286

Maine Yankee Final Status Survey Release Record FR-0400 Forebay Survey Unit 3

ML043640286
Person / Time
Site:	Maine Yankee
Issue date:	12/19/2004
From:	Cooper W J, Pillsbury G, Randall D B, Tozzie N Maine Yankee Atomic Power Co
To:	NRC/FSME
References
MN-04-060, RA-04-118 FR-0400-03, Rev 0
Download: ML043640286 (24)

Text

MAINE YANKEE FINAL STATUS SURVEY RELEASE RECORD FR-0400 FOREBAY SURVEY UNIT 3-s Date: Prepared By: a 9e"L ________FSS Engineer -Signature 12ccle Afl e Mld.Printed Name Date: Reviewed By: a7wg. Dntc'SSpe st-gature Printed Name Date: Reviewed By: _ __ 261 6 q dependent Reviewer -Signature Printe NDate-Approved By: _ ,. /zzco Sip tednS' S~ture n6nted Name /Date: Approved By: _¢r /,z SS, M1OP -Signature Printed Name MAINE YANKEE FINAL STATUS SURVEY RELEASE RECORD FR-0400 FOREBAY SURVEY UNIT 3 A. SURVEY UNIT DESCRIPTION Survey Unit 3 is located within Survey Area FR-0400, the Forebay. The Forebay is located south of the radiologically Restricted Area of the site at coordinates 407250 N and 623700 E (See Map FR0400-SITE, Attachment 1). The Forebay is a large, rock-lined basin in which condenser cooling water collected prior to its release through the diffuser system out to the ocean. During plant operation, the Forebay/Diffuser System was the licensed discharge path for liquid, radiological effluents.

After plant shutdown, stop logs were set in place at the Forebay end of the diffuser to isolate the Forebay in order to prevent the release of Forebay sediment into the river during remediation activities.

Two earthen dikes make up the north-south running walls of the Forebay with concrete walls at the extreme north and south ends to support the circulating water and diffuser pipes. The dike walls form a V at the southern end of the Forebay (adjacent to Foxbird Island). The diffuser discharge pipes originate at the notch of the V. A concrete dam, or weir, runs in the east west direction at the northern end of the Forebay and creates a small, water-filled area called the sealpit. The sealpit maintained a water seal over the circulating water pipes to prevent loss of flow with tidal fluctuations.

Survey Unit 3 consists of the concrete on the Sealpit (North) side of the weir and Circ Water Discharge Structure up to the 4'6" elevation.

The Survey Unit has a surface area of approximately 1 00 m 2.B. SURVEY UNIT DESIGN INFORMATION The Forebay received the liquid radioactive discharges from the plant. It was known to have been contaminated to levels in excess of the release limits and extensive remediation activities including underwater dredging, underwater vacuuming, and dry surface vacuuming were performed.

It should be noted that concrete surfaces were not remediated prior to the final status survey. Given the high probability of residual contamination, the Forebay was classified as Class 1.Revision 3 of the Maine Yankee License Termination Plan (LTP) states that the Forebay dose from residual radioactivity "is so insignificant and the probability so low that an individual would be able to successfully place a viable well within the Forebay, survey measurements of the Forebay surfaces including rip-rap will be limited." As a result, the survey design for the Forebay is a reasonable approach to demonstrate compliance with the release criteria while not necessarily meeting all of the requirements for a "MARSSIM" survey.FR-0400-03, Revision 0 Page 2 of 24 The survey unit design parameters are shown in Table 1. A minimum number of 14 direct samples were required for the Sign Test. Each sample measurement location was determined using a random start point and a square grid. These locations are presented on survey maps FRO400-09 and FRO400-1 0 (Attachment 1). Once the direct readings were completed, removable contamination samples were obtained at each direct measurement location.The survey unit design included 108 individual scan grids of approximately I m 2 (7 of the 108 scan grids wvere deemed inaccessible due to safety concerns for large overhanging boulders).

Refer to maps FRO400-07, 07a, and 08 in Attachment I for scan grid locations.

Instrument scan setpoints were conservatively set below the DCGLENIC, as shown in Table 2-2 (Attachment 2). Ninety-degree surface junctures were scanned using the 43-68 probe with a reduced efficiency.

Background values were established, for each particular instrument probe application based on ambient background values in the survey area and previously established material backgrounds.

These background values, listed in Table 1, were used to establish net activity for direct measurements, scan alarm setpoints, and to confirm the scan MDCs used were appropriate.

The instruments used in this survey 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 at the alarm setpoint was always less than the design DCGLEU1C, no EMC sample size adjustment was necessary.

FR-0400-03; Revision 0 Page 3 of 24 TABLE I SURVEY UNIT DESIGN PARAMETERS Survey Unit Design Critcria Basis Area 99.1 ml Based on an LBGR of 9,000 b dpm/1 00 cm 2 , a sigmal of 220 Measurements Required 14 dpm/1 00 cm 2 , and a relative shift (adjusted) of 3.0.Type I = Type II = 0.05 Sample Area 7.08 nL 99.1 / 14 samples Sample Grid Spacing 2.7 m (7.08)"2 Area Factor 7.0 50 m7 / 7.08 m' (Reference 4)Scan Survey Area -92 m" 100% accessible areas Background

^ 68 Direct and Scan 2 A a M (flat surfaces) 3,217 dpm/1 cm C Ambient and Material 43-68 (Junctures) 6,522 dpm/1 00 cmZ Ambient and Material Scan Investigation Level Background

+ DCGL See Table 2-2 (Attachment 2)DCGL 18,000 dpm/l 00 cm t Forebay technical basis document Design DCGLENIC 126,000 dpm/l 00 cm' Area Factor x DCGL C. SURVEY RESULTS Fourteen direct measurements were made in Survey Unit 3. The direct measurement data are presented in Table 2 below. All direct measurements were below the DCGL.The scan process was performed in accordance with FSS requirements for all accessible areas. The scan surveys identified no locations with verified alarms that would indicate potentially elevated activity; therefore no investigations were required.I Sigma was determined during the background evaluation performed for Survey Unit 3.FR-0400-03, Revision 0 Page 4 of 24 TABLE 2 DIRECT MEASUREMENTS Gross Activ. Net Activity Sample Number cm) (Table I Background Subtracted)(dpm/100 cm(dpm/100 CM 2)FRO400-3-COOI 3,083 -134 FR0400-3-C002 3,217 0 FRO400-3-C003 2,851 -366 FRO400-3-C004 3,168 -49 FRO400-3-C005 3,120 -98 FRO400-3-C006 3,510 293 FRO400-3-C007 3,480 263 FRO400-3-C008 3,474 256 FRO400-3-C009 3,272 55 FRO400-3-COIO 3,321 104 FRO400-3-COI 1 2,949 -269 FRO400-3-C012 3,205 -12 FRO400-3-C013 3,455 238 FRO400-3-C014 3,565 348 Mean 3,263 45 Median 3,245 27 Standard Deviation 218 218 Range 2,851 -3,565 -366 -348 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, are provided in Table 2. Without subtracting background, all sample measurement results were less than the DCGL. The mean value of background subtracted results are at 0.25% of the DCGL limit. The maximum direct sample result was equivalent to 2.0% of the DCGL. The background subtracted survey unit sample mean is a net value of 45 dpm/l 00 cm 2.This would be equivalent to an annual dose rate of 0.0008 mrem/y.2 The sample standard deviation is larger than the design sigma, however, no additional measurements were required due to the power of the Sign Test (i.e., relative shift unaffected).

2 Based on LTP Table 6-13 (Rev. 3). Residual contamination at the level of the DCGL for a contaminated basement is equivalent to an annual dose of 0.301 mrem/y.FR-0400-03, Revision 0 Page 5 of 24 The scan measurements, which were performed on 100% of accessible areas and produced no scan alarms. Grids # C025, C026, C027, C028, C048, C049 and C050 were not scan surveyed as they were deemed inaccessible due to a safety concern of injury from falling rock. However, since no remediation was performed on any concrete surfaces prior to the final survey, the results of the scan surveys on accessible areas are judged to be indicative of the radiological conditions for the unsurveyed grids. Some scan backgrounds were below the established background range. The survey data was evaluated with reduced investigation levels based on the low background measurements.

It was concluded that no additional alarms would have occurred.

In addition, since the instruments were shown to be performing properly with pre and post source checks, it is concluded that the low backgrounds do not affect the survey results or conclusion.

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.I .The Sign Test Summary provides an overall summary of design input (Table I) 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, except for the final sigma, were clearly satisfied for the FSS of this survey unit. Although the design sigma was less than the final sigma, the relative shift wvas unaffected and the number of samples remained adequate for the Sign Test.2. The Quantile Plot was generated from direct measurement 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 18,000 dpm/I 00 cm2 3. A Histogram Plot was also developed based on the direct measurement values. This plot shows that the direct data were essentially a normal distribution with no 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 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.As mentioned in Section B, removable contamination samples were obtained at each (direct)measurement location.

In that this survey unit did not involve a standing building, the removable contamination measurements were not applicable to release decisions for the survey unit. However, the samples were obtained and evaluated, indicating alpha and beta activity less than the MDA values of 4.3 and 4.6 dprn/l 00 cm 2 respectively.

Thus, in comparison with the mean survey unit net activity (Table 2), the removable contamination sampling effort indicated that the majority of activity is fixed.FR-0400-03, Revision 0 Page 6 of 24 G. CHANGES IN INITIAL SURVEY UNIT ASSUMPTIONS ON THE EXTENT OF RESIDUAL ACTIVITY The survey was designed as a Class I area. The FSS results were consistent with that classification.

As discussed previously, the final standard deviation was greater than the design sigma. However, the survey design was not adversely affected.

Thus, a sufficient number of samples were taken.HI. LTP CHANGES SUBSEQUENT TO SURVEY UNIT FSS The FSS of Survey Unit 3 was designed and performed using the criteria of the approved Forebay Technical Basis Document (Reference

4) and LTP (Revision 3 Addenda).Subsequent LTP changes have been evaluated and have no impact on the design, conduct, or assessment of the final status survey of this Survey Unit.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 18,000 dpm/l00 cm<.A Sign Test Summary analysis demonstrated that the Sign Test criteria were satisfied.

The sample standard deviation is larger than the design sigma, however, no additional measurements were required due to power of sign test.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 normal distribution, with variance consistent with expectations for a Class I survey unit.The scan survey design for this survey unit was developed in accordance with the LTP with significant aspects of the design discussed in Section B and Table 1. Scanning resulted in no verified alarms, therefore no investigations were required.In addition, while not part of the release decision criteria, removable contamination sampling confirmed that the majority of remaining activity in this survey unit was fixed It is concluded that FRO400 Survey Unit 3 meets the release criteria of IOCFR20.1402 and the State of Maine enhanced criteria.FR-0400-03, Revision 0 Page 7 of 24 J. REFERENCES

1. Maine Yankee License Termination Plan, Revision 3, October 15, 2002 2. Maine Yankee letter to the NRC, MN-02-061, dated November 26, 2002 3. NRC letter to Maine Yankee, dated February 28, 2003 4. Maine Yankee letter to the NRC, MN-03-05 1, "Forebay Technical Basis Document," dated September 3, 2003 FR-0400-03, Revision 0 Page 8 of 24 Attachment 1 Survey Unit Maps FR-0400-03, Revision 0 Page 9 of 24 Maine YankeeMan akeDeonssoinPrjcSuv rll apI Decommissioning Team Maine Yankee Decommissioning Project Survey Form Map ID #: FR 0400-SITE Survey Type: O Remediation 0 Turnover

• Final Status Survey I Survey Area Name: Forebay Seal Pit Site Map SURVEY AREA (PARTIAL), FR 0400__ -623,000 E FOXBIRD ISLAND 624,500 E 625,000 E Cn a CA a C 0 0) C-J 0) C) a o o 0 0 0 o Z z z z z z SCALE 0 400 800 1200 Note: Grid based on Maine State Coordinate System (West Zone) NAD 1927 MN 1--- E3D~ N FR-0400-03, Revision 0 Page 10 of 24 DcMm oin g Tnea Maine Yanikee Deconnmissiotting Project Survey Fort Map ID #: FRO400-07 Survey Type: O Characterization O Turnover

• Final Status Survey Survey Area Name: ForeBay Seal Pit FR 0400: FOREBAY, SEAL PIT Survey Unit 3, CW Discharge Surface Beta Scans Grids # C015 -C050 Surface Area is approximately 33.1 sq-m FIR 0400: FOREBAY, SEAL PIT Survey Unit 3, CW Discharge 35.0' [10.68m]Looking North Looking North 0___ __ __ I CONST. JOINT EL. 6'-9" EL. 4'-6"-r-r-I_I C039 0040 0041 C042 C.0 43 C044 I Q,045 IC046 C047 1444 CONST. JOINT EL. -1 0"_ _ _ __ _ __ ._ .__ _ _ _f,, C037 C036 C035 C034 033 C032- C031 C030 C029 &4q C015 C016 C017 C018 C019 C020 Q021 622 0023 024 Inaccessible grids due to safety stand-off Scan Grids are approximately 1m X 1m FR-0400-03, Revision 0 Page II of 24 Mming Ta m Maine Yankee Decommissioning Project Survey Forml Map ID #: FRO400-07a Decommissioning Teamll Survey Type: 0 Characterization 0 Turnover U Final Status Survey ISurvey Area Name: ForeBay Seal Pit FR 0400: FOREBAY, SEAL PIT Survey Unit 3, CW Discharge Surface Beta Juncture Scan # C122 Surface Area is approximately 33.1 sq-m FR 0400: FOREBAY, SEAL PIT FIR 0400: FOREBAY, SEAL PIT Survey Unit 3, CW Discharge 35.0' [10.68m]/0-__ TT .-C122- -CONST. JOINT EL. 6'-9" EL. 4'-6"[I CONST. JOINT EL. -'-O" Looking North FR-0400-03, Revision 0 Page 12 of 24 lecm ine Yaneeam laine Yankee Decomntmissioning Project Survey Form Map ID #: FR040D-O8 Decommissioning TeamII Survey Type: 0 Characterization l Turnover

• Final Status Survey Survey Area Name: ForeBay Seal Pit FR 0400: FOREBAY, SEAL PIT Survey Unit 3, Concrete Weir Surface Beta Scans Grids # C051 -C121 Surface Area is approximately 66 sq-m FR 0400: FOREBAY, SEAL PIT Survey Unit 3, Concrete Weir Looking South, East End Cr11A1I I -V%MIA1 QJ1 C12 C107 1n08 2109 1c 10 111 2112 1ill r117 4- -.--- + -i C106 0C085 C103 r2099 COPS COP 096,/21 05 C104 C102 21 01 2100 C097 C087-2086 L o ok i n S o u t h W e s t E Looking South, West End FR-0400-03, Revision 0 Page 13 of 24 I Maine YankeI ., -, loneomsinn em l ~lt }akeDcmtsinn rjc S rv~ or Map ID #: FIR 0400 REF Seal Pit FSS Surve Unit Reference

1. 1 -3 BAILEY COVE -as 5r/M/~------ --- --IsI S- /V\ /---10---- ----- ------------------------------__---.- ---J zzZz Z2 -.- --.- -. N.-----LEGEND:~- -tIx Or aRAVM m OME OF FRIP RA BOTI'M OF BAby Co>c CMMOEIE* OB I SURVEY UNIT 1 -FLAT SEDIMENT SURVEY UNIT 2. LEDGE SLOPE(S, SURVEY UNIT 3 -CONCRETE FOREBAY SEAL PIT/-I-GRAPHIC SCALE: 9 10 0 0 4 FR-0400-0 3 , Revision 0-Page 14 of 24 D Mmisioneang Alaine Yarnkee Decommissioning Project Survey Forum Map ID #: FRO400-09 Decommissioning Team I I Survey Type: O Characterization 0 Turnover

• Final Status Survey ISurvey Area Name: ForeBay Seal Pit FR 0400: FOREBAY, SEAL PIT Survey Unit 3, CW Discharge Surface Beta Directs -Pts. # C001 -C004 Surface Area is approximately 33.1 sq-m FR 0400: FOREBAY, SEAL PIT Survey Unit 3, CW Discharge i 10.67n I EL 4'-6" -2.21m CONST. JOINT EL. 0" 0-1 3.20m I Looking North FR-0400-03, Revision 0 Page 15 of 24 Maine YankeeI Decommissioning Team MAainte Yankee Decomnmissionting Project Survey Formi Map ID #: FRO400-10 Survey Type: E Characterization O Turnover U Final Status Survey I Survey Area Name: ForeBay Seal Pit FR 0400: FOREBAY, SEAL PIT Survey Unit 3, Concrete Weir Surface Beta Direct Pts. # C005 -C014 Surface Area is approximately 66 sq-m FR 0400: FOREBAY, SEAL PIT Survey Unit 3, Concrete Weir 0.87m ,C005 40C006 _LC07 -CO08 goo9 Cer.7,2.6) (6.4, 2.6) "(9.1, 2.6) TJ 1.8, 2.6;nte Line I I I Looking South, East End I 0 I Looking South, West End Attachment 2 Survey Unit Instrumentation FR-0400-03, Revision 0 Page 17 of 24 TABLE 2-1 INSTRUMENT INFORMATION E-600 S/N I Probe SIN (type) ]2489 148934 (43-68)1933 148938 (43-68)2490 148934 (43-68)2490 177992 (43-68)2491 149073 (43-68)2618 149073 (43-68)TABLE 2-2 INSTRUMENT SCAN MDC, DCGL, INVESTIGATION LEVEL, AND DESIGN DCGLEMC 1eecor43-68 j43-68 Detector I Flat Junctures Scan MDC 1,832 4,330 (dpmJ1I00 cm 2) (LTP Rev. 3) (Note 1)DCGL (dpm/100 cm 2) 18,000 18,000 Investigation Level 21,215 24,385 (dpmAl 00 cm2e ) (- DCGL plus background)

(- DCGL plus background)

Design DCGLEmC 126,000 126,000 (dpM /IO O CM 2)__ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _NOTE: 1. The 43-68 scan MDC from LTP, Revision 3 was adjusted to account for a reduced efficiency due to the juncture geometry.FR-0400-03, Revision 0 Page 18 of 24 Attachment 3 Investigation Table (No Investigations Required)FR-0400-03, Revision 0 Page 19 of 24 Attachment 4 Statistical Data FR-0400-03, Revision 0 Page 20 of 24 Survey Package FR-0400 Unit 3 Surface Sign Test Summary Evaluatioi In iut VaIL ;- -, ; '> R rm ts ' .Survey Package: FR-0400 Forebay Concrete Survey Unit: 03 Evaluator:

GP DCGL,: 18,000 DCGL,,.,:

126,000 LBGR: 9,000 Sigma: 220 Type I error: 0.05 Type II error: 0.05 Total Instrument Efficiency:

13.0%Detector Area (cm 2): 126 Concrete Choosing 'N/A' sets material Material Type: Unpainted background to "0" Z1,,:1.645 ZIP: 1.645 Sign p: 0.99865 Calculated Relative Shift: 40.9 Relative Shift Used: 3.0 Uses 3.0 if Relative Shift >3 N-Value: 11 N-Value+20%:

14 Ia 6~ rJ_ omments,.1:, ._,,,,:'/t,'.'-t'?pt-Static Data ValuesY W<,i:?---;iD°omn.<

Number of Samples: 14 Median: 28 Mean: 46 Net Static Data Standard Deviation:

218 Total Standard Deviation:

281 SRSS Maximum: 349.jJ; ;Sign Test Resulntnts-Y 1,'-" aft -.' Comments, , Adjusted N Value: 14 S+ Value: 14 .-Critical Value: 10 Sufficient samples collected:

Pass Maximum value <DCGL,: Pass Median value <DCGL,,: Pass Mean value <DCGLs,: Pass Maximum value <DCGL,.: Pass Total Standard Deviation

<=Sigma: Investigate Total sigma exceeds design sigma Sign test results: .Pass but the survey has adequate power The survey unit passes all conditions:

Investigate SU-3 Passes FR.0400-SU3-SurfaceSign 11/30/04 11:04AM FR-0400-03, Revision 0 Page 21 of 24 FR-0400 SU-3 Quantile Plot A c C C t -co E 0 I-a)65.W._400 300 200 100 0-100-200-300-400-500 , ,-_____-----.----.

--.--- --".-.-p

• I* Activity (dpm/1 00 cm2)-Median (dpm/100 cm2)0 25 50 Percent 75 100 One-Sample T-Test Report Page/Date/Time Database Variable 2 10/5/04 3:07:24 PM C2 Plots Section Histogram of FR-0400, SU-3 Ch 0 C,.0 E z FR-0400-03, Revision 0 Page 23 of 24 One-Sample T-Test Power Analysis Page/Date/Time 2 10/5/04 3:08:35 PM Chart Section a)0 a-Retrospective Power Curve.* I I I x, .I e l\ I I*l \ I* I I ,I I I \I I I \ I I I I \ I I£ I \ I I* I l\ I I I I I* I I I l I I I Survey Unit Mean (dpml1 00 cm2)FR-0400-03, Revision 0 Page 24 of 24