ML19007A032

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5299-SR-03 - LACBWR Confirmatory Survey Report
ML19007A032
Person / Time
Site: La Crosse File:Dairyland Power Cooperative icon.png
Issue date: 06/20/2018
From: Altic N, Pitman S
Oak Ridge Institute for Science & Education
To: Vaaler M
Reactor Decommissioning Branch
M WONG DUWP
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5299-SR-03
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INDEPENDENT CONFIRMATORY SURVEY

SUMMARY

AND RESULTS FOR THE CIRCULATING WATER DISCHARGE INTERIOR PIPING AT THE LA CROSSE BOILING WATER REACTOR, GENOA, WISCONSIN N. A. Altic, CHP and S. T. Pittman, PhD ORISE FINAL REPORT Prepared for the U.S. Nuclear Regulatory Commission June 2018 Further dissemination authorized to NRC only; other requests shall be approved by the originating facility or higher NRC programmatic authority

ORAU provides innovative scientific and technical solutions to advance research and education, protect public health and the environment and strengthen national security. Through specialized teams of experts, unique laboratory capabilities and access to a consortium of more than 100 major Ph.D.-granting institutions, ORAU works with federal, state, local and commercial customers to advance national priorities and serve the public interest. A 501(c) (3) nonprofit corporation and federal contractor, ORAU manages the Oak Ridge Institute for Science and Education (ORISE) for the U.S. Department of Energy (DOE). Learn more about ORAU at www.orau.org.

NOTICES The opinions expressed herein do not necessarily reflect the opinions of the sponsoring institutions of Oak Ridge Associated Universities.

This report was prepared as an account of work sponsored by the United States Government.

Neither the United States Government nor the U.S. Department of Energy, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe on privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, mark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement or recommendation, or favor by the U.S. Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof.

INDEPENDENT CONFIRMATORY SURVEY

SUMMARY

AND RESULTS FOR THE CIRCULATING WATER DISCHARGE INTERIOR PIPING AT THE LA CROSSE BOILING WATER REACTOR, GENOA, WISCONSIN Prepared by N. A. Altic, CHP and S. T. Pittman, PhD ORISE June 2018 FINAL REPORT Prepared for the U.S. Nuclear Regulatory Commission This document was prepared for U.S. Nuclear Regulatory Commission by the Oak Ridge Institute for Science and Education (ORISE) through an interagency agreement with the U.S. Department of Energy (DOE) (NRC FIN No. F-1244). ORISE is managed by Oak Ridge Associated Universities under DOE contract number DE-SC0014664.

La Crosse CWD Confirmatory Survey 5299-SR-03-0

CONTENTS FIGURES .......................................................................................................................................................... iii TABLES ............................................................................................................................................................. iii ACRONYMS .................................................................................................................................................... iv EXECUTIVE

SUMMARY

............................................................................................................................. vi

1. INTRODUCTION....................................................................................................................................... 1
2. SITE DESCRIPTION ................................................................................................................................. 2
3. DATA QUALITY OBJECTIVES ............................................................................................................. 4 3.1 State the Problem .............................................................................................................................. 4 3.2 Identify the Decision ........................................................................................................................ 5 3.3 Identify Inputs to the Decision ....................................................................................................... 5 3.4 Define the Study Boundaries ........................................................................................................... 7 3.5 Develop a Decision Rule.................................................................................................................. 7 3.6 Specify Limits on Decision Errors ................................................................................................. 8 3.7 Optimize the Design for Obtaining Data...................................................................................... 9
4. PROCEDURES ............................................................................................................................................ 9 4.1 Reference System .............................................................................................................................. 9 4.2 Surface Scans...................................................................................................................................... 9 4.3 Surface Activity Measurements .....................................................................................................10
5. SAMPLE ANALYSIS AND DATA INTERPRETATION ...............................................................10
6. FINDINGS AND RESULTS ...................................................................................................................11 6.1 Surface Scans....................................................................................................................................11 6.2 Surface Activity Measurements .....................................................................................................12
7. CONCLUSIONS ........................................................................................................................................14
8. REFERENCES ...........................................................................................................................................15 APPENDIX A ANALYTICAL RESULTS APPENDIX B MAJOR INSTRUMENTATION APPENDIX C SURVEY PROCEDURES La Crosse CWD Confirmatory Survey ii 5299-SR-03-0

FIGURES Figure 2.1. LACBWR Site Overview (LS 2016) ............................................................................................ 3 Figure 3.1. VSP Sample Size Determination.................................................................................................. 8 Figure 6.1. ORISE Scan Data for the CWD Pipe.......................................................................................12 Figure 6.2. Q-Q Plot of Surface Activity for the Top and Bottom Portion of the CWD Piping........13 TABLES Table 3.1. LACBWR CWD Piping Confirmatory Survey Decision Process ............................................ 5 Table 3.2. DCGLs for CWD Piping (dpm/100 cm2) .................................................................................. 6 Table 3.3. Gross Activity DCGLs (dpm/100 cm2) ....................................................................................... 7 Table 6.1. General Statistics for ORISE Surface Activity Measurements ...............................................12 La Crosse CWD Confirmatory Survey iii 5299-SR-03-0

ACRONYMS AA alternate action BWR boiling water reactor Co-60 cobalt-60 cpm counts per minute Cs-137 cesium-137 CWD Circulating Water Discharge DCGL derived concentration guideline level DCGLBC Base Case DCGL DCGLOps Operational DCGL DPC Dairyland Power Cooperative DQO data quality objective Eu-152 europium-152 Eu-154 europium-154 FESW fuel element storage well FRS final radiation survey FSS final status survey ISFSI Independent Spent Fuel Storage Installation LACBWR La Crosse Boiling Water Reactor LSE LACBWR site enclosure LTP license termination plan m meter MARSSIM Multi-Agency Radiation Survey and Site Investigation Manual MDC minimum detectable concentration mrem/yr millirem per year NaI sodium iodide NRC U.S. Nuclear Regulatory Commission ORAU Oak Ridge Associated Universities La Crosse CWD Confirmatory Survey iv 5299-SR-03-0

ORISE Oak Ridge Institute for Science and Education pCi/g picocuries per gram PSP project-specific plan PSQ principal study question Q quantile ROC radionuclide of concern STS source term survey SU survey unit VSP Visual Sample Plan La Crosse CWD Confirmatory Survey v 5299-SR-03-0

INDEPENDENT CONFIRMATORY

SUMMARY

AND RESULTS FOR THE CIRCULATING WATER DISCHARGE INTERIOR PIPING AT THE LA CROSSE BOILING WATER REACTOR, GENOA, WISCONSIN EXECUTIVE

SUMMARY

At the request of the U.S. Nuclear Regulatory Commission, the Oak Ridge Institute for Science and Education performed an independent confirmatory survey of the interior of the circulating water discharge (CWD) piping during the period of April 24-26, 2018, at the La Crosse Boiling Water Reactor. The confirmatory survey consisted of gamma scans and surface activity measurements for gamma and beta radiation to independently assess the final radiological status of the CWD piping interior relative to the release criterion. None of the collected surface activity measurementsbased on either gamma or beta radiationwere above the operational gross activity derived concentration guideline level (which corresponds to a dose of approximately 5.3 mrem/yr). Based on the confirmatory survey data, it is the opinion of ORISE that residual radiation levels in the CWD piping interior are less than the release criterion.

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INDEPENDENT CONFIRMATORY SURVEY RESULTS AND

SUMMARY

FOR THE CIRCULATING WATER DISCHARGE INTERIOR PIPING AT THE LA CROSSE BOILING WATER REACTOR, GENOA, WISCONSIN

1. INTRODUCTION The La Crosse Boiling Water Reactor (LACBWR), a 50-megawatt electric boiling water reactor (BWR) located in Genoa, Wisconsin, was originally a demonstration plant funded by the U.S. Atomic Energy Commission. The plant was later sold to Dairyland Power Cooperative (DPC) with a provisional operating license. The BWR achieved initial criticality on July 11, 1967 and operated for 19 years until being permanently shut down on April 30, 1987. After shutdown, DPCs authority to operate LACBWR under Provisional Operating License DPR-45 (issued by the U.S. Nuclear Regulatory Commission [NRC] on August 28, 1973) was amended via License Amendment 56 (August 4, 1987) to possession only authority (LS 2016).

Dismantling unused and offline systems and waste disposal operations began in 1994. The Reactor Pressure Vessel (head, internals, and 29 control rods sealed with concrete), stored waste in the Fuel Element Storage Well (FESW), and other Class B/C wastes were shipped offsite for disposal in June 2007. Other systems and componentssuch as spent fuel storage racks, gaseous waste disposal systems (excluding the underground gas storage tanks), condensate and feedwater system (excluding condensate storage tank and condenser), the turbine and generator, and various components located in the Turbine Building (cooling water system pumps, heat exchangers, piping, etc.)have also been removed. In September 2012, 333 irradiated fuel assemblies from the FESW were packaged in five dry casks and transferred to the sites Independent Spent Fuel Storage Installation (ISFSI) (LS 2016).

In May 2016, the NRC consented to having the possession, maintenance, and decommissioning authorities of the LACBWR site transferred from DPC to LaCrosseSolutions, LLC.

LACBWR has submitted a License Termination Plan (LTP) to the NRC requesting the removal of all remaining open-land and structures, except for the fenced area surrounding the ISFSI, from License DPR-45. The LACBWR Administration Building, Crib House, and Transmission Sub-Station Switch House will remain intact. All other LACBWR buildings and structures will be demolished and removed to a depth of three feet below gradecorresponding to the 636-foot La Crosse CWD Confirmatory Survey 1 5299-SR-03-0

elevationincluding the basements of the Reactor Building, Waste Treatment Building, Waste Gas Tank Vault, and other miscellaneous remaining basement structures.

The LTP requires a Final Radiation Survey (FRS) that will radiologically characterize the site and determine the potential for an average member of the critical group to receive a total effective dose equivalent greater than 25 millirem per year (mrem/yr). The FRS plan consists of two types of compliance surveys: a Final Status Survey (FSS) for open-land areas and buried piping based on NUREG-1575 (NRC 2000) and a Source Term Survey (STS) for the below-ground structures that will be backfilled prior to license termination.

NRC requested that the Oak Ridge Institute for Science and Education (ORISE) perform confirmatory survey activities to independently assess the final radiological condition of the Circulating Water Discharge (CWD) piping interior. This report summarizes the confirmatory survey activities associated with the CWD interior piping, at LACBWR.

2. SITE DESCRIPTION The LACBWR site is located approximately 1.6 kilometers (1 mile) south from the village of Genoa, Wisconsin on the eastern shore of the Mississippi River. The 10 CFR Part 50 licensed site is shared with the non-nuclear Genoa-3 Fossil Station and comprises a total of 66.2 hectares (164 acres). The operational fossil plants buildings and structures were classified as non-impacted and are not subject to the release surveys specified in the LTP (LS 2016). Figure 2.1 provides an aerial view of the licensed site, within which is located the 0.61-hectare LACBWR Site Enclosure (LSE) area, shaded red in the figure.

The CWD piping, designated as survey unit S1-011-102 CWD, is a 1.52-meter (m) diameter steel pipe with a length of approximately 128 m (420 feet). During reactor operations, it was the receiver of batch liquid discharges to the Mississippi River and is a Class 1 survey unit (LS 2018a). At the time of survey, pumps had largely removed river water from the pipe, with residual water and sediment remaining in limited areas.

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Figure 2.1. LACBWR Site Overview (LS 2016)

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3. DATA QUALITY OBJECTIVES The data quality objectives (DQOs) process was applied to the design of the confirmatory survey.

The DQOs applied, and described herein, were consistent with the Guidance on Systematic Planning Using the Data Quality Objectives Process (EPA 2006) and provided a formalized method for planning confirmatory radiation surveys, improving survey efficiency and effectiveness, and ensuring that the type, quality, and quantity of data collected were adequate for the intended decision applications.

The seven steps in the DQO process were as follows:

1. State the problem
2. Identify the decision/objective
3. Identify inputs to the decision/objective
4. Define the study boundaries
5. Develop a decision rule
6. Specify limits on decision errors
7. Optimize the design for obtaining data 3.1 STATE THE PROBLEM The first step in the DQO process defined the problem that necessitated the study, identified the planning team, and examined the project budget and schedule. LACBWR is in the process of dismantling remaining structures and remediating remaining lands. As part of this process, LACBWR is conducting an FSS to demonstrate compliance with the NRCs license termination criteria specified in 10CFR20.1402. To this end, the NRC requested that ORISE perform confirmatory surveys of the CWD piping interior to provide independent data for NRCs consideration in their evaluation of the FSS. Therefore, the problem statement was as follows:

Confirmatory surveys are necessary to generate independent radiological data for NRCs consideration in the evaluation of the FSS design, implementation, and results for demonstrating compliance with the release criteria.

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3.2 IDENTIFY THE DECISION The second step in the DQO process identified the principal study questions (PSQs) and alternate actions (AAs); developed decision statements; and organized multiple decisions, as appropriate. This was done by specifying AAs that could result from a yes response to the PSQs and combining the PSQs and AAs into decision statements. Given that the problem statement introduced in Section 3.1 was fairly broad, multiple PSQs arose and were detailed in the confirmatory survey project-specific plan (PSP) (ORISE 2017). The PSQ, AAs, and combined decision statement applicable to the survey efforts detailed in this report are presented in Table 3.1.

Table 3.1. LACBWR CWD Piping Confirmatory Survey Decision Process Principal Study Question Alternative Actions Yes:

Confirmatory results indicate that residual radioactivity levels are below allowable limits compile confirmatory survey data and present the results to the NRC for their decision making.

Are residual radioactivity levels in the CWD piping below the release criterion? No:

Confirmatory survey results indicate that residual radioactivity levels exceed allowable limits summarize unacceptable data points and provide technical comments and/or further evaluation(s) to the NRC for their decision making.

Decision Statement Determine if the residual radioactivity levels are below/above the allowable limits.

3.3 IDENTIFY INPUTS TO THE DECISION The third step in the DQO process identified both the information needed and the sources of this information; determined the basis for action levels; and identified sampling and analytical methods to meet data requirements. For this effort, information inputs included the following:

  • LWCBWR derived concentration guideline levels (DCGLs); discussed in Section 3.3.1 La Crosse CWD Confirmatory Survey 5 5299-SR-03-0
  • LACBWR Procedure No. LC-FS-PR-018, Radiation Surveys of Pipe Interiors Using Sodium/Cesium Iodide Detectors (LS 2018b)
  • ORISE confirmatory survey results including: surface radiation scans and direct surface activity measurements 3.3.1 Radionuclides of Concern The primary radionuclides of concern (ROCs) identified for LACBWR are beta-gamma emitters fission and activation productsresulting from reactor operation. The DCGLs for the CWD piping are presented in Table 3.2.

Table 3.2. DCGLs for CWD Piping (dpm/100 cm2)

ROC DCGLBC DCGLOps Co-60 7.75E+04 1.63E+04 Sr-90 7.56E+05 1.59E+05 Cs-137 3.30E+05 6.94E+04 Eu-152 1.67E+05 3.51E+04 Eu-154 1.56E+05 3.27E+04 dpm/100 cm 2 = disintegrations per minute per 100 square-centimeters DCGLBC = Base Case DCGL DCGLOps = Operational DCGL Source: LS 2018a In Table 3.2, the Base Case DCGL (DCGLBC) is the residual radioactivity levelwhen considered individuallythat results in a potential total effective dose equivalent of 25 mrem/yr (the release criterion) to a future receptor. To account for multiple source terms at the LACBWR site, the Base Case DCGLs are reduced to a fraction of the dose criterion; the reduced DCGL is termed the Operational DCGL (DCGLOps).

LACBWR has established gross gamma activity DCGLs using the surrogate approach to account for the pure beta emitter, Sr-90, and the expected activity fractions for other gamma-emitters. Gross activity DCGLs are presented in Table 3.3.

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Table 3.3. Gross Activity DCGLs (dpm/100 cm2)

Gross Activity Limit DCGLBC 2.28E+05 DCGLOps 4.80E+04 Source: LS 2018a 3.4 DEFINE THE STUDY BOUNDARIES The fourth step in the DQO process defined target populations and spatial boundaries; determined the timeframe for collecting data and making decisions; addressed practical constraints; and determined the smallest subpopulations, area, volume, and time for which separate decisions must be made.

Physical boundaries of the confirmatory survey were limited to the CWD interior piping survey unit, identified as S1-011-102 CWD by the licensee. Three full days were allotted for this survey, constituting the temporal boundary of the study.

3.5 DEVELOP A DECISION RULE The fifth step in the DQO process specified appropriate population parameters (e.g., mean, median); confirmed detection limits were below the action levels; and developed an ifthen decision rule statement.

The parameters of interest for this survey were individual surface activity measurements collected from the CWD piping survey unit. LACBWR established a measurement scheme where static gamma measurements were collected every linear foot of piping. Based on LACBWRs calibration and measurement methodology, each static surface activity measurement represented a total area of 3,315 cm2, with a width of 32.5 cm along the central axis of the pipe. Measurements were collected with the detector approximately 14 cm from the bottom of the pipe, as this represents the highest potential for contamination. The confirmatory survey was designed such that, provided a representative number of surface activity measurements from the CWD piping were below the action level, one could conclude that a high percentage of the piping was below the action level with a specified degree of confidence. In this instance the action level was the DCGLBC. Given the previous discussion, the decision rule was stated as follows:

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If confirmatory survey measurements were below the DCGLBC, then conclude that a high percentage of the CWD piping is below release limit; otherwise, perform further evaluation(s) and provide technical comments to the NRC.

3.6 SPECIFY LIMITS ON DECISION ERRORS The sixth step in the DQO process specified the decision makers limits on decision errors, which were then used to establish performance goals for the survey.

Decision errors were limited by establishing the confidence level for confirming that residual activity over a high percentage of the piping was less than the DCGLBC. For this study, a 95% confidence level was selected. Visual Sample Plan (VSP), version 7.9, was used to determine the number of measurements necessary to conclude that 95% of the survey unit was acceptable at the 95%

confidence level. Figure 3.1 depicts the VSP output. A total of 55 measurements were needed to achieve the desired confidence level.

Figure 3.1. VSP Sample Size Determination An additional level of control was to ensure that static measurement count times were such that the minimum detectable concentration (MDC) was less than the gross surface activity DCGLBC and that scan sensitivities were adequate for the identification of any localized, high activity hot spots.

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3.7 OPTIMIZE THE DESIGN FOR OBTAINING DATA The seventh step in the DQO process was used to review DQO outputs; develop data collection design alternatives; formulate mathematical expressions for each design; decide on the most resource-effective design of agreed alternatives; and document requisite details. The survey design was optimized by implementing the procedures outlined in Section 4.

4. PROCEDURES The ORISE survey team performed visual inspections, measurements, and sampling activities within the CWD piping survey unit S1-011-102 CWD. Survey activities were conducted in accordance with the ORAU Radiological and Environmental Survey Procedures Manual, the ORAU Environmental Services and Radiation Training Quality Program Manual, and the approved confirmatory survey PSP Addendum (ORAU 2016a, ORAU 2016b, and ORISE 2018).

4.1 REFERENCE SYSTEM ORISE referenced confirmatory measurement/sampling locations to the sites reference system, which was distance traveled from the south to north end of the CWD pipe.

4.2 SURFACE SCANS LACBWR designed a detector carrier for scanning the interior of the CWD piping. The carrier is a wheeled device designed to keep a 2 x 2-inch sodium iodide (NaI) detector in a fixed geometry.

ORISE used this device at the direction of NRC, along with an ORISE NaI detector, to perform surface scans of the bottom of the pipe interior. The NaI detectors used for interior piping scans were Ludlum Model 44-10 NaI scintillation detectors coupled to Ludlum Model 2221 ratemeter-scalers with audible indicators. High-density surface scans were performed on both the lower and upper portions of the entire length of the pipe per standard ORISE procedure (without the use of the carrier).

There were no locations of elevated direct gamma radiation identified. All ratemeter-scalers were attached to data-loggers to electronically capture the scan count rate data.

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4.3 SURFACE ACTIVITY MEASUREMENTS Surface activity measurement locations for the bottom of the pipe were laid out in a random start systematic fashion. As introduced in Section 3.6, the number of measurements required was 55; however, due to the systematic spacing, the number was adjusted to 60 to cover the entire length of the pipe. Gamma surface activity measurements were collected using a Ludlum Model 44-10 NaI detector coupled to a Ludlum Model 2221 ratemeter-scaler. Prior to survey, the efficiency was expected to be on the order of 2.3E-03 for a 15.24 cm detector offset, based on Monte Carlo modeling of the NaI detector and the estimated size of LACBWRs Cs-137 calibration standard. The choice of Cs-137 as a calibration standard is conservative because the instrument response from the other gamma-emitters is greater than that of Cs-137.

Efficiency factors for the NaI detector were validated by utilizing LACBWRs flexible large-area Cs-137 calibration standard once the survey team was onsite. The validated efficiency determined by using the sites calibration standard was 3.37E-03, which is slightly higher than the Monte Carlo-based estimated efficiency. All subsequent surface activity calculations were performed using the validated detector efficiency determined onsite. Appendix C.3.2 provides additional information related to the efficiency validation. The surface-activity MDC was 2,700 dpm/100 cm2, averaged over an area of 3,315 cm2.

In addition to the gamma measurements, beta surface activity measurements were also collected from the top and bottom of the CWD piping at a frequency of 25% to confirm the appropriateness of the gamma surrogate relationship to Sr-90. Beta measurements were collected using a Ludlum 44-142 beta scintillator detector connected to a Ludlum 2221 ratemeter-scaler. Additional gamma surface activity measurements were collected from the top of the piping at a frequency of 25%; at the same locations as the beta measurements.

5. SAMPLE ANALYSIS AND DATA INTERPRETATION All confirmatory survey data collected onsite were transferred to the ORISE facility in Oak Ridge, Tennessee for analysis and interpretation. Static surface activity measurements are reported in units of dpm/100 cm2. Surface activity calculations are discussed in greater detail in Appendix C.

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Gamma surface scan data for the top and bottom portion of the pipe were graphed in a quantile-quantile (Q-Q) plot for assessment. The Q-Q plot is a graphical tool for assessing the distribution of a data set. In viewing the Q-Q plots provided, the Y-axis represents gross gamma surface activity in units of cpm. The X-axis represents the data quantiles about the median value.

Values less than the median are represented in the negative quantiles, and the values greater than the median are represented in the positive quantiles. A normal distribution that is not skewed by outliersi.e., a background populationwill appear as a straight line, with the slope of the line subject to the degree of variability among the data population. More than one distribution, such as background plus contamination or other outliers, will appear as a step function.

6. FINDINGS AND RESULTS The results of the confirmatory survey activities are discussed in the subsections below.

6.1 SURFACE SCANS Overall, NaI detector scan responses ranged from approximately 2,600 to 5,100 cpm for the bottom of the pipe and 2,800 to 5,900 cpm for the top. Table A-2 in Appendix A provides summary statistics for the scan data. No anomalies were identified relative to the localized background. Higher NaI responses were encountered near the north end of the pipe, where the metal pipe had been removed for entryas would be expected due to an increase in cosmic background radiation. The Q-Q plot for the scan data is presented as Figure 6.1. NaI detector response for the top portion of the pipe was approximately 300 to 800 cpm higher relative to the bottom portion throughout the length of the pipe. However, the increase is not expected to be due to contamination as the detector response was fairly uniform.

La Crosse CWD Confirmatory Survey 11 5299-SR-03-0

Figure 6.1. ORISE Scan Data for the CWD Pipe 6.2 SURFACE ACTIVITY MEASUREMENTS General statistics for the ORISE surface activity measurements are provided in Table 6.1. Table A-1 provides individual surface activity measurements.

Table 6.1. General Statistics for ORISE Surface Activity Measurements Bottom (dpm/100 cm2) Top (dpm/100 cm2)

Parameter Beta Gamma Beta Gamma Mean 680 39 4,200 7,700 Median 780 0 4,100 6,700 Standard Deviation 460 3,100 2,100 5,700 Min -580 7,800 510 1,700 Max 1,300 17,000 8,600 20,000 The maximum observed gamma and beta surface activities on the bottom of the pipe were at 417 feet and 403 feet from the south end of the pipe, respectively. The maximum observed gamma and beta surface activities on the top of the pipe were at 95 feet from the south end of the pipe for both.

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Figure 6.2 provides the Q-Q plot for surface activity measurements collected from the CWD piping interior. The plot is segregated by the top and bottom portion of the pipe with the respective beta and gamma data set plotted on the same facet. As indicated by the Q-Q plot, all data sets appear normal, with perhaps the exception of the gamma surface activity data set for the bottomwhich appear to contain an outlier at 17,000 dpm/100 cm2. However, contamination is not expected as this potential outlier was collected from the north end of the pipe where the ambient background was observed to be higher. The mean surface activity for the top portion of the pipe is approximately 7,700 dpm/100 cm2, which is approximately 7,600 dpm/100 cm2 higher than the mean of the bottom surface activity measurements. The corresponding count rate differencein units of cpm is approximately 860 cpm, which compares favorably to the mean difference in the top/bottom scan data sets, indicating the top portion and bottom portion of the pipe have different backgrounds.

Due to the relatively small gamma efficiency, a small difference in count rates corresponds to a multiplicatively larger difference in surface activity. None of the beta or gamma surface activity measurements were above the operational gross activity DCGLOps. The beta surface activity measurements did not indicate the presence of Sr-90 at significant quantities relative to other gamma-emitting ROCs, however no hot spots were identified that would confirm this relationship.

Figure 6.2. Q-Q Plot of Surface Activity for the Top and Bottom Portion of the CWD Piping La Crosse CWD Confirmatory Survey 13 5299-SR-03-0

The beta surface activity data sets are both approximately normal as indicated by the shape of the Q-Q plot and the similarities of the mean and median. As with the gamma data set, the top portion of the pipe has a higher background than the bottom. Neither data set is centered around zero, as an ambient instrument background was subtracted instead of an SU-specific background, which is conservative.

7. CONCLUSIONS During the period of April 24 through 26, 2018, ORISE performed an independent confirmatory survey of the interior of the CWD piping at the La Crosse Boiling Water Reactor. The confirmatory survey consisted of gamma scans and surface activity measurements for gamma and beta radiation to independently assess the final radiological status of the CWD piping interior relative to the release criterion. None of the collected surface activity measurementsbased on either gamma or beta radiationwere above the DCGLOps. Based on the confirmatory survey data, it was concluded that at least 95% of the CWD piping interior is below the DCGLOps at the 95% confidence level.

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8. REFERENCES EPA 2006. Data Quality Assessment: Statistical Methods for Practitioners. EPA QA/G-9S.

U.S. Environmental Protection Agency. Washington, D.C. February.

LS 2016. La Crosse Boiling Water Reactor, License Termination Plan. LaCrosseSolutions. Genoa, Wisconsin.

June.

LS 2018a. Final Status Survey Package for Survey Unit S1-011-102 CDW. LaCrosseSolutions. Genoa, Wisconsin. April 9.

LS 2018b. Procedure No. LC-FS-PR-018, Revision No. 0, Radiation Surveys of Pipe Interiors Using Sodium/Cesium Iodide Detectors. LaCrosseSolutions. Genoa, Wisconsin. March 27.

NRC 2000. Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM). NUREG-1575.

Revision 1. U.S. Nuclear Regulatory Commission. Washington, D.C. August.

ORAU 2014. ORAU Radiation Protection Manual. Oak Ridge, Tennessee. October.

ORAU 2016a. ORAU Radiological and Environmental Survey Procedures Manual. Oak Ridge Associated Universities. Oak Ridge, Tennessee. November 10.

ORAU 2016b. ORAU Environmental Services and Radiation Training Quality Program Manual. Oak Ridge Associated Universities. Oak Ridge, Tennessee. November 9.

ORAU 2016c. ORAU Health and Safety Manual. Oak Ridge, Tennessee. January.

ORAU 2017. ORAU Radiological and Environmental Analytical Laboratory Procedures Manual. Oak Ridge Associated Universities. Oak Ridge, Tennessee. August 24.

ORISE 2017. Project-Specific Plan for the Confirmatory Survey Activities at the La Crosse Boiling Water Reactor, Genoa, Wisconsin. Oak Ridge Institute for Science and Education. Oak Ridge, Tennessee.

December 20.

ORISE 2018. Addendum to the Project-Specific Plan for the Confirmatory Survey Activities at the La Crosse Boiling Water Reactor, Genoa, Wisconsin (DCN 5299-PL-02-0). Oak Ridge Institute for Science and Education. Oak Ridge, Tennessee. April 24, 2018.

La Crosse CWD Confirmatory Survey 15 5299-SR-03-0

APPENDIX A ANALYTICAL RESULTS La Crosse CWD Confirmatory Survey 5299-SR-03-0

Table A-1. Individual Surface Activity Measurements for the CWD Piping Interior Distance Static Count (cpm) Surface Activity (dpm/100 cm2) from Bottom Top Bottom Top DM ID Start (ft)a Gamma Beta Gamma Beta Gamma Beta Gamma Beta CDW-1 4 3187 -1,200 CDW-2 11 2930 373 3131 310 -3,500 1,100 -1,700 510 CDW-3 18 2982 -3,000 CDW-4 25 3030 -2,600 CDW-5 32 3004 -2,800 CDW-6 39 3047 241 3997 533 -2,500 -180 6,000 2,700 CDW-7 46 3120 -1,800 CDW-8 53 3145 -1,600 CDW-9 60 3005 -2,800 CDW-10 67 3506 335 4980 870 1,700 760 15,000 6,100 CDW-11 74 3572 2,200 CDW-12 81 3551 2,100 CDW-13 88 3630 2,800 CDW-14 95 3487 349 5586 1117 1,500 900 20,000 8,600 CDW-15 102 3618 2,700 CDW-16 109 3702 3,400 CDW-17 116 3635 2,800 CDW-18 123 3157 317 4234 733 -1,500 580 8,200 4,700 CDW-19 130 2907 -3,700 CDW-20 137 3145 -1,600 CDW-21 144 3289 -290 CDW-22 151 3207 363 4643 935 -1,000 1,000 12,000 6,800 CDW-23 158 3031 -2,600 CDW-24 165 3319 -22 CDW-25 172 3432 990 CDW-26 179 2944 313 4419 671 -3,400 540 9,800 4,100 CDW-27 186 3016 -2,700 CDW-28 193 3046 -2,500 CDW-29 200 3220 -910 CDW-30 207 3260 351 3413 544 -550 920 820 2,900 CDW-31 214 3154 -1,500 CDW-32 221 3086 -2,100 CDW-33 228 3324 22 CDW-34 235 3216 340 3739 602 -940 810 3,700 3,400 CDW-35 242 3303 -170 CDW-36 249 3474 1,400 La Crosse CWD Confirmatory Survey A-1 5299-SR-03-0

Table A-1. Individual Surface Activity Measurements for the CWD Piping Interior Distance Static Count (cpm) Surface Activity (dpm/100 cm2) from Bottom Top Bottom Top DM ID Start (ft)a Gamma Beta Gamma Beta Gamma Beta Gamma Beta CDW-37 256 2446 -7,800 CDW-38 263 3248 328 4073 740 -660 690 6,700 4,800 CDW-39 270 3419 870 CDW-40 277 3085 -2,100 CDW-41 284 3226 -850 CDW-42 291 3378 201 4060 607 510 -580 6,600 3,500 CDW-43 298 3330 76 CDW-44 305 3567 2,200 CDW-45 312 3508 1,700 CDW-46 319 3624 338 4594 819 2,700 790 11,000 5,600 CDW-47 326 3723 3,600 CDW-48 333 3675 3,200 CDW-49 340 3422 900 CDW-50 347 3376 328 4395 610 490 690 9,600 3,500 CDW-51 354 3364 380 CDW-52 361 3419 870 CDW-53 368 3447 1,100 CDW-54 375 3336 316 4034 750 130 570 6,400 4,900 CDW-55 382 3419 870 CDW-56 389 3482 1,400 CDW-57 396 3441 1,100 CDW-58 403 3195 389 3421 367 -1,100 1,300 890 1,100 CDW-59 410 3473 1,400 CDW-60 417 5239 351 17,000 920 Mean 3325 327 4181 681 39 676 7667 4214 Median 3322 337 4073 671 0 775 6700 4100 SD 350 47 635 209 3119 464 5651 2097 n 60 16 15 15 60 16 15 15 aReferenced from the south end of the CWD pipe La Crosse CWD Confirmatory Survey A-2 5299-SR-03-0

Table A-2. Gamma Scan Data Summary Statistics (cpm)

CWD Pipe Minimum Maximum Mean SD Portion Top 2,846 5,896 3,970 641 Bottom 2,587 5,050 3,460 389 La Crosse CWD Confirmatory Survey A-3 5299-SR-03-0

APPENDIX B MAJOR INSTRUMENTATION La Crosse CWD Confirmatory Survey 5299-SR-03-0

The display of a specific product is not to be construed as an endorsement of the product or its manufacturer by the author or his employer.

B.1 SCANNING AND MEASUREMENT INSTRUMENT/DETECTOR COMBINATIONS B.1.1 Gamma Ludlum NaI(Tl) Scintillation Detector Model 44-10, Crystal: 2-inch x 2-inch (Ludlum Measurements, Inc., Sweetwater, Texas) coupled to:

Ludlum Ratemeter-scaler Model 2221 (Ludlum Measurements, Inc., Sweetwater, Texas) coupled to:

Trimble Data Logger (Trimble Navigation Limited, Sunnyvale, California)

B.1.2 Beta Ludlum Plastic Scintillation Detector Model 44-142, Physical Area: 100 cm2 (Ludlum Measurements, Inc., Sweetwater, Texas) coupled to:

Ludlum Ratemeter-scaler Model 2221 (Ludlum Measurements, Inc., Sweetwater, Texas)

La Crosse CWD Confirmatory Survey B-1 5299-SR-03-0

APPENDIX C SURVEY PROCEDURES La Crosse CWD Confirmatory Survey 5299-SR-03-0

C.1 PROJECT HEALTH AND SAFETY ORISE performed all survey activities in accordance with the ORAU Radiation Protection Manual, the ORAU Health and Safety Manual, and the ORAU Radiological and Environmental Survey Procedures Manual (ORAU 2014, ORAU 2016c, and ORAU 2016a). Prior to on-site activities, a work-specific hazard checklist was completed for the project and discussed with field personnel. The planned activities were thoroughly discussed with site personnel prior to implementation to identify hazards present.

Additionally, prior to performing work, a pre-job briefing and walk-down of the survey areas were completed with field personnel to identify hazards present and discuss safety concerns. Should ORISE have identified a hazard not covered in the ORAU Radiological and Environmental Survey Procedures Manual (ORAU 2016a) or the projects work-specific hazard checklist for the planned survey and sampling procedures, work would not have been initiated or continued until it was addressed by an appropriate job hazard analysis and hazard controls.

C.2 CALIBRATION AND QUALITY ASSURANCE Calibration of all field instrumentation was based on standards/sources, traceable to National Institute of Standards and Technology.

Calibration of field instrumentation was performed in accordance with procedures from the ORAU Radiological and Environmental Survey Procedures Manual (ORAU 2016a)

Quality control procedures included:

  • Daily instrument background and check-source measurements to confirm that equipment operation is within acceptable statistical fluctuations.
  • Training and certification of all individuals performing procedures.
  • Periodic internal and external audits.

C.3 SURVEY PROCEDURES C.3.1 Surface Scans Scans for elevated gamma radiation were performed by passing the detector slowly over the surface.

The distance between the detector and surface was maintained at a minimum. Specific scan MDCs for the NaI scintillation detectors were not determined, as the instruments were used solely as a qualitative means to identify elevated gamma radiation levels in excess of local background.

La Crosse CWD Confirmatory Survey C-1 5299-SR-03-0

Identifications of elevated radiation levels that could exceed the site criteria were determined based on an increase in the audible signal from the indicating instrument.

C.3.2 SURFACE ACTIVITY MEASUREMENTS Calibration verification activities were performed using LACBWRs flexible Cs-137 calibration standard placed inside a 152.4-cm-diameter pipe surrogate. A static count was collected with the detector mid-point centered along the width of the source (i.e., along the length of the pipe). The count time was sufficiently long, such that over 10,000 counts were accumulated, thus limiting counting error to less than one percent. The static efficiency was determined to be 3.37E-03. The median of the gamma count rate data for the bottom of the pipe was selected as the SU-specific background for the CWD piping. A representative SU-specific background from a non-impacted area was not available. The SU-specific background selected from the study area was justified based on the approximate normal distribution of the count-rate data. The median of the data set was selected, such that the one data point (near the north end pipe opening) that was elevated would not bias the background estimate high. For a static 1-minute count, the a priori minimum detectable concentration (MDC) was determined to be 2,400 dpm/100cm2 by:

3 + 4.65

=

100 2 x Where:

Bkg = Background count rate, determined to be 3,322 cpm

= detector efficiency, estimated to be on the order of 3.37E-03 G = Source area modification factor, which is 33.15 (based on the calibration source area of 3,315 cm2 (33.15 cm2/100 cm2). The detector field of view covers significantly more than this area. Previous ORISE pipe detector calibrations demonstrate that approximately 90% of the detector response to a point source (relative to the source centered with the detector midpoint) occurs within 15 cm from the detector midpoint.

Surface activity measurement data were converted to units of disintegrations per minute per 100 square centimeters (dpm/100 cm2) using the following equation:

(/100 2 )=

x La Crosse CWD Confirmatory Survey C-2 5299-SR-03-0

Where:

SA = surface activity C = measured count rate (cpm)

B = background count rate (cpm) = 3,322 cpm G = 33.15 tot = total efficiency (unitless)

Surface activity measurements for the beta data set were calculated using the previous equation only a G of 1.00 was used and the total efficiency was 0.10, based on Co-60.

La Crosse CWD Confirmatory Survey C-3 5299-SR-03-0

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