ML20034D661
| ML20034D661 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 01/31/2020 |
| From: | Altic N Oak Ridge Institute for Science & Education |
| To: | John Hickman Division of Decommissioning, Uranium Recovery and Waste Programs |
| Hickman J | |
| References | |
| Download: ML20034D661 (47) | |
Text
January 3, 2020 Mr. John Hickman U.S. Nuclear Regulatory Commission Office of Nuclear Material Safety and Safeguards Division of Decommissioning, Uranium Recovery, and Waste Programs Reactor Decommissioning Branch, Mail Stop: T8F5 11545 Rockville Pike Rockville, MD 20852
SUBJECT:
INDEPENDENT CONFIRMATORY SURVEY
SUMMARY
AND RESULTS FOR THE SUBSURFACE SOILS ASSOCIATED WITH THE SACRIFICIAL BARRIER AT THE ZION NUCLEAR POWER STATION, ZION, ILLINOIS; DOCKET NOs. 50-295 and 50-304; RFTA 18-004; DCN:
5271-SR-07-0
Dear Mr. Hickman:
Oak Ridge Institute for Science and Education (ORISE) is pleased to provide the attached report detailing the confirmatory survey activities of the sacrificial barrier subsurface soil at the Zion Nuclear Power Station in Zion, Illinois.
Please feel free to contact me at 865.574.6273 or Erika Bailey at 865.576.6659 if you have any questions or comments.
Sincerely, ncerely, Nick i kAA. Altic, Al i CHP Health Physicist/Project Manager ORISE NAA:tb Attachment electronic distribution: K. Conway, NRC B. Lin, NRC R. Edwards, NRC D. Hagemeyer, ORISE E. Bailey, ORISE J. Lee, ORISE File/5271 100 ORAU Way
- Oak Ridge
- TN 37830
- orise.orau.gov
INDEPENDENT CONFIRMATORY SURVEY
SUMMARY
AND RESULTS FOR THE SUBSURFACE SOILS ASSOCIATED WITH THE SACRIFICIAL BARRIER AT THE ZION NUCLEAR POWER STATION ZION, ILLINOIS N. A. Altic, CHP and J. D. Lee ORISE FINAL REPORT Prepared for the U.S. Nuclear Regulatory Commission JANUARY 2020 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 SUBSURFACE SOILS ASSOCIATED WITH THE SACRIFICIAL BARRIER AT THE ZION NUCLEAR POWER STATION ZION, ILLINOIS FINAL REPORT Prepared by N. A. Altic, CHP and J. D. Lee ORISE JANUARY 2020 Prepared for the U.S. Nuclear Regulatory Commission This document was prepared for the U.S. Nuclear Regulatory Commission by the Oak Ridge Institute for Science and Education (ORISE) through interagency agreement number 31310018N0014 with the U.S. Department of Energy (DOE). ORISE is managed by Oak Ridge Associated Universities (ORAU) under DOE contract number DE-SC0014664.
Zion Sacrificial Subsurface 5271-SR-07-0
INDEPENDENT CONFIRMATORY SURVEY
SUMMARY
AND RESULTS FOR THE SUBSURFACE SOILS ASSOCIATED WITH THE SACRIFICIAL BARRIER AT THE ZION NUCLEAR POWER STATION ZION, ILLINOIS Prepared by: Date:
N. A. Altic, CHP, Health Physicist/Project Manager ORISE RISE Prepared by: Date:
J. D. Lee, Assistant Project Manager ORISE Reviewed by: Date:
P. H. Benton, Quality Manager ORISE Reviewed by: Date:
W. F. Smith, Senior Chemist ORISE Reviewed and approved for release by: Date:
E. N. Bailey, Survey and Technical Projects Group Manager ORISE FINAL REPORT JANUARY 2020 Zion Sacrificial Subsurface i 5271-SR-07-0
CONTENTS FIGURES .......................................................................................................................................................... iii TABLES ............................................................................................................................................................. iii ACRONYMS .................................................................................................................................................... iv EXECUTIVE
SUMMARY
.............................................................................................................................. v
- 1. INTRODUCTION....................................................................................................................................... 1
- 2. SITE DESCRIPTION ................................................................................................................................. 2
- 3. DATA QUALITY OBJECTIVES ............................................................................................................. 4 3.1 STATE THE PROBLEM ........................................................................................................................ 4 3.2 IDENTIFY THE DECISION/OBJECTIVE ........................................................................................... 4 3.3 IDENTIFY INPUTS TO THE DECISION/OBJECTIVE ....................................................................... 5 3.3.1 Radionuclides of Concern and Release Guidelines.............................................................. 6 3.4 DEFINE THE STUDY BOUNDARIES ................................................................................................. 7 3.5 DEVELOP A DECISION RULE ........................................................................................................... 8 3.6 SPECIFY LIMITS ON DECISION ERRORS ......................................................................................... 9 3.7 OPTIMIZE THE DESIGN FOR OBTAINING DATA .......................................................................... 9
- 4. PROCEDURES ..........................................................................................................................................10 4.1 REFERENCE SYSTEM .......................................................................................................................10 4.2 SURFACE SCANS ...............................................................................................................................10 4.3 MEASUREMENT/SAMPLING LOCATIONS .....................................................................................10 4.4 SOIL SAMPLING ................................................................................................................................11
- 5. SAMPLE ANALYSIS AND DATA INTERPRETATION ...............................................................11
- 6. FINDINGS AND RESULTS ...................................................................................................................12 6.1 SURFACE SCANS ...............................................................................................................................12 6.1.1 April 2019 Gamma Walkover Scans ....................................................................................13 6.1.2 July 2019 Gamma Walkover Scans ......................................................................................14 6.2 SOIL SAMPLING ................................................................................................................................14 6.2.1 April 2019 Soil Sampling .......................................................................................................14 6.2.2 July 2019 Soil Sampling ..........................................................................................................16
- 7.
SUMMARY
AND CONCLUSIONS ......................................................................................................18
- 8. REFERENCES ...........................................................................................................................................20 APPENDIX A FIGURES APPENDIX B TABLES APPENDIX C SURVEY AND ANALYTICAL PROCEDURES APPENDIX D MAJOR INSTRUMENTATION Zion Sacrificial Subsurface ii 5271-SR-07-0
FIGURES Figure 2.1. ZNPS Overview (Adapted from ZS 2018) ................................................................................ 3 Figure 2.2. Overview of ZNPS Survey Units (Adapted from NRC 2019)................................................ 3 Figure 3.1. SUs Associated with the Power Block Subject to Confirmatory Surveys.............................. 8 Figure 6.1 Q Plot of Gamma Walkover Data for April 2019 and July 2019 Confirmatory Surveys...13 Figure 6.2. Strip Chart for the April 2019 Confirmatory Survey Soil Samples .......................................16 Figure 6.3. Strip Chart for the July 2019 Confirmatory Survey Soil Samples .........................................17 TABLES Table 3.1. ZNPS Confirmatory Survey Decision Process ........................................................................... 5 Table 3.2. ZNPS Subsurface Soil DCGLs and Corresponding MDCs ..................................................... 6 Table 6.1. Summary of ROC Concentrations in Soil Samples Collected During the April 2019 Site Visit ....................................................................................................................................................................15 Table 6.2. Radionuclide Activity of Discrete Particles from the April 2019 Site Visit ..........................16 Table 6.3. Summary of ROC Concentrations in Soil Samples Collected During the July 2019 Site Visit ....................................................................................................................................................................17 Table 6.4. Radionuclide Activity of Discrete Particles from the July 2019 Site Visit ............................18 Zion Sacrificial Subsurface iii 5271-SR-07-0
ACRONYMS AA alternate action CFR Code of Federal Regulations Co-60 cobalt-60 cpm counts per minute Cs-137 cesium-137 DCGL derived concentration guideline level DCGLBC Base Case DCGL DCGLEMC elevated measurement comparison DCGL DCGLOp Operational DCGL DOE Department of Energy DQO data quality objective DRP discrete radioactive particle DS decision statement Exelon Exelon Generation Company FSS final status survey GPS global positioning system H-3 tritium HTD hard-to-detect LTP license termination plan Ci microcuries MARSSIM Multi-Agency Radiation Survey and Site Investigation Manual MDC minimum detectable concentration MeV mega electron volt mrem/yr millirem per year NaI sodium iodide Ni-63 nickel-63 NIST National Institute of Standards and Technology NRC U.S. Nuclear Regulatory Commission ORAU Oak Ridge Associated Universities ORISE Oak Ridge Institute for Science and Education pCi/g picocuries per gram PSQ principal study question Q quantile RA radiological assessment REAL Radiological and Environmental Analytical Laboratory ROC radionuclide of concern SOF sum of fractions Sr-90 strontium-90 SU survey unit TAP total absorption peak TEDE total effective dose equivalent ZNPS Zion Nuclear Power Station ZS ZionSolutions, LLC Zion Sacrificial Subsurface iv 5271-SR-07-0
INDEPENDENT CONFIRMATORY SURVEY
SUMMARY
AND RESULTS FOR THE SUBSURFACE SOILS ASSOCIATED WITH THE SACRIFICIAL BARRIER AT THE ZION NUCLEAR POWER STATION ZION, ILLINOIS EXECUTIVE
SUMMARY
The U.S. Nuclear Regulatory Commission (NRC) requested that the Oak Ridge Institute for Science and Education (ORISE) perform confirmatory survey activities of subsurface soils associated with the sacrificial barrier at the Zion Nuclear Power Station (ZNPS). During the period of April 16-18, 2019 and July 15-19, 2019, ORISE performed an independent confirmatory survey consisting of gamma walkover surface scans and soil sampling.
During the April 2019 confirmatory survey, ORISE staff performed gamma surface scans that identified locations of elevated response distinguishable from localized background. As the survey progressed, the site requested that the U.S. Nuclear Regulatory Commission (NRC) suspend confirmatory survey activities while the site evaluated the anomalies. NRC agreed to the request, but did ask that ORISE analyze all collected confirmatory samples. A total of 16 judgmental soil samples were collected from 15 individual locations. Two samples were discrete radioactive particles (DRPs) that consisted solely of cobalt-60 (Co-60). One other sample location contained concrete-like debris contaminated with cesium-137 (Cs-137), and the surrounding soils exceeded a sum of fractions (SOF) of unity, based on the Operational derived concentration guideline level (DCGLOp). All other radionuclides of concern (ROCs)including strontium-90 (Sr-90) and nickel-63 (Ni-63)were less than their respective DCGLOp. All Sr-90 and tritium (H-3) concentrations were less than the analytical minimum detectable concentration (MDC).
In July of 2019, at the request of NRC, ORISE returned to the site to re-perform the previously planned and partially implemented confirmatory surveys. A total of 21 judgmental samples were collected from 19 individual locations. One sample, containing predominately Cs-137, exceeded the allowable SOF [unity] based on the DCGLOp, but was less than the allowable limit when compared to the Base Case DCGL (DCGLBC). Two samples contained DRPs that consisted solely of Co-60.
All other results for gamma-emitting ROCs were less than the DCGLOp. A subset of eight soil samples were selected based on the gamma spectrometry results and were analyzed for Sr-90, Ni-63, and H-3. Only Ni-63 was detected above the analytical MDC, but at concentrations less than 1% of the DCGLOp. Based on the results of the July 2019 confirmatory survey, the study area does contain residual radioactivity, and the results of the survey are provided herein for NRCs evaluation.
Zion Sacrificial Subsurface v 5271-SR-07-0
INDEPENDENT CONFIRMATORY SURVEY
SUMMARY
AND RESULTS FOR THE SUBSURFACE SOILS ASSOCIATED WITH THE SACRIFICIAL BARRIER AT THE ZION NUCLEAR POWER STATION ZION, ILLINOIS
- 1. INTRODUCTION The Zion Nuclear Power Station (ZNPS) consisted of two reactors, Units 1 and 2, which operated commercially from 1973 to 1997 and 1974 to 1996, respectively. Cessation of nuclear operations was certified in 1998 after both reactor units were defueled and the fuel assemblies had been placed in the spent fuel pool. Both units were then placed in safe storage pending the commencement of site decommissioning and dismantlement. In 2010, the U.S. Nuclear Regulatory Commission (NRC) operating license was transferred from Exelon Generation Company (Exelon) to ZionSolutions, LLC (ZS) to allow the physical decommissioning process, which is expected to be completed within 10 years. The end-state and primary decommissioning objective at ZNPS is the transfer of all spent nuclear fuel to the independent spent fuel storage installation and to reduce residual radioactivity within structures and soils to levels below the criteria specified in 10 Code of Federal Regulations (CFR) 20.1402, permitting release of the site for unrestricted use. Upon successful completion of the decommissioning activities, control and responsibility for the site will be transferred back to Exelon and the independent spent fuel storage installation will be maintained under Exelons Part 50 license (EC 2015).
As part of decommissioning, all above-grade structures, with a few exceptions, were demolished.
Structures below the 588-foot elevation (referenced from mean sea level), consisting of primarily exterior subgrade walls and floors, remain. These basement structures were backfilled as part of the final site restoration. In order to demonstrate compliance with the release criteria in 10 CFR 20.1402, ZS implemented final status survey (FSS) activities of remaining basement structures, along with associated embedded piping and penetrations, buried piping, and remaining soil. FSS methodologies are outlined in Chapter 5 of ZSs license termination plan (LTP) (ZS 2018).
FSS methods are based on those outlined in the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) (NRC 2000). NRC issued license amendments 191 and 178 to approve ZSs LTP in September of 2018 (NRC 2018).
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For this specific effort, ZS placed clean borrow over the original grade to catch materials, such as dust and debris generated and dispersed by demolition activities. This borrow layer is referred to as the sacrificial barrier. After demolition activities were concluded, ZS removed the sacrificial barrier plus other soils from the original grade, thus leaving an exposed subsurface layer that presumably had not been radiologically impacted by site operations. ZS performed high-density gamma walkover surveys of the exposed subsurface layer as part of a radiological assessment (RA). ZS committed to collecting volumetric subsurface samples after land restoration as part of the FSS.
NRC requested that the Oak Ridge Institute for Science and Education (ORISE) perform a confirmatory survey of the exposed soils following the removal of the sacrificial barrier at ZNPS.
- 2. SITE DESCRIPTION ZNPS is located in Lake County, Illinois, on the easternmost portion of the city of Zion. It is approximately 64 kilometers (40 miles) north of Chicago, Illinois, and 68 kilometers (42 miles) south of Milwaukee, Wisconsin. The owner-controlled site is composed of approximately 134 hectares (331 acres) and is situated between the northern and southern parts of Illinois Beach State Park on the western shore of Lake Michigan (EC 2015 and ZS 2018). Figure 2.1 provides an overview of ZNPS. The site and its surrounding environs is relatively flat, with the elevation of the developed portion of the site at approximately 591 feet above mean sea level. For reference, the elevation of Lake Michigan, which bounds the site on the east, is approximately 577.4 feet at low water level (ZS 2018).
The area within the security-restricted fence contained the principal components of the power plant, including the two containment vessels, the turbine, the crib house, and a waste water treatment facility. The site subdivided land areas into survey units (SUs), which are outlined in Figure 2.2.
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Figure 2.1. ZNPS Overview (Adapted from ZS 2018)
Figure 2.2. Overview of ZNPS Survey Units (Adapted from NRC 2019)
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- 3. DATA QUALITY OBJECTIVES The data quality objectives (DQOs) described herein are consistent with the Guidance on Systematic Planning Using the Data Quality Objectives Process (EPA 2006), and provide a formalized method for planning radiation surveys, improving survey efficiency and effectiveness, and ensuring that the type, quality, and quantity of data collected are adequate for the intended decision applications.
The seven steps of the DQO process are 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 Confirmatory survey DQOs were originally presented in ORISE 2019 and are represented here for completeness.
3.1 STATE THE PROBLEM The first step in the DQO process defined the problem that necessitated the study. NRC requested that ORISE perform confirmatory surveys at ZNPS. The objectives of the confirmatory survey activities were to provide NRC with independent confirmatory data for NRCs consideration in the evaluation of the sites RA results. The problem statement was formulated as follows:
Confirmatory survey activities are necessary to generate independent radiological data for NRCs consideration in the evaluation of the RA survey design, implementation, and results for demonstrating compliance with the release criteria.
3.2 IDENTIFY THE DECISION/OBJECTIVE The second step in the DQO process identified the principal study questions (PSQs) and alternate actions (AAs), developed a decision statement (DS), and organized multiple decisions, as appropriate.
This was done by specifying AAs that could result from a Yes response to the PSQ and combining the PSQ and AAs into a DS. Table 3.1 presents the confirmatory survey decision process.
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Table 3.1. ZNPS Confirmatory Survey Decision Process Principal Study Question Alternate Actions Yes:
Compile confirmatory data and report results to NRC for their decision making. Provide independent interpretation of confirmatory survey results that identified anomalous field or laboratory data and/or when sample population examination/assessment conditions have been met.
Did confirmatory survey results identify residual radiological contamination in the No:
subsurface soil associated with the sacrificial Compile confirmatory data and report results to NRC barrier land area? for their decision making. Provide independent interpretation that confirmatory field surveys did not identify anomalous areas of residual radioactivity, that quantitative field and laboratory data satisfy the NRC-approved decommissioning criteria, and/or that sample population examination/assessment conditions have been met.
Decision Statement Confirmatory survey results did/did not identify anomalous results or other conditions, and the results were/were not below the NRC-approved endpoint criteria.
3.3 IDENTIFY INPUTS TO THE DECISION/OBJECTIVE 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 that would meet data requirements. For this effort, information inputs included the following:
x Site-generated RA data for the subject soil surfaces x Zion Station Restoration Project License Termination Plan (ZS 2018) x Subsurface soil derived concentration guideline levels (DCGLs) for radionuclides of concern (ROCs) plus respective scan and analytical minimum detectible concentrations (MDCs), which are discussed in subsection 3.3.1. Because the excavation surface is below the original grade and the areas will eventually be covered with fill, subsurface guidelines are used for this evaluation x ORISE confirmatory direct gamma radiation scans x ORISE soil sample analytical results Zion Sacrificial Subsurface 5 5271-SR-07-0
3.3.1 Radionuclides of Concern and Release Guidelines The primary ROCs identified for ZNPS are beta-gamma emittersfission and activation products listed in Table 3.2resulting from reactor operations. ZS developed site-specific DCGLs that correspond to a residual radioactive contamination level, above background, which could result in a total effective dose equivalent (TEDE) of 25 millirem per year (mrem/yr) to an average member of the critical group. These DCGLsdefined in ZSs LTP as Base Case DCGLs (DCGLBCs)are radionuclide-specific and independently correspond to a TEDE of 25 mrem/yr for each source term.
The initial suite of ROCs present at ZNPS has been reduced based on an insignificant dose contribution from a number of radionuclides. As such, the DCGLBCs have been reduced to account for the dose from these insignificant radionuclides.
In order to ensure that the total dose from all site-related source termsbasement structures, soils, buried piping, and groundwateris less than the NRC-approved release criteria, the DCGLBCs are further reduced to Operational DCGLs (DCGLOps). The DCGLOps represent the expected dose from prior investigations and are used for remediation and FSS/RA design purposes. DCGLBCs and DCGLOps for subsurface soil, accounting for insignificant dose contributors, are provided in Table 3.2. Note that ZS did not identify tritium (H-3) as a primary ROC; however, it was included as part of this study, as requested by NRC.
Table 3.2. ZNPS Subsurface Soil DCGLsa and Corresponding MDCs (pCi/g)
Nominal Analytical ROC DCGLBC DCGLOp Scan MDCb MDCc Co-60 3.44 0.881 3 to 5 < 0.1 Cs-134 4.44 1.137 Unknown < 0.1 Cs-137 7.75 1.984 6 to 8 < 0.1 Ni-63 763.02 195.333 HTD <2 Sr-90 1.66 0.425 HTD ~0.2 H-3 -d -d HTD <3 aRecreated from ZS 2018 bApproximated using the methods described in NRC 2000 cBased on observed analytical MDCs dH-3 is not identified as a primary ROC; therefore, DCGLs are not available pCi/g = picocuries per gram MDC = minimum detectible concentration HTD = hard-to-detect ROCs; scanning instrument not sensitive to these ROCs Any detection suggesting the presence of residual contamination present after the sacrificial soils were removed may have resulted in some action. Because each individual DCGLBC represents a separate Zion Sacrificial Subsurface 6 5271-SR-07-0
radiological dose, the sum-of-fractions (SOF) approach must be used to evaluate the total dose from the SU and must demonstrate compliance with the dose limit. Typically, the SOF would be calculated with the average ROC concentration; however, since only judgmental samples were collected, the SOF was calculated for each sample using Equation 3-1.
= Eq. (3-1)
Where:
Csample,j is the sample concentration of ROC j DCGL,j is the DCGLBC/DCGLOp for ROC j 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. Confirmatory surveys were conducted during two periods [site visits]: April 16-18, 2019, and July 15-19, 2019. Physical boundaries of the confirmatory activities were the SUs associated with the power block (see Figure 3.1) that contained the sacrificial barrier. Additional physical boundaries for the confirmatory activities depended on safe access considerations. The primary reason for not achieving 100% investigation of the subject area was standing water. The ORISE survey team was not permitted to access these areas because the depth of the water was unknown. All survey subunits associated with the power block are designated as a Class 1 by the site.
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Figure 3.1. SUs Associated with the Power Block Subject to Confirmatory Surveys 3.5 DEVELOP A DECISION RULE The fifth step in the DQO process specified appropriate population parameters (e.g., mean, median),
evaluated action levels relative to the appropriate detection limits, and developed an ifthen decision rule statement. Decision rules for this survey were based on independent scan surveys and soil sample results.
Hypothesis testing adopts a scientific approach where the survey data are used to select between the baseline condition (the null hypothesis, H0) and an alternative condition (HA). A significant subsurface soil source term was not expected; therefore, any positive detection may have required follow-up action, and, thus, a formal statistical comparison was unnecessary. Therefore, the null and alternative hypothesis were as follows:
H0: Subsurface soils beneath the sacrificial layer do not contain residual ROC contamination HA: Subsurface soils beneath the sacrificial layer do contain residual ROC contamination Zion Sacrificial Subsurface 8 5271-SR-07-0
Rejection of the null hypothesis may not indicate that the area is unacceptable for release. The area of residual contamination also should be considered. Ultimately, NRC will assess the acceptability of any remaining hot spots identified during the confirmatory survey.
Qualitative parameters of interest included gamma walkover survey data collection over accessible soils (i.e., surface soils beneath the sacrificial barrier after it was removed). Locations with levels of radiation distinguishable from localized backgroundas determined in real time by the surveyor during direct gamma scans and/or based on post-processing of scan datawere marked for further investigation. For this study, the quantitative parameters of interest are individual soil sample concentrations and the associated analytical MDC. The decision rule was stated as follows:
If ROC concentrations in confirmatory samples are reported less than analytical detection limits, then the subject area is presumed to be free of residual contamination. Otherwise, the subject area may be impacted by site operations and additional action may be required. Present results to NRC for their evaluation.
3.6 SPECIFY LIMITS ON DECISION ERRORS The sixth step in the DQO process examined the consequences of making an incorrect decision and established bounds of decision errors. Decision errors were controlled both during the confirmatory activities and during data quality assessments. As shown in Table 3.2, detector scan MDCs for gamma-emitting ROCs were expected to be above subsurface soil DCGLOps. Any anomalies above background identified while performing the surveys or subsequent data assessment were thoroughly investigated and discussed with NRC staff. Additionally, analytical MDCs were approximately 10% of the DCGLOpwith the exception of strontium-90 (Sr-90), which was approximately 50% of the DCGLOp, as indicated in Table 3.2.
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, select the sample size to satisfy DQOs, decide on the most resource-effective design of agreed alternatives, and document requisite details. Specific survey procedures are presented in Section 4.
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- 4. PROCEDURES The ORISE survey team performed visual inspections, measurements, and sampling activities within the accessible survey areas specifically requested by NRC. Survey activities were conducted in accordance with the Oak Ridge Associated Universities (ORAU) Radiological and Environmental Survey Procedures Manual and the ORAU Environmental Services and Radiation Training Quality Program Manual (ORAU 2016a and currently ORAU 2019a).
4.1 REFERENCE SYSTEM ORISE referenced confirmatory measurement/sampling locations using global positioning system (GPS) coordinates using Illinois East State Plane 1201 NAD 1983 (meters). Measurement and sampling locations were documented on detailed survey maps.
4.2 SURFACE SCANS Ludlum model 44-10 2-inch by 2-inch thallium doped sodium iodide (NaI[Tl]), hereafter referred to as NaI, detectors were used to evaluate direct gamma radiation levels for land areas. Accessible areas associated with the power block SUs were scanned with medium- to high-density coverage. All detectors were coupled to Ludlum Model 2221 ratemeter-scalers with audible indicators. Ratemeter-scalers also were coupled to hand-held GPS data-loggers to electronically record detector response concurrently with geospatial coordinates. Locations of elevated response that were audibly distinguishable from localized background levels, suggesting the presence of residual contamination, were marked for further investigation via volumetric sampling. Additionally, direct gamma scan data were processed and reviewed prior to leaving the site in order to identify any additional judgmental sampling locations.
4.3 MEASUREMENT/SAMPLING LOCATIONS Random samples were not specifically required to assess the mean concentrationany single positive detection may have resulted in follow-up actions, but were proposed to achieve greater probability of detecting a location with a soil concentration greater than the DCGL, but less than the scan MDC.
However, temporal boundaries prevented the collection of a random data set as planned. Therefore, as agreed upon by NRC, all samples/measurements were collected from judgmental locations. The Zion Sacrificial Subsurface 10 5271-SR-07-0
ORISE field team used all available time onsite to perform gamma walkovers and collect judgmental samples.
4.4 SOIL SAMPLING Soil sampling locations were judgmentally selected from the study area and collected following the removal of the sacrificial barrier. These samples will represent subsurface soil conditions after final backfill. Soil samples were collected from the exposed surface to a depth of 15 centimeters. A total of 37 samples were collected between the two site visits16 samples in April and 21 samples in July.
Four sample locationstwo from the April 2019 site visit and two from the July 2019 site visit exhibited indications of a discrete radioactive particle (DRP) versus volumetric contamination (i.e., the NaI detector response was highly localized). The presence of DRPs was confirmed at each location, and the particles were isolated while onsite. During the April site visit, the DRPs were isolated in the field prior to sample collection. The DRPs collected during the July site visit were isolated after the volumetric soil sample was collected. The DRPs were collected for confirmatory analysis in order to confirm the contaminants.
One-minute, static NaI counts were performed at each sample location pre- and post-sample collection. The static measurements were used to assess the potential for contamination at depth.
- 5. SAMPLE ANALYSIS AND DATA INTERPRETATION Samples and data collected on site were transferred to the ORISE facility for analysis and interpretation. Sample custody was transferred to the Radiological and Environmental Analytical Laboratory (REAL) in Oak Ridge, Tennessee. Sample analyses were performed in accordance with the ORAU Radiological and Environmental Analytical Laboratory Procedures Manual (currently ORAU 2019b).
With exception of isolated particles, samples were homogenized and analyzed by high-resolution gamma spectrometry for gamma-emitting fission and activation products. Results for the volumetric soil samples were reported in units of picocuries per gram (pCi/g). The DRPs were reported in units of total activitymicrocuries (Ci)because a concentration value in pCi/g is not applicable to the DRP results.
Select soil samples also were analyzed for hard-to-detect (HTD) ROCs. As directed by NRC, all samples from the April 2019 sampling effort, excluding the DRPs and sample 5271S0045, and a Zion Sacrificial Subsurface 11 5271-SR-07-0
subset of eight samples from the July 2019 effort were selected for analysis of HTD ROCs. The selections were based primarily on the gamma spectrometry results. For the HTD analysis, REAL prepared samples utilizing wet chemistry and material oxidation. Samples then underwent separation and were analyzed for Sr-90, nickel-63 (Ni-63), and H-3 by low-background proportional or liquid scintillation counting, as applicable. All HTD analytes were reported in units of pCi/g.
Scan data were graphed in quantile (Q) plots and histograms for assessment. The Q plot is a graphical tool for assessing the distribution of a data set. In viewing the Q plots provided, the Y-axis represents ROC concentrations in units of counts per minute (cpm). The X-axis represents the data quantiles about the mean value. Values less than the mean are represented in the negative quantiles; the values greater than the mean are represented in the positive quantiles. A normal distribution that is not skewed by outliers (i.e., a background population) will 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, appears as a step function.
Soil sample analytical results were plotted using strip charts, often referred to as one-dimensional scatter plots.
- 6. FINDINGS AND RESULTS The results of the confirmatory survey are discussed in the following subsections.
6.1 SURFACE SCANS Figure 6.1 presents the overall Q plot for the scan data from each site visit. The sharp increase in the Q plot at the upper quantile is associated with the DRPs. As previously discussed, certain site conditions, such as excavations and/or standing water, rendered some areas inaccessible. The details of each site visit are discussed in the following subsections.
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Figure 6.1 Q Plot of Gamma Walkover Data for April 2019 and July 2019 Confirmatory Surveys 6.1.1 April 2019 Gamma Walkover Scans In April 2019, ORISE staff performed gamma surface scans in portions of SUs 12102, 12104, 12105, 12106, 12107, and 12108. Overall, the gamma detector scan responses ranged from 3,400 to 600,000 cpm. A histogram of the scan data is provided in Figure A.2 in Appendix A. Note that all results above 17,000 cpm are combined in one bin to allow for better visibility of the lower count rate region of the distribution. Review of the histogram reveals a multi-modal distribution (i.e., multiple backgrounds). The ORISE field team noted multiple soil types, ranging from sand to clay, each with a different background. Note that the clay exhibited the highest background at approximately 10,000 cpm. Multiple backgrounds within each SU prevent the use of a fixed NaI action level to identify judgmental sampling locations, which is why ORISE based sampling decisions on an increase in detector response relative to localized background.
Detector response peaked at approximately 600,000 cpm, which resulted in the identification and collection of a DRP. This location is presented as 5271S0039 in Figure A.3. A second notable instance resulted in a detector response of approximately 100,000 cpm, which also resulted in the identification and collection of a DRP. This location is presented as 5271S0054 in Figure A.3.
Zion Sacrificial Subsurface 13 5271-SR-07-0
6.1.2 July 2019 Gamma Walkover Scans During the July 2019 confirmatory survey effort, ORISE performed gamma walkover scans of all area soils associated with the sacrificial barrier within the power block boundaries, including the SUs previously scanned in April 2019. Overall, the gamma detector scan responses ranged from approximately 3,500 to 40,000 cpm. A histogram of the scan data is provided in Figure A.5. Note that all results above 17,000 cpm are combined in one bin to allow for better visibility of the lower count rate region of the distribution. Review of the histogram reveals a multi-modal distribution similar to that of the April survey. The histogram for the July data appears more refined, as indicated by the sharper peak at approximately 6,000 cpm and the more defined curves. The increase in definition is due to a much larger data set for the July survey relative to the April survey.
Detector response peaked at approximately 40,000 cpm, which resulted in the identification and collection of a DRP. This location is presented as 5271S0056 in Figure A.6. A second notable instance resulted in a detector response of approximately 38,000 cpm, which also resulted in the identification of a DRP. This location is presented as 5271S0055 in Figure A.6.
6.2 SOIL SAMPLING Soil sample locations for the April 2019 and July 2019 efforts are provided in Figures A.3 and A.6, respectively. Individual soil sample results are presented in Table B.1 in Appendix B. Details regarding the soil sample results for each site visit are discussed in the following subsections.
6.2.1 April 2019 Soil Sampling A total of 16 samples were collected from 15 locations during the April 2019 survey, two of which were DRPs. Table 6.1 presents a summary of the analytical results for the soil samples collected during this effort. Cobalt-60 (Co-60) and cesium-137 (Cs-137) had concentrations above the analytical MDC in four and three of the 16 confirmatory samples, respectively. Co-60 concentrations in the confirmatory soil samples ranged from -0.013 to 3.69 pCi/g, while Cs-137 concentrations ranged from
-0.031 to 1,672 pCi/g. The maximum observed concentrations for both Co-60 and Cs-137 were identified in sample 5271S0045, which was a piece of concrete-like debris collected from SU 12202.
The results for 5271S0045 are approximate as the smallest calibrated geometry the laboratory utilizes for analysis still contained dead space. Sample 5271S0046 was the soil surrounding the debris Zion Sacrificial Subsurface 14 5271-SR-07-0
[5271S0045], and it was determined to have Co-60 and Cs-137 concentrations of 0.303 and 6.91 pCi/g, respectively.
Table 6.1. Summary of ROC Concentrations in Soil Samples Collected During the April 2019 Site Visit (pCi/g)
Parameter Co-60 Cs-134 Cs-137 Ni-63 Sr-90 H-3 SOFOpa SOFBCa Min -0.013 -0.035 -0.031 0.9 0.01 -1.7 0.07 0.02 Max 3.69b 0.040 1672b 3.8 0.20 -0.20 847 217 aThe SOF does not include the fractional contribution from tritium; adjusted DCGLs are not presented in the sites LTP bSample result is approximate. Results are from S0045 Thirteen of the samples were analyzed for Ni-63, Sr-90, and H-3. Sample 5271S0045 and the DRPs were not analyzed for HTD radionuclides. Five of the 13 samples had Ni-63 concentrations above the analytical MDC, with a maximum concentration of 3.8 pCi/g in sample 5271S0046. The Sr-90 and H-3 concentrations reported were less than the analytical MDC in the confirmatory samples.
Figure 6.2 presents a strip chart of the soil sample results from the April 2019 survey effort. Sample 5271S0045 was not included in the strip chart because the magnitude of the Co-60 and Cs-137 results were much higher than the rest of the samples. As indicated by the clustering of data pointswith the exception of one data point for Co-60 and Cs-137, there is not a wide range of concentration values within the judgmental data set, indicating results are at or near background values. The SOF values exceeding unity are from the same sample, 5271S0046, which was the soil surrounding the concrete-like debris [5271S0045] collected in SU 12202.
Zion Sacrificial Subsurface 15 5271-SR-07-0
Figure 6.2. Strip Chart for the April 2019 Confirmatory Survey Soil Samples Analytical results for the DRPs are presented in Table 6.2. Co-60 was the only ROC identified above the analytical MDC in these samples. Results were not compared to the DCGL or the elevated measurement comparison DCGL (DCGLEMC) because the physical form of the sample does not match the conceptual site model.
Table 6.2. Radionuclide Activity of Discrete Particles from the April 2019 Site Visit ROC Activity and Uncertainty (Ci)
Sample ID Survey Unit Co-60 Cs-134 Cs-137 5271S0039 12106 1.757 +/- 0.094a -1.20E-04 +/- 6.70E-04 6.90E-04 +/- 3.20E-04 5271S0054 12106 0.372 +/- 0.011 -3.0E-05 +/- 7.30E-04 2.40E-04 +/- 3.20E-04 aUncertainties represent the total propagated uncertainty reported at the 95% confidence level 6.2.2 July 2019 Soil Sampling A total of 21 samples were collected from 19 locations during the July 2019 survey, two of which were DRPs. Table 6.3 presents a summary of the soil sample results. Co-60 and Cs-137 were positively identified above analytical MDC in five and four of the 19 confirmatory samples, respectively. Co-60 concentrations in the confirmatory soil samples ranged from -0.016 to 0.511 pCi/g, while Cs-137 concentrations ranged from -0.030 to 1.70 pCi/g. The maximum observed concentration for both Co-60 and Cs-137 was identified in sample 5271S0073 from SU 12202A.
Zion Sacrificial Subsurface 16 5271-SR-07-0
Table 6.3. Summary of ROC Concentrations in Soil Samples Collected During the July 2019 Site Visit (pCi/g)
Parameter Co-60 Cs-134 Cs-137 Ni-63 Sr-90 H-3 SOFOpa SOFBCa Min -0.016 -0.043 -0.030 0.04 -0.020 -1.00 0.00 0.00 Max 0.511 0.041 1.70 1.68 0.11 0.6 1.45 0.37 aThe SOF does not include the fractional contribution from tritium Eight of the 21 samples were analyzed for HTDs. One of the eight samples had Ni-63 concentration above the analytical MDC, with a maximum concentration of 1.68 pCi/g in sample 5271S0073. The Sr-90 and H-3 concentrations reported were less than the analytical MDC in the confirmatory samples.
Figure 6.3 presents a strip chart of the soil sample results from the July survey effort. As indicated by the clustering of data pointswith the exception of sample 5271S0073, there is not a wide range of concentration values within the judgmental data set, indicating results are at or near background values. Sample 5271S0073 exceeded an SOF of unity based on the DCGLOps; individual ROC concentrations were below their respective DCGLOp. However, when these results were compared to the DCGLBC, the resulting SOF was 0.37.
Figure 6.3. Strip Chart for the July 2019 Confirmatory Survey Soil Samples Zion Sacrificial Subsurface 17 5271-SR-07-0
DRPs from soil samples 5271S0055 and 5271S0056 were isolated and containerized prior to leaving the site. The DRPs were assigned their original same sample ID with an A appended to the end.
Total activity results for the DRPs are presented in Table 6.4 below. Note that, as stated in Section 4.4, the DRPs collected during the April Site visit were isolated prior to sample collection, and, thus, were assigned a sample ID without the A designation.
Table 6.4. Radionuclide Activity of Discrete Particles from the July 2019 Site Visit ROC Activity and Uncertainty (Ci)
Sample ID Survey Unit Co-60 Cs-134 Cs-137 5271S0055A 12202D 0.259 +/- 0.013a 6.0E-05 +/- 2.00E-04 5.0E-05 +/- 1.30E-04 5271S0056A 12202F 0.450 +/- 0.023 -8.0E-05 +/- 3.60E-04 1.40E-04 +/- 1.40E-04 aUncertainties represent the total propagated uncertainty reported at the 95% confidence level
- 7.
SUMMARY
AND CONCLUSIONS During the period of April 16-18, 2019, and July 15-19, 2019, ORISE performed independent confirmatory survey activities of subsurface soils associated with the sacrificial barrier at ZNPS. The confirmatory surveys consisted of gamma walkover scans and surface soil sampling (i.e., post removal of the sacrificial barrier). As a result of the gamma walkover surveys, a total of 37 locations between the two site visits were flagged for further investigation by soil sampling.
During the April 2019 site visit, a total of 16 samples were collected from 15 locations, two of which were DRPs with a total Co-60 activity of 0.372 and 1.757 Ci. After removal of the DRPs from the soil, the NaI detector response returned to background, indicating capture of all contamination.
Concrete-like debris containing Cs-137 was identified at another location, and the surrounding soil exceeded the SOF allowance [unity] based on the DCGLBC. All other samples were below the DCGLOp for selected ROCs. The site requested that NRC suspend confirmatory survey activities while the site evaluated the anomalies, to which NRC agreed. As a result, the entire power block was not surveyed as planned.
After the site completed their evaluation and corrective actions for the subject soils, NRC requested that ORISE return and re-perform the originally planned confirmatory survey activities. This site visit occurred in July 2019, during which a total of 21 soils samples were collected from 19 locations. Two Zion Sacrificial Subsurface 18 5271-SR-07-0
samples contained DRPs with a total Co-60 activity of 0.259 and 0.450 Ci. After removal of the DRPs from the soil, the NaI detector response returned to background, indicating capture of all contamination. One other sample exhibited an SOF greater than unity based on the DCGLOp, but less than unity based on the DCGLBC. All other individual ROC sample concentrations were either less than the analytical MDC or below the DCGLOp. Based on the results of the July 2019 confirmatory survey, the study area contains residual radioactivity, and the results to the survey are provided herein for NRCs evaluation.
Zion Sacrificial Subsurface 19 5271-SR-07-0
- 8. REFERENCES EC 2015. The Future of Zion. Webpage: http://www.exeloncorp.com/locations/power-plants/zion-station. Exelon Corporation. Chicago, Illinois.
EPA 2006. Guidance on Systematic Planning Using the Data Quality Objectives Process. EPA QA/G-4.
U.S. Environmental Protection Agency. Washington, D.C. February.
NRC 2000. Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM). NUREG-1575; Revision 1. U.S. Nuclear Regulatory Commission. Washington, D.C. August.
NRC 2018. Letter from J.B. Hickman, USNRC, to J. Sauger, Energy Solutions, RE: Zion Nuclear Power Station, Units 1 and 2 - Issuance of Amendments 191 and 178 for the Licenses to Approve the License Termination Plan.
September 28.
NRC 2019. E-mail communication between R. Edwards, NRC and N. Altic, ORISE. RE: Zion SU Map. April 9.
ORAU 2014. ORAU Radiation Protection Manual. Oak Ridge Associated Universities. 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 Health and Safety Manual. Oak Ridge Associated Universities. Oak Ridge, Tennessee. January.
ORAU 2019a. ORAU Environmental Services and Radiation Training Quality Program Manual. Oak Ridge Associated Universities. Oak Ridge, Tennessee. April 30.
ORAU 2019b. ORAU Radiological and Environmental Analytical Laboratory Procedures Manual. Oak Ridge Associated Universities. Oak Ridge, Tennessee. June 27.
ORISE 2019. Project-Specific Plan for Confirmatory Survey Activities of Subsurface Soils Associated with the Sacrificial Barrier at the Zion Nuclear Power Station, Zion, Illinois. Oak Ridge Institute for Science and Education. Oak Ridge, Tennessee. April 12.
ZS 2018. Zion Station Restoration Project License Termination Plan, Rev. 2. ZionSolutions, LLC. Chicago, Illinois. February 7.
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APPENDIX A FIGURES Zion Sacrificial Subsurface 5271-SR-07-0
Figure A.1. Gamma Walkover Survey Performed During the April 2019 Site Visit Zion Sacrificial Subsurface A-1 5271-SR-07-0
Figure A.2. Histogram of Scan Data from the April 2019 Site Visit Zion Sacrificial Subsurface A-2 5271-SR-07-0
Figure A.3. Confirmatory Soil Sampling Locations from the April 2019 Site Visit Zion Sacrificial Subsurface A-3 5271-SR-07-0
Figure A.4. Gamma Walkover Survey Performed During the July 2019 Site Visit Zion Sacrificial Subsurface A-4 5271-SR-07-0
Figure A.5. Histogram of Scan Data from the July 2019 Site Visit Zion Sacrificial Subsurface A-5 5271-SR-07-0
Figure A.6. Confirmatory Soil Sampling Locations from the July 2019 Site Visit Zion Sacrificial Subsurface A-6 5271-SR-07-0
APPENDIX B TABLES Zion Sacrificial Subsurface 5271-SR-07-0
Table B.1. Radionuclide Concentrations in Judgmental Confirmatory Soil Samples Sample Survey ROC Concentration and Uncertainty a,b (pCi/g) SOFc ID Unit Co-60 Cs-134 Cs-137 Ni-63 Sr-90 H-3 Op BC April 2019 S ite Visit 5271S0040 12104 0.018 +/- 0.025 0.016 +/- 0.026 -0.010 +/- 0.025 1.7 +/- 1.1 0.01 +/- 0.12 -1.7 +/- 1.5 0.07 0.02 5271S0041 12104 -0.009 +/- 0.022 -0.017 +/- 0.013 0.004 +/- 0.008 2.3 +/- 1.1 0.19 +/- 0.13 -0.9 +/- 1.7 0.46 0.12 5271S0042 12104 0.005 +/- 0.026 0.022 +/- 0.025 0.011 +/- 0.018 1.34 +/- 0.94 0.10 +/- 0.12 -0.6 +/- 1.2 0.27 0.07 5271S0043 12104 0.017 +/- 0.021 0.028 +/- 0.021 0.000 +/- 0.018 2.0 +/- 1.1 0.11 +/- 0.12 -0.9 +/- 1.2 0.31 0.08 5271S0044 12104 0.012 +/- 0.019 0.030 +/- 0.020 0.029 +/- 0.011 1.56 +/- 0.97 0.13 +/- 0.13 -0.5 +/- 1.0 0.37 0.09 5271S0045d 12202 3.69 +/- 0.26 -0.012 +/- 0.065 1,672 +/- 94 - - - 847 217 5271S0046 12202 0.303 +/- 0.030 0.008 +/- 0.016 6.91 +/- 0.41 3.8 +/- 1.1 0.13 +/- 0.13 -0.2 +/- 1.4 4.16 1.06 5271S0047 12105 -0.009 +/- 0.023 -0.026 +/- 0.015 -0.004 +/- 0.012 1.2 +/- 1.0 0.10 +/- 0.12 -1.0 +/- 1.2 0.24 0.06 5271S0048 12105 0.012 +/- 0.021 0.040 +/- 0.022 0.002 +/- 0.011 1.6 +/- 1.1 0.12 +/- 0.12 -1.1 +/- 1.2 0.34 0.09 5271S0049 12106 0.030 +/- 0.024 0.038 +/- 0.027 0.009 +/- 0.007 1.3 +/- 1.0 0.20 +/- 0.13 -1.4 +/- 1.2 0.55 0.14 5271S0050 12106 0.007 +/- 0.020 -0.035 +/- 0.016 0.009 +/- 0.007 1.6 +/- 1.1 0.11 +/- 0.13 -1.1 +/- 1.2 0.28 0.07 5271S0051 12107 -0.011 +/- 0.029 0.035 +/- 0.025 -0.031 +/- 0.024 1.8 +/- 1.1 0.17 +/- 0.13 -1.2 +/- 1.1 0.44 0.11 5271S0052 12107 0.006 +/- 0.025 -0.031 +/- 0.018 0.001 +/- 0.021 0.9 +/- 1.0 0.09 +/- 0.12 -0.7 +/- 1.4 0.22 0.06 5271S0053 12107 -0.013 +/- 0.024 0.010 +/- 0.016 0.007 +/- 0.019 2.4 +/- 1.1 0.15 +/- 0.13 -0.6 +/- 1.2 0.38 0.10 J uly 2019 Site Visit 5271S0055 12202D 0.062 +/- 0.018 0.015 +/- 0.019 0.099 +/- 0.019 0.46 +/- 0.43 0.10 +/- 0.11 0.6 +/- 1.6 0.37 0.10 5271S0056 12202F 0.069 +/- 0.016 -0.008 +/- 0.009 0.138 +/- 0.017 0.56 +/- 0.43 0.05 +/- 0.11 -0.4 +/- 1.7 0.27 0.07 5271S0057 10203 0.001 +/- 0.023 0.019 +/- 0.025 -0.020 +/- 0.017 - - - 0.02 0.00 5271S0058 12105 0.018 +/- 0.024 0.017 +/- 0.027 0.032 +/- 0.013 - - - 0.05 0.01 5271S0059 12106 -0.016 +/- 0.024 0.026 +/- 0.026 -0.002 +/- 0.018 0.04 +/- 0.40 0.00 +/- 0.10 -1.0 +/- 1.3 0.02 0.01 5271S0060 12105 -0.001 +/- 0.023 0.036 +/- 0.025 -0.002 +/- 0.019 - - - 0.03 0.01 5271S0061 12109 0.001 +/- 0.025 -0.043 +/- 0.018 -0.011 +/- 0.022 - - - 0.00 0.00 Zion Sacrificial Subsurface B-1 5271-SR-07-0
Table B.1. Radionuclide Concentrations in Judgmental Confirmatory Soil Samples Sample Survey ROC Concentration and Uncertainty a,b (pCi/g) SOFc ID Unit Co-60 Cs-134 Cs-137 Ni-63 Sr-90 H-3 Op BC 5271S0062 12107 -0.004 +/- 0.005 -0.033 +/- 0.018 -0.016 +/- 0.020 - - - 0.00 0.00 5271S0063 12108 -0.004 +/- 0.026 -0.023 +/- 0.014 0.043 +/- 0.014 0.05 +/- 0.42 0.11 +/- 0.11 -0.9 +/- 1.2 0.28 0.07 5271S0064 12201A 0.017 +/- 0.025 0.041 +/- 0.026 0.013 +/- 0.014 - - - 0.06 0.02 5271S0065 12201C 0.016 +/- 0.021 0.020 +/- 0.023 -0.014 +/- 0.018 - - - 0.04 0.01 5271S0066 12201C 0.009 +/- 0.015 0.015 +/- 0.016 0.008 +/- 0.009 - - - 0.03 0.01 5271S0067 12201B -0.007 +/- 0.023 -0.016 +/- 0.014 0.035 +/- 0.012 0.05 +/- 0.41 0.02 +/- 0.10 0.3 +/- 1.3 0.06 0.02 5271S0068 12201C -0.001 +/- 0.031 0.034 +/- 0.021 -0.030 +/- 0.030 - - - 0.03 0.01 5271S0069 12106 -0.003 +/- 0.007 -0.015 +/- 0.014 0.041 +/- 0.013 0.04 +/- 0.41 0.10 +/- 0.11 -0.2 +/- 1.5 0.26 0.07 5271S0070 12202A 0.016 +/- 0.016 0.014 +/- 0.015 0.034 +/- 0.011 0.07 +/- 0.40 -0.020 +/- 0.086 0.5 +/- 1.3 0.05 0.01 5271S0071 12202C -0.016 +/- 0.034 0.022 +/- 0.034 0.005 +/- 0.028 - 0.03 +/- 0.10 - 0.09 0.02 5271S0072 12202E 0.001 +/- 0.023 -0.031 +/- 0.017 -0.018 +/- 0.020 - - - 0.00 0.00 5271S0073 12202A 0.511 +/- 0.046 0.003 +/- 0.020 1.70 +/- 0.11 1.68 +/- 0.46 - 0.6 +/- 1.6 1.45 0.37 aUncertainties represent the total propagated uncertainties reported at the 95% confidence level bBolded values indicate the result was above the analytical MDC cThe SOF calculation does not include the fractional contribution from tritium dSample result is approximate Zion Sacrificial Subsurface B-2 5271-SR-07-0
APPENDIX C SURVEY AND ANALYTICAL PROCEDURES Zion Sacrificial Subsurface 5271-SR-07-0
C.1. PROJECT HEALTH AND SAFETY The Oak Ridge Institute of Science and Education (ORISE) performed all survey activities in accordance with the Oak Ridge Associated Universities (ORAU) Radiation Protection Manual, the ORAU Radiological and Environmental Survey Procedures Manual, and the ORAU Health and Safety Manual, and (ORAU 2014, ORAU 2016a, and ORAU 2016b). 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 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 the hazard 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 the National Institute of Standards and Technology (NIST).
Field survey activities were conducted in accordance with procedures from the following documents:
x ORAU Radiological and Environmental Survey Procedures Manual (ORAU 2016a) x ORAU Environmental Services and Radiation Training Quality Program Manual (currently ORAU 2019a) x ORAU Radiological and Environmental Analytical Laboratory Procedures Manual (currently ORAU 2019b)
The procedures contained in these manuals were developed to meet the requirements of U.S. Department of Energy (DOE) Order 414.1D and the NRC Quality Assurance Manual for the Office of Nuclear Material Safety and Safeguards, and contain measures to assess processes during their performance.
Quality control procedures include:
x Daily instrument background and check-source measurements to confirm that equipment Zion Sacrificial Subsurface C-1 5271-SR-07-0
operation is within acceptable statistical fluctuations x Participation in Mixed-Analyte Performance Evaluation Program and Intercomparison Testing Program laboratory quality assurance programs x Training and certification of all individuals performing procedures x 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. The sodium iodide (NaI) scintillation detectors were used solely as a qualitative means to identify elevated radiation levels in excess of background. Identifications of elevated radiation levels that could exceed the localized background were determined based on an increase in the audible signal from the indicating instrument and/or were identified after post-processing the scan data while the team was still at the site.
C.3.2 SOIL SAMPLING Soil samples (approximately 0.5 kilogram each) were collected by ORISE personnel using a clean garden trowel to transfer soil into a new sample container. The container was then labeled and security sealed in accordance with ORISE procedures. ORISE shipped samples under chain of custody to the ORISE laboratory for analysis. Where applicable, discrete particles exhibiting elevated radioactivity were isolated and containerized separately from the original sample volume prior to leaving the site.
C.4. RADIOLOGICAL ANALYSIS C.4.1 GAMMA SPECTROSCOPY Samples were analyzed as received homogenized, and/or crushed as necessary, and a dry portion sealed into an appropriate volume Marinelli beaker or container. The quantity placed in the beaker was chosen to reproduce the calibrated counting geometry. Net material weights were determined and the samples counted using intrinsic, high-purity, germanium detectors coupled to a pulse height analyzer system. Background and Compton stripping, peak search, peak identification, and Zion Sacrificial Subsurface C-2 5271-SR-07-0
concentration calculations were performed using computer capabilities inherent in the analyzer system. All total absorption peaks (TAPs) associated with the radionuclides of concern (ROCs) were reviewed for consistency of activity. Spectra also were reviewed for other identifiable TAPs. TAPs used for determining the activities of radionuclides and the typical associated minimum detectable concentrations (MDCs) for -hour count times are presented in Table C.1.
Table C.1. Typical MDCs Total Absorption Peaks Radionuclide TAP (MeV)a MDC (pCi/g)
Co-60 1.332 0.06 Cs-134 0.795 0.06 Cs-137 0.662 0.05 aMeV = mega electron volt C.4.2 NI-63 ANALYSIS Soil samples were spiked with a nickel (Ni) and cobalt carrier and digested with a mixture of nitric and hydrochloric acids. Unwanted elements, such as iron and cobalt, were then removed by running the slurry via anion exchange chromatography. Nickel was then separated from the slurry using a nickel selective resin cartridge. The purified nickel was then eluted off of the column with a dilute nitric acid solution. Ni-63 activity was then determined via liquid scintillation counting. The typical MDC for a 1-gram sample and 60-minute count time using this procedure is 1.8 picocuries per gram (pCi/g).
C.4.3 RADIOACTIVE STRONTIUM ANALYSIS Strontium-90 (Sr-90) concentrations were quantified by total sample dissolution followed by radiochemical separation and counted on a low background proportional counter. Samples were homogenized and dissolved by a combination of potassium hydrogen fluoride and pyrosulfate fusions. The fusion cakes were dissolved, and strontium was co-precipitated on lead sulfate. The sulfate-salt complex was dissolved in EDTA at a pH of 8.0. The strontium was separated from residual calcium and lead by re-precipitating strontium sulfate from EDTA at a pH of 4.0. Strontium was separated from barium by complexing the strontium in DTPA while precipitating barium as barium chromate. The strontium was ultimately converted to strontium carbonate and counted on a low-background gas proportional counter. The typical MDC for a 60-minute count time using this procedure is 0.4-0.6 pCi/g for a 1 gram sample.
Zion Sacrificial Subsurface C-3 5271-SR-07-0
C.4.4 H-3 ANALYSIS Tritium (H-3) analysis for the soil samples was performed using a material oxidizer and counted by liquid scintillation. The material oxidizer combusts samples in a stream of oxygen gas and passes the products (including CO2 and H2O vapor), through a series of catalysts. The H-3 is carried by water and is captured in a trapping scintillation cocktail specific to water. The typical MDC for H-3 for a 60-minute count time using this procedure is 3-5 pCi/g.
C.4.5 DETECTION LIMITS Detection limits, referred to as MDCs, were based on a 95% confidence level. Because of variations in background levels, measurement efficiencies, and contributions from other radionuclides in samples, the detection limits differed from sample to sample and instrument to instrument.
Zion Sacrificial Subsurface C-4 5271-SR-07-0
APPENDIX D MAJOR INSTRUMENTATION Zion Sacrificial Subsurface 5271-SR-07-0
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.
D.1. SCANNING AND MEASUREMENT INSTRUMENT/
DETECTOR COMBINATIONS D.1.1 Gamma Ludlum NaI Scintillation Detector Model 44-10, Crystal: 5.1 cm x 5.1 cm (Ludlum Measurements, Inc., Sweetwater, Texas)
Coupled to: Ludlum Ratemeter-scaler Model 2221 (Ludlum Measurements, Inc., Sweetwater, Texas)
Coupled to: Trimble Geo 7X (Trimble Navigation Limited, Sunnyvale, CA)
D.2. LABORATORY ANALYTICAL INSTRUMENTATION Low-Background Gas Proportional Counter Series 5 XLB (Canberra, Meriden, Connecticut)
Used in conjunction with:
Eclipse Software Dell Workstation (Canberra, Meriden, Connecticut)
High-Purity, Extended Range Intrinsic Detector CANBERRA/Tennelec Model No: ERVDS30-25195 Canberra Lynx Multichannel Analyzer Canberra Gamma-Apex Software (Canberra, Meriden, Connecticut)
Used in conjunction with:
Lead Shield Model G-11 (Nuclear Lead, Oak Ridge, Tennessee) and Dell Workstation (Canberra, Meriden, Connecticut)
High-Purity, Intrinsic Detector EG&G ORTEC Model No. GMX-45200-5 Canberra Lynx Multichannel Analyzer Canberra Gamma-Apex Software (Canberra, Meriden, Connecticut)
Used in conjunction with:
Lead Shield Model G-11 (Nuclear Lead, Oak Ridge, Tennessee) and Dell Workstation (Canberra, Meriden, Connecticut)
Zion Sacrificial Subsurface D-1 5271-SR-07-0
High-Purity, Intrinsic Detector EG&G ORTEC Model No. GMX-30P4 Canberra Lynx Multichannel Analyzer Canberra Gamma-Apex Software (Canberra, Meriden, Connecticut)
Used in conjunction with:
Lead Shield Model G-11 (Nuclear Lead, Oak Ridge, Tennessee) and Dell Workstation (Canberra, Meriden, Connecticut)
High-Purity, Intrinsic Detector EG&G ORTEC Model No. CDG-SV-76/GEM-MX5970-S Canberra Lynx Multichannel Analyzer Canberra Gamma-Apex Software (Canberra, Meriden, Connecticut)
Used in conjunction with:
Lead Shield Model G-11 (Nuclear Lead, Oak Ridge, Tennessee) and Dell Workstation (Canberra, Meriden, Connecticut)
Liquid Scintillation Counter Perkin Elmer Tricarb 5110TR (Perkin Elmer, Waltham, Massachusetts)
Zion Sacrificial Subsurface D-2 5271-SR-07-0