ML22089A098
| ML22089A098 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 03/28/2022 |
| From: | Van Noordennen G ZionSolutions |
| To: | Document Control Desk, Office of Nuclear Material Safety and Safeguards |
| References | |
| ZS-2022-010 | |
| Download: ML22089A098 (100) | |
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March 28, 2022 ZS-2022-010 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Zion Nuclear Power Station, Units 1 and 2 Facility Operating License Nos. DPR-39 and DPR-48 NRC Docket Nos. 50-295 and 50-304
Subject:
Revised Response to Request for Additional Information Related to Partial Site Release and Recent Site Survey Activities
References:
- 1) Marlayna V. Doell, U.S. Nuc lear Regulatory Commission, Letter to John Sauger, ZionSolutions, "Zion Nuclear Power Station Units 1 and 2 - Request for Additional Information Related to Partial Site Release and Recent Site Survey Activities,"
dated August 19, 2021
- 2) Kim A. Conway, U.S. Nuclear Regu latory Commission, Letter to John Sauger, ZionSolutions, "Zion N uclear Power Station Units 1 and 2 - Request for Additional Information Related to Partial Site Release and Recent Site Survey Activities,"
dated October 14, 2021
- 3) Gerard van Noordennen, ZionSolutions, Letter to U.S . Nuclear Regulatory Commission, "Response to Request for Additional Information Related to Partial Site Release and Recent Site Survey Activities, and Notification of Foundation Pad Discovery," dated March 8, 2022 ZionSolutions received Requests for Additional Information (RAJs), related to the partial site release request and site survey activities, on August 19, 2021 (Reference 1) and October 14, 2021 (Reference 2) . On March 8, 2022, ZionSolutions provided responses to the RAls (References 1 and 2) as documented in Reference 3.
In reviewing post-processing survey data, ZionSolutions identified that a conservative calculation of the minimum detectable activity for the investigation areas was made. Therefore, the responses to the RAls provided in Reference 3 have been revised to reflect the net count rate of the towed-array versus the gross count rate. This revision reflects a more realistic and lower discrete radioactivity particle activity sensitivity for identifying an area for investigation using post-processing methods for the towed-array surveys.
The purpose of this letter is to provide the revised responses to the RAls related to the partial site release request and site survey activities; the revised responses replace the previous responses, provided in Reference 3, in their entirety. The revised responses to the RAls are provided in the attachment to this letter. A revision bar is used to show where RAJ responses were revised .
101 Shiloh Boulevard , Zion
- IL 60099 (224) 789-4016
- Fax: (224) 789-4008
- www.zionsolutionscompany .com
ZionSolutions , LLC ZS-2022-0 10 Page 2 of3 If yo u shou ld have any question s regarding this submittal, please contact me at (860) 462-9707 .
Respectfully, Digita lly signed by Gerard van Noord ennen Gerard van ON: cn=Gerard van Noordennen, o= EnergySolutions, ou = Regulatory Affairs, Noordennen email=gpvannoordennen@energysolutions.com , c=US Date: 2022.03.28 12:32:02 -04'00' Gerard va n Noordennen Senior Vice President Regu latory Affairs
Attachment:
Revised Respon se to Request for Add itional Information Related to Partial Site Release and Recent Site Survey Activities cc: Kim Conway, U.S. NRC Senior Project Manager Regional Administrator, U.S. NRC, Region Ill Zion Nuclear Power Station, Units 1 and 2 Service List
Zion Nuclear Power Station, Units 1 and 2 Service List cc:
Ken Robuck Steven A. Reynolds President and CEO Manager, Nuclear Faci lity In spection EnergySolutions Division of Nuclear Safety 299 South Main Street, Suite 1700 Illinois Emergency Management Agency Sa lt Lake City, UT 8411 I 245 W. Roosevelt Road, Units 55 & 56 West Chicago, Illinois 60185 John Sauger President and Chief Nuclear Officer Kelly F. Grahn Reactor D&D Senior Health Physicist Energy Solutions Illinois Emergency Management Agency 121 W. Trade Street, Suite 2700 Division of Nuclear Safety Charlotte, NC 28202 245 W Roosevelt Road, Building 8, Suite 55 West Chicago, IL 60185 Todd Eiler Project Director Dan Eder D&D Engineering/Projects MPH, IPEM, LEHP EnergySolutions Interim Manager 121 W. Trade Street, Suite 2700 Lake County Emergency Management Agency Charlotte, NC 28202 1303 N. Milwaukee Avenue Libertyville, IL 60048-1308 Gerard van Noordennen Senior VP Regulatory Affairs EnergySolutions 121 W. Trade Street, Suite 2700 Charlotte, NC 28202 Russ Workman General Counsel Energy Solutions 299 South Main Street, Suite 1700 Salt Lake City, UT 84111
ZionSolutions ZS-2022-010 Attachment Zion Nuclear Power Station, Units 1 and 2 Revised Response to Request for Additional Information Related to Partial Site Release and Recent Site Survey Activities
ZionSolutions, LLC ZS-2022-0 l 0 Attachment Zion Nuclear Power Station, Units 1 and 2 - Request for Additional Information Related to Partial Site Release and Recent Site Survey Activities, dated August 19, 2021 , and October 14, 2021 REQUEST FOR ADDITIONAL INFORMATION:
The NRC staff is reviewing the Zion FSSR and the associated partial site release request to ensure that the proposed removal of 128 survey units from the ZNPS IO CFR Part 50 licenses demonstrates the ability of the site to meet the criteria for unrestricted release contained in Subpart E of IO CFR Part 20. The NRC staff has reviewed the FSSR submittals and supplements provided to date, as well as the results from the April 2021 inspection survey, and determined that additional information related to current radiological conditions at the site is needed to complete its review, as described in the following RAls. The information gathered in response to these RAis will be used, in part, by the NRC staff to perform additional risk assessments and/or dose calculations to obtain reasonable assurance that the Zion site meets the assumptions outlined in the Zion LTP and may be released from the ZNPS IO CFR Part 50 licenses without undue risk to public health and safety, or impact on the environment.
ZIONSOL UTIONS OVERVIEW ZionSolutions understands that the NRC staff is seeking additional information regarding the origin , release, and transport of discrete radioactive particles (DRPs) that have been di scovered at the Zion site. We further understand that NRC is seeking confirmation that work at the site was performed in accord ance with the Zion License Termination Plan (LTP). This information is important in ord er for the staff to have confidence that the site may be released from the Zion Nuclear Power Station (ZNPS) IO CFR Part 50 licenses w ithout undue risk to public health and safety, or impact on the environment.
ZionSolutions believes that the issues raised in the RAis can be summarized as fo llows:
- What is the origin of the DRPs at the Zion site and how did they get where they are?
- Was the work at the site conducted in accordance with the L TP?
- How can ZionSolutions and the NRC be confident that there are not DRPs remaining at the site that pose an unacceptably high risk to a future occupant?
In the fo llowing pages, ZionSolutions provi des answers to each of the RAis that address these questions. We believe that the tota lity of this information is adequate to justify unrestricted Page 1 of 96
ZionSolutions , LLC ZS-2022-01 0 Attachment release of the site. In this overview, we have summarized the key issues and the justification for our conclusions.
Origin and Transport of DRPs. The DRPs that were detected and remediated during FSS and ORJSE independent verification surveys come from a variety of so urces . While we cannot prec isely identify their so urce or the pathway to the location at which they were di scovered, we can infer both from the radioisotopic content, type of particle, and our understanding of activities at the site. Thi s informa ti on is usefu l in order to bound the scope of the problem ; however, it is important to recognize that these deta ils are not adequate to absolutel y confirm that no DRPs wi ll remain on-site. As exp lained below, w ith the add itional survey and sampling measures that have been implemented by Z ionSolutions, we believe there is reasonable assurance that there will be no DRPs posing an unacceptably high ri sk rema ining on-site.
Adequacy of FSS and DRPs . The FSS methodology is designed consistent with NRC guidance and industry best practice to detect di stributed activity that exceeds the derived concentrati on guideline levels (DCGLs) so that these areas may be remed iated . It is not desi gned specifi ca ll y to be sensitive for the detection ofDRPs. This notwithstanding, 19 DRPs were detected during FSS. That all DRPs were not detected is not an indication that the FSS was not adequate to perform its intended function . Neither is it an indication that FSS was not executed properly.
Z ionSolutions has designed and impl emented an additional survey plan to detect and remediate DRPs. The data quality obj ectives (DQOs) of thi s survey and the equipment used supplement the FSS and provide confidence that any remaining DRPs that would pose an unacceptably high risk have been identified and remediated.
Work in accordance with the LTP. Z ionSolutions has conducted the decommissioning of the ZNPS in accordance with the requirements an d commitments contained in the LTP. The execution of certain portions of this work (e.g., timing, source and depth of fi II , classification of survey units, identification of radionuclides of concern (ROC), and dose calculations) has come into question due to the identification of DRPs. As descri bed below, we are confident and have provided evidence that the work was done in accordance with the L TP. Z ionSolutions has considered if the LTP should have been modified in response to the detection of and calculation of dose from DRPs, and if so, whether the advance approval of the NRC is required . We have concluded that revi sions to Chapters 5 and 6 are necessary, and we are preparing and will submit a li cense amendment request (LAR) for NRC approval.
The DRP Survey Plan. ZionSolutions has designed and implemented a survey plan, " Survey Plan for Discrete Radioactive Particle Identification and Remediation," ZS-LT-07, Revision 1 (the "DRP Survey Plan"), 1 specifically for the purpose of detecting and removing DRPs. The 1
ZionSolutions ZS-LT-07, " Survey Plan for Discrete Radioactive Particle Identification and Remediation" Revision I , Decem her 202 1.
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ZionSolutions, LLC ZS-2022-01 0 Attachment DRP Survey Plan is included as part of the Z ionSolutions response to RAl-10 . Following th e executi on of the DRP Survey Pl an, there will be no kn own DRPs remaining on th e Z ion site.
Based on th e compl etion of th e survey and in vesti gati ons, an estimate of th e number and activity of DRPs that may hypoth eti call y remain has been made and the dose and ri sk from the hypothetica l DRPs have been estim ated. Any DRPs th at do remain wi ll not conta in sufficient activity to pose an unaccepta ble risk to a future occupant of the site.
Presence of DRPs at the Zion Site. Despi te the extensive work to detect and remed iate DRPs, the prospect of DRPs hypothetically remaining on th e Z ion site cannot be di smissed. Consistent with NRC guidance in NUREG-1757, Z ionSolutions has used a risk-based approach as described below to assess th e ri sk of dose from a DRP that may hypoth eti ca ll y be left on th e site. The p roposed change w iII be incorporated into th e L TP by Iicense amendment and will supplement how Z ionSo lutions demonstrates compli ance w ith th e dose criteria for unrestri cted re lease in Subpart E of 10 CFR Part 20. Based on our pro babili ty analysis, it is our estimation that as many as 3 1 DRPs co uld hypotheticall y remain on the site. We are confident based upon our implementation of additi onal survey and sampling measures that no DRPs that could deliver a signi ficant dose to a member of the public, including a future occupant, remain at the site. The analyses to document and justify this conclusion are described in detai l in our response to RAI-10.
Our detailed responses to each of the NRC questi ons enumerated in the RAis dated August 19, 2021 , and October 14, 202 1, are given below. These responses justify our conclusion that the ZNPS 10 CFR Part 50 licenses can be termin ated without undu e ri sk to public health and safety, or impact on the environment.
NRC RAI-la:
For each particle or sample identified during the April 2021 inspection survey and described above, please explain to the extent possible: The likely origin of the particle or material identified in the sample (e.g., activated metal, bioshield concrete, irradiated fuel fragments, etc.)
from decommissioning operations, including the hypothetical radionuclide mix for each type of particle based on the reactor operational history of both (e.g. , fuel bum up and activation).
ZIONSOLUTIONS RESPONSE:
Whil e the specific ori gin fo r each particle is unkn own, Z ionSolutions has postul ated th e most likely ori gin for each particle based primarily upon th e radionuclide profile of each. As discussed in th e February 10, 202 1, response to RAI-11 b, th e I ikely ori gin of the maj ority of particles fo und in site soil are from reactor vessel inte rnals (RVI) segmentation. Based upon the radi onuclide profil e of particles discovered by th e Oak Ridge Institute fo r Sci ence and Education Page 3 of 96
ZionSolutions, LLC ZS-2022-0 10 Attachment (ORISE) during the April 2021 inspection survey (as documented in fi nal report 5271-SR-09-02) ,
ZionSolutions believes that the additional particles originated from fue l fragments, intern al containment concrete (originating from under vessel or the bioshield), or we lding rod resid ue.
The interna l containment concrete was likely introdu ced into the soil during waste handli ng operations. The postu lated origi n and hypothetica l radionuc li de mix for each particle is shown below in Table 1.
Table 1 - Particle Origins and Hypothetical Radionuclides Sample Likely Origin Hypothetical Radionuclides S0112A RVI segmentation Co-60 S0116 RVI segmentation Co-60 Co-60, Ba-133, Eu- 152, Eu-1 54, Pu-S0 120 Internal contai nment concrete 238, Pu-239/240 S0124 RVI segmentation Co-60 Co-60, Cs-137, Eu-154, Eu-1 55, Am-S0126 Fuel fragment 24 1, Cm-244, Pu-238, Pu-239/240 Co-60, Ba-133 , Eu-15 2, Eu-154, Pu-S204AEu Internal containment concrete 238, Pu-239/240 Ra-228, Th-228, Th-230, Th-232, U-S203B Welding rod resi due 234, U-238 Ra-228, Th-228, Th-230, Th-232, U-527 1-S-203A Th Welding rod resi du e 234, U-238 NRC RAI-lb:
For each particle or sample identified during the April 2021 inspection survey and described above, please explain to the extent possible: The size range of particles expected to be produced by decommissioning operations for the three types of particles identified (i.e. , Co-60 metal, possible activated biosh ield concrete, possible activated fuel fragm ent). Specifically, for the types of cutting operations above and below water and demolition activities that were performed at Zion, the range of expected particle sizes should be identified, along with technical references for the expected size range where available.
2 "Independent Confirmatory Survey Summary and Results Assessing the Presence of Residual Radioactivity and Radioactive Particles within Select Land Area at the Zion Nuclear Power Station, Zion, Illinois," Oak Ridge Institute for Science and Education , Report No. 5271 -SR-09-0, September 3, 2021 .
Page 4 of 96
ZionSolutions, LLC ZS-2022-010 Attachment ZIONSOLUTIONS RESPONSE:
Co-60 Metal Particle Size. For the decommi ssioning of Zion, a mechanical complex tool system for underwater RVI segmentation was used . During the mockup testing of this system for Z ion, particl es produced were approximately l mm in diameter and less than l mm thick, as di sc ussed in th e February 10, 2021, response to RAI-11 b. Accordin g to th e EPRI Report, "Characteri zation and Management of Cutting Debri s During Plant Di smantlement," mechanica l techniques fo r RVI segmentati on produce debri s in th e 2 mm to 6 mm ran ge, with no airborne debri s. 3 Fuel Particle Size. The fuel particle mass was estimated using the activity and the specific acti vity (Bq/kg) of Pu-23 9 in sample S01 26 (shown in Figure 1), as documented in the ORISE report 5271-SR-09-0.
Figure 1 - NRC Radiological Toolbox Specific Activity for Pu-239
~ Summ.,y Tablt for Pu*l.39 X Summary Decay Data Table for Pu-239 H -Lde 2 41 IE*4 V Specific ActMly 2 295E* 12 Bq I kg Mode 4 Source ICRP-07 NOX Frequency Energy Mean Energy I:YI IYi
- El I:YI
- El I I:YI Radjation Number Ital) (MtY!oll (Mey)
Gamma rays 207 9 758E-04 6 399E*OS 6 658E-02 X rays 74 3 042Ect00 1 014E-03 3 335E-04 IC electrons 1016 3 045!:-0 1 S 829-03 1915E-02 Augtr electrons 15 2 590E+OO 1 625E-03 6 276E-04 Alpha particles 52 I OOOE+OO 5148E+OO 5 148E+OO Alpha RecOII Nuclei 52 1 OOOE*OO ~ 8 768E-02 Totll Emitted Energy 5 244E+OO Not a Yi = 1111ensity of radJation I El = tn rgy ol radiaoon ,
II Pin II OK The Pu-239 specific activities in GBq/g, Bq/g, and pCi/g are shown in Table 2.
3 "Characterization and Management of Cutting Debris During Plant Dismantl ement," The Electric Power Research Institute, July 28, 2015 .
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ZionSolutions, LLC ZS-2022-0 I 0 Attachment Table 2 - Pu-239 Specific Activity in various Units Specific Unit Activity 2.30E+00 GBq/g 2.30E+09 Bq/g 6.20E+ l0 pCi/g The mass of the Pu-239 in the particle can be estimated from the reported activities in 5271-SR-09-0 by dividing the activ ity in GBq/g by the specific activity in GBq/g in Table 2. The estimated Pu-239 mass of the particle is shown in Table 3.
Equation 1 - Calculation of Particle SOI 26 Pu-239 Mass Apu-239 X 3.70£-11 GBq/pCi MPu- 239 = SAPu-239 x 1000 g/kg where MPu-239 = the mass Pu-239 in the S0 126 particle APu-239 = the activity of Pu-239 in pCi SAPu-239 = the specific activity of Pu-239 from Figure l in Bq/kg
- 3. 70E-11 = the conversion factor for pCi to giga Becquerel where 1 pCi = l .00E-12 Ci and 3.70E+ 10 Bq = 1 Ci and l GBq = l.00E+09 Bq .
Table 3 - Estimated Pu-239 Particle Mass of Particle SOI 26 Activity Activity Mass Radionuclide (pCi) (GBq) (g)
Pu-239 7.74E+03 2.7898E-07 l.22E-07 According to the World Nuclear Organization4, as seen in Figure 2 below, approximately 5 kg of Pu-239 are contained in one tonne (1 ,000 kg) of spent fuel in a power reactor at discharge (approximately 2 years).
4 Plutonium in the Reactor Core, World Nuclear Organization Plutonium Webpage.
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment Figure 2 - Plutonium in the Reactor Core, World Nuclear Organization Plutonium Webpage Plutonium in the reactor core 6
5
,i!
0 j 3 i - - - --#-- + - - - - - - - - - - - 1 i
- l. 2
~
1 0
1 2 3 Yea nf or Equation 2 - Fractional Mass Pu-239 per Mass of Spent Fuel 5 kg x 1000 g/kg FPu-23 9 = 1000 kg x 1000 g/kg = 0.005 g Pu-239 per g spent fuel where F Pu-239 = Fractional mass of Pu-239 per mass of spent fuel Therefore, the mass of Pu-239 in particle S0126 (l.22E-07 g) is equivalent to 2.43E-05 g of spent fuel as follows.
Equation 3 - Mass of Spent Fuel Based on Mass of Pu-239 1.22£-07 g Pu-239 Msp = g = 2.43£-05 g SF 0.005 Pu-239 SF g Spent fuel contains 941 kg/tonne of U-23 8 or 0.941 gram U-23 8 per gram of spent fuel. 5 Based on this, the U-238 or uranium oxide mass is shown in Equation 4 as 2.29E-05 gram .
Equation 4 - Mass of Uranium Dioxide based on U-238 Mass and Fraction of U-238 per gram of Spent Fuel U-238 g Mu = 0.941 - - - x 2.43£-05 g SF= 2.29£-05 g SFg Converting the U-238 mass to volume using a uranium dioxide density of 10.97 g/cm 3 estimates a particle volume of 2.09E-06 cm 3 using Equation 5.
5 From Radioactivity.EU. com Page 7 of 96
ZionSolutions, LLC ZS-2022-010 Attachment Equation 5 - Volume of Uranium Oxide in Particle S0126 Based on Mass of U-238 and Density of Uranium Dioxide
_ 2.29£ - 05g _
Vu 0 2 - - 2.09£ - 06 cm 3 10.97-3 9 cm Using Equation 6, the diameter of a spherica l partic le of that volume is 159 µm.
Equation 6 - Particle Diameter Based on Spherical Volume 4
V = -rrr 3 3
D =2 x V
)1/J = 1.59£-0 2 cm X 10,000 -
µm
= 159 µm (3 cm
/4 rr where D = diameter of the uranium oxide particle in cm 2 = double the radius length to that of the diameter V= 2.09E-06 cm 3 volume of the uranium oxide sphere Activated Concrete Size. ZionSolutions is unable to estimate a size for a DRP consisting of activated concrete. DRPs of this nature were first identified by ORISE in the April 2021 inspection survey, and particle sizes were not presented in their final report, 5271 -SR-09-0.
Concrete demolition debris on-site was required to be reduced to a size smaller than 10 inches in diameter before it was packaged and shipped off-site or reused as backfill. As such, residual activated concrete discovered on-s ite would be expected to be smaller than 10 inches in diameter. A particle would clearly be much smaller, but we have no data to postulate a specific size range .
DRP Size Change over Time. It is important to recognize that these projected particle sizes may change due to weathering and other environmental influences over the 1,000-year compliance period. These particle size changes wi ll affect the potential dose to a future occupant.
ZionSolutions accounted for particle size changes in order to develop dose estimates in response to RAI-10. Our analys is of how particles may change in size and the resu lting dose estimates is described in the response to RAI-10, Specific Consideration 3b.
NRC RAI-lc:
For each particle or sample identified during the April 2021 inspection survey and described above, please explain to the extent possible: A description of how the particle or material transported from the contamination source to where it was found during the April 2021 inspection survey, as well as the potential timing or time range of when the particle was transported to that location.
Page 8 of96
ZionSolutions, LLC ZS-2022-0 10 Attachment From p. 12 of the RAl letter: "The licensee should attempt to determine the origin of this contamination, or provide reasonable assumptions regarding the potential origin of this
[enhanced thorium] material." And" ... the licensee should state whether the thorium material is likely a result of decommissioning operations, such as cutting or welding metal components; whether it was inadvertently imported ... "
ZIONSOLUTIONS RESPONSE:
ZionSolutions believes that partic les were introduced to the environment via the fol lowing events:
- 1. Partic les in the form of shavings from RVl segmentation were likely introduced into the soi l via the transportation of the 8-120 liners loaded with RVI segments. The origi nal incident in 2014 started when an 8-120 liner was transported from the south array storage area to the parki ng area to the north of the old NGET build ing. It is believed that the contents of the liner dried out. When Radiation Protection was surveying the vehicle for exit of the site, elevated read ings were encountered and a DRP was captured. At this time, the exit to the site was closed for all vehicles and personnel , and FSS personnel were brought in, along with 2" x 2" sodi um iodide (Nal) detectors, to help locate and capture other potential DRPs from this event. These scan surveys covered the so uth-north trave l route and extended east-west as necessary to ens ure that all particles were captured.
Personnel exiting the site had to perform a hand and foot frisk prior to entering the portal monitors. These mitigating measures that were immediately implemented after the event limited the spread of contamination to other areas of the site. While ZionSolutions believes that these measures were useful in limiting contamination, this event likely is responsible for the majority of the DRPs identified on-site.
- 2. Partic les in the form of fue l fragments or metal , entered the soi l via a lack of negative pressure and the movement of potentially contaminated equipment and large components through the equipment hatches of each Containment Building prior to the erection of the waste loadout tents. This source term origin was mitigated once the waste loadout tents were erected in early 2017.
- 3. Particles in the form of concrete material associated with interna l containment generated during demolition were likely introduced into the soi l during waste handling operations.
ZionSolutions believes waste handling operations to be the source of contamination based on the location and radionuc lide contents of the particles identified by ORISE during the Apri l 2021 inspection survey.
- 4. Particles containing thorium were likely introduced into the soil during welding activities, which frequently occurred throughout decommissioning both inside buildings and in outdoor areas. It was not uncommon to identify elevated areas of radioactivity during Page 9 of96
ZionSolutions, LLC ZS-2022-010 Attachment scan surveys of buildings and soil and identify welding rods to be the source of the elevated activ ity. While this activity was remediated when di scovered , it is possible that an indi vidual DRP escaped detecti on and remedi ation .
Z ionSolutions performed a review described in th e respo nse to RAJ-] n to determine if other events co uld ha ve introduced DRPs into the environment. Based upon th is review, Z ionSolutions does not believe that any events other th an those described above contributed to the presence of partic les or contami nated debris at the site.
The fo ll owing timeline summari zes the timing of potential releases from these events, as well as actions taken to remed iate the releases.
- 20 12 thro ugh 2014: Segmentation of reactor vesse l and reactor vesse l interna ls.
- 2012 through 2017: Containment equipment hatches expanded and open until the waste tent structures were constructed in January and February 2017.
- September 20 14: Storage outside of 8-1 20 liners containing reactor internals segments, loading of the 8-120 liner in an overpack, and transportation across the site.
- September 24 and September 25, 2014: Survey, detection of particles, and remediation of the contami nated areas (s urvey units 1022 1A, 10221B, 10221C, 10202, 10208, 10206, 10204, and 10203).
- June 3, 2015: The area north of Unit 2 Containment was established as a temporary radioactive materials area for the purpose of containing several pieces of segmented steam generator components awaiting loadout into railcars. Particles were detected in the soil north of Un it 2 containment during the down-posting survey.
- June 3 through June 11 , 2015: Survey, detection of particles, and remediation of the contaminated areas (survey units 1220 1A, 12201B, 12201 C, 12202A, 12202B, 12202C, 12202D, 12202F, 12109, and 12111).
- January and February 2017: The containment waste tent structures were erected and interior demolition of Unit 1 and Un it 2 Containment Buildings commenced.
- January 29, 2018, through March 1, 2018: Removed debris from Unit 1 under vessel.
- February 2, 2018 , through Apri l 5, 20 18 : Removed debris from Unit 2 under vessel.
Once introduced into the environment, the likely transportation pathways for particles are surface water flow (runoff during heavy rains) and/or heavy equipment and vehicle movement.
In immediate response to the events described above, and in response to the detection of DRPs at any time durin g decommissioning, biased surveys were conducted and the DRPs were successfull y remediated. While this was the case, DRPs were still intermittently detected Page 10 of 96
ZionSolutions, LLC ZS-2022-010 Attachment throughout decommissioning at different stages, durin g radiological assessments (RA), FSS, or even after FSS. The most recent example of the detection of DRPs after FSS completion is the April 2021 inspection survey conducted by ORISE, in which eight DRPs were identified .
Because the DRPs were identifi ed post-FSS and, in some cases, their radiological characteristics differed from the historical DRPs discovered at the site, ZionSo lutions designed and implemented the DRP Survey Plan to address the presence of DRPs on-site. The survey design included a 100% gam ma scan of the survey units of interest using a 6-detector (2" x 2" Nal) towed array and systematic sampling using a presence/absence design. The DRP Survey Plan is described in detail in the response to RAI-10.
NRC RAI-ld:
The most likely cause for why the particle or material was not found in licensee surveys.
ZIONSOLUTIONS RESPONSE:
The most likely cause for why particles or other materials were not identified during licensee surveys is that the DQO development process for the surveys was not designed to detect particles. Had that been the intent, different DQOs (e.g. , use of slower scan speeds) would have been implemented .
It is important to note that during active decommissioning, 255 particles were identified and remediated and another 25 particles were identified and remediated during FSS or RAs, for a total of 280 particles discovered by ZionSolutions using the standard instrumentation and survey methodologies in use at the time. So as designed, the surveys were adequate to detect the majority of particles on-site.
ZionSolutions implemented the DRP Survey Plan to provide high confidence that no particles remain on-site that cou ld deliver a significant dose to a member of the public. The survey plan included DQOs and survey methodologies that focus on DRP detection and remediation.
NRC RAI-le:
Whether these areas received an ORISE confirmatory survey in their final condition.
ZIONSOLUTIONS RESPONSE:
Survey unit 12201B did not receive a confirmatory survey during the FSS confinnatory surveys performed by ORISE in January 2020, when the survey unit was in its final condition. However, survey unit 12201B was included in the scope of the April 2021 ORISE inspection survey, but the survey was limited to a small portion of the survey unit and the intent of the survey was to identify particles, not to confirm FSS findings. Survey unit 12201 B was not impacted by final site grading.
Page 11 of 96
ZionSolutions, LLC ZS-2022-010 Attachment Survey unit 12203D did recei ve an ORISE confirmatory survey during the January 2020 site visit, as documented in the ORISE Fi na l Report 527 1-SR-08-0. 6 Survey un it 12203D was not impacted by final site grading. Si nce the ORJSE confirmatory survey in January 2020, a portion of th e survey unit was subject to investi gation durin g the Apri l 2021 inspection survey. FSS has since been reperformed in urvey unit l 2203D, and the urvey unit wa a lso within the scope of the DRP Survey Plan .
T he table below li sts th e survey units where particles were identifi ed (d urin g the entire proj ect) and w hether or not they received an FSS confirmatory survey by ORlSE.
Table 4 - Survey Units with Particles Identified that R eceived ORJSE FSS Confirmatory Survey Survey Unit FSS Confirmatory Survey Unit FSS Confirmatory 10202B Yes 12 104 No 10202D Yes 12 106 No 10203A Yes 12109 No 10203F No 12111 No 10204B No 121 12 Yes 10204D No 121 13 Yes 10206D Yes 1220 1A No 10207A Yes 12201B No 10207B No 12201C No 10207C No 12201D Yes 10209A Yes 12201E No 10209C Yes 12202A No 10209E Yes 12202B No 10214E Yes 12202C No 10214F Yes 12202D No 10220A Yes 12202F No 10220G Yes 12203A Yes 102201 Yes 12203C Yes 10221C Yes 12203D Yes 1022 1D Yes 12204A Yes 6
"Independent Confirmatory Survey Summary and Results of the Remaining Land Areas at the Z ion N uclear Power Station, Zion, Illinois ," Oak Ridge Institute for Science and Education, Report o . 527 1-SR-08-0 , April 24, 2020.
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ZionSolutions, LLC ZS-2022-010 Attachment NRC RAI-lf:
If the area received a confirmatory survey in its final condition , provide an estimate of whether the particles were present and missed during the confirmatory survey or were transported to the area after the confirmatory survey due to other site activities.
ZIONSOLUTIONS RESPONSE:
ZionSolutions is unabl e to estimate whether the parti c les were present and mi ssed dur ing the confirmatory survey or were transported to the area after the confirmatory survey due to other site activities (e.g. , personnel and veh ic le traffic). Z ionSolutions believes both scenarios to be equa lly likely.
As discussed in the response to RAI-ld, the most likely cause for why DRPs were not identified during licensee surveys is that the DQO development process for the survey was not designed to focus on the detection of DRPs.
NRC RAJ-lg:
Given the observations in the survey units listed above, as well as any additional observations resulting from ongoing licensee activities under the Final Status Survey Due Diligence Plan, provide an explanation for why the licensee surveys are adequate .
ZIONSOLUTIONS RESPONSE:
The licensee surveys were cond ucted fo llowing the process for performing FSS in accordance with the LTP, MARSSIM7 , and other regulatory guidance documents. As such, ZionSolutions believes that the surveys were conducted in accordance w ith best industry practice. The licensee surveys were designed to find unifom1ly distributed contamination and were adeq uate and successful for that purpose.
Particles are a source term, and it is ZionSolutions' intention to not leave any particles in site soil that present an unacceptabl y high risk. ZionSolutions accompli shed this by performing a 100%
surface area scan in survey units 12201B, 12203D, and 34 additi onal survey units within the scope of the DRP Survey Plan using appropriate DQOs and survey methods with sensitivity sufficient for the detection of particles. 8 7
"Multi-Agency Radiation Survey and Site Investigation Manual (MARS SIM)," NUREG- 1575 , Revision I , U.S.
uclear Regulatory Commi ssion, August 2000.
8 See Connecticut Yankee Atomic Power Co., 58 .R.C. 262 , 297-299 (2003) (find ing that Connecticut Yankee 's compliance with MARS SIM provides a sufficient plan for detecting hot particles in its L TP, with a separate opinion noting that a li censee cannot implement a detection plan until th e final site survey results are available).
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ZionSolutions, LLC ZS-2022-0 10 Attachment Within the DRP Survey Plan, ZionSolutions targeted survey units that had the potential to contain DRPs. In determining what survey units to target, Z ionSolutions selected survey units:
- where clean concrete demolition debris (CCDD) was temporarily staged or transported through after comp letion of FSS
- where waste loado ut areas resided
- with areas of elevated activity identified by ORJSE durin g th e April 2021 inspection survey
- that were adjacent to Class 1 survey units (e.g., survey units 10214, 10213 , 10212) where particles or elevated areas had been previously identified The rationale for survey uni ts not included in the DRP Survey Plan includes a combination of the fo llowing:
- Z ionSolutions assessment of the so urce and transport of the DRPs that have been identified did not give any indication that the survey unit would contain DRPs .
- DRPs were not detected in prior surveys.
- ORISE performed an FSS confirmato ry survey or other independent verificati on survey in the survey unit with no identificatio n of DRPs.
- Surveys performed during final site grading did not identify DRPs.
NRC RAI-lh:
Given that the licensee's FSS and other survey activities did not identify these particles or other radiological material, provide a discussion to support reasonable assurance that there are not similar particles in other areas at a concentration level or to an extent that might challenge the unrestricted release criterion of 10 CFR Part 20.
ZIONSOLUTIONS RESPONSE:
ZionSolutions has evaluated the likely sources and transportation pathways of particles on-site.
Based on this evaluation, survey units of medium to high risk were included in the DRP Survey Plan to undergo a 100% scan survey with instrumentation of the appropr iate sensitivity and particle-specific DQOs. Because the DRP Survey Plan was designed to identify and remediate any remaining particles on-site, it provides reasonabl e ass uran ce that DRPs that may have been mi ssed during prev ious surveys were detected and remediated and there are no particles remaining on-site to chall enge the unrestricted release criterion of 10 CFR 20. The foc us of the surveys on survey units that were most likely to contain DRPs provides reasonable ass urance that Page 14 of 96
ZionSolutions, LLC ZS-2022-010 Attachment there are no DRPs in other areas of the site. If warranted, the scope of the DRP Survey Plan was expanded as required by bounding investigations or remediation.
NRC RAI-li:
When clean fill was placed over and surrounding the basement substructures in the Zion Power Block area.
ZIONSOLUTIONS RESPONSE:
Table 5 gives the dates when clean fill was placed over and surrounding the basement structures.
A review was performed of the daily work reports for 2018 and 2019 to determine the dates for the perfom1ance of fi 11 work. Off-site material may have come from one of two so urces (li sted in the notes) and may be different types of material, but it is all clean fill.
Table 5 - Backfill Timeline Date Activity 02/21/18 Began moving AB rubble pile from rail spur loading areas to south loading area (10221).
03/28/18 Began receiving and stockpiling backfill for AB using clean, off-site material from Zion landfill. Placed on TB footprint (12205) for interim storage. TB footprint was under I&C prior to and during interim storage.
06/15/18 Began AB backfill.
07/20/18 Began backfill of Forebay using Turbine Building CCDD material.
07/23/1 8 Began U2 Containment interior backfill (dome in place) using clean, off-site material from Zion landfill.
08/02/18 Installed U2 Containment sacrificial backfill around perimeter.
08/10/18 Began backfill ofFHB using clean, off-site material from Zion landfill.
08/ 10/18 Began Unit I Containment interior backfill (dome in place) using clean, off-site material from Zion landfill.
08/27/18 Installed U 1 Containment sacrificial backfill around perimeter.
08/28/18 Began Unit 2 Containment demolition.
09/26/18 Began Unit 1 Containment demolition.
12/10/18 Began backfill of Wastewater Treatment Facility.
01 /24/19 Began moving CCDD from 12202 to 12205, 12112, 12113 02/27/19 Began removing sacrificial soil working from south to north. Placed in I 0207.
03/20/19 Began moving CCDD material to NW parking area.
04/17/19 Move of CCDD to NW parking area suspended.
06/24/19 Began moving CCDD from 12205, 12112, 12113 to west loading area ( I 0206).
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment Date Activity 07/11/19 Completed moves ofCCDD to 10206.
- - - - - - -- - - - ----------l 08/05/19 Began back fill of power block area (where the sacrificial soil was removed) to bring to final elevation. Used clean, off-site fill from Antioch quarry (Sand) otes:
- CCDD was used to fill basements up to 3 feet below grade
- Clean fill from the Zion Landfill was used as the top 3 feet layer in a basement
- Clean fill from the Antioch quarry (sand) was used to bring the power block area back to grade after the sacrificial soil was removed
- Sandstone gravel from off-site was used for roadways As noted in the last item of the timeline, the fina l cover soil (clean fill) was applied in August 2019 when basement backfills were complete. The DRPs that have been detected on the surface of the final clean fill applied to grade were likely attached to the equipment used to apply and grade the Antioch quarry sand. This equipment may have traversed the locations described in the response to RAl-lc and picked up DRPs.
NRC RAI-lj:
When final grading of the site commenced and was completed.
ZIONSOLUTJONS RESPONSE:
Final site grading of the site commenced on August 31 , 2020, and was completed on September 23 , 2020. A detailed timeline of final site gradi ng and supporting maps are included in the enclosure to this response ("Final Site Grading and Seeding Timeline with Maps").
Gamma scan surveys were performed prior to and after grading in all areas that were impacted by final site grading. Thi s includes areas where soi l was scraped , dispositioned, and w here swales were created. No areas of elevated activ ity were identified during these surveys. Based on these surveys, the potential for final site grading to spread DRPs is low. Because DRPs were not identified during final site grading, the impacted survey units were not included in the scope of the DRP Survey Plan .
NRC RAI-lk:
When final grading occurred for the area where concrete debris was stored.
ZIONSOLUTIONS RESPONSE:
As detailed in "Final Site Grading and Seeding Timeline with Maps" (provided in the enclosure to this response), grading occurred in survey units where concrete debris was stored on September7, 9, 11 , 14, 15, 16, 17, 18, 21 , and22of2020.
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ZionSolutions, LLC ZS-2022-010 Attachment NRC RAI-11:
When the final cover of seed bed (i .e., grass) on the final site grade was placed.
ZIONSOLUTJONS RESPONSE:
Seeding began on September 11 , 2020, and was completed on October 2, 2020.
NRC RAI-lm:
When ZNPS waste handling activities occurred in each of the locations where the particles and radiological material "chunks" were found (south of the railroad track, south of the Auxiliary Building, southeastern portion of the site near the beach , etc.).
ZIONSOLUTIONS RESPONSE:
For each of the locations where particles and radiological materials were found , waste handling activities occurred throughout most of the decommissi oning, with the first waste handling activities beginning in 2014, as described in the response to RAI-lc. However, interior containment concrete was not potentially introduced into the environment until January and February 2017, when the Unit 1 and Unit 2 tent structures were completed and interior demolition of the buildings commenced.
NRC RAI-ln:
Timing of any other operational events that could explain the origin or presence of the particles and radiological material "chunks" of contaminated debris at the site.
ZIONSOLUTIONS RESPONSE:
ZionSolutions has the reviewed the operational and decommissioning history of Zion to determine if any other events (other than the events described in the responses to RAI-la and RAI-lc) cou ld explain the origin or presence of particles or radiological material at the site.
ZionSolutions reviewed condition reports that were written to assess the prospect that the events could have been a source of particles or contaminated debris. Based upon this review, ZionSolutions does not believe that any events other than those described in the responses to RAI-1 a and RAI-1 c contributed to the presence of particles or contaminated debris at the site.
For example, on March 8, 2017, the Unit 2 Containment waste loadout tent sustained rips due to high winds. According to the condition report (ES-ZION-CR-2017-0038, included in the enclosure to this response), little, if any, radioactive material was within the tent at the time of the breach. For this reason, ZionSolutions does not consider this event as a contributor to the release of particles or material chunks to the environment. Prior to this, all handling of interior containment concrete occurred with in the Unit 1 and Unit 2 tents under controlled conditions.
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment NRC RAI-2a:
Please explain the process the licensee underwent to determine whether or not the information available since approva l of the Zion L TP has triggered an evaluation of the L TP change criteria.
Information potentially impacting the Zion LTP licensing basis is included in : an RAJ response submitted in February 202 1 (draft fo rm in November 2020) related to dose from potential radioactive particles left on the Z ion site, the April 2021 inspection survey results, and the Zion Final Status Survey Due Diligence Plan.
ZIONSOL UTIONS RESPONSE:
During the performance of decommi ssioning activiti es, all empl oyees have been tra ined and are responsible for executing work in conformance with the LTP. It is the responsi bility of the C/L T Manager to ensure that work is conducted in compli ance w ith the LTP . Tf any activ ity is identified as potentia lly incons istent with the LTP, it is the responsi bility of the C/LT Manager to conduct a rev iew and determ ine if a change to the L TP is or is not requ ired.
Once it has been determined that a ZNPS activ ity requi res a change to the LTP, AD-1 1, "Regul atory Reviews," is used to perform an LTP evaluation. The L TP evaluation is requi red, for all LTP rev isions, to address the license criteria in License Condition 2.C.(1 7). In addition to th e LTP evaluation, the acti vity is required to be rev iewed under 10 CFR 50.59. AD-11 prov ides guidance for the 50.59 rev iew as well.
There are 13 li cense change criteria in Attachment E-1 of AD-1 1 (the same cond itions that are listed in ZNPS License Condition 2.C.(17)). These cri teri a apply once it has been determined that a change to the LTP is necessary. As such, they are not considered in the assessment of whether or not to make a change to the L TP. ZionSolutions does not believe that there has been any information generated that wo uld necessitate a change to the L TP change criteri a.
In response to this RAI, Z ionSolutions has performed a review of the response to Supplemental NRC RAI Question No. 11 , submitted in February 2021 , the April 2021 inspecti on survey results, and the results of subsequ ent site surveys performed by Z ionSolutions si nce the April 2021 inspection survey in order to identify activities that may have triggered a change to the LTP. In prepari ng thi s response, ZionSolutions examined the fo llowing activities:
- 1. Detection of radi onuclides defined as "insignificant"
- 2. Revised survey unit class ificati on due to DRP detection
- 3. Detection of DRPs and the potential dose consequences In so do ing, ZionSolutions rev iewed the in itial determin at ions that none of th ese activities required a change to th e L TP . U pan fu rther rev iew, Z ionSolutions has reaffirmed that the first two activ ities listed above di d not requi re a change to the LTP ; however, th e th ird activity, the Page 18 of 96
ZionSolutions, LLC ZS-2022-010 Attachment detection ofDRPs, was found to require a change to the LTP. Detailed findings and the proposed changes to the L TP are described be low.
Results of the Activity Review
- 1. Activities that do not require a change to the LTP The first two activities identified above do not require changes to the L TP as described below. As those activities did not result in a change to the L TP, an L TP eva luation, to address the 13 criteria in ZNPS License Conditi on 2.C.(17), was not required. Those criteria apply when a ZNPS activity resu lts in a change to the LTP. The criteria are used to determine if the changes to the L TP require prior NRC approval.
A. Detection of Radionuclides Defined as Ins ignificant ZionSolutions performed a review of the preliminary results of the April 2021 inspection survey to determine if a revision to L TP Table 5-2 was necessary.
Specifically, ZionSolutions evaluated the need to include radionuclid es that previously had been defined as " insignificant" in the table. Section 5. J of the L TP states that for all samples anal yzed for the fu ll su ite ofradionuclides (LTP Table 5-1),
the actual insignificant contributor (IC) dose wi ll be calculated for each individual sample result. If the IC dose calculated is less than the IC dose ass igned for D CGL adjustment (2.5 mrem/yr for soils), then no further act ion wi ll be taken. If the IC dose exceeds 10 percent, then the additional radionuclides that were the cause of the IC dose exceedin g 10 percent w ill be added as additiona l ROC for that survey unit.
For all soi l samples analyzed for the full suite ofradi onuclides, the IC dose was less than 10 percent; therefore, the positive identifications of Am-241 , Pu-238/239, orNp-237 remained insignificant to the dose contribution. As described in the response to RAI-6a, the hard-to-detect (HTD) radionuclides identified in the samples do not change the ROC list for di stributed radioactivity. However, a LAR will be submi tted for NRC review and approva l to revise Chapter 6 of the LTP to include DRP ROCs.
The original ROC list (for distributed radioactivity) for the Zion site does not need to be changed .
B. Revised Survey Unit Classification due to DRP Detection If a DRP was identified in a survey unit, the survey uni t classification was changed, as necessary. A revision to a survey unit classification would not require a change to the LTP unless the survey un it was reclassified to a less restrictive classification.
During decommissioning, most DRPs were fou nd in C lass l survey units and therefore, no changes to the classifications were necessary. In som e cases, DRPs were identified in Class 3 survey uni ts (e.g. , survey unit 10214) ; portions of those survey units were reclassified as Class 1. As Z ionSolutions has not revised a classification to a less restrictive designation, no changes to the L TP are necessary.
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ZionSolutions, LLC ZS-2022-010 Attachment
- 2. Activity that requires a change to the LTP ZionSolutions originally concluded that the detection of DRPs did not require a revi sion to the LTP. However, upon further consideration, ZionSolutions has concluded that a change to the L TP is necessary to describe the process for detecting and calculating the dose from DRPs. The process for calculating the dose from DRPs is fundamentally different from calculating the dose usin g DCGLs to demonstrate compliance.
Detection of DRPs and the Potential Dose Consequences ZionSolutions initially determined that a change to the LTP due to the identification of DRPs and the potential dose consequences of the DRPs was not required because DRPs are a separate so urce term that is removed from the site upon detection. As such, th ere wo uld be no res idual DRP radioacti vity to be eva luated in the LTP (i.e., no pathway for dose needed to be modeled and there was no need to revise DCGLs). 1n that regard, finding a DRP is no different than finding a soil sample with concentrations in excess of the Base Case DCGL. In both in stances, Section 5.2. 14 of the LTP requires the material to be remediated . Each time a DRP was discovered , the DRP was removed from the survey unit. Therefore, no change to the DCGLs was required and no change to the methodology for calculating dose was required.
L TP, Chapter 5 Upon further consideration, ZionSolutions has conc luded that because the survey methodology of the DRP Survey Plan to detect DRPs is different from the survey techniques described in the L TP, a revision to the L TP is necessary. ZionSolutions proposes to revise the L TP by incorporating a new section into Chapter 5 entitled, "Survey Considerations for Suspected Discrete Radioactive Particle Areas ." The new section will discuss the definition of a DRP and the need for special survey techniques and actions to be used specifically for the detection of DRPs.
ZionSolutions will submit the revi sed L TP Chapter 5 with a LAR to the NRC.
LTP, Chapter 6 Because it is hypothetically possible that DRPs could be left at the site, and because the dose for DRPs is calculated differentl y than the dose calculated to demonstrate compliance using DCGLs, a change to Chapter 6 is necessary.
ZionSolutions will demonstrate compliance with the dose criteria in Part 20 Appendix E.
The proposed change will supplement how ZionSolutions demonstrates compliance with the dose criteria by also considering the risk of dose from a DRP that may hypothetically be left on the site. This risk-based approach is in accordance w ith the guidance contained in NUREG-1757.
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ZionSolufions, LLC ZS-2022-0 I 0 Attachment The DRP exposure scenario will be evaluated as a less likel y but plau sible (LLBP) scenario due to the low probability of DRP exposure occurring. ln accordance with Section 5.5.2 ofNUREG-1757,9 an LLBP is used to " .. . better ri sk inform the decision" and to en ure that " ... unacceptabl y hi gh ri sks would not result." This is consistent with the approach approved in the Z ion LTP fo r as es ing th e low-probability cenari o of the well driller contacting the Auxiliary Building drains, which was also designated as an LLBP scenari o. ZionSolutions' approach is to demonstrate that the risk from the hypothetically remainin g DRPs is not unacceptabl y high . Co nsistent with the designation as an LLBP exposure scenario, the dose from hypothetical DRPs will not be added to the Zion site boundary dose for demonstrating compliance with l O CFR 20 Subpart E.
ZionSolutions proposes to revi se th e L TP by incorporating a new attachment into Chapter 6 entitled , "Less L ikely but Plausible Scenario for Expos ure to Hypothetical Discrete Radioactive Particles." The new attachment wil l di scuss the assessment of DRP dose and risk as an LLBP scenario, DRP exposure probability, and the methodology used to calculate ingesti on, inhalation, and skin exposure dose from DRPs in order to demonstrate that the ri sk from encountering a DRP is not unacceptabl y high.
Additionally, the criteria for determining that " unacceptably hi gh risks would not result" from the LLBP DRP exposure scenario will be provided .
The LTP Chapter 6 revision w ill a lso address radionuclides of concern and mixes specific to DRPs .
ZionSolutions will submit the revi sed LTP Chapter 6 with a LAR to the NRC.
L TP Change Criteria (AD-11)
ZionSolutions has e aluated this activity against the change conditions in Attachment E- 1 of procedure AD-11 and concluded that it requires prior NRC approval. As such, the proposed changes to LTP, Chapters 5 and 6, will be the basis of a LAR. Our conclusion is based on our reading of change criterion 9:
Change the approach used to demonstrate comp li ance with the dose criteria (e.g., change from demonstrating compliance using derived concentration levels to demonstrating compliance using a dose assessment that is based on final concentration data)?
The technical basis for the proposed changes to Chapters 5 and 6 of the L TP are described in detail in our response to RAI-10.
9 NUREG-1757, Vol. 2, Rev. 2, Draft, "Conso lidated Decommissioning Guidance - Characteri zation, Survey, and Determination of Radiological Criteria," Section 5.5.2, Eva luation Criteria for Decommissioning Groups 4 - 5 (Unrestricted Release Using Site-Specific Information), p. 5-20, September 2020 .
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ZionSolutions, LLC ZS-2022-010 Attachment NRC RAI-2b:
Please discuss the results of the evaluation as they impact the ZNPS licensing basis. If an outcome of the process was that the licensing basis is not impacted, please justify why thi s is the case when considering the information available.
ZIONSOLUT/ONS RESPONSE:
As described in the response to RAI-2a, ZionSolutions has concluded that the methodo logies to detect DRPs and to ca lcul ate the potential dose from DRPs hypothetically remaining at the site constitute a change to the ZNPS licensing basis. Specifically, proposed changes to the ZNPS LTP, Chapters 5 and 6, are being submitted to the NRC in a LAR for approval.
NRC Additional NRC Comment, p. 12:
"G iven the current information on final site radiological status, more information is necessary in order for the NRC staff to reach a determination that the Zion site meets the L TP bounding assumptions."
ZIONSOLUTIONS RESPONSE:
ZionSolutions believes the term "bounding ass umptions" to be equivalent to " license conditions" within the context of this RAJ. In this sense, Zio nSolutions believes that th e responses to RAI-2a and RAI-2b have adeq uate ly prov ided the additional information necessary for NRC to reach a determination that the Zion site w ill meet the LTP bounding assumptions fo llowing revisions as proposed in the LAR.
NRC RAI-3a:
Please explain whether the Zion LTP considered or addressed these radionuclides.
ZIONSOLUTIONS RESPONSE:
Transuranics, including Am-241 and Pu-239, were evaluated as part of the LTP deve lopment and were identified in the initial radionuc lide list as stated in Section 2.3 .2 of the LTP. During the final deve lopment of the ROC li st and the IC radionuclide list, several rad ionuclides were evaluated to be in the IC list including the transuranic radionuclides . The development of the ROC and IC lists is detailed within TSD 11-001 , "Potential Radionuclides of Concern During the Page 22 of96
ZionSolutions, LLC ZS-2022-0 I 0 Attachment Decommiss ioning of the Zion Station," 10 TSD 14-019, "Radionuclides of Concern for Soil and Basement F i11 Model Source Terms," 11 and captured in the L TP.
However, the site ' s ROC and IC lists are based on characterization data for distributed contamination in so il , radioactive waste, systems, structures, and components, and not DRPs. A LAR will be submitted to the NRC staff for review and approval that will include separate criter ia fo r DRPs and the specific radionuclides.
NRC RAI-3b:
Please provide additional information on the background levels of Am-241 and Pu-239 that might be attributable to fallout in the local area surrounding the Zion site. Alternatively, please provide an explanation for the presence of Am-241 and Pu-239 in the soils if these radionuclides are not attributable to fallout in the local area.
ZIONSOLUTIONS RESPONSE:
Background radionuc lides at Zion were evaluated as documented in TSD 13-004, "Examination of Cs-1 37 Global Fa llout in Soils at Zion Station." 12 This TSD contains information on the production of Cs-1 37 and Pu-239/240 in weapons testing and notes that the activity ratio of Pu-239 to Cs-137 in weapons testing is 1/86.
The TSD also contains information on Cs-137 (Figure 3) and Pu-239/240 (Figure 4) depositions by county in the United States. From this, the TSD concludes that the Cs-1 37 from fallout is 50 times higher than the Pu-239/240 depositions from fallout in the Zion area.
As part of the background assessment, a total of 64 samples were submitted to an off-site laboratory for analysis. Each soil sample was analyzed for gamma-emitting nuclides by gamma spectroscopy. The off-site laboratory analysis included Co-60, Cs-137, Sr-90, thorium isotopic (Th22 8, Th-230, and Th-232), and uranium isotopic (U-234, U-23S , and U-23 8).
From the so il sample analysis, the hi ghest Cs-1 37 result reported in TSD 13-004 was 1.14 pCi/g.
Us ing the expected activity ratio of Cs-137 to Pu-239 of 50, the estimated expected concentration of Pu-239 would be 2.82E-02 pCi/g. This is well below the nominal detection sensitivities for Pu-239 of approximately 0.1 to l pCi/g. Therefore, any positive detections of transuranic radionuclides in soil wou ld be considered plant-related rather than from fallout contributions.
10 ZionSofuti ons TSD 11-00 I, "Potential Radionuclides of Concern During the Decommissioning of the Zion Station," Revision 1, October 201 2.
11 ZionSolutions TSD 14-019, "Radionuclides of Concern for Soil and Basement Fi ll Model Source Terms,"
Revision 2, February 2017.
12 TSD 13-004, "Examination of Cs- 137 Global Fallout in Soils at Zion Station," Revision 0, May 20 13.
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ZionSolutions , LLC ZS-2022-01 0 Attachment The responses to RAI-Ja and RAJ-le descri be the likely origins of particles on-site, based primarily upon the radionuclide profi le of each.
NRC RAI-3c:
Compare background radiation levels to the leve ls that were identified in the soil samples collected during the April 2021 inspection survey, and provide an explanation of whether the Am-241 and Pu-239 identified in these samples is the result of licensed material or background radioactivity from fallout.
ZIONSOLUTIONS RESPONSE:
ZionSolutions considers the Am-241 and Pu-239 identified in these samp les to be the result of licensed material. As discussed above in the response to RAI-3b, the Am-24 1 and Pu-239 co ncentrations are significantly higher than those foun d in background . Additi onally, the responses to RAI-1 a and RAI-1 c describe the like ly origins of particles on-s ite, based primarily upon the radionuclide profile of each.
NRC RAI-4a:
The ZNPS CRs indicated a "yes"' under the "50.75(g) Issue" field. Please describe the factors that go into deciding whether an event is added to the Zion l 0 CFR 50.75 (g) file if it is indicated with a "yes" in an associated condition report. Please describe the factors that go into deciding whether contamination events are discussed in the site characterization portion of the L TP, and/or subsequently used to update survey plans.
ZIONSOLUTIONS RESPONSE:
A "yes" was indicated und er the "50 .75(g) Issue" field for the relevant CRs to indicate that the C/LT Manager needed to evaluate the potential need for an update to the 10 CFR 50.75(g) file as a result of the contamination event. Secti on 7.2.1 of AD-8, "Corrective Action Program" 13 (included in the enclosu re to this response) states:
If the event invo lves the spill or detection of radiological contamination around the facility, equ ipment or site, or involves encountering unexpected buried plant systems or components, notify the FSS manager of the potential for 10 CFR 50.75(g) considerations. Code the CR as " 10 CFR 50.75g" (for al l areas outside the ISFSI boundary) or " 10 CFR 72 .30d" (for all areas inside the ISFSI boundary) .
13 Zi onSolutions AD-8 , "Corrective Action Program ," Revision 12, November 2020.
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ZionSolutions, LLC ZS-2022-0 l 0 Attach ment Accordi ng to the procedure, the positive indication of "50.75(g) Issue" acts as a trigger for C/L T management action and not as a statem ent of the existence of a docum ented update to the 10 CFR 50. 75 (g) file. Upo n th e co nclusion ofC/LT management's cons ideration, an update to the 10 CFR 50 .75(g) file wo uld be made if signifi cant contam ination remained after any c leanup procedures o r there is reaso nable likelihood that contaminants may have pread to inaccessible areas.
The partic le release events were not included in the 10 CFR 50.75(g) fi le. Section 5. 1.1 of Z -
RP-104-001-003 , " JO CFR 50.75(G) and 10 CFR 72.30(D) Docum entation Requirements" 14 (included in the enclos ure to this response) states:
Document a record of each spill or other unu sual occ urrence involving the spread of contamination (subject to th e scope of thi s proced ure) in and aro und the site, on Attachm ent 1, Record for 10 CFR 50.75(g) or 10 CFR 72.30(d). These records may be limited to instances w hen signifi cant contamination rema ins after any cleanup procedures or there is reasonable li kelihood that contami nants may have spread to inaccessible areas.
Because the particle contamination was thought to be successfu ll y cleaned up and not spread to inaccess ible areas, no updates to the 10 CFR 50.75(g) file were made.
lnformation on rad ioacti ve particles identified by the licensee throughout deco mmi ssioning as we ll as during the Apr il 202 1 inspection su rvey does not indicate a need to upd ate or revise the process for including informatio n in the 10 CFR 50.75(g) file. The fi le would be updated onl y when signifi cant contam ination remains after any cleanup procedures or there is reasonable like lihood that contaminants may have sp read to inaccessible areas . Nei ther of these cases app lies.
The inputs to Chapter 2 of the Z ion LTP were the Historical Site Assessment (hi storical contami nation events) and ini tial site characterization. Rad iologica l characterization data co llected after L TP submittal were used to verify the proper classification of survey units and to upd ate sample plans.
NRC RAI-4b:
Considering that the majority of the site characterization activities took place prior to 2014, discuss why the site characterization discussion in the Zion LTP was not revised by the licensee to reflect the change in radiological conditions at the site that was determined in 2016, prior to the Zion LTP being approved in 2018.
14 ZionSolutions ZS'-RP-104-001-003 , " 10 CFR 50.75(G) and 10 CFR 72.30(0) Documentation Requirements,"
Revision 2, ovember 20 19 Page 25 of 96
ZionSolutions, LLC ZS-2022-010 Attachment ZIONSOLUTIONS RESPONSE:
The events were not included in th e characterizati on report or th e ini tial LTP because a decision was made not to modi fy either the characterizati on report or the L TP w ith results fro m co ntinu ing characterization or changing radiologica l cond itions at the site . In discuss ions with the N RC during the LTP subm itta l p rocess, it was agreed that co nti nui ng characte rizati on resu lts wo ul d be presented in the releva nt FSS re lease reco rd s. Survey uni t class ifi cati ons were changed from those presented during initia l site characteri zati on as warra nted when particles were discovered .
As stated in the responses to RAI-2a and RAl-2b, Z ionSolutions has concluded that the meth odologies to detect DRPs and to ca lcul ate the potential dose from DRPs hypotheti ca ll y remaining at th e site consti tute a change to the ZNPS li censing bas is. These changes to the ZNPS licensing bas is w ill be impl emented via modi ficati ons to Chapters 5 and 6 of the LTP and a LAR will be submitted to th e NRC.
NRC RAI-5a:
If not previously discussed in response to RAI-1 , please provide information that explains the source of this particle and how it came to be present in SU 12203A.
ZIONSOLUTIONS RESPONSE:
L ikely particle origins are discussed in the responses to RAI-la and RAI-lc. The like ly source of the particl e di scovered by ORISE in survey unit 12203A is reactor fuel. As di scussed in th e response to RAI-1 c, once introduced into the env ironment, the likely transportati on pathways for particles are surface water fl ow (runoff during heavy rains) and/or heavy equipment and vehicle movement.
NRC RAI-5b:
Explain why the particle not being found during the licensee's FSS of SU 12203A does not indicate overall quality issues with the Zion FSS methodology, given that the particle contained gamma emitting radionuclides at levels that were within the scope and detection capabilities of the Zion FSS design.
ZIONSOLUTIONS RESPONSE:
The des igned FSS detection scan capabili ties are fo r di stributed co ntamination, not fo r particl es .
The failure to detect gamma-emitting rad ionuclides on particles at levels th at were w ithin the scope and detection capabilities of the original FS S design does not in and of itse lf indi cate a qu ality issue, e ither w ith the methodology or the executi on of the FSS. A lthough parti cles are w ithin the detecti on capabilities of the instrum ents, the detection of the parti cles was not within the scope of th e FSS design. If during the perform ance of th e FSS a particle was detected, it was Page 26 of 96
ZionSolutions, LLC ZS-2022-0 l 0 Attachment removed. Separate efficiency versus di stance factors and detection capabiliti es would have to be calculated for particles because they represent a very different geometry, and the detector sensitivity varies with the scan rate, the probe swing rate, and the distance between a particle and the detector. The DRP Survey Plan was implemented to specificall y look for and remediate particles.
ZionSolutions will use the DQO process to address detection of DRPs given the potential for them to be present. Thus, particle point source detection efficiencies and license termination criteria should not be conflated with DCGLEMCS that are based on distributed contamination averaged over an area.
To address DRP detect ion during scanning, the ZionSolutions p lanning team used the DQO process, whi ch is described in the DRP Survey Plan.
NRC RAI-Sc:
Explain why the surrogate ratio for Sr-90/Cs-13 7 is different for thi s particle than that which was assumed for soils across the site, and as described in the Zion LTP .
ZIONSOLUTIONS RESPONSE:
The surrogate ratio for Sr-90/Cs-1 37 for the particle found in survey unit 12203A app li es to fuel particles, not distributed contamination. When the site characterization was performed, only Co-60 and Cs-13 7 were detected in soil samples. The surrogate ratio was based upon distributed contamination estimated from concentrations in Auxi li ary Building concrete samples obtained during characterization. A surrogate ratio should not be based on a single sample analys is because the overall uncertainty to other samples is high.
NRC RAI-Sd:
Evaluate the potential impact on the Sr-90 surrogate ratio assumed for SU 12203A due to the presence of this particle. Assess whether, in accordance with the Zion LTP, a survey unit-specific surrogate ratio should be applied to this survey unit.
ZIONSOLUTIONS RESPONSE:
A survey unit-specific surrogate ratio does not need to be applied to this survey unit because if particle S0126 was found during the FSS, it wo uld have been removed. The survey unit surrogate relationships apply to distributed radioactivity and require that the DCGLs be applied.
If the radionuclides were detected as di stributed activity and on ly gamma spectrometry was performed, the LTP surro gate Sr-90/Cs-137 of 0.002 would have been app lied. However, only one particle containing Cs-137 and Sr-90 was identified, and this is not representative of distributed contamination. Lastly, a surrogate ratio should not be based on a single sample analysis because the overall uncertainty to other samples is high . Based on the forgoing analys is, Page 27 of 96
ZionSolutions, LLC ZS-2022-010 Attachment ZionSolutions believes that a survey unit-specific surrogate ratio does not apply due to the presence of particles.
NRC RAI-5e:
Evaluate the potential impact on the Sr-90 surrogate ratio assumed for other Zion survey units that may contain similar particles, and explain why the surrogate ratio applied to these other survey units is still valid. Provide a discussion to support reasonable assurance that particles containing a simi lar ratio of Sr-90 to Cs-13 7 do not exist in locations outside of what the license considers to be the affected area.
ZIONSOLUTJONS RESPONSE:
The potential impact of the Sr-90 surrogate ratios assumed for other Zion survey units that may contain similar particles has been described in the response to RAI-5d. To provide a reasonable assurance that particles containing a similar ratio of Sr-90 to Cs-13 7 do not exist in locations outside of the affected area, a comprehensive DRP Survey Plan (including sampling) has been implemented. There was high confidence that DRPs were not in areas not included in the scope of the DRP Survey Plan, as explained in the response to RAI-lg.
NRC RAI-5f:
Provide the potential overall or compliance dose consequences of assuming a different Sr-90 to Cs-137 surrogate ratio within what the license considers to be the affected area.
ZIONSOLUTIONS RESPONSE:
The potential dose consequences fro m assuming a different Sr-90/Cs-137 (e.g., greater than 0.002) within the affected area wou ld result in a higher dose estimate. But, as noted in the response to RAI-5c, the surrogate ratios that were previously determined from characterization data are app licable to distributed residual radioactivity and not DRPs. To determine such a relationship, DRP DCGLs and a corresponding dose model would need to be established.
Therefore, using a Sr-90/Cs- 137 ratio from a fuel particle for potential dose consequences for distributed contamination in soi l in affected areas is not appropriate.
NRC RAI-6a:
Evaluate the potential dose contributions from the radionuclides that were defined as
" insignificant" radionuclides in the Zion LTP, using the range of ratios/radionuclides observed in the samples collected during the April 2021 inspection survey.
Page 28 of96
ZionSolutions , LLC ZS-2022-010 Attachment ZIONSOLUTIONS RESPONSE:
For the fuel DRP, the dose contributions from all radionuclides have been included. For the Co-60 particles, the dose calculations conservatively used all radionuclides estimated to be present in the reactor internals components. In these calculations, we provided the contribution from all radion uclides including those identified as insign ificant in the LTP . These dose calculation results wi ll be included in the LAR for Chapter 6 of the LTP. The details of these calculations are provided in Specific Consideration 36 ofRAI -10 .
NRC RAI-6b:
Evaluate the ability of the survey methods used during the Zion FSS activities to detect the potentially significant radionuclides identified during the April 2021 inspection survey that were not on the original ROC list for the Zion site.
ZIONSOLUTIONS RESPONSE:
The scanning methods used during the Zion FSS activities are standard industry practice. If a particle is detected during scanning, that particle is rem oved, regardless of radioisotopic content, including isotopes considered insignificant. The ROC list for the Zion site identifies radionuclides that comprise 90% or more of the dose even though other radionuclides are present at the site. Those identified HTD radionuclides can only be detected by laboratory analyses of samples. Based upon the responses to RAI-3a and RAI-6a, the HTD radionuclides identified in the samples do not change the ROC li st for di stributed radioactivity. However, a LAR will be submitted for NRC review and approval to revise Chapter 6 of the L TP to include DRP ROCs.
The original ROC list (for distributed radioactivity) for the Zion site does not need to be changed.
The most likely cause for why particles or other materials were not identified during licensee surveys is that the DQOs were not developed to detect particles. Nonetheless, ZionSolutions notes that 255 particles were identified and remediated during active decommissioning, and another 25 particles were identified and remediated during FSS or RAs, for a total of 280 particles discovered by ZionSolutions. The DQOs and survey methodologies were enhanced for the implementation of the DRP Survey Plan to provide a high degree of confidence that no DRPs posing an unacceptably high risk remain on-site.
NRC RAI-6c:
Evaluate whether the observed conditions are within the bounds of what was assumed in the Zion L TP (i.e ., 10% of the dose is from insignificant radionuclides) and what potential actions are needed (e.g., a license amendment to change the list of ROCs) if the final site conditions do not fall within the original assumptions used in the L TP.
Page 29 of96
ZionSolutions, LLC ZS-2022-010 Attachment ZIONSOLUTIONS RESPONSE:
As described above in the responses to RAI-6a and RAJ-6b, no action is needed to change the ROC list in the LTP for distributed contamination. ALAR will be submitted to revise Chapter 6 of the L TP to separately address ROC for DRPs.
NRC RAI-7a:
Indicate how the current site conditions are consistent with the commitments in the Zion LTP given the surface materials noted during the NRC ' s April 2021 inspection survey.
ZIONSOLUTIONS RESPONSE:
The surface material s noted durin g the NRC 's April 2021 inspection survey are similar in appearance to CCDD that was previously stored and moved around the site. CCDD was surveyed in accordance with regulatory guidance and approved procedures and was found to have no detectable activity above backgro und (see the response to RAI-1 a from the February 10, 2021 , submittal). The CCDD that was not placed into a basement has been removed from the site . Any residual CCDD that was inadvertently left on the surface durin g removal is concrete that was determined to have no activity above background. Additionally, the survey units where the residual CCDD resides was subject to a 100% gamma scan during FSS and the FSS passed in all cases. The satisfactory results of FSS do not necessitate further removal of the CCDD. In accordance with the LTP, clean fill material from an off-site source was used to fill the last 3 feet of each basement up to the 591 feet elevation (i.e. , grade) . As such, ZionSolutions believes that the current site conditions are consistent with the commitments in the Zion LTP.
Sample S204AEu in survey unit 12201B from the April 202 1 inspection survey contains radi onuclides consistent with neutron activation (e.g ., Eu-152, Eu-154), which is indicative of activated concrete originating from the containment bioshield and not the containment exterior concrete (CCDD) . A process was in place to load potentially contaminated concrete into containers in a controlled fashion to limit the spread of contamination. As discussed in the responses to RAI-la and RAI-lc, the internal containment bioshield concrete was likely introduced into the so il durin g waste handling operations. This potential error in waste handling does not indicate a failure to follow commitments made in the L TP .
NRC RAI-7b:
Provide information on whether the material on the Zion site surface is demolition debris that should have been removed during decommissioning, offsite gravel that was used for grading, or some other explanation for its presence, such as basement fill that has been disturbed by action of weather (e.g. , erosion, freeze-thaw cycles) or site operations.
Page 30 of96
Z ionSolutions, LLC ZS-2022-010 Attachment Z IO NSOL UTION S RESPONSE:
During decommissionin g and site restoration, Z ionSolutions attempted to ensure that demolition debris was removed. The informat ion th at Z ionSolutions provided follow ing the May 20, 2021, te leconference describes ZionSolutions' best effort to document the position that every effort was put forth towards cleanin g up as m uch demolition and concrete debri s at the ite as reaso nab le.
Upon further review, ZionSolutions does not be lieve that debris identified is fi ll material brought to the surface by freeze -thaw cycles or erosio n. Wh ile conceivable, the freeze-thaw scenar io is un likely because sand was used as the majority of the surface fi ll material for the power block area to replace the sacrific ial layer that was remedi ated.
While Z ionSolutions cann ot prec ise ly explain the sou rce of concrete debr is or debris-li ke material, ZionSolutions has identified th e fo llowing as the most li ke ly sources for the materi al that was observed.
- Waste Handling Operations. It is possible that on rare occasions, m inimal concrete was introd uced into the environment during waste hand ling operations. Recent walk-downs revea led minim al instances of identified potentia l demoli tion debris. In order to ensure th at any activity res ulting from waste handling has been remediated, survey units w here railcars were loaded and prepared fo r shipment were surveyed as part of th e DRP Survey Plan. Additionally, when CCDD was removed from the six survey un its (12203A, 12203B, l 2203C, 12203D, 12 11 2, 12 11 3) where it was temporaril y stored or transported through and the five survey units where it was stored long-term (1 2205A, l 2205B ,
12205C, 12205D, 12205E), residual CCDD may have inad vertently been left behind . In these eleven survey units, FSS has been reperformed.
- Non-Concrete Material Was Misidentified . Lastly, it is poss ible that the concrete observed by ORISE and the NRC was actu all y sandstone gravel, used for roadways, which can be mi staken for small concrete chun ks. Additi onally, clean fi ll soil from th e Z ion landfi ll th at was used for the top 3 feet of basements an d to fi ll excavations was clay-like. When this clay-like materia l is dried, hardened, and subsequ ently di sturbed, it can resemb le small concrete chun ks. This material was surveyed prior to being imported on-site and was also subject to scanning durin g FSS.
NRC RAJ-Sa:
Discuss the final site configuration for the Zion site areas that received a sacrificial layer of soil that was subsequently removed and remediated, and over which clean fill material was emplaced. Specify the thickness of the clean cover material intended for the end state over these areas, and from where the clean cover material was sourced . Indicate the survey units where this final site configuration exists.
Page 31 of 96
ZionSolutions , LLC ZS-2022-010 Attachment ZIONSOLUTIONS RESPONSE:
Prior to the demoliti on of th e Unit 1 and Unit 2 Containment Buildings, an approximate 1.5 feet layer of sacrificial so il was placed in the areas identified in Figure 3 below. The sacrificial layer was compri sed of th e c lay-li ke material from the Z ion landfill. After demolition of the Containment Buildings, the sacr ifi cial layer was removed in its entirety and any soi l beneath the sacrificial layer that had residual radioactivity above the OpDCGL was remediated as necessary.
This remediation potentiall y took so il away from the minimum 3-fo ot thick fill layers within the footpri nt of previously-backfilled structures.
A large-scale RA was performed over the entire power block area, and the results were previously presented in the February 10, 202 1, submittal ("Power Block RA Report Attachments"). In order to bring these areas back to grade level , in the instance that remediati on necessitated the removal of soi l below grade, sand was bro ught on-site from the Antioch quarry.
The thickness of the clean cover material intended for the end state over these areas is 3 feet.
The survey units that we re impacted by the sacrificial layer of soil and subsequent potential remediation are as fo llows: 10203F, 12201 A, 12201B, 12201C, 12202A, 12202B, 12202C, 12202D, 12202E, 12202F, 12104, 12105, 12 106, 12107, 12108, 12109, 12110, 12111.
Page 32 of 96
ZionSolutions, LLC ZS-2022-0 l 0 Attachment Figure 3- Sacrificial Soil Boundary 64 1928.10 343603 .37
~. :
rrrrrrr,,
0 II IO 31 1.1at9rt Legend Sacrifiial Soil D Sacrific ial Soil Boundary NADBJ IL Sista Plane East 1201 (Meters}
2011 Aerials Lake County GIS Dept.
Date Modified: 02/1 2/20 19
- Points to be GPS 'ed Sacrifical Soil Page 33 of96
ZionSolutions , LLC ZS-2022-010 Attachment NRC RAI-8b:
For the areas of the site directly above backfilled basement structures (including the ZNPS Crib House basement in SU 12204), verify that the thickness of the clean cover material between the land surface and the upper level of the basement fill material is consistent with the Zion L TP commitments and the description of the site end state in Phase 4 of the Zion FSSR.
ZIONSOLUTIONS RESPONSE:
The thickness of the clean cover material between the land surface and the upper level of the basement fi ll material for the areas of the site directly above backfilled basement structures has bee n reviewed and determined to be consistent w ith the Zion LTP commitments and the FSSR.
The methodology for this assessment is described below.
All remaining structure basements were demo lished to three feet below grade level (588 feet elevation). As the demolition was completed for a given structure, a third-party surveyor was brought in to perform an elevation survey. Locations for the elevation surveys were based on judgment, e.g., did the e levation appear higher than the surrounding area. Readings were collected and results were evaluated immediately. The contractor would be notified, as necessary, if any of the locations needed additional material removed to meet the 588 feet maximum elevation. The as-left elevations for the basement structures were verified by the third-party surveyor prior to backfill.
The basements were backfilled using CCDD or clean soil from the Zion landfill. The Zion landfill was tested and approved as an uncontaminated off-site soil source. The final three feet of fill from the 588 feet elevation up to grade (59 1 feet elevation) consisted of clean soil from the Zion landfill, or as noted in the response to RAI-8a, sand from the Antioch quarry. Final elevation measurements were performed after backfill to verify that the as- left soil elevation was at grade. Figure 4 and Figure 5 below show the as-left so il elevations for the power block area.
As detailed in the response to RAI-lj , final site grading was completed on September 23 , 2020.
After completion of final site grading, another elevation survey was performed, the result of which is shown in Figure 6. ZionSolutions commits to confirming that final soil elevations are consistent w ith the LTP. If future observations reveal conditions inconsistent with the assumptions made in the LTP, ZionSolutions commits to making any modifications necessary.
Page 34 of96
ZionSolutions, LLC ZS-2022-010 Attachment Figure 4 - Unit 1 Area Grade Measurement Locations SU12113 Final Grade Elevation Locations Grade Locations 08/29/20 19 Drawing: Final Grade Locat1on1 Page 35 of96
ZionSolutions, LLC ZS-2022-0 l 0 Attachment Figure 5 - Unit 2 Area Grade Measurement Location s I
I I / I I I ! / I i
i/ I I f
! I i I
SU10203A j /
SU122018 I I i
SU12201A SU12201C I
I SU12201D I 202A
- ~--- .._,
U12202D SU1 Legend 12111 Final Grade Elevafion Locations 0 F'nal Gtade LOUtiona I Date* OW23/201i
- o,awing
- Anal Grade Locations Page 36 of96
ZionSolutions, LLC ZS-2022-010 Attachment Figure 6 - October 2020 Elevation Survey
_ . , . _ ,..._ OONtOJII
"""\..,+,.,,.....Jlot Sfi SHEET AS801 QWWWIOFW-.IUIICII _ . , . , .
101 SHILOH BOULEVARD ZION, IL 60099 ZION SOLUTIONS AS-$UILT GRADING PLAN ASB02 Page 37 of 96
ZionSolutions, LLC ZS-2022-010 Attachment NRC RAI-Sc:
Justify how current site conditions are consistent with Zion LTP. Jfthe Zion site conditions are not consistent, discuss the intended path forward (e.g., a license amendment to revise the assumptions in the Zion LTP) to resolve the inconsistency.
ZIONSOLUTIONS RESPONSE:
The following are the commitments to site conditions as detailed in the LTP:
- All on-site buildings, structures, and components must be demolished and removed to a depth of at least 3 feet below grade.
- The structures are backfilled with CCDD or soil from an off-site source.
- The Basement Fill Model applies to the backfilled basements which will have a minimum of three feet of cover and approximately 3 meters of clean fill above potential source term as defined by the equilibrium water level in the backfilled basements. The equilibrium water level is conservatively assumed to be at the natural water table elevation of 579 foot. Therefore, the dose from the water-independent exposure pathways is negligible.
ZionSolutions is confident that the final site conditions are consistent with the LTP. It is possible that, because of the times at which structures were backfilled (earlier in the decommissioning process in some cases), a piece of concrete or debris on the surface could have been inadvertently deposited on the surface and forced to a lower depth into the top 3-foot layer of clean soil fill through the movement of heavy vehicles. The presence of a small piece of concrete within the 3 feet of cover is not significant and would not require a license amendment to revise the assumptions in the Zion L TP.
Elevation surveys, as detailed in the response to RAI-8b, were performed to verify that basement structures were no higher than the 588 feet elevation. Elevation surveys were performed after backfill to verify the as-left soil elevations were at grade (3 feet above basement structure).
Additionally, section 6.6.1.1 of the LTP states, "For DUST-MS modeling, the initial source term in each basement is nominall y assumed to be 1 pCi/ m2 uniform activity over all walls and floor surfaces below 588-foot elevation." Section 6.6.1.2 states, "To accommodate any future perforation plans, and ensure conservatism, the mixing volume for the DUST-MS modeling is based on a basement water elevation equal to the 579-foot elevation of surrounding groundwater." The model assumed all of the activity on walls above the 579-foot elevation is instantly mixed with the water below the 579-foot elevation. Since there is no dose from walls in the unsaturated zone above the 579-foot elevation, a 3.6-meter cover was used in RESRAD.
(591 -579 = 12 feet= 3.6 m). Because the basement walls remain 3 feet below grade at the 588-foot elevation, and the grade is verified to be at the 591-foot elevation, the water-independent Page 38 of96
ZionSolutions, LLC ZS-2022-010 Attachment dose pathways used to determine compliance with the dose criteria for unrestricted release remain unchanged.
NRC RAI-8d:
If the thickness of the clean cover material is less than that assumed in the Zion LTP, or the erosion rate is greater than what was assumed in the RESRAD dose modeling for the Zion site, provide an evaluation of the dose resulting from the material in the Zion basements structures with the lower amount of shielding/dilution.
ZIONSOLUTIONS RESPONSE:
As described above in the answers to 8a-c, the conditions at the site, including the thickness of the clean cover material , are as assumed in the Zion LTP . There has been no significant erosion since final site grading on September 23 , 2020. Despite these circumstances, we have prepared the following analysis to demonstrate that even in the case of some future erosion, the depth of cover is adequate to provide for the health and safety of a hypothetical occupant.
The relative dose was calculated under three conditions to evaluate the effect of increased cover erosion rate and decreased cover thickness.
- Condition 1: BFM RESRAD model as applied in the L TP
- Condition 2: BFM RESRAD model with erosion rate increased to the 75 th percentile (2.92E-03 m/y) and cover thickness reduced by 0.5 m
- Condition 3: BFM RESRAD model with erosion rate increased to the 75 th percentile (2.92E-03 m/y) and cover thickness reduced by 1.0 m The relative doses from the ROC under each condition were calculated using the following equation:
Equation 7 - Relative Dose where RD = relative dose for ROC JA; = activity fraction for radionuclide i DSR; = dose to source ratio for radionuclide i (mrem/yr per pCi/g)
The ratio of relative doses from Condition 2/Condition I is 1.0 for both the Containment and Auxiliary mixtures. The ratio from Condition 3/Condition 1 is 1.10 for both mixtures. In summary, there is no change in dose when the cover thickness is reduced by 0.5 m. The dose is 10% higher when the cover is reduced by 1.0 m.
The relative dose results are provided in the three tables below:
Page 39 of96
ZionSolutions , LLC ZS-2022-010 Attachment Table 6 - R elative Dose LTP DSR Relative Dose LTP Radionuclide LTP Containment Mix Aux Mix H-3 2.1 69E-0l l.619E-04 Co-60 1.122E-0l 5.291E-03 l.029E-03 Ni -63 l .573E-02 4.169E-03 3.729E-03 Sr-90 4.362E+0l l .188E-02 2.246E-02 Cs-1 34 l.935E+00 l. 562E-04 l.954E-04 Cs-137 1.536E+00 1.047E+00 1. l 57E+00 Eu-152 3.801E-02 l .672E-04 E u-154 5.520E-02 3.230E-05 Sum l.07E+00 1.18E+00 Table 7- R elative Dose 75th Percentile Erosion and Cover Thickness R eduction of 1.0 m DSR Relative Dose Radionuclide 75th Percentile erosion Containment Mix Aux Mix 1 m cover reduction H-3 2.269E-01 l.69E-04 Co-60 2.064E-0l 9.73E-03 l.89E-03 Ni-63 l.869E-02 4.95E-03 4.43E-03 Sr-90 4.670E+0l l.27E-02 2.40E-02 Cs-134 2.122E+00 l.7 1E-04 2.14E-04 Cs-137 l.685E+00 1.lSE+00 l.27E+00 Eu-152 3.833£-02 l .69E-04 Eu-154 5.575E-02 3.26E-05 Sum 1.18E+00 l. 30E+00 Table 8 - R elative Dose 7511' Percentile Erosion and Cover Thickness Reduction of 0.5 m DSR Relative Dose Radionuclide 75th Percentile erosion Containment Mix Aux Mix 0.5 m cover reduction H-3 2.169E-0l l.62E-04 Co-60 1. l 25E-01 5.31E-03 1.03E-03 Ni-63 1.574E-02 4.17E-03 3.73E-03 Sr-90 4.384E+0l 1.19E-02 2.26E-02 Cs-134 1.935E+00 l.56E-04 l.95E-04 Cs-137 1.536E+00 l.0SE+00 1.16E+00 Eu-152 3.797E-02 l.67E-04 Eu-1 54 5.522E-02 3.23E-05 Sum l.07E+00 l.18E+00 The actual erosion rate is less than what was assumed in the RESRAD dose modeling for the Zion site. One instance of significant erosion was identified in ES-ZION-CR-2020-0001 (included in the enclosure to this response), where the area south of the Forebay and Cribhouse basement appeared to have eroded approximately 2 feet. This area was backfilled to the 591 foot elevation during final site grading. There are no v isible signs of erosion in this area or any other area above basements since final site grading.
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ZionSolutions , LLC ZS-2022-0 l 0 Attachment NRC RAI-9a:
Describe how any soil reuse aligns with the commitments in the Zion LTP.
ZIONSOLUTIONS RESPONSE:
Soi l was stockpiled and reu sed only to support buried pipe or other commodity removal. in each of these instances, an RA was performed using the methodology outlined in Section 5.7.1.7 of the L TP . Soil was always reused in the excavation from where it came (i.e., soil that originated from site was never stockpiled and used as fill later on).
Soil reuse as performed during decommissioning aligns with Section 5.7.1.7 of the LTP. The response to NRC RAI Question 8a from the February 2021 RAJ responses submittal is reiterated below.
Section 5.7.1.7 of the LTP states:
ZSRP will not stockpile and store excavated soil for reuse as backfill in basements. However, overburden soils will be created to expose buried components (e.g. concrete pads, buried pipe, buried conduit, etc.) that will be removed and disposed of as waste or to install a new buried system. In these cases, the overburden soil will be removed, the component will be removed or installed, and the overburden soil will be replaced back into the excavation. ln these cases, a RA will be performed. The footprint of the excavation, and areas adjacent to the excavation where the soil will be staged, will be scanned prior to the excavation. ln addition, periodic scans will be performed on the soil as it is excavated, and the exposed surfaces of the excavated soi l will be scanned after it is piled next to the excavation for reuse. Scanning will be performed in accordance with section 5.7.1.5.1. A soil sample will be acquired at any scan location that indicates activity in excess of 50% of the soil Operational DCGL.
Any soil confirmed as containing residual radioactivity at concentrations exceeding 50% of the soil Operational DCGL will not be used to backfill the excavation and will be disposed of as waste.
All radiological surveys performed to evaluate soils from the excavations of buried pipe, including the grade footprint of the excavation, the grade footprint of the overburden laydown area, the bottom and sidewalls of the excavation, and acceptability of the overburden to be used to eventually backfill the excavation were performed in accordance with Section 5. 7 .1. 7 of the LTP. RAs were designed, evaluated, and documented in accordance with ZionSolutions procedure ZS-LT-200-001-001 , "Radiological Assessments and Remedial Action Support Page 41 of 96
ZionSolutions, LLC ZS-2022-0 I 0 Attachment Surveys." 15 For all media sampling performed to evaluate excavation soils, the OpDCGLs for subsurface so il s fro m Table 5-8 of the LTP were used as the action level. The action level for scanning was set at the MDCR of the instrument plu s background. The in stru ment and data quality requirements spec ifi ed in procedure ZS-LT-200-001-001 for the performance of an RA are the sam e in strument and data quality requ irements required for the performance of FSS. The results of the RAs in these cases were provided to NRC Region Ill who, after review, provided concurrence that the excavations were suitable for backfilling.
As outlined above, soi l reuse ali gns with the comm itments in the Zion LTP.
NRC RAI-9b:
Provide justification and documentation of the process used to determine soil reuse as appropriate, including radiological scans for any soils that were reused from other parts of the Zion site and describe how the process aligns with what was discussed in the RAI response associated with the Zion L TP review dated February 27, 2017 (ADAMS Accession No. MLI 7208Al21).
ZIONSOLUTIONS RESPONSE:
The process used to determine when soil may be re-used on site is detailed in Section 5.7.1.7 of the L TP, as is reiterated in the response to RAI-9a. The soil must be surveyed under an RA and shown to have radion ucl ide concentrations below 50% of the soi l OpDCGLs before it can be reused.
As stated in the response to RAI-9a, so il s were excavated and reused on ly to support buried pipe or other commodity removal. Spoils from a particular excavation were placed back into the same excavation (and not transported around the site to be used in a different location) once the criteria for reuse of the soi l was met as outlined in the RA. The acceptabi lity of the soil to be reused as fill is determined by soil sampling and not scan meas urements. The criteria for reuse of the so il is that the concentrations in the soil are below 50% of the soil OpDCGLs. Any soil confirmed as containing residual radioactivity at concentrations exceeding 50% of the so il OpDCGLs was not used to backfill the excavation and was disposed of as waste.
The RAI response associated with the Zion LTP rev iew dated February 27, 2017 (ADAMS Accession No . MLl 7208Al21) provided a basis of the language presented in Section 5.7.1.7 of the LTP and in ZS-LT-200-001-001.
The buried pipe removal RA res ults are not di scussed in the relevant release records, and as such the RA results were provided to the NRC in the enclosure to the February 2021 RAI responses 15 ZionSo lutions ZS-LT-200-001 -001 , "Radiological Assessments and Remedial Action Support Surveys," Revision 6, May 2019.
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ZionSolutions, LLC ZS-2022-01 0 Attachment subm ittal (a spreadsheet entitl ed "Buried Pipe RA Results"). The location and timing of circum stances where so il reuse occurred is prov ided in the above-mentioned spreadsheet and in the response to NRC Request 8a from the February 202 1 RAI responses submitta l. Radi ologica l scan data fo r so il s that were reused (RA data) were not di gita ll y archi ved before being sent to long-te rm reco rds torage . such, th e scan data are not readil y avai lab le. ln lie u of scan resu lt .
ZionSolutions has prov ided thi s comprehensive spreadsheet that deta ils the soi l sample results (i.e., compli ance measurements to veri fy acceptabili ty as fill ) fro m every buri ed pipe RA .
NRC Additional NRC Comment, p. 34:
"These preliminary responses are not adequate for the NRC staff to verify that the reuse of excavated soil at the site is consistent with the commitments included in the Zion L TP."
ZIO SOL UTIONS RESPO SE:
ZionSolutions wants to clari fy that it was not the intent of the p re li m inary response to suggest that the 3-foot clean cover stratum above backfill ed stru ctures includes nati ve so il or reused so il.
The intent of the preliminary response was to demonstrate that th e commitment to have the top 3 feet of each basement structu re filled w ith clean so il fro m an off-site source was met and that that criterion does not apply to the entire site, only the footprint of backfilled structures.
ZionSolutions would like to reiterate th at spo ils from a parti cular excavation for buried pipe or other comm odi ty remova l were placed bac k into th e same excavati on and not transported aro und th e site to be u ed in a di ffere nt location once the criteria for reuse of the soil were met as outlined in the RA and in Section 5.7.1.7 of the LTP.
NRC RAI-10 PATH FORWARD:
The licensee should demonstrate how its FSS meets IO CFR 20 .1402, or propose a revised survey plan specifically designed for detecting and removing discrete radioactive particles. Goal s of this survey would be to : (I) detect discrete radioactive particles; (2) remediate detected discrete radioactive particles ; (3) determine the radionuclide composition and activity of the collected particles; (4) estimate the number of discrete radioactive particles that may remain at the site after the survey is completed (i .e., discrete radioactive particles either missed or below the MDA); and (5) facilitate collection of information necessary (physical and chemical properties) to estimate the radiation dose from discrete radioactive particles that may remain at the Zion site after the survey is completed. In developing its survey plan , the licensee should consider the information provided below, in add ition to other applicable resources, as it applies to the Zion facility. In this approach, it is expected that the licensee wou ld collect discrete radioactive particles that were detected during the survey, and then analyze them to better understand their characteristics and impact on the final site assumptions.
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment Due to the lack of specific NRC guidance on planning and conducting surveys for discrete radioactive particles at this time, the staff is providing the following information that the licensee may consider when developing its survey plan, if it chooses to develop a survey plan. Overall ,
the licensee should consider using the Data Quality Objectives Process, as recommended in the existing NRC guidance for planning decommissioning surveys. In addition, the survey plan should take into account the results from the limited-scope NRC confirmatory conducted in April 202 1 and describe which portions of the site are to be surveyed, along with the rationale for any portions of the site not included in the survey. This rationale should consider information on the source and transport of the discrete radioactive particles provided in response to RAI-1 in the NRC letter dated August 19, 2021 (ADAMS Accession No. ML2 I 23 I A 187). Also, when design ing the survey plan and determining the MDA for discrete radioactive particles, the licensee should consider the investigation levels that may require a change to the Zion LTP (i.e.,
ZNPS License Condition 2.C.(17) Criterion F).
ZIONSOLUTIONS OVERVIEW FOR RAI-10 ZionSolutions has designed and impl emented a revised survey plan, Survey Plan for Discrete Radioactive Particle Identification and Remediation, ZS-LT-07, Revision l (the "DRP Survey Plan"), spec ifi ca lly for the purpose of detecting and removi ng discrete rad ioactive particles (DRPs). The DRP Survey Plan 16 is included as part of the ZionSolutions response to RAI-10.
The objective of the DRP Survey Plan is to identify and remediate all the DRPs identified. This will provide reasonable assurance that there wi ll be no DRPs remaining on the Zion site that could pose an un acceptab ly high risk to a member of the public. Based on the completion of the survey and investigations, an estimate of the number and activity ofDRPs that may hypothetically remain has been made and the dose and risk from the hypothetical DRPs has been estimated.
ZionSolutions has performed an extensive dose evaluation, described in detail in response to Specific Consideration 36, that evaluates all potential effective doses and exposure pathways from particles with Co-60 or Cs-1 37 activities exceed ing the 50 th percenti le a po teriori MDAs of the survey. This includes potential doses if the particles' physical or chemica l properties change over time. Cs-13 7 is used as a surrogate isotope for transuranics in spent fuel particles.
The DRP exposure scenario has been evaluated as a less likely but plausible (LLBP) scenario due to the low probability of DRP exposure occurring. In accordance with Section 5 .5 .2 of NUREG-17 57, an LLBP is used to " ... better ri sk inform the decision" and to ensure that 16 References to the DRP Survey Plan also include the material described in the accompanying technical support document (TSD), "Calibration and Discrete Radioactive Particle Detection Sensitivity and Performance Assessment for a Lud lum 44-10 Six-Detector Array," TSD 21-00 I, Revision 2.
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment
" ... unacceptably high risks wo uld not result." Z ionSolutions' approach is to dem onstrate th at the risk from the hypothetica lly remaining DRPs is not unacceptably hi gh. Consistent w ith the des ignati on as an LLBP expos ure scenario, the dose from the hypothetical DRPs w ill not be added to th e Zion ite bound ary dose for demonstrating compli ance w ith 10 CFR 20 Subpart E.
The dose eva luation demon strates th at ingesting an irradiated fuel particle with an acti vity correspondin g to the 50th percenti le a posteriori Cs-1 37 MDA woul d not res ult in an un accepta bl y hi gh risk. T he dose from thi s hypo th etica l particle wo uld be 59.0 mrem (CEDE),
which is acceptable for an LLBP scenar io. The use of the 50 th percenti le a posteriori MDA is reasonab le for an LLBP scenari o. NUREG-17 57 Vol. 2, Appendix I, ection l.3.3.3 .7 states that:
"A nal yses of les like ly but plausibl e scenar ios are not meant to be 'worst-ca se' analyses and should not utili ze a set of ' wor t-case ' param eters. "
A techn ica l support document (TSD) that describes th e resu lts of th e survey, the dose calculations, and the ri sk calcu lations, wi ll be submitted to the NRC staff. This approach, i.e.,
submi tting dose modeling resu lts either in the L TP or in another document, in thi s case a TSD, is consistent with the guid ance in NUREG-1757. 17 The DRP Survey Plan In the absence of NRC guidance for how to devise a survey plan w ith the objective of identifyi ng DRPs over a large area such as a nuclear power plant decommissionin g site, Z ionSolutions dev ised and implemented a survey that was focused on coverin g a large area to identify DRPs.
The survey approach re li ed on proven techn ology and incorporated avai lable indu stry experience in conductin g field surveys. It also took into co nsideration the information provided by staff in the Octo ber 14, 2021 , RAI letter. ZionSolutions beli eves that this approach prov ides a high level of confidence that remaining DRPs wi ll be detected and remediated. The DQOs of this survey plan and the equ ipment used suppl ement the FSS and provide confidence th at any remaining DRPs that mi ght pose an unacceptab ly hi gh ri sk to a member of the public have been identifi ed and remediated .
Relevant License Termination Cases ZionSolutions a lso considered the app roach taken by other licensees. There are at least three notable and re levant examp les where DRPs a l o were a concern .
During ORISE confirmatory surveys fo llowing FSS at Rancho Seco, areas of e levated activi ty were identified that were due to DRPs. Si nce ORISE on ly surveyed portion s of applicable survey units that p otentially could have DRPs, NRC requested Rancho Seco perform add itional surveys.
Rancho Seco developed a particle scan protoco l based on the ability to detect a 1 µCi Co-60 particle. The licen ee co nducted additi ona l surveys and provided a description of its actions in 17 NUREG-1757, Vol. 2, Rev. 2, Draft, Section 5.1, Introduction, p. 5-1 , November 2020.
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ZionSolutions , LLC ZS-2022-0 l 0 Attachment response to the DRPs and a dose analysis in its site release request. 18 Rancho Seco identified 32 elevated activity items in its re-surveys and remediated any identifi ed areas of elevated radioactivity. The NRC staff reviewed the licensee ' s actions and determined that they were acceptab le. In August 20 18, the NRC terminated the license. As shown in the response to Specific Consideration I b, the towed array used for the Zion DRP survey a po teriori MDA value for Co-60 is 0.12 µCi. This is significantly more conservative than the Ranch Seco detection capabi Iity .
The license termination of the Shel well Services site in Hebron , Ohio provides another example of acceptable methodologies for license termination where DRPs are concerned. The NRC staff used a probabilistic approach to calcul ate an "expectation dose" for partic les potentially remaining on the site after license termination. The surveys used for site release utilized µR do e rate meters . The approach approved by the Comm ission for the termination of the She lwell license is summarized in SECY-98-117. The NRC terminated the license in July 1999. Our response to Specific Consideration 3b provides the expectation dose calculation for the Zion site using this methodology.
1n 2005 , Yankee Rowe performed an evaluation to evaluate the effectiveness of in-situ gamma pectroscopy to detect DRPs (Y A-REPT-00-018-05). A concentration of 1.0 pCi/g (Co-60) was fo und to correlate to a discrete point source of approximately 3.2 µCi. This activity value was considered as the discrete particle of concern. Discrete particles exceed ing this magnitude were considered to be readily detected during characterization or investigation surveys . The MDCs associated with handheld field instruments u ed for scan surveys were considered capable of detecting very sma ll areas of e levated radioactivity that could be present in the form of discrete point sources. Yankee Rowe determined that the minimum detectable particle activity for these scanning instruments and methods corresponded to a small fraction of the TEDE limit provided in 10 CFR 20 Subpart E.
The approach taken in the DRP Survey Plan is more conservative than the ones implemented at Rancho Seco, She lwe ll , or Yankee Rowe. Th is section provides an overview of the approach . A complete description is contained in the DRP Survey Plan ; respon e to NRC ' s specific considerations po ed in the RAI letter are given below.
The Towed Array ZionSolutions devised a survey approach that used a towed 62 inch-wide array of six Ludlum Model 44-10 2" x 2" Nal(TI) detectors mounted on a utility terrain vehicle (UTV) and attached 18 Letter, Einar Ronningen to .S. NRC, "Phased Release of the Rancho Seco Site," Sacramento Muni cipal Utility District, ADAMS Accession o. ML091670511 , June 8, 2009 .
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment to a Lud lum M odel 4612, a 12-chann e l counter data logger (the "towed array"). 19 The unit was eq uipped w ith a single Trimble GA8 10 GPS rece iver and antenn a combined with a hi gh-accuracy inerti a l meas urement unit (IMU). The L udlum Model 4612, Trimble GPS receiver, and the IMU are integrated using an on-board tablet or laptop computer (control computer) running the scannin g softwa re.
The towed array has signifi cant adva ntages over hand scannin g. It provides th e abi lity to cover a large area fa r more efficientl y than hand scannin g. This is co nsistent w ith the proposed gui dance in the update to MARSSIM (Draft Rev. 2) where the NRC staff was invo lved . While we recognize thi s draft is not to be cited or quoted, we believe it is informati ve because it recognizes that major advances in technol ogy have occ urred since th e last revision. These advances have encouraged th e use of automated scanning as a viable option for large area surveys . In additi on, MARSSIM (Draft Rev. 2) also recogni zes that hand-held survey ing remains the more economical choice for a small area, but as the area increases, the cost of an automated system becomes an increasingly worthwh ile investment to reduce manual labor costs associated with surveyi ng as th e case for the Zio n DRP survey .
Key Features of the Towed Array Some key features of the survey methodology are:
- Scan parameters. The towed array wi ll be operated on a continuous basis at a speed not to exceed 0.6 m/sec (1. 34 mph). The detectors wi ll be approximately 4" from the soil surface.
- Detection efficiency. The a priori MDAs for the towed array are described in Section 3 .4.1, Gamma Scan Survey with Towed Array, of the DRP Survey Plan .
- Hard to detect radionuclides. Hard-to-detect (HTD) radionuclide concentrati ons w ill be determined by direct analys is. Any identified non-Co-60 DRPs w ill be sent to the off-s ite laboratory for analysis of the full suite of radionuclides .
- Area to be surveyed. 100% of the accessible surface area of the survey uni ts listed in the DRP Survey Plan were scanned using the towed array. Areas inaccessible20 to the towed array were surveyed using hand-scanning methods.
19 The towed array and other aspects of th e approach are described in detail in Section 3 .4, Description of Planned DRP Survey Activities, of the DRP Survey Plan.
20 The term inaccessible in this context means that the towed array survey could not be performed within the parameters that were determined in the probabili stic modelling in TSD 2 1-001 , Revision 2.
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ZionSolutions , LLC ZS-2022-010 Attachment Basis for Selecting Areas to Survey Thirty-six survey units were selected for surveying usin g the DRP Survey Plan . The detailed justification fo r selecting these areas is provided below in the response to Specific Consideration 4a. These areas were elected because they were considered at hi gher risk fo r the presence of DRPs based on decommissioning proj ect experi ence (e.g. , a locati on where c lean concrete demoliti on debri s (CCDD) was temporarily stored or transported th rough), or where previous surveys identifi ed particles or areas of elevated ac ti vity .
The areas w ithin the scope of the DRP Survey Plan wou ld be expanded, as necessary, as a result of investigations performed to bound areas of elevated radioactivity or as a result of remediation.
The rationa le for areas not included in the DRP Survey Plan is that based on process knowledge and the results of previous radio logica l surveys, including but not limited to successful performance of FSS and ORISE independent verification surveys, there is a low potential for the presence of DRPs.
Detailed Investigation of Elevated Activity Detected by the Towed Array The investigation was des igned to identify and remove DRPs that potentially were the source of the elevated reading by the towed array. Any time the in vestigation level was exceeded during the towed array survey, a detai led investigation was performed. A summary of how the detailed investigation was conducted21 is as fo llows:
- Scan the elevated area using a hand-held Nal detector to locate the precise area of the elevated activ ity. Mark the location in the field with a fl ag or similar. If the area of elevated activity cannot be duplicated, then make a notation in the field notes and no further actions are necessary.
- If an area of elevated activity is detected , obtain a measurement using a portable gamma spectroscopy instrument and a 10-minute count.
- If a plant-related radionuclide is identifi ed, co llect a soil sample in the location down to a depth of 12 inches, capturin g at least 2 liters of so il to remediate the potential DRP.
- Spread the so il sample out into a pan or other appropriate container to an approximate 1-inch thickness. Use the hand-held Nal detector to try to iso late a potential DRP . Any DRPs identified will be captured and those containing non-Co-60 plant-related rad ionuclides will be sent to an off-site laboratory for full suite radionuclide anal ys is.
21 The detai led investigatio n process, in cluding the isolation and co llection of DRPs and surrounding so il, is described in Section 3.4.3, Scan investigations, of the DRP Survey Plan.
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ZionSolutions, LLC ZS-2022-010 Attachment
- If a DRP was captured in an investigative so il sample, rescan the sample void using the hand-held Nal detector to verify that the location has been successfu ll y remediated.
- If additional elevated readings are enco untered, co llect additional sampl es fo r screenin g, as described above.
Hand Scanning Areas inaccess ible to the towed array were surveyed using hand-scanning methods. The protoco ls for gamma scanning with hand -held detectors are delineated in the DRP Survey Plan and summarized below:
- Technicians w ill scan slowly (0 .25 m/sec or slower) in a serpentine fas hi on w hil e maintaining the detector end cap no more th an 2" from th e soil surface.
- Techn icians wi ll pause during the survey when the audible outp ut signal from the detector indicates elevated activity, such as from the presence of suspect DRPs .
- The investigation level for hand-held scannin g is minimum detectable count rate (MDCR) p lu s background. This investigati on level is a secondary consideration to the monitoring for variation of detector audio output.
In the event that e le vated activity was detected by hand scannin g, a detailed investigation, as described in the previous section, would be conducted.
Systematic Soil Sampling ZionSolutions designed a systematic soil sampling plan as recommended by NRC staff in RAi-l 0, Specific Co nsideration 2a, to augment the surveys described above. The sampling plan (described in detail in the DRP Survey Plan) is intended to prov ide add itiona l confidence that potential DRPs have been identified and remediated by selecting areas for anal ysis that have not been identified by scanning as containing elevated activity. This samp ling plan uses a
" presence/absence" surv ey design to select add itional survey areas for detailed investigation.
This investigation suppl ements the investigatory samp ling co nducted in areas of elevated activity.
The area of interest (the 36 survey units) was divided into 103,529 grid cell s l m 2 in size. Grid eelI sizes for presence/absence survey design correspond to the footprint of the samp ling methodology; in th is case, the sampling footprint is a 1 m 2 area where 5 total soi l samples were col lected. For each grid cell , l sample was co llected at the center of the grid ce ll and 4 samples were collected at each of the cardinal directions (N, S, E, W) 0.5 m eq uidi stant from the center sample.
ZionSolutions samp led 155 grid cells using th is approach . V isual Sample Plan (VSP), a software tool for survey design and data assessment used to design the presence/absence samp ling plan ,
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment determined that if 155 of the 103,529 grid cell s are sampled and 3 or fewer of the 155 sampled grid cell s co ntain DRPs, then there will be at least a 95.4% confidence that at least 95% of the grid ce ll s do not co nta in DRPs . A dditi onally, if no more than 0.5% of the grid ce ll s in th e population are assumed to contain DRPs, then there wi ll be no more than a 0.8% probability of conclud ing that the popul ation co nta ins DRPs.
Estimate of DRP Risk The exposures from the inhalation, ingestion , and skin exposure ( includi ng the effective dose equiva lent) of the hypothetical DRP source term are treated as LLBP scenari os due to their low probability of occurrence. Treating the low-probability DRP exposure as an LLBP scenario is cons istent w ith the approach approved in the Zion L TP for assess ing the low-probabi lity scenario of the we ll driller contacting the A uxili ary Building drains, whi ch was also designated as an LLBP scenario.
In accordance with NUREG-17 57, the evaluation of LLBP exposure scenarios ensures that
" unacceptably high ri ks would not result," but are not cons idered compl iance scenarios .
Accordingly, the dose from the hypothetica l DRPs will not be added to the Z ion compliance dose. Rather, the hypothetical DRP dose will be used to better risk inform the decision to terminate the license.
An unacceptably high risk is viewed as that correspondin g to the public dose limit of 100 mrem/year TEDE whi ch represents a lifetime fata l cancer risk22 of 4x10* 3 . Issued in support of the promulgation of the license termination rul e (LTR), SECY-97-046A states that the fatal cancer risk corresponding to the 25 mrem/year unrestricted use criterion is an order of magnitude lower at 4x10* 4 and that this risk is estimated ass umin g a risk coefficient of 5x10-4 per rem and a 30-year lifet ime expos ure.
To justify the designation of the hypothetical DRP exposure pathway as an LLBP scenario, the probabilities of DRP ingestion and inhal ation were compared to the probability of drilling into the Auxi lia ry Building drains, which was accepted by NRC as an LLBP scenario in the Zion LTP. The probability of a drill contacting the Aux iliary Building drains was calculated to be l.Sx 10*3 for a single well drill ed on the ite.
The probability of a future site resident ingesting or inhaling a single DRP i much lower than drilling into an A ux iliary Building drain ; ZionSolutions has calculated these probabilities to be l.6xl0* 8 and l.7xlo* 10 , respectively,23 assuming a sing le DRP is present. The site resident is assumed to occupy the site for a 30-year period in accordance with SECY-97-046A.
22 SECY-97-046A, "Final Rule on Radiological Criteria for Licen e Termination," March 3 1, 1997.
23 See the response to RAJ- I 0, Specific Consideration 3b, below, for the calculation of these probabilities.
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment The expectation dose is calculated by multip lying the probability of inhaling or ingesting a particle in a given year by the dose from the particle 12 . Inhalation and ingestion effective dose equivalents have been calcu lated for particles w ith Co-60 or Cs-1 3 7 that correspond to the 50 th percentile a posteriori MD As. The final lifetime probability of a sing le DRP being deposited in the ski n is I .2x I 0-7 _ The DRP direct skin exposu re effective dose equiva lents were ca lcul ated using the EPRJ 1002823 guidance. This guidance allows for direct comparison to the license tem1ination criteria of 25 mrem TEDE/yr assum in g that the exposure will occur (i .e., ignoring the low probability of an exposure event).
The dose to the average member of th e critica l gro up from DRP exposure is a low probability, once in a lifetime event, as compared to the assum ed 30-year li fetime exposure from di sperse source terms such as soi l. Therefo re, the dose (TEDE) from the hypothetical DRP wi ll be multiplied by the risk coefficient app li ed in SECY-97-046A, i.e. , 5x10-4 per rem, an d compared to the risk of 4xl 0- 4 that represents the 25 mrem/year unrestricted use criterion. If the ri sks from the LLBP DRP ingestion and inhalation expos ure scenarios are below 4x10-4, they are not considered un acceptably high.
NRC SPECIFIC CONSIDERATION 1:
The NRC staff offers the following information relevant to scan sensitivity of survey instruments for surveying the Zion discrete radioactive particles:
NRC SPECIFIC CONSIDERATION la:
The results of the limited-scope NRC confirmatory survey in April 2021 identified three types of discrete radioactive particles at the site: (1) cobalt-60 primarily, with other activation products, in the form of activated metal; (2) potentially activated bioshield concrete; and (3) potentially irradiated fuel fragments . One of the objectives of scoping for the revised survey should be a determination of an appropriate surrogate ratio that is based on adequate characterization information . For each particle type, consider the use of surrogates for hard-to-detect radionuclides and for the calculation of total activity . In addition, consider how differences in radionuclide composition of the bioshield concrete and irradiated fuel fragments would be taken into account for calculating the scan MDAs. Relevant information from the licensee 's RAI respon ses to the NRC letter dated August 19, 2021 (ADAMS Accession No. ML2 l 231Al 87) should also be taken into account.
ZIONSOLUTIONS RESPONSE:
A survey plan, the "Survey Plan fo r Discrete Radioactive Particle Identification and Remediation," ZS-LT-07 , Revision 1 (the "DRP Survey Plan"), was designed specifically for detecting and removing discrete radioactive particles. The DRP Survey Plan is included as part of the ZionSolutions response to RAI-10.
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ZionSolutions, LLC ZS-2022-010 Attachment In preparation for performing the DRP scan, each of the six 2"X2" NaJ detectors to be used for the towed array was calibrated using two NIST-traceable point sources, Cs- 137, whic h is an HTD surrogate, and Co-60 . The calibrati on involved the detem1ination of detection efficiency versus distance, x , between th e sources and the detector ranging from contact to approximately 20 inches. As part of the y tern capability eva luation, a mathemati ca l Monte Carlo model wa developed to determine a di stribution of detecti on efficien~ies and MDAs for DRPs while vary ing the 3-dimensional hypothetica l particle locations relative to the detectors. The model uses a curve-fit of the calibration efficiency (E) data (from 4 of the lowest efficiency detectors for the a posteriori evaluation) of the following mathematical form to determine the mean detection efficiency during each collection interval (l sec):
Equation 8 - Calibration Efficiency The DRP Survey Plan addresses the need to account for HTD nuclides in Section 3.5, Data Evaluation:
Transuranic hard-to-detect (HTD) radionuc lides will be determined by ratio to Am-241 , and other HTD radionuclides wi ll be determined by ratio to Cs-137, based on the ratios identified in particle S0126 identified by ORJSE during the Apri l 2021 survey.
We believe that the efficiency and MDA distributions for Cs-1 37 are reasonably representative of other gamma-emitting radi onuclides that may be present in DRPs given the moderate gamma energy range of Cs-137 compared to these other radionuclides.
Those portions of the responses to the NRC's August 19, 2021, Request for Additional Info rmation that are relevant have been incorporated into the DRP Survey Plan and are called out here as necessary.
NRC SPECIFIC CONSIDERATION lb:
For estimating the revised scan sensitivity of the survey instruments, expressed as a scan MDA, the scan MDA equation should be adjusted for a decreased observation interval for a particle in comparison to a diffuse source of residual radioactivity.
ZIONSOLUTIONS RESPONSE:
The detection efficiency and MDA model developed for the towed-array account for the scan observation interval (1 sec) used for the scan survey conducted at a nominal transit velocity not to exceed 0.6 m/sec (1.34 mph). The a priori MDAs for the towed array are described in Section 3.4.1 , Gamma Scan Survey with Towed Array, of the DRP Survey Plan . The detail s of system calibration and the sensitivity are described in TSD 21-001, Revision 2, "Calibration and Discrete Radioactive Particle Detection Sensitivity and Performance Assessment for a Ludlum Page 52 of 96
ZionSolutions, LLC ZS-2022-010 Attachment 44-10 Six-Detector Array." The calculated 50 th percentile a priori MDA values from TSD 21 -
001 , the post-process (a posteriori) data assessment sensitivity based on a seven sigma criterion, and the array drive-over tests are shown in the following table.
The Ai-ray Drive-Over Test. A n addi tiona l empirical test was performed to demonstrate the abi lity of the towed array to detect actual elevated activity items th at were collected durin g prior survey activ iti es at Zion . The Co-60 activity of the DRPs were determined by laboratory gamma spectroscopy ana lys is. The items were se lected based on the clo eness of their activ iti es to the calculated a priori MDAs. One piece of elevated activity concrete rubble (L l-12203B-FJGS-2 1 l-CV) and 2 DRPs (LI-12112A-FJGS-21 l-DP and LI-12113 A-FJGS-2 1 l-DP) were selected for this eva luation. These item s were analyzed by gamma spectroscopy at GEL Laboratories.
The tests were conducted on-site in actual field conditions. The items were placed one at a time onto the ground and the array was dri ven over the target item. The three items used in the test were successfully located by the system operator during the live time monitoring. The file s were then post-processed usin g off-the-shelf ESRI ARCMap 10.8 GTS software for data analysis and reporting.
An assessment was also done of the DRP detection sensitivity for the identificati on of potential locations for follow-up investigations using Arc-GIS post-processing. The results of the data interpretati on using Arc-GIS for two of the three items showed th at the system can identify the presence of these particles during a scan array survey with these DRPs at the ground surface.
Item s Ll-12203B-FJGS-21 l-CVand LI-12112A-FJGS-211-DP were detected in the post-process ing anal ys is.
The third item (Sample LI-12113A-FJGS-21 l-DP) was not identified during post-processing.
This particle was determined to have 0.08 µCi of Co-60 by laboratory gamma spectroscopy, which is 20% below the activity of particle LI-12112A-FJGS-21 l-DP . The likely cause of the missed detection was the position of the particle relative to the start of the I-second acquisition,
- t. For example, if t2 (the probabilistic time from detector array centerline to end count end-time) were at or near zero, the detection efficiency would be at a low value potentially causing a non-detection .
The detection of item LI-12112A-FJGS-211-DP with an activity of0.10 µ Ci is close to the theoretical predictions of both the probabili stic model and the post-survey data assessment.
This test clearly shows that the system is able to detect DRPs of 0.10 µCi of Co-60 and 0.04 µCi of Cs-13 7. Both of these values are below the a posteriori MDC . The activity and the corresponding doses of these detected particles well below the activity of dose significant particles.
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment Table 9- DRP Detection Sensitivity
'=--------.-----------,
Co-60 Sensitivity Cs-137 Sensitivity Methodology
(µ.Ci) (µ.Ci) a priori Probabil istic Model , sot1, Percenti le 0.06 0.15 MDA Post-Process data Assessment, 7 sigma 0.12 0.41 Array Drive-Over Test 0.10 0.04 NRC SPECIFIC CONSIDERATION le:
The detector speed over the land surface during the survey (e.g., 0.25 meter per second or other value) and the transect width of the survey path should be factored into the scan MDA calculation and the survey design, accordingly. !
ZIONSOLUTJONS RESPONSE:
The range of detector speeds and the transect width of the survey path have been factored into the scan MDA as probab ili stic parameters as described in the DRP Survey Plan and in TSD 21-001. In addition, for the a posteriori sensitivity evaluation, we incorporated the detection efficiency, scan speed, and the ranges of detector height from the ground as probabilistic parameters.
NRC SPECIFIC CONSIDERATION ld:
If collimators are used on the detectors, an estimate of the change in detector response (e.g., axial response and reduced background), as well as how the collimated detectors are addressed in the survey plan and scan MDA equation, should be considered. Additional factors , such as a shorter observation interval as noted in item I B above, should be considered for estimating the revised scan MDA if detectors with collimators are used for the survey .
ZIONSOLUTJONS RESPONSE:
As described in the DRP Survey Plan, collimators were not used during scanning.
NRC SPECIFIC CONSIDERATION le:
The method for calculating the efficiency of the detector should be described in the survey plan .
If collimators are used on the detectors, the calculation method should account for the detector response, as noted in item ID above.
ZIONSOLUTJONS RESPONSE:
TSD 21 -001 provides a summary of the methods for determining the mean detector efficiency distributions for calibration and assessment of the system performance. The a priori analysis Page 54 of96
ZionSolutions, LLC ZS-2022-0 10 Attachment model used the mean of al l detector effic iencies fo r each distance whereas the a posteriori model used the four lowest detector efficienci es as a conservative estim ate of system sens itivity.
Col limators were not used on the detectors.
NRC SPECIFIC CONSIDERATION lf:
A range of scan sensitivities for discrete radioactive particles located between the land surface and six inches or deeper below the land surface should be considered in the survey design. The assumed depth of particles informing the survey design should take into account the likely actual depth of the particles given the site history and prior survey results. For example, a *'worst-case" scan MDA may be calculated for discrete radioactive particles located at 6 inches or deeper below the land surface, and/or the depth below which a discrete radioactive particle of nominal activity cannot be detected. Then, an upper bound on the range of scan sensitivity and discrete radioactive particle detection may be calculated as a '"best-case" scan MDA, where the discrete radioactive particle is located on the land surface.
ZIONSOLUTIONS RESPONSE:
To estimate the effect of increased DRP depth in so il , Microshield v8.03 was used to calculate relative reduction/attenuation factors by modeling a point source for various distances and ratioing the results to the DRP location on the ground surface at a distance to the detector's centerli ne of 4 inches for only Cs-137. Co-60 was not used in the assessme nt, because the factors wou ld be less conservative due to Co-60 ' s higher gamma energy. The analysis modeled soil as concrete with a density of 1.6 glee and the dose rates used to determine the reduction factor associated w ith gamma ray build-up. The resu lts of the ana lysis are summarized in the table below.
Table I 0- Cs-13 7 Response Reduction at Depth Distance Cs-137 Below the Response Surface (in) Reduction Factor 1 2.6 2 4.0 4 8.0 6 16.2 8 32.2 10 59.3 12 101.0 This ana lysis shows that for a DRP at 6 inches below the surface , the detector' s efficiency wi ll decrease by a factor of 16, resu lting in an increase in the DRP MDA by the same factor for Cs-13 7. These reduction factors can be applied to the MDA distribution for Cs-13 7 to assess the Page 55 of 96
ZionSolutions, LLC ZS-2022-0 l 0 Attachment overall impact of DRPs MD As below the soil surface . Thi s range includes MD As fro m "worst-case" to " best-case."
NRC SPECIFIC CONSIDERATION lg:
The survey protoco l should consider how the surveyor will pause during the survey, using the output signal from the detector to identify suspect discrete radioactive particles. Also, the survey protocol should consider the investigation level as a second stage, in units of counts per minute above the background count rate .
ZIONSOLUTIONS RESPONSE:
The towed array is des igned to operate in a continuous manner, and as such th e survey protoco l does not account fo r an operator to pause based on output signal.
100% of th e accessible surface area of th e survey units listed in th e DRP urvey Plan were scanned using the towed array. Areas inaccess ible to the towed array were surveyed using hand-scanning methods.
The fo ll owing protoco ls for gamma scanning with hand-held detectors are delineated in the DRP Survey Plan :
- Technicians w ill scan slowly (0.25 m/sec or slower) in a serpentine fas hi on while maintaining th e detector end cap no more th an 2" from the so il surface .
- Collimato rs w ill not be utili zed.
- Technicians w ill pause during the survey when the audible output signal fro m the detector indicates elevated activi ty, such as from the presence of suspect DRPs.
- The investi gation leve l fo r hand-held scanning is minimum detectable count rate (MDC R) plus backgro und , but thi s investi gation level is a secondary consideration to the monitorin g for variation of detector audio output.
NRC SPECIFIC CONSIDERATION lb:
In addition to surveyors monitoring survey instrument physical meter movements and pre-set alarms, the existing NRC guidance on survey techniques recommends the use of additional methods to improve the human performance factors , such as headphones, to aid the surveyor' s efficiency and ability to identify areas of concern when performing surveys. The revised survey plan should consider the use of headphones or other means for improving the surveyor performance for detecting discrete particles or other areas of concern.
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ZionSolutions, LLC ZS-2022-010 Attachment ZIONSOLUTIONS RESPONSE:
Instrument headphones were not uti lized under the DRP Survey Plan , because the detectors used in the survey, Model 2350-ls, do not have headphone jacks. ZionSolutions instructed technicians, as part of the training for the DRP Survey Pl an, to cl osely mon itor the audib le output from the instrument. Zi onSolutions believes th at beca use D&D operations are no longer in progress and the background noise at th e site is nominal (normal environmental ambient level s),
technician s w ill be easil y able to detect chan ges in audibl e output.
NRC SPECIFIC CONSIDERATION li:
Personnel training should be considered to ensure that surveyors can achieve the performance bases of the survey protocol (e.g., the ass igned surveyor efficiency, maintaining detector distance to the land surface at the assigned scan speed, etc .).
ZIONSOLUTIONS RESPONSE:
ZionSolutions conducted personnel training for each surveyor who participated in the implementation of the DRP Survey Plan . Ind ividuals performing field survey and sampling acti vities and reviewing co llected data from field measurements or laboratory data reports were trained in the use of instruments, devices, and procedures, as app licable to the tasks they wi ll be performing.
Operators of the towed array are trained to operate the vehicle at a constant speed, not to exceed 0.6 m/sec (1.34 mph). The detector to ground distance remains nominall y con stant, and variabi lity is accounted for as a probabilistic parameter. For hand scanning, prior to being qualified, a technician was observed by a subject matter expert during training to verify that they are maintaining the correct scan speed and detector di stance spec ific to hand scanning in the DRP Survey Plan (maxi mu m 0.25 m/sec and maximum 2" from surface) .
NRC SPECIFIC CONSIDERATION 2:
The NRC staff offers the following considerations for developing a revised sample collection and laboratory analysis procedure relevant to the Zion di screte radioactive particles to be collected during the surveys:
NRC SPECIFIC CONSIDERATION 2a:
A systematic soil sampling plan should take into account a chosen confidence level for the purpose of performing statistical tests to determine what proportions of the investigation areas are impacted/not impacted by the presence of discrete radioactive particles and below the scan sensiti vity of the survey.
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ZionSolutions, LLC ZS-2022-010 Attachment ZIONSOLUTIONS RESPONSE:
A systematic soi l sampling plan was developed in the DRP Survey Plan that utili zed a "presence/absence" survey des ign . The area of interest (36 survey units denoted in Ta ble 3 of the DRP Survey Plan) wa divided into 103,529 grid cell s 1 m2 in size . Gr id ce ll izes for presence/absence survey design correspond to the footpr int of the sampling methodo logy; in thi case, the sampling foo tprint is the I m 2 area where 5 total so il samples w ill be collected. For each grid ce ll , 1 samp le was co ll ected at th e center of th e grid ce ll and 4 sample were co llected at each of the cardinal directions (N, S, E, W) 0.5 m equidi stant from the center sample.
Visual Sample Plan (VSP), a software tool for survey design and data assessment that was used to design the DRP Survey Pl an, determined that if 155 of the 103,529 grid ce ll s are sampled and 3 or fewer of th e 15 5 ampled grid cell s co nta in DRPs, then there will be at least a 95.4%
confidence that at least 95% of the grid ce ll s do not contain DRPs. Additionally, if no more than 0.5% of the grid cell s in the population contain DRPs, then there will be no more than a 0.8%
probability of concluding that the population contains DRPs (i.e., observing more than 3 grid cells assumed to contain DRPs in the sample size of 155).
NRC SPECIFIC CONSIDERATION 2b:
The revised sample collection procedures should consider how discrete radioactive particles will be isolated and collected during the survey. In addition, this procedure should consider the process used for collecting soil around any discrete radioactive particles identified, and separate laboratory analyses of those soils.
ZIO SOLUTIONS RESPO SE:
Elevated Activity Investigations. Detailed investi gati ons were performed any time the investigation level was exceeded durin g the scan survey. The detailed investigation process, including the isolation and collection of DRPs and surrounding soil, is described in Section 3.4.3, Scan Investigations, of the DRP Survey Plan and summarized below :
- Scan the elevated area us ing a hand-h eld Nal detector to locate the precise area of the elevated activity. Mark the location in the field with a flag or similar. If the area of elevated activ ity cannot be dupli cated, then make a notati on in the field notes and no further actions are necessary.
- If an area of elevated activity is detected, obtain a measurement using a portable gamma spectroscopy instrument and a 10-minute count.
- If a plant-re lated radionuclide is identified, collect a soil sample in the location down to a depth of 12 inches, capturing at least 2 liters of so il. This w ill remediate the potential DRP .
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment
- If the sampl e has been detected in an area of elevated backgro und, notify the rad iological engineer to consider moving the sample to an area of lower backgro und for further ana lys is.
- Spread the oil samp le out into a pan or other appropriate conta iner to an approx im ate 1-inch thickne s. Use the hand-h eld al detector to try to iso late a potential DRP .
o If no DRP is identified denote as such in the field notes . No further action is required .
o If a DRP containing only Co-60 is identified, capture the DRP and archive the sa mple. No further action is required.
o If a DRP contain ing an y non-Co-60 plant-re lated radionuc lides is identified , then capture the DRP and send the sample to GEL Laboratories fo r full suite radio nuclide analysis.
- If a DRP wa captured in an in estigative oil ample, rescan the sample void using the han d-held Nal detector to verify that the location has been successfull y remediated.
o If additi onal elevated readin gs are encountered, co ll ect add iti onal samples for screenin g, as described above.
Systematic Soil Sampling Plan. The fo llowing process will be used to sc ree n systematic samples:
- If the sample has been detected in an area of elevated background, notify the radiological engineer to co nsider mov ing th e sa mple to an area of lower backgro und for further ana lys is.
- Spread each of the five soil samp les out to an approximate I-inch thickness . In order to ensure the location from whi ch th e sample was taken, carefully segregate each of the five piles from one another. Use a hand-held Nal detector (with the protoco ls outlined in Section 3.4.2 of the Survey Plan) to try to iso late a potential DRP .
- If no elevated area/p otential DRP is identified , denote as such in the fie ld notes . Place the soil back in the ho le and no further action is required.
- If an elevated area/potential DRP is identified, obtai n a measurement using a portable gamma spectroscopy instrument and a I 0-minute count.
o If plant-related rad ionuclides are not identified, den ote the naturally occ urrin g radioactive material radionuclides in the fie ld notes. Place th e soi l back in the hole and no further action is required .
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ZionSolutions, LLC ZS-2022-010 Attachment o If the portable gamma spectroscopy instrument id entifies plant-related radionu clides, then collect the so il in an appropriate container, remedi ating the potential DRP.
- If o nl y Co-60 is identifi ed by the portab le ga mma spectroscopy instrum ent, den ote as such in the field notes and archive the samp le.
- If any non-Co-60 plant-related radio nu clides are identified by the portable gamma spectroscopy instrument, the sample w ill be sent to GEL Laboratories fo r ful l suite radionuclide analysis.
- If a DRP was captured in a soi l sample, rescan the sample void using the hand-held Nal detector to verify that the location has been successfully remediated.
o If add itiona l elevated readings are encountered, co llect add itional soi l material for screening, as described above.
Justification for use of the Portable Gamma Spectroscopy Instrument. The use of a portable gamma spectroscopy instrument to investigate elevated gam ma scan readings is an industry standard that has been used in numerous past decommissioning projects . Qualitative measurements obtai ned by the instrument can provide real -time indications in the field of whether an e levated reading is due to plant-related radioactivity or NORM. A lthough there may be concerns that some NORM (e.g. , K-40) may mask plant-related gamma emi tters such as Cs-137, this would not be an issue w hen implementing the DRP survey . During a standard FSS of a land survey unit, w here the release criteria are typ ically established at near backgrou nd levels, it may be possible for K -40 to mask low levels of Cs-137 . However, during the DRP survey, the portable gamma spectroscopy instrument wou ld have sufficient sensitivity to detect DRPs that co uld pose un acceptably hi gh risks to a future occupant of the site.
The effectiveness of the portable gamm a spectroscopy instrum ent in detecti ng DRPs was validated using actual DRPs in an empirical investigation. This empirical study is documented in TSD 21-00 1, " Calibration and Discrete Radioactive Particle Detection Sensitivity and Performance Assessment for a Ludlum 44-10 Six-Detector Array." In this investigation the portable gamma spectrometer was shown to be capable of identify ing plant-related rad ionuclides from dose significant particles within a background contai nin g naturall y occurring radionuclides.
NRC SPECIFIC CONSIDERATION 2c:
Revised sample collection procedures and planned laboratory analyses for discrete radioactive particles found during the survey should consider additional identification measures, such as labeling of sample containers with discrete radioactive particles, for the protection of laboratory personnel .
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ZionSolutions, LLC ZS-2022-010 Attachment ZIONSOLUT/ONS RESPONSE:
Samples containi ng DRPs were properly labe led as such on the chain of custody form for the protection of laboratory personnel. ZionSolutions fo rm all y notified GEL La boratories that every sample they received durin g the implementation of the DRP Survey Plan contained a DRP . Thi s notification enabled GEL Laboratories personne l to implement th e appropr iate internal procedures to ensure protection of their personnel.
NRC SPECIFIC CONSIDERATION 2d:
Revised laboratory analysis procedures should consider the radionuclide composition and radioactivity levels of the discrete radioactive particles, taking into account relevant information from the licensee 's RAJ responses to the NRC letter dated August 19, 2021 (ADAMS Accession No. ML2 I 23 I A 187). The licensee should direct laboratory analyses to include the range of radionuclides potentially present based on operational and decommissioning history, and not rely solely on the radionuclide compositions identified in the limited-scope April 2021 survey.
ZIONSOLUTIONS RESPONSE:
Because the DRP Survey Plan was des igned to identify and retrieve DRPs and not compare quantitative results to release criteria, determining the concentrations of radioactivity in each sample is not necessary to demonstrate compliance with 10 CFR 20. However, any identified DRPs were sent to G L Laboratories for gamma spectroscopy analysis. No fuel-fragment particles have been identified in executin g the DRP Survey Plan.
The process for identifying the rad ionuclides potenti all y present at Zion is summarized in the ZionSolutions' response to RAI-3a. Z ionSolutions re lied upon operationa l and decommissioning history at Zion (including samples coll ected at the site) and industry reference material to develop the radionuc lides of concern (ROC) lists that are contained in TSD 11-001 , "Potential Radionuclides of Concern During the Decommissioning of the Zion Station ," and TSD 14-01 9, "Radionuclides of Concern for Soil and Basement Fill Model Source Terms."
The information in the TSDs identified above is further informed by the results of the limited-scope April 2021 inspection survey. Taken together, these analyses (as documented in the cited TSDs and ORISE report) provide the basis for defining the approach in the DRP Survey Plan, which is submi tted as part of this response to RAI-10. They are also re lied upon in the formulation of the approach for developing a dose estimate for DRPs as described below in ZionSolutions' response to Specific Consideration 3. The data from the ORJSE report receives additional emphas is in the dose fo rmul ation because it is the only data that exists regardin g certain DRPs (i.e., fuel fragments) .
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ZionSolutions, LLC ZS-2022-010 Attachment NRC SPECIFIC CONSIDERATION 2e:
In addition to the radioanalytical procedures described above, the licensee should consider obtaining information on the physical and chemical characterization of collected discrete radioactive particles that are relevant to internal dosimetry calculations (e.g., the size of each particle, as well as the chemical solubility in simulated lung and digestive-tract fluids). Note that in the absence of specific information on discrete radioactive particle size and solubility characteristics, default assumptions from ICRP-30 (i.e .,fl values and inhalation class) are applied for internal dose calculations.
ZIONSOLUTIONS RESPONSE:
ZionSolutions does not propose to subj ect samples to chemical analysis. We will use data from literature and, when necessary, use the default assumptions from ICRP-30 to perform internal dose calculations. Additional detail regarding dose calculations, including the justification for thi s approach , is provided below in the response to Specific Consideration 3b.
ZionSolutions proposes to use alternate Ji values from the literature for insoluble DRPs, including irradiated fuel particles. While we understand that the use of organ dose weighting factors other than those in ICRP-30 would require an exemption, it is our understanding that using alternate Ji values is allowable under 10 CFR 20.
Specifically, 10 CFR 20.1204 (c) states:
When specific information on the physical and biochemical properties of the radionuclides taken into the body or the behavior or the material in an individual is known, the licensee may-(1) Use that information to calculate the committed effective dose equivalent . . .
Our selection ofthefi va lue for Cs-137 and the actinides in estimating the ingestion dose is consistent with the approach used in terminating the Shelwell license, where Dr. Keith Eckerman of Oak Rid ge National Laboratory calculated dose coefficients for insoluble Cs-137. New dose coefficients were needed since the primary NRC sources for this information, Federal Guidance Report No . 11 24 and 10 CFR 20, did not contain coefficients for insoluble Cs-137.
This methodology is also supported by Regulatory Guide 8.9, Acceptable Concepts, Models, Equations, and Assumptions for a Bioassay Program. The use of alternate biokinetic model s is discussed and stated to be acceptable to the NRC. Regulatory Pos ition 4.6 states:
24 "Limiting Va lues Of Radionuclide Intake And A ir Concentration And Dose Conversion Factors For Inhalation, Subm ers ion, And Ingestion," U .S. Env ironmental Protection Agency, Federal Guidance Report No . 11 , 520-1 020, September 198 8.
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ZionSolutions , LLC ZS-2022-01 0 Attachment Individual specific retention and excretion rates may be used in developing biokinetic model s th at differ from the reference man modeling (10 CFR 20.1204(c)). The quality and quantity of data used for thi s type of individual spec ific modeling should be suffic ient to justify the revised model.
NRC SPECIFIC CONSIDERATION 3:
The revised survey plan should consider the following information for developing a dose estimate for discrete radioactive particles at the MDA:
NRC SPECIFIC CONSIDERATION 3a:
Consider the range of potential discrete radioactive particles that were not detected during the survey (below MDA), taking into account the likely radionuclide composition, activity, physical size, depth beneath the surface, and chemical composition. See item IF above for information concerning MDA ranges and detection capability. Also see RAI-1 in the NRC letter dated August 19, 2021 , for additional information on origin of the particles and potential source terms (ADAMS Accession No . ML21231A187). The NRC staff notes that the Zion L TP dose modeling uses dose coefficients from FGR-11 , which is based on ICRP-30.
The information described below for each of the responses to Specific Consideration 3 also wi ll be included in the TSD th at documents the survey results .
ZIONSOLUTIONS RESPONSE:
The DRP Survey Plan provides the a priori MD As for the detection of DRPs that could pose unacceptably hi gh risk to a future occupant on and near the surface. ZionSolutions believes that the a priori MD As described in the DRP Survey Plan are adequate to address the range of potential DRPs not prev iously detected . It has been designed to take into account the range of radionuclide compositi on, activity, physical size, and chemi cal compositi on of potential DRPs remaining at the site. Thi s approach takes into account all potential DRPs regardless of origin.
As stated in the DRP Survey Plan , dose estimates from the particles that may remain at the Zion site after the survey is completed will be documented in a TSD and submitted to the NRC along with the res ults of the surveys . The post-survey TSD will also include an a posteriori probabilistic MDA evaluation using the same parameters in identifying areas for further investigation .
NRC SPECIFIC CONSIDERATION 3b:
Scenarios that should be considered include inhalation, ingestion , and skin exposures to remaining discrete radioactive particles. For inhalation and ingestion, the anticipated particle size ranges should account for particle size change over the 1,000-year compliance period. For ingestion, the technical basis for selection of the fl value (fraction of ingested element absorbed Page 63 of96
Zi onSolutions, LLC ZS-2022-0 l 0 Attachment directly into the body fluids) should be provided, based on the chemical compositions of activated metal , activated bioshield concrete, and irradiated fuel fragments. For skin exposures, the shallow dose equivalent and deep dose equivalent from discrete radioactive particle exposures to the skin for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> should be considered. The calculations should consider the range of cobalt-60 (only) di screte radioactive particles, as well as the radionuclide mixes that comprise activated concrete from the bioshield and irradiated fuel fragments . VARSKfN Version 6.2.1 should be used for these calculations.
ZIONSOLUTION S RESPONSE:
The exposures from the inhalation, ingesti on, and skin exposure of the hypothetical DRP source tenn have been assessed as LLBP scenari os du e to th eir low pro bability of occurrence . Treating the low-pro bability DRP exposure as an LLBP scenari o is consistent with the NRC-approved approach used in the Z ion LTP for assess ing th e low-pro bability scenario of a we ll driller contactin g the Aux ili ary Building dra in s, whi ch was also des ignated as an LLBP scenari o. In accorda nce w ith NUREG-1757, the eva luati on of LLBP expos ure scenari os ensures th at
" un acceptabl y high ri sks would not result," but are not considered compliance scenari os.
Accordingly, the dose from the hypoth eti cal DRPs wi ll not be added to the Z ion compliance dose.
A n un acceptably hi gh ri sk is viewed as th at corresponding to the public dose lim it of 100 mrem/year TEDE which represents a lifetime fatal cancer ri sk of about 4x10-3 . SECY-97-046A also states th at the fatal cancer ri sk corresponding to the 25 mrem/year unrestricted use criteria is an order of magnitude lower at 4x 10-4 and that thi s risk is estimated assumin g a ri sk coeffici ent of 5xl 0-4 per rem and a 30-year lifetime expos ure.
To justify the designation of the hypothetical DRP expos ure pathway as an LLBP scenari o, the pro babilities of DRP ingestion and inhalation are compared to th e probability of drilling into the Aux il iary Building drain s, w hich was accepted by NRC as an LLBP scenari o in the Z ion LTP .
The pro bability of a drill contacting th e Auxiliary Building drains is 1.5x 10-3 for a single we ll drilled on the site as calculated by the equ ation below.
E quation 9 - Probability ofA uxiliary Building Drain Contact by Drilling SA drain Pdra in = A CZ Where :
P drain = probability of drill contacting Aux iliary Building drain SA drain = projected surface area of Auxili ary Building drains (96.2 m2)
A c== area of contaminated zone (64,500 ni)
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment The probability of a fu ture site res ident ingestin g or inha ling a sing le DRP at l.6x I o*8 and l .7x l 0* 10, respective ly, is much lower th an drillin g into an Aux iliary Building drain. The pro bability of a particle ingestion and inhalat ion from th e Z ion end state is calcul ated using the eq uati on below. The res ident is assum ed to occupy the site fo r a 30-year peri od in accordan ce w ith SECY 046A.
Equ ation JO- Probability of Single Particle Inhalation and Ingestion 301R5 Where:
PnRP = pro bability of ingesting or inha ling one DRP
!Rs= so il mass ingesti on rate (18 .3 g/y) or inhalation rate 0.2 (g/y)
Ac== area of Z ion contaminated zone (64,500 m 2) le== thi ckness of soil layer affected by DRP (0.3048 m)
CFcm3/m3 = co nversion factor (l .00E+06 cm 3/m 3) ds = density of so il (1.8 g/cm 3) (see LTP 5.8.4.4) 30 = 30-year lifetim e exposure peri od to the average member of th e criti ca l group per SECY-97-04A The fi nal pro bability of DRP inhalation and ingesti on exposure is calcul ated by multipl ying the hypothetical number of DRPs estimated to remain by the single DRP pro bability. As described in the response to Spec ific Consideration 3c, 31 DRPs are estimated to hypotheti cally remain . The fin al lifetime probabili ty of ingestion or inhalation of a DRP is therefore 4.8x l 0*7 and 5.2x l o*9, respectively.
The probability of a DRP being deposited on th e skin during the life tim e of a future site resident is l.2x I0*7 , whi ch is calculated using the equati on below, assuming one DRP rem ains on th e site.
The single DRP p ro bability is multiplied by 3 1, the approximate number of DRPs projected to hypotheti call y remain resultin g in a fin al li fetim e pro bability of 3.7xI0*6 th at a DRP w ill contact the skin of a future site resident. The derm al depos ition param eters in the equation are from the EPA ' s Risk Assessment Guidance for Superfund .25 25 "Risk Assessment Guidance fo r Su perfund Vo lume I: Human Hea lth Evaluatio n Manu al, Part E, Suppl ementa l Guidance for Dermal Risk Assessment," U.S. Environm ental Protection Agency, EPA/540/R/99/005 , E xhibit 3-5, July 2004.
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ZionSolutions, LLC ZS-2022-010 Attachment Equation 11 - Probability of Single Particle Skin Deposition M skinTe PoRP Where:
PoR.P = lifetime probability of skin ex pos ure to ass umin g one DRP present on site Acz = area of Zion contaminated zone (64,500 m 2) tcz = thickness of soi l layer affected by DRP (0.3048 m)
CFcm3/m3 = conversion factor (1.00E+06 cm 3/m 3) ds = density of soi l (1.8 g/cm 3)
Te= time that res ident occupi es the site (30 y)
M skin = mass loading of soil on skin (g)
Where: M skin = f skin m ass loading event£ f event f re quen cy A f soil CFg / mgA skin fskin mass loading event = mass loadin g frequency (1 event/d)
Efevent frequency= frequency of event per year (350 d/y)
Afsoil = so il adherence facto r fo r resident gardener (0.07 mg/cm 2)
CFg;mg = conversion factor (l .00E-0 3 g/mg)
Askin= skin surface area (5 ,700 cm 2)
The dose to the average member of the critica l group fro m DRP exposure is a low probability, once in a lifetime event, as compared to the ass um ed 30-year lifetime exposure from di sperse source terms such as soil. Therefore, the dose (TEDE, CEDE, or EDE) from the hypothetical DRP wi ll be multiplied by the fatal cancer risk coefficient app lied in SECY-97-046A , i.e., 5x10-4 per rem, and compared to the risk of 4x10- 4 that represents the 25 mrem/year unrestricted use criterion. If the risks from the LLBP DRP ingestion and inhalation exposure scenarios are below 4x10-4, they are not considered unacceptab ly high.
In order to provide a comprehensive and thorough evaluation of the potential dose to future occupants from DRPs in the end state land areas, we have evaluated potential doses associated with particles at the 50th percentile a posteriori MD As of the towed scanning array of 0.1 2 µCi Co-60 and 0.41 µCi Cs- 137. The 50th percentile MDA was chosen because it represents the median and most likely detectab le particle activities that would be enco untered and thus the most likely doses that wo uld result from exposure to DRPs.
The exposure pathways evaluated include:
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment
- 1. Estimated particle sizes at the 50 th percentile MDAs, and potential doses from ingestion of large non-respirable particles with activities scaled to the 50 th percentile MD As to account for hard-to-detect radionuclides that may be present.
- 2. Fractionation of 50 th percenti le particles to 1 µrn AMAD and calcu lated activities and inhalation doses from the smaller particles.
- 3. Complete dissolution of the 50 th percentile MDA particles and the resulting localized distributed soil concentrations, and potential doses using newly calculated area factors and DCGLEMCS for the nuclides of concern in the particles.
- 4. Potential shallow, deep dose equivalents, effective dose equivalents (EDE) for particles on the skin with a 24-hour exposure period at the scaled 50 th percenti le MDA activities .
DRP Size Estimates Particle sizes are estimated for each of the DRP types that have been detected: activated steel ,
activated concrete, and irradiated fuel. ln addition, anticipated particles sizes accounti ng for changes in size over the 1,000-year compliance period have been estimated.
Activated Steel A minimum DRP diameter, de, for activated metal can be calculated using the highest activated source-term from decommissioning activities, which is well represented by the activation calculations of the concentrations of the reactor vessel internals. 26 The table below summarizes the Co-60 concentrations, Cco-60, for the various reactor internals components for each of the two reactors as of January 1, 2021. This shows that the highest concentrations are from the baffle plates in Unit 1 as 4.06E-02 Ci/cc or 4.06E+ 10 pCi/cc.
26 WMG 07-046D-RE-088 , "Zion Units 1 and 2 Activation Analysis and Component Characterization," January 2008 .
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ZionSolutions, LLC ZS-2022-010 Attachment Table 11 - Reacto r Internal Component Activities Unit 1 Cco-60 Unit 2 Cco-60 Component (Ci/cc) (Ci/cc)
Upper Core Plate 1. lSE-03 l.84E-05 Lower Core Barrel 1.78£ -03 1.73£-03 Thermal Shi eld 2.60E-04 2.52E-04 Baffle Plates 4.06E-02 3.98E-02 Baffle Formers 2.92E-02 2.84E-02 Lower Core P late l .03E-02 l.0lE-02 Balance of Lowers l.67E-04 l.64E-04 Vessel Wa ll 1.55E-06 9.S0E-08 Vessel Clad 5.61E-05 5.48E-0 5 The maximum concentration from the above tab le is for the Unit 1 baffle p late, which is used to estimate a mini mum DRP volume, V, for DRP activiti es corresponding to the 50 th percentile of the a posteriori distribution for the probabilistic parameters fro m TSD 21-001 Rev . 2 using the fo llowing:
Equation 12 - DRP Volume Corresp onding to the SO'h Percentile a posteriori Distribution MDAso,co-6o(pCi)
V(cc) pCi Cco-6o(cc)
Using the above, with the Unit l baffle plate concentration of 4.06E-02 Ci/cc, the DRP volume for 50 th percentile scan MDA activity (0 .12 µCi Co-60), the MDA is 2.90E-06 cc. I From this volume, the DRP physical di ameter, de, can be estimated assum ing a spherical geometry using:
Equation 13 - Vo lume of a Sphere V = ~nr3 3
Rearranging yields:
Equation 14 - DRP Physical Diameter Where:
V = the spherica l volume of the DRP based on the concentration in the base material (pC i/cc) and the activity of the DRP (pCi)
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ZionSolutions , LLC ZS-2022-010 Attachment r = the radius of the spherical vo lume of the DRP de= the physical di ameter of th e DRP Using the above eq uati on, the particle diameter fo r the 50 th percentile Co-60 MDA particle diameter is 124 µm .
The equation to calculate aerodynamic eq uiva lent diameter (dae) equivalent to AMAD for a di stributio n of particle sizes weighted by activ ity, from the physical eq ui va lent vo lume di ameter (de) below, is taken from Eq uation 2- 1 on page 2-2 in a report prepared for the NRC .27 Equation 15 -Aerodynamic Equivalent Diameter Where:
dae = the aerodynamic equivalent diameter de = the equivalent volume diameter (physical diameter) of the DRP p = the density of the particle material 8 glee steel, 2.35 glee activated concrete, 10.97 glee uranium d ioxide x = the particle shape factor, usuall y betv,1een 1 and 2. Typical value of 1.5 is used for a spherical geometry Therefore, rea rranging thi s and solving for de yields:
Equation 16 - Phy sical Diameter of 1 µm Particle d, = ft 1 µm dae The sperical volume of 1 µm particle, V(l µm dae), is calculated using the fo llowing:
Equation 17 - Spherical Volume of 1 pm Particle
= 34rr (de) 3 V(1µm dae) 2 Therefore, the intact particle aerodynamic equivalent di ameter for an 8 glee density sphere with a 1.5 shape factor for the 50 th percentile is 28 7 µm , respectively. Thus, intact particles detected at the MD As far exceed the 10 µm respirable particle threshold . Also, since the particle would not likely be truly spherical the median aerodynamic diameter could be substantially larger.
27 "Airborne Particle Resuspension and Inhalation Radiological Dose Estimation Following Volcanic Events,"
prepared fo r U. S. uclear Regulatory Commi ss ion , Contract NRC- 02-07-006 , September 2011 .
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ZionSolutions, LLC ZS-2022-010 Attachment The ICRP-30 lung model is based upon l µm AMAD particles. The spherical volume of 1 µm AMAD dae activated steel particle is 4.25E-1 4 cc. The vo lumes and correspondingly the activities of th e 1 micron particles at the 50 th percentil e Co-60 MDA (i.e., 2.90E-06 cc) woul d be reduced by a factor of 8.63E-09, resultin g in a Co-60 partic le activity of l .02E-03 pCi for an equi a lent volume diameter of I µm AMAD. The doses from inhalation of these particles created by fractionation of larger particles at the Co-60 MDAs would be at this activity level and the do es wou ld be insignificant. Thus, even if over time the activated metal particle sizes are reduced to respirable particle sizes, the dose from inhalation would be incon equential.
Activated Concrete Similar to the activated metal , the estimated partic le size of the activated concrete particle SO 124AEu is based on the highest concentration activated concrete detected in the under ves el during characterization (core B102106-CJFCCV-002) of 397 pCilg E u-152 28 . This sample was co ll ected between June 20 12 and January 2013 and is not decay-corrected for the purpose of this analysis. At a concentration of 397 pCilg. the E u-154 activity (344,000 pCi) observed on the SOJ 24AEu particle corresponds to an 867 gram piece of activated concrete. Using a density of 2.35 glee, this is a 369 cc piece of concrete. This is an unreasonably large estimate of the size because it is based on the highest Eu- 152 pCilg activity observed in a concrete core. The core location is from the incore under vessel area floor, which is not necessarily the highest activated concrete present in the concrete surrounding the reactor vessel.
A more reasonable particle size estimate can be made by using the Co-60 data. The highest concentration of Co-60 observed in the activated concrete characterization samples was 1.09E+03 pC i/g in core B102110-CJFCCV-001 28 . The Co-60 level in the particle was 30,000 pCi . At this activity level and assuming a density of2.35 glee the size of thi s particle is 27.5 grams or 11.7 cc. Assu ming a theoretical particle was present with a Co-60 activity equal to the towed array scan MDA, the size of the particle wo uld be 183 grams or 78 cc.
Table 12 - Concrete Particle Size Analysis Co-6 0pCi 30,000 2.00E+0S 50th Percentile Co-60 S204AEu Scan MDA grams 2.75E+0l l .83E+02 cc 1.17E+01 7.81E+01 Particles of this size are not respirabl e. A reductio n in the particle size would produce a correspondin g reduct ion in the particle activ ity. As such, a 1 µm AMAD particle fragment 28 ZionSolutions TSD 14-028, "Radiological Characteri zation Report," Revi sion 0, December 20 I 4.
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ZionSolutions, LLC ZS-2022-01 0 Attachment generated over time from the ori ginal partic les or concrete pieces is likely to contai n minimal activ ity.
Irradiated Fuel Particle For the fuel particle (S0126), the mass of Pu-239 is estimated fro m the reported activ ity (7,450 pCi) along with the specific activity of Pu-239 of 6.2El 0 pCi/g res ulting in a P u mass of 1.22E-07 g. Us ing thi s Pu mass, the fuel mass can be estimated using data from Figure 2, w hich shows 5 kg Pu-239 per to nne of fuel at a two-year irradi ation interval resulting in a fuel mass of 2. 16E-05 g. Using the same meth odology described above and accoun ting fo r the U-238 mass to fu el-mass rati o of0.94 1, this fuel mass corresponds to a physical spherical di ameter of 155 µm and an aerodynam ic equiva lent diameter, dac, of 420 ~* m AMAD using a densi ty of 10.97 g/cc and a shape factor of 1.5 , well above the size considered respirab le.
When the S01 26 radi onuclide mix is scaled to the Cs-137 Scan MDAs, the fo llowing Pu-239 concentrations, particle vo lumes and di ameters res ul t.
Table 13 - Cs-137 S can MDA Irradiated Fuel Particle Size U-238 Particle Sphere S0126 @ Pu-239 Activity Pu-239 U-238 SF Volume Diameter (d.)
MDAs (pCi) Mass (g) Mass (g)
(cc) (µm)
Pu-239 50th 3.15£+04 5.08£-07 1.62£-04 9.02£-05 8.20£-06 1.76£+02 A 1 µm AMAD fue l parti cle has a spherical vo lum e of 2.65E-14 cc. Thus, the activity of a 1 µm AMAD particle derived from a particle at the 50th percenti le Cs- 137 scan MDA would be redu ced by a facto r of l .90E-09.
DRP Internal Dose Analysis As di scussed in the pri or sections, the only likely internal dose pathway from the identified DRPs is from ingestion since the particle size estimate fo r each DRP type is substantially larger than a respi rable size limit of 10 µm . This internal dose analysis is perform ed fo r each of the DRP types identified to date (activated metal, acti vated concrete, and irradiated fue l).
For each parti cle type, we have assumed that each is best represented by the most inso lub le form since the particles have been exposed to weatherin g and have like ly become sta bl e since the particle's creation. A lso, there appears to be no available data withi n the literature for absorpti on of radi onuclides with in the GI tract fo r activated particles (i.e., concrete and steel) but it is reasonable to expect that this absorpti on wil l be very low. However, there is some data for irrad iated fue l fragments as di scussed in more detail below.
Therefore, to represent these inso lub le states, we have selected forms with the lowest value of the parameter that represents absorption from the GI tract (alimentary tract) to the blood stream fo llowing a hypothetical ingestion event. In each case, the calculated intern al dose fo llows the methodology from ICRP-3 0, the basis of the meth ods represented in 10 CFR 20, including the Page 71 of 96
Z ionSolutions, LLC ZS-2022-010 Attachment ti ssue weighting factors. The ingesti on internal doses are calcul ated using IMBA Profess ional Plus Version 4.1.11 using parameters from ICRP-26/30 or directl y fro m Federal Guidance Report N o. 11 (FG Rl 1) as noted in each secti on.
Activated Metal Particle Activities and Doses For the first part of this analysis, we have considered particle number SO124 since it represents the particle with th e hi ghest reported activity of Co-60 fo und by ORIS . In ord er to acco unt for the remainder of the acti vation radionuclides that were not meas ured in the particle assessment, we have sca led these to Co-60 from the mean component activity of the calculati ons of the reactor internals acti vati on. In addition, we th en scaled the Co-60 activities to the 50th percentile of the DRP scan MDA di stribution. The in gesti on dose calculations fo r thi s parti cle are shown in th e tables below. Fo r th is parti cle type we have used the lowest/, value and its corresponding dose conversion factor from FGRl 1.
Table 14 - Activated Metal DRP Scan MDA Activity Activation Particle Activity Activity Activity Scaled to 50 th Nuclide Ratio to Calculation for Percentile MDA Co-60 Ul (Ci) (pCi)
H-3 2.53E+02 2.53E-03 3.04E+02 C-14 3.59E+02 3.59E-03 4.31E+02 Mn-54 2.85E+0 l 2. 85E-04 3.42E+0l Fe-55 7.15E+03 7.14E-02 8.57E+03 Co-60 l.00E+0S l .00E+00 l .20E+0S Ni-59 l. 66E+03 l .66E-02 l .99E+03 Ni-63 2.27E+05 2.27E+00 2.72E+0S Nb-94 5. 54E+00 5.53E-05 6.64E+00 Tc-99 l.18E+00 l.1 7E-05 l .40E+00 Page 72 of 96
ZionSolutions, LLC ZS-2022-0 I 0 Attachment Table 15 -Activated Metal DRP Scan MDA Dose FGR 11 Ingestion Particle Ingestion Dose Nuclide FGR ll/1 Dose Factor Equivalent Scaled to 50 th (mrem/pCi) Percentile MDA (mrem)
H-3 I.00E+00 6.40£-08 l.91E-05 C-14 l.00E+00 2.09£-06 8.84£-04 Mn-54 l.00E-01 2.77£-06 9.32E-05 Fe-55 I.00E-01 6.07E-07 5.llE-03 Co-60 5.00E-02 1.02£ -05 l .20E+00 Ni-59 5.00E-02 2.l0E-07 4. l lE-04 Ni-63 5.00E-02 5.77£-07 l.54E-0l Nb-94 l.00E-02 7.14E-06 4.66E-05 Tc-99 8.00E-01 l.46E-06 2.02E-06 Total 1.36E+00 One particle was fou nd during the DRP survey. Thi s DRP (Sample IA81Al04P) was analyzed by gamma spectroscopy at GEL and had a Co-60 activ ity of 0. 167 µCi. The calculated dose from ingestion of this DRP is shown in the table below.
Table 16 - DRP IASIAJ 04P Ingestion Dose FGRll Ingestion Co-60 Ingestion Nuclide Dose Scaling Dose Factor, Factor (mrem) mrem/pCi H-3 6.40£-08 2.53£-03 2.70£-05 C-14 2.09£-06 3.59E-03 1.25£-03 Mn-54 2.77£-06 2.85£-04 l.32E-04 Fe-55 6.07E-07 7.14E-02 7.24E-03 Co-60 1.02E-05 l .00E+00 l.70E+00 Ni-59 2.l0E-07 l .66E-02 5.82E-04 Ni-63 5.77E-07 2.27E+00 2.19E-0l Nb-94 7.14E-06 5.53£-05 6.60E-05 Tc-99 1.46£ -06 l.17E-05 2.86E-06 Total 1.93E+00 Activated Concrete The activity in a piece of activated concrete at the 50th percentile of the Co-60 DRP scan MDA is shown below. The Co-60 scaling factors for Ba- 133, Eu-1 52, and Eu-154 were derived from the results of Sample S204EU. The remaining nuclides have been scaled to Co-60 using the Page 73 of96
ZionSolutions, LLC ZS-2022-010 Attachment activated metal scaling factors described above. The basis for using the activated metal scaling factors is the assumption that these nuclides are from the activation ofrebar in the concrete. We then scaled the Co-60 activities to the 50 th percentil e of the DRP scan MDA . The ingestion dose calculations for this particle as shown in the tables below. For this particle type, we have used the lowest_[! value and its corresponding dose conversion factor from FGRl 1.
Table 17 -Activated Concrete Particle Activity Particle Activity Activity Ratio to Nuclide Scaled to 50 th Co-60 Percentile MDA (pCi)
H-3 2.53E-03 3.04E+02 C-14 3.59E-03 4.31E+02 Mn-54 2.85E-04 3.42E+0l Fe-55 7.14E-02 8.57E+03 Co-60 l .00E+00 l.20E+05 Ni-59 1.66E-02 1.99£+03 Ni-63 2.27E+00 2.72£+05 Nb-94 5.53E-05 6.64E+00 Tc-99 1.17E-05 l.40E+00 Ba-133 5.07E-02 6.08E+03 Eu-152 1.1 SE+0l l.38E+06 Eu-154 5.40E-01 6.48E+04 Table 18 - Activated Concrete Particle Ingestion Dose Particle Ingestion Dose FGR 11 Ingestion Equivalent Scaled to Nuclide FGRll/1 Dose Factor Co-60 (mrem/pCi) 50 th Percentile MDA (mrem)
H-3 l.00E+00 6.40E-08 1.91E-05j C-14 l.00E+00 2.09E-06 8.84E-04 Mn-54 1.00E-01 2.77E-06 9.32E-05 Fe-55 1.00E-01 6.07E-07 5.1 JE-03 Co-60 5.00E-02 l .02E-05 l.20E+00 Ni-59 5.00E-02 2. 10E-07 4.llE-04 Ni-63 5.00E-02 5.77E-07 1.54E-01 Nb-94 l.00E-02 7.14E-06 4.66E-05 Tc-99 8.00E-01 l.46E-06 2.02E-06 Ba-133 1.00E-01 3.60E-05 2.03E-02 Eu-152 l .00E-03 6.48E-06 8.78E+00 Eu-154 l.00E-03 9.SSE-06 6.07E-0l Total 1.08E+0l Page 74 of 96
ZionSolutions, LLC ZS-2022-0 l 0 Attachment Irradiated Fuel Activity and Ingestion Dose For this particle type, we identified two sources of estimating absorption from the GI (i .e.,
alimentary) tract. The first is from ICRP-1 37 wh ich provides the following :
In Publi cation 30 (lCRP, 1979), an absorpti on va lue of 2XI 0-4 was recommended on the basis of the study of Maletskos et al. (1969). ln Publications 67 (lCRP, 1993) and 69 (ICRP, 1995a), because similar va lues have been obtained in more recent human studi es on the absorption of plutonium , americium , neptunium , and curium , a general absorption va lue of sx10- 4 was adopted for dietary intake by adults for all actinides other than uranium. In Publication 68 (1994b ), a value of 2X 1o- 4 was applied to ox ides and hydroxides, w ith 5X10-4 app lied fo r all other chemical forms. An fAvalue of 5X l 0- 4 is adopted here for all chemical forms.
However, this section oflCRP-137 does not provide direct gu idance for ingestion exposure to irrad iated fuel particles for the actinides. ICRP-13 7 does provide an in-depth di scussion on Cs-137 in irradiated fu el particles. Table 6.2 shows that for ingestion of all forms of Cs, except irradiated fuel , the/a value (same asjj for ICRP-30) is 1.0, but for irradiated fuel , the value is 0.1 or a factor of 10 reduction . Since the di scuss ion on the actinides value offa in ICRP-137 does not include irradiated fuel particles, but is included for Cs- 13 7, a very soluble element, using thi s factor of 10 reduction is app licable to the / a va lue of 5X10-4 for a final va lu e of 5X1 o-5 .
This value is consistent with the work reported in Environment Health Perspectives 29 with a value of 3X 10-5 for the fractional absorption by ingestion of radionuclides within irradiated fu el fragments. Additionally, thi s reference states, in regard to ingestion absorption of elements within a fuel fragment: " ... fis sion products in the fused particulate form renders them virtually inert in metabolic terms and the radionuclides are not metabolized along biological pathways characteristic for the elementary form."
Therefore, in this internal dose analysis we used a value for jj of SX 10-5 for the actinides. We applied a reduction factor of 10 in the lowestjj values listed in FGRl 1 for the other radion uclides identified in this particle except for Sr-90 and Eu-1 55, for which the lowestjj value from FGRll is used. It is likely that thejj value of sx10- 5 applies to all radionuclides contained within the fuel DRP ; however, thi s approach introduces a conservative margin into the dose calcul ation resulting in a higher CEDE than wou ld otherwise be calculated. We consider thi s approach to be appropriate and conservative for the hypothetical doses shown below for thi s 29 Environmental Health Perspectives, Review, Volume 103, No . 10, October 1995 , p. 920 - 934: "Biokinetics of Nuclear Fuel Compounds and Biological Effects of onunifonn Radiation," Sakari Lang (Department of Environmental Sciences, University ofKuopio, Kuopio, Finland), Kristina Servomaa (Department of Research, Finnish Centre for Radiation and Nuclear Safety, Hels inki, Finland), Veli-Matte Kosma (Department of Pathology, University ofKuopio, Kuopio, Finland), and Tapio Rytomaa (Finnish Centre for Radiation and N uclear Safety).
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ZionSolutions, LLC ZS-2022-010 Attachment fu el particle since it appears that anfi value of zero may actually apply to such an expos ure, which would further lower the calcu lated CEDE.
The ingestion dose from this particle was calcu lated using IMBA for the fI values shown in the table below along with the source of the/I, the Cs-] 37 sca lin g factor, and the CEDE using the ICRP-26/30 ti ssue weighting factors for the 50 th percentile of the MDA d istribution for Cs-137 .
The ingestion dose of the recovered fue l DRP, which containted .098 µCi of Cs- 13 7, is 14 mrem as shown in the tab le below.
Table 19- Fuel Particle Ingestion Dose S0126
- -- Ingestion Nuclide pCi /1 Source Dose (mrem)
Eu-155 838 0.001 FGRll 9.40E-04 Am-24 1 79900 0.00005 ICRP 137 modifi ed l.24E+0 l Cm-244 14800 0.00005 l CRP 137 modified 2.63E-01 Cs-137 98900 0.1 ICRP 137 4.53E-01 Np-237 3.9 0.00005 ICRP 137 modifi ed 6.14E-05 Pu-238 26188 0.00005 ICRP 137 modified 4.41E-0l Pu-239 7540 0.00005 ICRP 137 modifi ed l.19E-0l Sr-90 157043 0.01 FGRl 1 4.53E-0l Tota l 385212.9 1.42E+0l Tab le 20 - Irradiated Fuel Particle at Scan MDA Activities Particle Activity Activity Ratio Scaled to 50 th Radionuclide to Cs-137 Percentile MDA (pCi)
Eu-155 8.47E-03 3.47E+03 Am-241 8.08E-0l 3.31E+05 Cm-244 l .S0E-01 6.15E+04 Cs-137 l.00E+00 4.10E+05 Np-237 3.94E-05 l .62E+0l Pu-238 2.65E-01 l.09E+05 Pu-239 7.62E-02 3.12E+04 Sr-90 l .59E+00 6.52E+05 Page 76 of96
ZionSolutions, LLC ZS-2O22-O1O Attachment Table 21 - Irradiated Fuel Particle at Scan MDA Ingestion Dose Particle Ingestion CEDE Scaled to Radionuclide /1 Source of/,
50 th Percentile MDA(mrem)
Eu-1 55 1.00E-03 FGRII 3.91E-03 Am-241 5.00E-05 ICRP 137 modifi ed 5.l 8E+0I Cm-244 5.00E-05 JCRP 137 modified 1.l0E+00 Cs-137 l.00E-01 ICRP 137 l.89E+00 Np-237 5.00E-05 ICRP 137 modified 2.55E-04 Pu-238 5.00E-05 ICRP 137 modified l.83E+O0 Pu-239 5.00E-05 ICRP 137 modified 4.95E-01 Sr-90 1.00E-02 FGRll l.89E+00 Total 5.90E+0l Irradiated Fuel DRP Reduced Size over 1,000 years It is not possible to evaluate a rate at which particle sizes may change over the 1,OOO-year period because there is limited data on how stainless steel, concrete, and irradiated fuel particle sizes change with time. Size changes also depend on the natural processes such as weathering and corrosion, and site use such as grinding or pulverization from heavy equ ipment. The ICRP internal dose models are based on l µm AMAD.
ZionSolutions considered the potential for a particle that has been reduced in size over time and calculated the potential dose from the SO 126 fue l particle that had been size-reduced to a respirable size. To do so, we evaluated the dose impact from a fuel particle that was reduced in size to 1 µm AMAD over time. The spherical physical volume of the size-reduced particle is calculated to be 2.65E-1 4 cc, as compared to the 155 µm particle volume of2.O9E-O6 cc. The ratio of these volumes (l.35E-O8) would also represent the ratio of the activities for particle SO 126 to a hypothetical 1 µm dae particle, resulting in a Cs-1 3 7 activity of 1.33E-O3 pCi for the 1
µm particle. The scaled mix and estimated dose from inhalation of a 1 µm dae particle is 5.26E-O5 mrem as summarized in the fo llowing table.
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ZionSolutions, LLC ZS-2022-010 Attachment Table 22 - 1 µm AMAD S0J 26 Irradiated Fuel Particle Activities and Doses 1 µmA MAD Original Particle Inhalation Radionuclide Particle Activity Activity (p Ci) TEDE (mrem)
Ci)
Eu-1 55 8.3 8E+02 1.1 3E-05 l .25E-10 Am-241 7.99E+04 1.08 E-03 3.7 1£-05 Cm-244 1.48E+04 1.99E-04 4.68£-06 Cs- 137 9.89E+04 1.33 E-03 9.08£-08 Np-237 3.90E+00 5.26 E-08 9.66£-10 Pu-238 2.62E+04 3.53 E-04 8.0JE-06 Pu-239 7.54E+03 1.02E-04 2. l JE-06 Sr-90 l .5 7E+05 2.12E-03 5.90£-07 To ta t 5.26E-05 Doses from Complete Dissolution of Pa rticles Doses were also eva luated for complete di ssolution of particles over time into d istributed residual radioactivity in soi l over areas of 0.01 , 0.1, and 1 m 2 and at so il depths of 15 cm deep using Surface Area Factors and DCGLEMCS from the Zion LTP Chapter 6.11. Surface Area Factors for all the activated metal nuclides and the nuclide identified in DRP S204AEu and S0126 along with a so il density of 1.8 g/cc was used to ca lculate the di lution mass of the soil within these areas. The particle activities in pCi were divided by the masses associated with areas of 0.01 , 0.1 , and 1 m2 to calculate the distributed contamination soil concentration in pCi/g. The results are shown below. This analysis takes no credit for radioactive decay and is thus very conservative since complete dissolution wou ld li kely occur over many years, if at all.
Tab le 23 -Activated Metal DRP Dissolution Dose Activated Metal 50th Percentile Co-60MDA CEDE mrem) ---<---i 0.01 - - + -2.l0E-03
- 0. l - - + -2.1 0E-04
i 1 2. l0E - - '
Table 24 -A ctivated Concrete DRP Dissolution Dose Activated Concrete 50 th Area (m2) Percentile Co-60MDACEDE mrem 0.0 1 1.40£ -02 0.1 1.40£-03 1 l.40E-04 Page 78 of96
ZionSolutions, LLC ZS-2022-010 Attachment Table 25 - Fuel DRP Dissolution Dose Irradiated Fuel Area 50 th Percentile (m2) Cs-137 MDA CEDE (mrem) 0.01 3.41E-03
- 0. 1 2.06E-04 1 l.89E-05 DRP External Doses Varskin Version 6.2.1 was used to calculate ski n and deep dose (SDE and DDE). However, the 25 mremlyear dose criterion in 10 CFR 20 Subpart E app li es to TEOE, not skin dose, and therefore direct comparison of SDE and ODE to the 25 mremlyear criterion is not appropriate.
To allow comparison of SDE to the 25 mremlyear dose limit, the SDE was multiplied by a risk factor to calculate fata l cancer risk and compared to the risk corresponding to the 25 mremlyear TEDE criterion as provided in SECY-97-046A, whi ch is 4xI0* 4 ly. The fata l cancer risk factor applied to the SDE dose is from the 2002 Final Rule for Revision of the Skin Dose Limit30 . The risk factor from DRP SDE exposure is given as 6.6x10* 101rem. To compare the DDE skin dose to the 25 mremlyear criterion, the ODE could be multiplied by the skin tissue weighting factor of 0.01. However, this factor is not used in the DDE doses reported below. This is a highly conservative approach given that the exposure from DRPs are assumed to be limited to a 10 cm 2 area as opposed to the entire skin surface area.
Two types of DRPs were evaluated, activated metal and irradiated fuel , using the 50 th percentile of the Co-60 and Cs-137 scan MDA distributions, respectively. For each of the activities, the equivalent vo lume diameter, de, was calculated as described above. This diameter for a spherical particle was used in Varskin as the variable that accounts for the self-attenuation of beta particles within each DRP. Also, for the activated metal DRPs, on ly Co-60 was used since this nuclide clearly dominates the activity profile. The particle equivalent volume diameter is 124 µm with a density of 8 glee. For this particle, the associated Co-60 activity is 0.12 µCi and the SDE and DDE rates are 9.08 and 0.61 mrad per hour, respectively, corresponding to 24-hour doses of 218 and 14.6 mrad.
For the fuel DRP, the 50 th percentile particle diameter is 176 µm and the density is I 0.97 glee.
Only Sr-90 and Cs-137 are included in the ca lcul ations since the alpha emitters would make an insignificant contribution to SDE and DDE. Varskin includes the doses from progeny nuclides.
Therefore, the calcu lated dose includes the contri bution from Y-90. Lastly, the calcu lated dose rates are converted to a total dose for a 24-hour period as provided in the table below.
3
°Final Ru le, Revision of the Skin Dose Limit, 67 FR 16298, Apri l 5, 2002.
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ZionSolutions, LLC ZS-2022-010 Attachment Table 26 - Irradiated Fuel Particle External Doses SO'h Percentile SO'h SDE Rate soth DDE 24-hr SDE 24-hr DDE Nuclide Rate Activity (µCi) (mrad/hr) (mrad) (mrad)
(mrad/hr)
Sr-90 6.52E-01 5.44E+02 5.3 lE-02 1.31E+04 1.3 lE+00 Cs-I 37 4.1 0E-01 2.79E+02 6.3 lE-01 6.72E+03 4.32E+00 Total 1.06E+00 8.25E+02 6.84E-01 1.98E+04 5.62E+00 SOE Risk of Fatal Cancer/year l.l9E-08 As shown above, the risks of a fatal cancer at the calculated 24-hour SDEs are well below the 4.00E-04/year that is commensurate with the 25 mrem/year site release criteria.
To better evaluate the dose relative to the 25 mrem/year site release criteria, ZionSolutions used EPRI guidance for calculating a DRP Effective Dose Equivalent. 31 This approach, authorized by the NRC in RlS-2003-04,32 was used to calculate the worst-case effective dose equivalents for Co-60 and Cs-13 7 at the 50 th percentile MD As.
The NRC issued RIS-2003-04 to provide guidance regarding the use of EDE in place of DDE
" ... in showing compliance with regulatory requirements." The RIS goes on to state:
Licensees are encouraged to use the effective dose equivalent in place of the DDE in all situations that do not involve direct monitoring of external exposures using personnel dosimetry. Such situations include, but are not limited to : [ .. .] (2) calculating doses from contaminated soils and buildings; [ ... ] (5) making calcu lations in connection with license termination and release of sites; (6) assessing doses resulting from localized skin contaminations ...
The EPRI methodology is useful because it provides a more accurate method for calculating dose from DRP exposures. In particular, the EPRl data show that dose can vary dependent upon the location of the DRP on the body. For both Cs-137 and Co-60, the highest dose EDE conversion factors are for a particle located in the center chest area at 11.904 rem/hr per Ci for Cs-13 7 and 48.631 rem/hr per Ci for Co-60.
Using the Cs-137 and Co-60 EDE dose conversion factors, the EDE for particles at the 50 th percentile a posteriori MDAs are calculated and provided in the table below.
31 "Implementing the EPRI Effective Dose Equivalent (EDE) Methodology for Discrete Radioactive Particles on the Skin," Electric Power Research Institute, EPRI 1002823, October 2004.
32 "Use Of The Effective Dose Equivalent In Place Of The Deep Dose Equivalent In Dose Assessments," U.S.
uclear Regulatory Com mission , Regulatory Issue Summary (RIS) 2003-04, February 13 , 2003 .
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ZionSolutions, LLC ZS-2022-010 Attachment Table 27 - 50'h Percentile a posterio ri EDE a
a posteriori posteriori Max 50 th mrem/24 50 th rem/hr percentile hr percentile EDE MDA MDA(Ci)
(pCi) 50th % Co-60 Scan MDA 0.12 l.20E-07 5.74E-06 l.37E-0l 50th % Cs-1 37 Scan MDA 0.41 4. l0E-07 4.91E-06 l.18E-0l The effective dose equ ivalents from a particle on the skin are well below the license termination criteria.
Expectation Doses A risk-based approach was used to ca lcu late the potential dose from a DRP hypothetically remaining at the site. The approach fo llows that approved by the Commission for the termination ofthe She lwe ll license (SECY-98-117), in which thousands of residual DRPs were estimated to remain at license termination. The risk from particles in the soil was estimated by determining the annual expectation dose. The expectation dose is calcu lated by multiplying the probability of encountering, inhaling or ingesting a particle in a given year by the dose from the particle.
The probabi lities for particle ingestion, inhalation and skin adherence were calculated at the beginning of this response. Multiplying these probabilities by the doses for the various scenarios presented earl ier yield s the expectation doses shown in the following table.
The expectation dose for the doses calculated above are summarized below. The highest annual expectation dose for the 24-hr skin dose fuel particle SDE is 2.64E-03 mrem ; however, the corresponding ann ual EDE expectation dose is l .57E-08 mrem .
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ZionSolutions, LLC ZS-2022-010 Attachment Tab le 28 - Expectation Doses Annual Expectation Dose Calculation Case Dose (mrem)
Ingestion Activated Meta l at 50th percenti le 2. 18 E-08 Ingestion Activated Concrete at 50th l .72E-07 percenti le Ingesti on Fuel Particle at 50th percentil e 9.43E-07 Jngestion of 0. 167 µCi Co-60 Particle 3.09E-08 In gestion of SO 126 Fuel Particle 2.27E-07 Inhalation of 1µm Fuel Particle 9.12E- l 5 Fuel Particle 24-hour SDE 2.64E-03 Fuel Particle 24-hour DDE 7.49E-07 EDE Activated Metal at 50th percentile 1.83E-08 EDE Fuel at 50th percentil e 1.57E-08 NRC SPECIFIC CONSIDERATION 3c:
Consider updating the previous estimate of the number of discrete radioactive particles that may remain after the survey and collection activities are completed, which was based on the presence of one particle in every 50 centimeters (diameter) of the land surface (see the licensee ' s response to RAI-11 d in the letter dated February 10, 2021 (ADAMS Accession No. ML21067A225). The estimate of the number of particles should consider the potential for discrete radioactive particles remaining below the surface and should consider the likely location of the particles given their origin and transport mechanisms (see RAI-1 in the NRC letter dated August 19, 2021 (ADAMS Accession No. ML2 l 23 I A 187).
ZIONSOLUTIONS RESPONSE:
All of the DRPs identifi ed during the scan survey and vo lumetric sampling were remediated .
There w ill be no known DRP source term remaining. An estim ate of the number of DRPs that may remain is hypothetical. The most reasonable method for making an estimate of the number of DRPs that hypothetically may remain i to use the resu lts of the can surveys. The results of the vo lumetric sampling cou ld be used but the presence/absence test u ed in survey design provides only an upper-bounding estimate of DRPs that could remain, which is unrealistic.
The number of unidentified DRPs that could hypothetically remain wi ll be calculated by conservative ly assum ing that a ll of the DRPs identified during the scan survey were contained in a 1.0 cm layer of so il, regardless of the actual depth at w hich they were fou nd, and that the ran ge of DRP radionuclide activities and mixtures identified is representative of the DRPs that could hypotheticall y remai n. In addit ion, the hypothetical DRPs are assum ed to be lim ited to the first Page 82 of 96
ZionSolutions, LLC ZS-2022-0 l 0 Attachment 30.5 cm (1 foot) layer of so il. Given these assumpti ons, the estimate of the number of DRPs that cou ld hypothetica lly rema in was made by multiply ing the number of DRPs identified durin g the scan survey (i.e., one) by 30.5. Accordin gly, the hypothetica l number of particles projected to remain on the site is 31 (30.5 x 1).
The like ly locati ons of the particles, i.e., those locati on where DRP hypo th eti ca ll y remaining wou ld be most li ke ly to be found , were co nsidered in identifying areas that were included in the DRP Survey Plan . The methodo logy does not ascr ibe location within that area ; rather, it estimates the number that could remai n anywhere w ithin that area.
NRC SPECIFIC CONSIDERATION 4:
The revised survey plan, if developed, should consider the following information for addressing the survey area coverage during a future survey:
NRC SPECIFIC CONSIDERATION 4a:
A description of the areas surveyed and the rationale for not performing additional surveys of specific site areas . The rationale should consider information for any areas not surveyed previously, as well as relevant infom1ation from the licensee ' s RAI responses to the NRC letter dated August 19, 2021 (ADAMS Accession No. ML21231Al87).
ZIONSOLUTIONS RESPONSE :
Within the DRP Survey Plan, ZionSolutions targeted 36 survey un its that had the potential to contain DRPs. In determining what survey units to target, Z ionSolutions selected survey units:
- where clean concrete demo lition debri s (CCDD) was temporarily staged or transported through after completion of FSS
- where waste loadout areas resided
- with areas of elevated activ ity identified by ORISE during the April 2021 inspection survey
- that were adjacent to C lass 1 survey units (e.g., survey units 102 14, 102 13, 10212) where particles or elevated areas had been previously identified The rationa le for survey units not included in the DRP Survey Plan includes a combination of the following:
- Based on Z ionSolutions assessment of the so urce and transport of the DRPs that have been identified, th e survey unit was not expected to contain DRPs.
- The survey unit had no history of DRPs.
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ZionSolutions, LLC ZS-2022-010 Attachment
- ORJSE performed an FSS confirmatory survey or other independent verification survey in the survey unit w ith no identification of DRPs.
- Surveys performed during final si te grad ing did not identi fy DRPs.
NRC SPECIFIC CONSIDERATION 4b:
The scan coverage for each of the survey units and whether survey unit coverage will increase if a discrete radioactive particle is detected in a survey unit.
ZIONSOLUTJONS RESPONSE:
In the event that a DRP is detected, adj acent survey units wi ll be added to the survey plan unless already included or other considerations obv iate the need for expanding the survey area. In that event, the overriding considerations wi ll be documented. Scan coverage is addressed in the DRP Survey Plan.
NRC SPECIFIC CONSIDERATION 5:
The results of the survey and calculations should be submitted to the NRC. The licensee should provide a commitment to share the survey results with the NRC staff in the form of an FSS Record after the surveys and calculations have been completed. The result of the survey should include, as a minimum , the following information consistent with the considerations described in this RAI :
NRC SPECIFIC CONSIDERATION Sa:
The number of discrete radioactive particles detected during the licensee 's survey activities and their location .
ZIONSOLUTJONS RESPONSE:
One DRP contain ing 1.60 µCi of Co-60 was detected during the DRP Survey. The particle was located in SU 10221D.
The complete results of the survey and calculations will be submi tted to the NRC in a TSD upon completion of the work described in the DRP Survey Plan.
NRC SPECIFIC CONSIDERATION Sb:
The radionuclide composition and activity of the collected particles, along with a description of the laboratory analyses performed Particles collected during the survey should be analyzed by an offsite laboratory for their radionuclide composition. This information is necessary given the discovery of unexpected particles of initially undetermined origin and radiological composition during the April 2021 survey.
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ZionSolutions, LLC ZS-2022-0 10 Attachment ZIONSOLUTIONS RESPONSE:
No Cs-1 37 particles we re identified durin g th e survey. The DRP found durin g the survey was sent to GEL laboratori es fo r gamma spectroscopy analys is. The only gamma emitting nuclide detected was Co-60 . Jn additi on, dose ca lcul ati on fo r activated tee l ca led the HTD nu clide based on Co-60 acti vity using the most high ly acti va ted reactor intern als, th e baffl e plates.
NRC SPECIFIC CONSIDERATION Sc:
An estimate of the number of discrete radioactive particles that may remain at the Zion site after the survey is completed (i.e ., discrete radioactive particles either missed or below the MDA).
ZIONSOLUTIONS RESPONSE:
See the response to Spec ifi c Consideration 3c fo r the descripti on of the method to be used to estimate the number of DRPs that could hypothetically remain . The results w ill be provided to the NRC in the TSD th at docum ents th e survey res ults.
NRC SPECIFIC CONSIDERATION Sd:
An estimate of the radiation dose from the particles that may remain at the Zion site after the survey is completed . In developing its survey plan , the licensee should consider, as a minimum, the information provided in this RAJ , as it may apply to the Zion facility.
ZIONSOLUTIONS RESPONSE:
The DRP dose assessment method is described in the response to Specific Considerati on 3b. The results w ill be p rov ided to the NRC in the TSD that docum ents the survey results.
NRC RAI-lla:
~ustification that the licensee statement that the 2018 URS surveys confirmed that the concrete on the outside of containment meets the "free release" criteria given the reported remediation and detections of contamination recently provided to the NRC. This justification should address remediation that appears to have been performed on the containment building exterior concrete in 2018 and scan alarms and smear measurements that appear to be above the MDA in the 2018 URS survey results for the containment building exterior concrete. This justification should also include an evaluation of how the 2018 URS results compared to the 2016 URS results.
ZIONSOLUTIONS RESPONSE:
The statement that " .. .the concrete on the outs ide of containment meets the ' free release' criteri a ... " is in reference to its status after remedi ati on. The fact th at contaminati on was detected and remediated should not be interpreted to mean that the material did not meet the free release criteria before it was reused or di sposed off-site.
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ZionSolutions, LLC ZS-2022-010 Attachment The survey data from the 20 18 URS that was provided in the enc los ure to the February 10, 202 1, respo nses inc luded pre-remediation results that indicated that plant-derived radioactivity was detected as we ll as post-remediation data which showed no detectable radioactivity above background . For each instance in which a static a larm was recorded and/or where smear results were above Lo, the area wa rerned iated or removed and subseq uentl y re urveyed. In each occurrence, th e loose surface co ntaminati on was wiped clean, or the elevated material was removed in its entirety, and the area was resurveyed to veri fy th ere was no longer any p lant-derived radioactivity above background . These results are consistent w ith the text included in the February 10, 202 1, RAI response in which ZionSolutions states that this concrete meets the "free release" criteria.
The 2018 URS, in comparison with the 20 16 URS, found more elevated areas above background . This was expected, as more D&D wo rk was cond ucted adjacent to the Conta inment Buildings (insta ll ation of waste loadout tents, creation of access hatches in the Contai nments, significant dem olition of radioactive structures adjacent to the Containments). The le ve l of survey was significantl y increased for the 20 18 URS to acco unt for the changing conditions of the site.
NRC RAI-llb:
A description of the extent of contamination observed on the exterior containment building concrete after that area was put under isolation and control (i.e., 2016). This description should include:
- summary of the areas identified as potentially above background from scan alarms or smear sample measurements in the 2018 URS survey, including the measured activity and the approximate location (e.g. , elevation [less than 3 meters or above 3 meters], the proximity of the location to key features [such as equipment hatches, tent enclosures] , and whether the area was located on the Zion Unit l or Unit 2;
- summary of the area of the containment building exterior concrete remediated during or after the 2018 URS surveys;
- post-remediation data for the Zion containment building concrete that has not already been provided and/or a description of where the post-remediation data is located if it has been provided (e.g. , which pages of the "2018 Unit I and Unit 2 Containment Exterior URS" attachment contain the post-remediation data).
ZIONSOLUTIONS RESPONSE:
The exterior surfaces of the U nit 1 and Unit 2 Containment Buildings were put under isolation and co ntrol measures during the 20 16 URS. The isolation and control measures remained in place until January and February of 2017 when the tents were constructed . The isolation and Page 86 of 96
ZionSolutions , LLC ZS-2022-010 Attachment control measures remained in place for all other areas of the Containment Building exteriors outside of the tent enc losure. Becau se the isolation and contro l measures were no longer in place within the tents, the exterior surfaces of Containment w ithin the tents, as well as other areas outside of the tent, were subject to a more extensive URS in 2018 .
All areas identified as potentially above background were e ither rem ediated by wip ing clean or removed in its enti rety as shov.rn in Table 29 .
The fo ll owing table provides a summary of the static beta measurements that exceeded the alarm set-points durin g the 2018 URS for the exteriors of the Unit land Un it 2 Containment Bu ildin gs.
The table al so identifies whether the area was located on Zion Unit l or Unit 2, the elevation, and the proximity of the location to key features .
Table 29-2018 URS Elevated Beta Static Measurement Summary Scan Alarmed Alarm Scan Area Number Unit Area Readings Set-Point Remediation Location of Alarms ID (cpm) (cpm) decontamination by 1 1 3-9 m hei ght 1 1750 477 wiping 3-9 m height, near decontami nation by 1 3 conta inm ent access 2 32 15, 2494 787 wiping hatch 3-9 m height, near decontamination by 1 4 3 540,650, 750 477 tent opening wiping 3-9 m hei ght, near decontamination by 1 8 containment access 2 2703, 1150 787 wiping hatch 0-3 m height, near decontaminati on by 1 13 2 728, 777 507 tent opening wiping 3-9 m height, near decontam inati on by 1 15 1 1050 723 tent opening wiping 3-9 m height, near decontamination by 1 16 1 980 723 tent opening wiping 0-3 m height, near decontamination by 1 24 I 4616 763 tent opening wiping 0-3 m height, near complete removal 1 47 containment access 2 3400,2075 762 of scan area hatch Page 87 of96
ZionSolutions , LLC ZS-2022-010 Attachment Scan Alarmed Alarm Scan Area Number Unit Area Readings Set-Point Remediation Location of Alarms ID (cpm) (cpm) 0-3 m hei ght, near 1122, 2089, complete removal I 48 con tainment acces 3 762 1947 of scan area hatch decontamination by I 58 0-3 m height 2 648,939 494 wiping decontamination by 1 59 0-3 m height 1 810 543 wiping 564, 525 ,
3-9 m height, near decontamination by 2 1, 2 6 580, 409, 394 tent opening wiping 466, 975 0-3 m height, near decontamination by 2 13 2 486, 542 371 tent opening wiping 3-9 m height, near complete removal 2 15 1 1990 392 tent opening of scan area 0-3 m height, near decontamination by 2 18 2 798, 528 371 tent opening wiping 0-3 m height, near decontamination by 2 41 containment access 1 599 543 wipi ng hatch 0-3 m height, near decontamination by 2 42 containment access l 577 543 wiping hatch 0-3 m height, near decontamination by 2 43 containment access 1 566 543 wiping hatch 0-3 m height, near decontamination by 2 44 containment access 1 661 543 wiping hatch 0-3 m height, near decontamination by 2 45 containment access l 609 543 wiping hatch The following table provides a list of all the smears that were identified as above Lo.
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment Table 30- 2018 URS Elevated Smear Summary Unit Smear ID Count Number Beta Activity (dpm) Beta Lo (cpm) 1 1 1 35.99 9.08 1 1 2 6.74 9.08 I 57 I 9.66 9.08 1 57 2 0.89 9.08 I 8 1 9.66 9.08 1 8 2 3.81 9.08 1 13 1 9.66 9.08 1 13 2 12. 59 9.08 1 13 3 0.89 9.08 1 59A 1 21.36 9.08 1 59A 2 3.81 9.08 1 59 1 12.59 9.08 1 59 2 -4.96 9.08 1 52 1 9.65 8.9 1 52 2 3.97 8.9 1 23 1 12.48 8.9 1 23 2 29.51 8.9 1 23 3 -1.71 8.9 1 24A 1 9.65 8.9 1 24A 2 -4.54 8.9 1 25 1 15 .32 8.9 1 25 2 9.65 8.9 1 25 3 1.13 8.9 1 15 1 21 8.9 1 15 2 46.54 8.9 1 15 3 -4.54 8.9 1 ISA 1 18.16 8.9 1 15A 2 21 8.9 1 ISA 3 -4.54 8.9 1 1 1 21 8.9 1 1 2 3.97 8.9 Page 89 of96
ionSolutions, LLC S-2022-0 10 Attachment Unit Smear ID Count Number Beta Activity (dpm) Beta Lo (cpm) 1 52 1 9.65 8.9 1 52 2 3.97 8.9 1 3A 1 76.75 8.9 1 3A 2 77.25 8.9
] 3B 1 188.75 8.9 1 3B 2 184.58 8.9 1 8A 1 21 8.9 1 8A 2 21 8.9 1 8B 1 46.03 8.9 1 8B 2 37.52 8.9 1 1 1 8.33 7.65 1 I 2 8.33 7.65 1 1 3 3.81 9.08 1 13 1 40.96 7.65 1 13 2 30.48 7.65 1 13 3 44.76 9.08 1 13 4 35.99 9.08 1 4A 1 11. l 7.65 1 4A 2 19.4 7.65 1 4A 3 9.66 9.08 1 4A 4 27.21 9.08 1 4B 1 27.71 7.65 1 4B 2 19.4 7.65 l 4B 3 24.29 9.08
] 4B 4 15.51 9.08 1 4C 1 30.48 7.65 1 4C 2 40.96 7.65 1 4C 3 12.06 9.08 1 4C 4 12.59 9.08 1 4 1 27.71 7.65 1 4 2 19.4 7.65 Page 90 of96
ZionSolutions, LLC ZS-2022-010 Attachment Unit Smear ID Count Number Beta Activity (dpm) Beta Lo (cpm) 1 4 3 14.99 9.08 1 4 4 12.59 9.08 1 IA 1 44.3 2 7.65 1 lA 2 41.84 9.08 1 IA 3 74.01 9.08 2 34 1 9.65 8.9 2 34 2 9.65 8.9 2 34 3 6.81 8.9 2 35 1 9.65 8.9 2 35 2 -4.54 8.9 2 40 ] 12.48 8.9 2 40 2 12.49 8.9 2 41 1 35. 19 8.9 2 41 2 21.09 8.9 2 44 1 52.21 8.9 2 44 2 32.56 8.9 2 10 1 8.33 7.65 2 10 2 16.64 7.65 2 10 3 2.79 7.65 2 7 ] 519.8 1 8.99 2 7 2 559.93 8.99 2 7 3 15.36 8.99 2 2 1 17.71 8.99 2 2 2 9.63 8.99 2 15 ] 21 8.9 2 15 2 29.51 8.9 2 15 3 57.89 8.9 2 15 4 38.02 8.9 2 13 1 8.05 (alpha) 4.2 (alpha) 2 13 2 3.89 (alpha) 4.2 (alpha) 2 3 1 3.95 (alpha) 3.93 (alpha)
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ZionSolutions, LLC ZS-2022-0 l 0 Attachment Unit Smear ID Count Number Beta Activity (dpm) Beta Lo (cpm) 2 3 2 -0.18 (alpha) 3.93 (alpha) 2 4 1 7.74 7.65 2 4 2 3.81 7.65 2 1 (A3) ] 119.07 7.65 2 l (A3 ) 2 121.84 7.65 2 I (A3) 3 52.04 7.65 2 1 (A3) 4 72.01 7.65 2 I (A3) 5 96.92 7.65 2 1 (A3) 6 94.16 7.65 2 2 (A24) 1 13.28 7.65 2 2 (A24) 2 2.2 7.65 2 2 (A9) 1 18.82 7.65 2 2 (A9) 2 16.64 7.65 2 2 (A9) 3 30.48 7.65 2 2 (A9) 4 24 .94 7.65 2 2 (A9) 5 13.87 7.65 2 2 (A9) 6 32.66 7.65 2 1 (Al 7) I 4.97 7.65 2 1 (A17) 2 22.17 7.65 2 1 (Al 7) 3 5.56 7.65 2 1 (A 17) 4 13 .87 7.65 2 I (A l 7) 5 36. 02 7.65 2 1 (A l 7) 6 8.33 7.65 Post-remediation data for the survey performed on the Unit 1 exterior is included in the "2018 Unit 1 and Unit 2 Containment Exterior URS" report on pages 124-128. Post-remediation data for grids 1, 2, 13, and 18 in the Unit 2 survey is included in the report on page 202. Additional post-remediati on data for the U nit 2 survey was not included in the submitted report and was inadvertentl y not digitally arch ived before being sent to long-term records storage. As such, the data is not readily available. ZionSolutions is confident that rem ed iation and resurvey of th e remaining Unit 2 elevated scan areas was performed satisfactoril y based on the followi ng:
- Multiple stages of professional review and approval of the surveys are required and were executed prior to the structure bei ng deemed ready for open air demolition.
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ZionSolutions, LLC ZS-2022-01 0 Attachment
- The manager responsible for the work has confirmed that this process was fo llowed under his supervision.
- The same review and approval process was required for Unit 1, which is documented by the scan provided previously .
To the extent there is any question regarding the level of contamination of the CCDD, all of survey units in which the containment exterior CCDD was temporarily stored, transported through, or loaded into railcars are included within the scope of the DRP Survey Plan and were surveyed. The only exceptions to this are those survey units that went through FSS and ORISE confirmation followi ng the removal of the CCDD.
NRC RAI-llc:
Justification that the process for the URS surveys and the determination that material met the "free release criteria" is consistent with commitments in the LTP:
- a description of the process used to determine which areas to remediate and how large of an area to remediate (i.e. , once radioactivity was detected, how large of an area around the detection point was remediated and/or excluded from being part of the "free release" concrete material);
- an evaluation of whether the process for including or excluding concrete from being considered as "free release material" is consistent with the LTP conditions on URS.
ZIONSOLUTJONS RESPONSE:
Process Description . The process used to determine which areas to remed iate, that is, for the URS performed on the exteri or surfaces of the Unit 1 and Unit 2 Containment Buildings and the determination that the material met the free release criteria, is described in Section 5. 7.1.12 of the Zion LTP, wh ich states :
The decommissioning approach for ZSRP calls for the beneficial reuse of concrete from building demolition as clean fi ll. CCDD is defined as uncontaminated broken concrete witho ut protruding metal bars, bricks, rock, stone, reclaimed or other asphalt pavement or soi l generated from construction or demolition activities. On ly concrete debris that meets the definition of CCDD will be considered for use as clean hard fi ll and on ly when surveys have demonstrated that the concrete is free of detectable residual radioactivity.
If an elevated reading was observed, the area was bounded and marked with paint. The painted area was remediated, and all remediated material was controlled and disposed of as radioactive waste. The entire area that was remediated was rescanned to verify that it was suitable for free release. A ll areas with detectable radioactivity above background were remediated and Page 93 of96
ZionSolutions, LLC ZS-2022-01 0 Attachment res urveyed to verify suitability fo r free release and use as fill material (i .e., CCDD). A descripti on of the approximate area remedi ated for each elevated measurement was not always prov ided in th e fie ld logs; as such, exact sizes fo r remedi ation areas is unknown . Regardl ess of how large an area to remedi ate was, the entire area was resurveyed fo ll owing remedi ation.
There are no instances where CCDD th at was used as fi ll materi al or other concrete that was released fro m the site had detectable pl ant-related radi oactivity above backgro und . A li st of the areas that were remed iated is prov ided in Ta ble 29. A ll scan areas li sted in the tab le were either decontaminated by w iping or completely removed. A descr iption of the approx imate area remedi ated fo r each elevated measurement was not always prov ided in the fi eld logs; as such, exact sizes fo r remediation areas is unkn own .
Consistency with LTP . For CCDD remaining on-site as fi ll materi al, the process fo r survey ing and applyi ng dose is full y consistent with the L TP as ev idenced by the an swer to the prev ious question. This approach was approved by the NRC during the L TP submittal and rev iew process (see the response to RAT-4a and RA T-4d on Enclosure I to ZS-2017-0084 (ADAMS Access ion No. ML I 7215A095) dated Jul y 20, 2017).
NRC RAI-lld:
Justification that the URS surveys were performed adequately, including:
- a description of the process used to analyze the smear sample results, including: the method for determining if radioactivity above background was found in the sample (i.e., whether "Unc", the MDA, or some other criteria was used and a description of what " Unc" represents if " Unc" was used as the basis), a description of the process for determining whether smear samples were recounted, a description of which data was used in the evaluation of whether radioactivity above background was present when a sample was counted multiple times, and a justification for excluding data from the evaluation if any data was excluded .
- justification that concrete that had been located above 3 meters on the containment building exterior does not contain any residual contamination given the survey scan coverage of I 0%.
ZIONSOLUTIONS RESPONSE:
Process for analyzing smear sample results . The method for determining if radi oactivity above background was fo und in the sample was to determine if the acti vity exceeds Lo. "Unc" represents the uncertainty. The uncertainty was not used as a bas is fo r determining if activity was above background .
Process for determining whether smear samples were recounted and which data was used .
Smear samples were recounted if either the alpha or beta activity exceed ed Lo. Smear sampl es were recounted to verify if the activity remained the same or decreased. A decrease in acti vity over a short period of time indi cated the presence of radon or NORM. The last count of a smear Page 94 of 96
ZionSolutions , LLC ZS-2022-0 I 0 Attach ment sample, if it was counted multiple times, was used for evaluation. This aligns with standard industry practice when the presence of radon or NORM is a factor.
Justification for excluding data . The only data that were excluded from evaluatio n were those superseded by further co unts. Jn these cases, the hi gher activity of the origi nal smear was innuenced by the presence of rado n or NORM. lt is a standard industry practice to recount the smear after all owing time for decay and to discount the results of th e original ana lys is.
Justification for red uced survey scan coverage above 3 meters. The pathway for contam ination below 3 meters would be contact by personnel or equipment or by ai rborn e material within the tent enclosures. Because it is not normal for personnel or equipment to come into contact with bui lding surfaces above 3 meters, it was determined that there was a low potentia l for those surfaces to contain contami nati on above backgro und . Because there was a low probability of finding surface contamination above background, th e surfaces above 3 meters were designated as Class 2, and per procedure l 0% scan coverage was prescribed. In exception to this, the exterior surfaces above 3 meters w ithin th e waste tent were des ignated as Class 1 because of the greater potential for airborne contamination. As such, I 00% of the surfaces within the waste tent enclosure were surveyed.
NRC RAI-lle:
Evaluation of whether the containment building exterior concrete contamination (and/or the processes responsible for the contamination) could be a source of particles observed by the NRC, its contractor ORISE, and the licensee on the Zion site. This evaluation sho uld include:
- an evaluation of the root cause for radioactivity being detected in 2018 but not 2016 (i.e., was the initial survey inadequate, or was there a breakdown in isolation and control measures?) ;
- a description of the containment structure concrete, if any, from an area with detectable radioactivity above background that was included in the "free release material" (i.e., CCDD) that was disposed of on-site or that was moved through areas of the site post FSS;
- an evaluation of whether the factors that led to the detection of contamination on the Zion containment building concrete could have led to similar problems elsewhere on the site and, if so, a description of corrective actions that were taken or will be taken by the licensee to address the problem.
ZlONSOLUTIONS RESPONSE:
Root cause for time of detection. Z ionSolutions does not believe that the radioactivity being detected in 20 18 but not 20 16 is the result of inadequate initial surveys, a breakdown in isolation and control measures, or any other process fai lu re. Rather, Z ionSolutions believes it is a result of the seq uencing ofremediation. Several areas ofremediation in 2018 occurred near the Unit 1 and Unit 2 Containment Building equipment hatch openings which resided within the waste loadout Page 95 of96
ZionSolutions, LLC ZS-2022-0 10 Attachment tents, where airborne co ntami natio n was a common occurrence. The loadout tents were not present durin g the 20 16 URS. It is not unexpected that areas surveyed (co rrectly) as clean during the 2016 UR S might have been found to contain co ntamination in 2018. Rega rdl ess of the time at which activity was detected, the surfa ce was deco ntami nated if contamination was detected.
Description of concrete includ ed in CCDD. o portions of either containment structure with detectable act ivity were used as CCDD or released from the site without prior decontamination.
The contamination identified on the exterior of Unit l and Unit 2 containment in 2018 was low-level loose-surface contamination due to airborne radioactiv ity. All areas with detectab le radioactivity above background were remediated and resurveyed to verify suitabi li ty fo r free release and use as fill mate ri al (i.e., CCDD). There are no instances where CCDD that was used as fi ll material or other concrete that was re leased from the site had detectable plant-related radioactivity above background.
Evaluation of factors that led to contamination of concrete structures. Potential factors that led to the detection of contamination on the Unit 1 and Unit 2 Containment Building exteri ors were waste hand ling activities within the waste loadout enclos ure or cross-contamination from personnel or equipment. Waste loadout enclosures were not used or associated with other site buildings, and all other site buildings had been demolished prior to the demolition of the Unit 1 and Unit 2 Containment Buildings. As such, Z ionSo lutions does not believe that these factors could have led to similar problems elsewhere on the site. Thus, no corrective actions have been taken or planned.
ZionSolutions believes that the foregoing response also addresses the RC comment on p. 35 of the RAI letter, which states, "The measurement of radioactivity above background in the 2018 URS survey appears to be inconsistent with the text in in the February 202 1 RAI response (i.e. ,
that the 2018 survey confi rm ed previous measurements)."
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