Release of Material from Radiological Controls in Accelerators Sayed Rokni, Jim Allan, Alberto Fasso, James Liu, Amanda Sabourov, Joachim Vollaire, and Hirokuni Yamanishi Radiation Protection Department SLAC National Accelerator Laboratory, U.S.A. DOE Accelerator Safety Workshop, SLAC, August 17-19, 2010,

Outline Regulatory Background Secretarial Memoranda Site Impact PEP-II, BaBar Induced Radioactivity in Accelerators Activation characteristics Surface measurements Proxy radionuclides Radiological Clearance Workshop Volumetric release criteria Measurement protocols Expected Outcomes from the Workshop

Regulatory Background DOE Order 5400.5-1993 has provided requirements and guidelines for unrestricted release of property from radiological control Specific limits for surface contamination levels are prescribed in the Order No limits are given for release of material that has volumetric radioactivity. Such volumetrically contaminated materials may be released only on a case-by-case basis if criteria and survey techniques are approved by DOE For use with DOE Order 5400.5, DOE issued a draft Guide G 441.1-xx in 2002 for the implementation of the control and release of property that may contain residual radioactive material

Secretarial Memoranda Secretarial Moratorium (January 2000) Prohibits the release of volumetrically contaminated metals … into commerce Secretarial Suspension (July 2000, modified January 2001) Suspends the unrestricted release for recycling of scrap metals from radiation areas within DOE facilities Radioactive or not

PEP-II B Factory at SLAC HER = 2200 m, LER = 2200 m HER injection line = 2300 m, LER injection line = 2900 m Total length of beam line = 9600 m (6.0 miles) Radioactive components (< 6%)

Preliminary Field Surveys: PEP Activation Gross survey map Yellow shading represents some items in the area read above background used Ludlum Model-18 with 44-2 1”x1” NaI detector

Structures from BaBar Detector Magnet flux return (slabs of steel) and support girders

CERN LEP and Detectors

SLAC Site Impact Volume (ft3) Area (ft2) Landfill burial Shipping Cost   Volume (ft3) Area (ft2) Landfill burial Shipping Cost Labor Cost PEP-II 104106 33021 $1,041,058 $2,002,035 $1,500,000 BABAR 15625 5600 $289,250 $339,523 $500,000 Property Control (Hold) 104167 32541 $1,041,670 $2,713,269 $1,975,000 SUBTOTALS $2,371,978 $5,054,827 $3,975,000 TOTAL $11,401,805

Induced Radioactivity in Accelerators -Induced radioactivity is volumetric with maximum at a surface -Profile of radionuclides

Potential Activation in Electron Accelerators Tunnel 11 Potential Activation in Electron Accelerators Tunnel Bremsstrahlung Photons Electron Beam Loss Photonuclear Spallation Neutron Capture High-Energy and Low-Energy Neutrons

Beam Losses Beam losses, and consequent material activation, occur only on limited portions of an accelerator facility Some are produced on a small number of components designed to intercept the full beam power(targets, beam dumps) or a fraction of the beam (collimators) Other abnormal losses may occur at a few locations, due to mis-steering Most components (magnets, support structures, sections of vacuum chamber) do not become radioactive, especially at electron accelerators

Activation Characteristics No alpha emitters are produced No surface contamination in metals and other solid materials due to beam operations For material release purposes, in general, most abundant radioisotopes are those with a half-life of the order of the irradiation time (about 1 to 10 years) Induced activity in an object is volumetric and presents its maximum at the surface that faces beam loss points This supports surface measurements Radioisotopes that are difficult to detect are generally accompanied by “proxy” radioisotopes that can be clearly measured This supports measurements for proxy radioisotopes, instead of measurements for all potential radioisotopes that can be produced

Critical and Proxy Radioisotopes Material Radionuclide Half-life Carbon steel (Fe, C) and Cast iron (Fe, C, Si, Mn) 22Na (proxy) 2.6 y 54Mn (proxy) 312 d 55Fe (5.9 keV x-ray) 2.73 y 57Co 272 d Aluminum 22Na Copper 60Co (proxy) Concrete 3H (pure beta) 12.3 y 60Co 5.26 y 152Eu, 154Eu 13.5 y, 8.59 y Radioisotopes with long half-lives are of interest. Hard-to-measure radioisotopes (3H, 55Fe) emit only beta or low-energy X rays Proxy radioisotopes (22Na, 54Mn, 60Co) emit high-energy and high-intensity gamma rays 10 Sv/y  ANSI N13.12 Screening Level (SL): 22Na, 54Mn, 60Co: 30 pCi/g 55Fe, 3H: 3000 pCi/g Detection Limit requirement: ∑i (MDAi / SLi)  1

Example of FLUKA Induced Activity Calculations: BaBar Detector at SLAC 15 Example of FLUKA Induced Activity Calculations: BaBar Detector at SLAC Three Floors High, Thousands of Pieces

Volumetric Activation Profile in Metals The activity profile of each BaBar component has its maximum on the side that faces the source (e+ and e- collision point) SLAC Radiation Protection Dept. Note 09-04, 2009

Example of FLUKA benchmark – Exp T489 at SLAC Comparison of the calculated and measured residual activity Copper sample down beam of the target

Radioisotopes for Metals in BaBar Radioactivity in the BaBar IFR forward steel plug at three decay times Radioisotope Half-life FLUKA-Calculated Specific Activity in pCi/g (% of total) 1 year 2 years 5 years 60Co (proxy) 5.3 y 1.0×10-6 (22%) 8.9×10-7 (27%) 6.0×10-7 (38%) 57Co 272 d 9.4×10-8 (2%) 3.7×10-8 (1.1%) 2.3×10-9 (0.1%) 55Fe 2.7 y 2.4×10-6 (53%) 1.9×10-6 (57%) 8.8×10-7 (55%) 54Mn (proxy) 313 d 6.5×10-7 (14%) 2.9×10-7 (9%) 2.5×10-8 (1.6%) 49V 338 d 2.7×10-7 (6%) 1.3×10-7 (4%) 1.4×10-8 (0.9%) 3H 12.3 y 6.9×10-8 (1.5%) 6.5×10-8 (2%) 5.5×10-8 (3.4%) Remaining — 2.3×10-8 (0.5%) 1.0×10-8 (0.3%) 6.1×10-9 (0.4%) (SA/SL) for 55Fe is much less than (SA/SL) for 60Co

FLUKA-calculated Activity Profiles in Concrete Wall 55Fe / 22Na  10 Depth (cm) Depth (cm) Activity (Bq/g/W) 55Fe / 22Na  2 3H / 22Na  5 Depth (cm) Depth (cm) 10-year irradiation and 5-year decay

Recent Initiatives and Efforts

DOE Initiatives Revision of DOE Order 5400.5 (DOE O 458.1) Scrap metal management review of NNSA sites DOE review of SC accelerator labs: SLAC, TJLAB NNSA/SC Joint Working Group Radiological Clearance of Property Workshop, March 30- April 1, 2010, Las Vegas, Nevada

DOE technical assist visit of SLAC in December, 2009 Review of the property and material clearance processes Evaluate progress made to develop and implement enhancements to these processes DOE team reviewed SLAC radiological material clearance and occupational radiation safety programs and Identified five proficiencies with operations that demonstrates SLAC has continued to make improvements with their site processes and site procedures. Compliance with regulations and policies, technical basis, reduction of radiological areas, communication with public, proper survey technique Four observations were noted where additional improvements could be made to further enhance SLAC operations Property control, Independent verification, Survey instrumentation, Procedures

Disposition of SLAC Materials Two memos from DOE: April 13, 2010 on disposition of concrete shield blocks June 9, 2010 on disposition of BaBar detector and PEP-II material SLAC Site Office letter of July 1, 2010 Provides SLAC and SSO with a basis for developing and implementing a site strategy for disposition of CSB and scrap metal from BaBar and PEP-II projects, including the release of scrap metal for recycling The significance of the memoranda is that it now provides the SSO and SLAC with the authority to proceed with the disposition of certain materials in accordance with the requirements of DOE Order 5400.5 and SSO approval.

Joint Activation Working Group Co-Team Leads Scott Davis – SC-31.1 HQ Major David Pugh – NA-171.2 HQ SC Representatives Dennis Ryan BNL Sayed Rokni SLAC Don Gregory ORNL   NNSA Representatives Michael Duran LANL Todd Sundsmo LLNL Todd Culp SNL

NNSA/SC joint Working Group Develop… “Technical Position that will support the release of equipment and material from accelerator facilities and operations where there is potential for induced radioactivity or activated material” “This effort shall include all available facility, equipment, material, survey and detection information needed to derive criteria that can be used to determine the areas of and extent of activation.” “Criteria being developed should be reasonable and detection activities should be based on current techniques used within the Department and private industry.” Volumetric Activation

Regulations and Standards Clearance based on a dose criterion of 1 mrem/y has been recommended: IAEA Safety Series 89 (1988) EU Radiation Protection No. 89 (1998) ANSI N13.12 (1999) – “…Volume Radioactivity Standards for Clearance” NCRP-144 “Managing potentially radioactive scrap metal” (2002) DOE O 458.1 (Draft) Clearance levels (in specific activity) for radioisotopes are derived: IAEA-TECDOC-855 “Clearance levels for radionuclides in solid materials” (1996) EU Radiation Protection No. 122 (2000) ANSI N13.12 (1999)

Volumetric Release Criteria Indistinguishable from Background (IFB): the level below which materials are not subject to further regulatory control and can have unrestricted release > IFB and ≤ ANSI N13.12 (1999) Screening Levels (dose criterion of <1 mrem per year): as DOE pre-approved Authorized Limits for materials that may be volumetrically activated in accelerators Allows for consistent technical basis to document compliance with standards, directives, and Executive Orders > ANSI N13.12 (1999) Screening Levels: may be released through the DOE Order 5400.5 Derived Authorized Limit process

Process Knowledge Includes but not limited to: physics of induced radioactivity, facility operations, analytic or Monte Carlo calculations, and/or measurements to determine the types and the levels of induced radioisotopes in accelerators Process knowledge allows a graded approach such as the use of Areas of Interest (AOIs) concept AOIs are areas with potential for activation above background due to beam losses Materials in the AOIs are suspect activated Materials outside the AOIs are not activated (low energy and/or low intensity beam lines) Representative measurements to confirm predictions

Material Release Measurement Protocols demonstrate that induced activity in materials are either Indistinguishable from Background or meet ANSI Screening Levels Need Technical Basis to support measurement protocols Administrative controls need to be addressed for release above IFB – these can include recipient consent concepts, quality control and verification, and documentation on release processes

SLAC Measurement Protocols Measure surfaces of an item Measurements using commercially available field instruments and techniques with sufficient sensitivity (e.g., scanning with a 1”x1” scintillator detector) Instrument response is indistinguishable from natural background The Minimum Detection Activity (MDA) level of the measurements for the “proxy” radioisotopes of interest are no more than the corresponding ANSI Screening Levels (SL), i.e., ∑i (MDAi / SLi)  1 Laboratory analysis of representative samples as waranetd

ASW 2010 Workshop Expected Outcome Goal: Consistent measurement protocols to support for unrestricted release of concrete and metals Questionnaire on Measurement protocols Discussions of issues, show-stoppers and problems, and solutions that are expected or have occurred in the material release process of each lab Deliverable: Benchmark report

ASW 2010 Workshop –Questionnaire on Measurement protocols Release criteria Field instruments Methods (e.g. direct scan, discrete points) Graded measurement approach based on MARSSIM/MARSAME considerations Additional verification measurements (e.g. analytic sampling, portal gate monitors) Process knowledge Record management Reporting, public information Technical basis documents Impact to each site from metal moratorium

Release Criteria SLAC Only materials that have non-detectable radioactivity, i.e., indistinguishable from ambient measurement background, can have unrestricted release. Ludlum 1” NaI: net signal ≤ 2 of background signal of detectors; about 120 cpm in a background of 600 cpm. (detection limits = a few pCi/g for isotopes of interest). Fermilab See above. Both these threshold values have been determined to correspond to 95 % confidence levels for determining something to not be radioactive. Our limits represent specific activities of similar magnitude to SLAC’s. JLab Release allowed if no activity detected, and PK indicates little likelihood of hard to detect nuclides. Microrem: No detectable signal above ambient background – “detectable” defined to have upper bound of 5 µrem/h net. (sensitivity < 10 pCi/g for nuclides of interest in typical materials) Pancake GM: No detectable net signal (“detectable” defined to have upper bound of 100 cpm). Sensitivity assumed equivalent to DOE β-γ contamination limits. SNS NaI – Less than Lc in a background of less than 8000 cpm. Also need PK that material is uniform composition, no likely pure beta/alpha emitters, and most activated surface is accessible, OR activation calculation showing total activity less than 1000 dpm (powder), 5000 dpm (solid) or 10000 dpm (H-3). Pancake – less than 10CFR835 release limits for surface contamination LBNL For potentially activated materials, only materials that have non-detectable radioactivity, i.e., indistinguishable from ambient measurement background, can have unrestricted release (because they are non-radioactive material). Ludlum 1” NaI: net signal ≤ background signal Ludlum 2224 w/43-89: net signal ≤ surface activity in our release procedure, which references DOE O5400.5 Surface Contamination Limits (the same as Authorized Limits) BNL Only steel items with a thickness approx. < 2” or concrete thickness approx. < 4” indicating background only are candidates for unconditional release. Larger bulk items are considered volumetric release. Volumetric release requires direct scan along with analytical samples. Volumetric release is specifically authorized by and Radiological Control Division manager or as outlined in a Record of Decision. LANSCE Only materials with no detectable radioactivity shall be free released without any restrictions. Based on established LANL/LANSCE NDA release criteria (RP-1 TA-53 DP-312 procedure) Argonne Use “decision level” labeled on meter to decide if radioactivity is present. Typically 100 cpm above bkgd.

Analytic Sample Measurements Verification Measurements: Analytic Sample Measurements SLAC May include portable gamma spectrometry measurements in the field (detection limits around 1 pCi/g for isotopes of interest). May include core drill sample measurements with Laboratory gamma spectrometry system with environmental measurement protocol (detection limits around 0.1 pCi/g for isotopes of interest). Fermilab We have used these same verification techniques. We use field gamma spectroscopy, samples, etc. These are used when we have process knowledge reasons for believing that the activation is nonuniform, etc. Jlab Conducted for the following reasons: As part of technical basis study, If PK suggests potential for significant (> ANSI screening levels) activity that may not be detectable through standard survey, Release of liquids, finely divided solids, soil and soil analogues. Methods may include in-situ gamma spectroscopy, samples counted with lab gamma spec (including swipes, core drillings, liquids, etc.), and lab tritium analysis of swipes, liquids and leachates. Detection sensitivity defined in technical basis documents. SNS If any criteria not met, refer to Health Physicist for further evaluation, maybe including gamma spec LBNL Conducted as part of shield block release technical basis study. Conducted when warranted by process knowledge or for specific release and field applications. BNL Volumetric release would include direct survey and analytical samples. Brookhaven National Laboratory no longer has on site analytical measurement capability. Samples are sent off site for analysis (detection limits < 0.2 pCi/g for radionuclides of interest). LANSCE We primarily rely on process knowledge but have gamma spectroscopy capabilities if needed. Argonne same as SLAC not required, but may be done

Thank you

Field Instruments SLAC Volumetric radioactivity - Ludlum 2241 or 18 meter with 4402 detector (1” NaI) or equivalent Surface contamination - Ludlum 2241 with GM pancake or equivalent (e.g., TBM P15). Fermilab For volume activation, Bicron Analyst with 1.5” X 1.5” NaI probe or Eberline E140 or Ludlum 17704 Frisker Survey Instrument (Pancake GM tube) are used. The Bicron is preferred for detecting volume activation but magnetized materials and stray static magnetic fields from spectrometers, etc. preclude their use in some locations. Smear samples are also taken as indicated by other reasons. JLab Volumetric activity: Thermo (Bicron) Microrem with low energy option. Plastic (tissue equivalent) scintillator. Surface contamination: Pancake GM detector with any appropriate count rate meter. SNS Volumetric – 2x2 NaI probe with ASP-2e electronics. Surface Contamination – Pancake probe with Bicron Surveyor M LBNL Volumetric radioactivity: Ludlum 16 meter with 44-2 detector (1” NaI) or equivalent is required. Typically use Ludlum 2221 meter with 44-20 (3” NaI) detector. Surface contamination: Ludlum 2224 meter with 43-89 (alpha/beta phoswich) or equivalent. BNL Ludlum 19 micro-R with 1” NaI detector. LANSCE Eberline E600-SPA-3 (2X2” NaI) ESP-1-HP-260 (GM) Argonne Eberline ASP2e meter with PG2 2mm x 2 inch probe (mini-FIDLER)

SLAC Path forward for FY11 Complete SLAC release protocol consistent with guidance Program manual, technical basis document, operating procedures, document and record management Material management plan Identify components to be released Develop SSO/SLAC oversight and independent verification Develop stakeholder communication and reporting plan Release large shielding blocks, metals from PEP-II and BaBar

FLUKA-calculated Activity Profiles in Concrete Wall 38 FLUKA-calculated Activity Profiles in Concrete Wall Surface Maximum Photonuclear 55Fe / 22Na  10 Activity (Bq/g/W) Spallation 55Fe / 22Na  2 3H / 22Na  2 Depth (cm) 10-year irradiation and 1-year decay

Measured Activity Depth Profiles in Concrete 39 Measured Activity Depth Profiles in Concrete 220 MeV 45 MeV 1.3 GeV Measurements by Masumoto et al. of KEK at three electron accelerators “Evaluation of radioactivity induced in the accelerator building and its application to decontamination work,” Journal of Radio-analytical and Nuclear Chemistry, 255:3, 2003.