Outline

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

2. 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

3. 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

4. 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

5. 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%)

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

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

8. CERN LEP and Detectors

9. SLAC Site Impact

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

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

12. 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

13. 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

14. Critical and Proxy Radioisotopes 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

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

16. 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

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

18. Radioisotopes for Metals in BaBar Radioactivity in the BaBar IFR forward steel plug at three decay times (SA/SL) for 55Fe is much less than (SA/SL) for 60Co

19. 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

20. Recent Initiatives and Efforts

21. 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

22. 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

23. 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.

24. 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

25. 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

26. 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)

27. 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

28. 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

29. 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

30. 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

31. 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

32. 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

35. Thank you

37. 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

38. 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

39. 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.