1. Technical aspects of release of metals from accelerators for recycling Sayed Rokni, Jim Allan, James Liu, Olga Ligeti, Alberto Fasso, Amanda Sabourov, Joachim Vollaire Radiation Protection Department SLAC National Accelerator Laboratory

2. 2 Outline Introduction B-Factory D&D at SLAC DOE Moratorium and Suspension Scrap metal management in accelerators Induced radioactivity at high-energy accelerators Technical basis for a path forward Conclusion

3. 3 Introduction Beam operation at high energy accelerators activates some of the beam line components (e.g. targets, dumps, septa) –Majority of materials in SLAC accelerators are free of added activation Currently, large amount of materials (metals) from Radiological Areas in accelerators are stored on-site in different facilities For beneficial reuse/recycling as well as alleviating storage needs and disposal costs, many accelerators needs to release these non-radioactive components containing metals for recycling

4. 4 PEP-II B Factory at SLAC *radioactive components (6%) *suspension material (~74%) 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)

5. 5 Magnets Vacuum chambers Lights Cable traysSprinkler pipes Fire sensors Utility pipes Supports PEP-II Tunnel Components

6. 6 Structures from BaBar Detector Magnet flux return (slabs of steel) and support girders

7. 7

8. 8 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

9. 9 DOE Property Release Limitation on Scrap Metal Secretarial Moratorium –Release of volumetrically contaminated metal (January 2000) –Prohibits release of metal with potential for volumetric residual activity into commerce for unrestricted use Secretarial Suspension –Release for recycling of scrap metals (July 2000, modified January 2001) –Suspends the unrestricted release for recycling of scrap metals from radiological area (per 10 CFR 835)

10. 10 DOE Standards for Radiation Protection of the Public and the Environment DOE Order 5400.5 –Primary radiation protection standard used to protect the public and the environment from undue risk of radiation associated with DOE operations –Establishes requirements and framework for the release of real property (lands and structures) and personal with small levels of residual radioactivity from DOE control DOE G 441.1-XX Provides guidance on derivation and use of DOE approved authorized limits for release of property

11. 11 Recent initiatives Revision of DOE Order 5400.5 Request for shielding blocks for Nevada Test Site Some facilities are working with their respective site offices to develop clearance processes Scrap metal management at Pantex

12. 12 Pantex revised radiation area posting procedures and retroactively deposted areas that were not subject to radiation fields or contamination –new posting procedures resulted in reclassification of the status of scrap metals already in storage Independent review conducted in September 2008 with participation of HSS and EM –Findings: Compliant with 5400.5, DOE Policy Scrap Metal Management at Pantex:

13. 13 Scrap Metal Management in Accelerators Pantex materials had mainly surface contamination Materials in high-energy accelerators are mainly volumetrically activated –Iron and steel plates, copper cables ….. –Isotopes in copper, plastic, lead and stainless steel: Co-60, Fe-55, Mn-54; Na-22, Si-32, H-3; Bi-207, Tl- 204, Hg-194, Pt-193, Ta-179; Co-60, Fe-55, Mn-54, Co-57, V-49, Ni-63, Nb-91, Ar-39, Ti-44;…

14. 14 Induced radioactivity at high-energy accelerators Production Depends on type and energy of accelerated particles, beam intensity (beam power) –Spallation, neutron capture, photonuclear reactions –Induced activity produced by high-energy proton accelerators is ~ 100 times than that produced by high-energy electron accelerators, for the same beam power Beam losses: Targets, dumps, collimators, collisions beam mis-steering, extraction Main characteristics Induced radioactivity Negligible contamination

15. 15 Technical basis for a path forward 1.Evaluation –Radioactive or not…. 2.Release Criteria –MDA, activity based, dose based… 3.Assurance that property meets requirements –Confirmatory measurements –Rigorous processes for documentation, records maintenance and reporting….

16. 16 1. Evaluation Use process knowledge: Identify components that can not be activated; exclusion of operations that can not result in induced radioactivity, (e.g. few hundred keV X-rays) Identify operations that can potentially activate materials; identify areas with/without activated components –measurements, calculation, evaluation Use simulations to identify components with induced activity above pres-set limit: –inventory of isotopes –determine MDA for key isotopes

17. 17 BaBar Detector Cerenkov Detector (DIRC) 144 quartz bars 11000 PMTs 1.5 T Solenoid Electromagnetic Calorimeter 6580 CsI(Tl) crystals Drift Chamber 40 stereo layers Instrumented Flux Return Iron & Brass/RPCs, LSTs (muon/neutral hadrons) Silicon Vertex Tracker 5 layers, double sided strips e + (3.1 GeV) e - (9 GeV) ‘

18. 18 Use of B 0 B 0 events as a test case All hadrons and gamma with sufficient energy to induce nuclear reactions need to be simulated – FLUKA MC code Transported e +, e -, kaons, pions, neutrons… No buildup of induced radioactivity in the materials All particle fluence

19. 19 Total Induced Activity (from B 0 B 0 events) Total induced activity after 10 years of irradiation and 1 year of cooling

20. 20 Total Induced Activity (from B 0 B 0 events) Total induced activity after 10 years of irradiation and 5 years of cooling

21. 21 2. Screening levels for clearance DOE primary standard for protection of the public is 100 mrem/year from all sources and pathways The dose constraint for any single source or pathway (which is applicable to property release) is 25 mrem/year In the development of authorized limits, the goal should be to maintain doses from a release to a few mrem/year or less ….for personal property, the goal should be to control doses to 1 mrem/year or less –( DOE/EH-0697-ES&H Bulletin 2006-05, Control and Release of Property ) ANSI N13.12-1999 Guidance for volumetrically activated materials (based on 1 mrem/yr) –30 pCi/g for most beta-gamma isotopes such as Co-60, Na-22

22. 22 CERN: LEP D&D The CERN accelerator facilities are on Swiss and French territory Switzerland –material coming from sccelerstor housing is considedred to be potentially radioactive –clearance levels are derived such that: Exposure by direct radiation (maximum dose of 1 mrem in a year). France –no clearance level –calculation based process are required CERN’s regulation must comply with the regulations of the two Host States

23. 23 CERN process for LEP and experiments D&D

24. 24 3. Assurance: Confirmatory measurements Measurement and survey protocols in support of the limits –Gross beta-gamma field surveys Surface contamination –Pantex used a Ludlum Model 12 with a GM frisker for surface contamination Material dose rate surveys –CERN used a NaI (1.3”x1.3”) – Gamma spectroscopy surveys on some of the items –Portal monitors to supplement the measurements

25. 25 Conclusion The necessary tools to measure and calculate induced radioactivity from accelerator beam operations are available –Inventory and concentration of induced radionuclides, resulting radiation levels of volumetrically activated components, locations of beam losses can be determined with a high level of confidence –Rigorous processes for documentation, records maintenance and reporting, QA are needed Clearance levels at MDA, or no rad added, or 1 to few mrem/year are conservative and reasonable basis for release of metals for recycling –The levels for release of volumetrically activated materials exists in consensus standards Technical aspects of issues related to the release of metals from accelerators for recycling is well understood

26. Thank You

27. 27 Field Surveys – Gross beta-gamma Surface contamination surveys performed using a GM pancake detector (Eberline HP360, Ludlum 44-9, TBM P15) Protocols per Procedure –All surfaces of every item surveyed –Swipes taken on Fe/steel for LSC measurement for Fe-55 Pantex used comparable detectors: Pantex used a Ludlum Model 12 with a GM frisker for surface contamination. Pantex estimated their MDAs for contamination to be about 8 dpm for alpha, 13 dpm for beta, and 60 dpm for tritium TBM P15 used at SLAC

28. 28 Field Surveys – Gross beta-gamma Ludlum Model 18 with 44-2 1”x1” NaI detector –Sensitive from <100 keV to several MeV Protocols per Procedure –All surfaces of every item surveyed CERN protocols are similar: –All surfaces of every item surveyed in low background area – slow scanning on contact CERN used comparable detector: CERN used a NaI (1.3”x1.3”) that could detect down to 3.5 µrem/hr Ludlum Model 18 with 44-2 NaI detector used at SLAC

29. 29 Field Surveys: Minimum Detectable Activity (MDA) MCNP then used to model volumetric activation Activation profile for BaBar/PEP components estimated by FLUKA Conversion factor used to determine MDA in field setting 2m  2cmt x 10 NaI detector (1” x 1”  ) with Pb wrap Fe MCNP geometry used for volumetric model Expected count rate per unit specific activity, cpm/(pCi/g) =0  2902 =0  =10 1177 =0  =20 433 uniform214  =∞ =0.1 277  =∞ =0.2 340  =∞ =0.7 556

30. 30 Example of FLUKA benchmark T489 experiment in ESA in 2007 (28.5 GeV e - beam) Copper target surrounded by materials typically found in accelerators structure (Al, Cu, SS, Ti …) Irradiation gamma spectrometry dose rate measurements, comparison with calculations

31. 31 Example of FLUKA benchmark Copper sample down beam of the target Comparison of the calculated and measured residual activity