Technical aspects of release of metals from accelerators for recycling

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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

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Outline

• Introduction
• B-Factory DD at SLAC
• DOE Moratorium and Suspension
• Scrap metal management in accelerators
• Induced radioactivity at high-energy accelerators
• Technical basis for a path forward
• Conclusion

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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

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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)
• suspension material (74)

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PEP-II Tunnel Components
Cable trays
Sprinkler pipes
Fire sensors
Lights
Utility pipes
Supports
Vacuum chambers
Magnets
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Structures from BaBar Detector
Magnet flux return (slabs of steel) and support
girders
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(No Transcript)
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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 1x1 NaI detector

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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)

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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

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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

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Scrap Metal Management at Pantex

• 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

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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

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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

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Technical basis for a path forward

• Evaluation
• Radioactive or not.
• Release Criteria
• MDA, activity based, dose based
• Assurance that property meets requirements
• Confirmatory measurements
• Rigorous processes for documentation, records
  maintenance and reporting.

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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

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BaBar Detector
Electromagnetic Calorimeter 6580 CsI(Tl) crystals
1.5 T Solenoid
e (3.1 GeV)
Cerenkov Detector (DIRC) 144 quartz bars 11000
PMTs
e- (9 GeV)
Drift Chamber 40 stereo layers

Silicon Vertex Tracker 5 layers, double sided
strips
Instrumented Flux Return Iron Brass/RPCs, LSTs
(muon/neutral hadrons)
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Use of B0B0 events as a test case
All particle fluence

• 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

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Total Induced Activity (from B0B0 events)

• Total induced activity after 10 years of
  irradiation and 1 year of cooling

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Total Induced Activity (from B0B0 events)

• Total induced activity after 10 years of
  irradiation and 5 years of cooling

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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-ESH 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

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CERN LEP DD

• 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
• CERNs regulation must comply with the
  regulations of the two Host States

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CERN process for LEP and experiments DD
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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 (1.3x1.3)
• Gamma spectroscopy surveys on some of the items
• Portal monitors to supplement the measurements

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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

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Thank You
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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

TBM P15 used at SLAC
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
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Field Surveys Gross beta-gamma

• Ludlum Model 18 with 44-2 1x1 NaI detector
• Sensitive from lt100 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

Ludlum Model 18 with 44-2 NaI detector used at
SLAC
CERN used comparable detector CERN used a NaI
(1.3x1.3) that could detect down to 3.5 µrem/hr
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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

NaI detector (1 x 1 f) with Pb wrap
Fe
2cmt x 10
2mf
MCNP geometry used for volumetric model
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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

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Example of FLUKA benchmark
Comparison of the calculated and measured
residual activity

• Copper sample down beam of the target