FLUKA for accelerator radiation protection –Indian perspective

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FLUKA for accelerator radiation protection
Indian perspective

• Sunil C
• Accelerator Radiation Safety Section
• Radiation Safety Systems Division,
• Bhabha Atomic Research Centre

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Accelerator Radiation Safety Section

• Operational radiation protection
• Associated RD
• Heavy Ion Accelerators (TIFR Bombay and VECC,
  Calcutta
• 5-7 MeV/amu Pelletron
• 10 MeV/amu with a superconducting linac booster
• 100 MeV/amu superconducting cyclotron
• Electron accelerators (RRCAT Indore)
• 20 MeV Microtron to 2.5 GeV electron synchrotron
• High current industrial accelerators

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Future plans

• ADSS
• Proton accelerators
• 20 MeV to 1 GeV
• Swimming poll critical reactor that can also be
  operated in sub critical mode with 600 MeV
  protons incident on LBE
• 14 MeV neutron generators
• Bare
• Injectors for sub critical assemblies

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Uses of FLUKA

• Routine accelerator radiation protection
• Source term calculations
• Shielding
• Induced activity
• Synchrotron hutch shielding
• Photoneutron estimation
• ADSS
• Proton accelerators
• Secondary particle dose from heavy Ion reactions
• Muon Transport and dose estimation
• Spallation yields comparison with JQMD

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Heavy Ion accelerators

• Neutron source term calculations
• EMPIRE, PACE (heavy ions) ALICE, PRECO (protons)
• Transport using the source.f
• BME!
• 10 MeV/amu to 100 MeV/amu
• Hauser-Feshbach for compound nucleus?
• Induced activity calculations
• Neutron spectrometry using passive techniques
• ECR ion sources
• Simulate electric fields?

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20 MeV proton on Be
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Electron Accelerators

• Photon (Bremsstrahlung) spectrometry
• High energy
• Detector response studies
• neutrons and photons
• Photoneutron spectrometry and dosimetry
• Synchrotron dosimetry
• Low energy (lt 10 keV)

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Photoneutrons

• Contribution to the exposure in electron
  accelerators
• A new technique to predict the neutron spectra
  using empirical relations
• Spectra from FLUKA fitted to a Maxwellian
• Temperature
• Yield
• Form a couple equation to predict the GDR part of
  the photoneutron spectrum

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Check
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The procedure
Sunil C, Sarkar P K, Empirical estimation of
photoneutron energy distribution in high energy
electron accelerators, Nuclear Instruments and
Methods A 581, (2007), 844-849.
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Independent FLUKA Calculation
Experiment
Our Calculation
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Neutrons gt 50 MeV

• Experimental verification using Bi fission foils,
  track etch membranes shows higher values when
  compared to FLUKA calculations.
• How much is photon induced fission?
• The cross section is 1 of neutron fission (?gt200
  MeV)
• But at the experimental area, the photon fluence
  is expected to be several times higher than
  neutrons!
• Calculate photon induced fission using FLUKA?

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Photon Transmission

• 30 cm diameter and 30 cm long cylindrical
  detector (approximating the upper trunk of a
  human body) is used to count the photons.
• USRTRACK estimator tallies the photon fluence.
• Deq99 (FLUSUW) subroutine used to fold the
  fluence with the dose conversion coefficients to
  obtain ambient dose equivalent

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Transmitted dose
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Unshielded Dose rate
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Variation with detector size
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Effect of detector size
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Variation with detector size
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Residual activity

• 2.5 GeV electron incident on 10 X0 -1Xm targets.
• DPMJET activated using PHYSICS
• LAM-BIAS at 100
• Photon transport cut off to 10 MeV

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Residual Activity (Bq/g)
SS
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2.5 GeV e-, 1mA, 24 hours
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Residual Nuclei

• In SS, 51Cr was reported by Fasso with a higher
  neutron cutoff energy.
• Swansons technique and present calculation agree
  within a factor of 2 for example 57Co in Ni
  target, 63, 65Cu from Cu target.
• 59Fe in SS (58Fe(n,?)) target in this calculation
  was found to be four orders less compared to that
  obtained by Sato and Fasso
• Most of the important nuclides formed are in the
  range of 200 -500 MBqW-1.

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Synchrotron Hutch Shielding

• Hutch design in INDUS (2.5 GeV, 1 mA)
• Bremsstrahlung mixed with SR
• Experiments claim existence of SR
• Transportation tough - low energy at the edge of
  FLUKA capabilities.
• Can it be simulated using FLUKA?

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Heavy Ion reactions

• Work done at PTB Germany
• 200 MeV 12C ions on water phantom
• Score neutron fluence and dose inside 5.7 cm
  spheres at different angles.
• Compare with measurements done at GSI
• Spectra from TOF (GSI measurements)
• Dose using a TEPC (PTB measurements)
• Dose using WENDI (GSI measurements)

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Neutron Spectra
200 MeV/amu 12C incident on 15 cm diameter
cylindrical water phantom
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Neutron and charged particles
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Charged particles
Apply coincidence measurements
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Response Matrices

• Neutron attenuation through a target of finite
  thickness.
• Response of Bonner sphere type passive
  techniques.
• Response of liquid scintillators
• Bismuth fission detectors
• Neutron induced fission
• Photon induced fission

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ADSS

• A sub critical assembly driven by 14 MeV neutrons
• 256 nat.U rods inside water column, beam tube at
  center.
• Analog mode
• 36 hours for 106 histories !
• And still large errors (10-30)

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Proton accelerators for ADSS

• Plans to couple a sub critical reactor to a
  proton accelerator
• Source term for lateral shielding of the
  accelerator tunnel, reactor pool top
• Residual activity in LBE loop
• Activation of magnets concrete wall
• LBE window rupture due to heat load

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ADSS problems

• High beam current 1-5 mA!
• Proton energies varying from 100 MeV to 1GeV
• Shielding calculations
• Reduce dose by 9 orders- 7 meters!
• Induced activity after several meters of water
• Explicit Transport !? Or calculate neutrons at
  intermediate thicknesses?
• Induced activity in magnets, concrete walls.
• Induced activity in LBE after several
  combinations of irradiations.

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Shielding

• Attenuation length from IAEA 283
• n/p ratio from FLUKA
• Multiply end result by the n/p ratio to get the
  transmitted dose after shield
• Biasing!

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Simplified view
concrete
7 m
water
Window
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Further work

• Establish attenuation curves for different shield
  configurations.
• Different types of concrete
• Transport neutrons through several meters of
  water and calculate induced activity.
• Irradiation profile, raddecay, dcytimes, usrbin

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Thank you