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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. Accelerator Radiation Safety Section. Operational radiation protection Associated R&D

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Fluka for accelerator radiation protection indian perspective l.jpg

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 R&D

  • 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 (< 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 > 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 (>200 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.

  • Swanson’s 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


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