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A Review of the Recent Studies A Review of the Recent Studies on the Dosimetric Issueson the Dosimetric Issues
A Review of the Recent Studies A Review of the Recent Studies on the Dosimetric Issueson the Dosimetric Issues
Tatsuhiko SatoJapan Atomic Energy Agency (JAEA), Japan
1SATIF10, June 2-4, 2010, CERN
Table of Contents1. Computational Dosimetry
2. Experimental Dosimetry
1.1 Calculation of Dose Conversion Coefficient (DCC)
1.2 Neutron Dose Estimation Using DCCs
1.3 Summary
2.1 Review of Current Status
2.2 Development of Dose Monitor DARWIN
2.3 Summary
2
BackgroundBackgroundBackgroundBackground
ICRP Publication 103
Definition of the effective dose (E) was revised Update of the radiation weighting factor wR
Update of the tissue weighting factor wT
Introduction of the ICRP/ICRU authorized voxel phantoms to represent reference male and female
Numerical values of E is subjected to be changed when ICPR103 is introduced in the radiation protection systemNumerical values of E is subjected to be changed when
ICPR103 is introduced in the radiation protection system
Evaluation of dose conversion coefficients (DCCs) based on ICRP103 is urgently requested
Evaluation of dose conversion coefficients (DCCs) based on ICRP103 is urgently requested
Task Group on Radiation Exposures of Astronauts in Space (TG67)
3
ICRP C2 Task GroupsICRP C2 Task GroupsICRP C2 Task GroupsICRP C2 Task Groups
Task Group on Dose Calculation (DOCAL)
W. Bolch (chair), V. Berkovskyy, L. Bertelli, K. Eckerman, A. Endo, T. Fell, N. Hertel, J. Hunt, N. Ishigure, D. Nosske, M. Pelliccioni, N. Petoussi-Henss, M. Zankl
Full Members
Nuclear decay data for dosimetric calculations (ICRP107) Reference voxel phantoms for adult male and female (ICRP110) DCCs for exposures to external radiation and intake of radionuclides
Publish the reference values of DCCs as the revision of ICRP74Publish the reference values of DCCs as the revision of ICRP74
G. Dietze (chair), D. Bartlett, F. Cucinotta, L. Junli,I. McAulay, M. Pelliccioni, V. Petrov, G. Reitz, T. Sato
Full Members
Guidance for assessment of radiation exposure of astronauts in space
Publish the reference values of DCCs for heavy ionsPublish the reference values of DCCs for heavy ions
4
Table of Contents
1. Computational Dosimetry
2. Experimental Dosimetry
1.1 Calculation of Dose Conversion Coefficient (DCC)
1.2 Neutron Dose Estimation Using DCCs
1.3 Summary
2.1 Review of Current Status
2.2 Development of Dose Monitor DARWIN
2.3 Summary
Calculation of DCCs by DOCALCalculation of DCCs by DOCALCalculation of DCCs by DOCALCalculation of DCCs by DOCAL
5
Particle Energy Geometry Simulation Code
Photon* 10keV-10GeV AP, PA, LLAT, RLAT, ISO, ROT
EGS, GEANT, MCNPX
Neutron* 1meV-10GeV AP, PA, LLAT, RLAT, ISO, ROT
FLUKA, GEANT, MCNPX, PHITS
Electron*/Positron
50keV-10GeV AP, PA, ISO EGS, GEANT, MCNPX
Proton 1MeV-10GeV AP, PA, LLAT, RLAT, ISO, ROT
FLUKA, GEANT, MCNPX, PHITS
Charged pion 1MeV-10GeV AP, PA, ISO FLUKA, GEANT, MCNPX, PHITS
Muon 1MeV-10GeV AP, PA, ISO FLUKA, GEANT
Calculation of DCCs under the framework of DOCAL
Cover almost all particles that should be considered in practical RPCover almost all particles that should be considered in practical RP
Reference values will be determined, simply taking the mean valuesReference values will be determined, simply taking the mean values
*included in ICRP74, but their energies are limited
Organ dose conversion coefficients for 30 organs or tissues, DT
Organ dose conversion coefficients for 30 organs or tissues, DT
Particle transport simulation inside phantoms using Monte Carlo codesParticle transport simulation inside phantoms using Monte Carlo codes
Calculation ProceduresCalculation ProceduresCalculation ProceduresCalculation Procedures
ICRP/ICRU adult reference computational
phantoms (ICRP110)
6
wR and wT defined in ICRP103
Effective dose conversion coefficientsbased on ICRP103, EICRP103
Effective dose conversion coefficientsbased on ICRP103, EICRP103
ICRP103 R T TT
E w w D
7
Comparison with Comparison with EEICRP60ICRP60 and and HH*(10) *(10) Comparison with Comparison with EEICRP60ICRP60 and and HH*(10) *(10)
EICRP60
EICRP103
>
wR for lower & higher energy neutrons were reduced in ICRP103 Numerical compatibility between wR and Q(L) relationship
wR for lower & higher energy neutrons were reduced in ICRP103 Numerical compatibility between wR and Q(L) relationship
High energy neutrons deposit more energy at deeper locations in ICRU sphere 10mm is too shallow to represent the dose in human bodyHigh energy neutrons deposit more energy at deeper locations in ICRU sphere 10mm is too shallow to represent the dose in human body
10−5 100 105
101
102
103
Neutron energy (MeV)
Dos
e pe
r un
it flu
ence
(pS
v.cm
2 )
H*(10)
EICRP60
EICRP103
10−5 100 105
101
102
103
Neutron energy (MeV)
Dos
e pe
r un
it flu
ence
(pS
v.cm
2 )
EICRP60
EICRP103
EICRP60
EICRP103
>
EICRP60
EICRP103
≈
H*(10)
>
0.2 50
H*(10)
≥
H*(10)
≥CCs for EICRP103 and EICRP60 for neutrons for AP geometry
(ICRP74 + PHITS)
(ICRP74 + PHITS)
(PHITS)
8
Table of Contents
1. Computational Dosimetry
2. Experimental Dosimetry
1.1 Calculation of Dose Conversion Coefficient (DCC)
1.2 Neutron Dose Estimation Using DCCs
1.3 Summary
2.1 Review of Current Status
2.2 Development of Dose Monitor DARWIN
2.3 Summary
Calculation ConditionsCalculation ConditionsCalculation ConditionsCalculation Conditions
9
Facility Location Spectrum data Dose type
CERN Concrete shield (top) IAEA 403 [1] H*(10) & EAP
CERN Iron shield (top) IAEA 403 [1] H*(10) & EAP
IHEP 70GeV sync. Filtered by concrete IAEA 403 [1] H*(10) & EAP
KEK 12GeV sync. Location 1 IAEA 403 [1] H*(10) & EAP
Tohoku 35MeV cyc. Underpass IAEA 403 [1] H*(10) & EAP
SSRL Linac Diagnostic room IAEA 403 [1] H*(10) & EAP
PWR in USA Containment IAEA 403 [1] H*(10) & EAP
AmBe source facility Glovebox IAEA 403 [1] H*(10) & EAP
Aircraft 12km @ polar region EXPACS 2.16 [2] H*(10) & EISO
[1] Compendium of neutron spectra and detector responses for radiation protection purposes, Technical report series 403, IAEA (2001)
[2] EXcel-based Program for calculating Atmospheric Cosmic-ray Spectrum, http://phits.jaea.go.jp/expacs/
10
Results of the dose estimationResults of the dose estimationResults of the dose estimationResults of the dose estimation
Ratios of effective doses to H*(10)
E / H*(10) > 1 for high-energy neutron fields Not so significant by considering the uncertainty in measurements
E / H*(10) > 1 for high-energy neutron fields Not so significant by considering the uncertainty in measurements
Introduction of ICRP103 results in the decrease of the effective dosesReduction of wR for lower and higher energy neutrons
Introduction of ICRP103 results in the decrease of the effective dosesReduction of wR for lower and higher energy neutrons
1.06
E / H*(10) < 1 for other neutron fields H*(10) can be adequately usedE / H*(10) < 1 for other neutron fields H*(10) can be adequately used
11
Table of Contents
1. Computational Dosimetry
2. Experimental Dosimetry
1.1 Calculation of Dose Conversion Coefficient (DCC)
1.2 Neutron Dose Estimation Using DCCs
1.3 Summary
2.1 Review of Current Status
2.2 Development of Dose Monitor DARWIN
2.3 Summary
Fluence-to-dose conversion coefficients for various particles were calculated by several codes, following the instruction given in ICRP103
Reference values of dose conversion coefficients will be published as the revision of ICRP74
Summary of Computational DosimetrySummary of Computational DosimetrySummary of Computational DosimetrySummary of Computational Dosimetry
12
We estimated neutron doses for various conditions …
We concluded …
Current radiological protection system can be maintained after the introduction of ICRP103, with respect to neutron dosimetryCurrent radiological protection system can be maintained after the introduction of ICRP103, with respect to neutron dosimetry
Introduction of ICRP103 results in the decrease of the effective dose EICRP103 / H*(10) ≤ 1.06 The use of H*(10) is fairly adequate even in high-energy accelerator facilities
DOCAL Activity
Personnel Work
13
Table of Contents
1. Computational Dosimetry
2. Experimental Dosimetry
1.1 Calculation of Dose Conversion Coefficient (DCC)
1.2 Neutron Dose Estimation Using DCCs
1.3 Summary
2.1 Review of Current Status
2.2 Development of Dose Monitor DARWIN
2.3 Summary
14
BackgroundBackgroundBackgroundBackground
Differences of radiation fields in high-energy accelerators in comparison to conventional nuclear
facilities Existence of high-energy neutron doses
Existence of pulsed time structure (pulsed beam accelerator)
Neutronbelow 20 MeV
Neutronabove 20 MeV
Photon
Muon
Dose, H*(10), contributions behind shield of accelerator
underestimated by conventional survey-meter
underestimated by conventional
moderator-based survey-meter (rem-counter)
Existence of muon doses
Improvement of active dosimeters is necessaryfor ensuring radiation safety in HE acceleratorsImprovement of active dosimeters is necessaryfor ensuring radiation safety in HE accelerators
High Energy Neutron DoseHigh Energy Neutron DoseHigh Energy Neutron DoseHigh Energy Neutron Dose
15
Tungstenpowder
3Hecounter
Polyethylenemoderator
Structure of WENDI-II
Applicable energy: ~ 5 GeV Weight: 14 kg
Olsher et al Health Phys. 79, 170 (2000)
Rem-counter implemented with heavy metal layerRem-counter implemented with heavy metal layer
Profile of WENDI-II
Re
spo
nse
/ H
*(1
0)
Conventional type
WENDI-II
Dose measured at CERF
Mayer et al RPD125, 289 (2007)
2 times
Neutron Energy (MeV)
Response of WENDI-II & conventional rem-counter normalized to H*(10) CCs
16
Muon DoseMuon DoseMuon DoseMuon Dose
Dose rates behind rock at FermilabCalculated dose ratio:: e : : n = 0.68 : 0.28 : 0.03 : 0.01 Muon has the dominant contribution Experiment ≈ Calculation
TotalMuon
e-
Neutron
Sanami et al, ISORD5 (2009)*calculations were done by MARS
Muon dose at a certain location
H*(10) or Effective dose
≠
CC for H*(10) & EICPR103 for - in comparison with stopping power
, e, doses must be distinguished
, e, doses must be distinguished
100 102 104100
102
104
Muon Energy (MeV)D
CC
(p
Sv.
cm2 )
or
EICRP103 /
dE
/dx
(Me
V/(
g/c
m2 ))
Stopping Power
H*(10) /
New device must be developedNew device must be developed
Pulsed-Time-Structure FieldPulsed-Time-Structure FieldPulsed-Time-Structure FieldPulsed-Time-Structure Field
17
Generated by pulsed beam with low frequency Dose rates at a certain moment >> Average dose rates Dead time of active dosimeters becomes significant
Profile of pulsed-time-structure field
Pulse counting
Current readout
Reference neutron dose rate (Sv/h)
Mea
sure
d do
se r
ate
(S
v/h)
Dose rates around KEK synchrotron measured by rem-counter (SARM)
Iijima et al 2009
Pulse counting mode
Current readout mode
contamination cannot be excluded
Saturation effect is occurred
Pulse interval = 2.2 secPulse interval = 2.2 sec
≠
Above 2 Sv/h
Data are rather scattered
Some improvements are still needed to measure neutron dose precisely at
pulsed-time-structure fields
Some improvements are still needed to measure neutron dose precisely at
pulsed-time-structure fields
18
Table of Contents
1. Computational Dosimetry
2. Experimental Dosimetry
1.1 Calculation of Dose Conversion Coefficient (DCC)
1.2 Neutron Dose Estimation Using DCCs
1.3 Summary
2.1 Review of Current Status
2.2 Development of Dose Monitor DARWIN
2.3 Summary
19
Whole System
System of DARWINSystem of DARWINSystem of DARWINSystem of DARWIN
Phoswitch-type Detector
BC501A 5×5φinch
PM
ZnS(Ag)+6Li
BC501A : fast neutron, photon & muon 6Li doped ZnS(Ag) sheet : thermal neutron
Digital Waveform Analyzer
6Li(n,α)3H
p
e-
Fast neutron
Thermal neutron
Photon
Dose monitoring system Applicable to various Radiations over WIde energy raNges
125 MHz 14bit ADC x 8 FPGA
Fast & slow components of light output
Maximum count rate: 100,000 cps !
Tablet PC Incident particle type: Pulse-shape-discrimination Corresponding dose: G-function method
Draw trend of dose rates in real time
DARWINDARWIN
20
Features of DARWINFeatures of DARWINFeatures of DARWINFeatures of DARWIN
1 . Capable of monitoring doses, H*(10), from•Neutron :•Photon:•Muon :
~ 1 GeV~ 100 MeV~ 100 GeV
all particles that should be practically considered in radiation protection in high energy accelerator facilities
2 . High sensitivity
5 . Applicable to pulsed-time-structure fields
•10 times higher sensitivity to neutron compared with conventional rem-counter
3 . Applicable to wide dose-rate range•Neutron : Background (10 nSv/h) ~ 10 mSv/h•Photon: Background (70 nSv/h) ~ 100 Sv/h
4 . Function to Determine energy spectrum• Unfolding technique based on the MAXED code* (UMG Package 3.2)
* Courtesy of Dr. Reginatto, PTB
• short dead time of the detector compared with gas counters
6 . Easy to use• LabVEIW-based graphical user interface• Relatively light weight (~7kg)
21
Table of Contents
1. Computational Dosimetry
2. Experimental Dosimetry
1.1 Calculation of Dose Conversion Coefficient (DCC)
1.2 Neutron Dose Estimation Using DCCs
1.3 Summary
2.1 Review of Current Status
2.2 Development of Dose Monitor DARWIN
2.3 Summary
Summary of Experimental DosimetrySummary of Experimental DosimetrySummary of Experimental DosimetrySummary of Experimental Dosimetry
22
Radiation fields are different from those in conventional nuclear facilities Radiation Protection in High-Energy Accelerator
Existence of high-energy neutron doses
Existence of pulsed time structure
Existence of muon doses
inserting heavy metal layer into their moderator: WENDI-II current-readout circuit was installed in their data analysis process
Conventional active dosimeters are not adequately used for ensuring the radiation safety
Conventional active dosimeters are not adequately used for ensuring the radiation safety
Several new devices have been inventedRem-counters have been improved …
As a different approach … Liquid-organic scintillator based dose monitor DARWIN was developed, using the latest digital pulse shape analysis techniques
DARWIN can improve the radiation safety in accelerator facilitiesDARWIN can improve the radiation safety in accelerator facilities
23
AcknowledgementAcknowledgementAcknowledgementAcknowledgement
DOCAL members for their discussion in calculating dose conversion coefficients
Dr. D. Satoh, Dr. A. Endo and Dr. N. Shigyofor their support in developing DARWIN
Dr. M. Hagiwara and Dr. H. Nakashimafor their support in performing J-PARC experiment
Dr. T. Sanami, Dr. M. Hagiwara, Dr. M. Harada and Dr. H. Nakashimafor their support in preparing this presentation material
I am thankful to
Thank you very much for your attention !Thank you very much for your attention !
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