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 !