Part E. Radiation monitors 1 / 29 Part E. Radiation monitors
dose rate ( Sv.h -1 ) ma 0 10 20 30 40 50 10.0 1.0 0.1 250 0 10 20 30 40 50 days since 18/01/02 200 150 100 50 0 Example: photon dose rate measurement around ESRF storage ring 2 / 29
Gas-filled detectors Geiger-Müller counter V E I proportional counter I N dd dt dd dt pairs E w gas e w V gas w V dn gas gas I dt pairs ionisation chamber w H 2 He O 2 Ar Air electrons 36.3 ev 41 ev 31 ev 26.4 ev 34 ev alphas 36.5 ev 44 ev 32.4 ev 26.4 ev 35.3 ev V 3 / 29
4 / 29 Ionization chambers
5 / 29 Proportional counter
6 / 29 Geiger - Müller counter
7 / 29 Neutron monitors Example: neutron spectrum around the 1.7 GeV BESSY storage ring (Courtesy of Klaus Ott)
cross section (barn) cross section (barn) Moderated neutron monitors 3 He-filled proportional counter: 1.E+06 1.E+05 1.E+04 1.E+03 1.E+02 3 He(n,p) 3 H n n 3 10 5 He p BF 3 counter: 3 H 765keV 7 3Li 2.310 MeV(94%) B 7 3Li 2.792 MeV(6%) 1.E+01 1.E+00 1.E-01 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 energy (ev) 1.E+04 1.E+03 1.E+02 10 B(n, ) 7 Li 1.E+01 1.E+00 1.E-01 Polyethylene moderator 1.E-02 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 energy (ev) 8 / 29
µs v. c m 2 (re la tiv e u n its ) 9 / 29 Moderated neutron monitors 1.2 1 IC R P C R A MA L -3 1 0.8 0.6 0.4 0.2 0 1.E -4 1.E -3 1.E -2 1.E -1 1.E + 0 1.E + 1 1.E + 2 e n e rg y (Me V )
10 / 29 Moderated neutron monitors Berthold LB-6411 Neutron response enhancement using lead-shell in moderator type counters
pressure Radiation monitors Superheated emulsions superheated drop (20 100 m) expanded bubble (~ 0.1 0.6 mm) 8 liquid neutron vapour embryo < 0.1 m charged particle solid superheating overexpansion vapour 0 0 3 temperature 11 / 29
12 / 29 Superheated emulsions Thermal neutrons: OK 0.1 10 MeV: OK Epithermal neutrons: not important Under-read > 10 MeV Energy response of SDD100 vials (dichlorodifluoromethane)
13 / 29 Superheated emulsions effect of lead moderator
14 / 29 Superheated emulsions Acoustic bubble counting Model ABC1260 Framework Scientific www.framesci.com
15 / 29 Gamma (X-ray) Gamma (X-ray) Gamma (X-ray) Spectrometer Neutrons
16 / 29 COMPANY MODEL ENERGY RANGE DETECTION RANGE THERMO SmartION Mini 2100S >10keV 0-500mSv/h FLUKE Victoreen 451P >25keV <50mSv/h THERMO FH40 G-L10 >30keV 10nSv/h - 100mSv/h THERMO FHZ 672 E-10: 48 kev - 4.4 MeV 1nSv/h - 100mSv/h THERMO RadEye PRD 30 kev 1.3 MeV 0.01 μsv/h 250 μsv/h THERMO FHT 752 SH 0.01-100,000 cps THERMO RadEye N >0.005 cps
17 / 29 Active radiation detectors: FHT192 FHT 762 Wendi-2 EPD 0 Manufacturer Thermo Electron GmbH Thermo Electron GmbH Thermo Electron GmbH 1 Particle Photons Neutrons Photons 2 Energy range 30 kev 7 MeV 25 mev 5 GeV 15 kev 10 MeV 3 Measuring range 100 nsv/h 1 Sv/h 1 nsv/h 100 msv/h Resol. 1 msv/h: <0.5 Sv/h 4 Sv/h Resol. 1 Sv/h: 4 50 Sv/h 4 Energy response Calibration factor resp. Cs-137: For low dose rate: 0.01-0.02 (μsv/h)/cps For high dose rate: 1.9-2.2 (μsv/h)/cps Calibration Factor: 1.14 (μsv/h)/cps 5 Quantity Hp(10) Hp(10) Hp(10) Ref. Cs-137 ±30% from 17keV to 6MeV ±50% from 6MeV to 15Mev 8 Type Active Ionization chamber Active Proportional counter Active semiconductor dosimeter 9 Sensitive material Inert gas (7 bar) He-3 (2 bar) + polyethylene moderator Silicon diode detectors 10 Dead Time Dead Time for high dose rate: 6- Dead Time: 1.8 μs -- 7 μs
18 / 29 TR01GN: Tunnel Detector Septum Magnet & Kickers
19 / 29 TR01GN: Tunnel Detector Septum Magnet & Kickers
1. Engineering solution 20 / 29 Radiation Monitors Network reinforced by movables monitors TR07N TR09N Experimental Hall TR07N TR06G EH33GN TR03GN
1. Engineering solution 21 / 29 September 16 th 09 1.4 1.2 D2 Gamma DR (usv/h) PSS trip due to dose rate alarm 1 0.8 0.6 Close a bit scraper Open scraper 0.4 0.2 From 2nC to 4nc Start bending magnet scan 0
1. Engineering solution 22 / 29 RMN: Cu SCRAPPER DATA Gamma dose rate due to the Cu scrapper scans 1.4 µsv/h 26-Sep-2008 SCRAPER SCANS Charge/pulse: 4nC/pulso Energy: 109MeV Frequency: 1Hz
1. Engineering solution 23 / 29 RMN: LOCAL SHIELDING EFFECT One klystron trip D2 D1 T1 Scraper scans
1. Engineering solution 24 / 29 Total accumulated dose (maximum values): Max. charge: 4nC/pulse Max. energy: 109MeV Frequency: 1Hz
1. Engineering solution 25 / 29 Integrated dose measured at the shield wall next to: BL16 & BL18 & BL20 Stored beam: 0.2 ma EH16G ZONA CONTROLADA 51.7 µsv RIESGO DE IRRADIACIÓN EXTERNA 26.5 µsv ZONA VIGILADA EH18G RIESGO DE IRRADIACIÓN EXTERNA 9.8 µsv Integrated over 4 hours period 12th March 11
1. Engineering solution 26 / 29 RADMON next to (integrated dose): BL16 & TR03 (next to BL16) & BL27 & TR01 (next to BL27) Stored beam: 100 ma 2.5 µsv EH33GN TR03GN EH27G EH16G 30 th : 50 ma 1 st : 100 ma
1. Engineering solution 27 / 29 RADMON next to (gamma dose rate): BL16 & TR03 (next to BL16) & BL27 TR01 (next to BL27) EH27G 50 µsv/h TR03GN EH16G 5 µsv/h 14:00 20:25 22:00
References 28 / 29 Radiation Safety JUAS 2007, P. Berkvens NCRP Report No 51: Radiation Protection Design Guidelines for 0.1-100 MeV Particle Accelerator Facilities. NCRP, 1979 - Although dated, still very useful. Scope limited to mostly radiation source terms and shielding. Concise, only technical information. NCRP Report No 144: Radiation Protection for Particle Accelerator Facilities. NCRP, 2003. It is a substantial revision and expansion of NCRP Report No. 51, the Report revises and expands on the earlier report and includes new information on source intensities, shielding, dosimetry, and the environmental aspects of particle accelerator operation. It is primarily concerned with radiological safety aspects that are special to the operation of particle accelerators having energies above about 5 MeV up to the highest energies available, while not neglecting low-energy neutron generators. IAEA Report No. 188: Radiological Safety Aspects of the Operation of Electron Accelerators, IAEA, Vienna,1979. - Scope limited to electron machines. Very detailed and comprehensive: all facets covered, except safety systems. Strongest points: source terms, shielding, yields (activation, ozone, noxious gases). Although dated, still a must for electron machines. IAEA Report No. 283: Radiological Safety Aspects of the Operation of Proton Accelerators, IAEA, Vienna,1988. - Equivalent to No. 188 for proton machines. More detailed, good reading on general issues, with some high-energy bias.
References 29 / 29 SLAC Report 327: Health Physics Manual of Good Practices for Accelerator Facilities. Stanford Linear Accelerator Center, - Written by a committee from DOE accelerator labs - bias towards large, high-energy facilities. Little technical detail, but strong on operational issues, including safety systems. Certain aspects not found elsewhere; useful general reading. Landolt-Borstein Compendium: Shielding Against High Energy Radiation, 1990, Springer- Verlag - Written by former members of the CERN Radiation Protection group (Fasso et al). Very expensive, availability limited. Encyclopedic approach - compilation of large amounts of available data. Not good for general reading and learning, but a valuable reference for specialists. A. H. Sullivan: A Guide to Radiation and Radioactivity Levels near High Energy Particle Accelerators, 1992, Nucl. Technology Publishing - Small cookbook with limited scope, but very practical. Essence distilled to rules-of-thumb and simple formulae. ICRP Publication No 60: 1990 Recommendations of the International Commission on Radiological Protection, Oxford, 1991, Pergamon Press Contains the latest recommendations on quantities and units for radiation protections, in particular the concepts of equivalent dose and effective dose. ICRP Publication No 103: 2007 The 2007 Recommendations of the International Commission on Radiological Protection It is an update of the No 60 and also include an approach for developing a framework to demonstrate radiological protection of the environment.
30 / 29 Many Thanks for your attention!