Activation of Targets and Accelerator Components at PSI
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Transcript of Activation of Targets and Accelerator Components at PSI
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
Activation of Targets and Accelerator Components at PSI
- a Comparison of Simulation and Measurement
Daniela Kiselev, Sabine Teichmann, Michael Wohlmuther
Contents:• Overview of PSI• Nuclear reactions• Codes used at PSI to calculate nuclide inventories, dose rates• Applications: 1) Nuclide inventory in samples around SINQ target 3 2) Dose rates along SINQ target 4 3) Dose rates at the PIREX beam line 4) Nuclide inventory in samples from the E4 beam line• Comparison of the 2 calculational methods• Summary
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
Proton accelerator facilities + Experimental hall
Birds view of the Paul Scherrer Institut (PSI)
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
Injector 2Ring cyclotron590 MeV
Target M
Target E
SINQ
UCN Comet: 250 MeVGantry 1
Gantry 2Upgrade 2 mA to 3.0 mA in progress PROSCAN
OPTIS
OPTIS 2
Injector 1
PSI Proton Accelerator Facilities
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
All beam line components are surrounded by iron shielding.
Beam line from Target E to beam dump (side view)2.
5 m
Concrete shielding
Working platform
Target E Collimators Diagnostics
Beam dump
5 m
movable slitsinflatable seals
to SINQ
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
Components around beam line get activated... need to be removed eventually
• for replacement waste Nuclide inventory needed before disposal as required by swiss authorities
• for repair/dismantling planning of work procedures dose rate estimation needed
in addition:for future (planned) installations/facilities:• estimation of the amount of total waste after operation• dose rates needed for construction of shielding
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
excitationn
AA+1
1) Direct irradiation (590 MeV p): at loss points (target, collimators)
main process: spallation
2) Secondary particle fields:
after penetration of shielding: mainly neutrons,
thermalized in shielding material
equilibrated energy spectrum
important process: neutron capture at thermal energies,
e.g 59Co(n,)60Co, 107Ag(n,)108mAg
Activation due to
Evaporationof protons,neutrons,also2H, 3H .. 4He
pprimary particle
highly excited nucleus spallation
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
case 1: mainly due to primary irradiation
Monte Carlo particle transport program : n,p,d,3H....Input: dedicated geometry, material compositions, cross sections: for n<20MeV ENDF-B-VI.6, otherwise modelsOutput: n-fluxes (E<20 MeV), residual nuclei production rates
via Perl script
Cinder’90 Orihet3SP-Fispact or or
Input: irradiation and cooling history cross sections: Cinder library, EAF 2003 decay properties of isotopes Output: nuclide inventory, photon rate
MCNPX
used as source in MCNPX
via Perl script
dose rate
Calculation of the Activation
decaycodes:
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
- book-keeping prg. to calculate nuclide inventory- contains PSIMECX cross section library (developed at PSI)
nuclide inventory, scaled to measured dose rate.
Input:
choice of the representativen-flux spectrum
Production rates by folding with cross sections(PSIMECX)
choice of11 materialcompositions
Buildup/decay (Orihet)
case 2: mainly due to secondary particles PWWMBS
weightmaterial
surface dose +irradiation history
location (58 zones)
Output:
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
1. Activation in the close vicinity of the SINQ-Target 3
irradiation: 6.77 Ah for 2 years
p-beam
geom. model in MCNPX:3 samples:
Zrscrew
AlMg3hull
shielding316L
Zr tubes
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
1.0
4
1.0
0
0.3
0
1.2
6
0.9
5
8.0
7
1.2
9
1.0
0
0.9
9
0.3
0
1.2
6 1.5
4
7.7
2
1.2
9
0.6
4
0.6
0
0.6
4
0.5
9
0.1
1.0
10.0
Cl36 Mn53 Mn54 Fe55 Co57 Ni59 Co60 Fe60 Ni63
‘s in Ge-detector chemical + quantitative Analysis + measurement in Liquid Scintillator Accelerator mass spectrometry (AMS)
measurement done byradiochemist group at PSIin collaboration with AMS groupsin Zürich + Munich
Results for steel shielding: exp. / calc. activity
Nuclide inventory
2 different material compositions
simulation by MCNPX + Cinder‘90
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
0.69 0.
91
0.71
1.48
5.44
1.40
0.82
0.86
0.79
1.63
0.72
0.65
0.61
0.10
1.00
10.00
Na22 Cl36 Ti44 Mn54 Co57 Co60 Zn65 Ag108m
0.1
0.1
Results for safety hull: exp. / calc. activity
remarks:• overall good agreement with MCNPX+Cinder‘90• Na22: Data/SP-Fispact = 0.72• Fe60: deviation of factor 8 seen in many other samples• the right material composition (including impurities) is important!
2 different material compositions
not obtained in calculation
simulation by MCNPX + Cinder‘90
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
2. Planned: New Hot cell at PSI
What is the required wall thickness (shielding) ?
Most activated piece at PSI: SINQ target (Pb in Zr tubes) calculation of the nuclide inventory with MCNPX + Cinder’90 calculation of the thickness of the shielding with Microshield
How good are the predictions?5 SINQ targets were irradiated and dismantled
Compare calculated dose rates with measured data
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
0.1
1.0
10.0
M1 M2 M3 M4 M5 M6 M7 M8M1
M8
M7
M6
M5
M4M3M2
target:steel tubesfilled with Pb
stee
l shi
eldi
ng
Dose rates at SINQ Target 4
irradiation: 2 years with 10 Ah, cooling: 10 monthsdose rates obtained at 3cm, 30cm, 100cmdose rates calculated with MCNPX + Cinder‘90
Dose rates in Sv/h at 100 cm distance
calculation
data
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
0.1
1.0
10.0
100.0
1000.0
M1 M2 M3 M4 M5 M6 M7 M8
calculation
data
Dose rates in Sv/h at 3 cm distance
discrepancy: • factor 2 in the target region• factor 10 for small distance at the shielding reason: in calculation contribution also from target region Geiger Müller tube: smaller solid angle
measurement:
GeigerMüllertube
simulation:
x 10
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
purpose (1988 - 2004):material irradiation and degradation for Gantry 12006:dismantling of the beam line calculation of dose rates with MCNPX + comparison with measured doses
1 2 3
model in MCNPX of vacuum chamber
Beam current monitor
Degrader (Cu + C)
Beam Dump (Cu)
1
2
3
Assumption (made in simulation):
Degrader 2 and Beam dump 3are always in beam Irradiation history (simplified):16.6 y @ 8.3 μA 2.3 y cooling
3. Dose rates at the Pirex beam line at PSI
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
Comparison with data:
Overall agreement good
Average ratio 1.13
Two points with ratio > 2:
smaller dose as measured in
beam dump:
degrader was not always in
0.350(0.434)
0.020(0.057)
0.700(0.501)
0.660(0.315)
0.300(0.279)
0.380(0.295)
0.230(0.255)
0.115(0.181)
0.700(0.529)
Sv/h
Results of dose rate comparison:
calculated values by M. Wohlmutherin brackets
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
E4
Target E
ASK61
sample from beam tube
4. Activation of samples in the E4 beam line
Several samples were taken from• bending magnet ASK61• shutter behind ASK61• shielding around shutter
components are not directly irradiated calculation of the activity with PWWMBS use representative n-flux spectrum in vicinity of Target E
bending magnet ASK61(stainlesssteel) irradiated
for13 years
beam entry
2004:
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
1.4
3.6
1.4
3.5
1.6
3.1
1.4
1.2 1.4 1
.7
1.3
4.2
3.7 4
.9 6.2
0.2
8
0.0
16
0.6
25
0.01
0.1
1
10
Na2
2
Al2
6
Cl3
6
Sc4
6
V48
Cr5
1
Mn5
4
Fe5
9
Fe5
5
Co5
6
Co5
7
Co5
8
Co6
0
Ni6
3
Zr8
8
Y88
Nb9
5
Sb1
24
Results for beam entry at ASK61
Measured activities via• detection• Accelerator mass spectromety for Al26, Cl36, Ni59• Liquid Scintillation: Ni63
exp./calc. activity
calculationwithPWWMBS+ typicalstainless steelcomposition
calc. values from F. Atchison & M. Wohlmuther
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
• Electrical installations• Targets• Vacuum Chambers
• Collimators• Beam Diagnostic Monitors• Magnets• Shielding
Radioactive waste filled into Containers
Total activity per container: 1010 – 1012 Bq (4.5 t)
0.01 0.1 1 10 100
other metals
tungsten
PVC
insulation materials
lead
aluminum
copper
cast iron
concrete
stainless steel
normal steel
MA
TE
RIA
LS
CONTRIBUTION IN % OF TOTAL
Material compositon:
for most of thecomponents:nuclide inventoryobtained withPWWMBS
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
Comparison of the calculational methods
• PWWMBS: activation due to secondary particles main purpose: nuclide activity calculation of radioactive waste+ fast throughput, user friendly+ minimizing of personal dose (no detailed measurements or samples)- no predictions possible (dose rate needed)- accuracy: factor 10 due to simplified assumptions, sufficient for authorities
• MCNPX: activation due to primary irradiated fields main purpose: nuclide inventory calculation dose rate calculation energy deposit (input for ANSYS temperature distribution)+ predictions possible- elaborate geometry input- large cpu time (~1day on 256 - 512 nodes), statistical limitations+ accuracy: factor ~ 3 (except some outliers)
Comparison between simulation and measurement important
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
Summary:Predictions/calculations of the nuclide inventory and dose rates important for- disposal- personnel work at activated components
Solution at PSI:direct irradiation:MCNPX + Cinder’90 (or SP-Fispact, Orihet3)secondary particle fields:PWWMBS (nuclide inventory only)
Examples:1) Nuclide inventory of shielding + safety hull of SINQ target 3: good agreement2) Dose rates along the SINQ target 4 insertion: agreement within factor 23) Dose rates in vacuum chamber of PIREX: agreement within factor 24) Nuclide inventory of ASK61: exp/calc. < 10, except for Cl36
UC
N PIF
G
DirektSekundäres Strahlungsfeld72 MeV Neutronen (noch nicht spezifiziert)
1) direct irradiation2) secondary particles: n-flux spectra calculated for 72 and 590 MeV area, dependent on - shielding material - depth in shielding3) thermal neutrons
Division of the area in regions
Pirex (1988-2004)
SINQ
Gantry 1
Comet Optis 2
Gantry 2
Gantry 1
42nd ICFA, Advanced Beam DynamicsWorkshop on High-Intensity, High-Brightness Hadron Beams, Nashville, 25.8.-29.8.2008
Meson Production Area
Access to working platform after removing 3-4 m of concrete roof shielding
Use of remotely controlled shielded exchange flasks to remove defective components.
Repair work done in a hot cell.