Radioactive contamination transfer in Spiral II Simulation and experimental studies Manssour FADIL P. Dolegieviez, M. Ozille, V. Pismont, B. Rannou, Ph. Robillard
SAFERIB annuel meeting – EURISOL 27 – 28 October 2005 - Saclay
Summary 1
Objective of our works
1
MOVAK3D validation
1
Cryotraps dimensioning and conception
1
Contamination problem in vacuum system
1
Conclusion and Prospects
SPIRAL2 PROJECT OBJECTIVE Production of neutron-rich exotic nuclei A > 40 ; N
TOOL Nuclear fission
PROBLEM Very strong activity (5 1014 Bq) To have an idea : Target UCx (SPIRAL2) : 8,3 1013 Bq/kg PWR unloaded : 7,5 1013 Bq/kg
Problematic question : Very strong radioactivity ~ 5 1014 Bq Contamination transfer Simulation of nuclei migration
Vacuum systems dimensioning
MOVAK3D
Movak3D Code : description
1 Transmission probability 1 Molecular regime (very low pressure) 1 Any geometric shape 1 Monte Carlo Simulation
Movak3D Code : validation Comparative method
Theoretical formulas
Experimentation
Movak3D Code : theoretical validation L
Santler
Absorber
Source
D
3 L' Pr = 1 + 4 D
Diffuser
Pr
Santler, D.J., 1986, “New concepts in molecular gas flow”. J. Vac. Sci. & Technol. A −1
L’ = f(L/D)
0,2 0,16
MOVAK3D
0,12
Santler
0,08 0,04 0 0
10
20
30
40 L/D
MOVAK3D : Theoretical validation
De
Pr
D
Diaphragm Roth, A., 1990, “Vacuum technology”, Elsevier Science Publishers B.V., 3ed edition, Amsterdam.
1,E+00
MOVAK3D Roth
1,E-01
1,E-02
1,E-03 0
0,2
0,4
0,6
0,8
1 De/D
MOVAK3D : Experimental validation at 20 K Outgoing flux : Φe Transmission probability : Pr = Φe/Φi
Gaz flow at 20 K Flux entry : Φi
Measurement
MOVAK3D
N2
0.21 + 0.063
0.12 + 0.01
%
Ar
0,19 + 0.057
0.12 + 0.01
%
MOVAK3D : Experimental validation at 20 K
CRYOTRAPS OBJECTIVE
FUNCTION
Limitation of radioactive elements migration Radioactive gases trapping
TOOL
Cryogenic trapping system CRYOTRAPS
Radioactive gases in the target UCx after 90 days of irradiation
4,1 1014 Bq
Hypothesis : Tfusion < 2000 °C
80 K
→ element in the gaseous state
20 K
Te, Ba, Sr, Sb, In,…, H2O
N2, O2, CO2, CO, rare gases
GR1 : 3,5 1014 Bq
GR2 : 5,5 1013 Bq
20 K with an absorber solid
H2 ; H3 GR3 : 1,4 108 Bq
GR1 GR2
Total length : 100 cm
20 cm
GR3
80 K
20 K
20 K Ch. act
20 K
80 K
Transmission Efficiency (for s = 1) : (%) GR1
0,11
GR2
0,20
GR3
0,91
7 cm
CRYOTRAPS DESIGN
Contamination transfer from UCx target to the pumps Pumps related to the vacuum chamber
Probability transmission : 2.3 %
9,3 1012 Bq 4,1 1014 Bq
Contamination transfer from UCx target to the pumps Pumps related to the vacuum chamber Equivalent dose rate at 1 m (µSv.h-1)
1.1 106
0 hours
1.0 105
8 hours
5.0 103
3 months
3.9 102
1 year
and with radiobiological protection (20 cm of the lead) (µSv.h-1)
1.2
8 hours
Conclusion and prospects 1 1 1 1 1
Good agreement between Movak3D and measurements or theoretical formulas Cryotraps prototype under construction in GANIL Collaboration with Cryogenics team of IPN/Orsay to realize a cryogenic source Cryotraps prototype and cryogenic source tests at the beginning of 2006 Real contamination problem in vacuum systems
