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Integration of an advanced sealed-tube neutron generator into a mobile neutron radiology system and resulting performance
Nuclear Instruments and Methods in Physics Research B56/57
907
(1991) 907-910
North-Holland
Integration of an advanced sealed-tube neutron generator into a mobile neutron radiology system and resulting performance * William E. Dance LTV Missiles and Electronics Group, Missiles Division, Dallas, TX 7.52654003,
USA
Serge Cluzeau SODERN, 94451 Limeil Brevannes Cedex, France
Hans-Ulrich Mast ~nd~triean~agen_Betr~ebsgese~~scha~t mbH, W-8012 Ottobrunn, Germany
The first DIANE * neutron radiology system is being prepared for operation in the IABG laboratories in Ottobrunn (Germany). It utilizes a new D-T generator, designated GENIE 46, developed by SODERN (France) for this application. The generator is being integrated into an upgraded LTV-produced mobile neutron radiology system suitable for practical nonreactor inspection of components and structures. The maximum output of the present version of the GENIE 46 is 5 X 10” n s-l (14 MeV) with less than 10 mA ion beam current at 225 kV. Tube lifetime at maximum output is approximately 500 h, while at 10” n s-l the tube is designed for a lifetime of 1500 h. The geometry of the neutron tube, VHV connectors, ion source power supply, and cooling tubes
comprises a cannister designed to be compatible with the lo-in. diameter opening in the LTV moderator/collimator assembly. 3-D Monte Carlo neutron/photon transport simulations of the new integrated radiology system operation have been performed by IABG. The calculations predict a thermal neutron flux at the collimator exit (L/D = 13) of cp&OI E,, 5 0.3 eV) =I.2 x 10’ n cm-* s-‘. Comparisons of this value and other Monte Carlo results with actual performance will be made in the near future with the accrual of operational data.
1. Int.roductfon
the new neutron by SODERN.
Considerable progress was made during the past decade in the development of advanced transportable, “on-off” neutron radiology systems [1,2]. Such systems, which are based on small charged-particle accelerators, offer an attractive alternative to the earlier approach of utilizing the radioisotope 252Cf as the source of neutrons. The initiation of a project to develop an advanced neutron radiology system known as DIANE has been reported 131, which will utilize a new high-flux sealed-tube neutron generator as a source. Development of DIANE is a joint undertaking by four companies: LTV (USA), SODERN (France), SENER (Spain), and IABG (Germany). It is the purpose of this paper to present the status of development of the first demonstration model for the DIANE neutron radiology system. This model is comprised of the basic radiology system, including electronic imaging, provided and installed by LTV in 1988 in the IABG laboratories, and * Project in the framework of the European EUREKA tiative. Else&r
!&ience Publishers B.V. (Nor~“Holl~d)
2. IABG radiology
generator,
the GENIE
46, developed
facility
The present IAGB neutron radiology system, described in detail in earlier publications [3-51, is based
IniFig. 1. IABG transportable neutron radiology system. XI. ACTIVATION
908
W.E. Dance et al. / Advanced sealed-tube neutron generator
Fig. 2. Overall view of the IABG neutron radiology facility.
Fig. 3. The SODERN TN 46 neutron generator tube.
on a D-T neutron generator (Kaman Model A-711) which has a fast neutron yield (14 MeV) normally in the range 7-10 X 10” n s-l. Radiologic imaging is accomplished using either radiography film or a radioscopy system, the LTV Model NRTV-2. The IABG facility, with remotely-controlled robotics, is shown in fig. 1. The photograph shows, from the right to the left, the Kaman A-711 neutron generator head (extreme right) as installed in the spherical moderator housing, the moderator/collimator assembly and support stand mounted on the robotic platform, the cooling unit (left background) for the neutron generator head (the high voltage power supply for the accelerator is positioned directly beneath the cooling unit and is hidden by the robotic platform), and the electronic imaging module at the extreme left. This facility is located below ground level in one of IABG’s structures test buildings, in an 8.0 m x 3.5 m X 3.5 m room shielded by 1.5 m of removable concrete overhead and 1.0 m of concrete on the entry side of the room. Fig. 2 is a view of the overall NR facility, with the removable concrete shielding shown at the left and the above-ground control room to the right. A perimeter fence can be seen which prohibits personnel access to the radiation area during system operation.
660 mm, and its weight is 18 kg. The tube is sheathed in a cylindrical metal housing which, with certain additional components, constitutes the neutron emission module, the MEN 46. A more detailed description of the tube, its design, and operation has been published earlier [3,6,7]. Fast neutron (14 MeV) emission from the tube at a given accelerating voltage is directly related to the ion beam current to the tritium target. The ion beam current to the target is, in turn, governed by the gas pressure in the Penning ion source. Fig. 4 depicts the dependence of target current and neutron emission on the gas pressure at 225 kV maximum accelerating voltage. Also shown by the different curves is the effect of the ion source voltage parameter on the neutron emission. Neutron output of the TN 46 tube as a function of accelerating voltage is given in fig. 5. The GENIE 46 neutron generator is comprised of the components shown in fig. 6. From left to right in TN 46 NEUTRON TUBE
VHV = 225 kV
3. GENIE 46 neutron generator The advanced D-T neutron generator developed by SODERN, the GENIE 46, is designed for increased output as well as longer tube life over presently available systems. At a nominal output of 1O’l n s-* the neutron tube, TN 46, is designed for a minimum lifetime of 1000-1500 h; at the maximum output of 5 X 101’ 500 h. Fig. 3 is a n s-l its lifetime is approximately photograph of the TN 46 tube. The target end of the tube is near the left end; at the right end is an insulating component which mates with the high voltage connector to the tube. The tube diameter is 254 mm, its length is
/ unstable Range
Gas Pressura
k-
(tow)
-WI
Fig. 4. Dependence of TN 46 target current and neutron emission on tube gas pressure at 225 kV.
W.E. Dance et al. / Advanced sealed-tube neutron generator
TN46 PUNTNONTuBE m_
.._..
_...
909
Table 1 Neutron and photon levels predicted for the integrated GENIE 46 neutron radiography facility. Image plane at the collimator, L/D &,(O
50-
f&I
Ei, ‘kh 10,
20 -
Cd-ratio
= 12 (1.6+0.6)~10~ncm-~s-’
2100+80 mSv h-’ 56k4 mSv h-’ (0.13 kO.03) x lo6 n cm-’ 2.9 f 0.6
mR_’
Moderator surface
10-
2590fSOmSvh-’ 84+8 mSv h-’
5-
1
~~cratingvoltage 30
Ikv) /
lo2
Fig. 5. Neutron output of the SODERN GENIE 46 neutron generator as a function of acceleratingvoltage.
the photograph the following components are shown: system cooling units, low voltage power supply (LVPS), high voltage power supply (HVPS), electronics cabinet, and the neutron emission module (MEN 46) which contains the TN 46 tube previously shown in fig. 3. For the initial DIANE demonstration model the MEN 46 will be installed in the spherical moderator/collimator assembly replacing the Kaman accelerator which was seen at the right side of fig. 1.
4. System performance Performance of the GENIE 46 has been summarized in figs. 4 and 5 in terms of the emission of fast neutrons (14 MeV) from the D-T reaction. At the time of this
writing, installation of the GENIE 46 in the radiology system at IABG is awaiting completion of the export documents, which is imminent. However, the neutron radiological performance of the integrated system can be predicted based on the fast neutron emission of the GENIE 46 as recently measured by SODERN personnel, and Monte Carlo calculations performed and verified by experimental measurements on the present IABG NR system, as documented by IABG personnel [8]. Assuming a scale factor of 7 for the GENIE 46 over the Kaman A-711 generator and the results of the IABG measurements on the present system, the results for the integrated GENIE 46 NR system are predicted and tabulated in table 1. The thermal neutron beam at the imaging plane, as determined from the scaled measurements, is shown to be 1.6 X lo5 n cm-’ s-r. This compares with a value of 1.2 X lo5 n cm-* s-l predicted by the Monte Carlo calculations. A radiographic beam of this intensity is sufficient to yield quality electronic images in 3 min or less and film images in 15 min or less. In table 1, the higher neutron and gamma dose rates, G,, and a,, noted at the moderator surface as compared with those at the image plane are due to the closer proximity of the moderator surface to the moderator center.
5. Conclusions
Fig. 6. System components of the SODERN GENIE 46 neutron generator.
The increased performance of the integrated advanced neutron generator based NR system as summarized above will extend the present mobile “on-off’ neutron radiology capability to include production inspection applications. Inspection of turbine blades, pyrotechnic devices and aircraft structures, for example, now becomes economically feasible with the decreased exposure times and longer neutron tube lifetimes. It is anticipated further that, in the course of gaining operational experience with the new system, additional applications will emerge. XI. ACTIVATION
910
W. E. Dance et al. / Advanced sealed-tube neutron generator
References [l] W.E. Dance, SF. Carollo and H.M. Bumgardner, US Army Report AMMRC TR 84-39 (1984). [2] J.J. Antal, W.E. Dance, J.D. Moravec and S.F. Carollo, Neutron Radiography, Proe. 2nd World Conf., Paris, France, 1986 (Reidel, Holland, 1987) p. 407. [3] W.E. Dance, J.R. Huriet, S. Cluzeau, H.-U. Mast and F. Albisu, Nucl. Instr. and Meth. B40/41 (1989) 1316. [4] W.E. Dance and H.-U. Mast, Neutron Radiography (3) Proc. 3rd World Conf., Osaka, Japan, 1989 (Khrwer, Dordrecht/Boston/London, 1990) p. 195.
151W.E. Dance
and S.F. Carollo, Neutron Radiography Proc. 2nd World Conf., Paris, France, 1986 (Reidel, Holland, 1987) p. 415. 161 M. Dubochet, P. Bach and S. Cluzeau, ibid.. p. 175. Neutron Radiography (3) 171 S. Cluzeau and M. Dubouchet, Proc. 3rd World Conf., Osaka, Japan, 1989 (Khtwer, Dord~ht/Boston/~ndon, 1990) p. 205. @I R. Richter and H.-U. Mast, Proc. 1st Int. Topical Meeting on NR System Design and Characterization, Pembroke, Ontario, Canada, 1990, to be published.
907
(1991) 907-910
North-Holland
Integration of an advanced sealed-tube neutron generator into a mobile neutron radiology system and resulting performance * William E. Dance LTV Missiles and Electronics Group, Missiles Division, Dallas, TX 7.52654003,
USA
Serge Cluzeau SODERN, 94451 Limeil Brevannes Cedex, France
Hans-Ulrich Mast ~nd~triean~agen_Betr~ebsgese~~scha~t mbH, W-8012 Ottobrunn, Germany
The first DIANE * neutron radiology system is being prepared for operation in the IABG laboratories in Ottobrunn (Germany). It utilizes a new D-T generator, designated GENIE 46, developed by SODERN (France) for this application. The generator is being integrated into an upgraded LTV-produced mobile neutron radiology system suitable for practical nonreactor inspection of components and structures. The maximum output of the present version of the GENIE 46 is 5 X 10” n s-l (14 MeV) with less than 10 mA ion beam current at 225 kV. Tube lifetime at maximum output is approximately 500 h, while at 10” n s-l the tube is designed for a lifetime of 1500 h. The geometry of the neutron tube, VHV connectors, ion source power supply, and cooling tubes
comprises a cannister designed to be compatible with the lo-in. diameter opening in the LTV moderator/collimator assembly. 3-D Monte Carlo neutron/photon transport simulations of the new integrated radiology system operation have been performed by IABG. The calculations predict a thermal neutron flux at the collimator exit (L/D = 13) of cp&OI E,, 5 0.3 eV) =I.2 x 10’ n cm-* s-‘. Comparisons of this value and other Monte Carlo results with actual performance will be made in the near future with the accrual of operational data.
1. Int.roductfon
the new neutron by SODERN.
Considerable progress was made during the past decade in the development of advanced transportable, “on-off” neutron radiology systems [1,2]. Such systems, which are based on small charged-particle accelerators, offer an attractive alternative to the earlier approach of utilizing the radioisotope 252Cf as the source of neutrons. The initiation of a project to develop an advanced neutron radiology system known as DIANE has been reported 131, which will utilize a new high-flux sealed-tube neutron generator as a source. Development of DIANE is a joint undertaking by four companies: LTV (USA), SODERN (France), SENER (Spain), and IABG (Germany). It is the purpose of this paper to present the status of development of the first demonstration model for the DIANE neutron radiology system. This model is comprised of the basic radiology system, including electronic imaging, provided and installed by LTV in 1988 in the IABG laboratories, and * Project in the framework of the European EUREKA tiative. Else&r
!&ience Publishers B.V. (Nor~“Holl~d)
2. IABG radiology
generator,
the GENIE
46, developed
facility
The present IAGB neutron radiology system, described in detail in earlier publications [3-51, is based
IniFig. 1. IABG transportable neutron radiology system. XI. ACTIVATION
908
W.E. Dance et al. / Advanced sealed-tube neutron generator
Fig. 2. Overall view of the IABG neutron radiology facility.
Fig. 3. The SODERN TN 46 neutron generator tube.
on a D-T neutron generator (Kaman Model A-711) which has a fast neutron yield (14 MeV) normally in the range 7-10 X 10” n s-l. Radiologic imaging is accomplished using either radiography film or a radioscopy system, the LTV Model NRTV-2. The IABG facility, with remotely-controlled robotics, is shown in fig. 1. The photograph shows, from the right to the left, the Kaman A-711 neutron generator head (extreme right) as installed in the spherical moderator housing, the moderator/collimator assembly and support stand mounted on the robotic platform, the cooling unit (left background) for the neutron generator head (the high voltage power supply for the accelerator is positioned directly beneath the cooling unit and is hidden by the robotic platform), and the electronic imaging module at the extreme left. This facility is located below ground level in one of IABG’s structures test buildings, in an 8.0 m x 3.5 m X 3.5 m room shielded by 1.5 m of removable concrete overhead and 1.0 m of concrete on the entry side of the room. Fig. 2 is a view of the overall NR facility, with the removable concrete shielding shown at the left and the above-ground control room to the right. A perimeter fence can be seen which prohibits personnel access to the radiation area during system operation.
660 mm, and its weight is 18 kg. The tube is sheathed in a cylindrical metal housing which, with certain additional components, constitutes the neutron emission module, the MEN 46. A more detailed description of the tube, its design, and operation has been published earlier [3,6,7]. Fast neutron (14 MeV) emission from the tube at a given accelerating voltage is directly related to the ion beam current to the tritium target. The ion beam current to the target is, in turn, governed by the gas pressure in the Penning ion source. Fig. 4 depicts the dependence of target current and neutron emission on the gas pressure at 225 kV maximum accelerating voltage. Also shown by the different curves is the effect of the ion source voltage parameter on the neutron emission. Neutron output of the TN 46 tube as a function of accelerating voltage is given in fig. 5. The GENIE 46 neutron generator is comprised of the components shown in fig. 6. From left to right in TN 46 NEUTRON TUBE
VHV = 225 kV
3. GENIE 46 neutron generator The advanced D-T neutron generator developed by SODERN, the GENIE 46, is designed for increased output as well as longer tube life over presently available systems. At a nominal output of 1O’l n s-* the neutron tube, TN 46, is designed for a minimum lifetime of 1000-1500 h; at the maximum output of 5 X 101’ 500 h. Fig. 3 is a n s-l its lifetime is approximately photograph of the TN 46 tube. The target end of the tube is near the left end; at the right end is an insulating component which mates with the high voltage connector to the tube. The tube diameter is 254 mm, its length is
/ unstable Range
Gas Pressura
k-
(tow)
-WI
Fig. 4. Dependence of TN 46 target current and neutron emission on tube gas pressure at 225 kV.
W.E. Dance et al. / Advanced sealed-tube neutron generator
TN46 PUNTNONTuBE m_
.._..
_...
909
Table 1 Neutron and photon levels predicted for the integrated GENIE 46 neutron radiography facility. Image plane at the collimator, L/D &,(O
50-
f&I
Ei, ‘kh 10,
20 -
Cd-ratio
= 12 (1.6+0.6)~10~ncm-~s-’
2100+80 mSv h-’ 56k4 mSv h-’ (0.13 kO.03) x lo6 n cm-’ 2.9 f 0.6
mR_’
Moderator surface
10-
2590fSOmSvh-’ 84+8 mSv h-’
5-
1
~~cratingvoltage 30
Ikv) /
lo2
Fig. 5. Neutron output of the SODERN GENIE 46 neutron generator as a function of acceleratingvoltage.
the photograph the following components are shown: system cooling units, low voltage power supply (LVPS), high voltage power supply (HVPS), electronics cabinet, and the neutron emission module (MEN 46) which contains the TN 46 tube previously shown in fig. 3. For the initial DIANE demonstration model the MEN 46 will be installed in the spherical moderator/collimator assembly replacing the Kaman accelerator which was seen at the right side of fig. 1.
4. System performance Performance of the GENIE 46 has been summarized in figs. 4 and 5 in terms of the emission of fast neutrons (14 MeV) from the D-T reaction. At the time of this
writing, installation of the GENIE 46 in the radiology system at IABG is awaiting completion of the export documents, which is imminent. However, the neutron radiological performance of the integrated system can be predicted based on the fast neutron emission of the GENIE 46 as recently measured by SODERN personnel, and Monte Carlo calculations performed and verified by experimental measurements on the present IABG NR system, as documented by IABG personnel [8]. Assuming a scale factor of 7 for the GENIE 46 over the Kaman A-711 generator and the results of the IABG measurements on the present system, the results for the integrated GENIE 46 NR system are predicted and tabulated in table 1. The thermal neutron beam at the imaging plane, as determined from the scaled measurements, is shown to be 1.6 X lo5 n cm-’ s-r. This compares with a value of 1.2 X lo5 n cm-* s-l predicted by the Monte Carlo calculations. A radiographic beam of this intensity is sufficient to yield quality electronic images in 3 min or less and film images in 15 min or less. In table 1, the higher neutron and gamma dose rates, G,, and a,, noted at the moderator surface as compared with those at the image plane are due to the closer proximity of the moderator surface to the moderator center.
5. Conclusions
Fig. 6. System components of the SODERN GENIE 46 neutron generator.
The increased performance of the integrated advanced neutron generator based NR system as summarized above will extend the present mobile “on-off’ neutron radiology capability to include production inspection applications. Inspection of turbine blades, pyrotechnic devices and aircraft structures, for example, now becomes economically feasible with the decreased exposure times and longer neutron tube lifetimes. It is anticipated further that, in the course of gaining operational experience with the new system, additional applications will emerge. XI. ACTIVATION
910
W. E. Dance et al. / Advanced sealed-tube neutron generator
References [l] W.E. Dance, SF. Carollo and H.M. Bumgardner, US Army Report AMMRC TR 84-39 (1984). [2] J.J. Antal, W.E. Dance, J.D. Moravec and S.F. Carollo, Neutron Radiography, Proe. 2nd World Conf., Paris, France, 1986 (Reidel, Holland, 1987) p. 407. [3] W.E. Dance, J.R. Huriet, S. Cluzeau, H.-U. Mast and F. Albisu, Nucl. Instr. and Meth. B40/41 (1989) 1316. [4] W.E. Dance and H.-U. Mast, Neutron Radiography (3) Proc. 3rd World Conf., Osaka, Japan, 1989 (Khrwer, Dordrecht/Boston/London, 1990) p. 195.
151W.E. Dance
and S.F. Carollo, Neutron Radiography Proc. 2nd World Conf., Paris, France, 1986 (Reidel, Holland, 1987) p. 415. 161 M. Dubochet, P. Bach and S. Cluzeau, ibid.. p. 175. Neutron Radiography (3) 171 S. Cluzeau and M. Dubouchet, Proc. 3rd World Conf., Osaka, Japan, 1989 (Khtwer, Dord~ht/Boston/~ndon, 1990) p. 205. @I R. Richter and H.-U. Mast, Proc. 1st Int. Topical Meeting on NR System Design and Characterization, Pembroke, Ontario, Canada, 1990, to be published.