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DIANE neutron radiography device performance: comparison with reactor beam
Nuclear Instruments
and Methods in Physics Research B 99 (1995) 769-771
Beam Interactions with Materials 8 Atoms
ELSEVIER
DIANE neutron radiography device performance: comparison with reactor beam * S. Cluzeau a-* , P. Le Tourneur
‘, W.E. Dance b
’ SODERN? 20, aaenue Descartes, 94451 Limeil Brecannes C&den, France h Neutron Radiology. Dallas, TX 75229-2556, USA
Abstract Neutron radiography is an effective nondestructive inspection method; however its use has been equipment small enough for in-plant industrial applications in facilities with limited radioprotection. made with prototypes using accelerators, but these specific tools are not easily accepted by industrial or maneuverable equipment using recently available high-output long-lifetime neutron generators situation. This on-off equipment gives near-reactor image quality with simple and safe operating practically the same as are those currently used with industrial X-ray. The equipment is described, examples are given.
limited by the lack of Attempts have been users. New stationary basically changes this conditions which are and some application
1. Introduction
2. Small source NR system
Neutron radiography (NR) is a well known nondestructive testing method commonly applied to the inspection of nuclear fuel, materials with a high neutron capture cross section, pyrotechnic devices, and turbine blades [I]. In some cases NR is actually used to meet industrial needs, despite the time-consuming and costly necessity of transporting the test samples to a reactor facility. Without such a constraint, the application of NR could have spread to many other fields which are already well known, due to a substantial amount of research accomplished in many laboratories and institutes. Inspection of ceramics or composite materials and detection of aluminium alloy corrosion damage are examples of such very effective NR applications [l]. To remove the above-mentioned constraint, many attempts were made during the past ten years to design specific small-source NR systems suitable for in-plant use 121. Although some small systems using Van de Graaff accelerators. baby cyclotrons, californium sources, or sealed-tube neutron generators (STNG) are actually being used in laboratories, the people in charge of production nondestructive inspection have tended to “wait and see”.
The expectancy just mentioned may be attributed to two factors: the first is the need for manoeuverable equipment; the second is the need for image quality which is adequate for the tasks at hand. Recently it was proved that californium of STNG NR systems could be made to be maneuverable [I], but it is still generally expected that the image quality from these small systems may be less than needed, due to the low intensity of the neutron source. As explained in a former paper [3], this disadvantage of this low neutron emission can be offset by an optimization of the moderator, including reflector, appropriate moderator materials and good geometry. Some MCNP computations convinced the authors that a thermalization factor less than 500 cm’ can be obtained for 14 MeV neutrons, for instance, for the whole system including air gap and collimator inport. In this case, low neutron emission is rather an advantage for in-plant use. This paper is devoted to assessing the image quality supplied by such a small NR system.
3. Image quality of NR systems using STNG
. This work is partly supported by ANVAR and SERICS as part of the DIANE project in the framework of a EUREKA program. _ Corresponding author. Tel. +33 1 4.5 95 70 66. fax + 33 1 45 69 14 07. 0168-583X/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDI 0168-583X(94)00617-2
A stationary DIANE neutron radiography system was built at SODERN using a STNG as described in a previous paper [4], and the preliminary performance was reported in Ref. [S]. From this date, further new improvements were made in the equipment so as to reduce the gamma background, and the image quality now compares favorably
XVI. TOMOGRAPHY/RADIOGRAPHY
770
S. Cluzeau et al. /Nucl.
a
Instr. and Meth. in Phys. Rex B 99 (1995) 769-771
b
Fig. 1. Neutron radiographs of ASTM IQI. (a) BPI; (bl SI
with that obtained using a TRIGA nuclear reactor. Nevertheless, it must be pointed out that the thermalization factor of 625 cm* is not the best possible. The maximum thermal neutron fluence rate with the DIANE equipment is lo5 cm-’ s- ’ for an effective L/D ratio of 25. This parameter becomes 2.8 X 10’ cm-’ SK’ for an L/D of 60 accomplished by reducing the aperture diameter of the air-gap and of the collimator inport, which is appreciably more than the value 1.7 X 10” cm-z s-’ expected from the (D/L)* proportional law. This is due to a lower disturbance of the thermalizing volume of the moderator. We chose the lowest L/D ratio (approximately 2.51 for the images devoted to the image quality assessment so as to be in the worst conditions in comparison with the TRIGA NR system. The imaging system was a conventional TRIMAX 2 converter (Gd,OzS[Tb]) in conjunction with a 3M-FM film. The mean exposure time was approximately 15 min. The standard method for determining image quality was the ASTM E54.5. Judgment of the quality is based on evaluation of images obtained from two basic indicators: (1) the beam quality indicator (BP11 for quantitative determination of radiographic beam quality and (21 the sensitive indicator (SD for qualitative determination of the sensitivity of detail visible on the neutron radiograph. Fig. 1 gives the DIANE images of BP1 and SI, and Table 1 gives the result of applying the ASTM E545 standard to these images. Parameters values of the TRIGA NR system are from film supplied with the BP1 and SI certifications. As seen in Table 1, the image quality levels concerning thermal neutron content (NC), scattered neutron content (S), gamma content c-y) and pair production content (Pl, determined by densitometric analysis of the BP1 images, are in the same first category for the DIANE and TRIGA NR systems. As shown in Fig. 1, all of the SI gaps are Table 1 Image quality levels according
y
P
75% 0.7% 1% I
structure.
(a) NR; (b)
imaged, including the smallest (13 p,rn wide), giving the same IQ level of 7 for the G parameter and the first category for both systems. The only difference stays in the number of low-contrast holes (0.5 mm diameter) which can be detected: three for the DIANE and four for the TRIGA. Part of this difference can be explained by the low L/D value. Another way to assess the performance of the STNG system is simply visual observation of radiographic images obtained with various samples. Two examples are given in Figs. 2 and 3 for such an evaluation. The first one is a neutron radiograph of a honeycomb structure. The aluminium walls of the honeycomb are not at all imaged. and only the very thin hexagonal adhesive seals which hold the upper and lower skins are seen. Due to the view angle,
HG
DIANE IQ levels 70% 1.2% < 0.2% < 0.2% 3 quality category I I I I v quality category
of honeycomb
SI
NCS
TRIGA IQ levels
radiograph
to ASTM E 545 method
BP1
IQI item
Fig. 2. Neutron XR.
I
I
0.4% 1
7
I
4 7 IV I
Fig. 3. Silver brased seam of a copper pipe on a vacuum connec-
tor.
S. Cluzeuu et al. / Nucl. Instr. and Meth. in Phys. Res. B 99 C1995) 769-771
upper and lower hexagons are superimposed. It is nevertheless possible to detect a circular area with lack of adhesive over one of the two faces. The second figure shows a silver brazed seam of a copper pipe on a vacuum connector equipped with a rubber O-ring. The silver seal is imaged very well, and the O-ring is easy to inspect as well. An X-ray radiograph of the same sample is shown for comparison purposes. With this brief image assessment, it is important to remind that available image processing can also be used to analyze neutron radiographs, with a substantial improvement of the detail detection efficiency.
4. Conclusion These results, added to those already published [l,2], make it possible to consider neutron radiography as an
771
available and effective in-plant nondestructive testing method. Convenient equipment can be constructed using small accelerators or STNG, the later enabling one to design manoeuverable systems.
References [l] Proc. lst, 2nd. 3rd and 4th World Conf. on Neutron Radiography, held in San Diego (1983), Paris (1986). Osaka (1989) and San Francisco (1992), respectively. [2] J.P. Barton et al., Proc. 2nd WCNR. Part III (Reidel, Dordrecht, 1987) pp. 159-252. [3] S. Cluzeau, J. Huet and P. Le Tourneur. Nucl. Instr. and Meth.
B 79 (1993) 851. [4] S. Cluzeau and P. Le Tourneur, Nucl. Instr. and Meth. B 89 (1994) 428. [5] S. Cluzeau, J. Huct and P. Le Tourneur, Nucl. Instr. and Meth. B 89 (1994) 428.
XVI. TOMOGRAPHY/RADIOGRAPHY
and Methods in Physics Research B 99 (1995) 769-771
Beam Interactions with Materials 8 Atoms
ELSEVIER
DIANE neutron radiography device performance: comparison with reactor beam * S. Cluzeau a-* , P. Le Tourneur
‘, W.E. Dance b
’ SODERN? 20, aaenue Descartes, 94451 Limeil Brecannes C&den, France h Neutron Radiology. Dallas, TX 75229-2556, USA
Abstract Neutron radiography is an effective nondestructive inspection method; however its use has been equipment small enough for in-plant industrial applications in facilities with limited radioprotection. made with prototypes using accelerators, but these specific tools are not easily accepted by industrial or maneuverable equipment using recently available high-output long-lifetime neutron generators situation. This on-off equipment gives near-reactor image quality with simple and safe operating practically the same as are those currently used with industrial X-ray. The equipment is described, examples are given.
limited by the lack of Attempts have been users. New stationary basically changes this conditions which are and some application
1. Introduction
2. Small source NR system
Neutron radiography (NR) is a well known nondestructive testing method commonly applied to the inspection of nuclear fuel, materials with a high neutron capture cross section, pyrotechnic devices, and turbine blades [I]. In some cases NR is actually used to meet industrial needs, despite the time-consuming and costly necessity of transporting the test samples to a reactor facility. Without such a constraint, the application of NR could have spread to many other fields which are already well known, due to a substantial amount of research accomplished in many laboratories and institutes. Inspection of ceramics or composite materials and detection of aluminium alloy corrosion damage are examples of such very effective NR applications [l]. To remove the above-mentioned constraint, many attempts were made during the past ten years to design specific small-source NR systems suitable for in-plant use 121. Although some small systems using Van de Graaff accelerators. baby cyclotrons, californium sources, or sealed-tube neutron generators (STNG) are actually being used in laboratories, the people in charge of production nondestructive inspection have tended to “wait and see”.
The expectancy just mentioned may be attributed to two factors: the first is the need for manoeuverable equipment; the second is the need for image quality which is adequate for the tasks at hand. Recently it was proved that californium of STNG NR systems could be made to be maneuverable [I], but it is still generally expected that the image quality from these small systems may be less than needed, due to the low intensity of the neutron source. As explained in a former paper [3], this disadvantage of this low neutron emission can be offset by an optimization of the moderator, including reflector, appropriate moderator materials and good geometry. Some MCNP computations convinced the authors that a thermalization factor less than 500 cm’ can be obtained for 14 MeV neutrons, for instance, for the whole system including air gap and collimator inport. In this case, low neutron emission is rather an advantage for in-plant use. This paper is devoted to assessing the image quality supplied by such a small NR system.
3. Image quality of NR systems using STNG
. This work is partly supported by ANVAR and SERICS as part of the DIANE project in the framework of a EUREKA program. _ Corresponding author. Tel. +33 1 4.5 95 70 66. fax + 33 1 45 69 14 07. 0168-583X/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDI 0168-583X(94)00617-2
A stationary DIANE neutron radiography system was built at SODERN using a STNG as described in a previous paper [4], and the preliminary performance was reported in Ref. [S]. From this date, further new improvements were made in the equipment so as to reduce the gamma background, and the image quality now compares favorably
XVI. TOMOGRAPHY/RADIOGRAPHY
770
S. Cluzeau et al. /Nucl.
a
Instr. and Meth. in Phys. Rex B 99 (1995) 769-771
b
Fig. 1. Neutron radiographs of ASTM IQI. (a) BPI; (bl SI
with that obtained using a TRIGA nuclear reactor. Nevertheless, it must be pointed out that the thermalization factor of 625 cm* is not the best possible. The maximum thermal neutron fluence rate with the DIANE equipment is lo5 cm-’ s- ’ for an effective L/D ratio of 25. This parameter becomes 2.8 X 10’ cm-’ SK’ for an L/D of 60 accomplished by reducing the aperture diameter of the air-gap and of the collimator inport, which is appreciably more than the value 1.7 X 10” cm-z s-’ expected from the (D/L)* proportional law. This is due to a lower disturbance of the thermalizing volume of the moderator. We chose the lowest L/D ratio (approximately 2.51 for the images devoted to the image quality assessment so as to be in the worst conditions in comparison with the TRIGA NR system. The imaging system was a conventional TRIMAX 2 converter (Gd,OzS[Tb]) in conjunction with a 3M-FM film. The mean exposure time was approximately 15 min. The standard method for determining image quality was the ASTM E54.5. Judgment of the quality is based on evaluation of images obtained from two basic indicators: (1) the beam quality indicator (BP11 for quantitative determination of radiographic beam quality and (21 the sensitive indicator (SD for qualitative determination of the sensitivity of detail visible on the neutron radiograph. Fig. 1 gives the DIANE images of BP1 and SI, and Table 1 gives the result of applying the ASTM E545 standard to these images. Parameters values of the TRIGA NR system are from film supplied with the BP1 and SI certifications. As seen in Table 1, the image quality levels concerning thermal neutron content (NC), scattered neutron content (S), gamma content c-y) and pair production content (Pl, determined by densitometric analysis of the BP1 images, are in the same first category for the DIANE and TRIGA NR systems. As shown in Fig. 1, all of the SI gaps are Table 1 Image quality levels according
y
P
75% 0.7% 1% I
structure.
(a) NR; (b)
imaged, including the smallest (13 p,rn wide), giving the same IQ level of 7 for the G parameter and the first category for both systems. The only difference stays in the number of low-contrast holes (0.5 mm diameter) which can be detected: three for the DIANE and four for the TRIGA. Part of this difference can be explained by the low L/D value. Another way to assess the performance of the STNG system is simply visual observation of radiographic images obtained with various samples. Two examples are given in Figs. 2 and 3 for such an evaluation. The first one is a neutron radiograph of a honeycomb structure. The aluminium walls of the honeycomb are not at all imaged. and only the very thin hexagonal adhesive seals which hold the upper and lower skins are seen. Due to the view angle,
HG
DIANE IQ levels 70% 1.2% < 0.2% < 0.2% 3 quality category I I I I v quality category
of honeycomb
SI
NCS
TRIGA IQ levels
radiograph
to ASTM E 545 method
BP1
IQI item
Fig. 2. Neutron XR.
I
I
0.4% 1
7
I
4 7 IV I
Fig. 3. Silver brased seam of a copper pipe on a vacuum connec-
tor.
S. Cluzeuu et al. / Nucl. Instr. and Meth. in Phys. Res. B 99 C1995) 769-771
upper and lower hexagons are superimposed. It is nevertheless possible to detect a circular area with lack of adhesive over one of the two faces. The second figure shows a silver brazed seam of a copper pipe on a vacuum connector equipped with a rubber O-ring. The silver seal is imaged very well, and the O-ring is easy to inspect as well. An X-ray radiograph of the same sample is shown for comparison purposes. With this brief image assessment, it is important to remind that available image processing can also be used to analyze neutron radiographs, with a substantial improvement of the detail detection efficiency.
4. Conclusion These results, added to those already published [l,2], make it possible to consider neutron radiography as an
771
available and effective in-plant nondestructive testing method. Convenient equipment can be constructed using small accelerators or STNG, the later enabling one to design manoeuverable systems.
References [l] Proc. lst, 2nd. 3rd and 4th World Conf. on Neutron Radiography, held in San Diego (1983), Paris (1986). Osaka (1989) and San Francisco (1992), respectively. [2] J.P. Barton et al., Proc. 2nd WCNR. Part III (Reidel, Dordrecht, 1987) pp. 159-252. [3] S. Cluzeau, J. Huet and P. Le Tourneur. Nucl. Instr. and Meth.
B 79 (1993) 851. [4] S. Cluzeau and P. Le Tourneur, Nucl. Instr. and Meth. B 89 (1994) 428. [5] S. Cluzeau, J. Huct and P. Le Tourneur, Nucl. Instr. and Meth. B 89 (1994) 428.
XVI. TOMOGRAPHY/RADIOGRAPHY