Phoenix Neutron Imaging | How Much Do You Know About N-Ray?

Neutron imaging is a nondestructive testing method you might have heard of before, but probably haven’t had a chance to use. Despite being a powerful method for inspecting components in many industries, only a small community of NDT professionals are truly aware of neutron radiography, or N-ray.

Are you a part of this small community? Take our quiz to find out:

(Answers at the bottom of the quiz)

1. Neutron imaging is more useful than X-ray imaging for…

a. Detecting internal flaws in cast parts
b. Identifying bonding flaws in adhesives
c. Detecting and identifying the positions of o-rings, seals, lubricants, and adhesives inside complex assemblies
d. All of the above

2. Neutrons, unlike X-rays, are better for penetrating…

a. Dense materials
b. Light materials
c. Water
d. Plastics

3. Neutron radiation interacts most strongly with…

a. The electron cloud
b. The atomic nucleus
c. Photons
d. Other neutrons

4. True or false: Neutron imaging can only be done with a nuclear reactor.‍

a. True
b. False

5. True or false: Neutron imaging can be used in field work.

a. True
b. False

6. Neutron radiation is produced by:

a. Fission of uranium
b. Fusion of deuterium with tritium
c. Fusion of deuterium with deuterium
d. All of the above

7. True or false: In neutron imaging, the collimator focuses the neutron beam using electromagnets.

a. True
b. False

8. Neutron imaging has not often been used as a nondestructive testing tool because…

a. Neutrons are actually very destructive
b. Neutron imaging has only a few specific uses
c. Current imaging facilities are difficult to access
d. The objects being imaged remain “hot” for too long

9. Objects exposed to neutron radiation remain “hot” for how long?

a. About twelve hours
b. Roughly 66 hours
c. One week
d. 700 thousand years

10. What is the ASTM standard for neutron imaging?

a. ASTM E1931
b. ASTM E545 and E748
c. ASTM E1742 and E1742M
d. ASTM E1032

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Answer Key:

d. All of the above
In all of these situations and more, neutron imaging is ideal for picking up details that X-ray imaging would likely miss.
a. Dense materials
Because of the way neutrons interact with matter, they penetrate dense materials (including most metals and lead) more easily than they would pass through lighter materials (such as water and plastics).
b. The atomic nucleus
Neutrons interact with the atomic nucleus, which is why their rate of attenuation does not increase with density the way it does with X-rays. This is why neutrons pass through dense metals so easily while stopping when they reach lighter substances such as water and plastics.
b. False
Phoenix’s fusion neutron generators produce enough neutron radiation to create sharp, clear images without the burdens and supply risk associated with reactors. Our upcoming facility, PNIC, will be the first industrial radiography facility to provide neutron imaging services without the use of a reactor.
b. False
Currently, neutron imaging isn’t used for fieldwork due to the sheer scale of the technology needed to create an image in a timely fashion. However, Phoenix is continuing to work on creating more and more compact high-yield neutron sources, which will hopefully make neutron imaging more viable for fieldwork.
d. All of the above
All of these nuclear reactions and more produce neutron radiation. In all of these reactions, extra neutrons are left behind and become neutron radiation.
b. False
Because neutron radiation is comprised of neutral particles with neither a positive nor a negative charge, magnetic fields have no effect on them.
c. Current imaging facilities are difficult to access
Although neutron imaging as an industrial tool has existed since the 1950s, its near-exclusive reliance on nuclear reactors has made the technique difficult to access, especially since the number of reactors available has been declining.
a. About twelve hours
When an object is irradiated for neutron imaging or for radiation effects testing, how long it takes to “cool down” depends on what it’s made out of and how long it has been exposed to radiation. In most cases, though, the radiation drops to a safe level below 0.04 millirems within twelve hours.
b. ASTM E545 and E748
ASTM E545 describes the standard test method for determining image quality in direct thermal neutron radiographic examination and ASTM E748 is the standard guide for thermal neutron radiography of materials.

Thanks for taking our quiz. We hope you had as much fun taking this quiz as we did putting it together!

The X-ray image (left) cannot clearly depict the cooling channels in a batch of blades; however, the channels show up more clearly in a neutron image of the same batch (right).

Aircraft Turbine Blades X-Ray/Neutron Imaging Comparison

The manufacturing of jet engine turbine blades is one particular industrial niche for neutron radiography. Turbine blades are cast around ceramic molds which form cooling channels that prevent the blades from melting when exposed to the high temperatures of their operating environments. In manufacturing, fragments of ceramic can clog these cooling channels. A blade with clogged cooling channels could break or even melt while in operation, so such flaws must be rooted out with 100% certainty. The X-ray image (left) cannot clearly depict the cooling channels in a batch of blades; however, the channels show up much clearer in a neutron image of the same batch (right).

gadolinium tagging

This cross section of a turbine blade shows off one of the most useful and unique applications of industrial neutron radiography. The only way to reliably detect the ceramic fragments which can be left within a blade’s cooling channels is to wash the blade in a solution containing gadolinium, an element with a high neutron cross section. Once the gadolinium has permeated the ceramic’s porous structure, the fragments will show up in stark contrast on the resulting neutron image even after the solution has been rinsed off of the rest of the blade.

Beretta 92FS Neutron/X-Ray Imaging Comparison

Neutron radiography is especially useful for imaging munitions. In this neutron image, neutrons interact with parts within the firearm and show details that a high-energy x-ray would not depict, even the presence and position of gunpowder in the cartridge.

170kV X-ray imaging

440kV X-ray imaging

Neutron imaging

Rotary Telephone X-Ray/Neutron Imaging Comparison

X-rays and neutrons interact with materials differently, creating unique images. This rotary phone is comprised of many dense and light materials. The lower-energy 170 kV X-rays could not penetrate the denser materials of the phone. The higher-energy 440 kV X-rays could penetrate the denser materials, but was too high-energy to create an image of the lighter materials. The neutron beam could penetrate dense materials but not light materials, creating neutron radiograph that shows more detail of the phone’s inner workings than either X-ray image could on its own. The difference in how neutrons interact with light materials is what makes neutron radiography such a powerful complementary tool to X-ray radiography in materials science, materials research. and non-destructive testing applications.

Flower Neutron Images

Flowers tend to show up very distinctly on both neutron and X-ray images. However, water has a very high neutron scattering cross section, which makes neutron radiography and tomography useful for studying water uptake within root systems and rooted soil.

60kV X-ray imaging

140kV X-ray imaging

200kV X-ray imaging

Neutron imaging

Hand Plane X-Ray/Neutron Imaging Comparison

With examples such as this hand plane, it’s “plane” to see how neutron radiography and neutron images can show you details that can’t be seen with X-ray radiography. These three X-ray radiographs of varying energies, looked at as a whole, all together show almost as many details as a single neutron picture!

Welding flux on a copper plate (photo)

Welding flux on a copper plate (X-ray)

Welding flux on a copper plate (neutron image)

Welding Flux X-Ray/Neutron Imaging Comparison

Like gadolinium, boron has an extremely large neutron cross section that makes it useful as a contrast agent in neutron imaging, among other things. In this example, welding flux, which contains large quantities of borax, attenuates neutrons particularly well compared to metals such as copper. This makes neutron imaging useful for assessing the quality of welds and making certain that undesirable remnants of flux do not remain on a welded part.

MORE ON boron's neutron contrast properties

An X-Ray image of the fuel injector structures.

An N-Ray image of the fuel injector structures.

The X-ray images (top and center) miss important details regarding the fuel injectors’ structure. The N-ray image (bottom), on the other hand, offers more detail than either X-ray image alone.

Fuel Injector X-Ray/Neutron Imaging Comparison

As with the images of the rotary phone, these fuel injectors depict the differences between high and low energy X-ray images as well as neutron imaging. The image taken with 100 kV X-rays misses important details regarding the fuel injectors’ structures because the X-rays cannot easily penetrate the dense outer layers of material. However, the image taken with 190 kV X-rays also misses important details because while the X-rays can pass more easily through the denser material, they also pass too easily through the lighter material as well. Neutron imaging, on the other hand, offers more detail than either of the X-ray radiography images on their own.

In particular, two of the fuel injectors have been clogged with contaminants (we used ketchup, butter, and mustard), which show up as white blockages in the plugs in the neutron image and do not show up at all in the X-ray images. This shows the value of neutron radiography and tomography in rooting out defective parts and other non-destructive testing applications!

INTERACTIVE N-RAY/X-RAY COMPARISON

Click and drag on the vertical line to compare X-ray radiography and neutron radiography images. One advantage neutron imaging methods offer over the X-ray images is that details that did not show up on either the high-energy or low-energy X-rays, such as blockages within the fuel injectors, are visible.

225kV X-ray image

400kV X-ray image

Neutron image

Proxivision Ball Bearings X-Ray/Neutron Imaging Comparison

Click and drag on the vertical line to compare X-ray and neutron images.

Neutron Imaging of Hard Disk Drives

Because of the way neutron beams pass easily through dense metal components, the neutron image of the 3.5″ hard disk drive on the left mainly shows the less dense plastic components of the hard drive’s internal structure. the 2.5″ external hard drive on the right is entirely encased in a plastic shell which is more opaque, but not entirely opaque, to the neutron beam.

INTERACTIVE N-RAY/X-RAY COMPARISON

Click and drag on the vertical line to compare X-ray and neutron imaging. To neutron tomography, most of the metal components of the hard disk drive, such as the faceplate, the read/write heads, and the disks themselves, are completely transparent, allowing a clearer look at some components that are not as visible, if at all, in the neutron radiograph compared to the X-ray image.

We’re batty for neutron radiography at Phoenix!

Unlike X-rays, neutrons are attenuated heavily by flesh and muscle, giving a unique perspective to the radiographic image of these bat specimens. That is one of several reasons why your dentist probably isn’t interested in shooting neutron radiation at your teeth during your dental check-up.

Neutron Radiography of Consumer Electronics

Neutron radiography can provide an interesting look into consumer electronics. As in the hard drive images, the plastic tends to be more opaque to neutrons in the neutron beam than most of the electronic components, providing a unique view of the structures of these items.

Photograph

X-ray image

Neutron image

Personal Safe X-Ray/Neutron Imaging Comparison

Your secrets aren’t safe from X-ray vision or neutron vision, but both forms of radiography show quite different perspectives in these images. Plastic components, which are rich in hydrogen, are particularly opaque on the neutron images but much more transparent on the X-ray images due to the high neutron attenuation of plastics and other hydrogen compounds. A closeup of the Honeywell safe shows that neutron imaging could even pick up on the details of the embossed logo on the door to the safe!

Flashlight X-Ray/Neutron Imaging Comparison

Both neutron radiography and X-ray radiography can offer distinct advantages over each other. In these images, both depict unique features of the flashlight in question. Phoenix is currently working on imaging methods to seamlessly combine the data from X-ray and neutron imaging together into hybrid images, which would allow for an unparalleled look into an object’s inner working for cases in which both X-ray radiography and neutron radiography provide indispensable data.

*N-ray image on top. X-ray image on the bottom.

Neutron Radiography of a Jar of Staples

Click and drag on the vertical line to compare X-ray and neutron imaging. For a rather offbeat comparison of the strengths and weaknesses of X-ray and neutron imaging, we filled a glass jar with staples and a single plastic figurine. In the X-ray image, only the staples are visible. With neutron imaging, the staples are far less visible, but the figurine hidden within is entirely visible as the neutrons interact more heavily with the plastic.

How Much Do You Know About N-Ray?

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