Neutron Radiographic Testing (NR) Review Questions

Question 1

1. The highest intensity sources of thermal neutrons are?
A. Cf-252 isotopes
B. Accelerators
C. Nuclear fission reactors
D. Cosmic radiation

Answer 1

C. Nuclear fission reactors

Question 2

2. Neutrons for fast-neutron radiography are not obtainable from:
A. Accelerators
B. Radioactive sources
C. Reactors
D. X-Ray machines

Answer 2

D. X-Ray machines

Question 3

3. A radioactive source used for neutron radiography is:
A. Pu-239
B. Co-60
C. Cs-137
D. Cf-252

Answer 3

D. Cf-252

Question 4

4. The energy of the neutron is expressed in which of the following units of measurement?
A. Curies (becquerels)
B. Roentgens (coulombs per kilogram)
C. Rems (sieverts)
D. Electron volts

Answer 4

D. Electron volts

Question 5

5. A normally desirable feature of a thermal neutron beam fo neutron radiography is:
   A. Background gamma radiation intensity
   B. Relatively low fast-neutron intensity
   C. Low angular divergence
   D. Relatively high thermal neutron intensity

Answer 5

B. Relatively low fast-neutron intensity

Question 6

6. Material that slows down neutrons is called?
A. A moderator
B. A accumulator
C. A limitor
D. A collimator

Answer 6

A. A moderator

Question 7

7. The primary radiation mechanism for darkening X-ray film when the direct neutron radiography process is used with gadolinium screens is?
A. Alpha particles
B. Electrons
C. Gamma rays
D. Light emission

Answer 7

B. Electrons

Question 8

8. Neutron radiography using the transfer method requires that the imaging screen must:
A. Be placed behind the film
B. Be placed in front of the film
C. Be very thin
D. Become radioactive

Answer 8

D. Become radioactive

Question 9

9. Which of the following neutron radiography converter foils cannot be used for transfer or indirect radiography?  
A. Dysprosium
B. Indium
C. Gadolinium
D. Gold

Answer 9

C. Gadolinium

Question 10

10. The most suitable films for producing neutron radiographs are:
    A. Red sensitive films
    B. Instant-type films
    C. Industrial X-Ray films
    D. Emulsions that contain no silver halides

Answer 10

C. Industrial X-Ray films

Question 11

11. Materials that are exposed to thermal neutron beams:
    A. Must not be handled for at least 3 min after exposure has ceased
    B. Must be stored in a lead-lined room
    C. May be radioactive after exposure to neutrons has ceased
    D. Should be monitored by means of neutron counter

Answer 11

C. May be radioactive after exposure to neutrons has ceased

Question 12

12. Lead is:
A. A good neutron shield 
B. Corroded by neutron exposures
C. A relatively poor neutron absorber 
D. An efficient conversion screen

Answer 12

C. A relatively poor neutron absorber

Question 13

13. If 2 mm (0.08”) of plastic attenuated a thermal neutron beam by a factor of 2, then 20 mm (.8”) will attenuate it by approximately a factor of:
A. 10
B. 20
C. 200
D. 1,000

Answer 13

D. 1,000

Question 14

14. Materials in common usage for moderation of fast-neutron sources include:
    A. Aluminum, magnesium and tin
    B. Water, plastic, paraffin and graphite
    C. Neon, argon and xenon
    D. Tungsten, cesium, antimony and columbium

Answer 14

B. Water, plastic, paraffin and graphite

Question 15

15. The main reason for using neutron radiography in place of X-Radiography is:
    A. A lower cost
    B. Higher resolution
    C. The ability to image objects and materials not possible with X-Rays
    D. It is a simpler radiographic procedure when required than X-Radiography

Answer 15

C. The ability to image objects and materials not possible with X-Rays

Question 16

16. A photographic record produced by the passage of neutrons through a specimen onto a film is called?
A. A fluoroscopic image
B. A radiograph 
C. An isotopic reproduction 
D. A track-etch photograph

Answer 16

B. A radiograph

Question 17

17. Many of the absorption differences between neutrons and x-rays indicate that the two techniques
    A. Cause radiation problems
    B. Complement each other
    C. Can be used interchangeably
    D. Can both be used to image hydrogenous materials equally well

Answer 17

B. Complement each other

Question 18

18. The penetrating ability of a thermal neutron beam is governed by:
    A. Attenuating characteristics of the material being penetrated
    B. Exposure time
    C. Source-to-film distance
    D. Thickness of the converter screen

Answer 18

A. Attenuating characteristics of the material being penetrated

Question 19

19. The transfer exposure method is used because:
    A. It is not influenced by gamma radiation in the primary beam
    B. It produces greater radiographic sensitivity than direct exposure using gadolinium
    C. It is faster than the direct exposure method
    D. The screens used in this method emit only internal conversion electrons of about 70 keV

Answer 19

A. It is not influenced by gamma radiation in the primary beam

Question 20

20. Higher resolution can be achieved in direct neutron radiography by:
    A. Placing a lead intensifying screen between a gadolinium screen and film
    B. Increasing the L/D ratio of the collimation system
    C. Increasing the exposure time
    D. Increasing the distance between the object and the film cassette

Answer 20

B. Increasing the L/D ratio of the collimation system

Question 21

21. The primary advantage of using a Cf-252 source for neutron radiography is its:
    A. Portability
    B. Low cost per unit neutron flux compared to other neutron radiographic sources
    C. High resolution
    D. Long useful life

Answer 21

A. Portability

Question 22

22. Quality of the results from a neutron radiographic exposure is best determined by:
A. Reference standards
B. Image quality indicators 
C. Neutron flux measurement
D. Densitometer readings

Answer 22

B. Image quality indicators

Question 23

23. The radiographic image of flaws in the imaging screens can be separated from actual flaws in a part being radiographed by:
    A. Producing a photographic copy of the original neutron radiograph using X-ray duplicating film
    B. Comparing a neutron radiograph of the parts to a blank neutron radiograph of the same imaging screen with no parts in place
    C. Increasing the exposure time of the radiograph
    D. Decreasing the temperature of the developer solution

Answer 23

B. Comparing a neutron radiograph of the parts to a blank neutron radiograph of the same imaging screen with no parts in place

Question 24

24. For inspection of radioactive objects or those that emit gamma radiation when bombarded with neutrons, a preferable detection technique is the:
    A. Direct exposure technique
    B. Transfer technique
    C. Isotopic reproduction technique
    D. Electrostatic-belt generator technique

Answer 24

B. Transfer technique

Question 25

25. Neutron radiography is an excellent tool for determining:
    A. The coating thickness of aluminum oxide on anodized aluminum
    B. The size of voids in thick steel castings
    C. The integrity of thin plastic material within a steel housing
    D. Tungsten inclusions in GTAW welds

Answer 25

C. The integrity of thin plastic material within a steel housing

Question 26

26. Neutron radiography extends radiographic capability for detecting cracks in small cylinders of:
A. Aluminum
B. Iron 
C. Magnesium 
D. Plutonium

Answer 26

D. Plutonium

Question 27

27. Which of the following is not a preferred application of neutron radiography?
    A. Detecting the presence or absence of explosive material contained within a metal device
    B. Detecting the presence of water in the cells of stainless steel honeycomb
    C. Detecting the proper alignment of a rubber seal in a small steel valve assembly
    D. Detecting the presence of a lead rupture diaphragm in a small aluminum safety valve assembly

Answer 27

D. Detecting the presence of a lead rupture diaphragm in a small aluminum safety valve assembly