Chapter 10 Radiographic Inspection

Question 1

1. X-rays are a type of electromagnetic wave but gamma rays are beams of tiny charged particles.

a. True
b. False

Answer 1

b. False

Question 2

2. List three disadvantages of radiography over other inspection methods.

Answer 2

Bulky equipment,
special safety precautions,
some defects not reliably detected

Question 3

3. Sketch the main components of an X-ray machine then compare your sketch with that shown in Figure 137.

Answer 3

Question 4

4. Do gamma rays generally have a greater or lesser ability to penetrate thick steel than X-rays?

Answer 4

Greater

Question 5

5. List three disadvantages of gamma rays over X-ray radiography?

Answer 5

Radiation emitted continuously
Radiation hazard
Penetration power cannot be adjusted

Question 6

6. For a given intensity of X-rays striking a specimen, what are the two main factors that affect the intensity that emerges from the specimen to strike the film?

Answer 6

Thickness and type of material

Question 7

7. The only thing that causes fuzziness at the edge of an image is geometric unsharpness.

a. True
b. False

Answer 7

False, fuzziness is also caused by inherent unsharpness and scattering

Question 8

8. List the three dimensions that affect geometric unsharpness and the relationship among them (Ug=Ft/d equation).

Answer 8

Source size,
F; object-to-source distanced;
thickness, t, Ug = Ft/d

Question 9

9. What is the simplest way of reducing the geometrical unsharpness for a given plate and X-ray machine?

Answer 9

Increase the object (plate)-to-source distance

Question 10

10. The purpose of the IQI is to verify that all defects greater than 286 of the plate thickness have been detected.

a. True
b. False

Answer 10

b. False

Question 11

11. What features of the IQI image must be clearly distinguished on the radiograph when using X-ray?

Answer 11

Outline of the IQI and the essential T size hole or wire diameter

Question 12

12. Some dark crack-like indications appear on a radiograph. If they are not due to cracks in the actual specimen what else could they result from?

Answer 12

Scratches or cracks in the lead intensifying screens

Question 13

13. What is the specified range of density of a radiograph according to most codes?

Answer 13

1.5 to 3.5

Question 14

14. Since radiography is a volumetric method the condition of the surface is not an important factor.

a. True
b. False

Answer 14

b. False

Question 15

15. How would you distinguish spatter from porosity on a radiograph?

Answer 15

Spatter appears white or light and may cover the base metal as well as the weld. Porosity is normally confined to the weld metal and appears dark

Question 16

16. Radiography is not recommended by CSA W59 for fillet welds.

a. True
b. False

Answer 16

a. True

Question 17

17. Give two reasons why the source is not always placed inside cylinders or pipes when radiographing welds.

Answer 17

There may not be access to the inside; it may not be possible to get adequate source-to-film distance inside.

Question 18

18. How many shots would be required to radiograph a splice weld in a rectangular hollow structural section where there is no access to the inside?

Answer 18

Four

Question 19

19. Good visual inspection should always be used in conjunction with radiography.

a. True
b. False

Answer 19

a. True

Question 20

20. What is the recommended delay after welding before doing radiography on high restraint joints (according to CSA W59)?

Answer 20

48 Hours

Question 21

21. If a product is to be stress relieved, why is it important to use exactly the same procedure for radiography after stress relief as is used before?

Answer 21

To prevent borderline indications that could be interpreted differently before and after stress relief

Question 22

22. According to CSA W59, when doing spot radiography what minimum length of weld must each spot show?

a. 50 mm
b. 100 mm
c. 200 mm

Answer 22

b. 100 mm

Question 23

23. What do the letters CGSB stand for?

Answer 23

Canadian General Standards Board

Question 24

24. List some of the items you would look for when checking a procedure for radiography.

Answer 24

Some would be a sketch, 
governing standards, 
equipment, 
type of source, 
geometric arrangement, 
source-to-film distance, 
type of film and 
processing

Question 25

25. Which organization in Canada controls the use of gamma ray devices?

Answer 25

Canadian Nuclear Safety Commission (CNSC)

Question 26

26. Sketch from memory the international radiation hazard sign (trefoil), then compare your sketch with that in Figure 191.

Answer 26

Question 27

27. The emission of gamma rays from a radioactive isotope cannot be switched off; the source can only be retracted into a shielding container.

a. True
b. False

Answer 27

a. True

Question 28

28. If 1000 rays strike a shielding plate that is twice the TVL thick, how many rays emerge on the other side?

Answer 28

10

Question 29

29. If point B is 4 times as far from a radiation source as point A, how much lower will the intensity of radiation be at point B than point A?

Answer 29

16 times lower

Question 30

30. What is the SI equivalent unit to rem?

Answer 30

Sievert (Sv)