Radiation exposure by Time, Distance, Shielding

Question 1

4 basic methods of controlling internal radiation

Answer 1

Avoiding Inhalation- using engineering controls, i.e ventilation. Respirators

Avoiding Ingestion- Administrative controls, no food, beverages. Minimize surface contamination.

Avoiding Absorption- Protective clothing in a contaminated area. If liquid radioactive material used cover with absorbent paper.

Wound Decontamination- simple wet debridement.

Question 2

Three basic methods for controlling external radiation exposure

Answer 2

Minimize time- time spent in radiation field

Increase Distance- Increase distance from source

Utilize Shielding- material between the radiation source. Permanent and temporary. Lead, bags filled with led.

Question 3

How time distance shielding is used in medical setting

Answer 3

Time- through understanding of task. Preparation and practice. We’ll acquainted with fluoroscopy. Reduce time unshielded.

Distance- stand as far away as possible during x-ray. Use tongs to increase distance

Shielding- utilize aprons, lead pigs, syringe shields.

Question 4

Time distance and shielding are utilize in a nuclear setting

Answer 4

Time- plan job, pre-job briefings, work packages, mock up training. If able work out side radiation area.

Distance- move component being worked to an area of lower background radiation. Remote equipment. Work at arms length.

Shielding- temporary lead shielding. Work behind structural components.

Question 5

Time distance shielding are used in radiography

Answer 5

Time- don’t stay near a radiograph. Stage work area. Leave area during delays.

Distance- stay as far away from the source as practicable.

Shielding- utilize shielding between work locations and the source.

Question 6

Half-value layer

Answer 6

Thickness of a given material required to reduce the intensity of a beam of gamma to 1/2

Question 7

Tenth value layer

Answer 7

Thickness of a given material required to reduce the intensity of a beam of gamma to 1/10 original value.

Question 8

Tenth-value layers for Co-60

Answer 8

Lead- 2 niches
Steel- 4 inches
Water/polyethylene/
Oil- 2 feet (24 inches)

Question 9

Formula for exposure

Answer 9

E = I x T

I = e / t

T= e/i

Question 10

Stay time

Answer 10

Period a person may remain in a radiation area without exceeding a predetermined dose.

Reduce unnecessary exposure based on local control levels

Question 11

Point Source / Line source

Answer 11

Point Inverse square law

i1, r1^2 = i2, r2^2

Line, inverse law