Answers test examination
| # | choice | # | choice | # | choice | # | choice |
|---|---|---|---|---|---|---|---|
| 1 | B | 11 | A | 21 | D | 31 | A |
| 2 | A | 12 | B | 22 | C | 32 | A |
| 3 | C | 13 | D | 23 | B | 33 | D |
| 4 | B | 14 | C | 24 | D | 34 | B |
| 5 | C | 15 | A | 25 | C | 35 | D |
| 6 | B | 16 | D | 26 | A | 36 | C |
| 7 | B | 17 | A | 27 | D | 37 | D |
| 8 | A | 18 | C | 28 | C | 38 | D |
| 9 | C | 19 | D | 29 | B | 39 | A |
| 10 | D | 20 | B | 30 | C | 40 | C |
evaluation question 41:
Distance source - surface box = 40 cm / 2 = 20 cm = 0.2 m
Equivalent dose rate at 1 m from 4 GBq = 4000 MBq 137Cs
–› 0.093 μSv·m2·MBq-1·h-1 × 4000 MBq = 370 μSv per hour = 0.37 mSv per hour
Equivalent dose rate at surface box without shielding
–› 0.37 mSv per hour × (1 m / 0.2 m)2 = 9 mSv per hour
Equivalent dose rate on surface box with shielding
–› 0.1 × 9 mSv per hour = 0.9 mSv per hour
evaluation question 42:
Activity = 100 GBq = 100×103 MBq
Time = 10 s = 0.0028 h
Equivalent dose at 1 meter
–› 0.12 μSv·m2·MBq-1·h-1 × 100×103 MBq × 0.0028 h = 34 μSv
Equivalent dose rate at 50 cm = 0.5 m
–› 34 μSv × (1 m / 0.5 m)2 = 140 μSv = 0.14 mSv
Annual limit for exposed A-worker = 20 mSv
Maximal time
–› 0.0028 h × (20 mSv / 0.14 mSv) = 0.4 h = 24 min