1

Americium-241

6 × 10 ¹¹

2

Americium-241/Beryllium

6 × 10 ¹¹

3

Caesium-137

1 × 10 ¹²

4

Californium-252

2 × 10 ¹¹

5

Cobalt-60

3 × 10 ¹¹

6

Curium-244

5 × 10 ¹¹

7

Gadolinium-153

1 × 10 ¹³

8

Iridium-192

8 × 10 ¹¹

9

Plutonium-238

6 × 10 ¹¹

10

Plutonium-239/Beryllium

6 × 10 ¹¹

11

Promethium-147

4 × 10 ¹⁴

12

Radium-226

4 × 10 ¹¹

13

Selenium-75

2 × 10 ¹²

14

Strontium-90/Yttrium-90

1 × 10 ¹³

15

Thulium-170

2 × 10 ¹⁴

16

Ytterbium-169

3 × 10 ¹²