放射性是不稳定原子核因辐射失去能量的过程。它以Becquerels（BQ）进行测量。
1 RD = 100 rem
1 rem = 0.01 RD
例子:
将15 辐射衰减转换为REM：
15 RD = 1,500 rem
| 辐射衰减 | REM |
|---|---|
| 0.01 RD | 1 rem |
| 0.1 RD | 10 rem |
| 1 RD | 100 rem |
| 2 RD | 200 rem |
| 3 RD | 300 rem |
| 5 RD | 500 rem |
| 10 RD | 1,000 rem |
| 20 RD | 2,000 rem |
| 30 RD | 3,000 rem |
| 40 RD | 4,000 rem |
| 50 RD | 5,000 rem |
| 60 RD | 6,000 rem |
| 70 RD | 7,000 rem |
| 80 RD | 8,000 rem |
| 90 RD | 9,000 rem |
| 100 RD | 10,000 rem |
| 250 RD | 25,000 rem |
| 500 RD | 50,000 rem |
| 750 RD | 75,000 rem |
| 1000 RD | 100,000 rem |
| 10000 RD | 1,000,000 rem |
| 100000 RD | 10,000,000 rem |
规则