10 CFR § 20.1005 - Units of radioactivity.

---
identifier: "/us/cfr/t10/s20.1005"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "10 CFR § 20.1005 - Units of radioactivity."
title_number: 10
title_name: "Energy"
section_number: "20.1005"
section_name: "Units of radioactivity."
chapter_name: "NUCLEAR REGULATORY COMMISSION"
part_number: "20"
part_name: "STANDARDS FOR PROTECTION AGAINST RADIATION"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "Atomic Energy Act of 1954, secs. 11, 53, 63, 65, 81, 103, 104, 161, 170H, 182, 186, 223, 234, 274, 1701 (42 U.S.C. 2014, 2073, 2093, 2095, 2111, 2133, 2134, 2201, 2210h, 2232, 2236, 2273, 2282, 2021, 2297f); Energy Reorganization Act of 1974, secs. 201, 202 (42 U.S.C. 5841, 5842); Low-Level Radioactive Waste Policy Amendments Act of 1985, sec. 2 (42 U.S.C. 2021b); 44 U.S.C. 3504 note."
cfr_part: "20"
---


# 20.1005 Units of radioactivity.

For the purposes of this part, activity is expressed in the special unit of curies (Ci) or in the SI unit of becquerels (Bq), or their multiples, or disintegrations (transformations) per unit of time.

(a) One becquerel = 1 disintegration per second (s<sub>−1</sub>).

(b) One curie = 3.7 × 10 
<sup>10</sup> disintegrations per second = 3.7 × 10 
<sup>10</sup> becquerels = 2.22 × 10 
<sup>12</sup> disintegrations per minute.

[56 FR 23391, May 21, 1991; 56 FR 61352, Dec. 3, 1991]