Radioactivity Converter
Convert Becquerel (Bq), Curie (Ci), Rutherford (Rd), dps, dpm for radioactive decay.
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*Diagram shows values relative to the selected base unit (Becquerel).
Unit Information
What is a Becquerel (Bq)?
The Becquerel (symbol: Bq) is the SI derived unit of radioactivity. One Becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second (1 Bq = 1 s⁻¹). It is named after Henri Becquerel, who discovered radioactivity. Bq is the standard international unit for measuring radioactivity.
What is a Curie (Ci)?
The Curie (symbol: Ci) is an older, non-SI unit of radioactivity, named after Marie and Pierre Curie. One Curie was originally defined as the activity of one gram of radium-226. It is now defined as exactly 3.7 × 10¹⁰ disintegrations per second (or 37 gigabecquerels, GBq). While largely superseded by the Becquerel, the Curie and its submultiples (millicurie, microcurie) are still encountered in some medical and industrial applications.
What is a Rutherford (Rd)?
The Rutherford (symbol: Rd) is an obsolete unit of radioactivity, defined as the activity of a quantity of radioactive material in which one million nuclei decay per second (1 Rd = 1,000,000 Bq or 1 MBq). It was proposed in 1946 but was not widely adopted.
What are Disintegrations per second (dps) and per minute (dpm)?
These are direct measures of the rate of decay. One dps is exactly equivalent to one Becquerel. Disintegrations per minute (dpm) is also commonly used in laboratory settings with scintillation counters. 1 dpm = 1/60 dps = 1/60 Bq.
Formulas
1 Ci = 3.7 × 10¹⁰ Bq (37 GBq)
One Curie is exactly 37 billion Becquerels.
1 Bq = 1 dps
One Becquerel is equivalent to one disintegration per second.
1 Bq = 60 dpm
One Becquerel is equivalent to 60 disintegrations per minute.
A = A₀ * e^(-λt)
The radioactive decay law, where A is the activity at time t, A₀ is the initial activity, and λ is the decay constant.
λ = ln(2) / T½
The decay constant (λ) is related to the half-life (T½) by the natural logarithm of 2.
Key Reference Points
- Radioactivity of an adult human body (due to potassium-40): ~4,000-5,000 Bq.
- A typical household smoke detector (americium-241 source): ~30,000 Bq (or ~0.8 microcuries).
- Medical diagnostic dose of Technetium-99m: Often in the range of hundreds of MBq (millions of Becquerels) or tens of mCi (millicuries).
- One gram of Radium-226: Has an activity of approximately 1 Curie (37 GBq).
- A typical Granite countertop can emit low levels of radiation, contributing a very small amount to background levels.
- 1 Becquerel (Bq) is a very small unit of activity.
- 1 Curie (Ci) is a very large unit, representing 37 billion decays per second.
- The Megabecquerel (MBq) is a common unit in medical imaging.
- A Picocurie (pCi) is often used for measuring environmental radon levels.
- The Rutherford (Rd) is equal to 1 MBq.
Did You Know?
Radioactivity is a natural phenomenon. Elements like potassium-40 (found in bananas and many other foods), carbon-14 (used for radiocarbon dating), and radon gas (emanating from the ground) are naturally radioactive. Our bodies contain small amounts of these isotopes, contributing to our natural background radiation exposure.
The half-life of a radioactive isotope is the time it takes for half of the radioactive atoms in a sample to decay. Half-lives can range from fractions of a second to billions of years.
Carbon-14 dating uses the known decay rate of carbon-14 (half-life ~5730 years) to estimate the age of organic materials, such as archaeological artifacts.
A Geiger counter is a well-known instrument for detecting ionizing radiation. It works by using a gas-filled tube that conducts electricity when a particle or photon of radiation passes through it, creating an audible 'click'.
Radioactive decay is a random, or stochastic, process. It is impossible to predict when a single specific nucleus will decay. However, for a large number of nuclei, the overall decay rate can be accurately described by the half-life.
In 1896, Henri Becquerel discovered radioactivity by accident when he found that uranium salts could fog a photographic plate even in the dark, revealing the emission of a previously unknown type of penetrating radiation.
Positron Emission Tomography (PET) is a nuclear medicine imaging technique. It uses short-lived radioactive tracers that emit positrons. When a positron annihilates with an electron in the body, two gamma rays are produced, which are detected to create a 3D image of functional processes.
RTGs are a type of nuclear battery used to power spacecraft like the Voyager probes and Mars rovers. They use the heat generated by the decay of a radioactive material (like plutonium-238) to produce electricity via thermocouples.
The 'demon core' was a sphere of plutonium used in criticality experiments at Los Alamos during the Manhattan Project. Two separate incidents involving mishandling of the core resulted in physicists receiving fatal radiation doses, highlighting the dangers of working with highly active materials.
Marie Curie's notebooks from the 1890s are still radioactive and are kept in lead-lined boxes. To view them, one must wear protective clothing.
The Rutherford (Rd) was an early unit of radioactivity, defined as the amount of a substance that undergoes one million decays per second (1 MBq). It was proposed in 1946 but was quickly superseded by the Curie and later the Becquerel.
High-energy cosmic rays interacting with atoms in the atmosphere continuously produce radionuclides, such as Carbon-14 and Beryllium-7. These 'cosmogenic' isotopes are a source of natural background radiation.
Geologists use the decay of long-lived isotopes like Uranium-238 (half-life 4.5 billion years) and Potassium-40 (half-life 1.25 billion years) to determine the age of rocks and the Earth itself.
At Oklo in Gabon, Africa, there are several sites where self-sustaining nuclear fission reactions occurred naturally about 1.7 billion years ago. This was possible because the natural concentration of fissile uranium-235 was higher at that time.
These are the three most common types of radioactive decay. Alpha decay emits a helium nucleus. Beta decay emits an electron or positron. Gamma decay emits a high-energy photon. Each has different penetration and ionization properties.
In a radioactive decay chain, secular equilibrium is reached when the half-life of the parent isotope is much longer than the half-life of its daughter isotope. When this occurs, the daughter isotope decays at the same rate it is being produced, so their activities become equal.
Many ionization-type smoke detectors contain a tiny amount of the radioactive isotope Americium-241. It emits alpha particles that ionize the air in a chamber, allowing a small current to flow. Smoke particles disrupt this current, triggering the alarm.
In nuclear medicine, radioisotopes like Technetium-99m are attached to pharmaceuticals to create radiotracers. These are injected into the body and their decay (gamma rays) is imaged to diagnose diseases or assess organ function.