Radioactive alpha decay in smoke detectors


This paper provides the information of the radiation, the procedure of radioactive decay, peculiarly in the emanation of alpha atom ( alpha decay ) and its applications in the recent engineering of fume sensors. The intent and aims of the research workers in making the research of this subject is that the research workers are largely interested in the development of radiation within our day-to-day lives and thereby a farther research, deep apprehension and thorough analysis to increase the cognition about radioactive decay is perfectly necessary. In fact, a to the full detailed research on the alpha decay for Americium-241, who discovered it, as an alpha emitter and is normally produced from an unreal transubstantiation and used in fume sensors, is the chief aim of this research.

Furthermore, in item, many aims and common but necessary enquiries are inquired by the research workers for radioactive alpha decay understanding, such as what do the fume sensors to work and what cause the alpha particles to be inflicted in an alpha decay or what chemical substance or any external factors that trigger the fume sensors to be working, what happens within the procedure of Americium-241 alpha decay, what is the consequence, consequence and functionality in fume sensors and how the fume sensors work in the cause of Americium-241 decay being. The consequence of Americium-241 towards environment, homo ‘s organic structure and engineering will besides be explained briefly in this paper.


Atoms are cardinal units that compose affair. In a individual atom, monolithic nucleons ( composed of protons ( positively charged ) and neutrons ( impersonal ) ) are surrounded by negatrons ( negatively charged ) in their orbits based on their energy degrees, runing from the lowest energy degree ( nearest to the nucleons ) to the highest energy degree ( furthest to the nucleons ) . Generally, an atom ‘s size ( the radius from the most outside negatron to the nucleons ) is measured by utilizing the unit of Angstrom, whereas 1 Angstrom is the same as 10-10 metres or 0.1 nanometres ( Russell, 2008 ) .

The Numberss of protons inside the nucleons of an atom reflects the component of the atom itself. Therefore, different elements have different figure of protons inside their nucleons ( or besides known as atomic figure ) . For illustration, Americium is placed on figure 95 in periodic tabular array. This means, Americium component has an atomic figure of 95 and it has 95 protons in its nucleons. Most elements have different atomic mass or the different figure of neutrons, but with the same sum of protons, which is called “ isotopes ” . For illustration, the isotope Americium-243 ( 243Am ) has 95 protons and 148 neutrons, so the atomic mass is 243. Another isotope of this component is Americium-241 ( 241Am ) , which has 95 protons and 146 neutrons, so the atomic mass is 241.

Quarks are the simple atoms that form protons and neutrons in an atom. Within this subatomic atom degree, there is a strong binding force between protons and neutrons to organize nuclei. This force, which is the strong residuary force or largely known as atomic force. Furthermore, protons and neutrons tend to drive themselves due to their like charges by a abhorrent electromagnetic charge. However, they are bound to organize a karyon by a stronger attractive atomic force, so that the weaker abhorrent force does non impact the signifier of edge karyon.

Nuclei have their ain stable sum of nucleons. All elements that have the sum of nucleons less than 208 are stable elements. As there are more nucleons in a karyon, the radius of nucleus additions and the attractive atomic force weakens. Hence, the outer nucleons have the inclination to drive with other nucleons. This behavior causes the component to be unstable, and it is found that elements with sum of nucleons greater than 208 possess this instability. As the radius of nucleons is increased, the radioactive behaviour is increased every bit good and it tends to disintegrate to a wholly stable component ( stable to alpha, beta and gamma decay ) .

Within the degree of hadron constituent, protons and neutrons constituent are bound by a binding force, or known as the term of quantum chromodynamics ( QCD ) . By and large, there are interactions between quarks and gluons within protons and neutrons. This interaction is largely known as colour charge and three quarks in a proton/neutron tend to interchange their colour one another. These three quarks in a proton/neutron is assumed as Red, Green and Blue, because the combination of these three colourss is white or color-neutral.


In 1896, Antoine Henri Becquerel conducted an experiment where he could non utilize the Sun radiation as the beginning of the energy he needed. When he put photographic home bases together with a crystal contained an sum of U, some fagot and surprising phenomenon occurred. The U emitted an unseeable radiation itself without the presence of any energy beginning. Although Becquerel was cognizant of this phenomenon, he did non look farther into this instance as he did non analyze about radiation. ( Slowiczek, 2008 )

On 1898, Marie Curie and Pierre Curie did an experiment to detect the substance that could turn air into a electricity music director with uraninite and U. Both of them found that the uraninite ( UO2 ) had the ability to bring forth current several hundred times stronger than pure U could. This unknown phenomenon was besides confused them, and they thought an active substance must had existed within the uraninite to meet this phenomenon, and so, they introduced the term of “ Radioactive ” ( Slowiczek, 2008 )

In 1911, Ernest Rutherford performed an experiment where he ejected an alpha atom beam emitted from the decay of a radioactive stuff onto a thin gold foil. He observed that most of the atoms passed through the gilded foil absolutely without any hits, saying the gold foil was composed of largely empty infinite, alternatively of a solid affair. Nevertheless, some atoms collided with gold atoms and bounced back, demoing that the gold foil was a solid affair. In this experiment, Rutherford showed that atoms consisted of empty infinite with karyon in the Centre. Rutherford besides showed that unstable elements possess a radioactive behaviour and they decay over clip. He was besides the first to carry on an unreal transubstantiation between elements ( Slowiczek, 2008 ) .

  1. Radiation

The term of radiation means an atom emanation from an unstable atomic karyon. It happens because the reaction between abhorrent electromagnetic force and atomic force affects peculiar karyons and the size of nucleons affect the radioactive behaviour every bit good. This unstable atomic isotope produces radiation, such as alpha ( ? ) , beta ( ? ) and gamma ( ? ) radiation ( Nave, n.d. )

Most unstable elements decay through any decay procedure, whether it is alpha decay, beta decay or gamma radiation to bring forth a wholly stable nuclide. Some elements need to undergo through several decays before a stable nuclide is formed. Decay concatenation is a procedure of several stairss of radioactive decays that returns from an unstable parent nuclide to a girl nuclide with unstable atomic behaviour ( or instead called as radiation behaviour ) . This girl nuclide decays and produces radiation within a sequence until a stable nuclide is produced. Some isotopes may take 3-4 stairss until a stable girl nuclide is green goodss, while some may take more than 10 decays to bring forth one stable nuclide.

Alpha Decay

Alpha decay is one of radiation ‘s types where an alpha atom is emitted by the karyon of atom and so disintegrate into an atom with ( X-4 ) atomic mass and ( Z-2 ) atomic figure, whereas Ten means the original figure of atomic mass and Z is the original atomic figure. For illustration, alpha decay happens when Berkelium-245 decays into Americium-241 with the add-on of alpha atom emanation. Normally alpha decays go on in a solid karyon that has a big sum of ratio between protons to neutrons.

When anunstable atom decays through an alpha decay an emits an alpha atom, its girl nuclide ‘s atomic mass lessenings by four because of the release of four nucleons and its atomic figure lessenings by two since the parent nuclide release two protons in the decay procedure. Therefore, the new atom becomes a new component with different sum of protons and nucleons with the parent nuclide. For case, an isotope berkelium-245 transforms into isotope of Americium-241 through an alpha decay procedure.


Americium-241 ( Am-241 ) was foremost produced by Dr. Glenn Seaborg and his colleagues in 1944. This component is named after America, since it was discovered in the University of Chicago, USA ( Ocular Elements – Americium, n.d. ) .

This component can be seen as a silvern white metal which is able to be be tarnished easy in dry air at room temperature. It is humanly produced unnaturally by alpha decay from brekelium isotopes ( EVS, 2005 ) . The atomic mass of Americium-241 is 245.056823 U and it has a half life of 432 old ages. The possible parent of this component is beta decay from Pu-241 ( Plutonium-241 ) , electron gaining control from Cm-241 ( Curium-241 ) and alpha decay from Bk-245 ( Berkelium-245 ) . The extra mass that is emitted by this component is 52930 KeV ( Americium-241, 2009 ) . If Americium-241 goes through another alpha decay, it will transform into Neptunium-237 as the girl nuclide.

For the application, this component is normally used in fume sensors. Smoke sensors normally depend on the combination of the decay of this component and the alpha atom that was emitted in the decay procedure. Other engineering and applications that normally use Americium-241 are gamma radiograhy, aim stuff in atomic reactores and crystallography ( EVS, 2005 ) .

Enviromental Am was generated by the atmospheric testing of atomic arms which stopped worldwide in 1980s. The accidents happened from weapon production mills which caused localised taints and therefore, americium oxide is really common in the environment. Approximately, there are 0.01 picocurioes of this component in every surface dirt ( EVS, 2005 ) . This component is non easy dissolved yet it may be dissolved through chemical and biological procedure.

It is uncommon for people to come in contact with Americium-241. However, when this component acquire into the human organic structure, this component will most likely to remain in the bone, musculus and liver. This component has a large possibility of remaining in the human organic structure for old ages and will increase the hazard of developing malignant neoplastic disease if it is exposed by radiation. A manner for this component to acquire into the human organic structure is through inspiration. When it does acquire into the human lungs, it will most likely to stay at that place. The atom size and the chemical signifier consequence its result. If the easy dissolved chemical signifier is inhaled by the human lung, it will go through into the blood stream. However, if the less easy dissolved chemical signifiers is inhaled by the human lungs, the component will travel to the lung ‘s natural defence system, acquire swallowed of course by the human itself and base on ballss from the organic structure through the fecal matters ( EVS, 2005 ) .


Smoke sensors, which we can see everyplace presents, are fundamentally consist an dismay. The sensors themselves can run with a simple 9V battery to 120V house electric current. As explained before, smoke sensors differ on how they work, some usage visible radiation, some use the radiation emanation from a radioactive stuff and many more.

There are smoke sensors that use light and they are normally called photoelectric fume sensors. These sensors use a light beginning to bring forth visible radiation and so utilize the fume particles that enter inside the sensor to resile the visible radiation to the detector. They normally use photodiode for the detector, because of its sensitivity against visible radiation. These sensors are rather large and uneffective because the visible radiation will resile merely if the fume is thick plenty to resile the light photons. Otherwise, the visible radiation will merely merely travel consecutive and will ne’er hit the detector or it will non resile accurately to the visible radiation detector to put off the dismay. Therefore, the dismay will non trip.

On the other manus, fume sensors that use radiation emitted from a radioactive stuff are smaller and more effectual against little sum of fume. They call it ionisation smoke sensors because the sensors use ionisation radiation and it consists an ionisation chamber in the mechanism of dismay triggering.

Ionization radiation is radiation which uses energy to strike hard off electron out of some atoms, doing the atoms to be charged, go forthing a free negatron. While the ionisation chamber itself is really a normal chamber that the ionisation radiation takes topographic point. The chamber consists of two home bases charged by either batteries or other current. One of the home bases is charged by a positive charge, while the other home base is charged by a negative charge. The other portion in these sensors is the beginning of the radiation ; they use a really little sum of americium-241 as the beginning of the radiation which they put it near the home bases in the chamber.

Apart from utilizing detector like photoelectric sensors, ionisation smoke sensors make usage of the current degree. When the americium-241 is released, they ionized the atoms in the air, making an ionisation radiation. As explained before, the radiation will do the atoms to lose negatron and to be charged. The negatrons that are knocked off will attracted to the positive charged home base, while the charged atoms will attracted to the negative charged home base. This activity will do a little sum of current, but when the fume enters the chamber, they will interrupt the activity because the atoms of the fume attach themselves to the both atoms and negatrons, forestalling them to make the home base. This will finally drop the current degree that was produced by the charged atoms and the negatrons before. When the current beads into a certain degree, the dismay will trip automatically.

In a fume sensor, the alpha radiation emitted from the Americium-241 stuff is really little and it is harmful towards human organic structure. Since Americium-241 can be distributed in the air, a individual can inhale the element isotope of Americium-241. Because of its injuriousness towards human organic structure, it is suggested that people do non play with any application or engineering devices that use a substance of Americium-241.

There are many advantages of holding sensors in either private or public topographic points. these advantages are the decrease of losingss due to fire, the minimisation of outgo spent due to the fire and the lessening of pollution which can harm the human organic structure every bit good as the Earth itself by this fume sensor device. Furthermore, tobacco users will hold their smoke jobs cured by the presence of fume sensors as they will avoid smoke in edifices that have smoke sensors installed. Hence, the chance of undertaking smoke diseases, such as malignant neoplastic disease, bosom diseases, etc. can be reduced. Millions of lives can besides be saved by fume sensors and salvaging the disbursal of 1000000s of dollars because of the fire occurred. ( Chaudhari, n.d. ) .


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