Helium-3 (³He)

Data nuklida

Unsur

Helium (He, Z = 2)

Nomor massa (A)

3

Proton (Z)

2

Neutron (N)

1

Massa atom

3.01602932197 ± 0.00000000006 u

Waktu paruh

Stabil

Mode peluruhan

Tidak meluruh

Kelimpahan alami

0.000 002(2)

Tahun penemuan

1934

Sumber data

IAEA Atomic Mass Data Center (NUBASE) and IUPAC CIAAW, via PubChem

Kegunaan isotop helium

• 3He is a product of the radioactive decay of 3H (half-life of 12.31 years). The relative variations in the amount ratio n(3He)/n(3H) can be interpreted in terms of elapsed time. This has been especially useful in aquatic systems, including oceans, lakes, and aquifers, that received large inputs of 3H from precipitation following thermonuclear bomb test periods. 3H- 3He dating provides the elapsed time since a water mass became isolated from the atmosphere in the time range from the mid-1950s to the present. Such studies are important for establishing the sustainability of groundwater resources in shallow aquifers,. 4He is a product of radioactive decay in the uranium and thorium decay series. As a result, 4He concentration is used to estimate the relative ages of minerals and groundwater. In closed systems (systems that do not exchange matter with their surroundings), relative variations in the amount ratio n(4He)/n(U) can be interpreted in terms of elapsed time, although other processes can alter the distribution of helium, which is highly mobile in terrestrial environments,. 4He concentrations commonly increase along groundwater flow paths through a cumulative release from aquifer materials. This rate of accumulation is used to estimate the time since the groundwater was recharged at the surface. The 4He accumulation method of groundwater dating is typically used in deeper aquifers, where groundwater is relatively old and the 3H- 3He method cannot be used because of the relatively short half-life of 12.31 years for 3H.
• 3He has a large absorption cross section for neutrons, which makes it especially useful for radioactivity detection,. In this application, neutrons produced by the radioactive decay of elements, such as uranium and plutonium, enter the detector, where the reaction 3He (n, p) 3H produces 1H and 3H atoms. This induces further collisions and the release of electrons, which interact with charged surfaces to generate an electric current. Large amounts of 3He are used to produce neutron detectors in portal monitors for detecting illicit radioactive materials at ports, border crossings, and airports (Fig. IUPAC.2.1). Unfortunately, the isotope 3He is rare and there is a need to incorporate alternative gases for use in neutron detectors. 3He neutron detectors are also used in devices that determine the proportions of water, oil, and gas in wells drilled for energy production. Other important uses of 3He include lasers, gyroscopes used for missile stability and guidance, and cryogenic research (ultra-low temperature, less than 1 K). The global supply of 3He available for research and practical applications has become severely limited in recent years, such that prices have increased substantially and some uses have been curtailed,. A major source of 3He is from nuclear weapons containing 3H, recovered when the warheads are reconditioned or dismantled. 3He accumulates in such devices as a radiogenic product of 3H decay. The annual supply of new 3He has decreased with reductions in nuclear arsenals.
• 3He is used as an inhalant to improve magnetic resonance imaging (MRI) of the lungs.

Isotop helium lainnya

⁴He, ⁵He, ⁶He, ⁷He, ⁸He, ⁹He, ¹⁰He

Pelajari

Kimia inti Simulasi peluruhan ³He Bagan nuklida