H

H

atomic symbol for hydrogen

half-life (of a radionuclide)

median life of an atom of a radionuclide, usually denoted by T_1/2, or the time required for, on average, half of any given amount of the radionuclide to decay

He

atomic symbol for helium

health physics

study of the effects of ionizing radiation on people and the environment and of methods of protection against its harmful effects; the science of radiation protection

heterogeneity

nonuniformity in the composition of material

Note: The existence of heterogeneity implies that samples of the material may differ in composition from each other and from the original lot of material as a whole.

Hf

atomic symbol for hafnium

Hg

atomic symbol for mercury

high-purity germanium (HPGe) detector

gamma-ray detector whose principal component is a cryogenic crystal of high-purity germanium

Ho

atomic symbol for holmium

hold-back carrier

carrier used to prevent a particular species from following other species in a chemical or physical operation [IUPAC]

holding time

specified limit on the time allowed between two steps in sample processing, such as the time between the receipt of the sample at the laboratory and the completion of a particular analysis

homogeneity

degree of uniformity in the composition of material; lack of heterogeneity

Hs

atomic symbol for hassium

HTO

commonly used molecular symbol for tritiated water, in which one atom of ¹H has been replaced by an atom of ³H (tritium)

Note: Tritiated water may also occur as T₂O, but this molecular form is relatively significant only at very high tritium concentrations.

hypothesis test

statistical test for choosing between two hypotheses, one of which (the null hypothesis, H₀) is presumed to be true in the absence of evidence to the contrary and the other of which (the alternative hypothesis, H₁ or H_A) is accepted only if the data provide strong evidence for it