Patent Number: 
Section: claims

1. A gamma radiation source comprising: 75Selenium or a precursor thereof, wherein the 75Selenium is provided in the form of one or more thermally stable compounds or mixtures, and with one or more nonmetals the neutron irradiation of which does not produce products capable of sustained emission of radiation which would unacceptably interfere with the gamma radiation of 75Selenium. 2. A gamma radiation source as defined in claim 1, wherein the one or more nonmetals comprise a natural isotopic composition, an enriched isotopic composition, or a depleted isotopic composition. 3. A gamma radiation source comprising: 75Selenium or a precursor thereof, wherein the 75Selenium is provided in the form of one or more thermally stable compounds, or mixtures with one or more nonmetals the neutron irradiation of which does not produce products capable of sustained emission of radiation which would unacceptably interfere with the gamma radiation of 75Selenium, wherein the one or more nonmetals may comprise a natural isotopic composition, an enriched isotopic composition, or a depleted isotopic composition; wherein the gamma radiation peaks of the composition may be adjusted in relative frequency. 4. A gamma radiation source comprising: 75Selenium or a precursor thereof, wherein the 75Selenium is provided in the form of one or more thermally stable compounds, or mixtures, and with one or more nonmetals the neutron irradiation of which does not produce products capable of sustained emission of radiation which would unacceptably interfere with the gamma radiation of 75Selenium, wherein said one or more nonmetals comprises Germanium or Silicon. 5. A gamma radiation source comprising: 75Selenium or a precursor thereof, wherein the 75Selenium is provided in the form of one or more thermally stable compounds, or mixtures with one or more nonmetals the neutron irradiation of which does not produce products capable of sustained emission of radiation which would unacceptably interfere with the gamma radiation of 75Selenium, wherein the one or more nonmetals may comprise a natural isotopic composition, an enriched isotopic composition, or a depleted isotopic composition, wherein said one or more nonmetals comprises Ge or Si, wherein the gamma radiation peaks of the composition may be adjusted in relative frequency.