Tritium measurements with a new liquid scintillation counter

Abstract

Abstract A new concept in liquid scintillation counting has been employed in developing an instrument for the purpose of quantitatively measuring low specific activity tritium samples. The instrument design differs from present commercial instrumentation in that it utilizes electronics that measure fast-pulse time intervals rather than performing pulse height analysis. The liquid counter was built to accomodate samples as large as 100 ml of solution. The solutions can be counted as a combination of water and scintillator or as pure benzene synthesized from water. As much as 20 g of water can be counted directly as a solubilized cocktail or an equivalent of 66 g of water converted to benzene. Direct counting of aqueous cocktails can be accomplished to sensitivity levels below 10 T.U. Tritiated benzene samples of 25 ml volume have been counted at 53% counting efficiency with background count rates contributing less than 1.75 c/m. This new instrument utilizes massive graded shielding and an electronic guard to minimize external radiation for low background counting.