Will $^{37}$Ar emissions from light water power reactors become an obstacle to its use for nuclear explosion monitoring?

Abstract

37 Ar is a promising candidate for complementing radioxenon isotopes as indicators of underground nuclear explosions. This study evaluates its potential anthropogenic background caused by emissions from commercial pressurised water reactors. Various 37 Ar production pathways, which result from activation of 36 Ar and of 40 Ca, respectively, are identified and their emissions quantified. In-core processes include (1) the restart of operation and degassing of the primary cooling water after maintenance and refueling shutdown, (2) the replacement of primary coolant water for limiting its tritium concentrations, and (3) the leakage of 37 Ar produced from calcium impurities in UO 2 after fuel rod failures. Activation of air and of calcium in concrete within the biological shield are major out-of-core production pathways. Whereas emissions from in-core processes are transient, a rather constant 37 Ar source term results from its out-of-core production.