In anticipation of results from current and future double-beta decay studies, we report a measurement resulting in a 82 Se double-beta decay Q-value of 2997.9(3) keV, an order of magnitude more precise than the currently accepted value. We also present preliminary results of a calculation of the 82 Se neutrinoless double-beta decay nuclear matrix element that corrects in part for the small size of the shell model single-particle space. The results of this work are important for designing next generation double-beta decay experiments and for the theoretical interpretations of their observations. The results of recent neutrino oscillation experiments indicate that the mass of the neutrino is non-zero [1][2][3]. The mass hierarchy and the absolute mass scale of the neutrino, however, are unknown. Furthermore, the nature of the neutrino is also unknown; is it a Dirac or Majorana particle, i.e. is the neutrino its own antiparticle? The only known practical method for determining the nature of the neutrino is through neutrinoless doublebeta decay (0νββ decay) measurements [4]. Interest in double-beta decay (ββ decay) has been increasing since the laboratory verification of the weak, but allowed, twoneutrino double-beta decay (2νββ decay) of [6,7]. With the exception of the controversial claim in Ref. [8], 0νββ decay has yet to be observed. If experiments succeed in observing 0νββ decay, we would have evidence that the neutrino is a Majorana particle and that conservation of total lepton number is violated -a situation forbidden by the standard model of particle physics.An extensive campaign is currently underway to develop next-generation experiments to detect 0νββ decay in a number of candidate isotopes (see Ref.[9] for a current review of planned experiments). One such experiment, SuperNEMO, is expected to provide an increase in sensitivity of three orders of magnitude over its predecessor, NEMO-III, and is projected to reach a half-life sensitivity at the 90% confidence level of 1-2 x 10 26 years by observing 100-200 kg of 82 Se for five years [9,10]. The defining observable of 0νββ decay is a single peak in the electron sum-energy spectrum at the ββ decay Q-value, Q ββ . Hence, it is crucial to have an accurate determination of Q ββ . The Q-value is also a key parameter required to determine the phase space factor (PSF) of the decay. The effective Majorana neutrino mass, together with the corresponding PSF and nuclear matrix element (NME) for a 0νββ decay candidate provide the necessary information to determine the 0νββ decay halflife, which is given by:where M is the relevant NME, m ββ is the effective Majorana mass of the neutrino, m e is the mass of the electron, and G 0 ν is the PSF for the 0νββ decay, which is a function of Q ββ 5 and the nuclear charge, Z . Thus, to obtain an accurate estimation of the half-life sensitivity needed to detect a given m ββ , or conversely, to determine m ββ if the half-life is measured, the NME and especially the Q-value need to be known to high precision.Of all the 0νββ decay...