Appl Radiat Isot. 2016 Dec 21. pii: S0969-8043(16)30455-9. doi: 10.1016/j.apradiso.2016.12.031. [Epub ahead of print]For the ultimate sensitivity in trace radiochemical analysis, the radiation detector must have high efficiency and low background. A low-background gamma-ray spectrometer in regular use at NIST for over twenty years is being supplemented by a new system, improved in several ways. The new detector is much larger, a shield of iron reduces cosmic neutron background compared with lead, large plastic scintillators reduce the muon continuum background, and a digital data acquisition system gives new opportunities for optimization.Published by Elsevier Ltd.