Abstract. Applying atomic beam laser spectroscopy, hyperfine constants as well as level isotope shifts of the (6s2r~s) 2S1/2 levels (n = 7 -12) and (6s2nd) 2D3/2,5/2 levels (n = 6-10) have been measured in 2°3T1 and 2°5T1. Furthermore, some new hyperfine constants and level isotope shifts of the T1 2p1/2, 3/2-states are presented together with corrected results of earlier experiments. The hyperfine splittings have been compared with the predictions of the semiempirical theory. For the D-states a relatively poor agreement between these theoretical predictions and experimental resuits has been found. Using the experimental level isotope shifts and the 6(r 2) value from muonic X-ray data, results of single-configuration Dirac-Fock calculations have been tested.

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Plutonium-238 oxide ( 238 PuO 2 ) is used in the fabrication of general purpose heat sources (GPHS) or light-weight radioisotope heater units (LWRHUs). The heat sources supply the thermal energy used in radioisotope thermoelectric generators to power spacecraft for deep space missions and to heat critical components in the cold environs of space. Los Alamos National Laboratory has manufactured heat sources for approximately two decades. The aqueous purification of 238 PuO 2 is required, due to rigorous total Pu-content, actinide and non-actinide metal impurity, and neutron emission rate specifications. The 238 PuO 2 aqueous purification process is a new capability at Los Alamos National Laboratory as previously, aqueous purified 238 PuO 2 occurred at other DOE complexes. The Pu-content and actinide and non-actinide metal impurity specifications are met well within specification in the Los Alamos process, though reduction in neutron emission rates have been challenging. High neutron emission rates are typically attributed to fluoride content in the oxide. The alpha decay from 238 Pu results in α,n reactions with light elements such as 17 O, 18 O, and 19 F resulting in high neutron emission rates in the purified 238 PuO 2 . Simple 16 O-exchange takes care of the high NER due to 17 O, and 18 O. A new method to reduce the NER due to 19 F in the purified 238 PuO 2 is presented in this paper. The method involves addition of water to purified 238 PuO 2 , followed by heating to remove the water and liberating fluoride as HF.