Seriously? I don't know what his "light water cell" is but I doubt that NASA replicated any of Mills' claims.
You said that to make me look it up for you, didn't you? Well, I did:
In 1996, NASA released a report describing experiments using a BLP electrolytic cell. Although not recreating the large heat gains reported for the cell by BLP, unexplained power gains ranging from 1.06 to 1.68 of the input power were reported, which, whilst "...admit[ing] the existence of an unusual source of heat with the cell...falls far short of being compelling". The authors went on to propose the recombination of hydrogen and oxygen as a possible explanation of the anomalous results.
Around 2002, the NASA Institute for Advanced Concepts (NIAC) granted a Phase I grant to Anthony Marchese, a mechanical engineer at Rowan University, to study a possible rocket propulsion that would use hydrinos.