This is by no means a wildly original premise (among other things, it's the premise for "Memory Of Water", reviewed for this site back in 2012 - although, to be fair, Radiance predates "Memory of Water" by a year or so) but it's certainly a serviceable one for a few family secrets, a lot of good jokes and some of those long-awaited-things, good roles for actresses (in this case, "Radiance" was written on request for two of its three original lead actresses).
In this current production, we get large chunks of the humour (particularly as handled by Miranda Tapsell, who gets the lionshare of the best jokes) and some great work with the family secrets as Shari Sebbens and Leah Purcell get to unburden themselves in act two. The decision to play it straight through without an interval does lead to a slightly odd set design (by Dale Ferguson) meaning act one is played fairly remotely from the audience - the actors only get to get up-close-and-personal with the audience in Act Two. A combination of writing and actress also means that Sebbens' opening monologue doesn't quite have the high-pitched anger that seems to be seething through the writing, though Sebbens clearly brings it home in her interactions with the other two actresses and particularly her monologue of resentment in Act Two.
Purcell has dual duties as both actress and director - while her character isn't quite where her range normally is (I've mostly enjoyed Purcell more when she plays earthy practical characters), she does have a nicely toned hauter to her that is let go to remarkable effect as events roll on. Most importantly, all three actresses feel like they belong together, that they have shared history and are very lived-in people.
If I have slight reservations, it's mostly to do with design (you lose a lot when you don't let your actors roam free on the belvoir stage) and with Nowra's script, which is more of the "good vehicle" rather than consistently great play - some of the revelations feel a bit forced and he does go to the melodrama side fairly often. But this is a solid enjoyable production and a good launch to the year.