The increase to 71.6 million pounds of uranium oxide (within 52 million tonnes grading 620 parts per million uranium oxide), is in the fully permitted mining lease at the idled operation.
The increase followed infill drilling and interpretative work.
De-risking work is continuing.
Boss has a debt finance mandate with private equity firm Tribeca for US$65 million.
Such funding is seen as going towards a re-start of the solvent extraction plant for production of 880,000 lbs per annum U308 equivalent (costing $10 million), with incorporation of an ion exchange plant taking output to 2Mlbs per annum U308 equivalent at an added cost of $58 million - and a two year timeframe.
The forerunner to the planned Boss project was initially developed and briefly operated earlier this decade prior to be shut when the uranium price crashed post-Fukushima.
Boss started the year with A$12.7 million cash.
Shares in Boss were up 5% to 5.9c in morning trade, capitalising the company at $93.5 million.
The stock was at levels around 4c 12 months ago and 8c last August.