Boss Energy (ASX:BOE) said the updated mineral resource estimate (MRE) for its Honeymoon Uranium Operation in South Australia stands at 21.4 million tonnes at 440 parts per million uranium oxide for 20.8 million pounds of uranium oxide metal, according to a Thursday Australian bourse filing.

The updated mineral resource estimate represents a 42% decrease in metal and a 33% reduction in average grade compared with the 2019 MRE at a comparable cut-off grade, the filing added.

The company said the updated MRE comprises 66% indicated and 34% inferred resources at a 100 parts per million cut-off, depleted as of June 30.

The new feasibility study forecasts life-of-mine production of about 13.8 million pounds of uranium oxide drummed over a nine-year operating period, reaching 1.9 million pounds per year from fiscal 2030 to fiscal 2033, with forecast life-of-mine production 26% lower than the 2021 enhanced feasibility study, the filing added.

The company said average C1 costs are AU$50 per pound and all-in sustaining costs are AU$79 per pound, reflecting a circa 28% increase in pregnant leach solution grade and a circa 50% reduction in wellfield infrastructure compared with the historical design.

The company's shares plunged 17% in recent Thursday trade.