GR Engineering Services has reviewed the latest technical optimisation studies related to the restart of the Honeymoon uranium mine, in South Australia, and come up with capital expenditure savings of $6.3 million for owner Boss Resources.

Following the release of the feasibility study in January 2020, Boss embarked on technical optimisation studies which included completion of an identified ion exchange (IX) process detail design and testing, undertaken with the Australian Nuclear Science and Technology Organisation (ANSTO).

The January feasibility study highlighted a capital expenditure of $63.2 million (excluding offsite power provider upgrades) to build the two-stage mine. Stage 1 consisted of refurbishing the existing solvent extraction plant with process improvement to a capacity of 880,000 Ib/y of U308 equivalent, while Stage 2 involved adding an IX circuit to achieve annual production of 2 Mlb/y. This also estimated an average all-in cost of $32.3/lb U308 over the life of mine.

The IX process optimisation program with ANSTO aimed to remove the requirement for solution heating in the elution of uranium from the IX resin. Power input to the elution process necessitated upgrades to the transmission line to service Honeymoon with grid power from Broken Hill, 80 km southeast of the mine.

Boss devised a series of tests in consultation with ANSTO to study the effect of ambient temperature on both the conversion and elution performance, with the conversion work indicating an ambient temperature process could achieve the required conversion performance within the timeframe in the process design.

Furthermore, a 45% reduction in reagent concentration in the conversion process had a negligible effect on conversion performance and offered significant reagent savings, Boss noted.

Test work on the elution process was also successful, the company said. “While there is a small difference in the eluant requirement to achieve complete elution of the resin, there is sufficient capacity in the elution circuit as designed to achieve this without impacting the downstream processes, while facilitating significant energy savings,” it explained.

The remainder of the program aimed to provide additional information to allow detailed equipment design for IX adsorption and elution processes. As a result of this work, Boss made additional changes to the resin sulphation and regeneration processes, which could represent additional cost savings.

Boss commissioned GR Engineering to evaluate the cost implications of the above work on the feasibility study results, initially on a +/- 25% basis, with initial results confirming a capital expenditure reduction of $6.3 million owing to the reduction in heating and insulation requirements for the elution circuit and reagent make up systems, and the reduced transmission line upgrade costs.

Additionally, the engineering company identified the reduction in electricity costs alone represented an operating cost saving of $2.4 million/y, equating to $1.22/lb U308 equivalent.

GR Engineering is now undertaking an evaluation of the operating cost implications of these changes in Stage 2 operations over the life of the overall operation considered in the feasibility study.

“Boss designed the feasibility study to fast-track production from Honeymoon’s existing solvent extraction plant within a 12-month period, following a decision to mine, to capitalise on any improved market fundamentals,” the company said.

It plans to increase production to 2 Mlb/y U308 equivalent through the addition of the IX plant, which will take around 20 months to design, construct and commission.

Boss Resources Managing Director and CEO, Duncan Craib, said: “Boss continues to work on opportunities to optimise Honeymoon as a first-mover uranium restart operation – this outstanding IX test work result is one example.

“We will continue working towards net present value accretive technical advancements and revising estimates contained within the January 2020 feasibility study, strengthening Honeymoon’s potential to be one of the lowest cost uranium producers globally.”

Following these initial results, Boss plans to incorporate these optimisations into a revised feasibility study level estimate for the Honeymoon restart which will also incorporate other initiatives including the conversion of the current solvent extraction infrastructure to a NIMCIX IX system, Boss said.

In parallel, Boss’s exploration team is completing a comprehensive desktop review of the extensive historical exploration database information to define new uranium exploration targets.

“With financial support from the South Australian government to utilise innovative uranium geophysical exploration techniques, exploration is focusing on expansions to known uranium discoveries to increase Honeymoon’s production profile distal to existing JORC mineral resources (total 71.6 Mlb U308),” the company said.

It is envisaged that these new mineralised target areas will form the basis of a study to assess and define Stage 3 production ramp up to produce more than 3 Mlb/y U308 equivalent, Boss said.