Process economics

The plant design is subject to capital cost estimating procedures.For a feasibility study, the development of the costs will include the following components:

Civil

detailed estimates of quantities are combined with carefully developed unit rates for the various construction tasks, e.g. clearing and grubbing, excavation, backfill, concrete, etc.At the feasibility study level of detail, it is necessary that sources for backfill material be identified and unit costs for concrete be developed or quoted by reputable contractors.

Building and structural steel

costs are based on detailed steel quantity take-offs combined with quoted unit rates from supply and install contractors.

Equipment supply costs

are based on firm quotations from suppliers received in response to detailed technical specifications coupled with proposed commercial terms. Delivery costs must be included in the quotation or developed in detail by the cost engineers for remote projects. It is expected that the quotations used in the estimate will be suitable for the purchase of the required equipment.

Used process equipment is sometimes invoked as a means of reducing capital costs.

Experience shows that the direct cost savings are often eradicated by refurbishment costs and startup delays. At the feasibility stage, the inclusion of purchased used equipment in the cost estimates must be supported by a letter of intent and a favourable mechanical inspection report. Used equipment already in the possession of the project owner must be carefully examined for the state of repair and the suitability.

Equipment installation costs

are developed from a combination of installation manhour requirements and the appropriate project crew rate. The crew rate is developed by the estimating team and includes the direct labour cost for a construction crew, the cost of overtime, direct supervision, travel time, subsistence allowance, and contractors profit.

Many will be surprised that the crew rate on most North American projects presently exceeds

$50/manhour. Equally surprising is the time that contractors require for what appears to be a simple task. Installation of a small slurry pump, say one with a 50 mm suction line and weighing about 200 kg, requires one manweek of effort. It is tempting to look at the equipment and imagine installing it oneself in a day but the historical record must be relied upon.

Instrumentation

costs can be significant in modern plants ranging as high as $2 000 000 in a large and complex plant. However, in a plant producing 2000 t/a of U valued at about $44 million/a, an extra 1% recovery is worth $440 000 and could result from improved instrumentation. The costs for instrumentation must be estimated from detailed design documents.

Piping

for a detailed feasibility study, the piping specifications must be firm and the routing of all major lines identified and costed. This is particularly true for expensive materials of construction such as titanium and high alloy materials.

Electrical

the source of power, cost of transmission lines, switchgear, and primary transformers must all be identified and costed in detail.Costs for secondary transformers, motor control centres (MCC) will also be detailed in the feasibility study. Costs for final distribution will be based on average cable lengths and unit costs.

Indirect construction costs

includes the costs for working under difficult climatic conditions, establishing and operating construction management offices, crane rental, bonds, permits, construction camp, fly-in/out operation and other similar costs.For the feasibility study, these costs must be estimated in detail.

Engineering, procurement and construction management

these costs are estimated in detail at the feasibility stage. A significant proportion of the engineering costs have, of course, already been expended to arrive at the feasibility stage.

Contingency

money is set aside to cover the cost of items in the original scope, but either missed, or not estimated in detail, or unknown at the time of the estimate. At the feasibility stage this is often included as an allowance equal to 10% of the estimated direct cost of the project. Contingency is not intended to cover scope changes.

The capital cost estimate for the hypothetical plant is summarized below:

Process Plant Area_________US$000 US$000 Site preparation

roads, etc. 2,000 Building

sorting plant process plant solvant extraction

TOTAL

1,000 7,000 1,000

9,000 9,000

104

Equipment sorting grinding leaching CCD SX

Gypsum precip Uranium precip product drying tailing/water treatment reagents

laboratory

services and instruments

Total direct cost — $ 1000s

5,000 4,300 2,500 5,200 2,900 1,100 900 1,400 1,000 4,000

700 2,200

31,200 31,200 42,200

Note that piping, electrical and indirect construction costs are included in the relevant process sections in the capital cost table. Other indirect costs are treated in subsequent sections.

P l a n t o p e r a t i n g c o s t

Process operating costs must also be revised:

Operating labour costs

a revised manning document is prepared for the process aspects of the project. The document includes all supervision, operating and maintenance personnel and is based on required staffing levels for other, similar plants. Labour rates must be confirmed based on local union contracts, published salary surveys, and other sources.

Process supply costs

the requirement for reagents and other supplies must be reviewed based on the latest test data and relevant data from other, similar operations. Delivered costs for reagents are obtained from suppliers as firm quotations. In the case of remote projects, costs might be obtained for delivery to a marshalling point. The engineering company would then develop costs to transport to the project site.

Power costs

process power consumption is obtained by a detailed analysis of the electrical loads. The unit cost of power is usually obtained as a detailed quotation from a supply utility. At remote sites, power will be generated in hydro-electric plant or diesel-electric power plant. In either event costs must be developed in detail.

Other operating cost components must be developed in detail for the feasibility study. In all cost areas, the unit costs must be obtained as written quotations from reputable suppliers and in response to written enquiries.

Using the procedures outlined above, the following data were obtained for the hypothetical processing plant (including the radiometric sorter).

PROCESS OPERATING COSTS — $1000/a

Total operating costs $1000s/a Unit operating cost ($/LB U3O8)