average at best , page-34

I found a synopsis of the pdf elsewhere and have copied it for here. Thanks caterpilla from TS.

Resource (JORC) Estimates for In Situ Leach

Uranium Exploration Expansion
With recent emphasis being placed on Uranium (U) as a means of sustainable or energy least impacting on the planet, there has also been a sudden influx of Junior Explorers, some focused on U only. (I have been trying to keep an eye on them !)

With these sunrise exploration programs has also come a certain amount of confusion, as to how one can asses the results of their work. This has probably been the result of these companies mostly searching for palaeochannels/valleys forming roll front U deposits, which can be extremely economical to mine. The mining process being in situ leaching (ISL).

ISL mining technology for uranium was developed independently in both the USSR and USA in the mid 1970s, so we are a bit slow in Australia. In Australia, ISL mining experience is limited to Beverley mine (South Australia), which commenced production in 2001. A second ISL mine is being developed at Honeymoon, also in South Australia. In addition, a couple of other under rated explorers are also establishing Pilot Plants. In all my living days, associated with mining, I have never seen a Pilot Plant fail expectations, especially when established by competent people.

But why the problem with ISU JORC interpretation as compared to other conventional base metal deposits? This can be a real nightmare if companies are not all reporting their findings within the same parameters. Why are palaeochannel roll front deposits difficult to asses?

Eocene Strata
These deposits/accumulations if you like, occur in particular sequence and or classification of strata or stratigraphy. The geological history can probably be best described by saying that the U occurs within the Tertiary Sediments, of which palaeochannels are generally found in the sub-division of this age group called the Eocene strata, of which there can also be an upper & lower Eocene system. But to generalize and to keep things simple, we will adhere to Eocene, a period where fossils can be found that identify the age, within the mainly esturian sands/gravels and clays. Some fossils reveal Mollusca showing the dawn of recent species (shells molluscs) and where an existing order of Mammals appear. So as you can see, it is somewhat of a messy business poking around in these areas and endeavoring to determine a JORC compliant resource.

In addition, these systems are generally below the water table, and make for difficult recovery of sample suitable for assessing the exact nature of the elements contained within.

JORC Standardisation
During 2005 The Uranium Industry Framework (UIF) was established by the Minister for Industry, Tourism and Resources.The Steering Group comprised senior representatives of the uranium industry; the Commonwealth, South Australian and Northern Territory governments; and the Northern Land Council.

The resulting technical paper called for relevant supporting material to be prepared to provide information to ensure that the JORC Code is properly understood and applied, and include case studies related to uranium mining, particularly in relation to in situ leach mining (ISL).

The Implementation Group allocated responsibility for coordination of the preparation of this uranium reserves and resources paper to Geoscience Australia, in consultation with the Joint Ore Reserves Committee (JORC). The JORC Code is principles based, rather than a prescriptive Code. It sets out minimum standards, recommendations and guidelines on the classification and public reporting, whether by ASX Announcements, Quarterly or Annual reporting. The paper did not constitute a formal addition to the JORC Code, it presents suggestions on practices that are consistent with this Code.

Reporting Uranium Properties
Here are a few issues that are particularly important for uranium which specifically need to be taken into account.

1.Radiometric probes or hand held devices are commonly used in exploration and evaluation of mineralization. These need to be appropriately calibrated
and adequate correction factors applied.

2.Uranium can be out of equilibrium with its daughter products, and the extent of disequilibrium needs to be quantified in estimating uranium grades by gamma-based methods. (Definition of disequilibrium: it occurs when one or more decay products are dispersed as a result of differences in solubility between uranium and its daughters, and/or escape of radon gas.)

3.Check assays (repeats) of representative samples are required.

From the above came the reliability of the probe measurements, the number and distribution of measurements, and the extent of check assaying that will constrain the category of uranium mineral resources that can be reported. The units used to report grades and tonnages should all be unambiguous.

Some Probe Techniques for ISL
Radiometric data for evaluation of in situ leach uranium deposits are acquired by downhole logging. Two of these are:

1.Gamma ray logging which measures gamma radiation from radioactive daughter isotopes produced from isotopic decay of uranium-238 (U238). Consequently, the uranium determination can be inaccurate due to the natural disequilibrium between uranium and its daughter isotopes.

2.Prompt fission neutron (PFN) logging which provides a direct measure of uranium, these measurements are not affected by natural disequilibrium.

Drilling Logging & Analysis
Down hole logging is used mostly in conjunction with open hole rotary mud drilling which is a relatively rapid, low cost drilling method. It may be difficult to obtain representative samples (core, rock chip) of unconsolidated sands and gravels which host the deposits by using conventional drilling methods such as reverse circulation. Rotary mud drilling is often used because it causes minimal disturbance of the soft unconsolidated sands, and mud coating of the walls keeps the hole open for sufficient time to complete logging with a downhole probe.

However, with rotary mud drilling, there is severe lag of sample material and mixing across sample intervals. Consequently, chemical analyses of sample cuttings are usually not undertaken for grade determination because they are not normally representative of specific sample intervals.

The continuous nature of the radiometric data from down hole probes provides a complete measure of uranium grades in the host sands whereas core recovery from conventional drilling would be poor or non-existent for these holes.

Economic U Values
How many times do we see Companies announcing through the ASX these huge hits of U (U3O8) and how many metres they have in the intersection? Too many to name. Yes, we have a fair idea why it is done. It causes new investors/traders to fight over their securities like seagulls fighting over hot potato chips. I call them the OHOHW (One Hit One Hole Wonders).

But remember, there are two types of U deposits in Australia.

1. Hard Rock
and
2. In Situ

Hard Rock
We probably all know what is classed as hard rock mining. Drill, blast and removal.

However, most hard rock (base metal) mines require underground workings which are expensive, unless they are open pit. Few hard rock base metal mines become open pit.

One such U mine is Roxby Downs. Hard Rock & Underground. That may change with the BHP expansion program. It may become the largest Open Pit on Planet Earth.

But the point is, that there is no hard rock underground mine in Australia that is highly economical chasing U at only 200ppm to 300ppm.

For Roxby Downs to exist, it relies on the other elements of the poly metallic deposit. Take away the Gold (Au) & Copper (Cu) then it would become uneconomical to mine for U or anything else for that matter. The mine would not be feasible. U is only in the order of a few hundred ppm (Parts Per Million) (.01% – 0.03%) 100ppm to 300ppm.

So next time you see a great OHOHW intersection announcement on the ASX, weigh up as to whether it is a poly metallic deposit, or a one off U intersection. Hard rock values of 100ppm to 400ppm at depth are just not worth chasing. However, they may well be worth further exploration and drilling.

In Situ Leaching (ISL)
This process, developed independently in the US and the former Soviet Union (FSU) is the most cost effective means of extracting U from palaeochannel roll front formations.

Very few, only a limited number of Junior Explorers have this intimate knowledge, of finding palaeochannel formations, let alone extracting the U. These are mostly to be found in South Australia where Legislation encourages exploration, and then simple processes of E.I.S (Environmental Impact Statement) coupled with E.P.A. (Environmental Protection Authority) approval to get the projects up and running to an accepted level. S.A leads Australia, as opposed to the process required in W.A., since the recent change of Govt.

So when evaluating the feasibility, there is increased recognition that ISL field leach trials provide more reliable, large scale tests of recovery. In addition, these trials also provide important data on the hydrology and permeability of the sands which host the mineralisation. These are important parameters for mineral resource estimates.

As opposed to Hard Rock Mining, ISL Reserves can operate Economically as low as 300ppm to 500ppm (0.03% U3O8 to 0.05% U3O8). When you begin to see figures around 500ppm to 1000ppm, (0.05% U3O8 to 0.1% U3O8) you are starting to look down the barrel of a potentially high grade In Situ Prospect.

The ultimate test, a pilot scheme. This process is far beyond and after the OHOHW drilling announcement of a new U resource that may have been announced on the ASX.

So next time you see new U Province, or a OHOHW type of Intersection, consider the path the explorer then has to go down before one can really consider their announcement valid.

Some Junior Explorers are already well down the track, having drilled many hundreds of holes, or near to it, considering the construction of a Pilot Operation, have great market sentiment to raise capital for these operations, and have the Technical Know How to meet the Desired Objective, on time and within budget.