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United States uranium resources the 1975–2000 outlook
United States uranium resources The 1975 -2000
outlook
Douglas G. Brookins The
status
the
USA
can only broad
of uranium
for the
due
interplay
of
involved.
Minimum
light
oxide
water
within
to
the
rather
a
complex
many
factors
estimates
requirements
nuclear
for
to fuel
reactors
(LWRs)
alone range from 2 x IO” to 2.25 tonnes
These
U3 03.
deemed
reasonable
unlikelihood
for
1975-2000
be estimated
limits
uranium
resources
period
x 1 O6
limits due
are
to
the
of a firm commitment
to
the use of fast breeder reactors (FBRs) by the government; dates range from but, even impact
tentative 1988
presuming
on uranium
felt until after
2000.
A wider may
eventual
uranium
needs
originally
reactors,
planned
FBRs; hence
uranium
the next century. an
accelerated
development federal and
the
close
however,
to
were use
from LWRs to
their increased
the
use of
lighten
only for interim
during the change-over not affect
the
needs will not be
reactors
These
or so
the former,
converter 2000.
decision
to 2000
use will
demand
until
Present plans call for exploration
and
programme involving state agencies with
industry and other sources. Department of Geology, University of New Mexico, Albuquerque, New Mexico, USA
142
The necessity for expeditiously developing nuclear resources in view of the depletion of combustible fossil fuels was pointed out in December 1973 by Dr Dixy Lee Ray, then director of the USAEC, in a report entitled ‘The Nation’s Energy Future’. While top priority has been given to coal as the short-term substitute for petroleum and its derivatives the point is well made that nuclear energy will play a dominant role in the immediate future. Indeed, the US Geological Survey has issued a public information circular indicating that some 60% of the nation’s electrical energy needs will be met by nuclear energy by the year 2000. These facts, coupled with the present status of reactors, emphasise the need for accurate knowledge of nuclear fuel resources and ways of expediting new discoveries of nuclear fuels. This report deals with uranium, and the assumption is made that at present uranium is more critical to the nuclear industry than thorium. Thorium is four times as abundant as uranium but, although it may be used in some reactors, the nuclear plants in operation (about 240), under construction or planned, use uranium. The light water reactor (LWR) uses U-235 enriched fuel and therefore most of our present forecasting is based on LWR usage. The total energy production of these 240 or so plants will be approximately 210 000 MW which is more than the total generating capacity in the USA a decade ago. As more plants are ordered then obviously a greater commitment to uranium will increase. This in turn will prompt expansion in the uranium industry and, in turn, additions to US uranium reserves. The minimum required for the period 1975-2000 for the USA is approximately 2.25 x lo6 tonnes of uranium oxide (U3Os). Further, the U-235 content is only 0.72% of total uranium. It should be pointed out, however, that the converter reactors (of which the HTGRs are the most common) use a uranium-thorium mix which requires roughly 65% of the uranium needed for the LWRs. Further, the decision to use the fast breeder reactors (of which the LMFBRs are the most common) will not be made for at least another 12-13 years or so. Many of the data, including those presented as modified figures, have been taken from US government sources. In order to save RESOURCES
POLICY
September
1976
’ ‘Uranium industry seminar’, US Atomic Energy Commission, GJO-108 (74). II parts, 1974, 266pp ‘Uranium resources 2 Brookins, D.G. 1975-2000: Reserves and exploration potential in the United States’, American Sot Mech Engrs Symposium, 1975. (in press) 3 Brookins, D.G. ‘Uranium and thorium resources’ Part IV of State of New Mexico Governor’s Energy Task Force, Report of the Commission on Nuclear Energy, 1975, pp. IV-1 4 Patterson, J.A. ‘Outlook for uranium’ paper at 17th Minerals Symposium, AIME Meeting, Casper, Wyoming, May, 1974,9pp
reference searching time the reader is referred to the publications USAEC (now USERDA).’
of the
Summary of US uranium requirements for the period 1975-2000 Some of the material discussed here has been presented by the author.*13 The annual U,08 requirements to fuel reactors as of 1 January 1974 and those additionally forecast are shown in Figure 1. The annual requirements will reach about 3 x lo4 tonnes around 1980 (well above the past peak production of 1.79 x IO4tonnes in 1960). In brief, the approximate projected needs for uranium (in tonnes of U30x) for the period 1975 to 2000 assume an enrichment tails assay of 0.2% U308 up to 1981 and 0.3% thereafter. It is further anticipated that plutonium recycle will be 100% by 198 1. The initial enrichment transaction tails assay of 0.2% results from the USERDA eliminating some 8.17 x lo4 tonnes of UF, stockpiled at their enrichment plants. The cumulative requirements for uranium are shown in Figure 2. According to Patterson4 these forecasts are subject to any number of assumptions including (1) time lag for plant construction and operation, (2) growth in electricity demand, (3) tails assay selected at the enrichment plant, 137.17
Figure
1.
Annual
domestic b requirements reference
uranium producers
deliveries and
(modified
from
POLICY
September
1)
RESOURCES
1976
143
the relative costs of feed and separative work, recycle of plutonium generated in the reactors and recovered in the reprocessing step which could reduce uranium needs by approximately 20%, and (f-3)possible introduction of the breeder reactors. The decision to use the breeder reactor on a wide scale will not be made until at least 1988 and possibly not until closer to the year 2000. It is apparent from Figure 3 that even if the decision to use the breeder reactor is made in 1988 the effect on uranium requirements will not be fully felt until after the year 2000. Consequently, one is forced to make projected demands on the basis of the light water reactors until at least the year 2000 and perhaps after that date. There are many uncertainties surrounding the introduction of breeder reactors. Concern with safety aspects over the large amounts of plutonium generated by the breeders has been widely expressed by the various public media; hence my earlier comment about this decision as ‘political’ - at least in part. Of further concern is that the cost of the breeder reactor is increasing at an alarming rate. It has roughly increased by a factor of three and, with additional stringent safety requirements coupled with possible even greater costs, this factor may increase even more. Because of these uncertainties concerning the breeder reactors more attention is now being given to greater utilisation of the converter reactors which, while they breed in part (ie, Th-232 to produce U-233), much of the fuel is still enriched uranium. A typical high temperature gas reactor (HTGR) will use about 65% of the uranium needed to fuel a conventional LWR. The converter reactors were considered to be of relatively short-term usage
1830 -
1525-
Figure 2. requirements
Cumulative for ordered
plants (modified
144
1
uranium-
000
and forecast
from reference
1)
RESOURCES
POLICY
September
1976
Figure
3. Projected
requirements
for
breeder
reactors
reference
1)
annual
1988,
2000
(modified
domestic and no
I
1960
from
I
1990
I
I
2000
2010
Year
until the breeder reactors became widely used; it now appears, however, that the converter reactors may be used on a greater scale than previously anticipated. Figure 4 provides a closer examination of the uranium needs of the USA, with annual delivery commitments (as projected based on orders) and requirements for the period 1974-1985. It is all too obvious that the divergence of the two curves reflects the tremendous requirements relative to the delivery commitments as of 1 January 1974. Further, this particular graph has not changed appreciably even with assumed lower grade assay tails through the year 1974. As of 1 January 1974 utilities had contracted with uranium producers for delivery of some 1.22 x lo5 tonnes U308 over the next 20 years; only in 1974 and this year will deliveries be in excess of commitments. This has primarily resulted from slippage in reactor schedules; at present, deliveries are somewhat ahead of actual needs. However, this is, as shown here, a very short-lived phenomenon and price increases for uranium, now on the upswing, will continue throughout the 1970s and into the 1980s. The USERDA’s early 1974 figures on estimated uranium resources are given in Table 1. However, the cut-off costs are USERDA estimates of forward capital costs. Profit and ‘sunk’ costs such as expenditures for property acquisition, exploration and mining development are not included in determining in which category a reserve would be placed. It should be noted that reserves are ores in specific known deposits and their estimates are based on detailed sample data whereas potential resources are postulated to exist in known favourable geological environments. RESOURCES
POLICY
September
1976
145
D.A. and 5 Brobst, Pratt, W.P. United States Minerals ‘Introduction’, Resources, US Geological Survey Professional Paper 820, 1973, p 1 6 Finch, W.I., Butler, A.P., Armstrong, F.C. and Weissenborn, A.E. ‘Uranium’, US Geol. Surv. Prof. Paper 820, 1973, p. 456
In terms of the minimum anticipated cumulative demand (MACD) for identified and hypothetical resources, Brobst and Pratt5 list, respectively, figures of II (ie domestic resources 2 to 10 times the MACD) and III (ie domestic resources 0.75 to 2 times the MACD). Stated in another way these data infer that our uranium resources should be sufficient to about the year 2000 but that they will diminish after that time unless new deposits are found. It is essential to note that Finch and others6 indicate our known reserves to be between 2.27 x lo5 to 2.72 x lo5 tonnes of readily recoverable U308. Even the addition of perhaps some 1.8 x lo5 tonnes from paramarginal reserves totals only 4.54 x lo5 tonnes; less than one-quarter the projected amount needed by 2000. Consequently, our uranium reserves are not adequate to meet the projected demand. Types of deposits The most abundant uranium deposits are those classified as peneconcordant deposits, those in which the uranium is concentrated, commonly in close association with organic carbonaceous matter, in fluvial, lacustrine, and near-shore marine deposited sandstones interbedded with mudstones. Uraninite (uranium oxide) and coffinite (uranium silicate) are the main ore minerals; they commonly fill voids in the sandstones but occasionally replace older mineral grains. The 50 80/
/
// /’ 40 64-
Figure
4.
commitments (modified
from
Annual and reference
0
delivery
Table 1. US uranium Cut-off cost per pound of Us08
146
1985
Yeor
1)
industry seminar’, Source: ‘Uranium AEC, GJO-108 (74). II parts, 1974
1
I 1980
1975
requirements
US
resources - January
1, 1974
Reasonably assured
(tonnes U308) Estimated additional
Total
fY0
306 249 000
630 405 000
936 654 000
$15 $30
468 000 630 000
900 000 1 530 000
1 368 000 2 160 000
RESOURCES
POLICY
September
1976
average grade of ore is 0.15 to 0.30% U308 with a cut-off of 0~08%~ for $22/kg. The ore is deposited in various geometries with tabular or lensoid masses and crescent-shaped ‘rolls’ being the most common. The deposits are sporadically distributed within the sandstones and commonly quite small although accumulations in excess of 9 x lo6 tonnes of ore are known. Conditions of formation for these deposits are not accurately known although it is speculated that deposition of uranium occurs at redox interfaces in ground water systems or mixed ground water-hydrothermal systems. Uranium is thought to be transported as hexavalent uranyldicarbonate ion which is reduced to tetravalent uranium in uraninite or coffinite concomitant with formation of pyrite and other minerals. The sandstone type of deposits constitute over 95% of the deposits known in the USA and are more or less restricted to certain geographic areas in the San Juan Basin, New Mexico; Colorado-Utah Basins; Wyoming Basins; Texas Coastal Plain. The assumed roll front in sandstone is under- and over-lain by impervious mudstone. The general model for sandstone types of deposits is that the ore-bearing solutions move down gradient and precipitate the ore at the redox interface. Whether or not the deposits are roll shaped or lensoid masses is uncertain as they vary from district to district; what is important is the location of the front for planning exploration projects. Let us also remember that in the exploration programme the drilling is often done through hundreds to thousands of metres of barren rock and that the ore is rather sporadically distributed. To emphasise this point let us consider a case, as in Figure 5, in which a hypothetical drill grid and the outline of a hypothetical redox front and ore zones are shown. The figure has been drawn to show all the drill holes missing the ore zones and also the many holes in both the oxidised as well as in the reduced ground. It is obvious that criteria must be developed to determine whether or not reduced ground is encountered, and this is being done. It is of greater importance to determine whether or not ore-bearing solutions have
Poleo - charnels
Figure hydraulic
5.
Assumed
direction
Pyrite-bearing
of
ground
gradient
RESOURCES
POLICY
September
1976
147
penetrated the rocks. Solutions to these problems will greatly reduce the drilling costs. Other deposits include Precambrian, uranium-bearing quartz conglomerates (important in Canada and South Africa but not in the USA), uranium-bearing vein deposits which occur as fissure and other types of fillings of rocks of virtually all ages, contact metamorphic deposits, and other minor deposits. These are described in greater detail in Finch and others.‘j A greater search for the uranium-bearing quartz conglomerates is warranted based on the reports presented at the conference on ‘Formation of Uranium Deposits’ (International Atomic Energy Agency, Athens, Greece, 6-10 May 1974). A virtually untapped source of uranium is phosphatic rocks enriched with uranium; although the percentage is low (O-007 to 0.07% U,Os) the tonnage is tremendous. Technological problems in removing uranium from these rocks have not been solved, however. The same can be said of marine black shales with low but significant concentrations of uranium. Further environmental restrictions may limit rapid development of these potential resources. Finch and others state: ‘Domestic speculative resources consist of (1) new districts containing types of uranium deposits found elsewhere in the United States, (2) types of deposits known only elsewhere in the world, and (3) new types of deposits’. They list margins and axial parts of sedimentary basins (especially those derived in large part from granite or volcanic rock terrains) as favourable targets. Exploration methods are usually those involving radioactivity measurements (ie conventional Geiger counters and more sophisticated scintillation counters) in conjunction with favourable geological criteria. On a nationwide scale it is apparent that more attention should be given to searching for non-peneconcordant types of deposits as well as for research in uranium recovery from phosphorites and black shales.
Comments on exploration The success of any exploratory programme for uranium depends on many factors, not the least of which are the drilling programmes and related additions to the national reserves. The period from 1948 to 197 1-1972 was marked by drilling and additions of reserves on the usual supply and demand formula in turn dictated by purchasing policies and/or constraints on the nuclear industry. The decline in drilling and reserve additions in the late 1950s was determined by factors other than those primarily related to the nuclear industry, and they are, in retrospect, exactly what one would expect. Similarly, the increase in drilling and reserve additions in the late 1960s in response to a growing nuclear industry is also predictable. However, for the period 1966-1969 the ratio of reserve addition/drilling (in millions of metres) was not as high as in the 195Os, which in turn is a reflection of discovery of many of the major orebodies during the 1950s plus increased drilling costs and shortages of drilling equipment and related factors in the 1966-1969 period, as shown in Figure 6. The ‘lag’ of approximately ten years (ie 1956-1966) fairly well summarises much of what we are today concerned with, ie drilling and reserve addition aspects of the nuclear picture were not recognised in view of future non-petroleum and coal energy needs. 148
RESOURCES
POLICY.September
1976
IO
3
b
-c "0 z
n
/I
m 9
,hanned z 0” 2
6_
drhng
=E
E
s E ?
co “0 G
4-
5 v)
Figure additions
6.
Drilling
(modified
and
I
reserve
from reference
I)
0
1966
g
Reserve
2-
1970
- 60’5 _/--
_c--
-40; -20 1975
i$ 0”
The second drop in drilling-reserve additions occurred in the period 1970-72 and, fortunately, has been of relatively short duration. Uncertainties in the com.mitment to the nuclear energy picture coupled with environmental concern and other factors resulted in short-term cessation of purchasing policy. Not until the very early 1970s did the federal government fully commit itself to a viable nuclear programme. As a result, the estimated drilling footages for 1974 and 1975 are given1 as 8.8 and 10.4 x lo6 metres, respectively approximately double the footage drilled in 1973. Yet one cannot and must not assume that this very rapid increase in drilling will go hand in hand with an equivalence in the form of additions to our reserves due to the reality that new, large deposits are not necessarily unlikely to be found but will certainly be more difficult to find. This was the case for the boom years of the 1950s relative to a lesser boom in the late 1960s. Further, there is a finite limit to our drilling capacity. We do not have enough drilling equipment to expedite the uranium exploration programme unless extensive cuts into the equally viable petroleum and coal programmes are made. This, of course, is unlikely and unrealistic. Thought should be given, however, to assigning higher proprity to domestic drilling programmes for all energy-related programmes than to overseas ventures if Project Independence is to work fully.
Discussions and conclusions We are aware of the favourability of certain areas over others for Roughly 95% of our deposits occur in uranium exploration. sedimentary rocks of Cenozoic and Mesozoic age; notable among these are the deposits of the Grants Mineral Belt and other areas in the San Juan Basin of New Mexico, the Wind River, Powder River, and Shirley Basins of Wyoming, the Paradox Basin of Colorado and Utah, and the Texas Coastal Plain. yet these combined districts in terms of area are small compared to the estimated 6.73 x lo6 km* of sedimentary basins in the USA. That over 90% of our drilling occurs in the known areas merely reflects that it is from these areas that we in all probability will meet our short-term needs for uranium. In order to investigate and evaluate the remaining sedimentary basins non-drilling (supplemented by spot drilling) exploratory programmes RESOURCES
POLICY
September
1976
149
7 ‘Uranium GJO-108
150
industry seminar’, USAEC, (74). II parts, 1974, Figure 3
are being conducted by the USERDA and the USGS. These studies, most of which are just being initiated or else have not been fully developed, should indicate more favourable targets for future exploration. One has only to glance at the NURE (National Uranium Resource Evaluation) resource regions map of the contiguous USA’ to see the discrepancies. The bulk of exploration is confined to resource regions in the San Juan Basin, Wyoming, and coastal Texas. Yet, based on geological inference, one could argue for pilot exploratory programmes in many of the other resource regions. Number 13, which encompasses Kansas and most of Nebraska, Iowa, Missouri, Oklahoma, Texas, and vast amounts of Arkansas, Colorado, New Mexico and even part of Wyoming is well suited for the hydrogeochemical-soil sampling projects contemplated by ERDA and it is noteworthy that some uranium has been found in this region (ie west Texas). Similarly, one could argue that Nevada, in resource region 5, demands attention due to the abundance of favourable source (ie acidic, volcanic) rocks known to occur in the area; again, spotty uranium occurrences are known. Geological criteria have not yet been developed to comment on the favourability of regions east of the Mississippi River although it is known that vast amounts of uranium, although at low grades (ie Chatanooga shale), occur in these regions. It is unrealistic to think that the major quantity of uranium has been concentrated in just the areas now being actively mined; yet, at the same time, it is also unrealistic to think that any simple exploratory programme is going to reap ‘immediate’ results from the virtually untapped non-producing areas. It is now appropriate to address the ‘whys and hows’ of immediate and long-range aspects of the uranium picture. The short-term needs, say to 2000, can probably be met by continued exploration and development of known areas and more likely sub-economic areas, especially if foreign uranium is added to the reserves. However, even if the breeder reactor were in full operation by 2000 or shortly after which is unlikely based on comments made earlier - our known uranium reserves simply do not meet the projected demand. For the post-2000 period the picture is indeed bleak unless new uranium deposits from previously undiscovered areas are found or technology (and other) problems are overcome to assure a continued supply of uranium until some type of stable energy growth is met (ie not necessarily zero energy growth but growth such that supply can cope with demand). To do this the inventory and evaluation programme of the USERDA and other agencies must be complete, preferably by 1990, to allow industry, with the help of the state and other federal government agencies to develop the new sources.
RESOURCES
POLICY
September
1976
outlook
Douglas G. Brookins The
status
the
USA
can only broad
of uranium
for the
due
interplay
of
involved.
Minimum
light
oxide
water
within
to
the
rather
a
complex
many
factors
estimates
requirements
nuclear
for
to fuel
reactors
(LWRs)
alone range from 2 x IO” to 2.25 tonnes
These
U3 03.
deemed
reasonable
unlikelihood
for
1975-2000
be estimated
limits
uranium
resources
period
x 1 O6
limits due
are
to
the
of a firm commitment
to
the use of fast breeder reactors (FBRs) by the government; dates range from but, even impact
tentative 1988
presuming
on uranium
felt until after
2000.
A wider may
eventual
uranium
needs
originally
reactors,
planned
FBRs; hence
uranium
the next century. an
accelerated
development federal and
the
close
however,
to
were use
from LWRs to
their increased
the
use of
lighten
only for interim
during the change-over not affect
the
needs will not be
reactors
These
or so
the former,
converter 2000.
decision
to 2000
use will
demand
until
Present plans call for exploration
and
programme involving state agencies with
industry and other sources. Department of Geology, University of New Mexico, Albuquerque, New Mexico, USA
142
The necessity for expeditiously developing nuclear resources in view of the depletion of combustible fossil fuels was pointed out in December 1973 by Dr Dixy Lee Ray, then director of the USAEC, in a report entitled ‘The Nation’s Energy Future’. While top priority has been given to coal as the short-term substitute for petroleum and its derivatives the point is well made that nuclear energy will play a dominant role in the immediate future. Indeed, the US Geological Survey has issued a public information circular indicating that some 60% of the nation’s electrical energy needs will be met by nuclear energy by the year 2000. These facts, coupled with the present status of reactors, emphasise the need for accurate knowledge of nuclear fuel resources and ways of expediting new discoveries of nuclear fuels. This report deals with uranium, and the assumption is made that at present uranium is more critical to the nuclear industry than thorium. Thorium is four times as abundant as uranium but, although it may be used in some reactors, the nuclear plants in operation (about 240), under construction or planned, use uranium. The light water reactor (LWR) uses U-235 enriched fuel and therefore most of our present forecasting is based on LWR usage. The total energy production of these 240 or so plants will be approximately 210 000 MW which is more than the total generating capacity in the USA a decade ago. As more plants are ordered then obviously a greater commitment to uranium will increase. This in turn will prompt expansion in the uranium industry and, in turn, additions to US uranium reserves. The minimum required for the period 1975-2000 for the USA is approximately 2.25 x lo6 tonnes of uranium oxide (U3Os). Further, the U-235 content is only 0.72% of total uranium. It should be pointed out, however, that the converter reactors (of which the HTGRs are the most common) use a uranium-thorium mix which requires roughly 65% of the uranium needed for the LWRs. Further, the decision to use the fast breeder reactors (of which the LMFBRs are the most common) will not be made for at least another 12-13 years or so. Many of the data, including those presented as modified figures, have been taken from US government sources. In order to save RESOURCES
POLICY
September
1976
’ ‘Uranium industry seminar’, US Atomic Energy Commission, GJO-108 (74). II parts, 1974, 266pp ‘Uranium resources 2 Brookins, D.G. 1975-2000: Reserves and exploration potential in the United States’, American Sot Mech Engrs Symposium, 1975. (in press) 3 Brookins, D.G. ‘Uranium and thorium resources’ Part IV of State of New Mexico Governor’s Energy Task Force, Report of the Commission on Nuclear Energy, 1975, pp. IV-1 4 Patterson, J.A. ‘Outlook for uranium’ paper at 17th Minerals Symposium, AIME Meeting, Casper, Wyoming, May, 1974,9pp
reference searching time the reader is referred to the publications USAEC (now USERDA).’
of the
Summary of US uranium requirements for the period 1975-2000 Some of the material discussed here has been presented by the author.*13 The annual U,08 requirements to fuel reactors as of 1 January 1974 and those additionally forecast are shown in Figure 1. The annual requirements will reach about 3 x lo4 tonnes around 1980 (well above the past peak production of 1.79 x IO4tonnes in 1960). In brief, the approximate projected needs for uranium (in tonnes of U30x) for the period 1975 to 2000 assume an enrichment tails assay of 0.2% U308 up to 1981 and 0.3% thereafter. It is further anticipated that plutonium recycle will be 100% by 198 1. The initial enrichment transaction tails assay of 0.2% results from the USERDA eliminating some 8.17 x lo4 tonnes of UF, stockpiled at their enrichment plants. The cumulative requirements for uranium are shown in Figure 2. According to Patterson4 these forecasts are subject to any number of assumptions including (1) time lag for plant construction and operation, (2) growth in electricity demand, (3) tails assay selected at the enrichment plant, 137.17
Figure
1.
Annual
domestic b requirements reference
uranium producers
deliveries and
(modified
from
POLICY
September
1)
RESOURCES
1976
143
the relative costs of feed and separative work, recycle of plutonium generated in the reactors and recovered in the reprocessing step which could reduce uranium needs by approximately 20%, and (f-3)possible introduction of the breeder reactors. The decision to use the breeder reactor on a wide scale will not be made until at least 1988 and possibly not until closer to the year 2000. It is apparent from Figure 3 that even if the decision to use the breeder reactor is made in 1988 the effect on uranium requirements will not be fully felt until after the year 2000. Consequently, one is forced to make projected demands on the basis of the light water reactors until at least the year 2000 and perhaps after that date. There are many uncertainties surrounding the introduction of breeder reactors. Concern with safety aspects over the large amounts of plutonium generated by the breeders has been widely expressed by the various public media; hence my earlier comment about this decision as ‘political’ - at least in part. Of further concern is that the cost of the breeder reactor is increasing at an alarming rate. It has roughly increased by a factor of three and, with additional stringent safety requirements coupled with possible even greater costs, this factor may increase even more. Because of these uncertainties concerning the breeder reactors more attention is now being given to greater utilisation of the converter reactors which, while they breed in part (ie, Th-232 to produce U-233), much of the fuel is still enriched uranium. A typical high temperature gas reactor (HTGR) will use about 65% of the uranium needed to fuel a conventional LWR. The converter reactors were considered to be of relatively short-term usage
1830 -
1525-
Figure 2. requirements
Cumulative for ordered
plants (modified
144
1
uranium-
000
and forecast
from reference
1)
RESOURCES
POLICY
September
1976
Figure
3. Projected
requirements
for
breeder
reactors
reference
1)
annual
1988,
2000
(modified
domestic and no
I
1960
from
I
1990
I
I
2000
2010
Year
until the breeder reactors became widely used; it now appears, however, that the converter reactors may be used on a greater scale than previously anticipated. Figure 4 provides a closer examination of the uranium needs of the USA, with annual delivery commitments (as projected based on orders) and requirements for the period 1974-1985. It is all too obvious that the divergence of the two curves reflects the tremendous requirements relative to the delivery commitments as of 1 January 1974. Further, this particular graph has not changed appreciably even with assumed lower grade assay tails through the year 1974. As of 1 January 1974 utilities had contracted with uranium producers for delivery of some 1.22 x lo5 tonnes U308 over the next 20 years; only in 1974 and this year will deliveries be in excess of commitments. This has primarily resulted from slippage in reactor schedules; at present, deliveries are somewhat ahead of actual needs. However, this is, as shown here, a very short-lived phenomenon and price increases for uranium, now on the upswing, will continue throughout the 1970s and into the 1980s. The USERDA’s early 1974 figures on estimated uranium resources are given in Table 1. However, the cut-off costs are USERDA estimates of forward capital costs. Profit and ‘sunk’ costs such as expenditures for property acquisition, exploration and mining development are not included in determining in which category a reserve would be placed. It should be noted that reserves are ores in specific known deposits and their estimates are based on detailed sample data whereas potential resources are postulated to exist in known favourable geological environments. RESOURCES
POLICY
September
1976
145
D.A. and 5 Brobst, Pratt, W.P. United States Minerals ‘Introduction’, Resources, US Geological Survey Professional Paper 820, 1973, p 1 6 Finch, W.I., Butler, A.P., Armstrong, F.C. and Weissenborn, A.E. ‘Uranium’, US Geol. Surv. Prof. Paper 820, 1973, p. 456
In terms of the minimum anticipated cumulative demand (MACD) for identified and hypothetical resources, Brobst and Pratt5 list, respectively, figures of II (ie domestic resources 2 to 10 times the MACD) and III (ie domestic resources 0.75 to 2 times the MACD). Stated in another way these data infer that our uranium resources should be sufficient to about the year 2000 but that they will diminish after that time unless new deposits are found. It is essential to note that Finch and others6 indicate our known reserves to be between 2.27 x lo5 to 2.72 x lo5 tonnes of readily recoverable U308. Even the addition of perhaps some 1.8 x lo5 tonnes from paramarginal reserves totals only 4.54 x lo5 tonnes; less than one-quarter the projected amount needed by 2000. Consequently, our uranium reserves are not adequate to meet the projected demand. Types of deposits The most abundant uranium deposits are those classified as peneconcordant deposits, those in which the uranium is concentrated, commonly in close association with organic carbonaceous matter, in fluvial, lacustrine, and near-shore marine deposited sandstones interbedded with mudstones. Uraninite (uranium oxide) and coffinite (uranium silicate) are the main ore minerals; they commonly fill voids in the sandstones but occasionally replace older mineral grains. The 50 80/
/
// /’ 40 64-
Figure
4.
commitments (modified
from
Annual and reference
0
delivery
Table 1. US uranium Cut-off cost per pound of Us08
146
1985
Yeor
1)
industry seminar’, Source: ‘Uranium AEC, GJO-108 (74). II parts, 1974
1
I 1980
1975
requirements
US
resources - January
1, 1974
Reasonably assured
(tonnes U308) Estimated additional
Total
fY0
306 249 000
630 405 000
936 654 000
$15 $30
468 000 630 000
900 000 1 530 000
1 368 000 2 160 000
RESOURCES
POLICY
September
1976
average grade of ore is 0.15 to 0.30% U308 with a cut-off of 0~08%~ for $22/kg. The ore is deposited in various geometries with tabular or lensoid masses and crescent-shaped ‘rolls’ being the most common. The deposits are sporadically distributed within the sandstones and commonly quite small although accumulations in excess of 9 x lo6 tonnes of ore are known. Conditions of formation for these deposits are not accurately known although it is speculated that deposition of uranium occurs at redox interfaces in ground water systems or mixed ground water-hydrothermal systems. Uranium is thought to be transported as hexavalent uranyldicarbonate ion which is reduced to tetravalent uranium in uraninite or coffinite concomitant with formation of pyrite and other minerals. The sandstone type of deposits constitute over 95% of the deposits known in the USA and are more or less restricted to certain geographic areas in the San Juan Basin, New Mexico; Colorado-Utah Basins; Wyoming Basins; Texas Coastal Plain. The assumed roll front in sandstone is under- and over-lain by impervious mudstone. The general model for sandstone types of deposits is that the ore-bearing solutions move down gradient and precipitate the ore at the redox interface. Whether or not the deposits are roll shaped or lensoid masses is uncertain as they vary from district to district; what is important is the location of the front for planning exploration projects. Let us also remember that in the exploration programme the drilling is often done through hundreds to thousands of metres of barren rock and that the ore is rather sporadically distributed. To emphasise this point let us consider a case, as in Figure 5, in which a hypothetical drill grid and the outline of a hypothetical redox front and ore zones are shown. The figure has been drawn to show all the drill holes missing the ore zones and also the many holes in both the oxidised as well as in the reduced ground. It is obvious that criteria must be developed to determine whether or not reduced ground is encountered, and this is being done. It is of greater importance to determine whether or not ore-bearing solutions have
Poleo - charnels
Figure hydraulic
5.
Assumed
direction
Pyrite-bearing
of
ground
gradient
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147
penetrated the rocks. Solutions to these problems will greatly reduce the drilling costs. Other deposits include Precambrian, uranium-bearing quartz conglomerates (important in Canada and South Africa but not in the USA), uranium-bearing vein deposits which occur as fissure and other types of fillings of rocks of virtually all ages, contact metamorphic deposits, and other minor deposits. These are described in greater detail in Finch and others.‘j A greater search for the uranium-bearing quartz conglomerates is warranted based on the reports presented at the conference on ‘Formation of Uranium Deposits’ (International Atomic Energy Agency, Athens, Greece, 6-10 May 1974). A virtually untapped source of uranium is phosphatic rocks enriched with uranium; although the percentage is low (O-007 to 0.07% U,Os) the tonnage is tremendous. Technological problems in removing uranium from these rocks have not been solved, however. The same can be said of marine black shales with low but significant concentrations of uranium. Further environmental restrictions may limit rapid development of these potential resources. Finch and others state: ‘Domestic speculative resources consist of (1) new districts containing types of uranium deposits found elsewhere in the United States, (2) types of deposits known only elsewhere in the world, and (3) new types of deposits’. They list margins and axial parts of sedimentary basins (especially those derived in large part from granite or volcanic rock terrains) as favourable targets. Exploration methods are usually those involving radioactivity measurements (ie conventional Geiger counters and more sophisticated scintillation counters) in conjunction with favourable geological criteria. On a nationwide scale it is apparent that more attention should be given to searching for non-peneconcordant types of deposits as well as for research in uranium recovery from phosphorites and black shales.
Comments on exploration The success of any exploratory programme for uranium depends on many factors, not the least of which are the drilling programmes and related additions to the national reserves. The period from 1948 to 197 1-1972 was marked by drilling and additions of reserves on the usual supply and demand formula in turn dictated by purchasing policies and/or constraints on the nuclear industry. The decline in drilling and reserve additions in the late 1950s was determined by factors other than those primarily related to the nuclear industry, and they are, in retrospect, exactly what one would expect. Similarly, the increase in drilling and reserve additions in the late 1960s in response to a growing nuclear industry is also predictable. However, for the period 1966-1969 the ratio of reserve addition/drilling (in millions of metres) was not as high as in the 195Os, which in turn is a reflection of discovery of many of the major orebodies during the 1950s plus increased drilling costs and shortages of drilling equipment and related factors in the 1966-1969 period, as shown in Figure 6. The ‘lag’ of approximately ten years (ie 1956-1966) fairly well summarises much of what we are today concerned with, ie drilling and reserve addition aspects of the nuclear picture were not recognised in view of future non-petroleum and coal energy needs. 148
RESOURCES
POLICY.September
1976
IO
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/I
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6_
drhng
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Figure additions
6.
Drilling
(modified
and
I
reserve
from reference
I)
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1966
g
Reserve
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1970
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The second drop in drilling-reserve additions occurred in the period 1970-72 and, fortunately, has been of relatively short duration. Uncertainties in the com.mitment to the nuclear energy picture coupled with environmental concern and other factors resulted in short-term cessation of purchasing policy. Not until the very early 1970s did the federal government fully commit itself to a viable nuclear programme. As a result, the estimated drilling footages for 1974 and 1975 are given1 as 8.8 and 10.4 x lo6 metres, respectively approximately double the footage drilled in 1973. Yet one cannot and must not assume that this very rapid increase in drilling will go hand in hand with an equivalence in the form of additions to our reserves due to the reality that new, large deposits are not necessarily unlikely to be found but will certainly be more difficult to find. This was the case for the boom years of the 1950s relative to a lesser boom in the late 1960s. Further, there is a finite limit to our drilling capacity. We do not have enough drilling equipment to expedite the uranium exploration programme unless extensive cuts into the equally viable petroleum and coal programmes are made. This, of course, is unlikely and unrealistic. Thought should be given, however, to assigning higher proprity to domestic drilling programmes for all energy-related programmes than to overseas ventures if Project Independence is to work fully.
Discussions and conclusions We are aware of the favourability of certain areas over others for Roughly 95% of our deposits occur in uranium exploration. sedimentary rocks of Cenozoic and Mesozoic age; notable among these are the deposits of the Grants Mineral Belt and other areas in the San Juan Basin of New Mexico, the Wind River, Powder River, and Shirley Basins of Wyoming, the Paradox Basin of Colorado and Utah, and the Texas Coastal Plain. yet these combined districts in terms of area are small compared to the estimated 6.73 x lo6 km* of sedimentary basins in the USA. That over 90% of our drilling occurs in the known areas merely reflects that it is from these areas that we in all probability will meet our short-term needs for uranium. In order to investigate and evaluate the remaining sedimentary basins non-drilling (supplemented by spot drilling) exploratory programmes RESOURCES
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7 ‘Uranium GJO-108
150
industry seminar’, USAEC, (74). II parts, 1974, Figure 3
are being conducted by the USERDA and the USGS. These studies, most of which are just being initiated or else have not been fully developed, should indicate more favourable targets for future exploration. One has only to glance at the NURE (National Uranium Resource Evaluation) resource regions map of the contiguous USA’ to see the discrepancies. The bulk of exploration is confined to resource regions in the San Juan Basin, Wyoming, and coastal Texas. Yet, based on geological inference, one could argue for pilot exploratory programmes in many of the other resource regions. Number 13, which encompasses Kansas and most of Nebraska, Iowa, Missouri, Oklahoma, Texas, and vast amounts of Arkansas, Colorado, New Mexico and even part of Wyoming is well suited for the hydrogeochemical-soil sampling projects contemplated by ERDA and it is noteworthy that some uranium has been found in this region (ie west Texas). Similarly, one could argue that Nevada, in resource region 5, demands attention due to the abundance of favourable source (ie acidic, volcanic) rocks known to occur in the area; again, spotty uranium occurrences are known. Geological criteria have not yet been developed to comment on the favourability of regions east of the Mississippi River although it is known that vast amounts of uranium, although at low grades (ie Chatanooga shale), occur in these regions. It is unrealistic to think that the major quantity of uranium has been concentrated in just the areas now being actively mined; yet, at the same time, it is also unrealistic to think that any simple exploratory programme is going to reap ‘immediate’ results from the virtually untapped non-producing areas. It is now appropriate to address the ‘whys and hows’ of immediate and long-range aspects of the uranium picture. The short-term needs, say to 2000, can probably be met by continued exploration and development of known areas and more likely sub-economic areas, especially if foreign uranium is added to the reserves. However, even if the breeder reactor were in full operation by 2000 or shortly after which is unlikely based on comments made earlier - our known uranium reserves simply do not meet the projected demand. For the post-2000 period the picture is indeed bleak unless new uranium deposits from previously undiscovered areas are found or technology (and other) problems are overcome to assure a continued supply of uranium until some type of stable energy growth is met (ie not necessarily zero energy growth but growth such that supply can cope with demand). To do this the inventory and evaluation programme of the USERDA and other agencies must be complete, preferably by 1990, to allow industry, with the help of the state and other federal government agencies to develop the new sources.
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1976