Atomic Energy of Canada Limited

OUTLOOK FOR CANDU REACTORS

PART 1: TECHNICAL PART 11: ECONOMIC

by

D.G. HURST

Papers presented at the IAEA International Survey Course on Economic and Technical Aspects of Nuclear Power, Vienna, September 1-12, 1969.

Chalk River, Ontario

Januory 1970

AECL-3553 ATOMIC ENERGY OF CANADA LIMITED Chalk River Nuclear Laboratories

OUTLOOK FOR CANDU REACTORS PART I : TECHNICAL PART II : ECONOMIC

by D. G. Hurst

Papers presented at the International Survey Course on Economic and Technical Aspects of Nuclear Power, sponsored by the IAEA at Vienna, September 1-12, 1969.

AECL-3553 OUTLOOK FOR CANDU REACTORS PART I : TECHNICAL PART II : ECONOMIC

by D. G. Hurst

ABSTRACT

The CANDU reactor system, established at NPD and Douglas Point, is the basis for two of the world's large nuclear generating stations - Pickering and Bruce - now under construction. Further evolution of the system will result from materials development, fusl modifications, and higher thermodynamic efficiency, but with firm guidance by cost evaluations that are kept fully up-to-date. Significant reduction of capital cost should be attainable without seriously affecting the already low fuelling cost.

Papers presented at the International Survey Course on Economic and Technical Aspects of Nuclear Power, sponsored by the IAEA at Vienna, September 1-12, 1969.

Chalk River Nuclear Laboratories January 1970

AECL-3553 Perspective d'avenir pour les réacteurs CANDU 1 Partie: Aspects techniques 2 Partie: Aspects économiques

par D.G. Hurst Mémoires présentés au Colloque international sur les aspects économiques et techniques des réacteurs de puissance organisé à Vienne par l'Agence internationale de l'énergie atomique, du Ie* au 12 septembre 1969.

Résumé

La filière CANDU, employée dans le NPD et à Douglas Point, sert de base à deux centrales nucléaires - Pickering et Bruce - actuellement en construction qui compteront parmi les plus grandes du monde. La filière CANDU va connaître une évolution résultant du développement de certains matériaux, de modifications apportées au combustible, d'un rendement thermodynamique accru, mais tenant compte des évaluations de coût tenues constamment à jour. Une réduction importante des investissements devrait être possible sans augmentation du coût de l'approvisionnement en combustible qui devrait rester bas.

L'Energie Atomique du Canada, Limitée Chalk River, Ontario Janvier 1970

AECL-3553 -1-

OUTLOOK FOR CANDU REACTORS PART I: TECHNICAL

by D. G. Hurst

1. 1 Introduction

I am very pleased to have this opportunity to discuss once again the outlook for CANDU reactors, which are heavy-water moderated pressure tube reactors without restriction on the fuel and coolant con- tained in the pressure tubes. It is ten years or more since I was pub- licly involved in discussions of this topic. At that time the operation of any power reactor using heavy water was some years away - the commis- sioning of the NPD reactor took place in 1962. We, the proponents of heavy-water, gave theoretical proof of a promising outlook and others gave theoretical proof of failure. Today we no longer rely on theory; we have a major heavy-water power reactor program underway.

1. 2 Survey of Operating and Committed CANDU Reactors

On Figure 1 are shown the operating and committed CANDU nuc- lear power plants representing an investment of more than lj billion dollars. Note that the word CANDU is followed by PHW (Pressurized Heavy Water) or BLW (Boiling Light Water) signifying the coolant and a number giving the electrical output. The first three stations, NPD, Douglas Point, Gentilly, although operated by electric utilities, are owned by AECL. The Pickering and Bruce stations on the other hand, which together require an investment of about 1. 4 billion âollars, are wholly utility owned. The utility, Ontario Hydro Electric Power Commission, is a provincial organization in no way controlled by AECL or the Federal -2-

6000 BRUCE 4 x CANDU - PHW - 750 —

5000

PICKERING 4000 1 4 x CANDU- PHW-500 .r GENTILLY

3000 CANDU-BLW - 250 DOUGLAS POINT CANDU - PHW - 200 2000 - P n \ \ N. s- CANDU-•PHW-25 \ 1000 - \CANDU •BHW-25-^ \ \ \ 1 V i i i i i 1 i i i i . i , N 0 960 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 1979 IN SERVICE DATE

Figure 1. Nuclear Power Commitment in Canada -3-

Government and its decisions to proceed with Pickering and Bruce removes the sometimes implied criticism that the power reactors in Canada are D2O because AECL blindly follows its owr. predilection. Utilities make investments of this magnitude only after hard-headed scrutiny of all alter- natives.

Not included on this figure are the commitments of India to 800 MWe from similar reactors, the 137 MWe KANUPP plant being built in Pakistan by Canadian General Electric, and the plans of other countries for heavy- water reactors.

Tvluch information on CÀNDU reactors is in the literature, for example, the Canadian contributions to the Agency "Symposium on Heavy Water Power Reactors" September 1967. Let us look in more detail at the solid prospects for CANDU shown on Figure 1.

NPD

NPD has been in operation since 1962 and the details up to September 1967 are given in (1). Its success has been one of the factors leading to the major commitments. It has fulfilled its primary purpose but is continued in operation as a training centre and a test bed for new equipment and operating methods. During the summer of 1968 changes were made to per- mit net boiling and throughout the 1968-69 winter run it operated smoothly in the boiling mode with net exit quality of 13% and an output of 25 MWe (gross).

Douglas Point

The 200 MWe Douglas Point reactor is still in its "shakedown" stage which the operations staff expect to see last for 5 years, i.e. they do not feel that a meaningful on-line capability figure can be expected for -4- another year or so. This is in line with experience elsewhere. Although Douglas Point was planned as a "full-scale" power station under the cond- itions existing in the Ontario system and taking into account available turbine sizes, these conditions have changed so much that 200 MWe is no longer "full-scale" and 500 MWe and 750 MWe are more appropriate. The scaling-up is also advantageous economically.

The history of Douglas Point is checkered. During the crucial winter periods when full system capability is required it has come through adequately, but there were early problems with purnp seals and bearings (now hopefully solved) and teething problems with the fuelling machines which are of a somewhat different design from NPD.

Experience with NPD and Douglas Point has been published and reference may be made to some of the more recent papers (1, 2, 4).

Gentilly

With one exception the committed CANDU reactors are cooled by heavy water. Other coolants have been kept in mind and development effort has been expended on the more promising. A comprehensive review (3) was made in 1962 of CANDU variations from which four coolants - heavy-water, light water fog, boiling light water, and organic - were selected for quantitative comparison. Cost studies gave organic coolant a slight economic edge with boiling light water next. However, the economic assessment of organic involved some parameters which had not been fully substantiated and accordingly the committee did not give organic top priority but recommended vigorous development of fog and boiling light water and also continued development of organic coolant. As a result of further studies, construction was authorized in 1966 of a 250 MWe BLW (Boiling Light Water) prototype at Gentilly in the Province of Quebec as a -5-

joint project of AECL and Hydro-Quebec. The design and construction have progressed well, in spite of early labour difficulties not arising locally. The predicted cost appears to be a good estimate.

The BLW reactor, as represented at Gentilly, is an advance but it contains greater promise still with higher steam quality. The current value of 16. 5% exit quality is imposed by the decision to avoid dryout with a 50% margin, i.e. the critical power ratio is 1.5. As heat trans- fer data accumulate it should be possible to operate much closer to 1. The result will be a higher exit quality with accompanying higher burnup which, together with smaller reactivity hold-up, higher efficiency, and elimination of high temperature D,O, will keep BLW in the competition.

1. 3 Industrial Participation

From the early days of the Canadian power program the intent has been to involve industry to the maximum extent possible. Through design and construction of NPD, the Canadian General Electric Co. Ltd. (CGE) acquired the necepsary know-how to enable them to bid successfully on the KANUPP power reactor in Pakistan and the WR-1 research reactor in Canada. The power reactor design group is at present merged with AECL, providing a coordinated organization for supply of reactors.

Canadian design and consulting firms have been active in a number of nuclear projects throughout the world using experience gained in Canadian work.

All reactor components are obtained from industry. Because of their specialized technology and the small volume to date, the pressure tubes and sheaths have been obtained from the USA, but with the large reactors now committed the market will support Canadian production, -6-

and at least two companies will shortly be qualified to produce pressure tubes. Eldorado Nuclear Ltd. has set up a zirconium billet production plant.

The fuel program has been most successful. Close liaison was maintained among the design group, the two manufacturers who set up production shops, and the fuel development group at Chalk River which had the use of fuel testing loops. Every effort was made to ensure reli- able fuel operation at minimum cost. Both aims have been achieved and two firms are able to offer fuel at a price which promises fuelling cost in the region 0. 6 to 0. 8 mills/kWh iven without credit for spent fuel.

1. 4 Evolution of Current Types

The operation of NPD and Douglas Point, and the advanced stages of construction of Gentilly and Pickering I and II give us a real vantage point from which to look ahead. The commitment of Pickering and Bruce, each of which is a major project among the world1 s nuclear power stations, provides a firmly encouraging outlook in the direction of gradually evolving standard CANDU-PHW reactors.

There should be a steady evolutionary progress of both PHW and BLW. The design of Pickering incorporates lessons learned from Douglas Point, and Bruce will make use of the learning and development up to the latest possible moment. We do not expect to stop there. The materials develop- ment program can be expected to produce improved alloys that will permit higher temperatures and pressures with a resulting gain in efficiency. Fuel modifications, such as use of Pu, will permit variations. Non-uniform cores, e.g. with different pressures, may also have some advantages. None of these is a major change but some will certainly be introduced as -7-

PHW reactors are built.

An analysis was made this summer to arrive at a technically sound forecast of possible parameters of CANDU-PHW and BLW-J500 MWe reactors for near-term commitment, i.e. to follow Bruce, without the need of a prototype. These reactors are of interest in themselves, and they also furnish a much-needed reference for judging other coolants.

Both natural and enriched uranium were considered with approp- riate .nodifications in the design (e.g. 28-element fuel bundles and'6 MW per channel for natural uranium PHW,. 37-element and 8. 8 MW per channel for 1% enriched uranium).

Without plutonium credit the optimum enriched reactor was margin- ally (0. 03 to 0. 08 mills/kWh) ahead of the natural, but with the credit this advantage was negligible at $10 per gm fissile Pu and would reverse at higher Pu value or higher uranium cost.

1. 5 Higher Efficiency

There is a wide spectrum of possibilities for change in the reactors, from straight design alterations through the evolution discussed in the prev- ious section to major changes requiring many years of development. In this and the following Sections some of the possibilities are mentioned.

Over the past 40 years the efficiencies hi large fossil-fuelled power stations have increased from about 25% to 40% with resultant gain in econ- omy. Some examples of nuclear power stations are shown on Figure 2.

Gas-cooled thermal reactors and sodium-cooled fast reactors prom- ise efficiencies above 40%, roughly the same as conventional plants. On the other hand, economic optimization of water-cooled reactors has resulted -8-

40

HTGR (PERCE * u 35 ICIE » IL. «JL UJ BWR DBLW • PHW IO N D BLW 30 PHW x BWR

STA T + PWR MAGNOX O MAGNOX °—8 A AGR V HTGR • PFR 25 I I I960 1965 1970 1975 COMMISSIONING YEAR

Figure 2 -9- in pressures and temperatures well below those in conventional plants because of the penalties imposed by thickened pressure tubes or pressure vessels. Consequently the thermal efficiencies of water-cooled nuclear plants are relatively low and the step from 30% to 40% is a potential bonus. Because of the possible bonus a committee at AECL has been seeking means to realize this potential in the CANDU reactor (8). The development program that will grow from *.ne search for high efficiency is a long-term one and will not be allowed to interfere with priority work for the 5500 MWe nuclear capacity instailed or committed in Canada.

Various coolants - water (including steam), organics, gas, liquid metal, molten salt - were considérée, with steam turbines as prime moverp. The steam supplied from current water-cooled reactors is very close to saturation. For efficiencies approaching 40% or higher it is clear that the steam entering the turbine must be superheated. The super- heat can be added to the steam either in the reactor or from an alternative coolant. In-reactor superheat technology that could be put into effect now involves stainless steel cladding, enriched fuel and low pressure (50 bars). Several studies of this concept elsewhere have been terminated and this approach is of secondary interest to us. A path likely to be pursued is the development of zirconium alloys with good strength at high tempera- ture (500° C) and a longer-term study of graphite fuels and ceramic tubes for use at top modern steam temperatures.

The operation of the WR-1 reactor has given AECL. expertise with organic cooling, and for a significant near-term increase in efficiency to the neighbourhood of 40% organic cooling offers the best promise.

The three other coolants mentioned are alternatives to organic for out-reactor superheat but any application in our program is remote. -10-

1.6 Valubreeder

The availability of larger reserves of thorium than uranium and the superior properties of U-233 in thermal reactors (an rj value of 2.28 and a predominantly 1/v cross-section) has led to world-wide interest in thorium-based fuel cycles.

A fuel cycle named the Valubreeder has been proposed by Lewis (5). This can take various forms and is being improved and assessed but the basic concept rests on the high value of U-233, exemplified, for example, by the current U.S. offer of up to $14 a gram for pure U-233 and on the greater cross-section of thorium as compared to uranium. Whereas the production of Pu in natural uranium power reactors is about 2. 7 g Pu-239 per kg of U, the equilibrium production of U-233 is typically 16 g per kg of thorium. At $13/g U-233, this makes the value of a kg of irradiated thorium over $200, (minus processing costs) and is the basis for the Valubreeder name.

There are many forms in which the fuel cycle could be employed in CANDU reactors and these are being reviewed. The flexible fuelling arrangements of CANDU permit the smooth introduction of new fuel cycles into an existing reactor as they become economically desirable. In a cur- rent study of possible new reactors, organic coolant (for high efficiency) is combined with the Valubreeder thorium cycle.

1. 7 Plutonium Re-cycle

In the basic economics of the CANDU reactors no credit was claimed for the plutonium in spent fuel. Nevertheless, the plutonium is valuable, and off-shore sales of spent fuel, already arranged, will bring appreciable revenue. Over the next ten years nuclear power in Canada will grow to a •-11-

magnitude that can justify, on economic grounds, a plutonium extraction plant, and credit for spent fuel is routinely estimated for future reactors. From the earliest days of our power program, plutonium re-cycle has been studied, but only now has the necessity for hard decision been immin- ent. The first use may well be in booster rods as an alternative to U-235 for Xenon override. This could probably be accomplished without much basic fuel development but with perhaps some reactor physics measure- ments and full-scale irradiation tests of prototype rods.

The re-cycling of plutonium to give reactivity for prolonging the irradiation of natural uranium or for supporting thorium irradiation will be in economic competition with sale of plutonium, most likely for fast reactors. If re-cycling proves desirable it will either be mixed with uran- ium or in "spikes", i.e. plutonium fuel elements without uranium. Each method has advantages and disadvantages and as yet there is no overriding preference. Fuel for high temperature superheat may require nearly pure fissile material and if so would provide another application of plutonium.

1. 8 High Density Fuel

High density fuel is attractive because it improves the competitive position of the fuel for neutrons, thereby increasing the burnup, and puts more uranium into the same volume thus leading to lower fabrication costs per kg of uranium. The latter appears to have more importance in the cost.

Irradiation tests of l^Si show that the pronounced swelling, which

prevented its early acceptance, can be accommodated. Plans are underway

for power reactor tests of bundles.

Uranium carbide, although it reacts readily with water, is a prom-

ising fuel for organic coolant. -12-

1. 9 Electro-Nuclear Neutron Supply

The operation of a reactor depends or a small margin in the balance of neutrons. A slight shift in the balance can significantly alter the fuel burnup. If neutrons could be made available from an external source, the complete utilization of thorium and uranium might be achieved in thermal reactors. The spallation of heavy elements by high energy protons is a promising source of neutrons that might profitably be included in a power system because the production of a neutron by this reaction requires only about 25 MeV whereas the fission reaction that c&n result from the neutron produces about 20Q MeV. Some studies have been made of such possib- ilities (6).

1. 10 Development^ Program

If we are to fulfill the wide-ranging needs of our program, we must apportion our development funds wisely between the needs of our currently committed reactors and the needs of the future. There are some general guidelines for our longer-term program. Zirconium-based alloys will continue to be of major interest for some time. The development of alloys with good strength and creep properties at high temperature is a central requirement that could benefit both near-term and long-term reactors. The top usable temperature of organic coolant is likely to be in the region of 425° C with sheath temperatures somewhat above this. In-reactor super- heat requires steam temperatures of 450° C'and preferably higher to be economically justified. Current zirconium alloys are not strong at these temperatures but we have done laboratory work on more complex alloys containing two or more additives such as Sn, Mo, Nb, Al and Si. Certain of these alloys have properties which warrant testing in the form of pres- sure tubes. The long-term move to much higher temperatures will require -13-

ceramic developments and improved insulations.

An illustration of the magnitude of the effort required may be seen in the development of the Zr-2|% Nb alloy which is to be used in Gentilly pressure tubes arid in later PHW reactors beginning with Pickering III and IV. Over the 10-year interval during which this alloy has been brought to the stage of acceptance in these reactors about $10 million has been spent on development, but in return the use of Zr-Nb pressure tubes for reactors going into service between now and 1980 will save about $30 million mainly through increased fuel burnup.

Adequate heat transfer data are not yet available for direct applic- ation to the conditions in fuel bundles with two-phase flow. The design depends on correlations extending and bridging the experimental results. Until direct experimental confirmation is available, designs may be some- what conservative. There has been a continuing program on this topic at AECL with close contact with workers elsewhere. We see the need of a continuation of this effort, particularly as regards the dryout condition with two-phase flow. In-reactor measurements, as are done in NRU loops and planned for Gentilly, are expensive and complicated experiments but well repay the effort.

In establishing the basic CANDU reactor system, the reactor physics was kept relatively simple and straightforward with closely related experi- mental backup. Elaborate computer programs played a secondary role. As we look forward to the long-term developments we expect to rely more heavily on detailed calculations for new fuel channel configurations. Our computational facilities are fully up to date, permitting appropriate complex- ity in our codes.

The excellent loop facilities of NRX and NRU have been a major -14-

factor in the advancement of the CANDU fuel design.

1.11 Complementary and Competitive Role

The technical qualifications of CANDU give high promise of its importance to world nuclear power programs. It is one of the outstanding advanced converters and as such could provide plutonium to any large-scale fast breeder program.

Within the Canadian framework it is being introduced as an altern- ative to fossil-fuelled stations in systems which have been predominantly hydroelectric. For example, in Ontario where the early electricity supply was based almost entirely on hydroelectric generation, there are ample supplies of uranium but no fossil fuel. The installed hydroelectric cap- acity is about 6500 MW and as the hydroelectric potential is almost fully utilized, a similar capacity of thermal plants fuelled with imported coal is installed or planned. The nuclear plants will not only improve the foreign exchange situation but will also reduce the cost of power. The mixed system of hydro, fossil and nuclear plants will give the system engineers good scope in meeting base and peak loads with maximum economy. -15-

OUTLOOK FOR CANDU REACTORS PART II: ECONOMIC

2. 1 Introduction

The controlling factor in application of nuclear power is the economics.,, Twenty years ago there was general talk of the desirab- ility of nuclear power, and proposals were beginning to emerge. The economic possibilities inherent in heavy-water became quantitatively encouraging about that time with the achievement of 3000 MWD/T irradi- ation in original NRX fuel and the establishment of a high-pressure water-cooled loop in NRX.

Several years later a nuclear power feasibility study was under- taken at Chalk River by a team of engineers assembled from Canadian utilities and industries. Their initial recommendation was for the construction of a demonstration reactor, NPD, of 20 MWo net output to which funds were committed in 1955. The design, construction, financ- ing and operation of NPD involved three organizations - AECL, OHEPC, and CGE.

TABLE 1

CANDU POWER REACTORS: ORGANIZATIONAL RELATIONSHIPS

Reactor Owner --^ Designer Operator

NPD AECL ÇGE/AECL OH Douglas Point AECL AECL/OH OH Gentilly AECL AECL/HQ HQ Pickering OH AECL OH Bruce OH AECL OH -16-

Table 1 - continued -

AECL Atomic Energy of Canada Limited - Federal Crown Co. CGE Canadian General Electric Co. Limited - Private Industry HQ Hydro-Quebec - Provincial Utility OH (OHEPC) Ontario Hydro Electric Power Commission - " "

Meanwhile continuation of the study directed towards a large power reactor resulted in a proposal for pressure tubes instead of a pressure vessel and for on-power refuelling of individual channels. Consequently work on the design and construction of NPD as a pressure vessel reactor was sus- pended in 1957 and these new features were incorporated in the NPD reactor.

As a result of increasing power demand in Ontario and the approach- ing full utilization of hydroelectric resources, thermal plants were being

*• introduced into that province. Lack of fossil fuel, large uranium reserves, and low interest rates and carrying charges in the publicly owned utility all favoured ruclear over fossil fuel. For these reasons a decision was taken to build the large (200 MWe) reactor at Douglas Point. With the confidence engendered by NPD and Douglas Point, Ontario Hydro has committed the Pickering and Bruce stations (Table 1).

The Province of Quebec, with some undeveloped hydroelectric sites still available, has less urgent but similar interests in thermal power plants. Foreseeing the eventual introduction of nuclear power into its system, Hydro-Quebecfentered into an agreement with AECL for construc- tion at Gentilly of CANDU-BLW-250 when this was indicated as a promising CAN DU line (Section 1. 2). -17-

2. 2 Cost Studies: Optimization

During the feasibility study that led to the Douglas Point generating station, many variations were costed by hand calculations. The install- ation of a digital computer at Chalk River about this time made possible the programming of the necessary engineering, cost and reactor physics formulas. Their use developed into what wns perhaps the first power reactor optimization.

In addition to the initial optimization of a concept, the computer programs provide quick and reliable cost comparisons of alternatives that arise during the engineering design phase. This ready access to costs, coupled with technical considerations, enables the design team to operate efficiently by keeping to the most promising routes to low cost energy.

Great importance is attached to feedback of engineering experience and to ensuring that consistent ground rules and cost data are used in all computations.

The formula for unit energy cost given on Fig. 3 shows the three components: capital, fuel and operation. The net cost of fuel can be adjusted to allow for spent fuel (plutonium) credit.

The operational cost is not an important variable in the optimization.

It may include such items as D2O or organic makeup, and it decreases with unit size being less than | mill/kWh for large (500 - 800 MWe) units.

For the purposes of illustration, we may take as representative values C = 245 $/kW, A = 8%, H = 7000 h/year

P = 45 $/kg U, B =9.7 MWD/kg U, n = 0. 3 -18-

UNIT ENERGY COST CA J P = 10 H 24 Co (CAPITAL) + (FUEL) + (OPERATION)

c = UNIT CAPITAL COST $/kWe A = CAPITAL CHARGE RATE %/YEAR H = TIME ON-LINE HOURS/YEAR P = NET COST OF FUEL $/kgU B = FUEL BURNUP MWD/kgU NET STATION EFFICIENCY FRACTION

CO- OPERATING COST mills/kWh

Figure 3 -19-

and obtain 10 x 245 x 8 capital cost component = —-— = 2. 8 mills/kWh

45 fuel cost component = — r~- —-— = 0, 65 mills/kWh C.*T X 7» ' X U. J t (without Pu credit)

There is clearly less scope for cost reduction in the fuel cycle than in the four times larger capital component. Much of the long-term devel- opment is directed accordingly.

With the set of values above, a reduction of $8.75/kW cuts the capital component by 0. 1 mills/kWh. The return on a saving of 0. 1 mill/kWh will pay for considerable development. If the cost of energy from the nuclear plants forecast for installation in Canada during 1988 (4000 MWe) could be reduced by 0. 1 mill/kWh, the "present value" in 1988 of the accumulated saving over the life of the plants would be $3 9 million.

2. 3 CANDU Cost Estimates

Many unit energy costs are quoted in the literature and these differ for a number of reasons: the different reference dollar dates and allow- ances for escalation, the power generated, the number of units per station, the degree of sophistication in the estimates, etc. ^ In general the estimated costs have decreased with time from the early Douglas Point estimate of 5-6 mills/kWh.

Tnble 2 contains a recent estimate of capital costs for a 600 MWe plant. Estimates for Pickering and Bruce, in 1969 Canadian dollars, are 266 and 245 $/kW respectively. With annual charges appropriate to the utility system (based on 6. 5% interest and amortization only) and adding -20- fuelling and operation costs yields unit energy costs of 3. 9 mills/kWh and 3. 5 mills/kWh respectively. A reduction of at least 0. 2 mills/kWh due to revenue from spent fuel is anticipated.

TABLE 2

CAPITAL COST OF A CANDU POWER PLANT 600 MWe

Cost in (Millions of 1969 Canadian $) Nuclear Steam Supply System includes equipment, material, engineering management, reactor building, heavy water at $45/kg and a complete fuel charge at $50/kg 74. 9

Conventional Plant turbine generator, buildings, services, etc. 52.8

Other Costs construction plant, commissioning, training, interest during construc- tion, etc. TOTAL

i.e. $263 (1969 Canadian) per kW

Pickering and Bruce are the first stations of a truly commercial CANDU-PHW line and establish a marketable position for this reactor type. We should recognize that the costs just quoted are firmly based on engineered designs. The costs provided by the optimization programs for the development groups cannot be so accurately based on design because, by their nature, they are part of the decision-making process that sets the -21-

design. However, by careful effort they are kept realistic and in good agreement with the final outcome.

Mention was made in Section 1.4 of the outline of the PHW and BLW reactors that might follow the present commitments. The unit energy costs derived for these reactors from the costing programs run from about 2. 4 to 2. 8 mills/kWh, without credit for spent fuel.

2. 4 Comparative Costs

The heavy-water reactor has had a reputation as a high capital cost system compared to the light water enriched uranium system. This needs re-examination under modern conditions of large (500-1500 MWe) units, cheaper D2O, and some reassessment of other systems. The excess capital of the heavy water system is not as large as a quick look might suggest. Capital costs published for CANDU systems usually cover the complete station up to and including the electrical switchyard and half the initial charge of fuel. This should be kept in mind when comparing with published costs of other systems which are often not so inclusive.

Comparison may be made with a recently published capital cost study (7) for light water reactors (LWR1 s) which gives $200 US/kW for an 800 MWe light water plant to be completed in 1973. Converting to Canadian

dollars by a factor 1. 08 gives $2l6/kW for the 800 MWe LWR to be com- pared with $245,'kW fo^ Bruce, (which includes nearly $4/kW for half the first fuel charge). The difference of 245-216 = $29/kW is in accord with other estimates which indicate for CANDU a unit capital cost from 10 to 15% greater than for LWR. Certain likely trends (more expensive uranium, higher value of Pu, increase in plant size) improve the CANDU position in the comparison, but escalation and higher thermal efficiency (in its effect -22-

on fuelling cost) favour LWR. However, it may be more difficult, if not impossible, to increase the LWR efficiency significantly.

In many circumstances, the low fuelling cost of CAN DU more than compensates for the higher capital, A 1 mill/kWh lower fuelling cost will balance a unit capital cost difference of $50/kW at 14% fixed charge rate 10 14 (from the first term of Fig. 3 *^Q* = 1 mill/kWh if C = $50/kW) and about $90/kW at 8%.

2.5 Summary

The development of the CANDU reactor system has resulted in a utility commitment to two of the world's large nuclear power generating stations - Pickering and Bruce - with predicted power costs of 3. 9 and 3.5 mills/kWh (1969 Canadian currency) less any revenue from spent fuel. The 750 MWe units of the Bruce type may later be followed by 1500 MWe units incorporating improvements resulting from operating and design experience or development for which a unit energy cost reduction of almost 1 mill/kWh may be expected.

Changing the reactor coolant or fuel cycle may offer a further economic advantage but if a prototype is required, some difficulty may be encountered competing with the established line for the investment funds.

During the next few years, the promising lines will be carried further in development and their economic promise will be kept under review but they will face the problems of a newcomer in a well-established field of business. -23-

REFERENCES

(1) HORTON, E. P. , "NPD Operating Experience", Proc. Symposium on Heavy Water Power Reactors, IAEA, Vienna, September 11-15/67, 53-65 (SM-99/27)

(2) WILLIAMS, G.H., "Douglas Point Generating Station Commissioning", Proc. Symposium on Heavy Water Power Reactors, IAEA, Vienna, September 11-15/67, 83-101 (SM-99/28)

(3) A Committee of AECL Staff, "Power Reactor Development Evaluation", AECL-1730 (1963)

(4) MILLEY, D. C. , "NPD Operation over the Past Twelve Months, May 1/68 to April 30/69", Canadian Nuclear Association Conference, June, 1969 (69-CNA-527)

EVANS, R.J., "Operating Project Report - Douglas Point" Canadian Nuclear Association Conference, June, 1969 (69-CNA-528)

HORTON, S. G. , "Lessons Learned in the Operation of Canadian Nuclear Power Plants and their Application to Subsequent Designs", Canadian Nuclear Association Conference, June, 1969 (69-CNA-529)

(5) LEWIS, W.B., "Super Converter or Valubreeder - A Near Breeder Uranium Thorium Nuclear Fuel Cycle", AECL-308! (DM-94), (May 1968)

(6) "AECL Study for an Intense Neutron Generator - Technical Details", AECL-2600 (July 1966)

(7) Nuclear Industry, Vol. 16, #5, May 1969, p. 45

(8) HURST, D. G. , "Improving the Thermal Efficiency of CANDU's", AECL-3332 (June 1969)

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