Risk-benefit evaluation of nuclear power plant siting

Annals of Nuclear Energy, Vol. 3, pp. 489 to 500. Pergamon Press, 1976. Printed in Northern Ireland

RISK-BENEFIT EVALUATION OF NUCLEAR P O W E R P L A N T SITING J. M I E T T I N E N , I. S A V O L A I N E N , P. S I L V E N N O I N E N E. TORNIO and S. VUORI

Technical Research Center of Finland, Nuclear Engineering Laboratory, L6nnrotinkatu 37, SF-00180 Helsinki 18, Finland (Received 10 May 1976, and in revised form 28 June 1976) Abstract--An assessment scheme is described for the risk-benefit analyses of nuclear power versus conventional alternatives. Given the siting parameters for the proposed nuclear plant an economic comparison is made with the most advantageous competitive conventional production scenario. The economic benefit is determined from the differential discounted annual energy procurement cost as a function of the real interest rate and amortization time. The risk analysis encompasses following factors: radiation risks in normal operation, reactor accident hazards and economic risks, atmospheric pollutants from the conventional power plants and fuel transportation. The hazards are first considered in terms of probabilistic dose distributions. In the second stage risk components are converted to a compatible form where excess mortality is used as the risk indicator. Practical calculations are performed for the power production alternatives of Helsinki where district heat would be extracted from the nuclear power plant. At the real interest rate of 10% and amortization time of 20 yr the 1000 MW(e) nuclear option is found to be $9.1 m per yr more economic than the optimal conventional scenario. Simultaneously the nuclear alternative is estimated to reduce excess mortality by 2-5 fatal injuries annually.

1. INTRODUCTION Due to the increasingly acute dilemmas associated with the siting of power plants the pertinent risk evaluation methods have progressed rapidly in recent years and in particular after the issuance of the Reactor Safety Study in the United States, RSS (1975). Siting criteria are shifting to more quantitative items which necessitates the use and further development of risk-benefit assessment techniques combined with the alternative scenarios of power generation whether of nuclear or conventional origin. In this paper we wish to present a scheme which considers the pros and cons of the nuclear and fossil based power production and incorporates diverse hazards in a uniform perspective by deducing the total safety risks in terms of health and economic damage. Assessing these quantitatively expressed risks against the economic balance of benefits one should obtain a reliable basis for decision-making. Since both the nuclear and conventional power production is customarily the business of one and the same utility the technique does not directly favour any particular interest group. The methods described later are fully general and applicable to any proposed siting alternative as soon as the economic, meteorological and basic technical plant data are available. To illustrate the

course of the work we also present practical calculations performed in the case of the power plant alternatives proposed in the Helsinki area, map of which is presented in Fig. 1. Consequently this work has an immediate connection to problems of urban siting dictated by the use of the energy not only to produce electricity but urban district heat as well. The economic comparison of different power production scenarios is made by conventional accounting methods in Section 2. The alternatives studied in detail include one nuclear option corresponding to 1000MW(e) and three conventional alternatives. The discounted annual revenue requirement is computed for all these alternatives and the economic benefit of nuclear power is determined vs the most advantageous conventional scheme. The radiation risk entailing normal operation of the nuclear power plant is determined by examining the atmospheric dispersion of gaseous effluents. The release quotas of the airborne nuclides are based on the values measured in the U.S.A. In practical computations we have employed the meteorological statistics of the Helsinki region. In Sections 4 and 5 the accident situations at nuclear power plants are considered. The health hazards are determined on the basis of the release

489

490

J. M1ETrlNEN, T. SAVOLAINEN, P. SILVENNOINEN, E. TORNIO and S. VUORI

_ r'~

-~Oo~ •

~q'~/'~.

¢'~

,Centrle" of Hel.sinki

Gutf of FinLand

o

Fig. 1. Map of the Helsinki metropolitan area. I-1:site of the nuclear power plant;/x: sites of the conventional plants of the alternative 2 in Table 7. data obtained from RSS (1975). The model to consider the consequences encompasses certain improvements over the considerations in the same reference. The results are given in a probabilistic form. As to the thermal pollution only a short description of the studies is given. This is because of the fact that the degree of thermal pollution is closely related to specific sites. Given the configuration of the eon,,entional power plants we deduce the health risk in Section 7 by calculating the atmospheric dispersion of coal and oil contaminants. The contamination falls within the accepted limits but the detrimental quantities of sulphur dioxide yield a comparison basis when computed for the entire population in the area. Due to the different rates of fuel transportation to the plants considered we have also included the transportation risks in the total analysis. Since the pertinent risks are of widely different character the ultimate comparison is based on the estimated number of fatal injuries probably incurring when the different power production schemes are implemented. These considerations are based on the dose-fatality correlations found in the literature.

district heat transmission system in the cost calculations in a form corresponding to the most expensive variant. Secondly, the fundamental calculations are performed assuming a real interest rate of 10% which is relatively high and disfavours the nuclear option. The nuclear capacity corresponds to equivalent 1000MW(e) net of which 1000MW thermal is extracted to the district heating and the electricity output is reduced to 830MW(e) net. The fossil alternative comprises one condensing power plant of 500 MW(e) capacity and 5 back-pressure power plants, each equivalent to 100 MW(e). This conventional coal-fired combination was economically found to be the optimal solution in the case of Helsinki area. Two other conventional configurations were deleted in an earlier stage of economic optimization. According to power demand estimates the new production units should be introduced by 1985. The estimated plant investment costs are given in Table 1. The figures include the direct investment, interest charges during the construction, and reserve fuel storage. The initial loading is included in the nuclear option. The price level is fixed at January 1976 and no cost escalation is considered since the analysis is carried out in terms of real interest rate which is left to be a free parameter. Consequently the inflation can be conveniently taken into account. For the nuclear option only we have included an extra payment for the district heat transmission system: it is assumed that the conventional back-pressure plants are located in the immediate urban area. The transmission distance is 45 km from the nuclear power plant to the centre of Helsinki. In computing the fuel costs we have used the following unit costs for nuclear fuel: raw uranium $25/lb, enrichment $100/kg SWU, fuel fabrication $100/kgU, reprocessing and waste storage $175/kgU. The fuel cost equals then 4.3 mills/kWhr(e). In addition to the fuel costs the Table 1. Cost characteristics of nuclear and fossil plants (millions of U.S.$) Investment in heat Annual Investment transmission operating in plant system cost

2. ECONOMIC COMPARISON OF DIFFERENT POWER PRODUCTION ALTERNATIVES

A n attempt has been made to analyse the power production economics in a manner which is reasonably conservative from the viewpoint of nuclear power. From the various possible sites the most remote feasible location is selected for the nuclear power plant. This means that we have included the

Nuclear 1000 MW(e) Fossil 500+5 × 100 MW(e)

813.0

181.8

44.4

577.9

--

102.1

Risk-benefit evaluation of nuclear power plant siting annual operating expenditure in Table 1 comprises the repair and maintenance, staff and insurances. Of the $44.4 m some $5.2 m represents the operating cost of the heat transmission system and the rest is allotted to the nuclear power plant. The coal price had experienced a minor decline in 1975 and the price was set to 5.6 mills/kWhr(t). A load factor of 75% is assumed in all calculations. Based on the data given in Table 1 one is now able to perform the trivial competitiveness calculation. It is advisable not to fix the specific values of interest rate or amortization period but rather span a domain where all conceivable decisions and parameter values can be represented. Choosing an amortization period of 20 yr one concludes that the nuclear option is more economical in terms of the total annual energy procurement cost up to the real interest rate of 12.4%. Above this rate of interest the fossil alternative takes over. For example, if the real interest rate is ten per cent the annual savings are some $9.1 m in favour of nuclear. A change of +1% in the interest rate corresponds to a change of • $4.2 m in the economic benefit of nuclear power. In case the amortization is allowed to cover the entire plant life of 30yr, the break-even interest rate is 13.5% and the annual saving at 10% is $13.5 m. Another way of looking at the comparison is illustrated in Fig. 2, where the accumulated total cost of the two competing power production variants is shown. All the future operating costs are discounted to the present value at the commencement of plant operation using again an interest rate of 10%. It is seen that during the first 13.5 yr the revenue requirement is higher for the nuclear energy and subsequently the plant is paid off against the conventional variant. Figure 2 incorporates a cost band which defines the variation due to the district heat transmission cost. The curves are given for the transmission distances of 0 and 50 km. Concluding this benefit section of our analysis until the synthesis in the summary we wish to point out that there are frequently other important factors to be considered besides the pure economics. In our study we have also considered the energy procurement in terms of the domestic share of expenses incurred. In our case this factor is strongly in favour of the nuclear alternative which is presumably the case in those industrialized countries which do not have their own resources of fossil fuel. We have included the cumulative share of the import expenditures in Fig. 2. While the entire fuel cost is included there only a part of the investment cost can be regarded as contributing to the foreign

491

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0 0

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Fig. 2. Comparison of the cumulative energy procurement costs ( ) and their foreign shares ( - - - ) between the nuclear and most economic conventional alternative.

share. On the average we have estimated that the imported part of the total investment amounts to 41.5 and 35.0% in the case of the nuclear and conventional alternatives, respectively. The heat transmission system involves purely domestic supplies. 3. R A D I A T I O N

RISKS IN N O R M A L

OPERATION

In this study we have considered only the airborne effluents generated in the normal operation of a light water reactor. The following three exposure pathways are considered: whole body dose due to external gamma radiation from the release plume, inhalation dose and external gamma dose from the contaminated ground. As to the whole body doses from the gaseous releases the external radiation from the plume is clearly the most significant contributor. Waterborne effluents and ingestion pathways are not taken into account. On the basis of the literature they can be expected to become critical only for small population groups. Neither have we considered transpiration of tritium, because its releases to the atmosphere are small and the proposed site lies on the coast of sea. The dose calculations have been carried out with our computer code A R A N O (Assessment of Risks of Accidents and Normal Operation), which is

492

J. MIETTINEN, I. SAVOLAINEN, P. SILVENNOINEN, E. TORNIO a n d S. VUOR!

mainly aimed for calculation of accident consequences, but is also applicable to calculation of collective and individual doses risen from the gaseous releases during normal operation. The release magnitudes used in our calculations are based on the U.S. experiences. We have considered separately the gaseous releases from the PWR and BWR plants. It is found that statistical distribution of the annual release magnitudes can roughly be described by a log-normal distribution. In Table 2 the median and 95% upper limit for the release magnitudes of noble gases, and iodines are shown (Report on Releases . . . . 1973; Summary of Radioactivity R e l e a s e d . . . , 1975). For the median release, the average annual whole body dose at 1500 m from the plant is about 2 m r e m for BWR and less than 0.01 mrem for PWR. The collective doses brought about by the different release situations are also shown in Table 2 or the surrounding population inside 100kin from the proposed site (about 1.2 million). The limit of the annual collective dose proposed by the authorities is 500 manrem per 1000 MW(e) and thus in all the above mentioned release situations this limit is not exceeded. The annual collective dose to the same population induced by the average natural background (about 0.1rem) is 120,000 manrem.

Table 2. Measured airborne effluents from U.S. light water reactors (1972-74) and collective dose for the population around the proposed site (inside 100 km) Airborne effluents (Ci/yr) PWR Nuclide

median

95%-limit

Ar-41 2.13E+1" 2.13E+1t Kr-85 2.51E+2 8.90E+3 Kr-85M 5.63E+ 1 2.15E+3 Kr-87 4.41 4.41 Kr-88 3.79 3.79 Xe-131M 3.82E +3 1.00E+6 Xe-133 3.37E+3 2.00E + 6 Xe-133M Xe-135 1.24E + 2 1.24E + 2 Xe-135M 1.82E + 2 1.82E+2 Xe-138 1-131 1.45E-2 1.10E+I 1-133 6.33E-5 6.33E-5 1-135 1.50E-5 1.50E-5 Collective dose~t <1 75 (manrem)

BWR median

95%-limit

1.65E+2 3.29E+3 3.73E+4 9.15E+4 1.02E+5

1.65E+2 2.24E+4 2.72E +5 8.08E+5 6.97E+5

7.64E + 4 2.30E + 4 1.56E+5 1.40E+4 5.36E + 4 1.97 2.81 4.15 50

7.40E +5 2.30E + 4 1.36E+6 1.40E + 4 3.64E +5 2.42E+1 4.57E+1 1.07E+2 380

* This means 2.13x 101. t The 95%-limit is assumed to be equal to the median, if the statistics is too limited for the nuclide. Release height 150 m.

4. H E A L T H RISKS IN ACCIDENTS

The large inventory of radioactive materials contained in the core combined with the possibility of a number of simultaneous faults makes a large reactor accident possible, which under unfavourable weather conditions may involve considerable health effects and economic damage to the environment. The analysis of the effects from accidents can be divided into two main parts. The first task is to define the possibilities and magnitudes of accidential radioactive releases from a nuclear reactor. The second phase is to calculate different environmental consequences under various weather conditions. The final results of these two stages are the probability distribution of the consequences of the accidents. In this study the accident probabilities and release magnitudes from the Reactor Safety Study (RSS, 1975) are employed unchanged. Because the estimated accident consequences of the different LWR types do not differ substantially, we consider BWR only and calculate the consequences based upon the probabilities and release magnitudes of BWR-release categories. Our model is contained in the computer code A R A N O . In the following description attention is paid mainly to points where the present calculation model differs from that of RSS (1975). In the dispersion model the concentrations of radionuclides in the release plume are assumed to be normally distributed both in the vertical and horizontal directions. The values of the vertical standard deviation for different weather stability categories are corrected using the method proposed by Smith (1974) to take into account the variation of surface roughness depending on the form of terrain in different dispersion directions. In this study three terrain roughness classes are used. As to the plume rise only the initial heat content is taken into account and the radioactive heating is neglected. Further the plume is assumed not to be able to penetrate the inversion-layer and the maximum value used for the height of the plume midpoint is 0.8 times the mixing height. The values for mixing heights used in this study are taken from Klug (1969). To take into account the expansion of the plume during the rise and due to the turbulence region caused by plant buildings the plume is moved backwards to a virtual source point until the dimensions of the plume at the actual source point correspond to the calculated effective initial radius (Clarke, 1973). This radius is assumed to decrease with declining wind speed. In the dose calculation the external gamma dose

Risk-benefit evaluation of nuclear power plant siting is interpolated from a normalized submersion gamma dose data file for different stability categories, roughness classes and release heights. This data file has been created using a separate computer code, which carries out the 3-dimensional numerical integrations required in the calculation of external doses from the release plume. In the calculation model it is possible to consider the effect of evacuation but this option is used only to truncate the integration of the external gamma dose from the contaminated ground, when the early health effects are estimated. The integration time is assumed to be one day. In the estimation of late health effects the integration is continued, but the additional individual dose after 1 week is assumed to be at most 10 rem, which is the criterion for the relocation in the calculation of economic losses. Before adding the dose contributions a shielding factor for external radiation from the cloud and the ground has been taken into consideration. In this connection the population is divided into two groups, one including the population which is expected to be in the open and the other one including those indoors. The first group (35%) has a shielding factor of 0.8 and a breathing rate of 3.5 × 10 -4 m3/sec and the second group (65%) 0.35 and 2.3× 10 -4 m 3 sec, respectively. In the case of early effects this division into two population groups increases significantly the number of persons. affected, if the maximum doses are near the used dose thresholds. The weather statistics for the site concerned contains the distributions of wind direction (12 sectors), wind speed (7 classes), weather stability (6 classes) and rain (2 classes). Every dispersion sector (30 °) is associated with a specific terrain roughness class and population distribution. As to the relationships between different health effects and radiation doses presented in literature no definite choice is made. Therefore the early effects of radiation are primarily presented in the form of numbers of persons exceeding given dose limits and in the case of late effects our primary results are the whole body and thyroid population doses. The complementary cumulative probability distributions for the number of people exceeding whole body doses of 10, 100, 200, 300 and 500 rem are presented in Fig. 3. Because the uncertainty in dose-response relationships is not included in these curves the uncertainty range on the magnitudes is estimated somewhat smaller than in RSS (1975). Upper and lower limits for the. num-

493

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~, 10- s

N :,o-'

N\

.-._

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10 2

10 3

104 10 5 10 6 N (number of people)

Fig. 3. Complementary cumulative probability distributions for the numbers of people exceeding certain dose limits (10-500rem) from reactor accidents BWR1BWR5. Note: Approximate uncertainties are estimated to be represented by factors of 1/3 and 3 on consequence magnitudes and by factors of 1/5 and 5 on probabilities.

bers of early fatalities are presented in Fig. 4. The calculations were carried out on the basis of linear dose-response curves (A: 200-500rem, B: 320750 rem). The first curve assumes ineffective treatment and the latter supportive treatment of patients. In the curve B' the better shielding factor and the average breathing rate are used for the whole population. Upper and lower limits for the number of early illness cases are estimated using the numbers of people exceeding whole body doses 100 and 200 rem (Fig. 3). Compared to our results RSS (1975) gives smaller probabilities for the number of early fatalities in the range below 1000 cases, although the probabilities for maximum consequences are in rather good agreement. Possible reasons to this difference in addition to the division into two population groups with different shielding factors and breathing rates may be (1) the neglect of evacuation, (2) differences in population distributions, (3) differences in weather distribution. The complementary cumulative probability distributions for the whole body and thyroid population dose are presented in Fig. 5. Our estimates of late health effects are based on these population doses. The 'best estimate' in the BEIR(1972)report for the number of cancer deaths per

J. MIETTINEN, I. SAVOLAINEN,P. SILVENNOINEN,E. TORNIO and S. VUORI

494 t[[ 4 Z AI

g

II~7

~. lif e ,~ 10-910 t

10 2

10 3

10 4 10 5 10 6 N (number of people)

Fig. 4. Complementary cumulative probability distributions for early fatalities from reactor accidents BWR1BWR5. Linear whole body dose-response curves: (A) 200-500 rem; (B) 320-750 rein. In the curve B' 100% of the population belongs to the better shielded group. The curve RSS is from reference RSS (1975). Note: Approximate uncertainties are estimated to be represented by factors of 1/3 and 3 on consequence magnitudes and by factors of 1/5 and 5 on probabilities.

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g td 6 Whole

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Fig. 5. Complementary cumulative probability distributions for whole body and thyroid population doses from reactor accidents BWR1-BWR5. Note: Approximate uncertainties are estimated to be represented by factors of 1/3 and 3 on consequence magnitudes and by factors of 1/5 and 5 on probabilities.

106manrem (whole body) is 150-200 cases (lifetime plateau included). The same report estimates the number of genetic effects including dominant genetic diseases, congenital malignancies, recognized spontaneous abortions, and constitutional and degenerative diseases to 60-160 in the first generation and 90-800 in all generations per 106manrem (whole body). Radio-iodines are assumed to be less effective by a factor of ten to induce thyroid tumours than external X-rays. The risk estimates in references RSS (1975), BEIR (1972) and U N S C E A R (1972) give after weighting with dose factors of different age groups about 20 cases of nodules and 20 thyroid cancers per 106manrem (thyroid (adult), iodine). Further a 10% mortality for thyroid cancer is assumed. A conclusion of the estimated health effects caused by the release categories BWR1-BWR5 is presented at different probability levels in Table 3. To illustrate other environmental risks it is worth of mentioning that normally in Finland the different tumours are the cause of death in about 15,000 cases annually. 5. E C O N O M I C

LOSSES IN ACCIDENTS

The estimation of economic losses in accidents has been formulated similar to the estimation of health effects to the extent possible. Instead of dose-response relationships various contamination criteria have to be used and they are either surface concentration limits or limits for the integrated whole body dose within 30 yr. In this study the following modes of economic losses are considered: (1) losses of investments, (2) losses of production, (3) relocation costs, (4) costs of health effects and (5) losses related to the power plant. The investments are divided into four main groups: (1) agriculture and forestry, (2) manufacturing and construction, (3) service, (4) housing. The spatial distributions of investments (1-3) are assumed to be the same as the numbers of workers in the same fields. The housing investments are distributed in the same way as the total population. The investments are assumed to be lost as long as the whole body dose within 30 yr from the end of the interdiction period exceeds 10 rem. The lost fraction of the investments is assumed to increase linearly with the interdiction time until 10 yr, when the whole value is lost. The investments belonging to. manufacturing and construction and agriculture and forestry are assumed available for use, if people can stay in the pertinent area over 40 hr per

Risk-benefit evaluation of nuclear power plant siting

495

Table 3. Consequences of reactor accidents (BWR1-BWR5) for various probabilities in the case of the proposed Helsinki nuclear power plant

Effects estimated from the whole body population dose Chance per yr 1" 10-4 10-5 10-6 10-7 10-8 10-9

Early fatalities

Early illness

0.0002-0.0005 0.001-0.006 <1 <1 <1 < 10 50-200 500-1500 400-1000 3000-15,000 8 0 0 - 3 0 0 0 10,000--40,000 2000-6000 20,000-70,000

Manrem Cancerdeaths 15 -0.5 x 106 6× 106 15 × 106 25 × 106 34 x 106

Genetic effects First gen. All g e n .

Effects estimated from the thyroid population dose M a n r e m Cancerdeaths

0.002-0.003 0.001-0.003 0.0014-0.012 80-100 900-1200 2300-3000 4000-5000 5000--7000

30-80 50--400 4 0 0 - 1 0 0 0 500-5000 9 0 0 - 2 4 0 0 1400-12,000 1500-4000 2300-20,000 2000-5500 3000-30,000

500

0.001

5 )< 1 0 6 100x 106 600 x 106 900 × 106 900 x 106

10 200 1200 2000 2000

* Average per yr (expectation value). Note. The values are based on the curves in Figs. 2-4 and the uncertainty of these curves is not taken into account in this table. Table 4. The contamination criteria and unit costs for losses of investments

Investment

Number of hours Limit of whole per week in the body dose within contaminated area 30 yr (rem)

Housing Agriculture and forestry Manufacturing and construction Service

Time to lose Fraction of investments the total value remaining useful of investments Unit cost of loss (moving) % (yr) of investment

168

10

0

10

$1.70/day/inhabitant

40

10

30

10

$1.30/day/worker

40 168

10 10

30 30

10 10

$18/day/worker $4.40/day/worker

w e e k w i t h o u t e x c e e d i n g the dose limit m e n t i o n e d . F u r t h e r certain part of i n v e s t m e n t s is a s s u m e d to r e m a i n useful by m o v i n g e l s e w h e r e . T h e p a r a m e t e r values used in the e s t i m a t i o n of losses of investm e n t s are p r e s e n t e d in T a b l e 4. T h e value of p r o d u c t i o n is a s s u m e d to b e lost during the s a m e p e r i o d as the use of the corresp o n d i n g i n v e s t m e n t s is interdicted. T h e area w h e r e milk and crops are c o n t a m i n a t e d is larger t h a n the area d e t e r m i n e d by the criterion 10 r e m p e r 30 yr. In the d i s j o i n t e d area their values are a d d e d to the p r o d u c t i o n losses of agriculture and forestry. T h e c o n t a m i n a t i o n criteria and unit costs u s e d for p r o duction are p r e s e n t e d in Table 5.

T h e relocation of p e o p l e f r o m c o n t a m i n a t e d areas is a s s u m e d to be n e e d e d if the whole b o d y d o s e within 3 0 y r e x c e e d s 1 0 r e i n . T h e relocation costs consist of m o v i n g costs ( $ 2 5 0 / p e r s o n ) and loss of i n c o m e ($2500/worker). Costs related to possible evacuation during the early e x p o s u r e p h a s e are not t a k e n into account, but are b e l i e v e d to be small c o m p a r e d to the a b o v e m e n t i o n e d relocation costs. D e c o n t a m i n a t i o n costs have not b e e n e s t i m a t e d directly, but the e c o n o m i c d a m a g e s are calculated b o t h w i t h o u t any d e c o n t a m i n a t i o n and with a dec o n t a m i n a t i o n factor of 20. T h e actual total costs are b e t w e e n t h e s e two estimates and p r o b a b l y quite n e a r the value with d e c o n t a m i n a t i o n .

Table 5. The contamination criteria and unit costs for losses of production

All

Manufacturing and construction

Service

$13/day

$66/day

$37/day

Agriculture and forestry Milk Contamination criterion Value of production per worker

Thyroid dose 10rem/yr or 2/xCi/m 2 (I- 131 equiv.) $7.30/day

* Same as for losses of investments.

Corn Bone marrow dose 1.5 rem/yr or 2 ~Ci/m 2 (Sr-90 equiv.) $1240/crop (yr)

496

J. MIE'ITINEN,I. SAVOLAINEN,P. SILVENNOINEN,E. TORNIO and S. VUORI Table 6. Costs of health effects Health effect

Unit cost

Thyroid disturbances (medicine care 30 yr) Radiation illness (3 months in hospital and 3 months on leave) Fatalities

$1000/patient

II) 4 At

"" , .

$ 6000/patient

~Total

_~ id 6 $ 220,000/case

~.

~.. In the calculation of the costs of different health effects the unit costs used are shown in Table 6. The losses directly related to the power plant consist of the loss of investment and energy production. The value of investments is estimated to be $813 m and the value of energy production $2200 m ($5.2/MWhr, 3000MW(t), 20yr, capacity factor 0.8). The economic consequences of reactor accidents B W R 1 - B W R 3 in the case of the proposed Helsinki nuclear power plant are presented in Figs. 6 and 7. In the first figure no decontamination is assumed, whereas in the latter a decontamination factor of 20 has been used. In addition to the total costs the most significant components are presented as well. The total costs in Fig. 7 are in good agreement with the results of RSS (1975) taking into account the fact that only the three most severe BWR-release categories are considered. The inclusion of the ld 4

g 16 s

g

=

Relocation Investments ~ . . ~ . \

Health effects

oduction

/

\

io-a

tO-g10 6

10 7

101o 10I1 10 s 10 9 C (economic losses in dollars )

Fig. 7. Complementary cumulative probability distributions for total economic losses (outside the powel plant) and for the most significant components from reactor accidents BWR1-BWR3. Decontamination factor = 20. Note: Approximate uncertainties are estimated to be represented by factors of 1/3 and 3 on consequence magnitudes and by factors of 1/5 and 5 on probabilities. categories B W R 4 - 5 would somewhat increase the portion of smaller consequences. They have been omitted for the mere reason of the large computer running costs. When the total costs with and without decontamination are compared, one finds that in the case of large consequences the decontamination decreases the costs only by a factor of about three. The reason for this is that the most densely populated areas remain inside the interdiction area in spite of decontamination. 6. THERMAL POLLUTION

= I°1

~. I0-s10 0

Relocation Health e f f e c t s Investments

10 7

1010 1011 IO 8 10 9 C (economic losses in dollars)

Fig. 6. Complementary cumulative probability distributions for the total economic losses (outside the power plant) and for the most significant components from reactor accidents BWR1-BWR3. No decontamination. Note: Approximate uncertainties are estimated to be represented by factors of 1/3 and 3 on consequence magnitudes and by factors of 1/5 and 5 on probabilities.

The cooling water discharge from a power plant induces some changes in the composition of biological communities and in the ecosystem within the sea areas influenced by the increase of the temperature. To assess the extent of the area effected by the cooling water the circulation and mixing conditions were studied at the proposed reactor site carrying out measurements both on-site and with a miniature model. The experimental part was amended by theoretical calculations using streaming models. We regard these undertakings as necessary to gain as much experience as possible. The studies are of local character and therefore only a brief account of the results is given here. The on-site tracer measurements are appropriate

Risk-benefit evaluation of nuclear power plant siting for the study of the natural water circulation flow and mixing conditions. The sea area is not, however, in the realistic state resulting from the perturbation of the water inlet and outlet streaming. These perturbations can be simulated by the scale models which therefore are necessary as well. The miniature model is convenient in the design of the most appropriate discharge velocities, channel depths and arrangement for intake and outlet of the cooling water. The computational models are used to further confirm the experimental results and they facilitate the interpolation between a reliable map of the incremental temperature isotherms. In the case of the proposed site the experimental and computational studies show that the area affected by considerable increases in water temperatures is rather limited if both the arrangement of intake and outlet of the cooling water and discharge velocities are chosen properly. 7. POLLUTION OF THE ATMOSPHERE FROM A L T E R N A T I V E CONVENTIONAL PLANTS

The most significant environmental effects of the conventional power production arise from the pollution via atmospherical emuents, mainly sulphur dioxide, nitrogen dioxide, ash and hydrocarbons. Impacts on man concentrate in the respiratory system. Sulphur dioxide is converted into sulphuric acid, that may induce via inhalation respiratory diseases. Nitrogen dioxide diminishes the ability of lungs to clear themselves of micro-organisms which increases susceptibility to infections. Especially the fine-grained fraction of ash is deposited on lungs and may cause lung cancer. Hydrocarbons are known as carcinogenic materials. As a consequence of the physiology of the pulmonary system health effects arise often from synergistic effects between different air pollutants. Significant economic losses are occasioned by increased corrosion of property and by damages on plants, but these are not considered in this study. Many statistical results have shown a clear correlation between air pollution and health effects. The correlations are mostly presented as fatalities or cases of illness depending on the concentrations of air pollutants (e.g. sulphur dioxide and particulates) and the exposure time. Health effects of conventional power plants can be estimated by applying these mathematical relations to the observed or calculated concentrations of environmental pollutants. It must be assumed that there is no threshold value for the influence of the concerned pollutants or that the background pollution level due to other

497

Table 7. Alternatives of conventional power plants used in calculations 1

2

Sites Kopparn~s Vuosaari Suomenoja Martinlaakso Fuel Coal Coal Coal Oil Dist. and dir. from Helsinki city (kin) 41 SWW 12NEE 13 SWW 12NNW CapacityMW(e) 2 x 500 2x200 100 100 Stack height m 150 150 150 80 SO2-emission* t/yr 41,800 16,800 4200 7500 NO2-emission t/yr 17,000 10,800 2700 870 Ash-emissiont t/yr 3500 1400 350 8 * Without scrubbing. ? 99% scrubbingfor the coal plants and 90% for the oil plant. sources than the considered power plants already exceeds this threshold. This is analogous to the estimation of risks from the normal operation of nuclear plants. In this study health risks are estimated for two siting alternatives of conventional plants (Table 7) using the results of dispersion calculations carried out by the Finnish Meteorological Institute and the predicted population distribution for the year 1990. The calculated concentrations of pollutants are everywhere smaller than one tenth of the permitted levels. A population weighted integral (unit manpphm) of concentrations over the area surrounding the considered power plants is used as a measure of the pollution in analogy with the collective dose (in manrem) from radiation. Compared with the normal pollution (Table 8) the alternative 1 increases environmental pollution about 2% and the alternative 2 about 4.5%. The increase of fatalities entailing the alternative 1 is 0.006-0.04% and 0.01-0.07% in the alternative 2. The number of fatalities (in Table 8) are Table 8. Calculated annual pollution effects of alternatives and comparison with normal values 1

2

Person considered 1.16 × 106 0.97 × 106 Pollution: SO2 man-pphm 2.4 × 1 0 4 5.6 X 104 NO 2 man-pphm 1.6 x 104 -Ash (<10 p.m) man-/xm/m 3 3.0 × 1 0 4 -Health effects: Fatalities on diseases 0.5-3 1-6 Bronchitis diseases 130 300 Illness days 12000 2800

Normal value 106 1.2 X 106 0.7 × 106 2.5 X

10 7

8500 7000 6. l0 s

J. MIE'I~INEN, I. SAVOLAINEN, P. S1LVENNOINEN, E. TORNIO and S. VUORI

498

Table 9. Number of fuel transports for a 1000 MW(e) power plant per yr Fuel

Truck

Train

Sh~

Nudear* Coal Off

135 (133000) (75000)

42t 2680 1550

147 80 50

* Including fresh and spent fuel and low-level wastes of power plant, t Transportation capacity used partly (1 wagon or 200 tons (gr.wt) per ship). based on statistical results of Lindberg (1968), Starr (1972) and Lave (1973). The number of bronchitis is baseo on a Japanese result (Nishiwaki, 1971) and the amount of illness days on a Swedish result (EngstrSm, 1970). The same statistical correlations predict that the observed concentration level of pollutants from all sources is the cause of between 2 and 5% of the total number of deaths in the Helsinki region. 8. FUEL TRANSPORTATION RISKS

Fuel transportation is an essential stage in power production and thus the population risk occasioned by the transportation is a considerable contributor to the total risk. The nuclear fuel cycle contains many stages and distances between different plants are often long. The most hazardous materials to be shipped are: spent fuel, high-level waste from reprocessing and plutonium compounds (Proc. of the . . . . 1974). Table 9 gives estimates of the needed capacity in truck, train or ship transportations per 1000 MW(e) for a light-water reactor and for power plants using fossil fuel (coal or oil). The population risk involved in fuel transportation can be estimated by the number of fatalities in traffic accidents. Table 10 shows, for instance, that the transportation of coal by boat causes three times more fatalities than the transportation of nuclear fuel by train. In normal conditions no radioactive materials are released from the shipping cask. The population is Table 10. Number of traffic accidents and fatalities per 1000 MW(e)-yr in different power production alternatives (Hypothetic transportation distance back and forth: truck and train 2 x 200 km, ship 1/2 weeks) Accident

Nuclear

Ship accidents 0.001 Fatalities in accidents -0.001 Train accidents 0.3 Fatalities in accidents 0.003 Truck accidents 0.17 Fatalities in accidents 0.002

Coal

Oil

0.008 -0.008 18 0.17 170 1.7

0.005 ~0.005 10 0.10 100 1.0

normally exposed only to the gamma radiation penetrating the shipping cask, but the dose rate must not exceed very stringer t regulatory limits. The collective dose from norm 1 transportations of spent fuel by truck and train is 0.020.1 manrem/1000MW(e)-yr/100km, if a population density of 20 persons/km 2 is assumed. This is negligible compared to the collective dose induced by me natural background radiation (about 0.1 rem/yr/person). A traffic accident involves a certain possibility to the release of radioactive materials from the spent fuel shipping cask. Based on the release probabilities presented by Starr (1972) and in the papers of Proc. of t h e . . . (1974) and the traffic accident statistics of Finland the probability for major releases is 0.002-0.03/106km by truck, 0.0080.02/106 km by rail and 0.001/ship-yr by ship. Dispersion calculations carried out show that the radioactive dose due to the assumed release from a 4.5 MTU spent fuel shipping cask may be fatal only in an area which is at most 100 m long and 10 m broad. If we, however, assume that this kind of release always leads to one fatality, the yearly transports of a 1000 MW(e) plant bring 3 x 10 -54 × 10 -4 fatalities. Thus the possible radioactive release is an insignificant contributor to the total person-risk in traffic accidents during the transportation of spent ~uel. Releases of'cosven~tlonal fuel in accidents may be very detrimental especially in the case of oil leakages from tankers. According to the year 1970 statistics oil leakages into seas were 1600t/1000MW(e)-yr, of which 8 0 t arise from tanker accidents. The magnitude of detriments is difficult to evaluate, as they are mainly of ecological chare zter. Economic losses come from cleaning of oil soilings. Decontamination costs are $50015,000/ton of oil depending upon whether the leakage occurs out at sea or near the shore. 9. CONCLUSION Based on the detailed discussion of various risk and benefit components we wish to unify the treatment by employing compatible indicators which facilitate a comprehensive comparison. Concerning the economic benefits of the nuclear power Section 2 contains the explicit annual savings gained and these figures can be transferred directly to the final comparison. Recalling that economic results are extremely sensitive to variations in the accounting practice and interest rates we find it reasonably conservative to give the result for a real interest

499

Risk-benefit evaluation of nuclear power plant siting Table 11. Risk-benefit summary, 1000 MW(e) Annual excess mortality Plant Nuclear Conventional

Normal operation Fuel transportation 0.0001-0.08 2-5

0.003 (train) 0.008 (boat)

rate of ten per cent and amortization time of 20 yr. With these parameters the annual benefit on nuclear power is $9.1 m per GWe. The massive heat transmission investment of $181.8m is then already included in the nuclear power cost while no such item is contained in the expenditure of the conventional power production. For representation of diverse risks one should develop a compatible risk indicator. We have chosen the excess mortality as the risk indicator and consequently all the risks should be reduced to this level. The risk items that in our judgement can be relatively reliably expressed in terms of excess mortality are the following: radiation effects in normal operation of the nuclear power plant, hazards due to reactor accidents, atmospheric pollution from conventional power plants, and fuel transportation risks. The radiation mortality from normal operation and the delayed somatic injuries caused by accidents are computed by means of correlating the total population dose directly to excess mortality. The detailed discussion appears in Section 4. The immediate accident mortality was calculated on the basis of individual doses vs the percentage of death. The excess mortality ensuing from the pollutant releases from conventional plants is obtained from statistical correlations relating the total population pollutant concentration to mortality. Finally, the fuel transportation risks are calculated from the generated traffic density and unit transportation capacity. The tratfic accident deaths are the major contributor also in the transporation risk of radioactive materials. The risk-benefit analysis of the various items is summarized in Table 11. It is concluded that the nuclear power alternative simultaneously reduces excess mortality and yields economic benefit. The differential risk-benefit ratio is consequently negative and more favourable than - 0 . 2 2 deaths/$ m. The reactor accidents are described by the mathematical expectation value over the entire hazard spectrum. Due to the character of the hazard the final criteria should be based on (1) that the expectation value is below a certain limit and

Accidents

Annual benefit $m (10% 20yr)

0.005 --

9.1 --

(2) given a fixed probability the expected number of fatal injuries does not exceed the acceptable limit. Thermal pollution effects are omitted in our riskbenefit analysis. This is because negative (or positive) effects are assumed to be local and the absolute difference between the discharges from nuclear and conventional plants is marginal. We wish to point out that waste management problems are not related heavily to plant siting. However, the selected unit price of $175/kg U for reprocessing and waste management is thought to be high enough to tolerate a rather expensive mode of waste storage. The nuclear alternative discussed in this study is to be seen as a reference. If it can be shown to be favourable with respect to the most economic conventional alternative, which is the case in our example, the continuation of siting studies should be directed to the search of the best nuclear site. Placing the nuclear power plant closer to the urban area would reduce the heat transmission investment. Part of the saving could then be used to improved engineered safety at the plant. The pertinent risk-benefit study could then serve as the basis for selecting the actual nuclear site to be finally proposed.

Acknowledgement--The participation of the Finnish Meteorological Institute is gratefully acknowledged.

REFERENCES

Biological Effects of Ionizing Radiation (1972) National Academy of Sciences. Clarke, R. H. (1973) Hlth Phys. 25, 267. Engstr6m, S. (1970) Tekn. Tidskr. 1 ~ , 18, 22. Klug, W. (1969) Staub 29, 143. Lave, L. B. and Freeburg L. C. (1973) Nucl. Saf. 14, 409. Lindberg, W. (1968) R~ykskader&det, Oslo. Nishiwaki, Y., Tsunetoshi, Y., Shimizu, T., Ueda, M., Nakayama, N., Takahashi, H., Ichinoswa, A., Kajihara, S., Ohshino, A., Ogino, M. and Sakaki, K. (1970) Atmospheric contamination of. industrial areas including fossil-fuel power stations, and a method of evaluating

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J. MIETTINEN, I. SAVOLAINEN,P. SILVENNOINEN,E. TORNIO and S. VUORI

possible effects on inhabitants. IAEA-SM-146/16, 247. Proc. of the Int. Syrup. on Packaging and Transportation of Radioactive Materials (1974) CONF-740901 P1-P3, FL, U.S.A. Reactor Safety Study (1975) WASH-1400. Report on Releases of Radioactivity in Effluents and Solid Waste from Nuclear Power Plants for 1972 (1973) USAEC.

Smith, F. B. (1974) Atmospheric Diffusion. (Pasquill F. ed.) Wiley, New York. Starr, C. and Greenfield M. A. (1972), UCLA-ENG7242. Summary of Radioactivity Released in Effluents [rom Nuclear Power Plants during 1973 (1975) NUREG-75/001. The United Nations Scientific Committee on the Effects o[ Atomic Radiation to the General Assembly (1972).