For the past six years I have participated in a program whose purpose was the development of a practical ability to predict the distribution with­in the biosphere of each and every radionuclide produced in the explo­sion of a nuclear device. In particular, our program had the goal of estimating the ultimate dosage to man from the release of radionuclides to the biosphere as a result of the peaceful uses of nuclear energy. We now have a capability for estimating a defendable upper limit for the dosage (Burton & Pratt, 1968; Fisher, in preparation; Ng et al., 1968; Ng & Thompson, 1966; Tamplin, 1967; Tamplin et al., 1968). But before dis­cussing it, I shall explain why I believe that our approach or some similar approach should be applied to the effluents from nuclear reactors and fuel processing plants.

In the Code of Federal Regulations, Title 10, pages 134-144, is a table which lists the maximum permissible concentrations of various radionuclides in air and water released to an unrestricted area. The values listed there for 137Cs are 2 x 10~9 мСі/ml of air and 2 x 10-5 /хСі/ml of water. These levels are set so that a whole-body dosage of 0.5 rad/yr would result from breathing such air for one year or drinking some 2 liters of water per day. But more important is what such levels really mean in terms of what could occur as a consequence of such levels in an unre­stricted area.

The 137Cs in the air will be deposited on pasture plants, which will be eaten by cows and secreted in their milk; the milk will subsequently be consumed by children. If the 137Cs concentration in air were maintained at the maximum permissible concentration (mpc) for just one day, a child consuming 1 liter of milk per day would get a whole-body dose of

7 rad as a consequence of just one day’s deposition. If mpc in air were maintained for one year, the dose would be 2,555 rad — 5,110 times higher than the 0.5 guideline of the aec and 15,000 times the radiation pro­tection guideline of the U. S. Federal Radiation Council (frc) (1960).

The above-dose estimate is derived as follows: The mpc for 137Cs in air is 2 x 10-9 ju, Ci/ml. This is equivalent to 2 x 10~3 мСі/m3. If this concentration existed for 24 hr, the integrated air concentration would be 48 X 10~3 juCi-hr/ms. Now the 1STCs would be deposited on forage at a rate of 17 m/hr (Fisher, 1966). The deposition would thus be:

■I48 X 10-3[(/iCi-hr)/m3]}- j 1т/Ы = 0.82(^Ci/m2)

A deposit of 0.12 /лСі/т2 would lead to a whole-body dose of 1 rad to a 10-kg child consuming 1 liter of milk per day (Ng et al., 1968; Ng & Thompson, 1966). Therefore, the 0.82 juCi/m2 would lead to a dose of 7 rad.

As for the concentration in water, the mpc is based upon the calcu­lation that a 150-lb average man consuming 2,200 g of water at the mpc per day would receive a dose of 0.5 rad. To begin with, a 75-lb child drink­ing this much water would get a dosage twice as high. He would be ex­ceeding the guideline dosage, and so would a 100-lb pregnant woman. Man, woman, and child have also been known to eat fish. The concen­tration of 137Cs in fish flesh, caught in a river, would be 1,000 times higher than the concentration in the water (Chapman et al., 1968; Ng et al., 1968). Thus a man eating a pound of fish a week, grown in water at the mpc, would receive a dosage of 15 rad/yr —30 times the aec guideline and 90 times the frc guideline. If he were a 75-lb child, the dosage would be 60 times the aec guideline and 180 times the frc guideline. In other words, most people would exceed the guidelines if they ate only one pound of fish a year.

The milk and fish represent biological concentration mechanisms. They, by themselves, serve to demonstrate quite conclusively that using air and water mpc values without considering food chains is meaning­less. Still another example can be found in a physical process. If the mpc of 137Cs in air were maintained for one year, the resultant deposition on the ground would be 300 ju, Ci/m2. Since 13 ^Ci/m2 is equivalent to an external radiation dose rate of 1 rad per year (Dunning, 1963), the radiation level from these 300 pCi/m2 would be 23 rad per year. In other words, even if the air concentration were a hundredfold less than the mpc, the radiation levels would exceed the frc guideline. The mpc’s are mean­ingless.

Now, it is often stated that the reactor discharges are kept to a small fraction of the mpc’s. The above analysis indicates that they should be kept to a very small fraction of the mpc’s. What fraction the engineers are using as a design criterion is a critical question.

The mpc values in air and water are of no use to the scientific com­munity in assessing the potential hazard to man from nuclear reactors and consequently are of no use to the engineers who are designing re­actors. In fact, the mpc values lead to an unacceptable risk estimate. What is needed for assessing the hazard is the quantity (the number of curies) of each and every radionuclide that is released to the environment. Armed with such information, we can proceed to estimating the distribution of these radionuclides within the biosphere and to estimating the resultant dosage to various organisms and to man. We can then estimate the po­tential damage to the biosphere and to man. I don’t mean that an abso­lute or accurate estimate can be made. There are too many uncertainties for this. Nevertheless, these uncertainties can be treated in a manner that is weighted toward the protection of public health and safety. The risk estimate that evolves from such an analysis is a defendable upper limit of the risk. On a scientifically valid basis, one can state that the risk can be no larger than this defendable upper limit. Any lower risk estimate is a matter of opinion. In this respect, it is important to recognize that scien­tific opinion is generally no more valid than other forms of opinion.

To illustrate how a defendable upper-limit estimate of the risk can be made, I shall describe our estimate of the dosage to and effect on man from the yearly release to a hypothetical stretch of river on an amount of fission products that would be produced in one hour from the operation of a 500-megawatt (thermal) nuclear power reactor. This stretch of river is 200 km (a little over 100 miles) long, 200 m (about 1,000 ft) wide, and 10 m (about 30 ft) deep. It therefore has a volume of 600 million cubic meters. Assume that this water is replaced each day —that is, the water flows at about 5 miles per hour. Assume also that there are 5 gm/cm2 of bottom material in equilibrium with the water. This is about the first inch. Finally, the population of the surrounding countryside exists totally on a diet of aquatic origin that is derived from the river. The details of the calculations are described in Parts IV and V (Ng et al., 1968; Tamplin et al., 1968) of the UCRL-50163 series of reports (Burton & Pratt, 1968; Fisher, in preparation; Ng et al., 1968; Ng & Thompson, 1966; Tamplin, 1967; Tamplin et al., 1968). Here I shall simply show the results and discuss their implication.

The accompanying tabulation presents the dosage estimate for the whole body over the period from conception to 30 years of age under these assumptions; this dosage would be accumulated from a yearly release to the hypothetical river of the fission products produced in 1 hour in a 500-megawatt (thermal) reactor.

Radionuclide rad

шСе…………………………………. 48

106Ru………………………………… 40

^Sb ……………………………………. 8

147Pm…………………………………. 6

“7Cs………………………………….. 1

14SCe…………………………. 6 x lO’15

Total………………………………. 105

The contribution from the most significant radionuclides (half-life >180 days) is included in addition to the total. There are a number of other radionuclides between 1S7Cs and 142Ce; 142Ce indicates the range over which the individual nuclides contribute to the dosage. As you can see, the total dosage estimate is 105 rad. If one assumes that only 1 per cent of the diet comes from the river, the dosage would be lower by a factor of 100 or 1.0 rad. This is one-fifth of the radiation protection guide­line of the FRC.

The dosage estimate shown in the tabulation is dependent upon the assumptions relating to the diet and the hypothetical river. It is also an upper-limit number. When some of the uncertainties in the biological data are resolved, when the appropriate dietary mix is considered, and when the values for an actual river are used, this upper-limit estimate may be lowered by a factor of 1,000. If this happens, the upper-limit dosage estimate would be a factor of 50 less than the present radiation protection guideline.

But even if we achieved this factor of 1,000, we should not be lulled into complacency. The release rate used in these estimates represents only a few hundredths of 1 per cent of the radionuclide inventory at the end of a single year’s operation of one 500-megawatt nuclear power plant (Division of Radiological Health, Public Health Service, 1966). In other words, this dosage estimate results from essentially complete containment (about 99.99 per cent) of the radioactivity within the power plant. If more than one reactor is planned for the river, the margin for error gets smaller. If we are going to live within the radiation protection guidelines with nuclear power plants, we had better take a very hard look at the permissible levels of release to the environment. At this point, it appears that something approaching absolute containment of the radioactivity is required.

Because of the assumptions involved in the calculations, the fore­going dosage estimates should not be taken at face value. My purpose here was to demonstrate that it is entirely possible to make such estimates of the dosage and to show that it is absolutely essential that such estimates be made to assure that the radiation protection guidelines are not ex­ceeded.

But even the frc suggests that dosage should be kept as far below this guideline as is possible. How far below the radiation protection guide­lines the dosage should be kept depends upon the risk that the population is willing to accept. The risk depends upon the biological effects of low dosage, low dose rate irradiation. Again, a precise estimate of the risk cannot be made, but it is possible to present a defendable upper limit for the risk. One approach to estimating an upper limit to the effects of radia­tion would be to assume that all of the fetal and infant deaths are a con­sequence of mutations occurring in the population. By this assumption, if the mutation frequency were doubled, these death rates would be doubled. This is not an unreasonable assumption. In the United States some 20 to 25 per cent of the conceptions terminate as fetal or early infant deaths, so it is apparent that this represents the most severe selection process imposed on the population. Exclusive of those deaths that result from chromosomal anomalies, some 15-20 per cent of the conceptions terminate as fetal or early infant deaths. This percentage is close to the mutation frequency estimated for the population (14/100 germ cells/ generation) (United Nations Scientific Committee on the Effects of Atomic Radiation, 1966). Since this number of mutations is being eliminated with each generation, the correspondence of these percentages suggests that the above assumption is not unreasonable.

The United Nations Scientific Committee on the Effects of Atomic Radiation (1966) estimates that 1 rad would increase the natural muta­tion frequency by a factor between.10 and.01. The existing radiation protection guidelines would allow a genetically significant dosage of 5 rad. This could increase the mutation frequency and hence increase the fetal and infant death rates between 5 and 50 per cent. As an upper limit then, the radiation protection guideline dosage could increase the fetal and infant death rates by 50 per cent. However, experiments on mice suggest that radiation delivered at low dose rates might produce only one — fifth as many mutations. As a consequence, the upper-limit estimates could be high by a factor of 5, and this would reduce the estimate to between 1 and 10 per cent. Considering that each year we have some 150,000 late-term fetal and infant deaths combined, even 1 per cent represents considerable human tragedy. Certainly, the dosages should be kept as far below the radiation protection guideline as is possible.

In summary, as a member of the scientific community and as a member of the public at large, I view the burgeoning nuclear power in­

dustry with a great deal of anxiety. My impression is that these power plants should be designed so as to approach absolute containment of the radioactivity. My anxiety is only increased when I consider that the only recorded regulations are a set of numbers called mpc’s for air and water that are tabulated in Title 10 of the Code of Federal Regulations. What is needed is a comprehensive study that takes into account both physical and biological concentrating mechanisms and is based upon quantitative data on each and every radionuclide in the inventory of the total nuclear power industry that is anticipated for the future in each ecological region of the nation. Following this study, it would be possible to determine whether something other than a very close approach to absolute contain­ment of the radioactivity is acceptable.

As the situation stands, aside from the bland reassurances of spokes­men for the Atomic Energy Commission and the nuclear power industry, there is no reason to assume that nuclear reactors will not jeopardize the public health and safety.

Abstract

The effects of heated water on aquatic biota are diverse and vary from the dramatic to the subtle. In general, these may be categorized into direct and indirect effects. Examples of the former would be lethality, reduction in reproduction, and alterations in the number and types of species normally present in a particular environment. Indirect effects could be significant increases in the oxygen demand of a water, increase in disease virulency, or increases in the toxicity of other pollutants. Attempts to improve water quality criteria for temperature have pre­sented several interesting considerations to supplement the anti-degra­dation policy of the Federal Water Pollution Control Administration.