The Control of Exposure of the Public to Ionizing Radiation

Above: The Control of Exposure of the Public to Ionizing Radiation in the Event of Accident or Attack, Proceedings of a Symposium Sponsored by the National Council on Radiation Protection and Measurements (NCRP), April 27-29, 1981, Held at the International Conference Center, Reston, Virginia. (The proceedings were published on May 15, 1982, by the U.S. National Council on Radiation Protection and Measurements, Bethesda, Md.) The NCRP was chartered by U.S. Congress in 1964 to analyze and publish information on radiation protection issues.


In several previous posts quotations are made from Dr Carl F. Miller's enlightening acceptance speech for an award (published beginning on page 99), which give a first-hand idea of the awesome task of obtaining the vital early-time data on arrival and deposit characteristics of fallout during the 1950s American atmospheric nuclear test series in the Pacific and also at the Nevada test site. Dr Miller's 60 rads gamma dose more than doubled his natural leukemia risk from 0.5% to over 1%, and he tragically died from leukemia in August 1981. A longer excerpt from the Session B Discussion text is as follows, and illuminates the whole subject very clearly:

'Mr Greene [Jack C. Greene, Moderator]: 'As all should know, much of the work that Jim Sartor described [in a summary of decontamination data] was done under the very able direction of Dr Carl Miller who is with us today and will join the panel.

'Carl, I am very pleased to use this occasion to present to you a "certificate of appreciation" from the Planning Committee for this symposium, joined by members of the former NAS Advisory Committee on Civil Defense and others who have worked with you over the years. Here's what the certificate says:

'We hereby present a Certificate of Appreciation to Carl F. Miller. Dr Miller's many years of dedicated research have combined the best of theoretical and applied work and have resulted in an unparalleled contribution to our understanding of the physical and chemical characteristics of radioactive fallout, as well as the means for protecting against it. It is specially meaningful to those of us who have known and admired Carl over the years to have an opportunity to publicly acknowledge and honor the work of this extraordinary, versatile and innovative scientist.'

'We will start the discussion period by giving Carl five minutes to comment on anything he chooses.

'Dr Miller: Thank you very much. I appreciate this commendation and your comments. I might add here that thanks should also be given to my co-workers who helped me and did most of the hard work - this includes, of course, Pete [Peter O. Strom of Sandia National Laboratories] and Jim [James D. Sartor of Woodward-Clyde Consultants] who just completed their presentations. Sitting here and listening, I was impressed with many of the talks that were given. Starting with Lew Spencer's, I think he did a very good job in giving the outline for the hazards to be discussed. One thing that occurred to me and probably occurs to a lot of you is that the real hazards in a nuclear attack are not from radiation - the real hazards are in the blast and other initial effects. Though his paper was clearly limited to the radiation effects, he knows, and you know, that the countermeasures against the other hazards would be more difficult to achieve.

'Someone talked a little about risks. One thing that usually comes to my mind when risks are discussed goes back to World War II when I was in Burma working with the Chinese Fifth Army as an artillery-man. We (and they) used to be supplied by airplanes that would fly over and parachute-drop food and ammunition and so forth. The thing about risk was that we used to watch the behavior of the Chinese soldiers - they would make bets on who could catch a sack of peanuts dropping down and they would truly try. I don't know what the LD50 for that "exposure" was or might be, but it was exceedingly high for a good catcher. It was a high risk game in a rather high risk environment. However, in the (now) old days, some of us at the then existing U.S. Naval Radiological Defense Laboratory did about the same thing with fallout at nuclear weapons tests.

'In 1954, some civilians and Navy men were on a specially outfitted ship - a monstrosity bedecked with all kinds of sprinklers for testing the Navy washdown system [i.e., the continuous spraying of decks by fire sprinklers, to flush fallout off the deck as it landed]. On one test, we were about 20 miles away when a 10-megaton shot was detonated. At the time, one piece of data we were interested in obtaining was the early time decay; also, additional data on the characteristics of the fallout were desired. My job was to put out a series of funnels, tubes, and other things on this ship to collect some of the fallout. The ship was sailed on a pathway that led to an area directly underneath the expanding cloud so as to be exposed to a maximum amount of fallout. The ship, called the YAG-39, was highly instrumented with gamma detectors; it was accompanied by a sister ship, the YAG-40, which was operated by remote control but without the washdown system. Fallout arrived about 20 minutes after detonation, at which time I collected the first few drops of "hot" washdown water from tubing that extended from the deck to the bottom of the ship across from where the radioactive assay equipment was located.

'In 1957, at the Nevada Test Site, personnel from NRDL and the AEC sat in an underground shelter a mile away when Shot Diablo was detonated. Some of us collected fallout particles as they fell out of the sky from this event. We didn't chase after them on the outside of the shelter because we had little funnels and tubes running to the outside from inside. One could hear that stuff trickle down into containers in a deep cave from which we picked out single particles for assay. I was trying to do gamma spectrometry on particles. I picked up one little particle, and the spectrometer just about blew up, so I quickly put it back and got a smaller one. That didn't work either: it was too hot. Finally, I got a teeny one, but it was still too hot. So I took it back in and smashed it into smaller pieces, picked up a chip with tweezers and found out it didn't blank out the spectrometer. Of course, after about a half-hour or so, one could hardly get a reading on it anymore, because of the rapid decay rate. Many people received some gamma exposure on ventures such as these. I did as well. ...

'I like the way Jim Sartor brought out the character of the fallout, and Pete Strom, too. With most of the local fallout that we're talking about, a lot of the larger particles are fused or melted to form little glassy marbles. The tower shots had iron in them so they were magnetic and we could separate hot fallout particles from tower shots with magnetism. The radioactive atoms that could be absorbed into, or by, body organs were the few that plated out on the surface of the fallout particles during the later stages of condensation in the fireball. That's why the elements iodine, strontium, ruthenium and a few other isotopes of that nature have been found in organs of animals and humans.'

Above: this is a summary of the decontamination data tables presented by James Sartor which Dr Miller was commenting on. This type of empirical field information is vital for informed decision making about how best to deal with a nuclear fallout disaster of any kind, be it an accident or a weapon attack.

The volume also contains other information of background importance. Dr Clarence Lushbaugh goes through the history of the LD50, i.e., the estimated dose which kills 50% of exposed people. He reveals that even before the bombs fell on Hiroshima and Nagasaki, the Manhattan Project had determined a figure of 500 +/- 100 R as the human LD50, based on extrapolations from animal data, and shows that the commonly quoted 450 R estimate of the LD50 stems not directly from any particular analysis of evidence, but instead from an average of the guesses made by 24 consultants to the U.S. Armed Forces Special Weapons Project who met at San Francisco in 1947 under the chairmanship of Dr R. R. Newell. (This 450 R human LD50 estimate was first published in 1950 by S. Warren and J. Z. Bowers in "Acute Radiation Syndrome in Man," Ann. Int. Med., v32, pp207-16.)

Dr Lushbaugh also comments on the disagreement which occurred in 1959, when Dr Payne Harris testified before the U.S. Joint Committee on Atomic Energy that the human LD50 was 700 R +/- 25%, based on Oak Ridge and Yugoslavian accident data, while Drs Cronkite and Bond testified using Marshallese evidence plus dog and swine data that the human LD50 was 350 R. As a result of this disagreement (one estimate above the previous LD50 estimate of 450 R, and the other estimate below that figure), the 450 R estimate continued to be used as the best available consensus. Lushbaugh however notes that he and Dr Auxier, using the best available data for shielding by buildings in Japan and the best empirical estimates of the radiation doses (confirmed by measurements of neutron induced activity in Hiroshima and Nagasaki, with thermoluminescent data which allow measurement gamma ray doses in roof tiles at various distances because some radiation energy is transferred to the ceramic as energy trapped in the crystalline structure, which is released as light when the material is subsequently heated), found an LD50 estimate of 260 REM, assuming a relative biological effectiveness (RBE) factor of 2 for neutrons. (REM = exposure in roentgens multiplied by RBE.) Lushbaugh comments that this low figure of the LD50 from Hiroshima and Nagasaki data is due to the blast and burn trauma the people took from the shock wave and thermal radiation which accompanied the nuclear radiation. (C. C. Lushbaugh and J. Auxier, "Reestimation of Human LD50 Radiation Levels at Hiroshima and Nagasaki", Radiation Research, v39, p526, 1969.)

He reports another study of Hiroshima and Nagasaki effects which found that a 50% incidence of epilation (hair loss) occurred at a dose of 310 REM if the neutron RBE is 4, and 50% incidence of hemorrhage (i.e., platelet suppression in blood due to irradiation of the bone marrow where blood cells are produced; the reduction in the platelet count causes small vessels to leak, producing small but visible skin hemorrhages below the outer skin layer). Some of these data will be obsolete now because they were based on the 1965 dosimetry of Hiroshima and Nagasaki, which has been updated with improved radiation transport models (although the 'improved" estimates of the yields of the Hiroshima and Nagasaki bombs may be a step backward, because the yields depend on random chances of the time of initiation of the chair reaction after fissile assembly, and other chance factors, and so should be evaluated from the actual measured blast effects data like the crushing of petrol tins and the overturning of stone slabs of known mass, as Penney did in his 1970 report, not on computer simulations of bomb dynamics).

Lushbaugh also discusses the effects of protracted exposure, where the body can repair some of the damage if the radiation is received at a low dose rate. A man accidentally irradiated by a Co-60 radiotherapy source in Mexico in 1964 for 106 days at a gamma exposure rate of 9-16 R/day (total dose 980-1,700 R) was still alive 17 years later, but four others who suffered daily exposure rates as least twice that amount were all killed within 80 days due to suppressed blood cell counts, hemorrhages and infections accompanying the reduced white blood cell count.

Another interesting item in the report is the table of neutron induced activities due in soils on different bedrocks (igneous, shale, sandstone, limestone and sediment) as part of Dr Peter Strom's paper on page 81. This shows that the initial beta Al-28 radioactivity induced in soil is on the order of 1,000 times as intense as that of Na-24. This is partly due to the higher typical abundance of aluminium than sodium in most soils, but is mainly due to the shorter half life of Al-28 (2.3 minutes, contrasted to 15 hours for Na-24). The faster something decays, the more intense the decay rate (decays/second, i.e., Becquerels) during its decay.

The typical igneous rock sample (at least half silicon dioxide, by mass) initially (i.e., at zero time) would give an beta activity from neutron induced Al-28 which is 550 times that from Na-24. After an hour (26 half lives of Al-28, but only 1/15th of a half life of Na-24) the ratio is only 0.0000088. Hence, despite the initial higher radiation levels from Al-28, it is always trivial within a fraction about half an hour of a nuclear explosion, as compared to other nuclides.

There are two interesting appendices in the volume. The first is by Philip J. Dolan of SRI International and is entitled Appendix A: Characteristics of the Nuclear Radiation Environment Produced by Several Types of Disasters, Summary Volume. On page 264, Dolan comments that:

'The hypothetical attack selected for use is a strategic attack on U.S. military installations, military supporting industrial and logistics facilities, other basic industries, and major population centers.

'The attack consists of 1,444 weapons with a total of 6,559 megatons, of which 5,051 weapons are surface burst. ...

'More than 67 million persons are located in areas receiving unit-time [1 hour reference time, although fallout is obviously not deposited everywhere within 1 hour of detonation so these unit-time figures are gross exaggerations if applied to distances of several hours downwind] reference dose rates in excess of 3,000 R/hr, more than 159 million in areas receiving in excess of 300 R/hr, and more than 188 million in areas in excess of 30 R/hr.

'The dose rates mentioned above would not necessarily exist since the deposition would take place over an extended time period and the fallout is decaying while deposition takes place. The four-day doses, which consider arrival time and which represent most of the lifetime accumulations, corresponding to the above-mentioned unit-time dose rates are 5,400, 360, and 24 roentgens, respectively. Shielding or relocation could reduce these accumulated doses.'

On page 265, Dolan adds:

'The four major ways to reduce adverse effects of fallout are: shelter, relocation, decontamination, and minimization of ingestion and inhalation ...

'The effectiveness of shelters usually is described in terms of a protective factor (PF), which is the ratio of the dose rate that would be measured 3 feet above an (imaginary) infinite smooth plane to the dose rate expected inside the shelter (accounting for surroundings as well as protection afforded by the shelter). About 20 percent of the urban population and 19 percent of the rural population of the U.S. could be afforded a PF of 1,000 or more (subways, mines, caves, and some basements) without evacuation, while about 75 percent of the urban population and 43 percent of the rural population could be afforded PF's of 100 or greater. ...

'The consequences of a multiweapon nuclear attack would certainly be grave, but exact numbers have large uncertainties. Estimates of 20 to 160 million short term fatalities have been made, with the majority of the survivors receiving doses from >10 to a few hundred rem. Nevertheless, recovery should be possible if plans exist and are carried out to restore social order and to mitigate the economic disruption.'

Commenting on the uranium and plutonium hazards of nuclear weapon accidents on page 272, Dolan states:

'Uranium taken internally represents a heavy-metal poison hazard in quantities less than those required to be a radiation hazard.

'Less than 10^{-4} of the plutonium eaten by man is absorbed from the intestine. Inhalation is a more probable route of deposition, but once the cloud has passed, inhalation requires that the plutonium be resuspended. This is an inefficient process.

'"Soluble" plutonium may be cleared from the lung within a year or so and will be translocated primarily to bone and liver. "Insoluble" plutonium will be retained much longer in the lung and will be translocated principally to lymph nodes. Plutonium dispersed in a weapon accident is expected to be in the form of insoluble oxides.

'Two accidents of this type are recorded. ... The first occurred near Palomares, Spain on January 17, 1966. A B-52 collided in flight with a tanker during a refueling operation, and 4 weapons were dropped. One weapon was found on the beach undamaged, and one was recovered intact from the sea at a much later date. The other 2 weapons resulted in high explosive detonations on impact with the earth. The resulting contamination covered about 650 acres with a concentration of about 5 micrograms per square metre or more.

'The second accident occurred near Thule, Greenland on January 21, 1968. A B-52 crashed on an ice floe just off the coast. Snow was falling at the time of the accident, and the precipitation increased after the accident. Most of the plutonium sank with the aircraft debris, and the rest was trapped under the snow and the ice. ... The worst consequence of such an accident is likely to be a partial denial of the use of a relatively small area.'

The second appendix is by Dr Alvin M. Weinberg, Appendix B: Civil Defense and Nuclear Energy, pages 275-7:

'The rejection of nuclear energy has been catalyzed by the articulate and influential energy radicals in the Western world. ... I continue to believe, and preach, the obvious: that defensive systems are less threatening than offensive systems: 100 million Americans can't be killed with Russian ABM's or civil defense ... Escalation of defense is not nearly as threatening as is escalation of offense. ... The ultimate issue is not how many people are going to be killed in a nuclear war: it is how can we both maintain our freedoms and avoid nuclear war. ...

'Nuclear power is an instrument of peace because it reduces pressure on oil. The energy crisis is primarily a crisis of liquid fuels. Insofar as nuclear power can replace oil, it helps stabilize the world order.

'The world today uses about 60 million barrels of oil per day; of that, about 18 million barrels per day came through the Straits of Hormuz before the Iran/Iraq war. A nuclear reactor of 1,000 megawatts electric output uses the equivalent of about 25,000 barrels of residual oil per day. If the world had 1,000 reactors operating now, the primary energy supplied by uraniu to those 1,000 reactors would exceed 18 million barrels of oil per day that go through the Straits of Hormuz. To be sure, the substitution is not direct, since what would be displaced is residual oil, not gasoline or other higher distillates. But with an expenditure of about $10-15 thousand per daily barrel of capital equipment, refineries could convert the residual oil into higher distillates [i.e., break the longer hydrocarbon molecules into smaller ones]. So to speak, residual oil, made available by conversion from oil-fired to nuclear power plants, is the best feedstock for a synthetic fuel plant. To make high distillates from coal requires an expenditure of about $100,000 per daily barrel. To make high distillates from residual oil takes only about one tenth as much. ...

'This simple-minded argument cannot be ignored: substitution of nuclear energy for oil reduces the pressure on oil and therefore reduces the political pressures that lead first to political instability, then to war, and possibly eventually to nuclear war. We forget that the immediate cause of the Japanese attack on Pearl Harbor was the decision by the United States to prevent Japan from moving into Indonesia to get oil. The Japanese entry into World War II demonstrated how oil can trigger a world conflagration. ...

'I do not know whether nuclear energy, which is now in a state of moratorium [following Three Mile Island controversy in 1979], will get started again. ... That people will eventually acquire more sensible attitudes towards low level radiation is suggested by an analogy, pointed out by William Clark, between our fear of very low levels of radiation insult and of witches. In the fifteenth and sixteenth centuries, people knew that their children were dying and their cattle were getting sick because witches were casting spells on them. During these centuries no fewer than 500,000 witches were burned at the stake. Since the witches were causing the trouble, if you burn the witches, then the trouble will disappear. Of course, one could never be really sure that the witches were causing the trouble. Indeed, though many witches were killed, the troubles remained. The answer was not to stop killing the witches - the answer was: kill more witches. ...

'I want to end on a happy note. The Inquisitor of the south of Spain, Alonzo Frias, in 1610 decided that he ought to appoint a committee to examine the connection between witches and all these bad things that were happening. The committee could find no real correlation ... So the Inquisitor decided to make illegal the use of torture to extract a confession from a witch. ...

'I don't know whether the modern witch - low level radiation and the hysteria that is exhibited about nuclear energy - will be resolved soon enough for nuclear energy to play a proper part in avoiding the oil confrontation. After all, it took 200 years for the Inquisition to run its course on witches. I only hope that our attitude towards nuclear energy will become more sensible long before 200 years have gone by. The possible alternative - nuclear war sparked by competition for dwindling oil - is far too horrible to accept, whether or not we have civil defense.'