Part 3

Other plankton research at Woods Hole uses radioactive carbon-14 and phosphorus-32 as tracers to evaluate rates of growth and nutrient assimilation by algae (floating green plants). These investigations have revealed that the presence or absence of minute quantities of nutrient minerals in seawater affects the rate at which the algae produce oxygen by the process of photosynthesis. Since the energy of all living things—including man—is also made available by photosynthesis, and since most of the photosynthesis on earth is performed by algae afloat in the oceans, it is apparent that this research is of more than academic interest. Algae, the original energy-fixers of the “meadows of the sea”, are also the original food source for the billions of aquatic animals, and may some day prove a source of food for a mushrooming human population.

In a project with more immediate application, extensive biological and environmental studies of the Eniwetok Atoll area in the Pacific were conducted prior to the first nuclear testing there in 1948, and these studies have continued ever since. Early in the test series the Japanese, who were at first concerned with the possible contamination of their traditional marine food supplies, were invited to participate in these studies. Fisheries radiological monitoring installations were established in Japan and the U. S. (The latter was established by the AEC and administered by the U. S. Food and Drug Administration.) Neither station encountered any radiological contamination of tuna or other food fish, and the American unit has now been closed.

Groups that have cooperated with the AEC in marine radiobiological research are the University of Hawaii, University of Connecticut, Virginia Fisheries Laboratory, University of Washington, U. S. Office of Naval Research, and U. S. Bureau of Commercial Fisheries.

At the Bureau of Commercial Fisheries Radiobiological Laboratory in Beaufort, North Carolina, a cooperative effort of the AEC and the BCF is concerned with learning the effects of radioactive wastes on one of America’s most valuable marine resources—the tidal marshlands and estuaries that are essential to the continued well-being of some of our important commercial fisheries.

Table III RADIOISOTOPES THAT MIGHT BE FOUND IN AN ESTUARINE ENVIRONMENT Isotope Half-life

Iodine-131 8.05 days Barium-140—Lanthanum-140 12.8 days—40 hours Cesium-141 32.5 days Ruthenium-103—Rhodium-103 10 days—57 minutes Zirconium-95—Niobium-95 65 Days—35 days, Zinc-65 245 days Cerium-144 285 days Manganese-54 314 days Ruthenium-106—Rhodium-106 1 year—30 seconds Cesium-137 30 years Potassium-40 1.3 × 10⁹ years

(Reprinted from _Radiobiological Laboratory Annual Report_, April, 1, 1964, page 50.)

The project has determined that radionuclides are removed from waters in an estuarine environment by several physical, chemical, and biological means. For example, radionuclides are absorbed in river-bed sediments at a rate varying directly with sediment particle size. Mollusks, such as clams, marsh mussels, oysters, and scallops, not only assimilate radionuclides selectively, but do so in sufficient quantity and with sufficient reliability to be useful as indicators of the quantity of the isotopes present. Clams and mussels are indicators for cerium-144 and ruthenium-106, scallops for manganese-54, and oysters for zinc-65 (most of which winds up in the oyster’s edible portions). It was learned that scallops assimilate more radioactivity than any other mollusk. Of the total radioactivity, manganese-54 accounts for 60%: The scallop’s kidney contains 100 times as much manganese-54 as any of the other tissues and 300 times as much as the muscle, the only part of the scallop usually eaten in this country.

In a surprising unintended result, it was determined that one acre of oyster beds, comprising 300,000 individual oysters, may filter out the radionuclides from approximately 10,000 cubic meters (18 cubic miles) of water per week!

The Radiological Laboratory scientists also have found that plankton are high concentrators of both chromium-51 and zinc-65, and that zinc apparently is an essential nutrient for all marine organisms. Some plants and animals appear to reach a peak of radionuclide accumulation quickly, which then tapers off even though the radiation concentration in the water is unchanged.

While the AEC’s oceanographic research budgets have not been large, they have contributed materially to knowledge of the oceanic environment. AEC-sponsored research at Scripps Institution of Oceanography has determined by a process known as neutron activation analysis[11] that the concentration of rare earth elements in Pacific Ocean waters appears to be only about one hundredth of the level previously reported. By analysis of naturally occurring radioisotopes, they have also discovered that it takes from one million to 100 million years for lithium, potassium, barium, strontium, and similar elements introduced into the ocean from rivers to be deposited in the bottom sediments. Aluminum, iron, and titanium are deposited in from 100 to 1000 years. They have also found that sedimentation occurs in the South Pacific at a rate of from 0.3 to 0.6 millimeter per thousand years, in the North Pacific at a rate several times that figure, and in the basins on either side of the Mid-Atlantic Ridge at a rate of several millimeters per thousand years.

The University of Miami has successfully developed two methods for determining the ages of successive layers of deep ocean sediments based on the relative abundances of natural radioelements, and thereby has established a chronology of climatic changes during the last 200,000 years during which the sediments were laid down.

The U. S. is not alone in its use of nuclear energy as a tool of science. The United Kingdom has carried out radiological studies of the marine environment for many years, particularly concentrating on the effects of radionuclides from nuclear power plants on the sea immediately contiguous to the British Isles. Both the European Atomic Energy Community and the International Atomic Energy Agency also encouraged marine radiological studies. Many laboratories and government agencies in Europe, North and South America, Africa, and the Middle East and Far East have well-established and productive programs under way.

Scientists in many parts of the world have used both natural and intentionally injected radiation to study the coastwise movement of beach materials. British experimenters, for example, activate sand with scandium-46 and are thus able to follow its movement for up to four months. Pebbles (shingle) coated with barium-140 and lanthanum-140 are also used as tracers and are good for 6 weeks. Scientists at the University of California trace naturally occurring radioisotopes of thorium, which may be introduced from deposits of thorium sands along river banks. These studies are of immediate practical importance, for each year the ocean moves billions of cubic yards of sand, gravel, shingle, and rock to and from beaches and along shores. This action destroys recreational beaches, fills channels, blocks off harbors, and in general rearranges the terrain, often at considerable cost and inconvenience to mariners and other people who use the coast.

In another use of radioisotopes in marine research, studies at the AEC’s Oak Ridge National Laboratory in Tennessee have revealed radioactivity in the scales of fish taken from waters affected by the laboratory’s radioactive waste effluent. It was suggested that this phenomenon might be put to use as a tagging technique in fish-migration studies, and scientists are now working on a method using cesium-134 introduced into the fishes’ natural diet.

Some of the most extensive studies of a marine environment ever conducted are those by the AEC, the Bureau of Commercial Fisheries, and the University of Washington in the Columbia River system and the nearby Pacific Ocean. Operations at the AEC’s giant Hanford facilities some 300 miles upstream from the ocean result in the release of small amounts of radioactivity to the river and also in raising the river-water temperature. This downstream research is to determine any effects of these changes, including any that might be detrimental to man. The research encompasses studies of the variations and distributions of the freshwater “plume”—the outflow from the rivermouth—extending into the nearby Pacific, sediment analyses, studies of the population dynamics of phytoplankton, and the transport of radionuclides through the food chain.

As so often happens with basic programs, this research has produced immediate benefits. New resources of marketable oceanic fish were discovered by the scientists at depths never before fished commercially (from the edge of the continental shelf to depths of 500 fathoms and greater). Similarly, commercial quantities of one species of crab have been discovered in the deeper ocean. Other findings indicate that crab populations may have seasonal up-and-down migrations that vary according to sex. It appears, in fact, that, except while mating and as juveniles, the male and female crab populations lead separate lives. This information is important both for more efficient fisheries and for improved conservation of the crab as a food resource.

The AEC is, in short, concerned with virtually every facet of basic oceanography, and with study of the sea as a whole, for radionuclides, like their nonradioactive counterparts, can and do become involved in every phase of the vast and complex ocean ecology. In the process of pursuing its research interests, it also provides oceanographers with a whole new family of tools for study. Let us now see how atomic instruments contribute to the growing knowledge of the sea.

Oceanographic Instruments

The ocean is both a complex and a harsh environment and its study has always demanded that designers of seaworthy instruments and sampling devices be both ingenious and experienced in shipboard requirements. Until recently, these devices tended to be rugged and simple, if not indeed crude. More refined, electronic instrumentation has begun to appear in recent years, but most designs still fail to pass the test of use at sea. Even among those that do pass, there is persistent difficulty in separating desired information-carrying signals from background and system-induced “noise”. This has been a specific problem with current meters designed to be moored in the open ocean and also with one quite sophisticated gamma-ray detector.

To meet the clear need for improved devices, as well as to support its own research and increase utilization of nuclear materials and techniques, the AEC Division of Isotopes Development encourages the development of oceanographic instrumentation. This comparatively young technology already has produced exciting results. The future may be even more revealing as nuclear energy is applied more and more to the study, exploration, and exploitation of the ocean.

Instruments that have been developed under the AEC program include a current meter, a dissolved-oxygen-content analyzer, and a sediment-density meter. A new, fast method for determining the mineral content of geological samples also has been perfected.

The DEEP WATER ISOTOPIC CURRENT ANALYZER (DWICA) was developed under a contract with William H. Johnson Laboratories, Inc. It relies on radioisotope drift time over a fixed course to measure seawater flow rates ranging from 0.002 to 10.0 knots. The device embodies 12 radiation sensors spaced equally in a circle around a radioisotope-injection nozzle. Current direction can be determined to within 15 degrees. The mass of tracer isotope injected is very small—less than 10 picograms[12] per injection—and the instrument can store enough tracer material to operate for a year. The tracer can be injected automatically at intervals from 2 to 20 minutes, depending on the current. The device sits on the sea floor, where its orientation to magnetic north can be determined within 2.5 degrees.

Isotope Reservoir and equipressure system Electric logic circuitry Pressure protective case Compass Sensor ring Flow baffle plate Isotope injection point

A SEDIMENT DENSITY PROBE, developed under an AEC contract by Lane-Wells Company, employs gamma-ray absorption and backscatter properties[13] to determine the density of the sediments at the bottom of lakes, rivers, or the ocean, without the necessity of returning a sediment sample to the surface. It is expected that it can be modified to sense the water content of the sediments. These determinations are valuable not only for research, but also for activity that requires structures on the ocean floor, such as petroleum exploration and naval operations.

The unit consists of a rocket-like tube 26 feet long and about 4 inches in diameter, containing a gamma-ray-emitting cesium-137 source, a lead shield, and a radiation detector. The device is lowered over the side of a ship and allowed to penetrate the sediment. Once in place, the gamma ray source, shield, and detector move together up and down, inside the probe, for a distance of 11 feet, stopping every 24 inches for 4 minutes to take a measurement. Gamma rays are absorbed in any material through which they pass, according to its density. A low radiation count at the detector indicates a high-density sediment: More radiation is absorbed and less is reflected back to the detector. Conversely, a high count indicates low density. Data are recorded on special cold-resistant film. A number of different sediment measurements can be made in several locations before the unit must be returned to the surface.

OXYGEN ANALYZER The amount of dissolved oxygen in any part of the ocean is a basic quantity that must be determined before some kinds of research can be undertaken. For example, oxygen concentration is important in determining the life-support capability of seawater and in measuring deep-water mixing. In the past this measurement has had to be determined by laborious chemical methods that may subject the water sample to contamination by exposure to atmospheric oxygen. Under an AEC contract, the Research Triangle Institute has developed a dissolved oxygen analyzer that relies on the quantitative oxidation by dissolved oxygen of thallium metal containing a known ratio of radioactive thallium-204.

The seawater sample passes through a column lined with thallium. The thallium is oxydized and goes into solution. It then passes between two facing pancake-shaped radiation counters that record the level of beta radiation from the thallium-204. Since the rate of oxidation, and therefore the rate of release of the thallium to solution, is proportional to the amount of dissolved oxygen in the water, it is simple to calibrate the device to show oxygen content. The system is sensitive enough to detect one part of oxygen in 10 billion of water. And, the device can be towed and take readings at depths of up to one mile, an added advantage that obviates the chances of surface-air contamination.

NEUTRON ACTIVATION ANALYSIS Nuclear energy is contributing to the more accurate and more rapid analysis of minerals in the sea in at least two different ways. The first employs neutron activation analysis, which we have already mentioned. This method is valuable not only in analyzing sediments cored from the ocean floor, but also in the detection and quantitative analysis of trace elements in the water. Knowledge of the role of all natural constituents in the ocean is essential to an understanding of the complex interrelationships of the ocean environment, as we have seen. Identification of trace elements also is a necessary preliminary to determining the effects of purposely introduced radionuclides. Collection of the minute quantities of trace elements is very difficult at best. Once they have been collected and concentrated, neutron activation analysis provides a means for their identification and measurement.

X-RAY FLUORESCENCE is another technique, used to identify the mineral content of ore or sediment. This system was developed (for the purpose of spotting gold being smuggled through Customs) by Tracerlab Division of Laboratory for Electronics, Inc. (LFE), under an AEC contract. Similar equipment was developed simultaneously in England for use by prospectors, geologists and mining engineers. It now may be used at sea in analyzing samples from the sea floor. As is often the case with isotope-based devices, its operation is really quite simple. When excited by radiation from an isotope (or any other radiation source), each element produces its own unique pattern of X-ray fluorescence, that is, it radiates characteristic X rays. By varying filters and measuring the count rate, oceanographers can detect and measure materials, such as tin, copper, lead, and zinc. The British unit is completely transistorized, battery powered, and weighs only 16.5 pounds.

RHODAMINE-B DYE The AEC also has improved oceanographic research in ways that do not involve the use of nuclear energy. Some years ago under the joint sponsorship of the AEC Division of Reactor Development and Technology and the Division of Biology and Medicine, the Waterlift Division of Cleveland Pneumatic Tool Company developed instrumentation and techniques for detecting the presence of the red dye, rhodamine-B, in concentrations as low as one-tenth part per billion. This method is now widely used both for groundwater studies and in the study of currents, diffusion, and pollution in rivers, lakes, and the ocean. In many cases, rhodamine-B is a better tracer in water than radioisotopes, due to the greater ease with which it is detected.

Environmental Safety Studies

The AEC Division of Reactor Development and Technology has supported extensive environmental studies to assess the safety of isotopic power sources (to be discussed later) in oceanic environments. One of the most important of these is being conducted by the Naval Radiological Defense Laboratory at an ocean environmental testing complex near San Clemente Island off the coast of California, which includes a shore installation and a floating ocean platform. These studies are to determine seawater corrosion of containment alloys and fuel solubility in seawater; the dispersion of the fuel in the ocean; the effect of the radioactive material on marine life; and the radiation hazard to man, when all significant exposure pathways are considered.

In another study the Chesapeake Bay Institute of Johns Hopkins University investigated potential hazards that might result if radioactive materials were released off the Atlantic Coast. Five areas along the Continental Shelf were examined in detail for environmental factors such as vertical diffusion. The same Institute made environmental and physical dispersion studies off Cape Kennedy, Florida, to predict the fate of any radioactive materials that might be released in aborted launchings of nuclear rockets or nuclear auxiliary power devices for space uses. Fluorescent dye was released into offshore, surf zone, and inshore locations; the diffusion was observed, sampled, and compared with existing diffusion theory. Mathematical models have been developed that can now be used to predict the rate and extent of diffusion in the Cape Kennedy area in the event of any radioactivity release from aborted test flights.

Similar studies have been carried out near the space launching site at Point Arguello, California, by the Scripps Institution of Oceanography. These included collection of data on dispersion, marine sediments, and the biological uptake of radioactive plutonium, polonium, cesium, and strontium.

The Atom at Work in the Sea

NUCLEAR REACTOR PROPULSION

The transformation in undersea warfare tactics and national defense strategy effected by the introduction of nuclear-powered submarines is now well known. Navy submarines employing the latest reactors and fuel elements can stay at sea for more than 3 years without refueling. _Polaris_ submarines on patrol remain submerged for 60 to 70 days. The nuclear submarine _Triton_, tracing Magellan’s route of 400 years earlier, traveled 36,000 miles under water, moving around the world in 83 days and 10 hours. Under-ice transits of the Arctic Ocean by nuclear submarines are now commonplace. These feats all are possible because of the nuclear reactors and propulsion systems developed by the AEC Division of Naval Reactors, which also developed the propulsion plants for the Navy’s nuclear surface vessels.[14]