Jan Rydberg

SISAK—A new technique for rapid, continuous (radio)chemical separations

SISAK, a new continuous technique for on-line chemical separation of short-lived species, is presented. The system features multistage two-phase liquid-liquid and liquid-solid separations completed within 3–5 sec per stage. The system is easily adaptable for selective isolation of almost all elements. The operational characteristics of the system are outlined and the delay properties briefly discussed. A two-detector delay method for half-life determinations is also presented. The application of the technique to the study of short-lived nuclides is exemplified by results from investigations of 30 sec 68gCu, 3·8 min 68mCu and 42 sec 70Cu.

An improved system for fast, continuous chemical separations (“SISAK 2”) in nuclear spectroscopic studies

Abstract An improved rapid, continuous solvent extraction system (“SISAK 2”) is described. The system is connected to a gas-jet installed at the Mainz reactor. It allows single or multistage chemical separations of liquid phases by means of specially designed centrifuges within ∼1 s per stage. The application of this system to study short-lived nuclides is exemplified for neutron-rich lanthanum and cerium isotopes produced by fission.

Reducing the Long-Term Hazard of Reactor Waste Through Actinide Removal and Destruction in Nuclear Reactors

Abstract Public opposition to nuclear power has focused on the long-term risks from reactor waste. In the Purex process used in Europe, this waste is a concentrated nitric acid solution containing all nonvolatile fission products and the actinides Np, Am, and Cm, plus smaller amounts of U and Pu. Techniques have recently been described which guarantee an absolutely safe containment of this high-active waste (HAW) for about 1000 years. At longer times, the risk to the biosphere is dominated by the actinides. If these actinides are isolated from the rest of the HAW and destroyed through nuclear incineration, the long-term risks of the HAW will be dramatically reduced. This paper presents a detailed scheme for removing the actinides from the Purex-HAW solution. In principle, the process consists of three different solvent extraction cycles, using HDEHP and TBP in three successive steps. The scheme has been tested on a synthetic HAW solution containing all fission products and actinides (except Z ≥96, Cm) usi...

H-10 — a new centrifuge for rapid liquid—liquid separations

Abstract A small centrifuge is presented which provides for rapid and efficient separation of a mixture of two liquid phases. The hold-up volume in the rotating bowl is 12 ml and hold-up time 0.25 s. The properties of the centrifuge and its applications for fast separations and in solvent extraction research are briefly discussed.

Behavior of Radionuclides in the Environment

The main objection against nuclear power is the risk of spread of “radioactivity” (radioactive elements) to the environment where it may cause health effects in humans. Such effects have already been discussed in chapter 15. As mentioned previously there are several suggested methods for the treatment of used nuclear fuel. However, all of them will require a final repository for the waste. The main difference is the total storage time, the different barriers, and the radiotoxicity of the final waste. In any case, if the repository is breached and ground water comes in contact with the fuel the readionuclides will be dissolved to a smaller or greater extent, depending on element and form. In this chapter, the chemical aspects of the sources of releases, and of the migration of the radionuclides in the environment, will be discussed. Their chemical properties, together with hydrology, determine how fast they will move from their point of entry into the groundwater to water resources used by man; this is schematically illustrated in Figure 22.1. In particular we discuss actinide behavior as these elements have the most hazardous radionuclides which may be released in the different steps of the nuclear fuel cycle, and, especially, from nuclear waste repositories. However, it may already be noted here that non of the actinides will contribute to the calculated dose to the critical population, except a tiny amount from 231 Pa, for a postulated leak from the planned Swedish underground repository as shown in Figure 22.2.

A New Fast Device to Transfer Radioactive Species from a Gaseous to a Liquid Phase

Abstract A new device for transferring the radioactive nuclides carried by a gas jet recoil transportation system to a liquid phase has been developed. It consists of a static mixer in which the gaseous and the liquid phases are thoroughly mixed and a centrifugal separator to facilitate a fast separation of the phases. The hold-up time of the device is ∼ 0.2 s and the maximum flow capacity 20 ml s −1 . It can remove more than 99% of the noble gases from a fission product solution. The new device has been tested in combination with the fast, continuous chemical separation system SISAK.

Radiation Biology and Radiation Protection

The biological effects of ionizing radiation were discovered soon after the production of intense radiation sources in the form of X-ray machines and radioactive elements about a century ago. Radiation was found to stop cell division and could therefore be used therapeutically to stop cancer growth. On the other hand, radiation applied locally was found to cause wounds, which were difficult to heal, and to induce cancer. Many serious accidents occurred as a result of the use of radiation before an adequate understanding of its biological effects led to formulation of rules for protection of workers. By 1922 approximately 100 radiologists (not patients) had died as a result of biological radiation damage.

Radiation Effects on Matter

Soon after the discoveries of X-rays and radioactivity it was learned that radiation could cause changes in matter. In 1901 P. Curie found that when a radium source was placed on his skin, wounds were produced that were difficult to heal. In 1902 skin cancer was shown to be caused by the radioactivity from radium but 5 years later it was learnt that radium therapy could be used to heal the disease. Large radiation doses were found to kill fungi and microorganisms and produce mutations in plants

Origin of Nuclear Science

The science of the radioactive elements and radioactivity in general is rather young compared to its maturity. In 1895 W. Roentgen was working with the discharge of electricity in evacuated glass tubes. Incidentally the evacuated glass tubes were sealed by Bank of England sealing wax and had metal plates in each end. The metal plates were connected either to a battery or an induction coil. Through the flow of electrons through the tube a glow emerged from the negative plate and stretched to the positive plate. If a circular anode was sealed into the middle of the tube the glow (cathode rays) could be projected through the circle and into the other end of the tube. If the beam of cathode rays were energetic enough the glass would glow (fluorescence). These glass tubes were given different names depending on inventor, e.g. Hittorf tubes (after Johann Hittorf) or Crookes tubes (after William Crookes). Roentgens experiments were performed using a Hittorf tube.

Detection and Measurement Techniques

The ionization and/or excitation of atoms and molecules when the energies of nuclear particles are absorbed in matter is the basis for the detection of individual particles. Macroscopic collective effects, such as chemical changes and heat evolution, can also be used. The most important of the latter have been described before because of their importance for dose measurements (e.g. the blackening of photographic films and other chemical reactions, excitation of crystals (thermoluminescence), and heat evolved in calorimeters; Ch. 8 ). Although animals have no known senses for detection of nuclear radiation, it has been found that subletal but large radiation fields can affect animals in various ways such as disturbing the sleep of dogs or causing ants to follow a new pathway to avoid a hidden radiation source. Apollo astronauts observed scintillations in their eyes when their space ship crossed very intense showers of high energy cosmic rays. People who have been involved in criticality accidents experiencing high intensities of n and γ have noted a fluorescence in their eyes and felt a heat shock in their body.