Increased Radiation Damage Research Articles

Properties of Lithium Hydride-V Vacancy Formation, Cavitation, and Lithium Precipitation in Irradiated Lithium Hydride

Expansion of crystals and compresses of LiH containing up to 40% LiT was observed during exposure to tritium β particles at temperatures from −196° to 400°C. Lithium metal precipitation was observed by electron paramagnetic resonance in small samples of similar composition. The results of auxiliary measurements of optical absorption, electrical conductivity and diffusion, nuclear magnetic resonance, and x-ray lattice parameter were used to interpret the data. Expansion was primarily related to the introduction of vacancies into the LiH crystal lattice to accommodate the products of radiation damage and tritium decay, to permit the formation of bcc Li metal, and to produce cavities in the crystals at high temperatures. Radiation damage was quickly reversed at the lowest temperatures, and the primary defects observed were interstitial He3 atoms and F centers. Warming to room temperature caused aggregation of the F centers and introduced vacancies which destroyed the interstitials Periodic warming for observation further increased the net expansion to allow the formation of bcc Li metal. At higher storage temperatures, vacancy diffusion stabilized a portion of the defects produced by radiation damage with the net result that increased expansion, increased Li formation, and H2 molecular species were observed in the crystals. The expansion rates in the temperature range of increasing radiation damage gave an activation energy consistent with that obtained for vacancy diffusion. An intercomparison of expansion and bcc Li formation at 23°C gave results consistent with the radiation-damage yield and with the formation of Li metal by a diffusion-controlled process. Above a 300°C minimum a second increase in expansion related to cavitation was observed.

GENETIC RADIATION DAMAGE REVERSAL BY NITROGEN, METHANE, AND ARGON

The oxygen effect, leading to increased radiation damage, can be countered or prevented to a large degree by the addition of 9 atmospheres of argon, nitrogen, or methane to 1 atmosphere of air or oxygen during irradiation. On the other has, the addition of 9 atmospheres of carbon monoxide to 1 atmosphere of air increases the radiation damage. These findings apply to dominant lethals produced in Drosophila virllis and sex-linked recessive lethals produced in Drosophila melanogaster. The stages of spermatogenesis from spermatogonia to mature sperm differ among themselves in their response to the same amount of x radiation and to the oxygen effect and its reduction or enhancement by the other gases. (auth)

Effects of cyanide and ionising radiation on the roots of Vicia faba

1. 1. An investigation has been made of the radiomimetic and radiomodifying action of cyanide on the roots of Vicia faba. 2. 2. Cyanide treatment alone causes inhibition of growth and mitosis, and an increase in the number of abnormal anaphases. These effects are most pronounced in conditions of high oxygen tension. 3. 3. When cyanide is used in conjunction with X-rays, there is an increased inhibition of growth and mitosis, and an increase in the numbers of abnormal anaphases. These effects occur when the experiments are conducted with nitrogen bubbling. In contrast, when the experiments are made with oxygen, cyanide does not increase radiation damage. 4. 4. Cyanide does not appear to modify the action of α-particles on Vicia roots. 5. 5. Various hypotheses have been considered in relation to these experimental results.