[en] Purpose: To reduce the volume of spent fuel insertion containing boron for long-term storage. Method: A fuel insertion is decontaminated to remove radioactive substances on the surface, inserted into an airtight chamber, cut into small pieces adapted for long storage, tritium discharged from a cladding tube is withdrawn from the airtight chamber when cutting, and passed through a catalytic reactor to convert it into tritium water. It is then adsorbed to an adsorbing floor, purified atmosphere is circulated in the airtight chamber, and tritium water thus adsorbed and fixed on the adsorbing floor is heated and purged, recovered and fed to a tritium solidifying step. (Yoshihara, H.)

[en] When processing radioactive metal wastes discharged from a nuclear power plant or radioactive material-handling facility, there is a method of dissolving to remove surface layers by using acidic solution or by colliding particles of ice or dry ice for separating to remove those materials deposited on the surface. However, oil contaminations or rubber and plastic materials can not always be removed. In view of the above, a hitting finger is constituted such that it can move vertically by driving means and a second hitting finger is disposed to the circumferential surface of a rotating drum. A guide wall having a slit extending vertically is formed in front of the hitting finger and the hitting finger is protruded through each of the slits into the processing chamber. Since deposited matters peeled off upon hitting are discharged through a sieve to a scale hopper, there is no external scattering and metal wastes and deposited matters can be separated easily and reliably. (K.M.)

[en] Radioactive metal wastes are packed to the inside of a container and the inside is deaerated and tightly sealed. Then, the container is disposed in a high pressure vessel charged with liquid medium and then the liquid medium is pressurized under a normal temperature by means of pressure generation means. This can compress the radioactive metal wastes at the inside of the container such that they are tightly adhered to each other. The compressed container is heated in a heat treatment furnace to diffuse and join the radioactive metal wastes to each other. In this way, since the compression operation is conducted under a normal temperature by means of liquid medium, a relatively high pressure can be exerted easily and safely to the container. Further, since no high pressure gas medium is used, the operation is free from legal high pressure regulation and the labors for the radioactive material removal can be saved. (T.M.)

[en] High-level radioactive waste contains a variety of radioactive materials in large amounts. Radiation emitted from radioactive materials may give humans significant effects by causing external exposure or internal exposure through inhalation or ingestion. Geological disposal is a method to protect humans and the environment from such effects and is being adopted and addressed by various countries. The purpose of this paper is to provide technical experts outside the disposal field with an understanding of the mechanism for ensuring the safety of geological disposal. Regarding the occurrence, classification, and disposal methods of radioactive waste in general, this paper introduces based on the safety standard documents of Japan and the International Atomic Energy Agency (IAEA), and explains that the disposal is based on the policy of 'confinement' and 'isolation.' Taking up the research case on the concept of geological disposal in France, this paper gives basic explanations on the following. (1) What kind of specific mechanism is used to ensure safety in the geological disposal being developed? (2) Under the mechanism of ensuring safety in geological disposal, what kind of radioactive materials are likely to appear to the living environment? (3) Is it possible to attain the safety protection target? (A.O.)

[en] Mainly based on a NEA's Radioactive Waste Management Committee (RWMC) study report (2007 - 2011) on the issues of reversibility and retrievability (R and R) in geological disposal of radioactive wastes, the present review paper explains the R and R project with a view to following up. The concept of geological disposal (engineering barrier and layout of the facilities), step-wise execution and the reversibility, state of a disposal site specifically for high-level radioactive wastes and the retrievability, some observational view on the R and R, development during these 30 years, current status of OECD member countries' programs for R and R and the current situation of Japan are described. (S. Ohno)

[en] Object: To eliminate a danger of explosion in case where oxygen is safely removed from waste gases containing radioactive rare gases for recovery thereof into a gas cylinder. Structure: In an atomic power plant, carbon dioxide gas and water are removed in a pretreatment system. Next, it is cooled by liquefied nitrogen in a heat exchanger and transported to a first condensing system composed of a low temperature adsorption bed to condense radioactive rare gases in the adsorption bed. The thus condensed rare gases are fed under pressure by a pump to a second condensing system composed of Cu and Cu group alloy bed. Next, oxygen in the condensed gases is reacted and removed in the Cu alloy bed maintained at 600⁰C and the rare gases are fed to the gas cylinder for recovery. (Yoshihara, H.)

[en] For the volume reduction and stabilization treatment of zircaloy hulls and hardware, a new hot isostatic pressing (HIP) process using a low pressure of 10 MPa has been developed. The hulls and hardware were pre-compacted in an SUS 304 capsule to about 70% of their theoretical density. The evacuated capsule was heat treated at 1000degC for 3 hr. To develop practical treatment technology, a large scale solid product of φ 300 x 450^H mm was fabricated and its product properties were investigated. (author)

[en] The fast breeder reactor could produce the nuclear fuel more than that used in a core by using a fast neutron for nuclear fission. Nuclear power generation is reviewed from the viewpoint of remarkable rise of the oil prices of these days and global warming prevention, but the deposits of uranium resources are not big at all. The expectation of the nuclear power generation swells out for a fast breeder reactor more and more, too. Therefore the birth of the fast breeder reactor and the change of the reactor type, each country and domestic development status, future development items and development program will be reviewed for eight times from this time. No.1 describes the discovery of the nuclear fission, the confirmation of the chain reaction and the birth of the fast reactor. Coexistence of the breeding and power generation was identified as well as the criticality of the fast reactor. (T. Tanaka)

[en] Following a previous report of the R and R project with a view mainly based on NEA's Radioactive Waste Management Committee (RWMC) study (2007-2011), the present report introduces the status of the technical aspect of the retrievability in several countries of EU based on the EC/EURATOM report on concerted action on the retrievability of long-lived radioactive waste in deep underground repositories and OECD/NEA report titled as summarized reasons to retrievability and reversibility questionnaire issued to NEA member countries in 2008. To understand the retrievability, we need to understand each country's disposal concept as well as features of base rocks, engineering barrier systems, and design of disposal facility of that country. The outline of the international projects such as PEBS, MoDeRn, and ESDRED done for demonstration and evaluation of retrievability in engineering barrier in geological disposal is presented. (S. Ohno)

[en] Vitrified high level liquid waste must be stored under survellance for certain periods before disposal. During storage, the removal of decay heat is needed to maintain the integrity of the vitrified waste. To establish a evaluation procedure for removing this decay heat, tests were made on a 1/5 scale model. The results show that the dominant factors for cooling characteristics are the range of turning loss coefficients for combined flow from pit to plenum and the ratio of inner to outer diameter of the annular passage. (author)