Материал: Крючков Фундаменталс оф Нуцлеар Материалс Пхысицал Протецтион 2011

The key stages of HLW treatment are:

1.Monitored interim storage:

∙Liquid HLW is kept in stainless steel tanks; monitoring covers heat release and gas blanket composition (hydrogen resulting from water radiolysis is removed);

∙IFAs are kept in water pools on NPP sites;

2.Evaporation of liquid HLW (with its volume reduced by a factor of 150 to 200). This process is accompanied by:

∙a rise in specific activity of concentrated HLW;

∙intensified gas formation due to water radiolysis, with the ensuing risk of hydrogen–air mixture explosion;

∙increase in specific heat release caused by natural decay of nuclides, with the ensuing rise of HLW temperature;

∙intensification of corrosive activity of HLW as concentration and temperature rise.

3.Solidification of HLW. The purpose of this stage is to implant HLW into a stable matrix which will prevent waste migration into the environment. Incorporation of HLW into glass (vitrification) is believed to be the most suitable form of its immobilization.

There exist two vitrification processes.

Single-stage process. Liquid concentrated HLW is poured into a crucible, and glass-forming agents are added to it. The mixture heating is accompanied by complete evaporation of moisture, baking of the resultant dry waste, and melting of the glass mass.

Once it is cooled down, the crucible together with its contents will be sent off for disposal.

Two-stage process:

a) calcination of the starting HLW at 300–400 оС;

b) mixing of the calcination product and the glass-forming additives, with the resulting mass transferred to a melting furnace;

c) heat-up and vitrification of the mass at 1100–11 50 оС;

d) periodic discharge of the glass mass into steel containers; e) interim storage and disposal of the containers.

There are alternative technologies of HLW immobilization. They consist in incorporation of this waste into other stable materials, such as ceramics, glassceramics, mineral-like materials, e.g., SYNROC.

SYNROC is an abbreviation of Synthetic Rock. Creation of synthetic rock for HLW immobilization is based on the assumption that such material will be as stable and durable as natural rock.

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Treatment of liquid intermediate-level waste

Intermediate-Level Waste (ILW) includes solutions from extraction cycles (except for the first cycle), condensate resulting from evaporation of low-level waste, and vapor produced in evaporation of high-level waste.

The main stages of ILW treatment are:

1)precipitation and removal of ILW from liquid phases (settling and filtering with the use of coagulants);

2)ion-exchange treatment of the remaining liquid;

3)evaporation to produce solid residue;

4)immobilization by bituminization (the material is mixed with bitumen mass and is left to solidify);

5)containerization of the bituminous mass with ILW;

6)interim storage and final disposal.

Bitumen as an immobilization material has the following merits:

·low water leaching;

·suitability for all chemical forms of ILW (salts, hydroxides, organic compounds);

·good radiation resistance.

The disadvantages of bitumen are its combustibility (as a product of oil refining) and softening when heated (asphalt).

An alternative to ILW immobilization is its cementation, i.e. incorporation into concrete. Concrete as an immobilization material is appreciated for its:

·low cost and simplicity of handling;

·high radiation resistance;

·high heat conductivity;

·being neither combustible nor softening when heated.

However, concrete does not have sufficient chemical resistance to water. Various rates of water leaching are given below for comparison of several materials:

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That is why glass and SYNROC are predominantly used for immobilization of high-level waste and bitumen and concrete for immobilization of intermediateand low-level waste.

A fuel cycle ends with final disposal of special casks with RW in deep, stable geological formations. Common candidates for this purpose are: salt deposits, clayey sedimentary and other rocks.

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CHAPTER 3

INTERNATIONAL NON-PROLIFERATION SAFEGUARDS

3.1. IAEA activities

The global problem of non-proliferation is being dealt with by the International Atomic Energy Agency (IAEA [1]). Using a well-developed system of measures, referred to as the International Safeguards, the IAEA seeks to ensure that nuclear materials (NM) are used exclusively for peaceful purposes.

The system of International Safeguards is based on the Treaty for the Non-Proliferation of Nuclear Weapons (NPT) and is described in the IAEA document INFCIRC/153. It relies largely on the national systems of safeguards, making it possible to exercise control over all NM in the states

– signatories to the NPT.

Organization of international control over nuclear materials

The IAEA, established in Vienna in 1957, is an international intergovernmental institution related to the United Nations Organization through a special agreement and is thereby made part of the UNO system. This agreement states that the Agency acts as an independent international organization having a working relationship with the UNO. The IAEA reports its activities to the UN General Assembly and cooperates with the Security Council by providing it with the information and assistance that may be required for the Council to perform its functions of keeping peace and security in the world.

The Agency’s objectives are defined in its Statute:

∙It shall seek to accelerate and enlarge the contribution of atomic energy to peace, human health and prosperity throughout the world;

∙The Agency shall encourage research and development in the field of peaceful energy uses, and shall provide materials, services, equipment and facilities to this end;

∙The IAEA shall establish and apply safety rules in connection with the use of nuclear energy and radiation;

∙The Agency shall be authorized to establish and implement safeguards for exclusively peaceful uses of nuclear materials.

As of 2007, the IAEA had 144 states as its members. Its steering entities are the General Conference and the Board of Governors.

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The General Conference is the highest authority of the Agency. Its sessions are held once a year. Most of its decisions and resolutions are made by a simple majority vote.

The Board of Governors guides the IAEA work in between the General Conference sessions. Its decisions on the main aspects of the Agency’s activities are subject to approval by the General Conference. The Board of Governors has 35 members. Its permanent members are ten states whose nuclear science and engineering are best developed, namely: Russia, China, USA, UK, France, Germany, Japan, Italy, Canada, and India. Besides, every year, three more states most advanced in the field of nuclear technology are appointed to the Board for a term of one year. All other members are elected for two years to represent states, other than the above ten, from seven regions: Latin America, Western Europe, Eastern Europe, Africa, Middle East and South Asia, South-East Asia and the Pacific, and Far East.

Besides, the Board of Governors will periodically set up ad hoc committees to address major specific matters. Thus, in view of the NPT coming into force in 1970, the Board appointed a committee for development of a standard safeguards agreement, which came to be referred to as document INFCIRC/153.

All regular practical activities of the Agency are carried out by its Secretariat. The IAEA Secretariat relies on the guidance and leadership of its Director General who is responsible for fulfillment of the Agency’s work program. At present, the post of Director General is held by Yukiya Amano from Japan.

The administrative structure of the IAEA is similar to that of a large research center (Fig. 3.1) and is tailored to its purposes. Its six major departments deal with: technical cooperation; nuclear energy; nuclear safety and security; management; nuclear sciences and applications; and safeguards. The departments consist of divisions, each subdivided into sections to address specific subjects.

Main areas of IAEA activities

All the variety of IAEA activities can be divided into three general areas: control over nuclear materials; technical assistance to countries; and scientific programs. Out of the six departments, three are responsible for implementation of scientific programs:

The departments for nuclear energy and for safety and security pursue studies in two directions:

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