Gaining Access

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51 'appropriate' waste form. In this present work, this covers the treatment of graphite wastes to reduce activity levels or to condition the material in other ways, and also considerations of the initial dismantling methodology);

• immobilization: 'conversion of waste into a waste form by solidification, embedding or encapsulation for the control of radioisotopes' (by reducing the potential for migration or dispersion of radionuclides during handling, transport, storage and/or disposal); and

• disposal options: included here is a specific definition of 'conditioning': 'those operations that produce a waste package suitable for handling, transport, storage and/or disposal'. Conditioning may include the conversion of the waste to a solid waste form, enclosure of the waste in containers, and, if necessary, providing an overpack.

The breakdown of the i-graphite management task is clearly complex but, in all cases, these operations contribute to the prime CRP objective of investigating treatment options for i-graphite in order to meet waste acceptance criteria (where they exist) – or to assist in their definition. Reference to the approach of the CARBOWASTE project is useful here: a consensus was achieved amongst their participants on twenty four potential options for the management of i-graphite, which are shown in Table 6 [73]. These options address the complete life cycle: in-reactor storage, conditioning, retrieval and treatment to final disposal.

TABLE 6. CARBOWASTE OPTIONS CONSIDERED FOR I-GRAPHITE

ASSESSMENT

Option No. Description

1 Encapsulation and deep repository

2 Size reduce graphite for minimised waste package volume; local immobilization 3 Minimum processing

4 Deferred start with remote retrieval 5 Deferred start with manual retrieval 6 Minimum processing with deferred start

7 Alternative retrieval and graphite form in package 8 Alternative retrieval and repository

9 Interim storage and repository

10 Alternative retrieval, encapsulation and intermediate storage 11 In-situ treatment and near-surface repository

12 Ex-situ treatment and near surface repository

13 Gasification and isotopic dilution with conventional fossil fuel CO

2

14 Gasification and isotopic dilution with conventional fossil fuel CO

2 as a result of sequestration 15 Gasification and isotopic dilution by dispersal as CO

2 in the sea 16 C-14 re-use

17 C-14 re-use with no isotope separation 18 Graphite re-use for nuclear application only 19 In-situ entombment

20 Waste volume reduction and emission to atmosphere

21 Make use of graphite as inert filler, removing the need for some encapsulation 22 Immobilise in medium impermeable to ¹⁴C

23 Chemically bind ¹⁴C

24 Interim storage of raw waste (25 years) then encapsulation and disposal in an interim repository

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The key findings from the analysis were :

• Option 10 (Alternative retrieval, encapsulation and intermediate storage) has the highest associated costs due to the continual replacement of surface stores.

• Option 19 (in-situ entombment) has the lowest costs due to the lack of any construction stages.

• Gasification options (Options 13, 14, 15 and 20) and re-use options (Options 18 and 21) have a lower costs due to a fraction of the ¹⁴C being diverted elsewhere (with less i-graphite requiring consignment to a repository) or to a near-surface repository.

As may be seen from Table 7, each of the four basic categories of investigation is adequately covered within the present CRP, with some programmes spanning more than one of them. It is important to underline that management of secondary waste generated by treatment processes has not been addressed by CRP participants in their projects although it is a key issue when considering waste treatment processes.

TABLE 7. GENERAL BREAKDOWN OF RESEARCH AGREEMENTS AND CONTRACTS UNDER THE CRP

CH = Characterization, PR = Processing, IM = Immobilization, DI = Disposal Country, organization, and researchers involved

Research focus CH PR IM DI

China. Tsinghua University, INET, Li Junfeng

Disintegration of Graphite Matrix from the High-Temperature Gas-Cooled Reactor Fuel Elements

France. Christine Lamouroux (CEA), Gerard Laurent (EdF), Laurence Petit (Andra)

Characterization of Radionuclides in Graphite Wastes Germany. FZJ, Werner von Lensa

CARBODISP. Treatment of Irradiated Graphite to Meet Acceptance Criteria for Waste Disposal.

Germany. FNAG, Johannes Fachinger Graphite as a Matrix Material

Lithuania. INPP. Alexander Oryšaka

Integration of Waste Management Features with Plant Dismantling Lithuania. LEI. Ernestas Narkunas, Povilas Poskas

Treatment Requirements for Irradiated RBMK-1500 Graphite Russia. VNIINM, Vladimir Kascheev, FGUP RADON, Olga Karlina

Methods of Irradiated Graphite Treatment – Characteristic Properties of Irradiated Graphite

Spain. ENRESA, Jose Luis Leganes Nieto

Measuring Techniques for ³⁶Cl, ⁹⁹Tc and ¹²⁹I in Graphite, and Compatibility Tests to Meet Acceptance Criteria

Switzerland. PSI, Hans F. Beer

53 Determination of Long lived Radionuclides with Special Emphasis on Reactor

Graphite

Ukraine. IEG, Boris Zlobenko

Investigation on the Conversion of Irradiated Graphite from the Decommissioning of Chernobyl NPP into a Stable Waste Form acceptable for Long-Term Storage and Disposal

United Kingdom. NDA, Simon Norris

Progression of UK Strategy Regarding Options for Long-Term Management of Irradiated Graphite

United Kingdom. The University of Manchester, Abbie Jones, Tony Wickham

14C and ³H removal from UK Graphite Waste

United Kingdom. University of Sheffield, Russell Hand

Development of Composite Materials to Utilise and Dispose of Waste Irradiated Graphite

United Kingdom. Bradtec, David Bradbury, Hyder/Bradtec, Jon Goodwin, Studsvik UK, Maria Lindberg, Costain, Terry Tomlinson, with Arbresle Ingéniere (France), Laurent Rahmani

Retrieval Demonstration – Novel Methodology, Efficacy of Gasification, Concept Design of CO2 Delivery System

Feasibility and Suitability of the Injection of Irradiated Graphite as an Aqueous or Oily Suspension or Foam into Confined Geological Formations

Chlorine Speciation

United Kingdom. NNL. Martin Metcalfe, Anthony Banford

Investigation into Aspects of the Production and Disposition of Carbon-14 in Magnox Reactor Graphite Cores

United States. Idaho State University, Idaho National Laboratory, Mary Lou Dunzik-Gougar

Characterization and Treatment of Carbon -14 in Irradiated Graphite

These contributions can be conveniently represented by the following diagram indicating differing management strategies (Figure 18):

Management options Investigated within the CRP by:

• PSI (Switzerland*)

• Bradtec/Hyder/Stu dsvik UK/Costain (UK)

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• Enresa (Spain*)

• PSI (Switzerland*)

• FZJ (Germany*)

• FNAG (Germany)

• EdF/CEA/Andra (France*)

• NDA (UK*)

• University of Sheffield (UK)

• INPP & LEI (Lithuania)

• Russia

• NNL (UK)

• EdF/CEA/Andra (France*)

• UoM (UK)

• Idaho State University (USA)

• Radon (Russia)

• Tsinghua University (China)

• INPP & LEI (Lithuania*)

• Bradtec/Hyder/Studsvi k UK/Costain (UK)

• NNL (UK)

55

• VNIINM (Russia)

• Bradtec/Hyder/Studsvi k UK/Costain (UK)

• Arbresle Ingéniérie (France)

FIG. 18.Management strategies covered by work in the CRP.

The next four sections of this TECDOC will cover, in turn, the current status of work on Characterization, Processing, Immobilization, and Disposal. The contribution of the relevant research programmes under these headings will be identified along with the general conclusions reached: in addition, the position on other work known to be in progress will be updated from the position in Ref. [2]. For each CRP work programme, a formal full report is annexed to this document (CD ROM). These reports cover in full the interim results provided at Research Coordination Meetings held during the course of the CRP.

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