RAW characterization and control

Reliable RAW processing shall result in a waste package, corresponding to the requirements of the waste disposal site, established usually as waste acceptance criteria (WAC).

The establishment of an efficient waste control strategy and implementa­tion of a proper waste characterization and control system is one of the key conditions to achieve the WAC. The RAW control system shall cover control of radiological, chemical and mechanical properties of RAW in each RAW stream and during the entire RAW life cycle. There are three principal steps in RAW control:

• Characterization of ‘as generated’ waste, providing principal informa­tion on the waste parameters for waste processing planning and selec­tion of processing technologies. This information is also a basis for estimation (prognosis) of the final waste package parameters.

• Control of RAW processes and operation of processing technologies (both treatment and conditioning steps), including control of material inputs, e. g. waste encapsulation matrix components, if applicable.

• Characterization of the final waste package to demonstrate its compli­ance with the WAC.

Commonly, RAW control is performed in different types of laboratories from simple, operational laboratories for basic waste and processes control to advanced radiochemical laboratories for precise control of critical waste parameters. The principal steps in a laboratory waste control procedure are: sampling, chemical parameter determinations, radiological parameter determinations and control of mechanical properties (applicable mostly for the final waste form and/or waste package). An unavoidable condition for advanced RAW control system implementation is the availability of a well — qualified accredited control laboratory, properly equipped with the relevant instrumentation, having in possession radiochemical methodologies for sample processing (ISO, ASTM, local accredited procedures), with a highly qualified staff and implementation of an advanced quality assurance/quality control (QA/QC) system.

The systematic or random control of finalized waste packages, whether for long-term storage or final disposal, is usually performed by non-destructive gamma or neutron scanning (tomography) of entire waste packages, using special scanning facilities, facilitated with special software for evaluation and presentation of results.

A consistent part of the waste control system is record keeping, providing traceability of waste parameters for regulatory purposes as well as for potential future decision making.

A compendium, describing the establishment of a waste control strategy, the distribution of responsibilities, a quality assurance system, and provid­ing an overview of characterization methods and procedures is given in Ref. [8].

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