Development of the physical model

Full text: The Physical Model was developed during Program 93+2 as a technical tool to aid enhanced information analysis and now is an integrated part of the Department's on-going State evaluation process. This paper will describe the concept of the Physical Model, including its objectives, overall structure and the development of indicators with designated strengths, followed by a brief description of using the Physical Model in implementing the enhanced information analysis. The work plan for expansion and update of the Physical Model is also presented at the end of the paper. The development of the Physical Model is an attempt to identify, describe and characterize every known process for carrying out each step necessary for the acquisition of weapons-usable material, i.e., all plausible acquisition paths for highly enriched uranium (HEU) and separated plutonium (Pu). The overall structure of the Physical Model has a multilevel arrangement. It includes at the top level all the main steps (technologies) that may be involved in the nuclear fuel cycle from the source material production up to the acquisition of weapons-usable material, and then beyond the civilian fuel cycle to the development of nuclear explosive devices (weaponization). Each step is logically interconnected with the preceding and/or succeeding steps by nuclear material flows. It contains at its lower levels every known process that is associated with the fuel cycle activities presented at the top level. For example, uranium enrichment is broken down into three branches at the second level, i.e., enrichment of UF6, UCl4 and U-metal respectively; and then further broken down at the third level into nine processes: gaseous diffusion, gas centrifuge, aerodynamic, electromagnetic, molecular laser (MLIS), atomic vapor laser (AVLIS), chemical exchange, ion exchange and plasma. Narratives are presented at each level, beginning with a general process description then proceeding with detailed descriptions in the categories of especially-designed or prepared equipment, dual-use equipment, non-nuclear material, nuclear material, technology/training/R and D, other observables, by-products/effluents and end products. The most distinguished feature of the Physical Model is to characterize each technology and process in terms of indicators specifying the existence or development of the specific technology or process. The specificity of indicators for a given nuclear technology or process is assessed, based on which relative strength is designated to each indicator as strong, medium or weak. The objectives of the development of the Physical Model are three-fold: (i) provide a general and easily accessible reference for fuel cycle activities; (ii) to provide a model for a State's nuclear program which would be a subset of the Physical Model and (iii) to provide a simple mapping function from the indicators to the existence or development of specific nuclear activities. It is intended to be used as a technical tool in implementing the enhanced information analysis. For example, it provides a model template to organize the consistency evaluation to justify the internal consistency of a State's nuclear program. The Physical Model indicators provide a means to associate a question or inconsistency with a specific nuclear activity. The designated strength of an indicator provides a reference to assess the proliferation significance of the question or inconsistency. The indicators and designated strengths will also help determine clarification or follow-up actions to respond to a given situation. In developing and implementing State-level safeguards approaches, the Physical Model will help to characterize a State's fuel cycle program and assess its potential to acquire weapons-usable materials based on identification of the acquisition paths at the State level. Originally issued in eight volumes in October 1998, the need to include Spent Fuel Management, Intermediate and High Active Waste Management and R and D Activities in Connection with Hot Cells was recognized. Expansion of the Physical Model was initiated in 1999 with support from Member States and will be completed by the end of this year. Methodology studies were also carried out with support of MSSP's, including R and D on the strengths of the Physical Model indicators when considered in combinations. The Physical Model is anticipated to be subject to periodic review and update based on technical advances in nuclear fuel cycle activities, experience gained through its application practice and new requirements for implementing the strengthened safeguards. Update of the Physical Model is also planned and will be executed in the near future. (author)