R. P. Kuatbekov

Current research reactors are unlikely to meet all needed missions over the next few decades. Many of the currently operating research reac­tors are ageing, and many missions are projected to grow in importance. Consequently, there is a need to design and build new research reactors. In many cases, particularly for industrial applications, new reactors can be de­signed from the beginning to use LEU rather than HEU fuel. In other cases, particularly if HEU or even plutonium fuel is required to retain essential performance characteristics, alternative solutions may need to be found to meet nonproliferation goals.

The customers of research reactors do not care whether the reactor is fueled by HEU or LEU—they simply need the results within a reasonable period of time and at reasonable cost. This is true whether the results are completed research, produced materials, or medical isotopes. Consequently, two key qualifications for any new research reactor will be: (1) its ability to meet customer needs; and (2) economic and technical feasibility. With respect to economics, both initial costs and refueling costs of the reactor should be considered to be reasonable by the operator.

In addition, not all countries can afford to perform experiments to op­timize fuel for their research reactors, as the United States and Russia have done, and these countries are likely to be a major market for certain types of research reactors in the coming decades. For these reasons, NIKIET is using reliable and tested fuel types and design solutions in its new research reactor designs. At the same time, proliferation concerns will need to be accounted for.

NIKIET is in the process of designing several new types of LEU-fueled research reactors for industrial, biomedical, training, and research applica­tions. The focus is on the development of pool-type reactors with integrated passive safety systems. Pool-type reactors are convenient for the end-user because they allow for flexibility in the core configuration and easy access to experimental positions. NIKIET uses standardized components in its reactor designs, which reduces costs and simplifies future repairs.

NIKIET is focusing on narrow-purpose reactor designs that optimize each reactor for the customer’s primary end use. There are two end uses that are in highest demand, both mentioned elsewhere in this report: medical isotope production and silicon doping. NIKIET is focusing on optimizing designs of two reactor types for these applications: (1) a low-power (500 kW or less) reactor with natural circulation for silicon doping and (2) a 15 MW reactor for isotope production. Some preliminary computations have been carried out on these reactor designs, and NIKIET plans to improve these designs in the future with additional computations and design work.

It is feasible to meet most customer needs using LEU-based research reactors. Designing reactors to use LEU from the start will not be as much of a challenge as retrofitting some current HEU-fueled reactors. In fact, modifying research reactor cores that were originally designed to use HEU can be very expensive and technically challenging, as illustrated by the case studies in Chapter 3. If the core is optimized during the design stage, then it can simultaneously be optimized for its missions. For example, if the core is initially designed to use LEU fuel, then differences in neutron fluxes and spectra can be accounted for from the initial design stages.

In fact, NIKIET has found that several of its designs for new LEU reac­tors maintain high flux levels to meet customer requirements and achieve reliable operation with high fuel burnups. NIKIET has now proven com­putationally that these LEU reactors should operate as well as similar HEU reactors.

On the other hand, some cutting-edge research requires reactors with unique designs or higher fast or thermal neutron fluxes. This research may not be able to be carried out using the types of standardized designs de­scribed here. In many cases, unique LEU-fueled reactors can be designed from the start to meet these needs; however, it was suggested by some at the symposium that maintaining a small number of special-purpose reac­tors fueled by HEU or plutonium could have value, particularly for fast reactor research.