Research Programs

Publications:

1. Y. Inoue, Z. Xu, E. Pilat and M. S. Kazimi, “ Effects of Burnable Poisons on Neutronic Performance of a Very Long Cycle BWR,” MIT Report, September, 2003.
2. Y. INOUE, Z. XU, and E. PILAT, “Effectiveness of Different Burnable Poisons in a Long Cycle BWR,” PHYSOR, April 2004.
3. Y. INOUE, E.E. PILAT, Z. XU, and M.S. KAZIMI, “Combining Thorium with Burnable Poison for Reactivity Control of a Very Long Cycle BWR,” MIT Nucl. Eng. Dept. MIT-NFC-TR-064, June 2004.

Investigators:

• Prof. Mujid Kazimi
• Dr. Edward Pilat
• Dr. Zhiwen Xu
• Mr. Yuichiro Inoue

A Very Long Cycle Boiling Water Reactor

Long cycle reactor core operation offers two major distinct advantages: (1) allows for improving the plant capacity factor and (2) reduces the infrastructure requirements for storing new and spent fuel. Significant savings from fewer refueling shutdowns can be realized for a long cycle core, if the other functions of inspections and maintenance can be performed without extensive shutdowns. There is also much less radioactivity release to the environment during refueling outages. Another advantage of long cycle cores is that it is easier to store fuel assemblies and components, which effectively lowers the cost. Besides these, the long cycle core provides another advantage, namely an intrinsic institutional barrier of proliferation resistance by reducing fuel handling.

A Boiling water reactor (BWR) was chosen as a candidate for long cycles by our collaborator, Toshiba. The objective of this project is to design a long-cycle BWR core operating at 900 MW thermal for 15 years. Note that both the power density and total power of this core are below conventional BWR designs. This is mostly due to the market foreseen for this reactor in developing countries that might not need larger size units. On the other hand this long cycle still involves increasing the fuel burnup to about 100MWd/kg, almost double the current burnup level.

The MIT effort examined the effects of various burnable poisons on the cycle length and fuel needs. We have confirmed the basic Gd specification that Toshiba issued based on a fuel assembly geometry and based on a Haling calculation. The latter allows for predicting the maximum power peaking factors in the core during its operation. These calculations were repeated for Er and for WABA poisons. These calculations were performed with the codes CASMO-4/ SIMULATE-3. Comparison of enriched Gd design with Er and WABA design indicates that the WABA design might have an advantage over the other designs in terms of required initial enrichment. However, Gd seems to offer the required control without the addition of gas into the fuel pin. The use of thorium as an effective initial poison was found to reduce the required enrichment by 5-10%