Experimental Studies of Independent Fission Product Yields - Current Status and Future Directions

Nuclear data underpin much of nuclear science and technology, and are particularly important in modeling and simulation of applications where radiation transport plays a role. There is currently an ongoing effort in the nonproliferation community to identify nuclear data needs, and one type of nuclear data that consistently stands out is fission product fields. These yields impact many areas relevant to national security, such as reactor monitoring and nuclear forensics. However, in the ENDF nuclear data evaluation library, which is used by many nuclear transport codes, fission yields have not been updated since the early 1990’s. There is a general consensus in the community that new evaluations are needed, particularly considering advances in the field over the last two decades. Nuclear data evaluations rely on experiments that provide cumulative yields, independent yields, and decay properties of the fission products. While the methodologies for measuring cumulative yields are well established, the same is not true for independent yields, and as a result there is much less experimental information available for those yields. This situation is starting to change as new experiments and techniques are being developed, and here I will provide an overview and the current status of this field. I will also briefly discuss the ongoing efforts to accurately measure the energy dependence of fission yields, something that is key in generating new evaluations.