Results of the preliminary tests for mixed oxide fuel test program at NSRR

Light water reactor fuel behaviors under reactivity-initiated accident (RIA) conditions have been investigated at the Nuclear Safety Research Reactor (NSRR) utilizing uranium oxide fuel rods. Furthermore, the NSRR program will be initiating RIA tests for uranium-plutonium mixed oxide fuel rods in 1981 in cooperation with the Power Reactor and Nuclear Fuel Development Corporation (PNC). As part of the preparation for the mixed oxide fuel test program, new test capsules consisting of dual containers were designed and fabricated. Employing these capsules, preliminary tests were conducted with uranium oxide fuel rods in order to examine the feasibility and nuclear characteristics of these experiments. The test results indicate the following: (1) The measured and predicted test rod energy depositions are in a relatively good agreement. This provides a confidence in the prediction of the maximum attainable energy deposition in the future tests (300 cal/g.fuel). (2) There is no mechanical energy generation (pressure pulse, water hammer) in a test at 340 cal/g. UO2 or less as expected. (3) Due to the hydrogen gas generated by Zircaloy-water reaction, rather conspicuous pressure rise takes place in the inner capsule. However, this does not change the fuel failure threshold. (author)