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What’s the most difficult question you’ve been asked as a maintenance instructor?
Blye Widmar
"Where are the prints?!"
This was the final question in an onslaught of verbal feedback, comments, and critiques I received from my students back in 2019. I had two years of instructor experience and was teaching a class that had been meticulously rehearsed in preparation for an accreditation visit. I knew the training material well and transferred that knowledge effectively enough for all the students to pass the class. As we wrapped up, I asked the students how they felt about my first big system-level class, and they did not hold back.
“Why was the exam from memory when we don’t work from memory in the plant?” “Why didn’t we refer to the vendor documents?” “Why didn’t we practice more on the mock-up?” And so on.
Yonghee Kim, Won Seok Park, Chang Kue Park
Nuclear Science and Engineering | Volume 144 | Number 3 | July 2003 | Pages 227-241
Technical Paper | doi.org/10.13182/NSE03-A2356
Articles are hosted by Taylor and Francis Online.
An importance function of the external spallation neutrons in an accelerator-driven system (ADS) has been introduced and characterized to address the source multiplication in a subcritical blanket. For a model ADS problem with a central external source, the source importance function is evaluated with a neutron transport code system. For a homogeneous core, essential characteristics of the importance are identified from the viewpoint of spatial distributions and energy dependency, etc. The importance function is evaluated for two different beam tube diameters, and its dependency on the buffer thickness is also addressed. In order to assess the impact of the power distribution on the importance function, a heterogeneous core is considered, and its importance function is evaluated. The analyses show that the peak importance occurs in the inner fuel blanket zone, not in the central source region, and the neutron importance in a high-energy regime, above 7 to 20 MeV, is high and increases with the energy. Also, the effects of a neutron absorber on the source importance are studied, and it is found that the source importance could be drastically reduced by surrounding the source with a strong neutron absorber such as B4C. In addition, the source importance function is compared with the conventional -mode adjoint flux, which is used as an importance function of fission neutrons in critical reactors. The comparison reveals that the inhomogeneous source importance function could be quite similar to the homogeneous -mode adjoint flux in both spatial and spectral distributions for a wide range of subcriticality.
