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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.
T. M. John, C. P. Reddy, Om Pal Singh
Nuclear Science and Engineering | Volume 80 | Number 3 | March 1982 | Pages 370-378
Technical Paper | doi.org/10.13182/NSE82-A19821
Articles are hosted by Taylor and Francis Online.
In this paper, an attempt has been made to investigate the noise transmission characteristics of nonmultiplying media of liquid-metal fast breeder reactors (LMFBRs) and study its implications on the detection of malfunctions in LMFBR cores by using out-of-core detectors and noise analysis methods. Neutron wave propagation technique has been used to study the problem by employing different approximations such as infinite and finite medium, one- and two-group diffusion theory, and multiregion and multigroup diffusion theory approximations. It has been found that reactor core noise will be transmitted to the out-of-core detectors with equal attenuation for all frequencies, ω < (ωΣt)min where υ is the speed of neutrons and Σt is the total macroscopic removal cross section of the medium. For normal in-reactor vessel nonmultiplying media, (υΣt)min is of the order of 1 kHz. However, for materials like graphite if used as a moderator surrounding the out-of-core detectors, the limit (υΣt)min can be as low as 10 Hz. Reactor noise of malfunctions due to thermal events inside the reactor core such as sodium boiling lies in the frequency range of 2 to 15 Hz for integral boiling and goes up to 1 kHz for local boiling. Noise due to mechanical events is also a high frequency phenomenon. Therefore for detecting the malfunctions due to thermal and mechanical events in LMFBR cores by out-of-core detectors and noise analysis methods, one has to keep in mind that for moderating materials like graphite used in the surroundings of detectors, a band limited noise in reactor may be transmitted to detector locations in a distorted way and since high frequency noise is likely to be attenuated more, it will pose a problem in detecting the malfunction in its incipient stage.
