- WP1: page 24, 2nd paragraph added, from George Flannagan’s email
- “Upcoming work by a new committee of the American Nuclear Society (ANS) to create a safety standard for FHRs, ANS 20.1, will provide the basis to develop consensus-based FHR-specific General Design Criteria (GDC) derived from existing LWR-specific GDC, to be used in licensing reviews. ANS 20.1 could be used by the regulator to judge if the FHR design conforms to the current regulatory requirements contained in 10CFR 50 or 10CFR 52. The determination is made by reviewing the application against the NRC standard review plan (may be tailored to account for unique design features) using the General Design Criteria as acceptance criteria. If the NRC endorses ANS 20.1 then the ANS 20.1 requirements will be used in lieu of Appendix A of 10CFR 50 as acceptance criteria. This was also the approach by which the MHTR, CRBR, SAFR, and PRISM were reviewed.”
- WP1: fig 1-6 on page 25: v2, v1
- WP1: Syd Ball comment not addressed in fuel section: ” note the success by the Chinese in producing good TRISO fuel for their HTR-10, for which ~no failures have been seen during operation. “
- WP2-4: “Preamble” instead of abstract
- WP2-4: generate using Adobe plug-in, to keep the links and bookmarks
- WP3: Greenspan/Tommy on flux curve
- WP1-4: remove the word “Final” from the cover page, and move FHR logo up
- There is a big concern in modular HTGRs about adequate mixing of the core outlet coolant that gives this “integral average” temperature referred to in this section. As the molten salt coolant moves through the core, I’d guess the power and flow distributions would be such that a fair amount of uneven heating of the coolant would occur. Since the overall core delta-T is small compared to HTGRs, the temperature fluctuations would tend to be much smaller; however, because of the much better heat transfer via the salt, the effects of the fluctuations on the structures it encounters might even be larger. Might be worth looking at.
- Note that the Japanese (HTTR) had a huge amount of trouble with their water cooled cavity cooling system – to the point that they “would do almost anything to avoid using a water-cooled RCCS.” As the FHR design gets further along, I’d suggest reviewing their tales of woe.
- Regulatory foundation: At some point, it would be useful to review the IAEA work in this area. There was lots done for modular HTGRs [at least in my experience – & maybe similar stuff for fast reactors, not in my experience base]. Also work done on generic advanced reactors. See IAEA TECDOCs 1366 & 1570. 1366: Advanced nuclear Plant Options to Cope with External Events. 1570: Proposal for a Teachnology-Neutral Safety Approach for New Reactor Designs.
- General discussions about PRA (in 4.1): there was I think a real good point made long ago by Bob Budnitz (NRC) about how PRAs should be thought of for the passively safe reactor designs, where “failure probabilities” need to be assigned to passive systems [e.g., how do you fail a heat transfer coefficient?!]. My favorite VG on this idea is attached.
The four FHR white papers are now available for download in their final versions: