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55th annual Nuclear News Buyers Guide now available
For American Nuclear Society members and Nuclear News subscribers, the 2024 Buyers Guide is now available in the ANS Digital Nuclear Library. The print version will be mailed along with the May “Capacity Factors/Nuclear Security” issue of Nuclear News magazine.
The corresponding ANS online Buyers Guide database is available year-round to all readers—updated with the latest products, services, and suppliers contact information for more than 600 nuclear-related companies.
Shinya Mizokami, Hideya Kitamura, Yoshiro Kudo, Seiichi Komura, Yoshifumi Nagata, Shinichi Morooka
Nuclear Technology | Volume 152 | Number 1 | October 2005 | Pages 105-117
Technical Paper | Nuclear Reactor Thermal Hydraulics | doi.org/10.13182/NT05-A3663
Articles are hosted by Taylor and Francis Online.
To ensure fuel integrity, light water reactor cores are designed to avoid the onset of boiling transition (BT) inside the fuel assembly that leads to a deterioration of the heat transfer characteristics and subsequent excessive rise of the fuel-cladding temperature in the anticipated operational occurrences (AOOs). However, some boiling water reactors' AOO events result in immediate scram or suppression of the reactor power due to an increase in the reactor coolant void fraction. Recent studies show that a short duration of dryout inside the fuel assembly only leads to a small rise in the fuel-cladding temperature and thus does not pose a threat to fuel integrity. Many tests on BT and an improved comprehension of its mechanism have led to the development of a methodology to appropriately assess the fuel-cladding temperature after BT has been reached. The Standards Committee of the Atomic Energy Society of Japan has therefore proposed a cladding temperature criterion after BT. Applying the post-BT standard enables the value of the operating limit minimum critical power ratio (OLMCPR) to be decreased by allowing for a short duration of dryout. We calculated the fuel-cladding temperature and dryout duration in the load rejection condition without a bypass event. The calculated results show that both the fuel-cladding temperature and dryout duration meet the post-BT standard in the case of a small OLMCPR, which is determined by the loss of feedwater heating. This enables a more efficient reactor core to be designed by applying the post-BT standard to licensing analysis. The possibility of applying a post-BT standard is demonstrated from the results of this work.