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Newest Russian icebreaker ready to hit the ice
The Russian nuclear-powered icebreaker Arktika. Photo: Rosatom
The Arktika, Russia’s latest nuclear-powered icebreaker, sailed from the Baltic Shipyard in St. Petersburg last week, bound for the Murmansk seaport. The voyage is scheduled to take approximately two weeks, during which time the vessel will be tested “in ice conditions,” according to Rosatom, Russia’s state-owned atomic energy corporation.
J. B. Clarity, K. Banerjee, H. K. Liljenfeldt, W. J. Marshall
Nuclear Technology | Volume 199 | Number 3 | September 2017 | Pages 245-275
Technical Paper | dx.doi.org/10.1080/00295450.2017.1361250
Articles are hosted by Taylor and Francis Online.
A novel assessment has been completed to determine the previously unquantified and uncredited criticality margin available in as-loaded commercial spent nuclear fuel (SNF) canisters. This assessment was performed as part of a broader effort to assess issues and uncertainties with storage, subsequent transportation, and final disposal of SNF canister systems. Detailed analyses crediting the burnup, initial enrichment, and postirradiation cooling time of actual SNF inventory were performed for 554 SNF canisters stored at 23 commercial reactor sites to determine realistic criticality safety margins. These detailed analyses were automated by the Used Nuclear Fuel-Storage, Transportation & Disposal Analysis Resource and Data System (UNF-ST&DARDS), a comprehensive, integrated data and analysis tool. Calculated, uncredited criticality margins (Δkeff) with respect to the safety analysis results range from 0 to almost 0.30 Δkeff for normal storage and transportation cases. Calculated eigenvalues (keff) range from 0.72 to 1.11 assuming a degraded neutron absorber disposal condition, and they range from 0.94 to 1.20 assuming a degraded basket disposal condition. Calculations with NaCl present in the moderator (which is possible for certain disposal geologies) were used to demonstrate the possibility for subcriticality for degraded cases with a keff above 0.98 with freshwater. The methods used to calculate keff for the canisters analyzed in this work are discussed in detail.
The results demonstrate that, for the majority of canisters analyzed here, significant uncredited safety margin is available that could be used to compensate for uncertainties in the SNF assembly and canister internal components. These uncertainties are associated with long-term storage and subsequent transportation and disposal. Results also suggest that the inherent margins associated with how canisters are loaded could support future changes in licensing SNF storage and transportation systems to directly or indirectly credit the margins associated with actual SNF characteristics. Ongoing research continues to gather additional data to quantify uncredited safety margins for SNF canisters loaded at other nuclear reactor sites and to explore potential methods for applying this uncredited margin.