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RISS 인기검색어
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- 저자 : Suk Pavel (검색결과 2 건)
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Geometry Optimization of Dispersed U Mo Fuel for Light Water Reactors
Novak Ondrej,Suk Pavel,Kobylka Dusan,Sevecek Martin 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.9
The Uranium/Molybdenum metallic fuel has been proposed as promising advanced fuel concept especially in the dispersed fuel geometry. The fuel is manufactured in the form of small fuel droplets (particles) placed in a fuel pin covered by a matrix. In addition to fuel particles, the pin contains voids necessary to compensate material swelling and release of fission gases from the fuel particles. When investigating this advanced fuel design, two important questions were raised. Can the dispersed fuel performance be analyzed using homogenization without significant inaccuracy and what size of fuel drops should be used for the fuel design to achieve optimal utilization? To answer, 2D burnup calculations of fuel assemblies with different fuel particle sizes were performed. The analysis was supported by an additional 3D fuel pin calculation with the dispersed fuel particle size variations. The results show a significant difference in the multiplication factor between the homogenized calculation and the detailed calculation with precise fuel particle geometry. The recommended fuel particle size depends on the final burnup to be achieved. As shown in the results, for lower burnup levels, larger fuel drops offer better multiplication factor. However, when higher burnup levels are required, then smaller fuel drops perform better.
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Distribution of natural and anthropogenic radionuclides in northwest Mediterranean coastal sediments
Lee, Sang-Han,Povinec, Pavel P.,Chisholm, John R.M.,Levy, Isabelle,Miquel, Juan-Carlos,Oh, Jung-Suk Elsevier 2017 JOURNAL OF ENVIRONMENTAL RADIOACTIVITY Vol.172 No.-
<P><B>Abstract</B></P> <P>The distribution of radionuclides in NW Mediterranean coastal sediments, and the processes controlling their abundance were investigated in three cores taken near the island of Porquerolles and one offshore Monaco. The sediments collected near Porquerolles were strongly anoxic due to diagenetic processes involved in the decomposition of organic matter, whereas they transitioned from oxic to anoxic at a depth of 4 cm beneath the seawater interface at Monaco. Organic carbon (OC) was more abundant in sediments at Porquerolles (by about a factor of 3–5) than at Monaco and elsewhere in the coastal NW Mediterranean. Sediment cores collected NE of Porquerolles also possessed elevated uranium concentrations that correlated with high OC content and strong reducing conditions. The <SUP>239,240</SUP>Pu and <SUP>241</SUP>Am activities in surficial sediments ranged from 1 to 5.7 Bq kg<SUP>−1</SUP> and 0.3 to 1 Bq kg<SUP>−1</SUP>, respectively, while the <SUP>137</SUP>Cs activity ranged from 0.3 to 6.2 Bq kg<SUP>−1</SUP>. The mean activity ratios of <SUP>241</SUP>Am/<SUP>239,240</SUP>Pu and <SUP>238</SUP>Pu/<SUP>239,240</SUP>Pu in Porquerolles and Monaco sediments were similar to the global fallout ratios. Sediment inventories of global fallout <SUP>239,240</SUP>Pu (430–800 Bq m<SUP>−2</SUP>) and <SUP>241</SUP>Am (150–285 Bq m<SUP>−2</SUP>) were by about a factor of 5–10 higher at Porquerolles, whereas the inventory of <SUP>137</SUP>Cs (430–1000 Bq m<SUP>−2</SUP>) was substantially lower at the investigated stations than have been reported elsewhere at similar latitudes. Specific local conditions characterised by high OC sediment loads due to the growth and mortality of <I>Posidonia oceanica</I> have been responsible for deposition of large amounts of seagrass tissues at the NE corner of Porquerolles, which have had a profound effect on the distribution of radionuclides in the sediments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Radionuclides in coastal sediments of NW Mediterranean were investigated. </LI> <LI> <SUP>241</SUP>Am/<SUP>239,240</SUP>Pu and <SUP>238</SUP>Pu/<SUP>239,240</SUP>Pu ratios consistent with global fallout ratios. </LI> <LI> <SUP>137</SUP>Cs mostly dissolved, but <SUP>239,240</SUP>Pu and <SUP>241</SUP>Am are particle reactive elements. </LI> <LI> Inventories of <SUP>239,240</SUP>Pu (430–800 Bq m<SUP>−2</SUP>) and <SUP>241</SUP>Am (150–285 Bq m<SUP>−2</SUP>) are high. </LI> <LI> Inventories of <SUP>137</SUP>Cs are significantly lower at all stations investigated. </LI> </UL> </P>
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