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RISS 인기검색어
- 검색키워드
- 저자 : D. C. Groeneveld (검색결과 3 건)
- 무료
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Overview of methods to increase dryout power in CANDU fuel bundles
Groeneveld, D.C.,Leung, L.K.H.,Park, J.H. Elsevier 2015 Nuclear engineering and design Vol.287 No.-
<P><B>Abstract</B></P> <P>In CANDU reactors some degradation in the CCP (critical channel power, or power corresponding to the first occurrence of CHF in any fuel channel) will occur with time because of ageing effects such as pressure-tube diametral creep, increase in reactor inlet-header temperature, increased hydraulic resistance of feeders. To compensate for the ageing effects, various options for recovering the loss in CCP are described in this paper. They include: (i) increasing the bundle heated perimeter, (ii) optimizing the bundle configuration, (iii) optimizing core flow and flux distribution, (iv) reducing the bundle hydraulic resistance, (v) use of CHF-enhancing bundle appendages, (vi) more precise experimentation, and (vii) redefining CHF. The increase in CHF power has been quantified based on experiments on full-scale bundles and subchannel code predictions. The application of several of these CHF enhancement principles has been used in the development of the 43-rod CANFLEX bundle.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Small changes in bundle geometry can have noticeable effects on the bundle CHF. </LI> <LI> Rod spacing devices can results in increases of over 200% in CHF. </LI> <LI> CHF enhancement decays exponentially downstream from spacers. </LI> <LI> CHF-enhancing bundle appendages also increase the post-CHF heat transfer. </LI> </UL> </P>
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Gallagher, S.J.,Reuning, L.,Himmler, T.,Henderiks, J.,De Vleeschouwer, D.,Groeneveld, J.,Rastegar Lari, A.,Fulthorpe, C.S.,Bogus, K.,Renema, W.,McGregor, H.V.,Kominz, M.A.,Auer, G.,Baranwal, S.,Casta& Elsevier 2018 Quaternary science reviews Vol.200 No.-
<P><B>Abstract</B></P> <P>Marine ooids are iconic indicators of shallow seawater carbonate saturation state, and their formation has traditionally been ascribed to physicochemical processes. The Indo-Pacific stands out as a region devoid of oolites, particularly during the Quaternary: the “ooid enigma”. Here we present results from recent coring by the International Ocean Discovery Program (IODP Expedition 356) off west Australia that shows that ooid horizons are common in Pleistocene strata up to 730,000 years old. Extensive “ooid factories” were created due to the presence of long-lived tidally influenced flat–topped tropical platforms suitable for intermittent ooid accretion over hundreds to thousands of years during highstands and times of lower sea level. This work suggests marine ooids may actually be more common in Indo-Pacific than previously reported. Past global ocean alkalinity was elevated during Pleistocene glacial periods and continental climate was generally more arid in the Indo-Pacific region compared to interglacials and the Holocene. Therefore, increased aridity associated with higher alkalinity conditions during the glacials facilitated ooid precipitation on adjacent tropical carbonate platforms particularly offshore from arid Australia. This confluence of factors suggests that more “ooid factories” may be encountered by further coring Indo-Pacific regions with Pleistocene flat long-lived carbonate shelves. However, Indo-Pacific Quaternary ooid occurrences outside Australia are rare, suggesting that the Northwest Shelf may be a unique archive of this non-skeletal precipitate. Further investigations into the petrography and geochemistry of pre-Holocene ooid occurrences will provide insights into their origin and the relative role of biotic, physicochemical and other factors in their formation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oolites are rare in the Indo-Pacific, particularly during the Quaternary: the “ooid enigma”. </LI> <LI> IODP Expedition 356 off west Australia cored common ooid horizons in strata up to 730,000 years old. </LI> <LI> Extensive “ooid factories” were deposited on tidally influenced flat–topped tropical platforms. </LI> <LI> Oolites were deposited during low and high sea levels in generally arid conditions. </LI> <LI> More “ooid factories” may be found by coring regions with flat long-lived carbonate shelves. </LI> </UL> </P>
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