| 1. |
- Saygin, Hasan, et al.
(författare)
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A Comparison Between the Results of Perturbation Theory and TRIGAP for the Reactivity Worth Calculations of Fuel Elements
- 1998
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Ingår i: Annals of Nuclear Energy. - 0306-4549 .- 1873-2100. ; 25:14, s. 1133-1140
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Tidskriftsartikel (refereegranskat)abstract
- Reactivity worth of the fuel elements of I.T.U. TRIGA MARK-IIreactor are calculated by using both one-group perturbation theory and a one dimensional, two-group diffusion computer code, TRIGAP. Results of both methods are compared with those measured experimentally. Although the perturbation theory is obtained from the diffusion theory by making some assumptions, it is seen that one-group perturbation theory gives the results with better accuracy in comparison to the results of TRIGAP. This situation shows that TRIGAP cannot reflect the effect of local material changes on the multiplication factor well enough. In order to calculate fuel elements reactivity worth of TRIGA type reactors, one-group perturbation theory can be preferred to TRIGAP due to its simplicity and accuracy, when the flux and group constants are known.
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| 2. |
- Borgenstam, Annika, et al.
(författare)
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Driving force for f.c.c.→b.c.c. martensites in Fe-X alloys
- 1997
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Ingår i: Acta Materialia. - 1359-6454 .- 1873-2453. ; 45:5, s. 2079-2091
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Tidskriftsartikel (refereegranskat)abstract
- Information on Ms, the starting temperature for formation of martensite, is reviewed and one Ms line each for lath and plate martensite are drawn in a number of Fe-X phase diagrams. A reasonable interpretation of the data indicates the possibility that the distance between the two lines may vary linearly with temperature and be independent of the choice of alloying element. Using thermodynamic descriptions of the binary systems, the driving force for the start of the formation of the two kinds of martensite is calculated from the same interpretation of data. When plotted against temperature the results indicate that the driving force for martensite may not be much affected by solution hardening but may mainly be a function of temperature. For plate martensite it may have a fairly constant value of about 2100 J/mol. For lath martensite it may vary linearly, possibly from 500 J/mol at 800°C to 2100 J/mol at 250°C.
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