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- Berglöf, Carl, et al.
(författare)
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Spatial and Source Multiplication Effects on the Area Ratio Reactivity Determination Method in a Strongly Heterogeneous Subcritical System
- 2010
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Ingår i: Nuclear science and engineering. - 0029-5639 .- 1943-748X. ; 166:2, s. 134-144
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Tidskriftsartikel (refereegranskat)abstract
- The area ratio method of Sjostrand is generally considered one of the most reliable reactivity determination methods and thus is a major candidate for off-line calibration purposes in future accelerator-driven systems for high-level waste incineration. In this work, the Sjostrand area ratio method has been evaluated experimentally under thorough conditions in the strongly heterogeneous subcritical facility YALINA-Booster. Both strengths and weaknesses of the method have been identified. Most surprisingly, it has been found that the area ratio reactivity estimates may differ a factor of 2 depending on detector position. It is also shown that this strong spatial dependence can be explained based on a simple two-region point-kinetics model and corrected by means of correction factors obtained through Monte Carlo simulations. A new Monte Carlo correction method is proposed that includes, at the same time, the spatial disturbance and the effective delayed neutron fraction. In that way, the value of the effective multiplication factor is obtained from the measured dollar reactivity without the need of calculating the effective delayed neutron fraction explicitly, and thereby, the delayed neutron transport is performed only once. Further, it has been found that the Sjostrand area ratio method is not sensitive to perturbations of the source multiplication factor.
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| 2. |
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| 3. |
- Fernandez-Ordonez, M., et al.
(författare)
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Reactivity determination techniques in ads systems for the incineration of radioactive wastes
- 2010
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Ingår i: International Conference on the Physics of Reactors 2010, PHYSOR 2010. - 9781617820014 ; , s. 2933-2945
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Konferensbidrag (refereegranskat)abstract
- The Subcritical Accelerator Driven Systems (ADS) have been proposed as one of the strategies for reducing the inventory and radiotoxicity of the spent nuclear fuel. The reactivity monitoring of ADS has been found to play a key role in the development of this technology. Although the current-to-power technique has been proposed as the main reactivity monitoring technique, it is necessary to periodically calibrate it using additional techniques. In this work, the standard reactivity monitoring techniques using Pulsed Neutron Source experiments have been evaluated in the coupled fast-thermal subcritical assembly YALINA-Booster. In addition, a new method to measure the absolute value of the system reactivity is proposed by using micro-interruptions of the continuous external neutron source (beam-trips). This technique, used for the first time in a subcritical core, provided results compatible with the standard PNS methods and can be used in future power ADS. Even more, to allow instantaneous reactivity checks, we have developed and tested the necessary electronic chains and data acquisition system to determine the system reactivity during a single beam trip, thus allowing the determination of the reactivity within a second.
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