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Development of delayed-neutron monitors for detection of fuel failure
Başlık:
Development of delayed-neutron monitors for detection of fuel failure
Yazar:
Mohamed, Mohamed Ibrahim, author.
ISBN:
9780438061040
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (183 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: J. Scobie.
Özet:
The objective of this work was to develop delayed neutron monitors for the detection of fuel failure and to assess their suitability for application on a reactor of UTR-type. For this purpose a failed Fuel Simulation rig has been constructed to simulate a reactor cooling system with a failed fuel element by circulating fission products from an irradiated uranium sample. The rig, which was installed on the top of the reactor, consisted of tubing with a total length approximately 18 metres, a reservoir, pump, flow-meter, valve, and source chamber. The latter was used to irradiate the uranium sample which was an electro-plated deposit of highly-enriched uranium containing a few milligrammes of uranium-235. The irradiation was done by installing the source chamber in front of the small thermal column in the shield tank of the UTR Reactor, at which position the thermal neutron flux was measured to be about 2 x 10e9 n/cm2-sec. The rig was designed so that the minimum transport time of the water from the source chamber to the monitor position, corresponding to the maximum flow-rate, was approximately the same as that for the UTR reactor coolant circuit. Also the reservoir hold-up time was similar to that for the reactor circuit. Based on the geometry of the arrangement the minimum transport time was calculated to be around 10 seconds, and later direct measurements of the arrival time of delayed neutron emitters gave values which agreed closely with this estimate. Monitoring of delayed neutrons was done using BF3 counters with suitable moderators. The efficiency of the counters was measured using an Am/Be neutron source with either water or wax as a moderator. Following these measurements three types of delayed neutron monitors were constructed. These were: a coil monitor with wax moderator, a water tank monitor with water moderator, and a mixed-bed resin monitor with a mixture of water and resin as a moderator. Several measurements were performed to test mainly the tank and resin monitor, and the results showed both monitors are sensitive to the signal due to a 0.5mm diameter hole, which was drilled in one face of a special uranium cell to simulate defective fuel. These results also showed that the resin monitor had a much higher sensitivity than that of either the tank or coil monitor, and for this reason it was suggested for use in the reactor of UTR type. In order to assess the feasibility of application of a resin monitor in the UTR reactor the prototype was installed in the process pit of the reactor so as to study background effects with the reactor in operation at full power. The results of this work showed that the high-energy gamma radiation from Nitrogen-16 in the reactor water has no significant effect or the detection sensitivity of the monitor. A small neutron signal was detected which varied with changes in the reactor water flow-rate, and was attributed to either or both of uranium surface contamination in the core or the neutron emitting isotope Nitrogen-17. An outline is given of a possible design of a fuel failure detection system for UTR-300 reactors based on this resin monitor. Also described in this work are some preliminary measurements on fission product deposition in the piping of the failed-fuel simulation rig.
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684872.1) | 684872-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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