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Feasibility study of detection of coolant void in liquid metal cooled fast reactors using changes in the neutron spectrum
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.ORCID iD: 0000-0002-3136-5665
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
2013 (English)In: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 265, 1255-1265 p.Article in journal (Refereed) Published
Abstract [en]

Formation of coolant void can lead to an increase in reactivity in metal-cooled fast reactors. Accordingly, the ability to detect formation of void and similar phenomena is highly relevant in order to counteract transient behaviour of such a reactor. As this work shows, the energy distribution of the neutron flux in a fast reactor is sensitive to formation of void. For monitoring purposes, this fact suggests the use of fission chambers with different isotopic content and thus different fission threshold energies. In such a way the monitoring system may be tailored in order to fit the purpose to obtain spectral information of the neutron flux.

In this work, simulations have been performed using the Monte-Carlo-based code SERPENT on the ELECTRA reactor design, a 0.5 MWth lead-cooled fast reactor (LFR) planned for in Sweden. The simulations show significant changes in the neutron spectrum due to the formation of void located in specific in-core regions as well as due to a homogeneous core-wide distribution of small bubbles. In an attempt to quantify and to put a number on the spectroscopic changes, the number of neutrons in the high energy region (2–5 MeV) are compared to the number of neutrons in the low-energy region (50–500 keV) and the changes caused by the introduction of void are analyzed. The implications of the findings are discussed.

Place, publisher, year, edition, pages
2013. Vol. 265, 1255-1265 p.
National Category
Subatomic Physics
Research subject
Applied Nuclear Physics; Physics with specialization in Applied Nuclear Physics
Identifiers
URN: urn:nbn:se:uu:diva-210980DOI: 10.1016/j.nucengdes.2013.10.015ISI: 000330085500127OAI: oai:DiVA.org:uu-210980DiVA: diva2:664924
Available from: 2013-11-18 Created: 2013-11-18 Last updated: 2017-12-06
In thesis
1. Development of a Methodology for Detecting Coolant Void in Lead-cooled Fast Reactors by Means of Neutron Measurements
Open this publication in new window or tab >>Development of a Methodology for Detecting Coolant Void in Lead-cooled Fast Reactors by Means of Neutron Measurements
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In a lead-cooled fast reactor (LFR), small bubbles (in the order of one mm or less) may enter the coolant from a leaking steam generator. If such a leakage is undetected the small bubbles may eventually coalesce into a larger bubble in local stagnation zones under the active core. If such a bubble or void releases and passes through the core, it could drive the reactor into prompt criticality. It is therefore desirable to be able to detect the initial stages of such void formation.

In this thesis, a methodology to detect such leaks is presented together with a study on void-induced reactivity effects in various LFR's. The methodology developed is based on information from two fission chambers positioned radially outside the core. The fissile content of the fission chambers consist either of 235U or 242Pu making them sensitive to different parts of the neutron spectrum. It is shown that the information from the fission chambers can be used to obtain an early indication of the presence of a small leak within typically a month. Furthermore, it is shown that for all but the smallest LFR’s, prompt criticality due to voids passing the core cannot be excluded.

One conclusion is that the methodology may form an attractive complement to the general monitoring system of future LFR’s but, as is noted, it has potential for further developments.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 54 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1180
Keyword
LFR, fission chamber, nuclear, reactor, leak, criticality
National Category
Energy Systems
Identifiers
urn:nbn:se:uu:diva-232252 (URN)978-91-554-9037-9 (ISBN)
Public defence
2014-10-31, room 2001, Lägerhyddsvägen 1, Ångströmslaboratoriet, Uppsala, 08:15 (English)
Opponent
Supervisors
Available from: 2014-10-08 Created: 2014-09-16 Last updated: 2015-01-23Bibliographically approved

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Wolniewicz, PeterHåkansson, AneJansson, PeterJacobsson Svärd, Staffan

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