ISSN Online: 2377-424X
International Heat Transfer Conference 12
Analysis of axisymmetric heat conduction pertaining to a new axial power monitor for nuclear reactors
Sinopsis
A new type of axial power monitor (APM) for nuclear reactors was recently tested in a laboratory under
electrical heating in two different modes, 1) passing an electric current through its bulk ("Joule heating") and 2)
passing an electric current through a heating wire along its axis ("internal heating"). The test results showed
good agreement between the thermocouple voltages for the two heating modes. However, a physical
explanation for the good agreement was missing and the applicability of the test results to reactor operation,
whereby the heating is due to gamma and neutron irradiation ("gamma heating"), needed to be examined.
Earlier investigations provided a physical explanation for the good agreement of the above test results as well as
insight into the axisymmeric heat conduction in the "hot zone" of an APM sensor segment. However, the effects
of non-uniform heat flux at the recess surrounding a "hot zone" on the important temperature differentials
remained to be investigated. In the present paper, axisymmetric heat conduction in the "hot zone" of an APM
sensor segment is investigated, assuming a parabolic radial heat flux at the recess, the radial heat flux being
maximum at the hottest cross section (plane of symmetry of the "hot zone") and decreasing to a negligible value
at the coldest cross section (end of the "hot zone"). For both "internal heating" and "gamma/Joule heating", the
partial differential equations for axisymmetric heat conduction under the new boundary conditions at the recess
were solved. The new results show small deviations from those of the earlier investigations.