Page 272 - 00. Complete Version - Progress Report IPEN 2014-2016

272 Nuclear Reactors and Fuel Cycle | Progress Report

Development of a new fuel element Experimental Analysis of Critical
“Dummy” (Pressure and Flow Velocity in Flat Plate Fuel Element
Measurement Device DMPV 2 for Nuclear Research Reactors

In the early 2000s CEN, in partnership with The fuel elements of a MTR (Materi-
the CCN, designed and built a DUMMY Fuel al Testing Reactor) type nuclear reactor are
Element for Pressure and Flow Measurement mostly composed of aluminum-coated fuel
(DMPV-1), which allowed a better understand- plates containing the core of uranium sili-
ing of the flow distribution in the IEA-R1 re- ca (U3Si2) dispersed in an aluminum matrix.
actor core and in the Cooling channels of the These plates have a thickness of the order of
fuel elements. millimeters and are much longer in relation
to their thickness. They are arranged in paral-
Based on the results obtained with the DMPV- lel in the assembly forming the fuel element
1, once again CEN, in partnership with the channels through which there is a flow of the
CCN, is initiating the design and construc- coolant (light water or heavy water). This con-
tion of a new DUMMY fuel element (DMPV- figuration, combined with the need for a flow
2) with the aim of proposing simple modifi- at high flow rates to ensure the cooling of the
cations to the fuel elements of the IEA- R1, in fuel element in operation, may create problems
order to improve the cooling conditions of the of mechanical failure of fuel plate due to the
fuel elements and, thus, improve the safety of vibration induced by the flow in the channels.
the IEA-R1 reactor. In the case of critical velocity, it may cause col-
lapse of the plates. Although there is no rup-
Modernization of the reactor ture of the fuel plates during collapse, exces-
control table IPEN / MB-01 sive permanent deflections of the plates can

cause blockage of the flow channel in the reac-
tor core and lead to overheating in the plates.
For this study, an experimental bench and a
test section that simulates a plate-like fuel ele-
ment with three cooling channels were devel-
oped. The test section was constructed with
aluminum and acrylic plates and was instru-
mented with strain gauge sensors, pressure
Figure 26. Digital system for control rod drive.
sensors, accelerometer and a tube of pitot. The
This line of development aims to modernize dimensions of the test section were based on
some of the subsystems of the IPEN / MB-01 the dimensions of the designed fuel element of
reactor that have become obsolete and diffi- the Brazilian Multipurpose Reactor (RMB). The
cult to maintain, making them suitable for the experiments performed attained the objective
advent of the design of the core exchange of of reaching Miller’s critical velocity condition
rods with the fuel elements of the type Plate, with the collapse of the plates. The critical ve-
providing adaptability to new experiments locity was reached with 14.5 m/s leading to the
through its intrinsic reprogramming capabil- consequent plastic deformation of the plates
ity, within the highest nuclear safety require- forming the flow channel. The central chan-
ments. It consists in to develop a new digital nel had a 3mm aperture in its center, causing
system for control rod drive. a large blockage of the flow in the lateral chan-

Instituto de Pesquisas Energéticas e Nucleares