RRFM 2009 Transactions - European Nuclear Society

DESIGN OF A FLOWING-NAK EXPERIMENTAL DEVICE FOR IN-
CORE MATERIAL IRRADIATION IN THE JULES HOROWITZ
REACTOR
Damien MOULIN, Christine BISCARRAT, Sébastien CHRISTIN, Guy LAFFONT,
Aurélien MORCILLO, Eric PLUYETTE, Frédéric REY
CEA, DEN, Department of Nuclear Technology,
F-13108 Saint-Paul-Lez-Durance, France.
ABSTRACT
One of the characteristics of the Jules Horowitz Reactor will be its very high fast
neutron flux. To take benefits of these irradiation locations, a specific test device
called CALIPSO is under development. The accurate temperature control of the
samples is possible by the mean of a small in-pile loop of circulating NaK.
Progresses on designing the CALIPSO device have been made concerning its
operating range and its main components such as the electromagnetic pump, the
electrical heater and the heat exchanger. The overall dimensions of the tubes have
been defined according to the safety requirements. The present design of
CALIPSO provides a large operating range regarding to nuclear heating values
and NaK temperature while keeping homogeneous the temperature distribution
around the samples.
1. Introduction
The Jules Horowitz Reactor (JHR) is under construction in the CEA’s Cadarache centre in
the south of France. It will be mainly dedicated to study material and fuel behaviour under
irradiation for the benefits of existing nuclear plants as well as the development of the future
reactors (1).
One of the characteristics of the JHR is its very high fast neutron flux providing irradiation
possibilities that will be quite unique among the existing Material Testing Reactors (2).
To take benefits of these irradiation locations, a specific test device was designed: initially
known as “M3” in its definition phase (3), it has been named CALIPSO since the beginning of
its development phase. As summarized in its acronym it is an in-Core Advanced Loop for
Irradiation in Potassium Sodium (NaK) coolant.
After a short presentation of the JHR in-core experimental locations, this paper will give the
operating principle, then the design of the main components will be detailed in accordance to
the operating constraints and the safety requirements.
2. In-core experimental locations
Operating at 100 MWth the JHR core is composed of 34 fuel elements. Each fuel element is
composed of 3 zones of 8 curved plates leaving a central hole. The total fissile length is
60 cm-long and the core is inserted in a 74 cm-diameter pressurized vessel.
Several experimental locations are available in the centre of fuel elements and some others
by replacing fuel elements (4).
Standard in-fuel element experimental locations are characterized by very high fast neutron
flux (E>1 MeV) reaching 5.10 14 n.cm -2 .s -1 at full power in the core mid-plane. These are very
efficient to perform experiments such as dose accumulation for cladding and structural
materials (displacement per atom rate ~15 dpa/year). The counter part of such high fast
neutron flux, is very high gamma and fast neutrons heating in materials, reaching about
20 W/g in steel. It is also important to highlight the small available space for the device part
located in the fissile zone: maximal outer diameter ~ 33 mm.
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