Testing of Inductively Coupled Eddy Current Position
Sensor of Diverse Safety Rod in Sodium
R. Vijayashree, R. Veeraswamy, B. K. Nashine, S. K. Dash, Prashant Sharma, K. K. Rajan, G. Vijayakumar,
C. Babu Rao, S. Sosamma and P. Kalyanasundaram
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I. INTRODUCTION
rototype Fast Breeder Reactor (PFBR) which is currently
under advanced stage of construction is U-Pu oxide fuelled
sodium cooled fast reactor. In order to control the power and
also shutdown the reactor , nine numbers of Control and Safety
Rods are used. To improve the reliability of shutdown, three
numbers of Diverse Shutdown Rod (DSR) are used [1]. During
normal operation, DSRs are held above the active fuel zone by
an electromagnet housed in Diverse Safety Rod Drive
Mechanism (DSRDM). On receiving SCRAM (Safety and
Control Rod Acceleration Movement) signal, the electromagnet
de-energizes and drops the DSR, which falls under gravity. DSR
gets decelerated after traveling free-fall distance and then
rests at bottom most position [2]. Eddy Current Position Sensor
Manuscript received May 20, 2011.
R. Vijayashree, R. Veeraswamy, B.K. Nashine, S.K. Dash, Prashant Sharma,
K.K.Rajan, G. Vijayakumar, C. Babu Rao, S. Sosamma, P. Kalyanasundaram
are with the Indira Gandhi Centre for Atomic Research, Department of Atomic
Energy, Kalpakkam - 603 102, India
E-mail: rviji@igcar.gov.in
(ECPS) has been conceptualized [3] to detect whether the DSR
has reached its bottom most deposited position or not and to find
out free fall time of DSR. A model ECPS set up with actual
geometrical dimension of DSR sub- assembly was designed and
fabricated for sodium testing. This paper deals with the
development testing of ECPS in sodium
II. DESIGN CONSTRAINT AND PRINCIPLE
The design of such a sensing system is governed mainly by
the fact that no electrical connection can be brought out from the
core subassemblies and by the space constraints. Since it is not
possible to have electrical connectivity with in-core
components, an indirect excitation through inductive coupling
has been conceptualized. A primary coil located in DSRDM is
excited by an AC source. The secondary coil is located in the
DSR sheath. The secondary coil, excited by the primary, acts as
exciting source for the sensor suitably placed at the bottom of
the DSR subassembly. When the DSR is dropped, the sodium in
the DSR subassembly is displaced by DSR and the
ferromagnetic piston of the DSR comes in the sensor coil center
location. This causes a change in the inductance of the sensor
coil which can be used to detect the position of the DSR and so
the free fall time of DSR.
P
Fig.1 Schematic of ECPS
978-1-4577-0927-2/11/$26.00 ©2011 IEEE