Thermal study of a non adiabatic differential calorimeter used for nuclear heating measurements inside an experimental channel of the Jules Horowitz Reactor

Abstract

Abstract. New online in-pile measurement methods are crucial during irradiations in Material Testing Reactors (MTR) for a better understanding of accelerated material ageing and nuclear fuel behaviour. In particular, instrumentation for measurements of one relevant parameter: nuclear heat deposition rate, called nuclear heating, has to be improved. The knowledge of this quantity is a great interest for various safety, scientist and end-user requirements (design of specific irradiation devices and associated cooling systems with imposed conditions). This paper focuses on thermal experimental and numerical studies carried out under non irradiation conditions on an in-pile calorimeter dedicated to nuclear heating quantification inside a new experimental device which will be dedicated to the experimental condition mapping (neutron and photon fluxes and nuclear heating) inside the JHR experimental channels. Experimental results concerning the calorimeter response during its electrical calibration (<3W) under laminar forced convection conditions show that its sensitivity does not depend on the cooling flow. Temperature and heat flux density measurements lead to the conclusion of a good directional conductive heat flow design (increased with a higher Reynolds number). A parametric numerical stationary study highlights a sensor sensitivity increasing. At last, the usual calorimeter design is compared to a single calorimeter which gives promising results (miniaturization, higher sensitivity).

Review of CALORRE Calorimeter Characterizations Under Laboratory and Irradiation Conditions

“…Consequently, the response of each calorimeter cell is induced by the power deposited inside its head which is proportional to the nuclear heating rate. In the case of the measurement cell the deposited power 𝑃 𝑆 is given by: 𝑃 𝑆 = 𝑃 ℎ𝑒𝑎𝑑 + 𝑃 𝑠ℎ𝑖𝑚 + 𝑃 𝑠𝑎𝑚𝑝𝑙𝑒−ℎ𝑜𝑙𝑑𝑒𝑟 + 𝑃 ℎ𝑒𝑎𝑡𝑒𝑟 + 𝑃 𝑠𝑎𝑚𝑝𝑙𝑒 = (𝑚 1 + 𝑚 𝑠𝑎𝑚𝑝𝑙𝑒 )𝐸 𝑛 (3) with m1 the total mass corresponding to the head, shim, sample-holder, heater for the measurement cell, msample the sample mass.…”

“…The online measurement of this latter quantity requires specific sensors: non-adiabatic calorimeters. With regard to the state of the art, two distinct sensors are used in MTRs: French differential calorimeters (CALMOS, CARMEN or CALORRE type) [3][4][5][6][7][8] or single-cell calorimeters (such as gamma thermometers or KAROLINA-type calorimeters) [9][10][11][12][13][14][15]. These two types of calorimeter allow the quantification of the nuclear absorbed dose rate thanks to temperature measurements and preliminary calibration under non-irradiation conditions from steady thermal states in the case of integrated heating elements or from transient thermal states in other cases.…”

State of the art on nuclear heating measurement methods and expected improvements in zero power research reactors

“…This energy is transferred to the electrons through neutral particle interactions, and finally deposited in the material. In ZPR, the very low operating power (typically of the order of 100 W) does not allow nuclear heating to be directly determined in W g À1 through temperature measurement (calorimetry) [1,2]. Thus, experimental techniques usually used for this kind of measurements, such as photographic films, semiconductor diodes, luminescent dosimeters, etc., are based on the quantification of the energy deposited per unit mass (absorbed dose) in the material of interest subjected to ionizing radiation (photons, neutrons, charged particles).…”

Responses of Single-Cell and Differential Calorimeters: from Out-of-Pile Calibration to Irradiation Campaigns.

“…The experiments involve the study of the sensor response to different imposed internal and external conditions by means of special testing benches, such as the ThermoHYdraulic test Bench (BETHY), which simulates specific thermal and hydraulic conditions pertaining to the smallest in-core JHR channel to test differential calorimeters [22], or the Polish bench, which reproduces these conditions for the MARIA reactor [7], and/or by the use of sensor prototypes [18]. The thermal numerical simulations are dedicated to carrying out parametric studies in order to improve knowledge of sensor behavior, to enhance and adapt the metrological characteristics of existing sensors, and to design new sensor configurations with new specific properties [23,24]. The modeling of interactions between nuclear radiation and matter is used to interpret experimental data (in particular to assess the contribution of neutrons and prompt and delayed photons to the nuclear energy deposition rate) or in addition to perform parametric studies [25].…”