No abstract

Different parameters should be monitored at a nuclear facility. Among them, water used in a nuclear reactor must meet strict specifications. The research reactor Argonauta, located in Rio de Janeiro, uses light water as both moderator and coolant. Quality control is the set of measurements to ensure, at any time, products that meet the parameters and standards in force. Then, the quality control of Argonauta’s water encompasses physical-chemical and radiological tests that are performed periodically to monitor deviations in the water parameters specification. These tests include the measurement of pH, conductivity, and gamma spectroscopy. By means of these tests, it is possible to evaluate if the quality parameters of this water meet the requirements defined by the reactor manufacturer and the Radiation Protection standards.  In this way, the safe operation of the Argonauta is guaranteed, besides avoiding unwanted exposures of operators and the environment to the ionizing radiation. This work presents the detailed assays performed in the water quality control. In addition, the obtained results in the last year measurements and highlights of the improvements to be done are also addressed. Moreover, a comparison among other research reactors in Brazil concerning this monitoring is presented. The obtained results indicate that pH, conductivity, and radiological parameters meet the established limits.

The NaI(Tl) detector is one of the most used in gamma ray spectrometry because it presents high counting efficiency for gamma rays in a wide range of energy. The crystal can have a lower efficiency that can be indicated by the effects of its aging by several factors such as: the reaction of sodium iodide with magnesium oxide, absorption of water vapor by crystal, and problems related to photomultiplier. In an experiment, several measures can be take and when a doubt exists between one of the measured values it is possible to use a statistical test. Grubbs test is designed to verify the presence of extreme values in sample observations. This paper presents a methodology that has the objective of evaluating the homogeneity of a NaI(Tl) scintillation detector using the Grubbs test to validated the crystal homogeneity. The study pre-established five differents locations in frontal area of detector where measurements were performed using a 137Cs standard source in order to calculate the standard deviation.