Measurements of the isothermal, power and temperature reactivity coefficients of the IPR-R1 TRIGA reactor

• Published in: Progress in nuclear energy (New series) 2011-11, Vol.53 (8), p.1126-1131
• Main Authors: Souza, Rose Mary Gomes do Prado, Mesquita, Amir Zacarias
• Format: Article
• Language: English
• Subjects: Applied sciences; Brazil; Coolants; Cooling systems; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Isothermal coefficient; Nuclear engineering; Nuclear fuels; Nuclear power generation; Nuclear reactor components; Nuclear reactors; Power coefficient; Power defect; Preparation and processing of nuclear fuels; Steady state; Temperature coefficient; TRIGA research reactor
• ISSN: 0149-1970
• DOI: 10.1016/j.pnucene.2011.06.010

The aim of this paper is to present the experimental results of the isothermal, power and temperature coefficients of reactivity of the IPR-R1 TRIGA reactor at the Nuclear Technology Development Center – CDTN in Brazil. The measured isothermal reactivity coefficient, in the temperature range measured, was −0.5 ¢/°C, and the reactivity measurements were performed at 10 W to eliminate nuclear heating. The reactor forced cooling system was turned off during the measurements. When the reactor is at zero power there is no sensible heat being released in the fuel, and the entire reactor core can be characterized by a single temperature. The power coefficient of reactivity obtained was approximately −0.63 ¢/kW, and the temperature reactivity coefficient of the reactor was −0.8 ¢/°C. It was noted that the rise in the coolant temperature has contributed only with a small fraction to the observed negative effect of the reactivity. The power defect, which is the change in reactivity taking place between zero power and full power (250 kW), was 1.6 $. Because of the prompt negative temperature coefficient, a significant amount of reactivity is needed to overcome temperature and allow the reactor to operate at the higher power levels in steady state. ►Experiments were done in the TRIGA reactor at CDTN/CNEN in Brazil. ►It was found that isothermal reactivity coefficient is negative. ►It was found the power and the temperature reactivity coefficients. ►Coolant temperature contributed with small fraction to negative reactivity effect. ►Then the fuel power coefficient of reactivity is the main contributor of it.