Assessment of the reliability of neutronic parameters of Ghana Research Reactor-1 control systems

• Published in: Nuclear engineering and design Vol. 281; pp. 72 - 78
• Main Authors: Amponsah-Abu, E.O., Gbadago, J.K., Akaho, E.H.K., Akoto-Bamford, S., Gyamfi, K., Asamoah, M., Baidoo, I.K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2015
• Subjects: Chambers; Control systems; Fluxes; Measuring instruments; Meters; Nuclear engineering; Nuclear power generation; Nuclear reactor components; Nuclear reactors
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2014.11.018

•The reliability of neutronics parameters of GHARR-I was assessed.•The reactor was operated at different power levels of 5–30kW.•The pre-set flux was compared with the flux in the inner irradiation site.•Decrease in the core reactivity caused difference in flux on the meters and site.•Neutronic parameters become reliable when operation is done at reactivity of 4mk. The Ghana Research Reactor-1 (GHARR-1) has been in operation for the past 19 years using a Micro-Computer Closed Loop System (MCCLS) and Control Console (CC) as the control systems. The two control systems were each coupled separately with a micro-fission chamber to measure the current pulses of the neutron fluxes in the core at excess reactivity of 4mk. The MCCLS and CC meter readings at a pre-set flux of 5.0×1011n/cm2s were 6.42×1011n/cm2s and 5.0×1011n/cm2s respectively. Due to ageing and obsolescence, the MCCLS and some components that control the sensitivity and the reading mechanism of the meters were replaced. One of the fission chambers was also removed and the two control systems were coupled to one fission chamber. The reliability of the neutronic parameters of the control systems was assessed after the replacement. The results showed that when the reactor is operated at different power levels of 5–30kW using one micro-fission chamber, the pre-set neutron fluxes at the control systems is 1.6 times the neutron fluxes obtained using a flux monitor at the inner irradiation site two of the reactor. The average percentage deviations of the obtained fluxes from the pre-set values of 1.67×1011–1.0×1012n/cm2s were 36.5%. This compares very well with the decrease in core excess reactivity of 36.3% of the nominal value of 4mk, after operating the reactor at critical neutron flux of 1.0×109n/cm2s.