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Optimisation and evaluation of boron analysis for pressurized Water reactor plants
Author(s)
Tasana, Nomalanga Gloria
Date Issued
2016
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
Boron concentration analysis is an important and critical analysis performed by the Analytical
Chemistry Laboratory at Koeberg Nuclear Power Station (KNPS), because boron controls
reactivity and the concentration determination is a Technical Specification Parameter (safety
parameter). Hence accurate, precise results for boron concentration produced by
laboratories and on-line analysers are important because of their operational implications
associated with reactivity control and also for nuclear safety.
The project focused on comparing the quality of chemical analysis results of boron produced
by analysis techniques/ methods used at Koeberg Nuclear Power Station namely;
Potentiometric Titration, Atomic Absorption Spectrophotometry (Flame) and UV-VIS
Azomethine-H method. The methods were described, optimised, evaluated and compared in
terms of uncertainty of measurement, accuracy, precision, analysis range, limitations,
appropriateness and applicability for boron analysis in 2500 mg B/kg concentration range.
For Potentiometric Titration method, the measurement uncertainty = 2500 ±16 mg B/kg,
accuracy= 0.2%, precision= 0.08% the range of analysis= 5-800 mg B/kg. For Atomic
Absorption Spectrophotometry (Flame) the measurement uncertainty= 2500 ±51 mg B/kg,
accuracy= 0.12%, precision= 0.44% the range of analysis= 0 -500 mg B/kg. For UV-VIS
Azomethine-H the measurement uncertainty= 2500 ±72 mg B/kg, accuracy= 0.08%,
precision= 0.44% the range of analysis= 0 -10 mg B/kg. The INPOs 95% accuracy and
precision criteria for boron is ± 1%. So these techniques could be used for boron analysis in
PWR. Based on the evaluation and assessments mentioned above; the Potentiometric
Titration was found to be the most preferred method for boron analysis for Pressurised Water
Reactors followed by Atomic Absorption Spectrophotometry (Flame) that can be of good use
in determining boron especially in waste samples and samples with complex matrices. The
UV-VIS Azomethine-H methods can only be used when it is really necessary to determine
very low levels of boron between 0- 10mg B/kg of which it was never required before. Since it is specifically the B-10 isotope that is responsible for the ability to control reactivity,
the implementation of isotopic boron analysis (by Inductively Coupled Plasma – Mass
Spectrometry) at KNPS is explained and the advantage of the programme is illustrated.
Although the current state of instrumental capabilities is adequate for 10B isotope
determination, further work of optimising the methodology for even better results is
recommended.
Chemistry Laboratory at Koeberg Nuclear Power Station (KNPS), because boron controls
reactivity and the concentration determination is a Technical Specification Parameter (safety
parameter). Hence accurate, precise results for boron concentration produced by
laboratories and on-line analysers are important because of their operational implications
associated with reactivity control and also for nuclear safety.
The project focused on comparing the quality of chemical analysis results of boron produced
by analysis techniques/ methods used at Koeberg Nuclear Power Station namely;
Potentiometric Titration, Atomic Absorption Spectrophotometry (Flame) and UV-VIS
Azomethine-H method. The methods were described, optimised, evaluated and compared in
terms of uncertainty of measurement, accuracy, precision, analysis range, limitations,
appropriateness and applicability for boron analysis in 2500 mg B/kg concentration range.
For Potentiometric Titration method, the measurement uncertainty = 2500 ±16 mg B/kg,
accuracy= 0.2%, precision= 0.08% the range of analysis= 5-800 mg B/kg. For Atomic
Absorption Spectrophotometry (Flame) the measurement uncertainty= 2500 ±51 mg B/kg,
accuracy= 0.12%, precision= 0.44% the range of analysis= 0 -500 mg B/kg. For UV-VIS
Azomethine-H the measurement uncertainty= 2500 ±72 mg B/kg, accuracy= 0.08%,
precision= 0.44% the range of analysis= 0 -10 mg B/kg. The INPOs 95% accuracy and
precision criteria for boron is ± 1%. So these techniques could be used for boron analysis in
PWR. Based on the evaluation and assessments mentioned above; the Potentiometric
Titration was found to be the most preferred method for boron analysis for Pressurised Water
Reactors followed by Atomic Absorption Spectrophotometry (Flame) that can be of good use
in determining boron especially in waste samples and samples with complex matrices. The
UV-VIS Azomethine-H methods can only be used when it is really necessary to determine
very low levels of boron between 0- 10mg B/kg of which it was never required before. Since it is specifically the B-10 isotope that is responsible for the ability to control reactivity,
the implementation of isotopic boron analysis (by Inductively Coupled Plasma – Mass
Spectrometry) at KNPS is explained and the advantage of the programme is illustrated.
Although the current state of instrumental capabilities is adequate for 10B isotope
determination, further work of optimising the methodology for even better results is
recommended.
Additional information
Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016
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