Nuclear Science and Engineering

The NB/T 20018 standard does not provide a model for the Type B measurement uncertainty of the containment leakage rate. In order to perfect the theoretical model concerning the containment leakage rate within this standard and to further enhance its instructiveness in engineering experiments， a Type B uncertainty analysis model for the containment leakage rate has been proposed in this study. Firstly， based on the uncertainty theory in the JJF 1059 metrological standard， a theoretical model for Type B measurement uncertainty was developed for the containment leakage rate calculation formula specified in NB/T 20018. Subsequently， experiments were conducted with sensors deployed in a 1000m3 steel containment mock-up to validate the effectiveness of the model and to explore the factors influencing uncertainty. Furthermore， the uncertainty model proposed in this paper was utilized to analyze the pressure test data of the Hualong One containment， thereby verifying the accuracy of the theoretical model in engineering-scale tests. The research results indicate that the combined uncertainty calculated using the model proposed in this study is consistent with the combined uncertainty calculated using the standard method， with a relative deviation of only 6%. Type A uncertainty is found to be related to the gas state inside the containment and the duration of the test， while Type B uncertainty is associated with the uncertainty of the instruments and their quantity. The conclusions of this study can serve to provide theoretical support for the improvement of the NB/T 20018 standard and promote the independent development of containment sealing test technology.