Om Pal Singh

Energetics of core disruptive accident for different fuels for a medium sized fast reactor

Abstract A comparative study has been made on the mechanical energy released in a core disruptive accident resulting from an unprotected loss of flow accident (LOFA) in a medium sized liquid metal fast breeder reactor with oxide, carbide and metal fuels. The study is conducted by ignoring the passive safety features incorporated in the design so that the accident scenario culminates in an energetic disassembly of the core with large energy release. The paper further provides the salient features of the analysis and presents the results with suitable physical explanations.

Leak noise detection and characterisation using statistical features

Abstract Covariance Matrix based statistical features have been used to detect leak, identify noise source and characterise noise transmission off-line on data from PFR Steam Generator Units. The methods show promise in their ability to detect leak in actual Steam Generator Units from the noise data with very low S/N ratios. Further analysis of data have yielded useful information on the potential of acoustic leak detection system.

New statistical features sensitive to sodium boiling noise

Abstract New statistical features sensitive to Na boiling noise have been constructed. The features have been tested on Na boiling noise data of a BOR-60 experiment. It is found that the determinant of the covariance matrix of N judiciously selected segmented areas under the power spectral density curve, is the most sensitive feature for Na boiling noise.

A multivariate pattern recognition analysis of BOR-60 sodium boiling noise data

Abstract Na boiling noise data from a BOR-60 reactor have been analyzed by a multivariate pattern recognition technique. The results of the analysis have been compared with the results obtained by individual features. The merit of the technique is judged by finding the time of onset of boiling with the required probability of missing the boiling detection and the spurious boiling detection. The multivariate pattern recognition method is found to detect the boiling more clearly and with better reliability.

New approaches in signal processing technique for sodium boiling noise detection

Abstract The paper deals with the investigations carried out on signal processing techniques for developing a suitable pattern recognition method for sodium boiling noise detection in liquid metal fast breeder reactors. The investigations are particularly related with the suitable feature selection, threshold selection and evaluation of the quality of the signal processing techniques in terms of their capability in detecting sodium boiling with desired probabilities of spurious boiling and missing the boiling detection. The methods evolved have been tested on available experimental data.

New statistical features for sodium boiling and leak noise detection in liquid metal fast breeder reactors under poor signal-to-noise ratio conditions

Abstract New statistical features have been constructed and tested for detecting sodium boiling noise and leak noise in liquid metal fast breeder reactors under poor signal-to-noise (S/N) ratio conditions. It has been established that the new features are more sensitive than the conventional features and detect sodium boiling noise with better discrimination for noise data with a S/N ratio of − 12 dB and for leak noise data with a S/N ratio of − 6.7 dB. The sensitivity of the newly invented features for leak noise with further deteriorated S/N ratio conditions is to be tested further.

Influence of a positive sodium void coefficient of reactivity on the consequences of transient overpower and loss-of-flow accidents in a medium-sized fast reactor

Abstract Results are reported for the dynamic analysis of protected as well as unprotected transient overpower and loss-of-flow accidents for a medium-sized liquid metal fast breeder reactor (LMFBR) fuelled with oxide, carbide and metal cores. It is concluded that the safety of the reactor is not materially affected by the sodium void coefficient of reactivity. Hence, design variants aimed to make the sodium void coefficient negative and involving economic penalties may not be justified for a medium-sized LMFBR.

Response to small reactivity perturbations in an oxide and metal fuelled medium-sized liquid-metal fast breeder reactor

Abstract The response to small reactivity perturbations of a medium-sized (500 MWe power) liquid-metal fast breeder reactor with oxide and metal fuel, has been studied using frequency and time domain analyses. The study indicates that the metal fuelled core is more sensitive to small reactivity perturbations than the oxide fuelled core. However, both cores satisfy the linear stability criteria for such reactivity perturbations. The methodology used and details of the results are presented. The frequency range of the effectiveness of certain reactivity feedbacks responsible for passive safety in the reactor is also indicated.

The angular dependence of neutron-noise transmission through shields in LMFBRs

Abstract This note deals with the angular dependence of neutron-noise transmission through shields in LMFBRs. The results are presented in particular, on the angle dependence of the APSD of the angular neutron-noise flux. It is observed that the larger the angle of the neutron-noise flux, the greater the break frequency of the corresponding APSD.

Analysis of passive shutdown capability for a loss of flow accident in a medium sized liquid metal fast breeder reactor

Abstract Passive shutdown capability of a medium sized (500 MWe) liquid-metal fast breeder reactor with oxide, carbide and metal fuels has been analysed for a loss of flow accident using static and dynamic analysis methods. The carbide fuel is assumed to be He-bonded as well as Na-bonded. The dependence of the passive safety on flow halving time constant of the loss of flow incident and the feedback components like radial core expansion due to subassembly spacer pad heating and differential control rod expansion due to heating of the control rod suspension mechanism is highlighted.