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Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
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What’s in your Dubai chocolate? Nuclear scientists test pistachios for toxins
For the uninitiated, Dubai chocolate is a candy bar filled with pistachio and tahini cream and crispy pastry recently popularized by social media influencers. While it’s easy to dismiss as a viral craze now past its peak, the nutty green confection has spiked global pistachio demand, and growers and processors are ramping up production. That means more pistachios need to be tested for aflatoxins—a byproduct of a common crop mold.
M. J. Ohanian, P. B. Daitch
Nuclear Science and Engineering | Volume 19 | Number 3 | July 1964 | Pages 343-352
Technical Paper | doi.org/10.13182/NSE64-A20967
Articles are hosted by Taylor and Francis Online.
Numerical solutions of the time-dependent thermalization problem in infinite 1/ν poisoned media as well as in finite media in the diffusion approximation have been obtained using an eigenfunction expansion of the neutron-density function in a discrete-energy representation. This eigenfunction method is compared with a method based on direct integration of the Boltzmann equation using a discrete-energy mesh for the scattering integral and a first-order Taylor series for the time integration. Both methods of calculation have given the same results where compared in the area of time-dependent and steady-state spectra. The Wigner-Wilkins Mass-1 and Nelkin scattering models have been used with particular emphasis on the computation of time-dependent, asymptotic, steady-state spectra and diffusion parameters and the determination of their sensitivity to the scattering kernel. It is found that time-dependent spectra are rather sensitive to the scattering kernel, particularly at times of the order of a few microseconds after the introduction of a neutron pulse in the case of hydrogenous moderators. The eigenvalues and eigenfunctions for both realistic scattering kernels show the characteristics predicted for simpler analytic models. Both discrete and continuum eigenvalues have been found with the eigenfunctions corresponding to the continuum eigenvalues exhibiting a characteristic singular behavior. An interpolation scheme to determine steady-state spectra in hydrogenous moderators is also presented. The method, which is based on interpolating in the reciprocal of the infinite-medium neutron lifetime, gives very good agreement with directly computed spectra in the range of 200 to 15 microseconds lifetime. A perturbation method based upon the infinite-medium eigenfunctions is used to compute diffusion parameters for the decay constant in water; this method, through terms in B4, yields the decay constant to better than 1% in comparison with the exact diffusion theory result for B2 = 1.0 cm-2.
