Similarity evaluation between neutron multiplication factors and nuclide inventories during nuclear fuel burnup

There are several different types of the integral data of nuclear fission systems, and the accuracy of the numerical predictions of them are related with each other via the nuclear data commonly used in the numerical simulations. Thus, it is sometimes possible that measurement data of one type of the integral data are used to improve the prediction accuracy of the different type of the integral data. To quantitatively evaluate such possibility, the similarity of the different types of the integral data is important. In this study, we quantitatively evaluate the similarity between neutron multiplication factors and nuclide inventories during nuclear fuel burnup from the viewpoint of the nuclear data uncertainties using the representativity factors. Using the Burner module of the CBZ reactor physics code system for fuel pin-cell burnup problems, we calculated the sensitivity of the neutron infinite multiplication factors and the inventories of the 17 actinoids at several fuel burnup points. The neutron multiplication factor during the fuel burnup was considered the target parameter for which the prediction accuracy is improved, and the degree of similarity of the nuclide inventory data during burnup to the target was quantitatively evaluated using the representative factor. Subsequently, multiple nuclide inventory data were combined using the concept of the extended bias factor method to create a fictitious parameter, and we investigated how much this fictitious parameter can increase the representativity factor for the target parameter. As a result, the representativity factor for the target parameters could be increased to more than 0.8 using some nuclide inventory data, and up to 0.92 depending on the burnup, even taking into consideration the measurement error.

Uncertainty quantification calculations of nuclide number densities of Gd-bearing fuel rods in light water reactors

The Post-Irradiation Examination (PIE) data are quite useful to validate the evaluated nuclear data. Recently, a new experimental program, REGAL (the Rod-Extremity and Gadolinia AnaLysis), has been proposed and launched. During this program, the PIE data are acquired for the Gd-bearing fuel rods during (or after) the initial Gd burnout. These PIE data would be different from those for the normal UOX or MOX fuel rods from a viewpoint of nuclide transmutation process. In the present work, we attempt to quantify this difference through calculating sensitivity coefficients of nuclide number densities of the Gd-bearing rods using the depletion perturbation theory and performing uncertainty quantification calculations with the sensitivity coefficients and the nuclear data covariance data. Through the numerical analyses, we found that the impact of the uncertainties of the nuclear data of Gd isotopes on the number densities of actinoids is negligible. The nuclear data-induced uncertainties of Gd isotopes number densities are relatively large during the Gd depletion, and those become small after the Gd burnout. After the Gd burnout, the relative standard deviations of Gd-155 and -157 number densities are approximately 6% and 13%, respectively, and the nuclear data of the parent nuclides of these Gd isotopes, Gd-154 and -156, are also important as well as those of Gd-155 and -157.

BURNUP SENSITIVITY CALCULATIONS WITH CBZ FOR LIGHT WATER REACTOR ASSEMBLY PROBLEMS

Sensitivities of k∞ and nuclides number densities during nuclear fuel burnup with respect to nuclear data are calculated with a reactor physics code system CBZ. Sensitivity calculations are carried out with the depletion perturbation theory applicable to nuclear fuel assemblies including burnable absorbers. Numerical results are presented both for BWR and PWR assemblies, and those demonstrate usefulness and effectiveness of burnup sensitivity calculation capabilities for LWR fuel assemblies.

Uncertainty quantification works relevant to fission yields and decay data

In the present paper, firstly, we review our previous works on uncertainty quantification (UQ) of reactor physics parameters. This consists of (1) development of numerical tools based on the depletion perturbation theory (DPT), (2) linearity of reactor physics parameters to nuclear data, (3) UQ of decay heat and its reduction, and (4) correlation between decay heat and β-delayed neutrons emission. Secondly, we show results of extensive calculations about UQ on decay heat with several different numerical conditions by the DPT-based capability of a reactor physics code system CBZ.

Accuracy of spinal curvature assessed by a computer-assisted device and anthropometric indicators in discriminating vertebral fractures among individuals with back pain

This study examined the accuracy of thoracic and lumbar kyphotic angles as well as anthropometric indicators for discriminating patients with vertebral fracture among Japanese women >50 years old with back pain. Along with region-specific kyphotic angles and anthropometric indicators, the combination of thoracic and lumbar kyphotic angles offered the highest accuracy.

INTRODUCTION

Vertebral fractures have been associated with thoracic kyphosis. However, reports on lumbar kyphotic changes in association with vertebral fracture are scarce. This study investigated the accuracy of thoracic kyphotic angle (TKA) and lumbar kyphotic angle (LKA) measurements as well as anthropometric indicators (wall-occiput distance (WOD) and rib-pelvis distance (RPD)) in discriminating patients with vertebral fracture.

METHODS

Lateral radiographs of the spine were obtained in 70 postmenopausal Japanese women who visited an orthopedic clinic with low back pain (mean age, 76.2 ± 9.0 years). Radiographic vertebral fracture was diagnosed using quantitative measurement according to Japanese criteria. Osteoarthritis (OA) was defined as Kellgren-Lawrence (KL) grade 3 or higher. TKA and LKA were measured using SpinalMouse®. WOD and RPD were also measured.

RESULTS

At least one vertebral fracture was present in 49 subjects (70 %). Women with vertebral fractures showed significant increases in LKA, TKA + LKA, and WOD and decreases in RPD. Logistic regression analysis showed significant association between TKA + LKA and vertebral fracture independent of the presence of OA. Receiver operating characteristic analysis revealed that TKA was useful for discriminating thoracic fractures (area under the curve (AUC), 0.730) and LKA was useful for lumbar fractures (AUC, 0.691). The combination of TKA + LKA offered the highest accuracy for detecting thoracic, lumbar, and any vertebral fractures, with AUCs of 0.779, 0.728, and 0.783, respectively. WOD and RPD showed low-to-moderate accuracies for thoracic, lumbar, and any vertebral fractures.

CONCLUSIONS

Assessment of spinal kyphosis by SpinalMouse® as well as anthropometric indicators proved useful in discriminating subjects with vertebral fractures. These convenient and radiation-free methods could contribute to early diagnosis of vertebral fractures and subsequent appropriate treatment, thus preventing additional osteoporotic fractures.

The influence of strenuous muscle stimulation on the menarche

Nowadays, the average age at which menarche begins is lowering by three to four years every century, that is, four months every decade, according to both Japanese, and European and American annual changes of the average age. It emerged that the menarche shows a tendency to occur later in female gymnasts, because of the influence of strenuous muscle stimulation, and the fact that a higher level of technic is required in gymnastic games each year. These conclusions have been drawn from replies submitted to a questionnaire distributed among a relatively small number of gymnasts who participated in the competitions including the Inter High School Championship and the World Cup Championship. For example, at the age of 14, the percentage of women who had menstruated is almost 100% among women in general, but only 24% among World Cup Championship gymnasts, the average age at menarche of the latter being later than that of the former by as many as 3 years. At the age of 16, the percentage of women who had menstruated is 100% among women in general, but on the other hand, it is only 60% among World Cup Championship gymnasts, in other words, only a low percentage of women, of the latter group, had menstruated. Finally in our study, we established that the age at menarche of gymnasts is three or five years later than that of women in general. From our study, we concluded that the excessive burden imposed on muscles might cause an abnormal menstrual cycle, and the influence on menstruation would be considerable.

A new pattern discriminant method for evoked potentials

A statistical approach to evaluate evoked potentials (EPs), consisting of three stages in procedure, was proposed with an application to study on postictal changes of visually evoked potentials (VEPs). At the first step, time series data of EPs were reduced by the means of using an autoregressive (AR) model. In this way, EPs were described in terms of AR coefficient vectors. Then statistical distances which are well known as the Mahalanobis' distances were determined as a scale for dissimilarity between patterns of EPs. At the third stage, a retrospective classification through a numerical taxonomy based on similarity of patterns was demonstrated. This procedure will tell us some standards for future experiments as well as an integrative insight of results from present experiment. By the above method, it was suggested that there may be two different processes in postictal recovery of kindled cats.