Kabushiki Kaisha Toshiba

Ritsuo Yoshioka

Makoto Ueda

Masatoshi Kawashima

Shungo Sakurai

Mitsuharu Nakamura

Yuichi Motora

Hiroaki Okuda

Koichi Sakurada

Motohiko Onishi

Takahiro Tatsumi

Tadahiro Ohashi

Yuji Uenohara

Akira Tanabe

Yasushi Tsuboi

Mamoru Nagano

Tsugio Yokoyama

Shunsuke Ogiya

Yoshihira Ando

Toru Yamamoto

Yasushi Hirano

Shigenori Shiga

Shouichi Watanabe

Takeshi Seino

Tomonobu Sakuranaga

Munenari Yamamoto

Yoichi Motora

A system for correctly evaluating a price distribution and a risk distribution for a financial product or its derivatives introduces a probability density function generated with a Boltzmann model at a higher accuracy than the Gaussian distribution for a probability density. The system has an initial value setup unit and an evaluation condition setup unit. Initial values include at least one of price, price change rate, and the price change direction of a financial product. The evaluation conditions include at least time steps and the number of trials. The Boltzmann model analysis unit receives the initial values and the evaluation conditions, and repeats simulations of price fluctuation, based on the Boltzmann model using a Monte Carlo method. A velocity/direction distribution setup unit supplies the probability distributions of the price, price change rate, and the price change direction for the financial product to the Boltzmann model analysis unit. A random number generator for a Monte Carlo method employed in the analysis by the Boltzmann model, and an output unit displays the analysis result. A dealing system applies the financial Boltzmann model to option pricing, and reproduces the characteristics of Leptokurcity and Fat-tail by linear Boltzmann equation in order to define risk-neutral and unique probability measures. Consequently, option prices can be evaluated in a risk-neutral and unique manner, taking into account Leptokurcity and Fat-tail of a price change distribution.

Price and risk evaluation system for financial product or its derivatives, dealing system, recording medium storing a price and risk evaluation program, and recording medium storing a dealing program

A system for correctly evaluating price distribution and risk distribution for a financial product or its derivatives introduces a probability density function generated with a Boltzmann model at a higher accuracy than the Gaussian distribution for a probability density. The system has an initial value setup unit and an evaluation condition setup unit. Initial values include at least one of price, price change rate, and price change direction of a financial product. The evaluation conditions include at least time steps and a number of trials. A Boltzmann model analysis unit receives the initial values and the evaluation conditions, and repeats simulations of price fluctuation, based on the Boltzmann model using a Monte Carlo method. A velocity/direction distribution setup unit supplies probability distributions of the price, price change rate, and price change direction for the financial product to the Boltzmann model analysis unit. A random number generator for a Monte Carlo method is employed in the analysis by the Boltzmann model, and an output unit displays the analysis result. A dealing system applies the financial Boltzmann model to option pricing, and reproduces the characteristics of Leptokurcity and Fat-tail by a linear Boltzmann equation to define risk-neutral and unique probability measures. Consequently, option prices can be evaluated in a risk-neutral and unique manner, taking into account Leptokurcity and Fat-tail of a price change distribution.

System for evaluating price risk of financial product or its financial derivative, dealing system and recorded medium

In a reactor core, there is charged a number of fuel assemblies composed of a channel box and a fuel bundle disposed therein, in which fuel rods adjacent to each other are arranged so as to provide a triangular shape and a ratio of a coolant channel cross section to a fuel cross section is set to be 1 or less.

Reactor core

A nuclear reactor core is provided with a fuel assembly which comprises channel boxes respectively separated with spaces into which control rods are arranged and a plurality of fuel rods arranged in the channel box, at least a part of the fuel rods being charged with uranium-plutonium mixture fuel and an enrichment of U-235 or a concentration of plutonium, or both being distributed in an axial direction of the fuel rods. The concentration of a burnable poison packed in the fuel rod is distributed in the axial direction of the fuel assembly. The ratio of the occupying region of a moderator of the fuel assembly is increased with respect to the fuel occupying region. The number of the fuel rods containing the burnable poison is variously changed with respect to the total number of the fuel rods and the arranging mode thereof is also varied with the concentration thereof.

Fuel assembly of nuclear reactor

A core of a light-water reactor comprises a plurality of fuel assemblies each including a number of fuel rods. The fuel rod is provided with at least one area interposed between fuel areas in a clad of the fuel rod. The interposed area contains extremely reduced or substantially no fissile nuclide. At least two areas or layers with high enrichment of the fissile nuclide are formed in the axial direction of the reactor by the location of the interposed areas throughout the whole fuel assemblies arranged in the light-water reactor core.

Core of light-water reactor

In the field of commercial nuclear reactors, there is an increasing demand for long-life control blades in order to meet the requirements of higher economy and reduction in the disposal of radioactive wastes. A control blade proposed by the invention stands a long use by virtue of the use of a long-life neutron absorber which is typically made of hafnium. Despite the use of hafnium which has a large specific weight (13.3 g/cm.sup.3), the size, shape and weight of the control blade are substantially the same as those of conventional control blades which employ boron carbides B.sub.4 C as the neutron absorber, so that the control blade can be back-fitted in existing boiling water reactors without difficulty. The control blade of this invention is a flux-trap-type control blade in which long-life neutron absorber plates or sheets are arranged to oppose each other in the thicknesswise direction of the wing within the sheath plate such that a water gap is preserved between the opposing neutron absorber plates, so that the weight of the hafnium, which occupies most part of the total weight of the control blade, is reduced by an amount corresponding to the volume of the water gap. The thickness of the neutron absorber plates or sheets is increased at the upper portion of the control blade where the neutron exposure is specifically high and where a large neutron absorption power or capacity is required for ensuring a sufficient reactor shut-down margin, while the thickness is reduced in other portions so as to increase the size of the water gap. In consequence, the weight of the control blade incorporating heavy hafnium as the neutron absorber is reduced almost to the same level as that of ordinary control blades, without being accompanied by any reduction in the reactivity worth.

Control blade for nuclear reactor

A fuel assembly for a nuclear reactor includes a number of fuel rods filled with a fuel material. A plurality of fuel rods have a partial effective fuel area filled with a fuel material and has a portion in which enrichment of a fissile nuclide is significantly reduced or the fissile nuclide does not exist at all on an axial level including a reactor shut-down zone at which subcriticality becomes small during a reactor operation period. The other fuel rods are filled with the fuel material throughout the entire axial length thereof. The first mentioned fuel rod may be provided with a partially interposed zone or may be constructed by a fuel rod having a length shorter than that of the other fuel rod. The tube means may be arranged in the fuel assembly so as to pass the moderator therethrough.

Fuel assembly for nuclear reactor

A control blade for a nuclear reactor having inserted upper end structural members and inserted lower end structural members connected to a plurality of wings each in the form of a generally rectangular plate having an longitudinal axis extending in the longitudinal direction of the control blade, the wing being disposed to form a cross-shaped section of the control blade. The wings and the structural members are connected to and supported on a central connection member. Each wing or a sheath member formed within each wing is formed from a diluted alloy obtained by diluting a long-lived neutron absorber such as hafnium with a diluent such as zirconium or titanium. A plurality of neutron absorber housing holes are formed in the diluted alloy section. Specifically, if the housing holes are formed to extend in the widthwise direction of the wing, the sectional area of each housing hole formed in a portion of the control blade corresponding to the region where the subcriticality in the reactor core becomes smaller after the reactor has been shut down by fully inserting the control blade into the core is larger than that of housing holes formed in the other regions. A structure having a means to cope with swelling of the neutron absorber can be applied to the former region.

A fuel assembly for a nuclear reactor comprising a number of fuel rods arranged in a regular fashion in a channel box which is surrounded by water gap in a reactor core. Some of fuel rods disposed at portions facing the water gap through which no control blade is inserted or drawn out, have atomic number densities of fissionable material contained in the fuel rods. The atomic number density of each of these fuel rods is made smaller than that of the fuel rod disposed in the fuel assembly at portions other than the portions referred to above.

In the field of commercial nuclear reactors, there is an increasing demand for long-life control blades in order to meet the requirements of higher economy and reduction in the disposal of radioactive wastes. A control blade proposed by the invention stands a long use by virtue of the use of a long-life neutron absorber which is typically made of hafnium. Despite the use of hafnium which has a large specific weight (13.3 g/cm.sup.3), the size, shape and weight of the control blade are substantially the same as those of convertional control blades which employ boron carbides B.sub.4 C as the neutron absorber, so that the control blade can be back-fitted in existing boiling water reactors without difficulty. The control blade of this invention is a flux-trap-type control blade in which long-life neutron absorber plates or sheets are arranged to oppose each other in the thicknesswise direction of the wing within the sheath plate such that a water gap is preserved between the opposing neutron absorber plates, so that the weight of the hafnium, which occupies most part of the total weight of the control blade, is reduced by an amount corresponding to the volume of the water gap. The thickness of the neutron absorber plates or sheets is increased at the upper portion of the control blade where the neutron exposure is specifically high and where a large neutron absorption power or capacity is required for ensuring a sufficient reactor shut-down margin, while the thickness is reduced in other portions so as to increase the size of the water gap. In consequence, the weight of the control blade incorporating heavy hafnium as the neutron absorber is reduced almost to the same level as that of ordinary control blades, without being accompanied by any reduction in the reactivity worth.

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Yokohama, Japan

Ritsuo Yoshioka