ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Explore membership for yourself or for your organization.
Conference Spotlight
2026 ANS Annual Conference
May 31–June 3, 2026
Denver, CO|Sheraton Denver
Latest Magazine Issues
Jan 2026
Jul 2025
Latest Journal Issues
Nuclear Science and Engineering
February 2026
Nuclear Technology
January 2026
Fusion Science and Technology
Latest News
Plans for Poland’s first nuclear power plant continue to progress
Building Poland’s nuclear program from the ground up is progressing with Poland’s first nuclear power plant project: three AP1000 reactors at the Choczewo site in the voivodeship of Pomerania.
The Polish state-owned utility Polskie Elektrownie Jądrowe has announced some recent developments over the past few months, including turbine island procurement and strengthened engagement with domestic financial institutions, in addition to new data from the country’s Energy Ministry showing record‑high public acceptance, which demonstrates growing nuclear momentum in the country.
Yuichi Niibori, Joonhong Ahn, Hitoshi Mimura
Nuclear Technology | Volume 175 | Number 3 | September 2011 | Pages 641-651
Technical Paper | NURETH-13 Special / Radioactive Waste Management and Disposal | doi.org/10.13182/NT11-A12512
Articles are hosted by Taylor and Francis Online.
Relative permeability kr is a practical tool to describe two-phase flow in the performance assessment of a geological disposal system of radioactive waste. So far, to avoid thermal alteration of an engineered barrier system such as bentonite, the maximum temperature in the conceptual design of a Japanese geological disposal system has been limited to <373 K. However, for a limited time period, even if the temperature exceeds 373 K or the boiling point at the underground level, the robustness of the system is expected to be sufficient. An upward revision of the permissible maximum temperature would reduce the total space of the repository and would result in more effective use of the space. Therefore, when two-phase flow is also considered, a more reliable estimate of the thermal impact on the repository system is needed.In general, the fluid flow velocities of two phases are described by Darcy's law including the relative permeabilities defined as the functions of liquid-water saturation (or steam saturation), e.g., Corey's equations. However, such saturation (e.g., liquid-water saturation Sw) is not always uniformly distributed in the grid cells of the numerical implementation. In this study, the uncertainty of kr due to the distribution of Sw was examined by using various kinds of probability density functions (pdf's). The results suggest that the apparent kr value can be numerically described by the arithmetic mean, the standard deviation, and the skewness of Sw. (In other words, the apparent value of kr does not depend on the types of pdf's.) Since the value of Sw is in the range of 0 to 1, the standard deviation and the skewness are limited. Therefore, the apparent values of kr also are in a limited range. Using the Lagrange multiplier method, this study examined the ranges of the kr value for each arithmetic mean of saturation Swa. Furthermore, by considering both the frequency distribution and the spatial distribution of saturation, this study quantitatively shows the degree of uncertainty of relative-permeability curves. These curves can explain the scattered data of two-phase-flow experiments.
