Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
<strong>atw</strong> Vol. 63 (<strong>2018</strong>) | Issue 8/9 ı August/September<br />
446<br />
OPERATION AND NEW BUILD<br />
commercial delivery, while improving<br />
the quality of the data and resulting<br />
design models used to describe the<br />
fuel. This new approach would be a<br />
significant improvement compared<br />
to the current, largely empirical<br />
approach, which requires years to<br />
obtain limited data from a very expensive<br />
test reactor(s), as well as for the<br />
fabricating, testing, cooling, transportation<br />
and post-irradiation examination<br />
of samples. To reduce the<br />
licensing timeframe for EnCore Fuel,<br />
Westinghouse plans to utilize:<br />
• Atomic scale modeling:<br />
• By utilizing first principles to<br />
determine physical properties<br />
of irradiated materials<br />
• By leveraging Westinghouse<br />
involvement in the Nuclear<br />
Energy Advanced Modeling &<br />
Simulation (NEAMS) Department<br />
of Energy (DOE) program<br />
on basic property prediction<br />
• By leveraging Westinghouse<br />
involvement in the Consortium<br />
for Advanced Simulation of<br />
Light Water Reactors (CASL) –<br />
Virtual reactor design<br />
• By continuing to utilize MedeA<br />
and Thermo-Calc software<br />
• Real-time data generation to verify<br />
the atomic scale modeling:<br />
• Poolside data generation<br />
PP<br />
Gamma emission tomography<br />
based on gamma-ray spectroscopy<br />
and tomographic reconstruction<br />
can be used for<br />
rod-wise characterization of<br />
nuclear fuel assemblies without<br />
dismantling the fuel to detect<br />
pellet swelling, pellet- cladding<br />
interaction and pellet cracking<br />
PP<br />
Potential use of a spectroscopic<br />
detection system to select<br />
different gamma-ray emitting<br />
isotopes for analysis, enabling<br />
nondestructive fuel characterization<br />
with respect to a variety<br />
of fuel parameters (fission gas<br />
release)<br />
• Wired or wireless transmission<br />
technology for measuring<br />
PP<br />
Centerline temperature<br />
PP<br />
Fuel rod gas pressure<br />
PP<br />
Swelling of fuel<br />
In addition to saving time and cost, with<br />
this approach Westinghouse hopes to<br />
achieve, an increased confidence by the<br />
U.S. NRC due to the predictability of<br />
performance that can be obtained since<br />
the performance models will have a<br />
theoretical basis in addition to an<br />
empirical basis. There should also be<br />
reduced time and effort due to the reduction<br />
in the number of submissionreview-revision-<br />
submission cycles. This<br />
should remove the review process from<br />
the critical path to commercialization.<br />
Communication with the U.S. NRC<br />
Commissioners, and coordination<br />
between the DOE, NRC and industry<br />
for licensing of ATF, are in progress<br />
and continuing.<br />
7 Conclusion<br />
Westinghouse and its partners are<br />
continuing to make good progress on<br />
U 3 Si 2 fuel, SiC cladding, and chromium-coated<br />
zirconium cladding. These<br />
new designs will offer design-basisaltering<br />
safety, greater uranium efficiency,<br />
and significant economic<br />
benefits per reactor per year for PWRs.<br />
While all testing and development to<br />
date has been engineered for LWR<br />
designs, Westinghouse believes the<br />
technology could provide some of the<br />
same safety and economic benefits to<br />
CANDU and other reactor designs.<br />
Fuel and accident modeling with<br />
other types of reactor systems will be<br />
required to evaluate the actual potential<br />
for these benefits. This, together<br />
with more beneficial power peaks,<br />
lower impact of the transition cycles<br />
and reduced dependence on uranium<br />
price assumptions, make adoption of<br />
the Westinghouse ATF, in conjunction<br />
with a transition to 24-month cycle<br />
operation, the recommended path<br />
forward for implementation of the<br />
Westinghouse ATF, EnCore Fuel.<br />
References<br />
[1] Gordon Kohse, MIT, 2016.<br />
[2] Ed Lahoda, Sumit Ray, Frank Boylan,<br />
Peng Xu and Richard Jacko, SiC Cladding<br />
Corrosion and Mitigation, Top Fuel 2016,<br />
Boise, ID, September 11, 2016, Paper<br />
Number 17450, ANS, (2016).<br />
[3] Jason Harp, Idaho National Laboratory<br />
preliminary photographs.<br />
[4] Lu Cai, Peng Xu, Andrew Atwood,<br />
Frank Boylan and Edward J. Lahoda,<br />
Thermal Analysis of ATF Fuel Materials<br />
at Westinghouse, ICACC 2017, Daytona<br />
Beach, FL, January 26, 2017.<br />
[5] E. Sooby Wood, J.T. White and A.T.<br />
Nelson, Oxidation behavior of U-Si<br />
compounds in air from 25 to 1000 C,<br />
Journal of Nuclear Materials, 484,<br />
pages 245-257 (2017).<br />
[6] Eugene van Heerden, Chan Y. Paik,<br />
Sung Jin Lee and Martin G. Plys,<br />
Modeling Of Accident Tolerant Fuel<br />
for PWR and BWR Using MAAP5,<br />
Proceedings of ICAPP 2017, Fukui and<br />
Kyoto ,Japan, April 24-28, 2017.<br />
Authors<br />
Gilda Bocock<br />
Robert Oelrich<br />
Sumit Ray<br />
Westinghouse Electric Company<br />
5801 Bluff Road<br />
Hopkins, SC 29061, USA<br />
Analyses of Possible Explanations for the<br />
Neutron Flux Fluctuations in German PWR<br />
Joachim Herb, Christoph Bläsius, Yann Perin, Jürgen Sievers and Kiril Velkov<br />
Revised version of a<br />
paper presented at<br />
the Annual Meeting<br />
of Nuclear Technology<br />
(AMNT 2017), Berlin.<br />
During the last 15 years the neutron flux fluctuation levels in some of the German PWR changed significantly. During<br />
a period of about ten years, the fluctuation levels increased, followed by about five years with decreasing levels after<br />
taking actions like changing the design of the fuel elements [1, 2]. The increase in the neutron flux fluctuations resulted<br />
in an increased number of triggering the reactor limitation system and in one case in a SCRAM [3].<br />
There exist different possible explanations<br />
how neutron flux oscillations are<br />
caused by physical phenomena inside<br />
a PWR. Possible explanations can be<br />
based on complicated interactions<br />
between thermo-hydraulical (TH),<br />
structural-mechanical and neutron<br />
physical processes (see Figure 1).<br />
Yet, no comprehensive theory<br />
exists, which can explain the neutron<br />
flux fluctuation histories observed<br />
in German PWR based on first <br />
physical principles. Therefore, GRS<br />
has started investigations to<br />
explain the observed neutron flux<br />
Operation and New Build<br />
Analyses of Possible Explanations for the Neutron Flux Fluctuations in German PWR ı Joachim Herb, Christoph Bläsius, Yann Perin, Jürgen Sievers and Kiril Velkov