Department Of Energy/National Nuclear Security Administration Research Articles

Finite-element model to predict roll-separation force and defects during rolling of U-10Mo alloys

A major goal of the Convert Program of the U.S. Department of Energy's National Nuclear Security Administration (DOE/NNSA) is to enable high-performance research reactors to operate with low-enriched uranium rather than the high-enriched uranium currently used. To this end, uranium alloyed with 10 wt% molybdenum (U-10Mo) represents an ideal candidate because of its stable gamma phase, low neutron caption cross section, acceptable swelling response, and predictable irradiation behavior. However, because of the complexities of the fuel design and the need for rolled monolithic U-10Mo foils, new developments in processing and fabrication are necessary. This study used a finite-element code, LS-DYNA, as a predictive tool to optimize the rolling process. Simulations of the hot rolling of U-10Mo coupons encapsulated in low-carbon steel were conducted following two different schedules. Model predictions of the roll-separation force and roll pack thicknesses at different stages of the rolling process were compared with experimental measurements. The study reported here discussed various attributes of the rolled coupons revealed by the model (e.g., waviness and thickness non-uniformity like dog-boning). To investigate the influence of the cladding material on these rolling defects, other cases were simulated: hot rolling with alternative can materials, namely, 304 stainless steel and Zircaloy-2, and bare-rolling. Simulation results demonstrated that reducing the mismatch in strength between the coupon and can material improves the quality of the rolled sheet. Bare-rolling simulation results showed a defect-free rolled coupon. The finite-element model developed and presented in this study can be used to conduct parametric studies of several process parameters (e.g., rolling speed, roll diameter, can material, and reduction).

Good practices in provision of nuclear safeguards and security training courses at the Integrated Support Center for Nuclear Nonproliferation and Nuclear Security

More than five years have passed since the Integrated Support Center for Nuclear Nonproliferation and Nuclear Security (ISCN) was established under the Japan Atomic Energy Agency (JAEA) in December 2010 and started its activities, in response to the commitment of Japan at the Nuclear Security Summit in Washington D.C.. The ISCN has been vigorously involved in capacity building assistance on nuclear nonproliferation (safeguards) and nuclear security, mainly in the Asian region. It has provided 105 training courses to 2901 participants in total as of August 2016. The ISCN plays a major role in strengthening nuclear nonproliferation and nuclear security in the region, and this can be considered one of the great results of the Nuclear Security Summit process. The ISCN has cooperated with the US Department of Energy/National Nuclear Security Administration (DOE/NNSA) and Sandia National Laboratories (SNL) to establish a base of instructors, particularly for the Center's flagship two-week courses, the Regional Training Course on Physical Protection of Nuclear Material and Facilities (RTC on PP) and the Regional Training Course on State Systems of Accounting for and Control of Nuclear Material (RTC on SSAC). Furthermore, the ISCN has provided training courses for experts in Japan, making the best use of the Center's knowledge and experience of organizing international courses. The ISCN has also started joint synchronized training with the Joint Research Centre of the European Commission (EC JRC) on nuclear safeguards. This paper describes the good practices at the ISCN through its five years of activities, focusing on its progress in nuclear safeguards and nuclear security training.

Enhanced Analysis Methods to Derive the Spatial Distribution of 131I Deposition on the Ground by Airborne Surveys at an Early Stage after the Fukushima Daiichi Nuclear Power Plant Accident

This paper applies both new and well tested analysis methods to aerial radiological surveys to extract the I ground concentrations present after the March 2011 Fukushima Daiichi nuclear power plant (NPP) accident. The analysis provides a complete map of I deposition, an important quantity incalculable at the time of the accident due to the short half-life of I and the complexity of the analysis. A map of I deposition is the first step in conducting internal exposure assessments, population dose reconstruction, and follow-up epidemiological studies. The short half-life of I necessitates the use of aerial radiological surveys to cover the large area quickly, thoroughly, and safely. Teams from the U.S. Department of Energy National Nuclear Security Administration (DOE/NNSA) performed aerial radiological surveys to provide initial maps of the dispersal of radioactive material in Japan. This work reports on analyses performed on a subset of the initial survey data by a joint Japan-U.S. collaboration to determine I ground concentrations. The analytical results show a high concentration of I northwest of the NPP, consistent with the previously reported radioactive cesium deposition, but also shows a significant I concentration south of the plant, which was not observed in the original cesium analysis. The difference in the radioactive iodine and cesium patterns is possibly the result of differences in the ways these materials settle out of the air.

Adapting the U.S. Domestic Radiological Emergency Response Process to an Overseas Incident

The earthquake and resulting tsunami in Japan led to a radiological release from the Fukushima Daiichi Nuclear Power Plan, which in turn resulted in the rapid activation and deployment by the U.S. Department of Energy National Nuclear Security Administration (DOE/NNSA) emergency response teams. These teams and those from other federal agencies are typically coordinated through the Federal Radiological Monitoring and Assessment Center (FRMAC) when responding to radiological incidents in the U.S. FRMAC is the body through which the collection, analysis, and assessment of environmental radiological data are coordinated and products released to decision makers. This article discusses DOE/NNSA’s role in the U.S. response to the Fukushima accident as it implemented its components of FRMAC in a foreign country, coordinated its assets, integrated with its federal partners, and collaborated with the Government of Japan. The technical details of the various data collections and analyses are covered in other articles of this issue.

Introduction to the Special Issue on the U.S. Response to the Fukushima Accident

Provides an introduction to the May 2012 issue of Health Physics, based on a special session at the 2011 Health Physics Society (HPS) annual meeting that focused on the United States' radiological response to the Fukushima Daiichi Nuclear Power Plant accident. This introduction outlines the papers in this important issue and describes the activities of the U.S. response participants, including the U.S. Department of Energy National Nuclear Security Administration (DOE/NNSA), Department of Defense, the U.S. Nuclear Regulatory Commission (NRC) and other organizations. Observations are provided and the stage is set for the articles in this issue which document many of the activities undertaken during the Fukushima accident and which describe challenges faced and valuable lessons learned.