[en] The Zero Energy Deuterium (ZED-2) Critical Facility, located at AECL's Chalk River Laboratories will be celebrating its 50th Anniversary this year. Built in the late 1950s, ZED-2 achieved first criticality on September 7, 1960. ZED-2 was initially built to test the fuel arrangement of Canada's first nuclear power plant, the Nuclear Power Demonstration (NPD), located along the shores of the Ottawa River about 20 km upstream of Chalk River. ZED-2 was the successor to the first nuclear reactor outside of the United States, the Zero Energy Experimental Pile (ZEEP), which was designed to investigate lattice physics and reactor kinetics. Since that time, the ZED-2 critical facility supports the development of the CANDU industry by testing a wide range of fuel bundle designs, fuel arrangements at low power under a variety of operating conditions and simulating accident scenarios. ZED-2 continues to operate today, supporting the current CANDU fleet, development of the Advanced CANDU Reactor and advanced fuel cycles including thorium fuels. To mark the historic occasion of ZED-2's 50th anniversary, a Technical Meeting to showcase the numerous accomplishments of low-power critical facilities worldwide was held in Ottawa, Ontario, Canada on November 1-3, 2010. The two-day Technical Meeting covered the following topics of interest to operators, experimenters and analysts involved with low-power critical facilities: safety and licensing of critical facilities; measurements in critical facilities; the use of measurements from critical facility to the test reactor; other uses of measurements from critical facilities; design development of instrumentation for measurements in or control of critical facilities; different fuel compositions, geometries, reactivity worth of devices, kinetics parameters, reactor types; measurements of irradiated materials, actinides; reactor physics benchmark databases and activities; and education and research with small reactors. Following the conference, AECL hosted all interested attendees for a day at the Chalk River Laboratories, with the highlight being a tour of the ZED-2 critical facility.

[en] CROCUS is a zero-power critical facility used mainly for educational purposes at the Swiss Federal Institute of Technology (EPFL) in Lausanne, Switzerland. It is a low-enriched-uranium fuelled, light-water moderated reactor, with the fission power limited to 100 W. The presentation will discuss the crucial role of CROCUS in teaching -- both as framework for reactor practicals offered to physics students at EPFL and as key educational tool in the recently established Swiss Master of Science in Nuclear Engineering. Regular development work is needed for the various instruments and components associated with the facility. As illustration, the recently completed refurbishment of the control rod system and the related calibration experiments will also be discussed.

[en] The MNRC is a facility centered around a 2 MW TRIGA research reactor, one of the three largest university research reactors in the US and the youngest. A wide range of research studies is underway including the imaging of fuel cells, tomography of geological minerals, neutron activation analysis of biological samples and plant seed irradiation. Industrial applications include radiography of precision aerospace castings and irradiation of electronics. The McClellan reactor may become part of a consortium of university reactors that will provide radiopharmaceuticals in response to a critical shortage in North America.

[en] Defueled channel experiments were performed in ZED-2 to help resolve discrepancies between calculated flux detector response during refueling in ACR-1000 according the reactor codes RFSP and MCNP. The data produced from these experiments was later used in a separate Regional-Over-Power (ROP) analysis to verify MCNP and RFSP neutron response predictions during refueling. These experiments provided information on thermal flux distributions interior and exterior to a fueled and defueled channel; and on epithermal absolute flux distributions exterior to the same channel. Critical height and moderator temperature data for fueled and defueled channel conditions were also measured. In addition, standard platinum-clad Inconel Self-Powered Detector (SPD) performance data was obtained. The following reactor physics and SPD parameters were measured in these experiments: C Radial flux distribution inside the channel of interest (fueled and defueled), C Radial flux distribution outside the channel of interest (fueled and defueled), C Epithermal radial flux distribution outside the channel of interest (fueled and defueled), and C SPD response parallel to and normal to the channel of interest (fueled and defueled).

[en] Static and transient experiments were performed in the ZED-2 reactor using a 24-cm square pitch lattice of 52 channels of heavy-water moderated ACR-LEU and CANFLEX-LEU 43-element fuel bundles, cooled with H₂O, air (void) or a checkerboard pattern of H₂O and air. Static experiments were performed before and after insertion of two different reactivity devices. Transient experiments were also performed, in which a shutdown absorber rod was dropped into the core. Predictions by MCNP5 and WIMS-AECL/DRAGON/RFSP were compared against experiments. Differences were evaluated for k_eff, device worth, flux distributions, kinetics parameters, and flux versus time. Results showed good agreement.

[en] The Seven Percent Critical Experiment (7uPCX) is a reactor physics and critical benchmark experiment designed to provide data for the validation of the reactor physics codes used to design commercial reactor fuel elements. The first operation of the experiment occurred on May 11, 2009. Since then, more than 50 different fuel element configurations have been addressed in the experiment. The 7uPCX is seven weight percent enriched, UO2 fueled, square lattice, water moderated experiment. The pitches of the two grid plate sets fabricated for the experiments were chosen to bracket the fuel-to-water ratios in the current US fleet of commercial light water reactors. The first set of experiments was with the tighter pitch core with water holes dispersed in the array. An inverse-multiplication approach to critical was implemented. The approach started with cores that had calculated multiplication factors of 0.9 and 0.95. From these two points the next critical loading was predicated and half of fuel increment between the current core size and the predicted critical size was loaded. This process was continued through an inverse multiplication of zero and on to configurations that were supercritical. In the second experiment, fuel rods were inserted into the water holes in the first configuration to offer a solid (no water holes) core design. In this and the first experiments, startup source was located in the center of the core configuration in a water hole. The third set of experiments relocated the source outside of the perimeter of the core and filled the central location with a fuel rod. Further experiments in the series addressed the reactivity worth of water holes as a function of position in the array. The initial set of experiments for the tight fuel rod pitch is complete. The next step in the experiment program is to exchange the assembly grid plates for those with the looser fuel rod pitch. When that is done, the same set of experiments will be performed as for the tighter pitch configuration. The critical experiments at Sandia National Laboratories are currently funded by the US Department of Energy Nuclear Criticality Safety Program (NCSP). The NCSP has committed to maintain the critical experiment capability at Sandia and to support the development of a critical experiments training course at the facility. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

[en] Following a brief description of the reactor some of the history of ZED-2 will be described, particularly in so far as it relates to the development of reactor physics methods used in the design and analysis of CANDU power reactors.

[en] In 2001, the Royal Military College of Canada replaced its aging analogue SLOWPOKE-2 reactor control system with a digital control system. The system was successfully commissioned and has provided a renewed platform for student learning and research. An upgrade to the digital control and instrumentation system has been completed and will be installed in October 2010. The upgrade includes new computer hardware, updated software and a simulation and training system that will enhance training, education and research by licensed operators, students and researchers.

[en] TSUNAMI, a sensitivity and uncertainty analysis tool was applied to benchmark experiments for the irradiation of five (Th,Pu)O₂ bundles in ZED-2. This paper presents the result of the TSUNAMI-3D computation of keff , its sensitivities and uncertainties. It was found that 238U (n,γ) and 2H (elastic) cross section data are the major uncertainty contributors in keff and coolant void reactivity bias, respectively. Since the experiments were very similar, we could adjust the nuclear data using the Generalized Linear Least Squares Method, such that keff bias was reduced from 2.3mk to 0.01mk for the H2O-cooled (Th,Pu)O₂ simulation.

[en] The first approach to critical of the SLOWPOKE reactor is described together with many as yet unpublished photographs of the event. The development of the reactor and the overpower testing are discussed.