Reflector movable

The quartz-crystal interferometer has been used mainly for obtaining sound velocities with high accuracy (0.1 % or better) over the range of frequency-to-pressure ratios from about 50 kHz/atm to 100 MHz/atm. The phase velocity V =fk is obtained through measurements of the wavelength X at accurately known frequencies. The common design employs a precision-cut quartz crystal opposed by a movable reflector, between which standing waves... 

Figure 3.11 An acoustic interferometer of the type used in the author s laboratory (from Nethery [104]). A X-cut quartz crystal, 100-600 KHz B crystal support mount and aligning screws. Optical flat E is attached to a movable reflector D for generation of ultrasonic standing waves. Invar rod F position is read from precision micrometer slide L.

In Fig. 8.19 the experimental setup for such time resolved double resonance experiments is schematically shown. The laser beam is split by the beam splitter BS into a pump pulse and a probe pulse which travel along different pathlengths before they enter the sample cell. The probe pulse is sent through a Raman shifter where its wavelength can be tuned to different transitions of the sample molecule. The time delay between pump- and probe pulse can be tuned by a movable retro-reflector. 

The reactor control system consists of four rods located in the radial reflector and in the lower movable end reflector. Two rods are used for automatic and manual control, whereas the other two, together with the movable reflector, are used for the protection in case of emergency. The negative temperature coefficient of the reactor reactivity allows operating for a long time without the interference of the control system. Only some deterioration of electric power necessitated increasing of thermal power up to a new level. 

A small fast reactor is used as a power source, the core of which contains more than 30 fuel rods. The fuel is a highly enriched uranium-molybdenum alloy. Longitudinally movable control rods are placed in the beryllium side reflector. 

An Enriched UO, ZrHj Critical Assembly, Af. V. Davis and A. W. Thiele (AI). A critical assembly has been built to obtain basic nuclear parameters necessary for the design of compact reactors for the SNAP Program. The assembly consists of two hemis pheres, separated on a horizontal plane. A machine was constructed that provided rigid support to the upper hemisphere and lifted the lower hemisphere at rates that would result in an approximately constant reactivity insertion rate, k portion of the reflector on the lower hemisphere was movable to provide fine adjustments in the reactivity. 

Figure 1 shows a picture of the reactor. The core, comprised of a stack of fuel and reflector blocks, rests on a low-density base to reduce floor reflection. The two halves of the reactor are separately movable, and are held apart Iqr springs. The tables are coupled to the drive mechanisms by magnetic latches which release on scram allowing the springs to separate the halves. The springs provide an acceleration of about 1 m/sec which produces fast safety shutdown of more than 4 in 200 msec. 

The assembly, as described, was subcrltical, but exhibited an apparent neutron source multiplication greater than 5. Criticality was achieved by increasing the outer-surface concrete reflector thickness from 20.3 to 30.5 cm of the array on the movable table i.e., the surface perpendicular to the direction of table motion. Criticality occurred at a table separation of 0.39 cm, and at table closure the keff of the assembly was measured as 1.0007. A second similar addition to the outer reflector surface on the stationary table resulted in criticality at a table separation of 7.36 cm. A summary of these data aj ears in Table U along with a schematic diagram of the experimental arrangement. 

The honeycomb critical assembly is a universal split table machine containing a 1.83-m ( ft>cubical matrix of 76-mm (3 in.)-square aluminum tub It is deagned to serve as a flexible system for initial mbckup studies for basic critical parameter investigations. Fuel inventory consists of various Assile species such as 330 kg of O.OS-mm-thick U(93) foils with widths and lengths appropriate to the aluminum matrix tubes. Control and safety rods utilize sections of the core or reflector materials for their flmction and major disassembly is provided by the movable section of the table. Honeycomb is presently stacked with a UOrMo (core). Be (reflector) mockup of a space powa reactor. 

Big Ten is a cylinilrical assembly comprising a U( 10%) core surrounded by a depleted uranium reflector. Overall, the cylinder is 0.84 m in diameter by 0-96 m long. The reflector is 0.15 m thick peripherally and 0.21 m thick at the ends. Major disassembly is provided by a movable section 039 m long the stationary section is 0.S7 m long. 

The SUR-IOO reactor is a solid homogenous reactor with 20% enrichment uranium fuel, moderated by polyethylene and using graphite as reflector. The core has the form of a cylinder, with 24 cm in diameter and 26 cm high, and is cooled by natural circulation of air. It is made up of fuel elements in the form of polyethylene discs of 24 cm diameter and stacked to a total height of about 26 cm divided into two symmetrical blocks the upper block is fixed and the lower one is movable. Two cadmium plates outside the core — in the reflector region — are used as control rods. The reactor also has a Ra-Be neutron source. 

Reactivity control mechanism (burnable poisons, control rods, liquid boron, spectral shift, movable reflector, etc or a combination thereof), number of independent active reactor control and protection (RCP) systems, cumulative worth for each RCP system... 

The 4S is a reactor without on-site refuelling in which the core has a lifetime of approximately thirty years. The movable reflector surrounding the core gradually moves, compensating the bum-up reactivity loss over the thirty-year lifetime. 

Reactivity control system Axially movable reflectors / Fixed absorber ... 

Primary shutdown system Axially movable reflectors of 6 sectors ... 

The primary sodium circulates from the EM pumps downward, driven by pump pressure, and flows through radial shielding assemblies located in the region between the RV and the cylindrical dividing wall. The coolant flow changes its direction at the bottom of the RV and then goes upward, mainly into the fuel subassemblies and partly into the movable reflectors. 

The burn-up reactivity swing is compensated by axially movable reflectors electromagnetic impulsive force (EMI) is applied in the driving mechanism of the reflectors. In an EMI system, the inertia of the reflector is the force behind the mechanics an EMI unit is provided for each of the six reflectors [XIV-2 to XIV-4], While an EMI technology will be developed for 4S, a combined system of ball screw and hydraulic mechanism as a developed system might be adopted for a reflector drive system in an initial phase of 4S deployments. 

The fundamental concept of the 4S is that of continuous monitoring rather than active operation . The reactor operates using a system of pre-programmed movable reflectors and the power control is executed from the outside, through feedwater flow rate changes in the power circuit. The plant and component conditions and/or unauthorized access could be continuously monitored from outside the site, e.g. by satellite systems. 

A 30-year lifetime of the 4S core and fuel the use of metal fuel and reactivity control with the movable reflector ... 

Although the PRACS can remove the decay heat under a natural convection mode, it was assumed to be out of work and only the RVACS was available — this conservative analysis was performed to evaluate the heat removal capability of the RVACS. The movable reflector was assumed to be moved down in this event. 

The 4S reactor is designed to apply a reactivity control system with a movable annular reflector replacing the control rods and driving mechanisms, which traditionally require frequent maintenance. If applied, control rods would have to be replaced a number of times during the long core lifetime. 

FIG. XV-9. Pattern of burn-up reactivity control by movable reflector. 

Fig. 2 Schemes of the optical part in the LICRM system. 1, Laser light source 2, movable plane mirror or corner reflector 3, polarizer 4 and 5, photocells 6 and 7, semi-transparent (half-sUvered) mirrors 8 and 9, stationary mirrors 10, the directions for the reflector 2 displacement...

Fig. 3 A scheme of the LICRM setup operating under compressive stress, 1, Laser light source 2, movable corner reflector 3, polarizer 4 and 5, photocells 6 and 7, semi-transparent mirrors 8, stationary corner reflector 9, specimen 10, support 11, puncheon 12, clock-like scale micrometer for rough controlling deformation 13, dampers 14, figured lever providing a stress constancy 15, load 16, oil damper 17, cooling unit 18, heater 19 and 20, programmable temperature regulator 21, amplifier 22, tape recorder 23, oscillograph 24, shaper of a meander (Schmitt trigger) 25, computer with the interface board imbedded...

Operation of a nuclear power plant. Heat generation takes place in the reactor core of a nuclear plant (Figure 23.14). The core contains the fuel rods, which consist of fuel enclosed in tubes of a corrosion-resistant zirconinm alloy. The fuel is uranium(lV) oxide (UO2) that has been enriched from 0.7% the natural abundance of this fissionable isotope, to the 3% to 4% reqnired to snstain a chain reaction in a practical volume. (Enrichment of nuclear fuel is the most important application of Graham s law, see Section 5.5.) Sandwiched between the fuel rods are movable control rods made of cadmium or boron (or, in nnclear snbmarines, hafninm), substances that absorb neutrons very efficiently. When the control rods are lowered between the fuel rods, the chain reaction slows because fewer neutrons are available to bombard uranium atoms when they are raised, the chain reaction speeds up. Neutrons that leave the fuel-rod assembly collide with a reflector, usually made of a beryllium alloy, which absorbs very few neutrons. Reflecting the neutrons back to the fuel rods speeds the chain reaction. 

Reactivity control system Control rods + B4C Spheres Axially movable reflectors Hydrogen gas... 

The reactor vessel surrounds the core and a combination of fixed and movable reflectors surround the vessel. The movable reflector is segmented and used to maintain reactivity at the desired operating temperature over life. Instrumentation to monitor power and temperature is used to determine when to move reflector segments during reactor startup and to compensate for uranium burn-up during operation. The reactor uses at least one safety shutdown rod. Safety rods are only used during transport and launch and would be withdrawn from the core prior to initial criticality. 

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