Reactor Core and Internals

Reactor Core and Internals Arrangement - Elevation View Reactor Core and Internals Arrangement - Plan View Graphite Core Support Structure - Flan View PSR Block Structure to the Hot Duct Entrance Support Post and Seat Geometry Bottom Reflector... 

Outline scheme for removal of standpipe region to give access for removal of reactor core and Internals. 

Fig 41 OUTLINE SCHEME FOR REMOVAL OF STANDPIPE REGION TO GIVE ACCESS FOR REMOVAL OF REACTOR CORE AND INTERNALS... 

Reactor core and internal design based on well proven ABB-CE technology... 

In the absence of positive reactivity insertions associated with the chemically and neutronically inert helium coolant, and limits on possible cool down events due to the large heat capacity of the reactor core and internals, control rod withdrawal events result in the maximum reactivity insertion. The design of the control rod drive mechanisms, and their location in the reactor cavity, preclude a control rod ejection event, thus the limiting overpower event is that associated with an inadvertent control rod withdrawal. Power and fuel temperature response to a control rod withdrawal event, with shutdown by the safety rods and with shutdown by the reserve shutdown system assuming failure of the safety rods, are shown in Fig. XV-10. 

Nuclear Boiler Assembly. This assembly consists of the equipment and instrumentation necessary to produce, contain, and control the steam required by the turbine-generator. The principal components of the nuclear boiler are (1) reactor vessel and internals—reactor pressure vessel, jet pumps for reactor water circulation, steam separators and dryers, and core support structure (2) reactor water recirculation system—pumps, valves, and piping used in providing and controlling core flow (3) main steam lines—main steam safety and relief valves, piping, and pipe supports from reactor pressure vessel up to and including the isolation valves outside of the primary containment barrier (4) control rod drive system—control rods, control rod drive mechanisms and hydraulic system for insertion and withdrawal of the control rods and (5) nuclear fuel and in-core instrumentation,... 

The operating modes of the Neutron Control Subsystem, in conjunction with the Reactor Core and Reactor Internals Subsystems, are discussed in Section 4.1.4.3. 

The CAREM project involves technological and engineering solutions, as well as several innovative design features that have been properly proved during the design phase. Within CAREM project, the effort was focused mainly on the nuclear island (inside containment and safety systems) where several innovative design solutions require developments. This comprises mainly the reactor core cooling system, the reactor core and fuel assembly, the reactor pressure vessel internals and the hydraulic control rod drive mechanisms. 

On the cylindrical part of the core barrel in the zone of flow separator the compensating plates are placed with the help of which the design value of mounting clearance is achieved. In heating-up the reactor vessel and internals this clearance is decreased and the core barrel is clamped to the flow separator over the whole perimeter that reduces the vibration loads on the core barrel. Design of the core baffle channels is changed to smooth temperature fields in the baffle and to decrease the resulted deformations of the baffle. 

On the other hand, the selection of a low mean power density in the reactor core, the selection of a suitable geometry for the reactor core and the surrounding core internals, and... 

Reactor vessel and internals Reactor pressure vessel, jet pumps for reactor water recirculation, steam separators and dryers, core spray, and feedwater spargers and core support structure... 

The reactor vessel design is based on proven historic SFR technology. The most important new feature of the PRISM reactor vessel and internals is that the reactor vessel has no penetrations (below the reactor closure head). This reactor vessel nozzle configuration precludes any large pipe ruptures at or below the elevation of the core. It is a key factor of the PRISM safety systems to keep the core completely and continuously flooded for the entire spectrum of design basis events/accidents. The reactor vessel is filled with liquid sodium and a helium cover gas. 

Intermediate sodium is circulated through the shell-side of the IHX and the shell-side of the SG by two EM pumps, each located in the cold leg of the loop in the SG facility. The internal EM pumps— pumps with no moving parts that move conductive fluids by way of a magnetic field—circulate the molten sodium through the reactor core and then to the IHTS. Permanent magnet flow meters are located in the cold leg to monitor sodium flow in the loop. 

Within CAREM project, the effort has been focused mainly on the nuclear island, i.e. internals of the containment and safety systems, where several innovative design solutions require R D within the first stage, in order to assure that they comply with functional requirements. These are mainly the solutions for Reactor Core Cooling System (RCCS), Reactor Core and Fuel Assembly, Reactor Pressure Vessel Internals (RPVI), and First Shutdown System (FSS). To fulfil project requirements, an extensive experimental plan has been prepared that includes the design and construction of several experimental facilities. 

Reactor construction. The reactor vessel and internals were constructed in this order the guard vessel for the reactor vessel, the reactor vessel, the core internals, the shield plug, the upper core structure and then the control rod drive mechanism. 

The major auxiliary systems of SMART consist of a component cooling system (CCS), purification system and make-up system. The function of the CCS is to remove heat generated in the main coolant pumps (MCPs), control element drive mechanisms (CEDMs), pressurizer (PZR), and the internal shielding tank. Feedwater supplied from the condensate pump of the turbo-generator is used as the coolant to remove heat. The purification system purifies the primary coolant and controls water chemistry to provide reliable and safe operation of the reactor core and all equipment in any mode of operation. The make-up system fills and makes-up the primary coolant in case of a primary system leak and supplies water to the compensating tanks for the PRHRS it consists of two independent trains, each with one positive displacement makeup pump, a makeup tank, and piping and valves. 

The ongoing joint United States/Russian Federation project to develop and construct a version of the GT-MHR to consume surplus weapons plutonium is an important element of commercial GT-MHR development. The major systems, structures and components of the GT-MHR, including the power conversion system, reactor vessel and internals, and reactor building, can be developed and demonstrated through this project. The primary alterations to the plutonium consumption design are expected to be in the reactor core and possibly the reactor cavity cooling system, with the remainder of the commercial GT-MHR drawing directly from the plutonium consumption version. 

The reactor core and associated internal components located within the reactor vessel shall be designed and mounted in such a way that they will withstand the static and dynamic loading expected in operational states, design basis accidents and external events to the extent necessary to ensure safe shutdown of the reactor, to maintain the reactor subcritical and to ensme cooling of the core. 

The sodium pools are mainly composed of a main vessel and guard vessel, with a temperature and pressure measurement instrument on the wall and a sodium leak detector in the gap of the vessels. The main vessel acting as the boundary of the primary circuit is a very important item of safety equipment. The internal strucmres involve the inner pool used to separate the hot and cold pools, the reactor core and its pressure header, and supports and shieldings. 

An AEC internal board of inquiry that assessed the reasons for the accident found fault with several technical deficiencies and administrative procedures. It cited as a primary cause "the condition of the reactor core and the reactor control system [that] had deteriorated to such an extent that a prudent operator would not have allowed operation of the... 

L. J. Siefken and M. V. Olsen, "Effect of Inconel Grid Spacers on Progression of Damage in Reactor Core", Fifth International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Salt Lake City, September 21-24, 1992. 

The point estimate core damage frequencies for the K-Reactor for both internal and external initiators are given in Table 11.3-6. 

The mean frequencies of events damaging more than 5% of the reactor core per year were found to be Internal Events 6.7E-5, Fire 1.7E-5, Seismic 1.7E-4, and total 2,5E-4. Thus, within the range of U. S. commercial light water reactors The core damage frequency itself, is only part of the story because many N-Reactor accident sequences damage only a small fraction of the core. The... 

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