Load-following capability

The reactor core, the source of nuclear heat, consists of fuel assemblies and control rods contained within the reactor vessel and cooled by the recirculating water system. A 1,220-MWe BWR/6 core consists of 732 fuel assemblies and 177 control rods, forming a core array 16 feet (4.8 meters) in diameter and 14 feet (4.2 meters) high. The power level is maintained or adjusted by positioning control rods up and down within the core. The BW R core power level is further adjustable by changing the recirculation flow rate without changing control rod position, a feature that contributes to excellent load-following capability. 

Performance Requirement - Load Follow Capability - SG Dryout Time - Daily load follow - Relaxation of dryout time to 20 minutes -Excluding frequency control - Related to PSCS removal... 

The AP 600 turbine consists of a double-flow, high-pressure cylinder and two double flow, low pressure cylinders that exhaust to individual condensers. It is a four flow tandom -compound, 1800 rpm machine. The turbine generator is intended for base load operation and also has load follow capability. 

A generic high-burnup element design (some features of which might be applied to NUE fuel to enhance the load-following capability)... 

Carter, T.J. and RJ. Fehrenbach. 1983. The Load Following Capability of CANDU Fuel, AECL Report, AECL-7096, February. 

Load following capability achieved without the operation of reactor control systems ... 

The natural circulation results in passive load following capability and autonomous control. It also makes loss-of-flow accidents inconceivable ... 

Very simple design with relatively few components. This is due to the superb passive safety features of the reactor coupled with the lack of refuelling, nearly zero burn-up reactivity swing over core life and autonomous load following capability. 

Autonomous load following capability due to natural circulation coupled with negative temperature feedback. Reactor is very tolerant to operators errors. 

It is also desirable to verify the autonomous load following capability of the ENHS reactor. 

Turbine-generator plant this is a new component, not tested in the MSRE. Hastelloy N is a Nickel-based alloy suitable for steam atmosphere, and the miniFUJI plant could be used to demonstrate the operation of a super-critical turbine system, including load-following capability, the reliability of structural materials for the steam generator, etc. 

Most nuclear power plants today are operated as base load plants, but with some ability to load-follow. For PWRs, this load following capability is achieved by means of systems that manage the boron concentration of the reactor coolant water by recycling the boron in and out, on a short time scale. This requires elaborate and complicated boron and water handling systems outside the containment, and results in restrictions on the rate of load follow available. 

CAREM is designed to be operated in base load, but it also has some load-follow capability. Loadfactor/ Availability... 

Reference is made to commercial SGHWR designs from the point of view of control. The effects of increased size compared with the Winfrith SGHWR on overall dynamic properties and spatial reactor modes are discussed together with control system developments to Improve load following capabilities. 

Some of the non-LW-SMRs offer load following capability even though most of the LW-SMRs work with base load. The following needs can be met with load following capability of some SMRs (IAEA, 2002 NRC, 2014a Kumar et al., 2012) ... 

Mortensen, J.H., Moelbak, T., Andersen, R, Pedersen, T.S., December 1998. Optimization of boiler control to improve the load-following capability of power-plant units. Control Engineering Practice. ISSN 0967-0661 6 (12), 1531-1539. 

The capital cost of a THERMAL DeNO, system includes the costs of ammonia and carrier gas systems, injectors, instrumentation and controls, installation, engineering, licensing fees, and, for a retrofit, the cost of any nnodifications. Retrofit applications usually involve neither major modifications nor excessive downtime. The capital cost is application specific and depends on the initial NO, concentration, the size of the boiler, the NO, reduction required, the load following capability, and the ammonia carryover limitations. 

The dynamic response of the PEMFC has been considered both in terms of start up times from cold condition and the load following capabilities under normal operation. PEMFC has a relatively shorter start up time compared to other types of fuel cells, because of the low operating temperature. Warm up time also is shorter. However, if the fuel is natural gas or other fuels, which requires reforming, the start time is dependent on both the size of the stack as well as the time taken to heat the reformer and not the fuel cell. If the PEMFC system has hydrogen as fuel, the start up time is not affected by the unit size as it is limited only by the time taken for the gas to flow through the system. 

There are many other aspects of recent FCV development that are worth commenting on, including a trend towards greater hybridization with batteries, which can make an FCV more responsive, and save money as a less powerful fuel cell might be required as a result. There have also been improvements in cold start-up (Honda is at the forefront here), and in the development of slim-line fuel cell systems that can fit into a car s chassis. Ju et al. (2005) have unveiled a control algorithm for active power distribution in a fuel cell/battery hybrid power source to improve system efficiency and battery life with load following capability. 

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