Core power

The Model 412 PWR uses several control mechanisms. The first is the control cluster, consisting of a set of 25 hafnium metal rods coimected by a spider and inserted in the vacant spaces of 53 of the fuel assembhes (see Fig. 6). The clusters can be moved up and down, or released to shut down the reactor quickly. The rods are also used to (/) provide positive reactivity for the startup of the reactor from cold conditions, (2) make adjustments in power that fit the load demand on the system, (J) help shape the core power distribution to assure favorable fuel consumption and avoid hot spots on fuel cladding, and (4) compensate for the production and consumption of the strongly neutron-absorbing fission product xenon-135. Other PWRs use an alloy of cadmium, indium, and silver, all strong neutron absorbers, as control material. 

Table A16.5 HT Cables up to 11 kV Armoured three-core power cables 1.9/3.3 kV ...

Table A16.6 Armoured three-core power cable 3.8/6.6 kV (grounded system)...

Martin Hochstadter introduces a three-core power cable that does not become deformed or burn by the high voltage electricity. 

The worst operating condition in a common design practice consists of overly conservative assumptions on the hot-channel input. These assumptions must be realistically evaluated in a subchannel analysis by the help of in-core instrumentation measurements. In the early subchannel analysis codes, the core inlet flow conditions and the axial power distribution were preselected off-line, and the most conservative values were used as inputs to the code calculations. In more recent, improved codes, the operating margin is calculated on-line, and the hot-channel power distributions are calculated by using ex-core neutron detector signals for core control. Thus the state parameters (e.g., core power, core inlet temper-... 

Dining outgassing of scrap uranium-aluminium cermet reactor cores, powerful exotherms led to melting of 9 cores. It was found that the incident was initiated by reactions at 350°C between aluminium powder and sodium diuranate, which released enough heat to initiate subsequent exothermic reduction of ammonium uranyl hexafluoride, sodium nitrate, uranium oxide and vanadium trioxide by aluminium, leading to core melting. 

Annular core inner/outer diameter m Average core power density W/cm3... 

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. 

In case of water ingress into the core with a rate of 0.0085 kg/s (Fig. 5) the core attains criticality at the 558th s of the transient after water ingress onset. Maximum reactivity value of 0.898 peff is attained in the calculation at the 583rd s, the core power... 

Reactor pressure vessel Core inlet temperature Core outlet temperature Coolant inlet pressure Coolant flow Core power density Average fuel bumup Refuelii interval Gas turbine cycle type... 

Fission counters are used extensively for both out-of-core and in-core measurements of neutron flux in nuclear flux in nuclear reactors. In out-of-core situations, they monitor the neutron population during the early stages of power ascension when the neutron flux level is very low. For in-core measurements, fission counters are used for flux mapping (and consequently, determination of the core power distribution). They are manufactured as long thin q lindrical probes that can be driven in and out of the core with the reactor in power. Typical commercial fission counters for in-core use have diameters of about 1.5 mm (0.06 in), use uranium enriched to at least 90 percent in as the sensitive material, and can be used to measure neutron fluxes up to 10 neutrons/(m s) [10 neutrons/(cm s)]. 

EC60092-354 Part 354 Single- and three-core power cables with extruded insulation for... 

Core Power, MWt 392 Total PHTS Flow Rate, kg/s 2143 1... 

Reactor power 200MWt Core power density 36.2kw/L... 

The reactor core power, power density, and geometry have been specifically constrained to maintain fuel particle integrity by limiting the maximum fuel temperature during all licensing basis events, including a loss of coolant and loss of all active cooling from full power operation. 

Monitoring of core power level during power operation is provided by ex-vessel neutron flux detectors. Flux monitoring at lower powers and at shutdown conditions is provided by source range detectors which are located in the side reflector. The reactor core and reflectors rest vertically on a support structure below the core and are restrained by a core lateral restraint structure located between the outer side reflector and the reactor vessel. 

In the shutdown mode, the reactor vessel is fully pressurized or, at different times, in various stages of depressurization. Afterheat from fission product decay is generated at rates of up to about 7 percent of the core power level prior to shutdown, depending on the time interval since shutdown. The core decay heat is removed by the HTS. When the HTS is not available, the heat is removed by the Shutdown Cooling System (SCS). The outer control rods are normally fully Inserted during shutdown, and meet the required shutdown margin, with due allowances for uncertainties, even if the maximvim reactivity worth rod remains fully withdrawn. For cold shutdown, the control rods in the inner reflector are also Inserted and for this case, the maximum reactivity worth control rod is in the inner reflector. The neutron flux level is continuously monitored by the source range detectors. 

The mechanical design of the fuel and core for the Standard MHTGR is described in Section 4.2.4.1.1. The results of the nuclear analysis of the core (Section 4.2.5.2.1) provided the core power and flux distributions for the fuel performance analysis. 

Nominal thermal and flow parameters were used in the fuel performance analysis except that the thermal power was increased to 102 percent of nominal full power per NRG Regulatory Guide 1.49 to account for uncertainties in core power measurements. The major thermal parameters used in the analysis are listed in Table 4.1-1. Nominal values of material properties were used in the analysis. The design correlations for the material properties of the H-451 graphite and the fuel rods account for thermal expansion, and the effects of fluence and temperature on thermal conductivity and irradiation-induced shrinkage. These thermal and flow parameters and... 

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