Control blades

It was reported that the hot air purging (450°F for 24 hours) yields solids in a condition suitable for transport under government control (Blades et al., 2004). Some posttreatment, such as smelting for metal scrap or incineration for carbon, may be required if the solids are not to be disposed in a hazardous waste landfill. 

Core shroud Control blade (absorber tubes)... 

The internal recirculation pumps are provided with more than 10% excess, flow rate capacity, which allows xenon override, and the fine motion control rod drives and the grey-tipped control blades allow control rod movements at full power. The excess pump capacity is utilized for hydraulic spectral shift operation the core coolant flow is increased towards the end of the operating cycle. The built-in "redundanc> " also implies that the reactor can be operated at full power even if one pump should fail. 

The SBWR core configuration consists of 732 bundles - 648 interior bundles and 84 peripheral bundles. The inlet orifice of the peripheral bundles is restricted in order to preferentially force flow through interior, high power bundles. The rated core power is 2000 MWt, which corresponds to a 41.5 kW/1 power density. The lower power density results in improved fuel cycle costs and greater manoeuverability. Since the SBWR is a natural circulation reactor, the reactivity control is maintained by movement of control blades and burnable poison being introduced into the fuel. 

Effects of Control Blades In Lattices Moderated by DjO/HjO Mixtures, R. H. Clark,... 

BWR fuel uses a square fuel channel (or shroud) which surrounds and supports the fuel rods and grids while separating flow channels. A BWR fuel assembly is shown in Figure 12.2. Figure 12.3 shows a cross section of a BWR fuel module that consists of four assemblies with a cruciform shaped control blade in between them. 

Control rod/control blade calibration using the in-hour equation. 

Control blade withdrawal speed given in UWNR 200 2.3.5 (2) as 14.5 inches/minute. Also in 2.9.4 (a)... 

Following the approach to critical, the next step is usually reactivity measurements. These include measurement of the worth of the control elements, the excess reactivity of the reactor, and the shutdown reactivity margin of the reactor. In this experiment, the worth of one of the reactor control blades will be measured using positive period techniques and the shutdown reactivity of the reactor will be measured using element drop techniques. Although it is traditional to use the word "rod" to refer to control elements, the word "element" will be used in subsequent paragraphs to refer to control elements, whether they be in rod, blade, bundle, or cruciform geometry. 

In this experiment, the worth of a control blade will be determined by measuring / h at five different element heights. This information will be used to construct a curve approximating d /dh versus h and integrating to obtain a value for the total worth of the blade. To measure / h, the blade will be set at some height h, and the remaining control elements banked to bring the reactor critical, i.e., = 0. 

Sometimes a single control blade drops. How can you tell whether it dropped from a scram condition or from mechanical problems (shock, poor alignment between the magnet and the armature) (0.5)... 

List three different factors that may cause a core reactivity change other than a control blade... 

The reactor is made exactly critical with the source removed at 0.5 watts and a bank height of 9.36 inches. Number two control blade is then withdrawn to establish a 30 second period. Power level is allowed to increase to 500 watts where the reactor is again leveled. Which of the following describes the final bank height at 500 watts ... 

Reference Console Information Book. Control Blade Worths... 

During full power operation control blade 2 falls into the core without any indication other than a BLADE DISENGAGED alarm. 

The minimum shutdown margin with the regulating blade and the most reactive control blade full out is ... 

What control blades or rods can be used for automatic control ... 

Fig. 9.6, Sectional view of the Grand Gulf boiling water reactor (courtesy of General Electric Company and Nuclear Engineering International). A, Vent and head spray B, steam dryer C, steam outlet D, core spray outlet E, steam separators F, feedwater inlet G, feedwater sparger H, L.P. coolant injection inlet J, core spray pipe K, core spray sparger L, top guide M, jet pump N, core shroud O, fuel assemblies P, control blade Q, core plate R, jet pump water inlet S, recirculation water outlet T, vessel support skirt U, control rod drives V, in-core flux monitor.

Corrosion of boiling water reactor control blades Nuclear 32 0.27... 

Figure 4.32 Dependence of lASCC on fast neutron fluence for creviced control blade sheath in high-conductivity BWRs where the tensile stress is high due to spot welds and dynamic due to swelling B4C absorber tubes [128].

BWRs have cruciform control blades, Figure... 

The specific in-core phenomena modeled in the APRIL code indude 2-D heat transfer between individui core components as well as between the core and surrounding structures, heat convection to the coolant in both the covered and xmcovered portions of the core, oxidation of the fuel dadding, channel walls, and control blades, fuel buckling (used as a criterion for rubble bed formation), slumping of the canisters and control blades, melting of individual core components, the formation of a eutectic mixture of fuel and molten zircaloy, molten material relocation and refreezing, channel blockage and the resultant flow redistribution. 

Figure 7. Molten mass of steel from control blades and upper structures for... 

R. 0. Gauntt, R. D. Gasser, and L. J. Ott, The DF-4 Fuel Damage Experiment in ACRR with a BWR Control Blade and Channel Box. NUREG/CR-4671, SAND86-1443, November 1989. 

Other recommendations with respect to the provisions of the EPGs from the standpoint of their application to ATWS are offered. These are first, that care be taken to avoid leading the operators to attempt manual depressurization of a critical reactor, second, that consideration be given to control the reactor vessel injection rate as a means for reduction of reactor power (as opposed to reactor vessel water level control as currently directed), and third, that removal of tiie rod sequence control system to facilitate the manual insertion of control blades under ATWS concfitions be undertaken, as authorized by the NRC. 

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