Moderator dump

Many redundant safety features were provided at the SRP. These included a moderator dump tank, gadolinium nitrate solution as emergency absorber, continuously mnning diesel generators, and a 95 x 10 -L (25 x 10 -gal) elevated water tank for each reactor, for assurance of cooling. 

A pencil-size neutron source, 0.22 gm RaBe, was placed between the fuel rods at the center of the lattice during approach measurements. Three BF, counters were used to monitor the neutron multiplication. Two safety channels with control and trip circuits from the TTR were used in conjunction with lour safety and two control rods for each experiment. A fast water-moderator dump system was also provided. 

The system is basically similar to many existing liquid systems. The core vessel accommodates cores up to 5 ft. in diameter by S ft. tall and a wide variety of grid structures. A moderator dump system and separate storage is employed. Heating and insulation allow operation up to a tenqmrature of 600 F. Poison rods are cable actuated and can be used in any lattice position. 

The 100-MWe Niederaichbach reactor was designed by Siemens in the early 1960s and constructed between 1965 and 1970 in the Isar Valley, about 70 km northwest of Munich. The reactor contained 351 vertical channels on a square pitch of 24.5 cm. The channels penetrated a tank or calandria containing heavy water. Basic control was achieved by adding a burnable poison, CdS04, to the moderator. The moderator level could also be adjusted and the moderator dumped to shut down the reactor. 

The plant is provided with two independent shut down systems the moderator dump and the liquid rods. Other safety systems are the containment and the emergency core cooling system. 

Control Safety rods either two separate banks containing up to 10 rods per bank (variable in size and composition) or fast internal moderator dump into cavity within tank. Coarse and fine control rods of variable composition and number, the difference being achieved by different gear speeds... 

Control East shutdown Internal moderator dump into cavity within tank for compact cores. Two banks of thermal absorbers may be fitted for pressure tube-type lattices. Eine control Variation of moderator level or insertion of fine control rods... 

The controlled flame was found to be largely unaffected by moderate swirl (levels up to 40%) although the stability was slightly reduced. Heavy swirl (beyond 75%) led to a further reduction in stability and intermittent formation of soot. The unforced swirling flame was not nearly as efficient in reducing soot formation as the controlled (forced) flame without swirl. The flame was unstable, quite yellow, and spread out to impinge upon the dump diameter... 

The apparatus for this experiment is shown schematically in Figure 9a. The positrons are produced by bremsstrahlung and pair-production at the beam dump of a 36 MeV electron linear accelerator. The positrons are moderated in tungsten vanes and transported to a Molybdenum n = 2 formation foil on the... 

Moderately thermophilic bacteria, those with an optimum temperature for growth of between 45 and 50°C, have been isolated from a variety of sites, such as mud springs, coal piles, various mineral dumps, and drainage waters from sulfide ore deposits, dumps, and mines (22). Some examples are listed in Table I. Mixed bacterial cultures isolated from such environments have been purified by serial dilution and plating on thiosulfate or tetrathionate agar (83). Some moderate thermophiles are active over a wide temperature range. A mixed culture oxidized pyrite at 30°C as rapidly as T. ferrooxidans alone and carried out the same reactions at temperatures over 50°C (6). These properties are of considerable value in commercial operations (Section V). 

FIGURE 19.14 Model dumping plumes (g/cm ) of suspended particulate matter (SPM) settled at the sea bottom (left) and suspended in water column (right) after 15 days of moderate wind forcing. The scale is logarithmic, arrows indicate mean model currents (left), and daily mean winds (right). 

An example involving the addition of a perlite filter aid to a clay suspension with a volumetric concentration of q)j = 0.058 wUl be discussed. Constant rate filtration (Camacho 1975) with different fractions of perlite was used to obtain cake resistance and cake solidosity as functions of Ap. The specific problem to be analyzed is a constant pressure filtration at 200 kPa (29 psi) of this clay suspension. For constant pressure and constant rate filtration with minimal medium resistance, maximum cycle flux is reached when the filtration time equals the time required to dump the cake, clean the filter, and start the next cycle (Rushton et al. 1996). hi this example, it is assumed that the dead time between cycles is 15 minutes. With t (filtration) = 15 minutes, a cake thickness of L = 0.014 m results when the cycle rate is maximized for this highly resistant, moderately compactible clay. 

Channeling is severe in towers filled with stacked packing, which is the main reason they are not much used. It is less severe in dumped packings. In towers of moderate size channeling can be minimized by having the diameter of the tower... 

The most commonly recycled material is water. Seldom destroyed in use, water serves as a medium for chemical reactions and as a heat transfer mechanism in steam or hot water systems, car engines, and various industrial processes. Moderately dirty water may be dumped directly into streams, injected into wells, or, in the case of cooling water from power plants, allowed to pass through wetlands to cool. 

Under moderately wet climatic conditions, freshly dumped refuse has an average water content of approximately 30%. The storage capacity is much higher (450-600 LU dry refuse = 39-46%), but... 

Disperse the Carbopol in the water by simply "dumping it in. The polymer will wet out in a few minutes. Add the surfactant while mixing under moderate agitation. 

The Group were interested in visiting SGHWR because it is a direct cycle pressure tube reactor, with some superficially similar features to the Chernobyl reactor. The moderator is, however, heavy water rather than graphite as at Chernobyl. Control is by pumping boric acid solution into liquid shutdown tubes and dumping heavy water moderator. 

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