Shim-safety rods

Referring to Fig. ii2.D., ."it wiH. be seen that the-end boxes of the fuel assembly fit into the upper an.d. lower assembly grids... i. The spring section of the upper end box (see Fig. 2.2.B) allows each assembly to be held firmly, and still allows for expansion and tolerance, limitations. . The eight square holes in the upper assembly grid a re for the. shim-safety rods which exbend all- the way through the rea ctor., ... 

The MTR control rods are of two main classes, the shim-safety rods and the regulating rods. All of them are designed to lower the reactivity of the reactor when they are inserted, and when fully in, i.e., resting in their shock absorbers, they will Overcome ah excess reactivity of greater than 40X. It will be shown in Chap. 6 that it is necessary to have approximately 19% excess reactivity built into the reactor hence the control rods provide an adequate margin of safety. 

The two types of shim-safety rods are shown in Figs. 2.3.A and B. 

Pertinent data on the shim-safety rods are summarized in Table 2.3.A. 

Bottom Absorber, Shim-safety Rod. The bottom shock absorbers for the shim-safety, rods are located on a plate mounted on the bottom plug. They consist merely of dash-pots into which plungers mounted on the bottom of the. shim rods fit. Since they are on the bottom plug they are always filled with water, which acts as the damping fluid. 

Insert - to move in downward direction a shim-safety rod holder holding a rod. 

Lower to move in downward direction a shim-safety rod holder not holding a rod (.i. e., empty). Note "Lower" is also used to mean change of seryo control point by running motor-operated rheostat..) - ... 

The racks for the storage of shim-safety rods are confined to groups of 16, four in a row and four tiers high. One rack is installed, while the future installation of racks in the other side of the canal is provided for by expansion anchors for the racks in the floor of the canal. 

The rack consists of three sections, each of which is bolted to the canal floor and so located that the rod rests in all three. The end sections are U shaped to contain the,..rod and to permit easy insertion and withdrawal. The Tower end section.is closed at the bottom to stop the rod. The middle section supports the uranium section of the shim-safety rod. It is constructed in an angular shape and is lined with 1/32-in.- thick sheet cadmium to absorb neutrons. 

RCKUlatlng Rods. Four regulating rods are stored parallel to the floor in (/-shaped openings constructed at the bottom of the shim-safety storage rack. These openings are placed on the inside and outside of two adjacent shim-safety rods this permits easy insertion and withdrawal of the rods. 

Leyse, C. F., Cooling of Thorium Shim-Safety Rods in Canal, ANL-ABS-10, November 16,.. 1949. 

For these reasons the Mock-Up was provided with two complete shim-safety rod channels and one regulating rod channel. The control, room contained the operating console which served as the study model for the MTR desk and a relay panel, both equipped with the necessary electrical equipment for testing system performance. 

Shim-Safety Rods and Drive Mechanisms. The shim-safety rods and... 

The flexible connections now incorporated in the shim-safety rod design were previously a section of the drive shafts, immediately above the magnets. 

Flow Through Safety Rods. The shim-safety rods afso require a cooling velocity of 30 ft/sec through the fuel section. Measurements in a previous experiment indicated a pressure drop of 40 psi for this velocity. Calibration of the Mock-Up rods agreed with this figure. The curve of velocity versus pressure drop is presented in Fig. A4.L. 

CALIBRATION OF CADMIUM SHIM SAFETY ROD NEW TYPE-0.060" FUEL PLATES... 

Nicoll, D.. Supplementary Report to Design of Shim-Safety Rods. OWIL CF-49-1-6S, December 31, 1948. 

Beall, S. E.. Shim-Safety Rod Data. OBNL CF-49-8-188, August 17, 1949. 

Twelve blade-type shim-safety rods move vertically through the core in the pattern shown in Fig. 7. The absorbing portion of each rod is about 7 in. wide and 42 in. long. The drive mechanisms for these rods are located in a room underneath the reactor (Fig. 9). 

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