Pressurized water reactors instrumentation

Rhodium, vanadium, cobalt, and molybdenum have been used as emitters for SPNDs. Since rhodium SPNDs are the main in-core instruments for the determination of power distribution in pressurized-water reactors (PWR), they are discussed first and in greater detail than the others. 

Fig. 9.3. Sectional view of the Sequoyah pressurized water reactor (courtesy of Nuclear Engineering International). A, Control rod drive head adaptors B, instrumentation ports C, thermal sleeves D, upper support plate E, support column F, control rod drive shaft G, control rod guide tube H, internals support ledge J, inlet nozzle K, outlet nozzle L, upper core plate M, baffle and former N, fuel assemblies O, reactor vessel P, thermal shield Q, access port R, lower core plate S, core support T, diffuser plate U, lower support column V, radial supports W, instrumentation thimble guides.

There are many other examples in the literature where sealed-vessel microwave conditions have been employed to heat water as a reaction solvent well above its boiling point. Examples include transition metal catalyzed transformations such as Suzuki [43], Heck [44], Sonogashira [45], and Stille [46] cross-coupling reactions, in addition to cyanation reactions [47], phenylations [48], heterocycle formation [49], and even solid-phase organic syntheses [50] (see Chapters 6 and 7 for details). In many of these studies, reaction temperatures lower than those normally considered near-critical (Table 4.2) have been employed (100-150 °C). This is due in part to the fact that with single-mode microwave reactors (see Section 3.5) 200-220 °C is the current limit to which water can be safely heated under pressure since these instruments generally have a 20 bar pressure limit. For generating truly near-critical conditions around 280 °C, special microwave reactors able to withstand pressures of up to 80 bar have to be utilized (see Section 3.4.4). 

Pure zirconium metal is highly resistant to heat and corrosion, and it imparts these properties to its alloys. For these reasons it has become an important material in the aviation, aerospace, chemical, and surgical instrument industries, and in nuclear reactor technology. The ability of zirconium to reject neutrons is utilized for the protection of heating elements in pressurized water and hot water reactors (see also Rubel 1983, Deknudt 1988, Trueb 1990). 

Cold reference leg" water level instruments measure reactor vessel water level by measuring the differential pressure of two columns of water — the variable leg and the reference leg. The reference leg is maintained filled to a constant height of water by a condensate chamber located at the top of the reference leg. Non-condensible gases can collect in the condensate chamber and can become dissolved in the water at the top of the reference leg. These dissolved gases can be transported down the reference leg by small leaks in valves and fittings at the bottom of the reference leg. 

During transients and accidents in boiling water reactors, errors in the level measurement of the reactors pressure vessel can occur due to dissolved non-condensable gases which goes out of solution and due to boiling in the level measurement instrumentation lines. 

On November 26, 1993, the USNRC issued Information Notice 93-89, "Potential Problems witii BWR Level Instrumentation Backfill Modifications," to alert licensees to potential problems that have been identified involving hardware modifications to the reactor vessel water level instrumentation system. This information involved the potential to pressurize the reference legs of the water level instrumentation if a backfill system is installed with the injection point on the instrumentation side of the manual isolation valve in the reference leg. If that valve is closed inadvertently during backfill system operation, the closure could result in a severe plant transient. At some plants, valve closure would cause all safety relief valves to open and potentially impact ECCS response. Licensees were advised to review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. 

The use of programmable electronic systems is finding increasing use in Indian nuclear power plants. This paper reviews the evolution of the control instrumentation system in Indian pressurized heavy water reactors and highlights the areas where programmable electronic and computer based systems are used as well as details the plans for the future. 

Donaldson, M. R., and R. E. Pulfrey, 1979, Imaging Optical Probe for Pressurized Steam-Water Environments, Proc. Review Group Conf. on Advanced Instrument for Reactor Safety Research, USNRC, NUREG/CP-0007, III.17-1-27. (3)... 

Fail-safe is a concept used to specify the position of process instrumentation in the event of power, air pressure, or other utility failures. For instance, the valve supplying cooling water to a chemical reactor would fail in the open position ( fail open ) in the... 

Problems witbin tbe polisher unit caused operators to respond by attempting to unblock a cboked condition using instrument air. The air was at a lower pressure than the condensate and this caused water to enter the air system. This was not a standard procedure and the commercially supplied polisher unit was not built to standards consistent with the plant. Water in the instrument air system caused several instruments to fail and ultimately initiated a turbine trip. This interrupted heat removal from the radioactive core. The heat generation within the reactor was halted automatically within a few minutes by dropping metal rods to absorb neutrons within the core. 

Nuclear Boiler Assembly. This assembly consists of the equipment and instrumentation necessary to produce, contain, and control the steam required by the turbine-generator. The principal components of the nuclear boiler are (1) reactor vessel and internals—reactor pressure vessel, jet pumps for reactor water circulation, steam separators and dryers, and core support structure (2) reactor water recirculation system—pumps, valves, and piping used in providing and controlling core flow (3) main steam lines—main steam safety and relief valves, piping, and pipe supports from reactor pressure vessel up to and including the isolation valves outside of the primary containment barrier (4) control rod drive system—control rods, control rod drive mechanisms and hydraulic system for insertion and withdrawal of the control rods and (5) nuclear fuel and in-core instrumentation,... 

The oxidation of phenol and toluene was performed in a batch reactor at 348 and 353 K, using water and acetonitrile as solvent, respectively with a substrate to H2O2 mole ratio of 3. The oxidation of m-cresol, m-xylene, naphthalene and 2-methylnaphthalene was carried out in a stirred autoclave (Parr instruments, USA) of 300 ml capacity under autogenous pressure. Typically, 1.0 g of the catalyst and 5 g of the substrate in 20 g of acetonitrile/Hj20 (solvent) and appropriate quantity of aqueous H2O2 (26 % by wt.) (substrate to 1 202 of 3 mol) were placed in the reactor. After completion of the reaction (24 h), 25 g of acetone was added to the products, which were then separated from the catalyst by filtration and analysed by GC (HP 5880) using a capillary (cross-linked methylsilicon gum) column and flame ionization detector. TTie identity of some of the products was confirmed by GC-MS (Shimadzu, QP 200 A model). 

---