Reactors maintenance

The moderator system includes two 100% capacity pumps, two 50% flow capacity heat exchangers cooled by recirculated light water, and a number of control and check valves. Connections are provided for the purification, liquid poison addition, D2O collection, supply, and sampling systems. The series/parallel arrangement of the moderator system lines and valves permits the output from either pump to be cooled by both of the heat exchangers and ensures an acceptable level of moderator cooling when either of the two pumps is isolated for maintenance. Reactor power must be reduced to about 60% if one moderator heat exchanger is isolated. The primary functions of the system are to... 

Reactor design Reactor mock-up Reactor remote maintenance Reactor construction and operation... 

Furnaces should be located at a safe distance and upwind from unrelated equipment containing hydrocarbons. Steam drums or deaerators can be located as required for operation and maintenance. Reactors can be located closer to furnaces than other equipment containing hydrocarbons, as long as adequate ce is... 

A special committee, the Joint Test Group (JTG), was specified in the master plan to provide independent review and approval of program activities. Membership of the JTG includes experienced personnel from Reactor Operations, Reactor Engineering, Maintenance, Reactor Quality Engineering, and the commercial nuclear industry. The DOE participates in JTG activities as a non-voting member. This board participation provides a key basis for a safe and effective startup program. 

Corrosion of reactors used for functionalization and ia pipes and valves along transferlines for sulfuric acid is a problem that results ia maintenance shutdowns. Sufficient agitation is needed to keep the resia beads fluidized duting sulfonation. As for copolymer kettles, transfer lines should be sufficiently large to allow reasonably rapid transfer of Hquids and resia slurries. 

Eig. 8. Cost of electricity (COE) comparison where represents capital charges, Hoperation and maintenance charges, and D fuel charges for the reference cycles. A, steam, light water reactor (LWR), uranium B, steam, conventional furnace, scmbber coal C, gas turbine combined cycle, semiclean hquid D, gas turbine, semiclean Hquid, and advanced cycles E, steam atmospheric fluidized bed, coal E, gas turbine (water-cooled) combined low heating value (LHV) gas G, open cycle MHD coal H, steam, pressurized fluidized bed, coal I, closed cycle helium gas turbine, atmospheric fluidized bed (AEB), coal J, metal vapor topping cycle, pressurized fluidized bed (PEB), coal K, gas turbine (water-cooled) combined, semiclean Hquid L, gas turbine... 

In the early years of reactor development, electricity from nuclear sources was expected to be much cheaper than that from other sources. Whereas nuclear fuel cost is low, the operating and maintenance costs of a nuclear faciHty are high. Thus on average, electric power from coal and nuclear costs about the same. 

The development of computer capabiUties in hardware and software, related instmmentation and control, and telecommunication technology represent an opportunity for improvement in safety (see COMPUTER TECHNOLOGY). Plant operators can be provided with a variety of user-friendly diagnostic aids to assist in plant operations and incipient failure detection. Communications can be more rapid and dependable. The safety control systems can be made even more rehable and maintenance-free. Moreover, passive safety features to provide emergency cooling for both the reactor system and the containment building are being developed. 

Economy of time and resources dictate using the smallest sized faciHty possible to assure that projected larger scale performance is within tolerable levels of risk and uncertainty. Minimum sizes of such laboratory and pilot units often are set by operabiHty factors not directly involving internal reactor features. These include feed and product transfer line diameters, inventory control in feed and product separation systems, and preheat and temperature maintenance requirements. Most of these extraneous factors favor large units. Large industrial plants can be operated with high service factors for years, whereas it is not unusual for pilot units to operate at sustained conditions for only days or even hours. 

Bubble columns in series have been used to establish the same effective mix of plug-flow and back-mixing behavior required for Hquid-phase oxidation of cyclohexane, as obtained with staged reactors in series. WeU-mixed behavior has been established with both Hquid and air recycle. The choice of one bubble column reactor was motivated by the need to minimize sticky by-products that accumulated on the walls (93). Here, high air rate also increased conversion by eliminating reaction water from the reactor, thus illustrating that the choice of a reactor system need not always be based on compromise, and solutions to production and maintenance problems are complementary. Unlike the Hquid in most bubble columns, Hquid in this reactor was intentionally weU mixed. 

Existing maintenance procedures must be reviewed for several reasons. Typically, these are established based upon manufacturers recommended practices for stock equipment such as pumps, centrifuges and some reactors. However, a new toll can introduce special cleaning and preparation steps as well as possible material of construction incompatibilities. If the toller is using new equipment, special maintenance practices and tools may also be required. 

Tolling presents a special consideration that can make the training step easier. Typically a toller s technical staff, operators and mechanics are knowledgeable in the basic operations and tasks related to the toller s specialty. For example, experienced operators may know operations of the reactors, columns, exchangers, and packaging equipment quite well. The mechanical personnel may be very familiar with the required safe work practices, equipment cleaning procedures and maintenance tasks for standard vessels and piping. 

Air-eooled dry type and oil-immersed type This will depend upon the size of the reactor and the design of the manufacturer. The latest practice is to use aircooled dry type, which call for lesser maintenance and are free from any fire hazards. 

Many applications of novolacs are found in the electronics industry. Examples include microchip module packaging, circuit board adhesives, and photoresists for microchip etching. These applications are very sensitive to trace metal contamination. Therefore the applicable novolacs have stringent metal-content specifications, often in the low ppb range. Low level restrictions may also be applied to free phenol, acid, moisture, and other monomers. There is often a strong interaction between the monomers and catalysts chosen and attainment of low metals levels. These requirements, in combination with the high temperature requirements mentioned above, often dictate special materials be used for reactor vessel construction. Whereas many resoles can be processed in mild steel reactors, novolacs require special alloys (e.g. Inconel ), titanium, or glass for contact surfaces. These materials are very expensive and most have associated maintenance problems as well. 

Minimum cyclone diameter is about 3 ft. based on maintenance considerations. Most cyclones are installed inside reactor vessels, and problems of geometric layout of multiple cyclones also can affect the size and hence the number of cyclones selected. 

The accident resulted from a routine safety test of some electrical control equipment at the start of a normal reactor shutdown for routine maintenance. The test was to determine the ability to continue to draw electrical power from a turbine generator during the first minute of coast-down following a station blackout. In a blackout, the reactor automatically scrams and diesel generators start to assume load (about 1 minute required). 

The cause of the explosion, which also left four people seriously injured and 31 others with minor injuries, is unknown. A Hoechst Celanese spokesman says that the first blast occurred near a gas-fired boiler and the second blast at a nearby reactor in which butane is reacted with steam to produce acetic acid. The 35-year-old plant employs 600 persons, 150 as contract maintenance and construction workers, but the blasts on Saturday only involved a weekend crew of 60. 

A reactor was prepared for maintenance and washed out. No welding needed to be done, and no entry was required, so it was decided not to slip-plate off the reactor but to rely on valve isolations. Some flammable vapor leaked through the closed valves into the reactor and was ignited by a high-speed abrasive wheel, which was being used to cut through one of the pipelines attached to the vessel. The reactor head was blown off and killed two men. It was estimated that 7 kg of hydrocarbon vapor could have caused the explosion. 

The vessel had been prepared for maintenance in a similar way on three previous occasions, but there was then far fewer granules in the reactor [14] (see Section 11.1 a and b). 

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