Shutdown history

The number and severity of failures experienced by the equipment under study must be related to the operations of the facility. It would be inappropriate to assign the same operating histories to a continuously operating system and a system that operates intermittently. The number of hours in different operating modes (for example, 100% production versus shutdown) affect failure rate calculation and service description for taxonomy definition. 

A further complication arises from the age of the weapons as well as their varied history— leakers" and "gelled agents require changes in standard" operations, for example. The shutdowns and restarts resulting from these feed stock variations can be planned for and shutdown times can be minimized. 

Specific information about the operating histories of SGIs associated with the 11 discarded PWRs remains classified. The year of start-up and shutdown and the fuel bumup for each PWR is currently known, as is the fact that all contained their initial fuel load at the time of final shutdown. Start-up dates covered the ten year period from 1958 to 1968, with the earliest date that for submarine factory number 254 and the latest date that for submarine factory number 421. Shutdown dates covered the seven year period from 1961 to 1968, with the earliest date that for submarine factory number 901 and the latest date again that for submarine factory number 421. The longest period of SGI operation was four years and is that for submarine factory number 254. While the shortest period of SGI operation was one year and is that for submarine factory numbers 901 and 421. Fuel bumup for the PWRs varied from a low of 1250 MW-d for submarine factory number 421 to a high of 3880 MW-d for submarine factory number 254. 

The behavior of all six compartments was considered in constructing the curves. The extent of the interpretive fairing applied to the data is illustrated by Fig. 12, which presents the raw data for three adjacent compartments covered by insulations with different thermal performance. Each data point on the curves of Fig. 12 represents every fourth tank boil-off cycle. The triangles and vertical lines on the figure represent the times when the tank was allowed to warm up for inspection and weekend shutdown. It is readily apparent from a comparison of the boil-off histories of the three compartments, that boil-off times for the better insulation (compartment 3) tends to mirror the performance of the poorer performing adjacent insulations (compartments 2 and 4). It is only... 

As noted previously, K-Reactor in Cold Standby will maintain a startup capability but with no planned provision for restart while L> and P>Reactors will remain in a Cold Shutdown mode. Cold Standby operations of K Reactor will be the continued storage and handling of unirradiated fuel and irradiated co )onents and the storage and processing of contaminated moderator. L> and P-Reactor Disassembly Basins operations will be the continued storage and handling of irradiated components. As such, the history of SRS production reactors offers examples of the histoty which might be expected in this continued use. 

The alternative release scenario could include a worst-case release amount but with passive (e.g., dikes or sumps) or active responses (e.g., a deluge system, emergency shutdown system) in place, or a release based on past history. The modeling is done under either typical meteorological conditions or a D atmospheric stability and a wind speed of 3 m/s. 

The danger of errors in the experimental determination of the thermal neutron fluence caused by other nuclear reactions is small. Co is also produced in stainless steels by (n,p) reaction from Ni and by (n,a) reaction from Cu, with both reactions being induced by fast neutrons. Since the cross sections of both reactions are very small (5 10 cm and 4.2 10 cm respectively), no interference is to be expected in light water reactors when monitor materials of the usual purity are used. Due to the 5.28-year halflife of Co, details of the irradiation history of this monitor material can only be neglected at gross irradiation periods of up to one year for longer periods, interruptions in the operation history of the plant, such as shutdowns, load reductions etc., have to be corrected for. 

Based on the history of RLOC operation records, Methane Run duration requires 2 days for each plant startup and shutdown. Comparing RLOC with other facilities in Qatar, flaring duration when using the Normal procedure requires 7-8 days for each startup and shutdown. Following Methane Run procedure reduces the downtime of planned maintenance and start up activities by two weeks. Based on the two main assumption mentioned above and the adaptations of the new Methane Run startup and shutdown procedure, it was found out that the time required to shut down and startup was reduced by upwards of 70%. Moreover, the flared quantities were reduced by nearly 70% in the startup process and about 80% for the shutdown period (Figure 3). 

At the time of shutdown, there exists a particular combination of iodine and xenon concentrations in the reactor. This combination depends, of course, upon the operating history (i.e., flux program) as indicated by Eqs. (9.268) and (9.271). In any case, these can be determined in detail, by measurement if necessary. The concentrations after shutdown are obtained by setting = 0 and letting / = 0 be the instant of shutdown. Then,... 

Describe xenon and samarium transient behavior for the following power histories (1) startup to steady state power ( ) shutdown from steady state (3) startup near peak shutdown concentration (4) decrease in power after prolonged operation at steady state and (5) Increase in power after prolonged operation at steady state,... 

When a reactor is shutdown, the neutron flux decreases to a low level which can be treated as if it were zero. In the xenon balance in Figure 8.1, the fission yields and burnout decrease to near zero. Xenon is produced only by iodine decay and depleted only by its own radioactive decay. The iodine which decays to become xenon is an amount that built up within the reactor during operation, so it is dependent upon past power history and neutron flux. After 48 hours of steady state reactor operation, the amount of iodine present in the reactor is I in equation (8.3). Equations (8.1) and (8.2) become ... 

Attempts to implement nondestructive quality control for carbon cathode blocks and to reveal internal defects has a 40+-year history, and we cannot say that these attempts have stopped. Typically, the next attempt to implement another nondestructive method of quality control starts after a series of imexpected shutdowns. These attempts are initiated by customers, but producers also carry out research in this direction. Another question to discuss is where should the nondestructive control device be placed near the producer s storage house or at the customer s quality control ... 

The decay heat generation is represented versus time in Fig. 7.15. The MSFR design implies that FPs are present in two different places when the reactor is stopped. Some are in the liquid-fuel salt and some in the gas processing unit. Approximately one-third of the heat is produced in the gas processing unit and two-thirds in the liquid fuel. The power of both heat sources decreases rapidly (by a factor of 10 in 1 day) from the value at shutdown, which depends on the history of power generation. The total amount of power at shutdown is approximately 5% of the nominal power. This value is lower compared with solid fuel reactors because FPs are continuously removed in this concept. 

Corrosion damage in steam generator tubes. The history of corrosion damage in steam generator tubes has been described in detail elsewhere. The problems have mainly been related to Alloy 600 (a Ni, Cr, Fe alloy) and have contributed to seven steam generator tube ruptures, numerous forced reactor shutdowns, extensive repair and maintenance work, steam generator replacements, and also radiation exposure of plant personnel. A brief summary follows. 

Inspection and maintenance for steam generator tubes. The SCOpe and fi equency of steam generator tube inspections depends on the operating history of the individual plant. In cases where operating records show extensive tube degradation, all the tubes are inspected at each shutdown. Modem inspection techniques are listed in Table 6.4, and Table 6.5 shows what... 

A review of an alarm history has identified that the bad actors include level, pressure, and temperature alarms that are associated with a liquid-phase, continuous, stirred-tank reactor. The chemical reactions are exothermic, and the CSTR is used at different times to make two products, A or B. The low-level and low-pressure alarm violations occur mainly during shutdown operations, whereas high temperature alarms for the jacket cooling water occur primarily when product B is produced. It is desirable to devise a strategy for reducing these bad actor alarms. 

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