Reactor shutdown

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). 

Initiating events, in this study, initiate plant scram or setback. Other initiators, such as refueling discharge accidents, do not necessarily cause a reactor shutdown but may lead t< minor fuel damage and radioactive releases. The list of initiators for nuclear power plants has litf ance for HFBR because of size and design differences. A list of HFBR-specific initiators was developed from " st prepared with the HFBR staff, the FSAR, the plant design manual, the procedures manual, techn specifications, monthly operating reports, and the HFIR PRA (Johnson, 1988). 

Atkinson. S. A., 1996, PSA-Operations Synergisms for Advanced Test Reactor Shutdown Operations PSA, Proceeding of the Int ——1 Topical Meeting on Probabilisl ety Assessment, Park City, Utah, pp 600-6 29-Oct. 3. 

This event tree analysis shows that a dangerous runaway reaction will occur on average 0.025 time per year, or once every 40 years. This is considered too high for this installation. A possible solution is the inclusion of a high-temperature reactor shutdown system. This control... 

Dust explosions (ASTM E789) that can occur during catalytic reactor shutdown and cleaning are due to the production of finely divided solids through attrition. Many catalyst dusts can bum explosively in air. Thus, control of dust generated by catalyst attrition is essential (Mody and Jakhete, 1988). 

Figure 9.18 Plot of PC 1. Sensor B was used as the lump formation started in chamber I. Acoustic warning appears as early as 15 57, approximately 30 min before reactor shutdown. Compare with Figure 9.19, which shows the same situation based on traditional process measurements only.

Days after nuclear excursion or reactor shutdown... 

Availability Not clear. Process heat loop is on back side of PCU farther from reactor core but is tightly coupled to PCU. So disturbance in process heat loop affects PCU directly and could cause turbine to trip leading to reactor shutdown. 

Investment protection Superior. The need to keep electrolytic cells at temperature even during reactor shutdown is more easily met if cells are heated by electrical heaters or hydrogen combustion products as is proposed for plant design that uses low temperature process heat loop. 

A catalyst for a particular chemical transformation is selected using knowledge of similar chemistry and some level on empirical experimentation. Solid catalysts are widely used due to lower cost and ease of separation from the reaction medium. Their drawbacks include a possible lack of specificity and deactivation that can require reactor shutdown for catalyst regeneration or replacement. 

Nuclide Ti/2 Hold-up time after reactor shutdown, year ... 

When transferring SFAs, the supplier executes and submits the relevant certificates for SFAs in shrouds to representatives of the reprocessing plant. Such certificates include initial characteristics, power generation data, core number, date of the first putting into operation and that of the last reactor shutdown before SNF imloading, the operational documentation of the relevant reactor installation being the source of such data. 

Quality variations in the polymer produced in bstch reactors are often caused by slight variations in the reactor start up procedure. Furthermore, the polymerization rate may change considerably during the batch and this may give tempetature variations that are difficult to reproduce causing batch-to-batch variations in quality. These problems would be minimized with CSTRs if the continuous reactor system could be operated for at least several weeks before wall fouling and coagulum buUd up become critical and require reactor shutdown for cleanup. If an effective start-up procedure for a continuous reactor train is not available, the costs associated with offspec material could make continuous operation uneconomical. In addition, with a continuous reactor system one loses the flexibility of batch reactors when a multiproduct operation, with its short productions runs, is involved. 

Continuous catalyst addition and withdrawal Is probably the most practicaf means to maintain constant production in a slurry methanol reactor. It gives the plant operator the flexibility to trade off catalyst replacement cost against methanol production rate, and It avoids the total reactor shutdown that is required to change Out a deactivated fixed-bed catalyst. 

Two independent reactor shutdown systems are foreseen. Both systems are assumed to be located in the graphite blocks of the side reflector. When called upon, the neutron absorber elements are assumed to fall into the designated channels located in the side reflectors, driven by gravity. 

Time after reactor shutdown, s Decay-heat power E ( . t), (MeV/s)/ (fission/s) Percent uncertainty... 

To calculate the growth and decay of these nuclides after reactor shutdown, the assumed equilibrium amounts at the time T of shutdown are calculated as above, using Eq. (2.114). These become the initial amounts for application of the batch decay, Eq. (2.18) for time t after shutdown. During shutdown the branching and convergence involving neutron reactions disappear, and we have only four simple linear chains to solve by applying Eq. (2.18). 

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