Initial Fuel Loading

Fig. 6. Initial fuel loading of PWR showiag the three enrichments where ( ) represents 3.10 wt % ( ) 2.60 ( ) 2.10 and (0) the cluster openings of...

The third control is by use of a fixed burnable poison. This consists of rods containing a mixture of aluminum oxide and boron carbide, included in the initial fuel loading using the vacant spaces in some of the fuel assembhes that do not have control clusters. The burnable poison is consumed during operation, causing a reactivity increase that helps counteract the drop owing to fuel consumption. It also reduces the need for excessive initial soluble boron. Other reactors use gadolinium as burnable poison, sometimes mixed with the fuel. 

Two cores had 6-% fuel enrichment, the remaining cores 21 % enrichment. Mean fuel load therein was equal to 46.8 kg. According to specifications, maximal fuel bumup made up 20 % of the initial fuel load on average. 

A4 5.1 Critical Hsiss Determination. Several extraordinary safety precautions were taken for the initial fuel loading. For instance, a standard safety rod was rebuilt with a beryllium section in place of the fuel section... 

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. 

Design Basis Accident analysis codes PREDIS and VENUS have been validated against European LOFA benchmark problems. Fuel subassembly worths at different radial positions in core during initial fuel loading were calculated. A study was made on the possibility of recriticality of molten fuel dropped in the core catcher from the core following an accident. Calculations of neutron irradiation dose for the reactor assembly out of core componets both in radial and axial locations were completed and indicated that the dose values are negligible ( ldpa). 

The applicant should submit an "Application for Initial Fuel Loading of Nuclear Power Plant" together with the "Final Safety Analysis Report" to the NNSA for an "Instrument of Ratification for the Initial Fuel Loading". 

Pattern of initial fuel load, three regions. 

The BWR is the only light water reactor system that employs bottom-entry control rods. Bottom-entry and bottom-mounted control rod drives allow refueling without removal of control rods and drives and allow drive testing with an open vessel prior to initial fuel loading or at each refueling operation. The hydraulic control rod drive system, which incorporates... 

Japan has a long-term national plan to introduce sodium-cooled fast breeder reactors (FBRs) for effective utilization of natural uranium to provide their initial fuel load, plutonium will be extracted from the spent fuel of existing light water reactors (LWRs). 

A fast neutron spectrum potentially allows the BN GT-based system with fuel recycling to produce energy consuming only depleted uranium, but such a system is currently less economically competitive than that employing spent PWRs MOX fuel as the initial fuel load. 

An alternative initial fuel loading option for the ENHS reactor is enriched uranium. With approximately 12.7 weight % the ENHS core will be FSS [XX-36]. The discharged fuel could be recycled many times using a similar strategy outlined above. 

The ENHS reactor is FSS. That is, the in-core fissile fuel inventory is kept nearly constant over core life and then recycled as many times as one wishes. The only feed after the initial fuel loading is either depleted uranium, uranium extracted from fuel discharged from LWRs, or natural uranium. 

Fuel discharged from LWRs is to provide the initial fuel loading for the ENHS core. The LWR discharged fuel is converted to the ENHS feed fuel by removing most of the fission products and approximately 90% of the uranium. The entire inventory of plutonium and minor actinides to be accumulated in the USA until 2030 could be stored in the cores of-400 ENHS modules. 

In order to ensure safety, an adequate degree of fire protection should be provided in nuclear power plants. A fire hazards analysis including consequences of fire fighting should be performed before initial fuel loading and be updated during operation to verify that the main safety functions to shut down the reactor, to remove residual heat, and to contain radioactive material are maintained against the consequences of a fire. 

The overall objective of the commissioning is to demonstrate that the plant has been constructed as designed, that the systems performance is consistent with the plant design, and that activities which culminate in operation at full licensed power are performed in a controlled and safe manner. These activities include initial fuel load, initial criticality and power ascension. 

Following construction and installation testing, pre-operational commissioning is performed to demonstrate that equipment and systems perform in accordance with design criteria so that initial fuel loading, initial criticality and subsequent power operation can be safely undertaken. Pre-operational tests at elevated pressure and temperature are referred to as hot functional tests. 

The schedule for the initial fuel load and for each maj or phase of the conunissioning includes the timetable for generation, review and approval of procedures as well as the actual testing and... 

Initial fuel loading and subsequent initial criticality and power ascension to full licensed power are performed during the start-up commissioning. Prior to the initiation of these operations, the systems and conditions necessary to bring the plant into compliance with the Tech-Specs (Chapter 16 of the EDCD, Reference 10.3 must be operable and satisfied. These operations are performed in a controlled and safe manner by using test procedures that specify ... 

Because of the unique conditions that exist during initial fuel loading, temporary neutron detectors may be used in the reactor pressure vessel to provide additional reactivity monitoring. Credit for the use of temporary detectors may be taken in meeting Tech-Specs requirements on the number of operable source range channels. 

Following initial fuel loading, the reactor upper internals and the pressure vessel head are installed. Additional mechanical and electrical tests are performed in preparation for critical and power operations. The following conditions exist prior to initial criticahty ... 

For the initial fuel loading, the assemblies in the inner and outer regions of the core itself contained fuel having equivalent plutonium contents of 21 %... 

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