Control worth

The number and location of the top entry control rods and the diverse reserve shutdown control have been specified to assure that the reactor thermal power is controlled both for normal and off-normal conditions. The radial thickness of the active core annulus was specified on the basis of assuring that the control rod worths of the reflector-located rods would meet all shutdown and operating control worth requirements. The choice of reflector control, coupled with the choice of a control system withdrawal sequence and safety classification was made to assure that the control rod integrity is maintained during passive decay heat removal. 

Nominal Reactivity Control Worths The calculation of control rod and reserve shutdown control (RSC) worths under both hot and cold conditions have been performed for both the initial cycle BOG conditions and the equilibrium cycle EOC condition. In addition, the worth of all 30 control rods has been calculated for other times in cycle for both the initial core and an equilibrium reload cycle to determine how the total control rod bank worth is expected to change over the cycle. Other specific rod pattern control worths for hot conditions for the selected withdrawal of groups of three rods each in the outer bank of control rods were analyzed to define the maximum group worth for use in the transients analyzed in Chapter 15. These calculations were only performed for the EOC equilibrium core loading since that cycle condition yields the minimum temperature coefficient of reactivity and the maximum rod group reactivity worth for a rod group withdrawal transient. No reduction in control rod poison worth due to burnup has been assumed in this or other EOC rod worth calculations discussed below, although this effect would be minimal. 

Similar nominal values of the calculated control worths for the initial core and at other times in cycle have been combined with selected values for the EQ-EOC conditions and are given in Table 4.2-7. 

Experiments carried out in Assembly-51 were devised to check computational models and to measure parameters related to the design and safe operation of the FTR. These included critical mass, spatial activation and small sample reactivity distributions, sodium voiding, spatial dcpendcAce of neutron spectra, central reactivity worth measurements, fuel compaction, and reactivity control worths. 

TABLE X-12. REACTIVITY CONTROL WORTH (Keif AND NA2B4O7 CONCENTRATION AT 20°C)... 

Considerable research efforts have been undertaken to develop reliable and cost-effective means to actively (or electronically) control noise produced by equipment. Though it is not a new concept, modem theory and hardware for adaptive digital signal processing have recently made the commercial use of active noise control worth considering for certain appU-cations with special requirements. 

It is worth noting that typically personnel and logistics represent 30% to 50% of operating costs while maintenance costs represent 20% to 40% of operating costs. These are particular areas in which cost control and reduction should be focused. This may mean reviewing the operations and maintenance philosophies discussed in Section 11.0, to check whether they are being applied, and whether they need to be updated. 

Pests and Insecticides. The most destmctive pests of the cotton plant are the boU weevil and the boUworm/budworm complex. They are serious threats to the cotton industry in countries around the world. The boU weevil migrated from Mexico around 1892 and spread over the entire cotton belt within 30 years. The domestic cotton crop lost to the weevil is worth 200 million a year. In addition, about 75 million a year is spent for pesticides to control this destmctive pest (8). Unfortunately, some insecticides used to control the weevil kill many beneficial insects. Among the undesired casualties are insects that help to control the boUworm and the tobacco budworm, pests that cause another 200 million loss in cotton. 

Noise control is worth mentioning. The turboexpander and axial compressors are noise producers and consideration must be given to the need for providing noise abatement. Silencers on vents and noise insulation housings on machines should be considered and have been proven effective. 

There is an old saying among pollution control engineers that practiced pollution prevention long before it became fashionable. That saying is - If you see a dollar lying on the ground, it s worth your while to bend over and pick it up - but NOT if you have to break your back to do it. ... 

The low-power-density, low enrichment reactor core uses soluble boron and burnable poisons for shutdown and fuel bumup reactivity control. Low worth grey rods provide load following. A heavy uranium flywheel extends the pump coastdown to allow for emergency action during loss-of-flow transients. 

Having decided on the appropriate way to proceed with the project, the owner needs to satisfy himself that adequate system and procedures have been put in place to give him the necessary control and confidence in the project. These will, of course, vary considerably from owner to owner and project to project, but certain key points are worth remembering. 

HARRIS, c. M., Handbook of Noise Control, McGraw-Hill, Newark, 1957 BRUNDRETT, G. w.. Handbook of Ddiumidification Technology, Butter worths, 1987... 

In the final analysis, market price and sales volume are functions of the quality standards offered and the buyer s degree of confidence that the product will conform to the standards. Maintenance of buyer s confidence requires inspection to screen out all nonconforming products, or control over variability of quality during production and distribution to a degree where few, if any, products fail to meet the standards. Screening inspection of the finished product cannot improve quality it merely serves to segregate unacceptable from acceptable product, and results in loss of production capacity and costly waste and salvage. The second consideration provides the only sound basis for quality control in frozen food production and distribution. It operates on the old principle that an ounce of prevention is worth a pound of cure. ... 

As a preamble to looking at some of these specific problems, it is worth reiterating effective control strategies are achieved through the planned avoidance of problems and understanding cause-and-effect relationships. 

Despite global use of free caustic programs, however, it is worth noting that good control over the caustic reserve and other factors is still very necessary to prevent the development of localized and highly concentrated deposits of caustic that may cause specific and very damaging caustic gouging corrosion. Such problems are usually associated with power WT boilers but, in fact, also may occur readily in FT boilers. 

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