Reactivity limitations

Fig. 29 EM-profiles for competing intramolecular elimination and substitution from o- 0C6H40(CH2) 4Br [1] in 99% Me2SO as a function of the size n of the cyclic transition states. The point for the elimination reaction where n = 6 is an estimate for the upper reactivity limit. (Reproduced with permission from Dalla Corte/ al., 1983)...

Primary amines are obtained from ammonia, and secondary amines from primary amines. Alkylating agent must have good S 2 reactivity. Limitations are discussed in Section 23-9D. 

Fig. 27 EM-profiles for 8 2 cyclisation of (A) O(CH2) iCl and (A) HjNCCHjln-iBr (tak from Kirby, 1980) ( ) TsNlCHj),. jBr (Di Martino et al., 1985) (O) (EtO2C)2C(CH2) iBr. (Casadei et al., 1984 the point for the 3-membered ring is an estimate for the lower reactivity limit). (Adapted with permission from Di Martino et al., 1985)...

Reactivity-limited Bumup in PWR with Modified Scatter Fueling... 

Watt [W2] has used the computer codes CELL and CORE to evaluate the reactivity-limited bumup of a 1060-MWe PWR operated with modified scatter refueling as a function of the... 

Figure 3.11 Reactivity-limited burn-up versus number of fuel zones for various feed enrichments, 1060-MWe PWR, modified scatter refueling, steady state.

The bumup increases roughly linearly with enrichment. The dashed line shows that the variation of reactivity-limited bumup of 3.2 w/o enriched fuel with the number of fuel zones predicted by the simple Eq. (3.6) is a fair representation of the more accurate computer result. 

Despite the inability of these equations to represent accurately the concentration of hi er plutonium isotopes, the reactivity-limited bumup attainable from fuel initially containing 3.2... 

The reactivity equals zero at a burnup of 20,833 MWd/MT. This is in excellent agreement with the reactivity-limited burnup of 21,085 MWd/MT for batch irradiation of 3.2 w/o fuel in this reactor obtained by Watt [W2] using the computer codes CELL [B2] and CORE [Kl]. 

What weight percent should reload fuel have to permit this reactivity-limited burnup and operating cycle ... 

Coordinatively unsaturated transition metal complexes are known to bind to a variety of donor molecules. Qualitatively, the enthalpies of these interactions range from very strong dative bonds with ligands such as phosphines and CO to very weak interactions with saturated hydrocarbons. Despite the importance of these interactions in determining structure and reactivity, limited quantitative data exist for metal-ligand bond strengdis. 

The solutions for equations (6.19) and (6.21) behave as follows. At D = 0 (the non-reactive limit), the fixed point criteria for both the rectifying and stripping cascades reduce to the same equation... 

Criterion 28 - Reactivity limits. The reactivity control systems shall be designed with appropriate limits on the potential amount and rate of reactivity increase to assure that the effects of postulated reactivity accidents can neither (1) result in damage to the reactor coolant pressure boundary greater than limited local 5uelding nor (2) sufficiently disturb the core, its support structures or other reactor pressure vessel internals to impair significantly the capability to cool the core. These postulated reactivity accidents shall include consideration of rod ejection (imless prevented by positive means), rod dropout, steam line rupture, changes in reactor coolant temperatme and pressure, and cold water addition. 

A third way is to put a big variable-capacitor in series with the heater, because capacitive ("reactive") limiting of ac has no loss, at least with nearly-perfect capacitors. This method of controlling ac is hardly ever used, because capacitors that are variable and are "nearly perfect" (practically no ESR) would be very expensive to manufacture. (A similar concept will be described at the end of the next chapter, where a different kind of reactance is often used to control power.)... 

Excess reactivity limited to less than 1, that permits safe response to postulated insertion of all excess reactivity from power operating conditions ... 

In contrast to the case of FEP, a relatively small amount of vinyl ether is required to develop adequate toughness. There also is no reactivity limitation to vinyl ether incorporation, but this is unimportant in view of the minor amount of comonomer required. Superficially it appears that the difference in HFP and perfluoropropryl vinyl ether (PPVE), for example, lies in the structure and size of the side chain. This effect is illustrated quite effectively by comparison of the toughness of "TEFLON" FEP with that of "TEFLON" PFA at comparable molecular weights (Figure 3). The difference illustrated occurs despite the remarkably lower PPVE content of PFA. 

Which ONE of the following correctly identify the Technical Specification experiment reactivity limits for single unsecured and secured experiments respectively ... 

Core configurations are frequently changed in research reactors and these changes involve the manipulation of components such as fuel assemblies, control rods and experimental devices, many of which represent considerable reactivity value. Care has to be taken to ensure that the relevant subcriticahty limits and reactivity limits for fuel storage and core loading are not exceeded at any time. 

Reactivity Limit (AK/K) Reactor Period (sec) Reactor Cond it i on... 

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