Reactivity prompt-mode

We shall refer to as the prompt-mode reactivity. The two expressions presented in Eq. (28) for the prompt-mode reactivity can be used—one for its calculation in the perturbation formulation, and the other for its experimental determination. 

The GPT for eigenvalue problems developed so far pertains to integral parameters that are functionals of the static eigenfunctions. One of these parameters is the static reactivity. GPT can be extended to take into account perturbation in functionals of eigenfunctions other than the static eigenfunctions. We show here a GPT formulation for the prompt-mode reactivity [see Section II, Eq. (28)], as well as for the prompt-mode decay constant a. Applying the procedure used to derive Eq. (134) to Eq. (281. we find 49),... 

The asymptotic period and the prompt mode decay constant can be related more naturally to reactivities other than the static reactivity. The natural reactivities are related to real flux distributions in the subcritical reactor and to the importance function in the reference critical reactor. 

This article is concerned with one specific aspect of cluster organometallic chemistry, and describes the synthesis, characterization, structure, and reactivity of transition metal clusters containing alkyne, or alkyne-derived ligands. Alkynes display a diverse reactivity in their reactions with carbonyl clusters, and exhibit a wider range of coordination modes than any other simple, unsaturated molecule. It is this compelling diversity that has prompted the authors to undertake this review. 

The biological utilization of phosphate derivatives is of utmost importance. Phosphate diesters form part of the backbone of DNA. The phosphate derivatives and anhydrides, in particular ATP, are the main method of energy transduction in the cell and phosphorylation of proteins is a key step in the regulation of some metabolic pathways. In contrast to their reactivity in biological systems, phosphate derivatives are generally un-reactive in laboratory conditions. A striking feature of many of the enzymes in this area is that most of them are metalloenzymes or require metal ion cofactors (108). This observation prompts the question. Do metal ions have a special effect on the reactivity of phosphate derivatives or are they merely used in a structural role (140) A number of mechanisms by which metal ions could conceivably facilitate the reactions of phosphate derivatives are fairly obvious and include the six modes listed below. 

The quantity k t) is the excess prompt reactivity and I is the prompt generation time. The small time variation of Z will be ignored throughout. The assumptions that all power is in the fundamental mode shape and that I is independent of time seem unlikely to lead to serious error, but do represent potential weaknesses in the argument. The equation for the time variation of power when a neutron source is present can be written ... 

However, power reactors require significant amounts of reactivity (i.e., well above the amount needed to go prompt critical if added suddenly) that must be provided by movable control absorber devices (or removable poison dissolved in the piimaiy coolant) under the direction of a licensed operator and following jq>proved procedures during reactor start-up and the transition to equilibrium full-power operation. This positive reactivity is needed to compensate for losses associated widi increased core temperature, reduced coolant density including bubble void formation, and equilibrium fission product poison loads, especially Xe. Consequently, it is only possible to limit the amount of reactivity that could theoretically be inserted to small, intrinsically safe values when the reactor is already in the normal full-power operating mode with all movable control devices very near their maximum withdrawal positions (and when the dissolved poison concentration is close to zero). 

Pulsed reactivity measurements were made, in the Subcritical Eiqperiment Facility at the vannah River Laboratory. A rigid aluminum support frame maintained accurate spacing within the arrays. The lattices were tolly flooded to achieve an effective infinite H2O reflection. A KAMAN modei A-800 puised-neutron generator was located at the mhtotone 15 cm from toe core. Neutron detectors were placed in the low importance region on toe radial centerline of representative fuel assemblies. The measured fundamental-mode prompt-neutron decay constant, (meas), was determined by standard pulsedineutron techniques (Table I). 

---