Effect of operating temperature on LMFBR core performance

Abstract

MASTER pSTHBCflON OF THIS DOCUMSTT IS TOLIMtED , * Eliminated in later designs. ** Diameter increase required to equalize power of low and high temperature designs. *** Should be studied. * Thermal power of normalized designs held constant. ** All values normalized to load factor of 801. 2.7 the three contractors. For the purposes of this study, each contractor was asked to put forward a single high or low tenperature design to contrast with their reference design. This vas done in order to simplify the evaluation procedure. It was agreed that the inportant effects could be observed by looking at the difference between these single high and low tCTperature designs. The combination of fuel cycle costs, capital costs, and unavailability costs were used for selection of either a high or low tenperature design by each contractor. Economic factors were placed ahead of other considerations as is appropriate. In this study, attention is focused, first of all, on the fuel cycle costs, and then on those capital costs which are directly attributable to differences in core design. AI and GE see an inprovement in fuel cycle costs as the temperature is decreased. The WARD analysis shows an increase of fuel cycle costs with decreased temperature and the normalized designs show a small increase with decreased tenperature. These cost differentials come about by a relatively complex interaction among several variables which change as tenperature is changed. The main effects, however, are the change of theimal efficiency, the change of fuel lifetime, and in the case of GE, the change of fuel pin diameter and linear power. AI calculates an increased fuel lifetime sufficient to override the effect of decreased thermal efficiency. WARD, on the other hand, calculates no increase of fuel life; consequently, WARD'S fuel cycle costs increase as operating tenperatures are reduced. Calculations made using the normalized designs, indicate that these two factors are in fairly close balance and the net result is a very small change of fuel cycle cost. GE's net result comes from the interaction of a larger nimber of parameters. The most interesting result found in analyzing GE's design is the fact that fuel lifetime does not increase a great deal as the operating tenperature of the core is reduced. This comes about because of the relatively poor cooling strategy adopted by GE. Cladding and duct tenperatures in the General Electric cores are substantially higher than those of the other designers, and furthermore, for the GE low tenperature design, increased bypass flow makes the clad and duct tenperatures extraordinarily high for a low tenperature design. Nevertheless, some inprovement

Core Outlet Temperature Study

“…The superheated steam (SHS) cycle is the reference power conversion plant for the ABR-1000 [1]. For this work, the cycle is modeled with GateCycle 6.0 software [2]. The main assumptions used for the model development are presented in Table 2.…”

“…This steady-state approach to analyze this accident is commonly used in the reactor analysis. In fact, a peak channel design analysis usually includes 15% overpower factor [2,7] to account for exactly this type of event. The results presented below basically repeat the peak temperature analysis above with an introduction of the 15% overpower factor.…”

“…Therefore, the decision on whether higher temperatures provide a net benefit to the reactor is always based on the trade-off between the benefits of the higher electricity production and drawbacks of reduced safety margins as well as any potential cost increase associated with elevated temperatures. A side-byside comparison of the designs with different temperatures, such as one carried out in Reference [2] is usually the best approach to find the optimal operating conditions. This side-by-side comparison however requires not only detailed design analysis at each operating conditions, but also a very accurate reliable cost analysis methodology.…”

“…This side-by-side comparison however requires not only detailed design analysis at each operating conditions, but also a very accurate reliable cost analysis methodology. For example, the results of the study presented in Reference [2] conclude that the overall net cost of electricity from reactors designed for two different core-outlet temperatures, 875 °F (470 °C) and 950 °F (510 °С), is very close The difference is so small that depending on the organization carrying out the analysis, the higher temperature design was shown to be either beneficial or disadvantageous.…”