Atomic Energy, Vol. 85, No. 6, 1998
FUEL EFFICIENCY OF RBMK REACTORS
A. V. Krayushkin, Yu. A. Tishkin, and S. M. Tsareva
UDC 621.039.54
Fuel efficiency is an important aspect of reactor operation, since it has a decisive influence on the economic efficiency of atomic power plants. The operation of a large number of RBMK reactors currently permits the determination of a criterion for estimating their economic performance and the formulation of recommendations for improvement. The main comparative characteristic is fuel burnup, determining the rate of recharging and hence the consumption of the fuel rods. However, this characteristic is only applicable in identical conditions of reactor charging (fuel enrichment, number and design of moderators, etc.). Currently, the charging of RBMK reactors is significantly different (Table 1), and therefore comparison of the corresponding burnup is inexpedient. Another comparative measure of the fuel efficiency is the leakage of neutrons from the reactor. This is a universal characteristic, since it does not depend on the charge composition; it is determined by the form of the energy-liberation field. The formation of this field is a controllable process, since it depends on the fuel recharging and the position of the control rods. The neutron leakage of RBMK reactors may be calculated by means of the STEPAN full-scale three-dimensional neutron-thermohydraulic program. In the calculation, the energy liberation field is constructed on the basis of the readings of sensors over the radius and the height. The mean (over 2-3 states for each unit) total leakage for each stage is shown in Table 2, along with the radial and axial components. It follows from the results that atomic power stations may be divided into two groups on the basis of the neutron leakage. The first group includes the Chernobyl, Ignalinsk, and Leningrad power stations, for which the mean (over the station) total leakage (radial and axial) is 2.04-2.1%. For the second group (Kursk and Smolensk power plants), the mean total leakage is around 2.27%. The third unit of the Smolensk power plant is in a category of its own, with a total leakage of 2.43%. Thus, the difference in the total leakage between the groups of reactors is -0.4%. This corresponds to a 2% loss in the fuel burnup, which increases the fuel-rod consumption by approximately ten per year for each unit.
TABLE 1. Charging of Reactors and Theoretical Mean Energy Yield Number of loading elements Atomic power
additional absorber water column
regular
Chernobyl lgnalinsk
2 5-6
Kursk Leningrad Smolensk, unit 1-2 3
pIant
cluster
2% enrichment
2.4% enrichment
65 0-1
28 17--45
78 0
1488 0
1-22 2-10
2-99 15-81
0-77 0--42
473-782 0-9
2-7 1-6
36-60 90-93
19--42 0
0 0-233
Variation in mean
fuel
2477-01
with erbium absorber
manual control rods
energy release, MW-day/fuel rod
21 24-48
1235.4 827-1038
2% enrichment forRBMK-100C forRBMK-1500 uith beat-transfer reactor reactor intensification
0 0
0 0 140-752 873-1449
784-1113 0 1226--1572 0-392
0 0
0 0-27
0--49 0-21
943-1106 1225-1402
1570-1576 1329-1522
0 0
0-5 0--48
0-25 0-1
1265-1298 1187-1257
0 0
Kurchatovskii Institute. Translated from Atomnaya l~nergiya, Vol. 85, No. 6, pp. 481-482, December, 1998. Original article submitted November 25, 1998. 1063-4258/98/8506-0919520.00 o1999 Kluwer Academic/Plenum Publishers
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TABLE 2. Mean (over Power Plant) Neutron Leakage Atomic powerplant Chernobyl lgnalinsk Kursk Leningrad Smolensk, unit 1-2 3
Leakage, % total
I axial
! radial
2.06 2.04 2.27 2.10
0.88 0.94 0.93 0.92
1.17 1.10 1.34 1.18
2.28 2.43
0.94 0.95
1.33 1.48
Note that the basic differences in leakage between these groups of power stations is mainly determined by the radial leakage (Table 2). Detailed analysis is required to explain this finding, so that recommendations can be made for reducing the leakage at the Kursk and Smolensk plants to the level of the other plants. That such research is worthwhile is clear from the possibility of improving the fuel-rod consumption by up to 10 per year for each unit.
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