VVER nuclear fuel burnup with different absorbers

Abstract

A computational study is performed of the fuel burnup in VVER-1000 using different absorbers in open and closed fuel cycles. It is shown that mixtures of plutonium isotopes (energy and others) can give the same effect as gadolinium, which is currently used. Fuel burnup increases. When neptunium, americium, and curium isotopes are used as a consumable absorber in a closed fuel cycle, the accompanying effect is elimination of long-lived α-emitting radionuclides which have accumulated in long-term repositories.The main sources of energy for nuclear power plants which are currently operating or under construction are water moderated and cooled light-water reactors. Such facilities will be used in the future in the construction of nuclear power plants in different countries irrespective of the specific provisions of the national plans for the development of nuclear power. This article presents the results of comparative computational studies of fuel burnup in open and closed nuclear fuel cycles. The calculations were performed using the standard parameters of VVER-1000.The enrichment of uranium used as fuel is the main, though not the only, indicator of the cost-effectiveness of nuclear power plants with VVER-1000. The consumption of natural uranium, the number of units of separation work, and probably most importantly the fuel burnup, which determines the operating expenses and the cost of fabricating new fuel elements depend on the enrichment.The main objective of scientific-technical developments concerning the fuel cycle of power reactors is to increase the fuel burnup. Ordinarily, it is achieved by increasing the initial enrichment and using consumable absorbers. As enrichment increases, the consumable absorber decreases the multiplication properties of the reactor core at the run start to a value which can be compensated by the safety and control system. Gd 2 O 3 is added to VVER-1000 fuel as the consumable absorber. The isotopic composition of natural gadolinium and the absorption cross section of thermal neutrons at 0.0253 eV of separate isotopes are presented in Table 1. In the present work, the MCNP program [1] and the system of programs SCALE [2] were used to calculate fuel burnup. Figure 1 shows the dependence of the multiplication coefficient K cell of a cell as a function of the burnup W. A cell is taken to mean a standard fuel assembly containing 316 fuel elements, 12 channels for control rods, and a central tube.The computed curves illustrate the change in K cell during a VVER-1000 run: curve 1 -fuel containing only UO 2 with 5% enrichment is loaded into the core; curve 2 -fuel containing UO 2 with 5% enrichment is loaded into the core; gadolinium in the form Gd 2 O 3 (3.7% of the uranium mass) is added as the consumable absorber to 12 fuel elements of each fuel assembly.

Precise calculation of neutron-capture reactions contribution in energy release for different types of VVER-1000 fuel assemblies

“…Dimensions of fuel rods are the same as for 13ZS and 30ZSV models (Figure 3, 4). Characteristics of materials are in Table 5 [10,11]. Calculated Ʉeff is 0.999 for all the models.…”

Use of erbium as a burnable absorber for the VVER reactor core life extension

“…В первую очередь рассматривалась задача об оценке влияния весовой доли эрбия в твэлах на выгорание выгружаемого топлива [9]. Весовое содержание двуокиси эрбия в твэлах варьировалось в интервале от 0.3 до 1.1% с интервалом 0.2% весовых.…”

Decay heat power of spent nuclear fuel of power reactors with high burnup at long-term storage

“…Results of calculations of the main actinide masses from the annual discharge of the VVER-1000 [9,10] reactor for the burnup of 40-70 MW·d/kg are presented in Table 1 and are illustrated in the Figure 1 for more wide limits of burnup. 3 Decay heat power of fission products and actinides from single unloading of spent fuel of VVER-1000 reactor in longterm storage Calculated decay heat power of main fission products and actinides from 1 ton of spent fuel of VVER-1000 reactor with burnup of 40 and 70 MWÂd/kg at long-term storage during the time T is presented in Tables 2 and 3.…”