Peculiarities of Neutronics Characteristics of Integral Reactor WWER of Small Capacity

Abstract

In the present paper are analyzed the neutronic characteristics of the stationary fuel loading of the core of integral reactor WWER with a small power 600 MW (th.) and about 200 MW (el.) calculated with Russian code BIPR-7. The core and the FAs, and also the technological parameters are basically analogous to serial reactor WWER-1000; however, there are essential differences in comparison with the WWER-1000:

 - in the core are placed 85 FAs (163 in WWER-1000) with an active length 250 cm (355 cm in WWER-1000);

- it is used the reactor campaign of 24 months length and the fuel campaign of 48 months (in WWER -1000 is used 12-18 months the reactor campaign and 36-48 months the fuel campaign);

- for reduction in the neutron leakage on the core periphery are placed burnt out FAs with the smallest multiplication properties, and also FAs have axial blankets with the smaller enrichment (in WWER-1000 they are used to a lesser degree or they are not used);

 - there are 18 Guiding Tubes placed in FAs for reactor control and EP provision for the arrangement in them the Black and Grey CRs CPS (in WWER-1000 they are used only Black CRs CPS for EP provision);

- for compensating of the reactivity margin for fuel burn-up and for subcriticality provision of reactor in shut-down conditions are widely used the IFBA in FAs – 18-30 FRs with 8% of natural Gd (tvegs), and also Grey and Black CRs CPS and is not used the dissolved boron in the coolant (in WWER-1000 in essence it is used dissolved boron in the coolant and to a lesser degree the tvegs);

- under the conditions for boron-free control, for guaranteeing the minimum power peaking factors in the core it is fitted the optimum axial enrichment profiling of FAs and axial profiling of concentration of BA in tvegs, and also the axial profiling of concentration of absorber in CRs CPS (in WWER-1000 it is not used).

The neutronic characteristics were investigated in the process of burning out of fuel in the base operating mode at the nominal power for variant of boron-free control. They are compared with analogous characteristics for usual variant of boron control. The mode of the daily manoeuvring in a wide range of power change 100-30-100% of nominal power is also analyzed for variant of boron-free control and with use of additional regulation by various primary coolant temperatures (modes "P2=const", "tin=const", "tav=const"). The positive results were obtained, which make it possible to make a conclusion about the relatively simple feasibility of WWER technology in the neutronic aspect in the integral smallpower reactor.