Izvestiya vuzov. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Potential of the VVER reactor spectral regulation with regard for fuel burn-up

7/09/2020 2020 - #02 Physics and technology of nuclear reactors

Tikhomirov G.V.

DOI: https://doi.org/10.26583/npe.2020.2.03

UDC: 621.039.536

Neutron spectrum control in a nuclear reactor makes it possible to monitor excessive reactivity through the absorption of excess neutrons in the absorber or by changing the uranium-water ratio. The paper deals with investigating the potential of the VVER reactor neutron spectrum control with the use of displacers. Zirconium rods of different diameters (Zr rods) were used as the displacers. The Zr rods were positioned between fuel rods. Introducing the Zr rods between the fuel rods and increasing their diameter leads to a decrease in the amount of water inside of the reactor and to a reduction in the multiplication factor. Excessive reactivity is made up for in current VVER reactors through the dissolution of boric acid in water. The results of comparing the potential efficiency of displacer utilization against the use of boric regulation are presented. The burn-up calculations have shown that adding Zr rods to the VVER-1000 geometry reduces the U-235 burning rate and enhances the Pu-239 production. The concentration of plutonium isotopes increases with the Zr rod diameter increase. Important safety parameters involved in the change of the moderator-fuel ratio are density and Doppler reactivity coefficients. These coefficients were therefore calculated with the obtained results demonstrating the potential safety of using displacers in VVER reactors instead of boric regulation. This has proved that the use of Zr rods as the neutron spectrum regulator makes it possible to maintain the neutron economy and to monitor excessive reactivity inside of VVERs.


  1. Iqbal Hosan M., Soner M.A.M., Khorshed Ahmad Kabir, Salam M.A., Fazlul Huq Md. Study on neutronic safety parameters of BAEC TRIGA research reactor. Annals of Nuclear Energy. 2015, v. 80, pp. 447-450. DOI: https://doi.org/10.1016/j.anucene.2015.02.031 .
  2. Atkinson S., Litskevich D., Merk B. Small modular high temperature reactor optimisation part 2: Reactivity control for prismatic core high temperature small modular reactor, including fixed burnable poisons, spectrum hardening and control rods. Progress in Nuclear Energy. 2019, v. 111, pp. 233-242. DOI: https://doi.org/10.1016/j.pnucene.2018.11.001 .
  3. Campolina D., Faria E.F., Santos A.A.C.,Vasconcelos V., Franco M.P.V., Dias M.S., Mattos J.R.L. Parametric study of enriched gadolinium in burnable neutron poison fuel rods for Angra-2. Annals of Nuclear Energy. 2018, v. 118, pp. 375-380. DOI: https://doi.org/ 10.1016/j.anucene.2018.04.025 .
  4. Chan P.K., Paquette S., Bonin H.W., French C., Pant A. Neutron absorbers in candu natural uranium fuel bundles to improve operating margins. International Conference on Nuclear Engineering, Proceedings, ICONE2115919. American Society of Mechanical Engineers (ASME). 2013. v. 1. DOI: https://doi.org/10.1115/ICONE21-15919 .
  5. Galahom A.A. Investigation of different burnable absorbers effects on the neutronic characteristics of PWR assembly. Annals of Nuclear Energy. 2016, v. 94, pp. 22-31. DOI: https://doi.org/10.1016/j.anucene.2016.02.025 .
  6. Tran H.N., Hoang H.T.P., Liem P.H. Feasibility of using Gd2O3 particles in VVER-1000 fuel assembly for controlling excess reactivity. Energy Procedia. 2017, v. 131, pp. 29-36. DOI: https://doi.org/10.1016/j.egypro.2017.09.442 .
  7. Safarzadeh O., Saadatian-Derakhshandeh F., Shirani A.S. Calculation of reactivity coefficients with burn-up changes for VVER-1000 reactor. Progress in Nuclear Energy. 2015, v. 81, pp. 217-227. DOI: https://doi.org/10.1016/j.pnucene.2015.02.006 .
  8. Fadaei A.H. Investigation of burnable poisons effects in reactor core design. Annals of Nuclear Energy. 2011, v. 38, pp. 2238-2246. DOI: https://doi.org/10.1016/ j.anucene.2011.06.005 .
  9. Frybortova L. VVER-1000 fuel cycles analysis with different burnable absorbers. Nuclear Engineering and Design. 2019, v. 35, pp. 167-174. DOI: https://doi.org/10.1016/ j.nucengdes.2019.05.026 .
  10. Taheranpour N., Talaei A. Development of practical method using a Monte Carlo code for evaluation of optimum fuel pitch in a typical VVER-1000 core. Annals of Nuclear Energy. 2013, v. 54, pp. 129-133. DOI: https://doi.org/10.1016/j.anucene.2012.10.029 .
  11. Banerjee S., Banerjee M.K. Nuclear Applications: Zirconium Alloys. Materials Science and Materials Engineering (Reference Module). 2016, pp. 6287-6299. DOI: https://doi.org/ 10.1016/j.anucene.2012.10.029 .
  12. Rench iukova б V., Macak J., Sajdl P., Novotny R., Krausova A., Corrosion of zirconium alloys demonstrated by using impedance spectroscopy. Journal of Nuclear Materials. 2018, v. 510, pp. 312-321. DOI: https://doi.org/10.1016/j.jnucmat.2018.08.005 .
  13. Chibinyaev A. V., Alekseev P.N., Teplov P.S. Estimation of the effect of neutron spectrum regulation on VVЙR-1000 fuel burnup. Atomic Energy. 2006, v. 101, pp. 680-683. DOI: https:/ /doi.org/10.1007/s10512-006-0151-z .
  14. Thilagam L., Sunil Sunny C., Jagannathan V., Subbaiah K.V. A VVER-1000 LEU and MOX assembly computational benchmark analysis using the lattice burnup code EXCEL. Annals of Nuclear Energy. 2009, v. 36, pp. 505-519. DOI: https://doi.org/10.1016/j.anucene.2008.12.015.
  15. Leppдnen J., Pusa M., Viitanen T., Valtavirta V., Kaltiaisenaho T. The Serpent Monte Carlo code: Status, development and applications in 2013. Annals of Nuclear Energy. 2015, v. 82, pp. 142-150. DOI: https://doi.org/10.1016/j.anucene.2014.08.024 .
  16. Hussain A., Xinrong C. Core optimization simulation for a pressurized water reactor. Information Technology Journal. 2009, v. 8, pp. 220-225. DOI: https://doi.org/10.3923/ itj.2009.220.225 .
  17. Lewis E.E. Fundamentals of Nuclear Reactor Physics. Elsevier Inc., 2008. 293 p. DOI: https://doi.org/10.1016/B978-0-12-370631-7.00001-2 .
  18. Stacey W.M. Nuclear Reactor Physics: Second Edition. Wiley-VCH, 2007. 706 p. DOI: https://doi.org/10.1002/9783527611041 .
  19. Faghihi F., Roosta F., Ghaemi S., Bagheri S. Core designing of the newly proposed (U+Gd)O2 FAs in the VVERs core and comparison with current UO2FAs. Alexandria Engineering Journal. 2019, v. 58, pp. 647-658. DOI: https://doi.org/10.1016/j.aej.2019.03.010 .
  20. Vahman N., Akbari-Jeyhouni R., Rezaei Ochbelagh D., Amrollahi R. An assessment of a VVER-1000 core during Turbo-Generator load reduction test using RELAP5/MOD3.2 and WIMSD-5B/PARCSv2.7. Progress in Nuclear Energy. 2016, v. 93, pp. 155-164. DOI: https://doi.org/10.1016/j.pnucene.2016.08.005 .

VVER reactivity reactivity coefficients boric regulation spectral regulation water displacers excessive reactivity