Izvestia Vysshikh Uchebnykh Zawedeniy. Yadernaya Energetika

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

Analysis of a severe beyond design basis accident for the EGP-6 reactor facility at Bilibino NPP. Release source term formation

3/23/2018 2018 - #01 Global safety, reliability and diagnostics of nuclear power installations

Parafilo L.M. Mukhamadeyev R.I. Baranayev Yu.D. Suvorov A.P.

DOI: https://doi.org/10.26583/npe.2018.1.10

UDC: 621.039.586

An analysis has been performed for the dynamic phase progression in a severe beyond design basis accident caused by uncontrolled insertion of positive reactivity into the EGP-6 reactor in conditions of the emergency protection system failure. The initial event leads to the reactor power growing rapidly to 450% of the rated value, involving the fuel temperature growth and the growth in the coolant temperature and pressure. These factors result in the coolant boiling in some of the FAs, leading to a departure from nuclear boiling, the fuel damage in these SFAs and the escape of the steam-water fluid into the reactor stack. The stack pressure growth leads to the reactor shroud damage, the escape of the steam-water fluid into the space above the core and the subsequent steam-water fluid transport (into the reactor hall and the above-core space ventilation system and, further, into the environment). The dynamic processes were calculated using the RELAP5/Mod3.2 code. The stages of the fuel damage process were considered, and the dynamics in the number of and the extent of damage to fuel elements in the FAs was estimated. The estimated fission product release from the failed FAs was considered based on experimental data acquired at SCC IPPE for the Bilibino NPP FAs (tube-type steel-clad fuel elements, fuel composition: uranium dioxide grit in a magnesium matrix) for the severe beyond design basis accident conditions. The transport of fission products with water and steam was estimated based on experimental data for the fission product graphite stack transmission in conditions of a severe accident, also obtained at SCC IPPE. The emergency release into the atmosphere was estimated with regard for the fission product release dynamics and the use of two approaches to the release path formation (conservative or the most probable one). Good self-protection properties of the EGP-6 facility in conditions of a severe beyond design basis accident were noted.

References

  1. Bilibino NPP. Unit 4. In-depth Safety Analysis Report. JSC Concern Rosenergoatom, JSC SSC IPPE, JSC Atomenergoproekt, JSC Izhorskiye zavody. Moscow, Rosenergoatom, 2016, 4971 p. (in Russian).
  2. General Provisions for Ensuring NPP Safety. NP-001-2015. Moscow. Rostechnadzor Publ., 2015 (in Russian).
  3. Recommendations for the Content of the In-depth Safety Analysis Report for Effective Nuclear Power Units. RB-001-05. Moscow, Rostekhnadzor Publ., 2005 (in Russian).
  4. Deterministic Safety Analysis for Nuclear Power Plants. IAEA SAFETY STANDARDS SERIES No. SSG-2, STI/PUB/1428, IAEA, Vienna, 2009, 84 p.
  5. Fletcher C.D., Schultz R.R.RELAP5/MOD3 Code Manual. NUREG/CR-5535, INEL-950174, v. 2, 293 p.
  6. RELAP5/MOD3.2 Certification Passport as Applied to Calculations for the EGP-6 Reactor. No. 317, dated 9.10.2012. Moscow, Rostekhnadzor Publ.. 2012, 6 p. (in Russian).
  7. Samoilov A.G., Kashtanov A.I., Volkova V.S. Dispersion Fuel Elements. Vol. 1. Materials and Technologies. Moscow. Energoatomizdat Publ., 1982, 224 p. (in Russian).
  8. Samoilov A.G., Kashtanov A.I., Volkova V.S. Dispersion Fuel Elements. Vol. 2. Design and Serviceability. Moscow. Energoatomizdat Publ., 1982, 256 p. (in Russian).
  9. Samoilov A.G., Volkov V.S., Solonin M.I. Fuel Elements of Nuclear Reactors. Moscow. Energoatomizdat Publ., 1996, 400 p. (in Russian).
  10. Review of Fuel Failures in Water Cooled Reactors, Technical Reports Series No. 388, STI/ DOC/010/388; (ISBN: 92-0-102298-0), IAEA, Vienna (1998), 167 p.
  11. Fuel Failure in Water Reactors: Causes and Mitigation (Proceedings of Technical Meeting Bratislava, 2002), IAEA-TECDOC-1345, IAEA, Vienna (2003), 165 p.
  12. Structural Behaviour of Fuel Assemblies for Water Cooled Reactors (Proc. Tech. Mtg. Cadarache, France, 2004), IAEA-TECDOC-1454, IAEA, Vienna (2005), 324 p.
  13. Review of fuel failures in water cooled reactors. NF-T-2.1, STI/PUB/1445; (ISBN:978-92-0-102610-1), IAEA, 2010, 178 p.
  14. Nuclear Safety Regulations for Reactor Facilities of Nuclear Power Plants. NP-082-07. Moscow. Rostehnadzor Publ., 2007, 26 p. (in Russian).
  15. Baranaev Yu.D., Dolgov V.V., Moseev L.I., Viktorov A.N. Release of Fission Products from Dispersion Nuclear Fuel in Conditions of Accidents at Nuclear Icebreakers and Bilibino NPP / The 15th Mendeleyev Congress on General and Applied Chemistry. Obninsk Symposium. Abstracts of reports in 2 volumes, p. 58 (in Russian).
  16. Baranaev Yu.D., Dolgov V.V., Moseev L.I., Viktorov A.N. Experimental determination of fission product release from the Bilibino NPP reactor fuel in conditions simulating severe accidents. Atomic Energy, v. 74, iss. 5, 1993, pp. 416-421 (in Russian).
  17. Dolgov V.V., Ilyin Yu.V., Ryabov V.V. Results of the Bilibino NPP fuel element testing in conditions simulating an accident with complete coolant loss and a failure of all active cooldown channels. The 4th Interbranch Conference on Reactor Materials Science, 15-19 May 1995, Dimitrovgrad. Collection of Reports in 2 Volumes. Dimitrovgrad. NIIAR Publ., 1996. V. 1. Fuel and Fuel Elements of Power Reactors, pp. 165-177 (in Russian).
  18. Suvorov A.P., Baranaev Yu.D., Moseev L.I., Kozmenkov Ya. K. Experimental and Calculational Investigations of Fission Product Release from Fuel of Water Cooled Reactors on Initial Stage of Severe Accident. Report on TCM Design measures for prevention and mitigation of severe accident at advanced water cooled reactors, 21-25 October, Vienna, 1996. IAEA-TECDOC-1020, IAEA, Vienna, 1998, pp. 27-37.
  19. Croff A.G. ORIGEN-2: A Versatile Computer Code for Calculating the Nuclide Compositions and Characteristics of Nuclear Materials, Nuclear Technology. 1983, v. 62, pp. 335-352.
  20. Deen J.R., Woodruff W.L., Costescu C.I. WIMS-D/4 User Manual. Rev.0. Agronne National Laboratory and University of Illinois, ANL/RETR/TM-23, Argonne, 1995, 95 pp. Available at http://www.oecd-nea.org/tools/abstract/detail/nea-0329 (accessed Sep. 21 2017).
  21. Sharapov V.N. Neutronic basis of water-graphite reactors with tubular fuel elements. Dr. Sci. thesis in specialization 05.14.03. Obninsk. SCC RF-IPPE Publ., 1997, 75 p. (in Russian)

severe beyond design basis accident departure from nucleate boiling fuel damage dynamics fission product escape release