Eccentricity Analysis of the Fuel Assembly Spring Cartrige Force

Fuel assembly bow of a nuclear reactor is one of the major problems of nuclear power engineering and can result in an emergency at a nuclear power plant. However, the causes of fuel assembly bow, currently not fully understood. This study identified a possible cause of fuel assembly bow as its eccentric compression due to relaxation processes occurring in the spring cartridge and causing eccentricity of the spring cartridge force. A mathematical model is worked up for determining the parameters of eccentric assembly compression: the force eccentricity compressing the assembly, and the bending moment. The study showed that the force eccentricity compressing the assembly, and the bending moment are significant, and their impact cannot be ignored when analyzing the fuel assembly bow.

References

[1] Review of fuel failures in water cooled reactors. Vienna, International Atomic Energy Agency, 2010, 191 p.

[2] Boyle, J.T., Spence, J. Stress analysis for creep. London, Butterworth, 1983. (Russ.ed.: Boil Dzh., Spens Dzh. Analiz napriazhenii v konstruktsiiakh pri polzuchesti. Moscow, Mir publ., 1986. 360 p.).

[3] Danilov V.L., Zarubin S.V., Semishkin V.P. Raschetno-teoreticheskii analiz napriazhenno-deformirovannogo sostoianiia teplovydeliaiushchei sborki VVER-1000 [Computational and theoretical analysis of the stress-strain state of the fuel assemblies of VVER-1000] . Mater ialy I I Vseros siiskoi nauchno- tekhnicheskoi konferen- t s i i «Obespechenie bezopasnosti AES s VVER» [Materials II All-Russian Conference «Safety Assurance of NPP with WWER»]. Podol’sk, 2001.

[4] Kiselevskii V.N. Izmenenie mekhanicheskikh svoistv stalei i splavov pri radiatsionnom obluchenii [Changes in the mechanical properties of steels and alloys in radiation exposure]. Kiev, Naukova dumka publ., 1977. 101 p.

[5] GusevM.P., Danilov V.L. Relaksatsiia pruzhin golovnoi chaste teplovydeliaiushchei sborki [The relaxation of the head of the springs of the fuel assembly]. Vestnik MGTU im. N.E. Baumana. Spetsial’nyi vypusk Sovremennye problemy prikladnoi mekhaniki dinamiki i prochnosti mashin [Herald MSTU named after N.E. Bauman. Special Issue Recent developments in applied mechanics, dynamics and strength machines]. 2012, no. 6, pp. 139–148.

[6] Bogomolova O.A. , Enin A.A. , Rozhkov V.V. Eksperimental’nye issledovaniia mekhanicheskikh kharakteristik elementov, uzlov i maketov TVS s zhestkim karkasom v obosnovanie termomekhanicheskoi stabil’nosti TVS v usloviiakh ekspluatatsii [The experimental study of the mechanical characteristics of the elements, components and layouts FA with a rigid frame to support the stability of FA in the thermomechanical conditions]. Materialy II Vserossiiskoi nauchno-tekhnicheskoi konferentsii «Obespechenie bezopasnosti AES s VVER» [Materials II All-Russian Conference «Safety Assurance of NPP with WWER»]. Podol’sk, 2001.

[7] Mahmood R., Channel bow in boiling water reactors — hot cell examination results and correlation to measured bow, 2007 Int. LWR Fuel Performance Mtg, San Francisco, CA, 2007.

[8] Bibilashvili Yu., Operation experience of WWER fuel, including analysis of abnormal condition, Proc. 2nd Int. Sem. on WWER Reactor Fuel Performance, Modelling and Experimental Status, Sandanski, 1997, BAS, INRNE, Sofia, 11.

[9] Jacobson S., Francillon, E. Incomplete control rod insertion due to fuel element bow, Nuclear Fuel and Control rod: Operating Experience, Design Evolution and Safety Aspects, Madrid, 1996.

[10] Anderson T. A decade of assembly bow management at Ringhals, Int.Mtg on LWR Fuel Performance, Orlando, FL, 2004.

[11] Bosselut D., Insertion and drop of control rod in assembly: simulation and parametric analysis, Structural Behaviour of Fuel Assemblies for Water Cooled Reactors, IAEA-TECDOC-1454, IAEA, Vienna, 2005.

[12] Chaplin D., EFG Fuel designs and experience in EDF reactors, TopFuel 2006, Salamanca, 2006.