Swelling of guide tubes for safety rods in nonuniform fields of temperature and irradiation

4/04/2015 2015 - #01 Nuclear materials

Porollo S.I. Konobeev Yu.V. Garner F.A.

https://doi.org/10.26583/npe.2015.1.07

The purpose of the present work is to investigate shape changes and void swelling in safety rod guide tubes of the reactors BN-350 and BOR 60 after operation for the scheduled life time. Post-irradiation measurements of diameters of the reactor BN-350 temperature compensator were carried out for two mutually perpendicular positions after 50-100 mm along the core height with accuracy of 0.1 mm. Sizes of the reactor BOR-60 safety tube were measured for various cross sections along the core height at edges and face middles. The swelling of the tube material was measured by an Archimedes technique.

As a result of examination it was established, that neutron irradiation of the guide tube of the temperature compensator rod in BN-350 reactor core to the maximum dose of 65 dpa has led to its significant curvature (the maximal bending deflection is equal to 15 mm) and to diameter changes. Near the core center the tube diameter has increased in one of the directions to 89 mm from the initial value of 84 mm. In the perpendicular direction the tube diameter has decreased up to 82 mm, i.e. below initial value.

The operation of the safety rod guide tube in the BOR-60 reactor core to the maximum dose of 120 dpa has led to a significant increase of the hexagonal tube size between opposite edges and to a reduction of the flat-to-flat size at the tube face middle.

The change of safety rod guide tube sizes occurs due to a non-uniform swelling of the material (austenitic stainless steels EP-150 and 18Cr-9Ni) along tube wall height, perimeter and thickness. The swelling gradient leads to occurrence of significant internal stresses, under action of which a further deformation of the guide tube occurs in the form of initial size reduction due to irradiation creep. The high level of residual stresses in a combination with a complete brittleness of the tube material can lead to the tube failure even in the absence of any external loadings.

References

1. Cawthorne C., Fulton E.J. Voids in Irradiated Stainless Steel. Nature, 1967, v. 216, no. 11, pp. 575-576.
2. Norris D.I.R. Voids in Irradiated Metals (Part I). Radiation Effects, 1972, v. 14, pp. 1-37.
3. Norris D.I.R. Voids in Irradiated Metals (Part II). Radiation Effects, 1972, v. 15, pp. 1-22.
4. Bykov V.N., Vahtin A.G., Dmitriev V.D., Konobeev Yu.V., Kostromin L.G., Rreutov V.F. The investigation of void swelling in structural steels of the BR-10 reactor carbide core. Atomnaya Energiya. 1973, v. 34, iss. 4, pp. 247-250 (in Russian).
5. Lihachyov Yu.I., Proshkin A.A., Scherbakova Zh.N. Trudy Fiziko/energeticheskogo instituta, [Proceedings of the Institute for Physics and Power Engineering]. Moscow, Atomizdat Publ., 1974. 358 p. (in Russian).
6. Foster J., Boltax A. Observation of swelling-irradiation creep interaction at low values of swelling with CW 316 SS. J. Nucl. Mater. 1991, v. 183, pp. 115-123.
7. Flinn J.E., MсVay G.L., Walters L.C. In-reactor deformation of solution annealed type 304L stainless steel. J. Nucl. Mater. 1977, v. 65, pp. 210-223.
8. Waltar Alan E., Reynolds Albert B. Fast Breeder Reactors. Pergamon Press, 1981.
9. Beskorovajnyj N.M., Kalin B.A., Platonov P.A., Chernov I.I. Konstruktsionnye materialy yadernyh reaktorov [Structural materials for nuclear reactors]. Moscow, Energoatomizdat Publ., 1995. 704 p. (in Russian).
10. GOST 5632-72. P.17 (in Russian).
11. Krasnosyolov V.A., Kosenkov V.M., Loboda E.M. Materials science investigation of a compensating rod guide tube irradiated to the neutron fluence of 1.6Ч1023 n/cm2 (Е>0.1 МeV) in the BOR-60 reactor. Atomnaya Energiya, 1978, v. 44, iss. 3, pp. 228-231 (in Russian).
12. Golovanov V.N., Povstyanko A.V., Neustroev V.S. Materials science investigation of the BOR-60 reactor safety guide tube. Atomnaya Energiya, 1985, v. 59, iss. 4, pp. 289-290 (in Russian).
13. Scherbak V.I., Kostromin L.G., Dmitriev V.D. The influence of temperature drop across the safety guide tube wall on the void swelling of 18 Cr-9 Ni steel. Atomnaya Energiya, 1985, v. 47, iss. 5, pp. 336-337 (in Russian).

fast reactor swelling irradiation creep guide tubes temperature gradient damage dose

Link for citing the article: Porollo S.I., Konobeev Yu.V., Garner F.A. Swelling of guide tubes for safety rods in nonuniform fields of temperature and irradiation. Izvestiya vuzov. Yadernaya Energetika. 2015, no. 1, pp. 66-75; DOI: https://doi.org/10.26583/npe.2015.1.07 (in Russian).