PSI - Issue 5

Hyung-Kyu Kim et al. / Procedia Structural Integrity 5 (2017) 63–68 Hyung-Kyu Kim/ Structural Integrity Procedia 00 (2017) 000 – 000

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and ovality are altered, a corresponding plot can be generated by using the methods explained in section 3.

Fig. 4. Reference thickness of a 9.5 mm diameter tube to avoid the buckling failure with the safety factor of 2.0 and 1% ovality.

5. Conclusions

It is found that the formula of the critical buckling pressure may be non-conservative owing the measurement uncertainties of the elastic modulus and the Poisson ratio as well as the tolerances of the tube thickness and radius. From the example case of a zirconium alloy tube of 5.1-16.5 mm in nominal outer diameter and 0.25-0.89 mm in nominal thickness, the critical buckling pressure can be reduced by more than 25% if the maximum tolerance of the thickness (0.08 mm) is incorporated. Besides the thickness uncertainty, the uncertainty of shape irregularity of a tube, i.e. the ovality is found more critical. Another example of a Type 304 stainless steel tube having 0.02 ≤ t / r ≤ 0.2 shows the critical buckling pressure can be reduced by 13-73% if 1% ovality is allowed. If the ovality increases, the reduction becomes much severer, further more than a linear manner. This implies that a quality control of the thickness and ovality is significantly crucial in the tube manufacturing to achieve a safe design against the buckling failure.

Acknowledgements

This work has been carried out under the Nuclear R&D Program supported by the Ministry of Science, ICT & Future Planning.

References

ASTM Standard B 811-02. 2007. Standard specification for wrought zirconium alloy seamless tubes for nuclear fuel cladding. ASTM Standard A 269-10. 2010. Standard specification for seamless and welded austenitic stainless tubing for general service. Timoshenko, S.P. and Gere, J.M., 1961. Theory of Elastic Stability, 2 nd Ed., McGraw Hill, New York, pp. 289-297. Huh, Y.-H. et al. 2010. Estimation of measurement uncertainty in evaluation of tensile properties, Transaction of KSME(A) 34, 73-78 (in Korean). Kim, H.-K. et al., 2009. A study on the structural integrity issues on a dual-cooled fuel rod, Top Fuel 2009. Paris, France, paper #2080. Matweb, 2017. www.matweb.com. Griffin, D.S., Inelastic buckling of long axially compressed curved plates. WAPD-TM-469, Bettis Atomic Power Laboratory, Pittsburgh, Pennsylvania, July 1965. Morgan, R., Report on external collapsing pressure for ELK River reactor fuel element tubing. ACNP 64-509, Allis-Chalmers Manufacturing Company, Washington D.C., Jan. 1964.