Issue With Determining the Limiting Point for a Nozzle for Pressure-Temperature Limits

One of the issues address in Regulatory Issue Summary (RIS) 2014-11, “Information on Licensing Applications for Fracture Toughness Requirements for Ferritic Reactor Coolant Pressure Boundary Components,” dated October 14, 2014, is that P-T limit submittals must address more than just materials with the highest reference temperature. In particular, structural discontinuities such as nozzles must also be addressed. The following pictorially explains the issue with nozzles.

The limiting point on a nozzle for P-T Curves has three competing factors:

1. Material

2. Fluence

3. Stress

The following illustrations depict the above factors (PWR inlet nozzle shown).

ANSWER: The answer is plant specific.

So, do your P-T curves adequately encompass all of your RPV nozzles? If you’re not sure, or if you have any questions, give us a call.

 

Footnotes:

(a) E.N. Jones, and B.P. Richardson, “Evaluation of DPA Profiles in Westinghouse 3-Loop and 4-Loop PWR Inlet and Outlet Nozzle Forgings using the RAMA Fluence Methodology,” presentation at the Materials Reliability Program Technical Advisory Committee Joint Meeting, November 13, 2012 (Slide 25).

(b) S. Yin, B.R. Bass, and G.L. Stevens, “Stress and Fracture Mechanics Analyses of Boiling Water Reactor and Pressurized Water Reactor Pressure Vessel Nozzles – Revision 1,” Oak Ridge National Laboratory Report No. ORNL/TM-2010/246, June 2012, ADAMS Accession No. ML12181A162 (Figure 53).

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