Steam generator tube integrity program: Phase II, Final report

Abstract

The Steam Generator Tube Integrity Program (SGT!P) was a three phase program conducted for the u 1 S. Nuclear Regulatory Commission (NRC) by Pacific Northwest Laboratory (PNL).1a) The first phase involved burst and collapse testing of typical steam generator tubing with machined defects. The second phase of the SGTIP continued the integrity testing work of Phase I, but tube specimens were degraded by chemical means rather than machining methods. The third phase of the program used a removed-from-service steam generator as a test bed for investigating the reliability and effectiveness of in-service nondestructive eddy-current inspection methods and as a source of service degraded tubes for validating the Phase 1 and Phase II data on tube integrity. This report describes the results of Phase II of the SGTIP. The object of this effort included burst and collapse testing of chemically defected pressurized water reactor (PWR) steam generator tubing to validate empirical equations of remaining tube integrity developed during Phase I. Three types of defect geometries were investigated; stress corrosion cracking (SCC), uniform thinning and elliptical wastage. In addition, a review of the publicly available leak rate data for steam generator tubes with axial and circumferential sec and a comparison with an analytical leak rate model is presented. Lastly, nondestructive eddy-current (EC) measurements of defect severity are reported. laboratory EC measurements to determine accuracy of defect depth sizing using conventional and alternate standards is described. To supplement the laboratory EC data and obtain an estimate of EC capability to detect and size SCC, a mini-round robin test utilizing several firms that routinely perform in~service inspections was conducted.

Risk assessment of severe accident-induced steam generator tube rupture

“…I n conjunction w i t h an NRC-sponsored steam generator integrity program, Pacific Northwest National Laboratories (PNNL) conducted a series of tests (Kurtz, 1990) on tubes containing part-through-wall axial cracks. From these tests, PNNL developed an empirical formula for the failure pressure of a tube containing a part-through axial crack.…”

“…(Kurtz, 1990) using the various models for m,. These errors are expressed i n terms of the root-mean-squared (RMS) errors for the entire test series and i n terms of the RMS errors associated w i t h a range of crack depths.…”

“…Although fairly extensive tensile property data are available for tubing a t room temperature (Kurtz, 1990). only limited data are currently available for higher temperatures.…”

“…multiplied Equation (20a) by a factor of 0.9. This is the same factor by which the sum of the yield and ultimate tensile strengths of Alloy 600 bars a t room temperature (Rempe, 1993) has t o be multiplied t o obtain the sum of the yield and ultimate tensile strengths for Alloy 600 tubes a t room temperature (Kurtz, 1990;Chavez, 1996).…”

Steam generator tube integrity program. Semiannual report, August 1995--March 1996

“…The first set included four axial cuts 0. 25 The 20 SG tube samples were also inspected by M. Brook at ABB AMDATA with an ultrasonic probe that propagated Lamb waves in the tube wall, which are unaffected by a roll transition. These waves propagate in a free tube wall and are capable of detecting inner or outer-surface circumferential cracks.…”