05000390/FIN-2012005-03
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Finding | |
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| Title | Engineering Justification for Modifications to NON-CONFORMING Ice Baskets |
| Description | The inspectors reviewed outage WO 113393057 which specified the installation of new hardware on a total of six ice baskets that had been damaged, apparently due to ice condenser maintenance. The ice condenser is located within the primary containment and was designed, tested, qualified and fabricated by Westinghouse, the nuclear steam supply system original equipment manufacturer (OEM). The ice condenser contains a total of 1944 vertically supported, perforated 14 gauge sheet metal, ice baskets (12.1 inches in diameter and 48 feet tall) each weighing a maximum of 2200 pounds (ice column + basket). Each of the six damaged baskets (non-conforming components) had suffered plastic deformation (local compressive buckling) of support ligaments in the vicinity of the bottom three feet of the baskets. Instead of replacing the damaged portion of the baskets, as permitted by FSAR Section 6.7.4, licensee engineering had designed hardware to add to the damaged portions of the baskets. EDC E-50607, Revision A, specified the installation of vertical supports mechanically attached on the outside of the damaged area and EQV 60275, Revision A, specified the use of wire rope (steel cable) laced through the damaged area. According to the referenced calculation, WCG-1-1912, Qualification of the Optional Lower Ice Basket Support, the vertical supports were intended for compressive loading and the wire rope was intended for tensile loading. Per FSAR Table 6.7-2, during a deadweight load or deadweight and seismic loads the vertical load on the ice baskets is in compression. When subjected to a design basis accident (DBA) load in combination with a deadweight, or deadweight and earthquake load, the vertical load on all the ice baskets is in tension and the compressed ice basket would tend to elongate. Review of FSAR Section 6.7.4.3, Design Evaluation, Loading Conditions, part 2., Blowdown Loads, subpart E. Horizontal Ice Basket Forces, states that the tangential and radial forces acting on the ice baskets due to cross flow are assumed to act on the bottom, three feet of ice basket (one-half of the span between the top of the lower support structure and the attachment of the ice baskets to the first lattice frame). The inspectors did not find that the licensee-developed design changes adequately considered these dynamic tangential and radial loads on the damaged ice baskets. Their modifications only addressed either tensile or compressive forces on the ice baskets. Also the addition of the hardware appeared to be more appropriately governed by the requirements of a temporary alteration control form (TACF) per procedure NPGSPP- 09.5, Temporary Alterations, since information contained in the WO indicated the damaged baskets would have to be replaced during the next refueling outage. In addition, the 10CFR50.59 screening processes employed for the addition of hardware did not adequately consider the key elements that would be addressed for a TACF, since hardware was being added to safety-related components. The modifications may not be adequate for the damaged ice baskets to withstand all static and dynamic loads they were originally designed, tested, and qualified to be subjected to. Although there appears to have been some verbal contact between the licensee and the OEM engineering organization regarding the damaged ice baskets, there was no formal OEM review and acceptance of the licensee modifications as an acceptable alternative to ice basket replacement or repair per FSAR Section 6.7.4. Pending additional information from the licensee which can verify that there was adequate engineering justification for the use of an EDC and an EQV for hardware modifications to ice baskets, this item is identified as unresolved item (URI) 050000390/2012005-03, Engineering Justification for Modifications to Non-Conforming Ice Baskets. |
| Site: | Watts Bar  |
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| Report | IR 05000390/2012005 Section 1R18 |
| Date counted | Dec 31, 2012 (2012Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.18 |
| Inspectors (proximate) | S Shaeffer A Nielsen K Miller R Hamilton R Kellner R Monkd Faillae Patterson J Hamman K Miller M Speck R Baldwin R Lanyi R Monk S Shaeffer |
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Finding - Watts Bar - IR 05000390/2012005 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Watts Bar) @ 2012Q4
Self-Identified List (Watts Bar)
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