IR 05000261/1988027
| ML14191B012 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 10/05/1988 |
| From: | Blake J, Kleinsorge W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML14191B011 | List: |
| References | |
| 50-261-88-27, NUDOCS 8810250024 | |
| Download: ML14191B012 (7) | |
Text
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- 0 UNITED STATES
NUCLEAR REGULATORY COMMISSION REGION il 101 MARIETTA ST., ATLANTA, GEORGIA 30323 Report No.: 50-261/88-27 Licensee: Carolina Power and Light Company P. 0. Box 1551 Raleigh, NC 27602 Docket No.:
50-261 License No.:
DPR-23 Facility Name: H. B. Robinson Inspection on cte :
ember 12-14, 1988 Inspect r: *--
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o ge, Date Signed Approv d by
J.. Bae, Section Chief D te Signed M e is and Processes Section E gin ering Branch D vision of Reactor Safety SUMMARY Scope:
This routine, announced inspection was conducted in the areas of biofouling of.containment cooler Results: In the areas inspected, no violations or deviations were identifie The licensee's past actions related to biofouling of the service water system were driven by economic concerns which appear to be penny-wise and pound foolis The licensee's actions after the identification of potential compromise of containment integrity have been well thought, comprehensive and conservativ This indicates that the licensee's management is approaching this technical issue from a safety standpoin O24 881011 PDR ADOCK 05000261 Q:
REPORT DETAILS 1. Persons Contacted Licensee Employees
- J. Cribb, Acting Director or Quality Assurance/Quality Control
- C. Dietz, Robinson Nuclear Project Department Manager
- W. Farmer, Engineer - Systems
- W. Flanagan, Technical Supported Design Engineering Manager
- E. Harris, Jr., Director Onsite Nuclear Safety
- M. Page, Engineering Supervisor Plant Systems
- D. Quick, Acting General Manager,
- D. Sayre, Acting Director of Regulatory Compliance Other licensee employees contacted during this inspection included engineers, mechanics, technicians, and administrative personne NRC Resident Inspector R. Latta, Resident Inspector
- Attended exit interview 2. Biofouling of Containment Coolers The original cooling coil assemblies consisted of continuous water tube cooling coils of 5/8" x 0.049" copper tubing (See Figure 1).
The first cooling coil assemblies lasted eight years, from plant startup in 1971 to June 197 The cooling coil assemblies were replaced with identical replacement cooling coil assemblies under Plant Modifications M470 and M47 The second set of cooling coil assemblies lasted four years from installation in June -
September 1979 to November 198 The licensee indicated that the both sets of cooling coil assemblies were replaced due to the effects of errosion/corrosion after multiple repair No metallurgical evaluation as made of the failed assemblies. The third sets of cooling coils were installed in November 1983 under Plant Modification M76 The third set of cooling coil assemblies differed from the first two as follows:
The third set is a stack of six cooling coils, six row, three pass configurations with removable cover water-box headers on both ends, with 5/8" x 0.028" alloy AL-6X tubes rolled into a type 316L stainless steel water box headers (see Figure 2).
The typical chemical analysis and mechanical properties for alloy AL-6X are shown on Figure During the refueling outage March - May 1987, two fuel cycles after installation of the third set of cooling coil assemblies HVH-2 and 4 were visually inspected "...From the outlet side with a light on the inlet side. The tubes were found to be shiny (internal surfaces with no heavy deposits."
NRC Report No. 50-261/88-12, Reported that microbiological induced corrosion (MIC) had been identified outside the envelope of the sleeves in the service water syste This condition was identified.as a potential compromise of containment integrit As a consequence of this, the licensee committed, in their July 22, 1988 letter, to repair or replace the service water piping in the containment building where the internal pressure is less than the containment pressure during a Design Basis Accident, during the 1988 Refueling Outage (now scheduled to start November 12, 1988).
To determine the extent of pipe replacement necessary the licensee performed SP-814 to obtain service water system flow. and pressure data under different plant conditions. The testing revealed flows and outlet pressures much lower than anticipated. The reevaluation of low flows and outlet pressures initiated an investigation of the cause. Upon removal of the water box covers in HVH coolers, the licensee noted the following on the water side of the cooling coil assemblies:
Approximately 10-25% of the tubes were plugged, 10-25% of the tubes were relatively clean, and the majority of the tubes were fouled to the point that there was a 20-50% reduction in tube ID. The fouling was distributed down the length of the tube The fouling appeared to be uniform in each cooler. The fouling appeared to be identical to the fouling that was found in the 1987 outage, in the service water system piping. After removing the fouling, bright shiny metal could be seen; the fouling was extremely easy to remov A sample of the fouling was submitted to the licensee's Harris E&E Center for analysis but, as of this writing, the analysis has not been complete After cleaning the water side-of the cooling coil assemblies the licensee inspected a sample of the tubes with a fiberscope and made the following observation Fiberscopic examination indicated that the tubes may have experienced extensive pitting and possibly branched crackin It was recommended to Nuclear Engineering Department personnel that eddy current testing be performed to either accept or reject the visual findings, and to characterize the tube A Hydro Test of the service water system at 67 psig, was performe This test was approximately 25 psig pressure over 40 psig maximum design basis accident pressure for the containment. The test pressure was maintained for four hours followed by a 100% walk down of the service water system and HVH coolers. A pin hole leak was found in a sleeve to pipe fillet weld outside the enveloped of the sleev A review of documents relating to the Alloy AL-6X cooling coil assemblies relative to biofouling revealed the following:
CP&L Memorandum from A. Moccari to T. Lewis dated October 5, 1983, referring to Alloy AL-6X stated in part:
No printed data on the biofouling resistance of this alloy is available in the open literatur From plant observation and the nature of the lake water, we do know that the possibility of sludge formation does exis How much and how fast the tubes foul, or sludge forms, or how often the deposits have to be removed is not know It is worthwhile to investigate the biofouling rate of this alloy to determine the necessary cleaning method and period."
Westinghouse Technical Manual - Reactor Containment Fan Cooler System dated September 1984 - Paragraph 24.4 states:
"2. Cooling Coil Wet and Dry Layup If the cooling water flow to the cooling coils is to be stopped for a prolonged period, such as during an extended core refueling or plant steam generator replacement, unrestrained growth of biological fouling can seriously degrade the thermal performance of the cooTing coil To minimize or eliminate the biological growth, one of the following three methods should be-followed:
o Drain the cooling coils and blow dry air through the tubes until all moisture is purge o Initially, take no special precautions and leave the coils filled with cooling wate Record for future action, however, that a tube-side cleaning procedure should be performed prior to putting the cooling coils back into servic o Wet layup is permitted if the cooling water is treated with a biocidal agent to prevent biological growth during the no-flow condition."
At this writing the licensee was in the process of developing the repair procedure for the pinhole leak; and engineering evaluations to support:
the operability of the service water containment coolers; the integrity of the containment coolers; and the integrity of the service water syste The licensee in retrospect questioned the adequacy of the 1987 inspector of the cooling coil assemblie In light of the warnings provided by the Westinghouse technical manual and the Moccari memorandum, combined with the biofouling of the cooling coil assemblies, the licensee also questioned the frequency and adequacy of inspections of the cooling coil assemblie The licensee indicated that they intend to replace as much of the service water pipe in containment with Alloy AL-6XN pipe (see Figure 3) as possible with the contraints of procurement, and availability of welders during the November 1988 refueling outag Based on this inspection it appears that the licensee's past actions related to service water system biofouling, were driven by economic concerns, which appear to be penny-wise and pound foolis The licensee's actions and plans after the identification of the potential compromise of containment integrity reported in 50-261/88-12 have been well thought out, comprehensive, and conservativ This indicates that the licensee's management is approaching this technical issue from a firm safety standpoin Within the areas examined no violations or deviations were-identifie. Action On Previous Inspection Findings (92701)(92702)
Actions of previous inspection findings were not examined during this inspectio. Exit Interview The inspection scope and results were summarized on September 14, 1988, with those persons indicated in paragraph 1. The inspectors described the areas inspected and discussed in detail the inspection results listed belo Proprietary information is not contained in this repor Dissenting comments were not received from the license FIGURE 1 FIGURE 2
Typical Analysis Element AL-6X AL-6XN C
0.025 0.02 Mn 1.50 0.50 P
0.025 0.025 S
0.010 0.002 Si 0.50 0.40 Cr 20.25 20.75 Ni 24.50 25.00 Mo 6.25 6.50 N
0.20 Cu 0.15 Mechanical Properties Yield Strengty.2% offset, PSI 40,000 55,000 Tensile Strength PSO 90,000 110,000 Elongation In 2" Percent
50 Reduction in Area Percent
65 Figure 3