ML20034C958
| ML20034C958 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 05/23/1990 |
| From: | Tucker H DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20034C959 | List: |
| References | |
| IEB-89-002, IEB-89-2, NUDOCS 9006040183 | |
| Download: ML20034C958 (3) | |
Text
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(?N1373 4531 DUKE POWER 1
May 23, 1990 l!. S. Nuc1 car Regulatory Commission ATTN:
Document Control Desk Washington, D.C.
20555
Subject:
Duke Power Company Catawba Nuclear Station Docket Nos. 50-413, 50-414 Response to NRC Bulletin 89-02
" Stress Corrosion Cracking of liigh-llardness Type 410 Stainless Steel Internal Preload Bolting In Anchor Darling Model S350W Swing Check Valves or Valves of Similar Design" Pursuant to Item 3 of t.he Reporting Requirements of NRC Bulletin 89-02, I am providing the results of our investigation into this bulletin at Catawba Nuclear Station.
Catawha Nuclear Station has no Anchor Dalring Model S350W swing check valves installed or in our varchouse stock, llowever, there is one application that uses a design similar to the Anchor Darling Model S350W. This valve
-lNB-800, is located in the Boron Recycle System (NB) on a branch line just off of the Unit I and U.it 2 common header drain to the Boron Recycle llold-up Tank. This 4 inen valve is manufactured by Atwood & Morrill.
We have determined that we cannot inspect this valve during the 1990 refueling outages and do not anticipato an opportunity to inspect this valve in the future.
Swing check valve INB-800 is not capable of being isolated for disassembly unless both Units 1 and 2 are shutdown and defueled. This valve is located on a 4 inch line that ties into a common relief valve discharge header for the following systems:
Safety Injection (NI)
Containment Spray (NS)
Chemical and Volume Control (NV)
Residual llent Removal (ND)
Since the discharge header is common to both trains of both units, it could not be isolated or taken out of service without rendering the above systems 9006040183 900523 PDR ADOCK 05000413 Q
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U. S. Nuclesr R:gulatory Commission Page 2 May 23, 1990 inoperable.
(See Attachment).
Even with one or both units shutdown, the ND system must still remain operable and this would not be possible with INB-800 out of service. Other options considered in isolating this valve from the header included freeze scaling but it was not feasible due to the lack of sufficient space between the valve and the header. Duke has determined that further steps to gain access to this valve will involve excessive costs without a commensurate increase in the level of quality and safety.
Valve 1NB-800 is necessary to prevent highly radioactive effluent from the NB, ND, NI, NS and NV systems from backflowing into the Reactor Make-up Water Storage Tank and the Boric Acid Tank through the tank overflow lines.
This valve is normally closed and serves as a boundary valve between ASME Section III Code and non-nuclear safety related radioactive fluid piping.
It is not considered active or subject to leak rate testing per ASME Section XI.
Also, an additional backflow check valve is located upstream of INB-800 to provide redundant backflow protection for each Tank. The disc mounting bracket capscrews in question are preloaded to less than 35% of yield and, therefore, somewhat less susceptible to stress corrosion cracking than highly preloaded fasteners.
In addition, the failure mechanism described in the bulletin has historically not been a problem for Atwood & Morrill supplied valves.
Duke Power will review the findings from this Bulletin to determine if other utilities have experienced Stress corrosion cracking with internal 410SS fasteners used in similar Atwood & Morrill swing check valves.
If a problem is indicated, we will explore other options to inspect this valve. No further action is planned at this time.
Sincerely, C S?lc k A
/
Hal B. Tucker JSW/374/lcs xc Mr. S. D. Ebneter Regional Administrator, RII U. S. Nuclear Regulatory Commission 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. W. T. Orders NRC Resident Inspector Catawba Nuclear Station I
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