ML19247A852
| ML19247A852 | |
| Person / Time | |
|---|---|
| Site: | Catawba, Perkins, Cherokee  |
| Issue date: | 07/18/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Dail L DUKE POWER CO. |
| References | |
| NUDOCS 7908030005 | |
| Download: ML19247A852 (2) | |
Text
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8 s.gg g NUCLEAR RE U ATORY COMMISSION a
REGION 11
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p JUL 181979 In Reply Refer To:
RII:JP0 50-413, 50-414 50-488, 50-489 50-490, 50-491 50-492, 50-493 Duke Power Company Attn:
L. C. Dai1, Vice President Design Engineering P. O. Box 33189 Charlotte, North Carolina 282'42 Gentlemen:
The attached enclosure, Circ.ular 76-06, was inadvertently coitted in the July 17, 1979 issue of Information Notice 79-19.
Sincerely,
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wr f James P O'Reilly A Director
Enclosure:
Circular 76-06
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. Duke Power Company cc w/ encl:
D. C. Beam, Project Manager Post Office Box 223 29710 Clover, South Carolina J. T. Moore, Project Manager Post Office Box 422 29340 Gaffney, South Carolina t
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{ 9 JO N p } =* 3 i November 26, 1976 1E Circular No. 76-06 STRESS CORROSION CRACKS IN STAGNANT, LOW PRESSURE STAINLESS PlPING CONTAINING BORIC ACID SOLUTION AT FWR's D.ESCRIPTION OF CIRCIMSTANCES:
During the period November 7,1974 to November 1,1975, several incidents of through-wall cracking have necurred in the 10-inch, schedule 10 type 304 stainIcss steel piping of the Reactor Building Spray and Decay Heat
' Removal Systema at Arkansas Nuc1 car P) ant No. 1.
On October 7, 1976, Virginia Electric and Tower also reported through-vall cracking in the 10-inch schedule 40 type 304 stainless discharge piping of the "A" recirculation spray hear exchanger at Surry Unit No. 2.
A recent inspection of Unit 1 Containneat Recirculation Spray Piping revealed cracking i.inilar to Unit 2.
On October 8, 1976, another incident of similar cracking in 8-inch schedule 10 type 304 stainless piping of the Sefety Injection Pump Suction 1.irje at the Cinna facility was reported by the licensee.
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Infohnation received on the r.etallurgical analysis conducted to date indicates that the failures were the result of intergranular stress corrosion cracking that initinted nn the inside of the piping. A cormonality of f actorn observed associated with the corrosion mechanism l
vere:
1.
1he cracks were adjacent to and propagsted along veld zones of the thin-velled low pressure piping, not part of the reactor coolant i
system.
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2.
Cracking occurred in piping containing relatively stagnant boric acid solution not required for normal operating conditions.
1 3.
Analysis of surface producta at this time indicate a chloride ion interaction with oxide formation in the relativaly stagnant boric acid solution as the probable corrodant, with the state of stress I
probably due to welding and/or fabrication.
The source of the chloride ion is not definitely known.
However,.at ANO-1 the chlorides and sulfide level observed in the surface tarnish film near welds is believed to have been introduced into the piping during tenting of the sodium thinsulfate discharge valves, or valve leakage.
Similarly, at Cinna the chlorides and potential oxygen bb i
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IECircularNo.7646Jg(l7 Pl*.3L November 26, 1976 availrbility were assumed to have been present since original construction of the borated water storage tank which is vented to Corrosion attack at Surry is attributed to in-leakage of atmosphere.
chlorides through r: circulation spray heat exchange tubing, allowing
. buildup of contaminated water in an otherwise normally dry spray piping.
ACTION TO BE TAKEN BY LICENSEE:
1.
Provide a description of your program for assuring continued integrity of those saf ety-related piping systec:s which are not This f requently flushed, or which contain nonflowing liquids.
program should include consideration of hydrostatic testing in accordance with ASME Code Section XI rules (1974 Edition) for all active systemc required for safety injection and containment spray, including their rceirculation modes, from source of water supply up to the second isolation valve of the primary system.
Similar tests should be considered for other safety-related piping systems.
2.
Your program should also consider voluraetric examination of a representative number of circumferential pipe welds by non-destructive examination techniques.
Such examinations should be performed generally in accordance with Appendix I of Section XI of the ASME Code, except that the examined area should cover a distance of approximately six (6) times the pipe wall thickness (but r.rt less than 2 inches and need not exceed 8 inches) on eaci sic.c of the weld.
Supplementary exatiination techniques, such as radiography, thould be used where necessary for evaluation or confirm tion of ultrasonic indications resulting f rom such cxamination.
3.
A report describing your program and schedule for these inspec-tions should he submitted within 30 days af ter receipt of this Circular.
4.
The NRC Regional of fice should be infcrmed within"24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
of any adverne findings resulting during nondestructive evaluation of the acce u ibic piping welds identified above.
5.
A sumaty report of the examinations and evaluation of results should be suhm1Lted within 60 days from the date of completion of proposed testing end examinations.
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IE Circular No. 76-06 ' g g p[ p -
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November 26, 1976 i
i This summary report should also include a brief dencription of plant conditions, operating procedures or other activities which provide assurance that the ef fluent chemistry will maintain low levels of potential corrodants in such relatively stagnant regions within tho piping.
Your responsen should be nubmitted to the Director of this of fice, t
Division with a copy to the NRC Of fice of Inspection and Enforcement, of Reactor inspection Programs, Washington, D C.
20555.
t Approval of NRC requirements for reports conecrning possible generic problem has been obtained under 44 U.S.C 3152 f rom the U.S. General Accounting Office.
(GAO Approval B-380255 (R0062), expires 7/31/77.)
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