ML19329A571
| ML19329A571 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 02/02/1971 |
| From: | US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML19329A570 | List: |
| References | |
| NUDOCS 8001070568 | |
| Download: ML19329A571 (3) | |
Text
e, EfA1: COCK NID UILCOX REPORTS 1:N.*-136'l AND 1364 CRACRIt.C N;D I!;DICATIO:1S Ill REACTOR COOIZlT PIPI;.C FOR DURE POWER OCO:;EE Ui.IT 1 Docket No. 50-269 REPORT HAW-1363 The fissures found in the internal cladding of two pipe spools for the subject facility are typical for arc welding of austenitic stainless steel with inadequate control of the welding parameters. The report sug-gests that the low delta ferrite (assumed high temperature phase) is due to a chromito deficiency in the flux.
Chromitra addition in the flux is primarily for the purpose of acting as a deoxidizer, and fissuring in generally related to inadequate control of weldinr. variables and the chemical composition of the weld. Since no tests were performed on the cladding r:aterial af ter grinding had rernoved the fissures, the veld cheeistry below this level nas not been deterciined.
liovever, by applying new cladding over the affected areas H&W has covered these areas with acceptable cladding r.interial.
Uc find that the steps taken to rectify the claddiny, deficiency as identi-fled in the 11&V report are acceptable.
PIPORT 11AW-1364 A review of the subject report revealed that the defects in the cladding i
trere the result of a series of manufacturing and processing errors. These were:
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O (a) Contamination of the cledding surfacen by fron scale reaultina from carbon steel spacer bars used in the heating cycle prior to the hot-forniuf, operation.
(b) Prenning of thanc undetected contaninants into the cladding surf ace during hot-forming.
(c) The use of strong acidic type etchants, (i.e., Strauss Solution),
to identify the areas of contamination.
The cladding procedure for pipe elbows is the Dupont DETACLAD, or ex-plosion bonding, process.
The type 304 stainlens steel pinte material is applied prior to hot-forming followed by quench and towper treatments, and the postweld atress relief af ter the cibou halves have been ucided together.
The cladding is subsequently acnsiti cd vrought stainless steel material.
The indications, or fisnures, found in two of the elbown can be traced to an accelerated stress corrosion attack because of the exposure to etchants
. and nitric acid solutions.
In addition, a dilute Strauss solution has been used on sone of the elbows to identify iron surface contamination in con-tact areas. These procedures have since been abandoned. The report indi-cates that the cladding was cooled slo.ely from about 1900 which is the solution heat treatment temperature and also the hot-formings tenperature:
but omission is made of the temperature excursions to quenching-tempering and later stress relief temperatures.
It can be concluded that any benefits from a solution heat treatment have been lost in the subsequent temperature excursions. Furthermore, no Strauss test has been perforned to prove that tha cladding naterial is not severely sensitized.
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3 Because of the uncertainties with respect to the degree of sensitization present, we recommend that inservice inspection for pipe elbove be ex-j tended to include nondestructive examination of the cladding and its bond to the base metal. This augmented inspection shoulu be performed within 4" bands adjacent to the welds in these elbows.
The examination should be conducted prior to plant startup and during at least the first two refueling outages.
If no evidence of stress cor-rosion attack is observed during these inspections. the examination frequency may revert to the schedule specified in the ASME Inservice Inspection Code Section XI.
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