ML19326B664
| ML19326B664 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 08/29/1975 |
| From: | ARKANSAS POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML19326B653 | List: |
| References | |
| NUDOCS 8004170511 | |
| Download: ML19326B664 (4) | |
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' Abnormal Occurrence Report No.
50-313/74-11B 2.
Report Date:
August 29, 1975
'3.
Occurrence Date:
November 7, 1974 4
' Facility:
'Arkans'as Nuclear One-Unit 1 Russellville, Arkansas 1
5.
Identification of Occurrence:
Reactor Building Spray Pump P35B suction line leak.
6.
Conditions Prior to Occurrence:
Steady-State Power Reactor Power 0
MWth Ib t. Standby Net Output' 0
MWe Cold Shutdown X
Percent of Full Power 0
4 Refueling Shutdown Load Changes During Routine
's Power Operation Routine Startup Operation Routine Shutdown
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Operation Other (specify) s 7.
Description of Occurrence:
See Abnormal Occurrence Report No. 50-313/74-11.
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Abnormal Occurrence Report No.
S0-313/74-11B 8.
Designation of Apparent Cause of Occurrence:
Design Procedure t'
thnufacture Unusual Service Condition Including Environmental Installation /
Construction Component Failure Operator Other (specify)
X The apparent cause of the failure of the piping was intergranular stress-assisted corrosion cracking (IGSACC). This was caused by a number of coexisting circumstances which were present in only Heat No. 800201 of the Schedule 10 stainle<s steel piping used in the Reactor Building Spray system.
9.
Analysis of Occurrence:
Sections and samples of the failed piping and from other heat numbers of Schedule 10 piping in the Reactor Building Spray system and connected Decay !! cat Removal system were analyzed by Bechtel's San Francisco Materials, Fabrication and Quality Control Services (MF6QCS) laboratory and Southwest Research Institute of San Antonio, Texas.
The following conclusions were reached:
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- 1) All leaks occurred in 10-inch Schedule 10 Type 304 stainless steel 4
pipe manufactured to ASTM-A358 from one heat number of steel, Heat No. 800201.
- 2) Heat No. 800201 steel was found to be partially sensitized in the "as delivered" condition. However, the pipe material met the
^z requirements of ASTM-A358 and passed the Practice A and E tests of ASTM-A262 which determines the dcAtee of sensitization of a material.,
- 3) The contributing factors in the IGSACC were determined to be:
a) High carbon content of Heat No. 800201 material, b) Partial sensitization due to the still air cooling in heat treatment by the pipe manufactur'er.
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-Abnormal Occurrence Report No.
50-313/74-11B 9.
Analysis of Occurrence (cont.)
c) Sensitization in the heat-affected zones (RAZ) near welds, produced by welding heat.
d) Stress produced by welding (always present),
e) The existance of one or more corrodents. The corrodents are believed to be chloride ions and/or ions of sulfur oxides.
Extensive analysis of water samples taken from the failed piping revealed 2 PPM chloride ions and 1100 PPM total sulfur.
- 4) Specimens and/or sections of the different heat number Schedule 10 piping from the affected systems were examined by Bechtel's MF6QCS and Southwest Research to determine the degree of sensi-tization. MF5QCS found only Heat No. 800201 to be partially sensitized. Southwest Research also found Heat No. 800201 to be partially sensitized as well as a section of Heat No. 2P-3352.
Another section of 2P-3352 was found to be normal, with no sensi-tization, indicating that the observed sensitization is confined to particular individual pipe sections and is not a character-istic feature of all material from this heat.
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and found to be scand with no abnormal metallurgical conditions produced in the HAZ.
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Abnormal Occurrence Report No.
50-313/74-11B 10.
Corrective Action:
All cracks have been repared by replacing a section of the pipe with 304L stainless steel pipe or removing the section of pipe and capping the exposed ends (i.e.10" crossover line).
The following action is to be undertaken in,the near future:
- 1) An upgraded surveillance program of both visual and volumetric examinations including:
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a) Periodic walk-through examinations for leaks in areas con-taining pipe from Heat No. 800201 and the section of sensi-tized piping associated with Heat No. 2P-3352, to be gradually phased out if no further leaks are found.
b) A volumetric inservice inspection program following the guide-lines of Article IWC-2000 of ASME Se'etion,XT 1974 edition (Table IWC-2520, CG) for piping systems containing material from Heat No. 800201 and the section of sensitized piping associated ~with Heat No. 2P-3352 will be performed until the results indicate that further inspection is no longer needed.
- 2) A program of sampling and flushing of normally stagnant safety-
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related systems containing potentially corrosive chemical addi-tives.
- 3) An extensive study has been undertaken by Failure Analysis Associates for APSL' to show that a catastrophic failure will not result from a postulated crack in the Schedule 10 piping under design stresses.
s 11.
Failure Data:
See AOR 50-313/74-2 and 50-313/74-11.
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