ML19210E918

Final Deficiency Rept Re Main Feed Pipe Spools.Nrc Found Nine Pipes Not in Compliance W/Asme Code Physical Impact Requirements.One Hot Bend Spool Being Replaced.Others Operate Satisfactorily at Min Svc Temp of 70 F

ML19210E918
Person / Time
Site:	Midland
Issue date:	11/19/1979
From:	Donna Anderson BECHTEL GROUP, INC.
To:
Shared Package
ML19210E917	List: ML19210E916 ML19210E918
References
MCAR-29, NUDOCS 7912130224
Download: ML19210E918 (4)

Text

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Bechtel Associates Professional Corporation Attachment to Howe-310-79

SUBJECT:

MCAR 29 (issued S/22/79, revised 5/25/79)

Impact Testing of Main Feedwater Pipe FINAL REPORT DATE: November 19, 1979 ,

PROJECT: Consumers Power Company Midland Plant Units 1 & 2 Bechtel Job 7220 Introduction This final report is prepared in response to Midland project management Corrective Action Report 29. This consludes and summarizes our actions as previously reported in Interin Reports 1 through.4.

Description of Discrepancy During a review of Grinnell docunents, the NRC identified nine pipe spools f abricated f rom ASME SA 106 Grade B pipe, Heat N-32762, which f ailed to nect the physical impact requirement for the material in acccordance with ASME Section III Class 2 Code criteria. Grinnell subsequently notified Bechtel of the potentially reportable discrepancy.

Potential Safety Implication A potential safety prob 1cn would exist if inadequate material impact toughness properties at low feeduater temperatures resulted in, or contributed to, a main f eedwater line break.

Summary of Investigation and Historical Background Bechtel, af ter being inforced by Grinnell that a discrepancy with poten-tial saf,cty implications existed, reviewed at Grinnell 70 spool data packages for impact test properties. This review covered all natcrial requiring Charpy impact testing. This review was done to determine whether additional material, other than that identified during the NRC audit, cet specifications and ASME Section III, Class 2 Code require-ocnts.

The specific Code requirements are as follows: .

In accordance with NB 2332(1) of ASME Section III, test three Cv (Charpy V-notch test) specimens at a temperature lower than er equal to the lowest service tenperature. All three specimens shall meet the requirc-ocnts of Ta ble HB 2332-1.

According to Tahic NH 2332-1, the required Cv values for piping are as f ollows :

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. Bechtel Associates ProfessionalCorporation HCAR 29 Final Report

- Page 2 Nominal Wall thickness Lateral expansion (mils)

No test required 5/8" or less Over 5/8" to 3/4" (inclusive) 20 Over 3/4" to 1-1/2" (inclusive) 25 Over 1-1/2" to 2-1/ 2" (inclusive) 40 Subarticle NB2350 of ASME Section III permits one Charpy V-notch impact retest (consisting of two additional specimens taken as near as practicable to the failed specimens) to be conducted at the same temperature provided the following:

a) The average value of the test meets the minimum requirements.

b) Not more than one specimen per test is below minimum.

i c) The specimen not meeting the requirement is not lower than 10 ft-lb or 5 mils below specification requirements.

The above spools were fabricated from a total of 16 heats. Of these heats, two material test reports (for Heats N-32762 and L-20479) contained questionable data.

For Heat 32762, Grinnell had performed four separate tests as identified below: .

a) 19151: Test voided because specimen oriented incorrectly b) 19676-1 Results: 21, 40, and 45 mils (The minimum requirement is

- 25 mils for a material with a nominal wall thickness of 0.937 inches.)

c) 19676-3 Results: 21, 40, 45, 25, and 18. The last two were not nottd as retests, which was permissible, though Test 19676-1 indi-cated that only three samples were tested.

The failing 18 mils value precludes a further test at the same temperature.

d) A subsequent test was performed by the ITT Grinnell test laboratory with passing values at 29, 30, and 32 mils. This was a third test of the heat which is not allowed by the Code. This test was accepted by ITT Grinnell Industrial Pipe Inc.

Heat N-32762 was considered questionable because Grinnell performed more than one retest, which is not allowed by ASME Section III, Class, 2 Code, as discussed previously.

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.. .Bechtel Associates PiofessionalCorporation HCAR 29 Final Report Page 3 In May 1979, Grinnell tested three samples of Heat N-32762. These samples were f rom a f abricated spool which was still at its facility, spool lELB-2-S-638-13-2. This spool which consisted of a straight piece of pipe which was hot-bent, air-cooled, and then full-furnace stress-re lieve d. These sampics yielded results of 9, 6, and 17 mils lateral expansion. Because the samples were taken near the area of the bend, it was thought that they may have been f rom a heat-af fected zone (an arca which had received an intermediate heating and cooling cycle because of its proximity to the hot-bend area).

Grinnell has indicated that measurement of the actual sample location relative to the area which was heated and bent, shows that it was not significantly heated during the bending cycle.

Grinnell submitted a graph verifying that the above sanples were not in the heat-affected zone of the bend.

The Heat L-20479 retest at 30F was considered questionable because the acceptable test results were based on material in a stress-relieved condition. Grinnell's rationale was based on its experience that a

'suberitical (1100-1200F) heat treatment has the effect of reducing the spread of toughness values (smaller variances) and slightly improving lateral expansion values through a sof tening mechanism (a slightly reduced yield point). The rctest of Heat L-20479 af ter stress-relieving, met the code iupact test requirements. Houever, Crinnell concedes that its rationale, as demonstrated by the previously identified poor impact test results of Heat N-32762 af ter stress relieving was not 100% consistent, and as a result, it believes that other stress-relieved heats would also be suspect in relation to the repeatability of the impact properties at 30F on each spool.

Grinnell rationalized that because it did not obtain improved Charpy test results 'for Heat N-32762 af ter stress-relieving, Heat L-20479 cannot be considered to have the desired inpact' properties (+30F) cither.

Bechtel investigated the minimum service temperatures for all questionable spools in the feedwater system. In accordance with Code definitions of' . . ...

minimum service temperature and the operating criteria for the applicabic .

portion of the system, a minimum service temperature of 70F is required.

However a minimum service temperature of 30F was originally specified, based on the minimum expected service temperature for any fluid piping -

system within the plant. The 30F tenperature was chosen to achieve a

-uniformity in testing requirements for the project.

Grinnell submitted 2 supplier deviation disposition requests (SDDRs) with test data requesting Bechtel to revise the temperature requirement for inpact testing f ron 30F to 70F for all spools of Heat L-20479 and all but spool 1-ELB-2-S-638-13-2 of Heat N32762. Bechtel approved the SDDRs based on the above-identified rationale. All spools tested passed at 70F or lower.

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Bechtel Associates ProfessionalCorporation MCAR 29 Final Report Page 4 The test results for lleat L-20479 at 70F are as follows:

Impact Lateral Material Testing Toughness Expansion Percent Identification Tenpe ra tu re ft-lb Mils Shear 76-1 +70F 63 51 60 76-2 +70F 40 4 '4 50 76-3 +70F 57 60 50 The test results for Heat N-32762 at 60F are as follows:

N-32762-7 +60F 136' 87 100 N-32762-8 +60F 53 48 60 N-32762-9 +60F 53 49 60 Spool lELL-2-S-638-13-2 of Heat N-32762 was not placed on an SDDR. This is the previously identified hot bend spool which had received full-furnace stress-relieving and. yielded uniformly excessively lower test results.

Therefore, it was decided to replace that spool. Grinnell is replacing spool lELB-2-S-633-13-2 with one fabridated from ASME SA 333 Grade 6 caterial.

The other hot-bend spools in the feedwater system were not fabricated from the questionable heats and were acceptable in the as-received condftion.

Corrective Action As a result of the determination that satisfactory operation at the minimun service tetperature of 70F is provided by the applicable portion of the installed feedwater piping spools, no corrective action is required. Grinnell is replacing the one hot-bend spool, 1ELB-2-S-638-13-2, uhich had not been shipped. .

Reportability Project engineering's final evaluation is -that the originally reported discrepancy of the subject MCAR has been resolved and thus there is not a reportable condition within the requirements of 10 FCR 50.55 c.

Suhaitted by: eg Approved by: /[.92.7J $ Md_.8

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