ML19210A619
| ML19210A619 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 11/10/1977 |
| From: | Herbein J METROPOLITAN EDISON CO. |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| GQL-1508, NUDOCS 7910300654 | |
| Download: ML19210A619 (3) | |
Text
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METROPOLI FAN EDISON COMPANY POST OFFICE BOX 542 7EACING, PENNSYLVANI A 19603 TELEPHONE 215 - 929 2001 November 10, 1977 GQL 1508 Director of Nuclear Reactor Regulation Attn:
R. W. Reid, Chief Operating Reactors 3 ranch No. h
.377 U. S. Nuclear Regulator / Cecnission Washingten, D.C.
20555
Dear Sir:
"'hree Mile Isla:,d Nuclear Station Unit 1 (TMI-17 C Docket No. 50-289 Operating License No. DRR-50 Decay Heat Pump Shafts In our letters of September 28, 1977, and October 5, 1977, en the subject Decay Heat Pump Shafts, Met-Ed advised that the feasibility of metallographic rep-lication and hardness tests to verify the heat treated ccndition of the TMI shafts was under investigation. Cur letter of October 27, 1977, advised that we had scheduled, concurrent with the vibration and UT testing during the first week of November, a EHN Hardness Test, a Resistivity Measurement Test using a "TEV0" tester, and a Magnetic Permeability Test employing Eddy Current testing, to verify to the extent possible, the heat treated condition of the installed shafts.
In preparing for the EICT Hardness Test, it was determined that there was insufficient clearance to do this test on the shaft end.
W rther, since spherical indentations in excess of 0.020 inches deep can result from performing this test, it was felt that it was not advisab]e to perform this test on the cutside diameter of the shaft, although that is the only location where sufficient clearance is available. Instead, the hardness readings were taken on the outside diameter of the pump shafts between the =ctor coupling and the pump hcusing using the Senadur Model 10C-1 Ultrasonic Hardness Tester manufactured by Krautkramer - Branson. This instrument utilizes a 665 gran load on a Vicker diamond point indentor with a direct readout in Rockwell C hardness numbers. Because of the light penetrating load used by this instru= sat, the hardness readings are surface values and are consequently affected by surface conditions. Therefore, any cold verking of the surface as a result of the cachining of the shafts vill tend to produce slightly higher hardness readings, which would make the material appear as if it had been heat treated at a lever temperature than it actually was.
The average hardness readings of the "A" shaft of Re 36.52 vith a standard deviation of 2.3h, and the "3" shaft of Rc 35 5 with a standa-d deviation of 3.3h, are within the range for H-1150 material of Re 28-37.1/
h d dition, the shaft material meets the specified hardness requirement of ASSE:SA 56h Type 630 for the H-1150 ccnditicn of Ec 28 mini =un.
1/ Armco 17 h FH Precipitatien--Hardening Stainless Steel 3ar and Wire A =co Steel Corporatien, Saltimore, Maryland 1492 187
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- GQL 1508 Tovember 10, 1977 R. W. Reid, Chief _
Preparation for the evaluation of the Resistivity test and the Magnetic
- ?erreability Test included the production of calibration standards by which the tests could be qualified. These standards consisted of four heats of Ccndition "A" material, heat treated to H900, H1025, H1075, H1100, and H1150.
After preparaticn of the standards and upon cc=pletion of the "TEV0" tester evaluation, 3&W concluded that a suitable and accurate technique had not been develcped, and therefore, declined to perform the test on the pu=p shafts. 3&W further indicated that the "TE70" tester would probably not be able to identify the exact heat treatment of the shafts due to the large overlap in readings produced b:e the different heats and heat treatments.
Magnetic Analysis Corp., whose equipment and personnel were being employed to measure variations in magnetic permeability via eddy current testing, also experienced equipment calibration problems.
It was determined that when using a hand held probe, it is possible to produce variations in readings simply by varying the contact pressure and angle between the prebe and the test specimen.
In addition, test specimen gecretry appeared to affect the results. In pre-paring the calibraticn standards, different diameter bars were used. During the calibration attempts, it appeared that the size cf the bar and position of the probe also affected instrument cutput. Because of these variables, it was decided that this test method would not be utilized until reproducible laboratcry results could be obtained. However, as with the "TE70" tester, exact identification of the shafts' heat treatments may not be possible.
In s-a f, the average Rockwell C hardness values are within the range for H1150 material. The other non-destructive methods for determining the heat treatment conditions of the shafts are not presently reliable, and were there-fore, not employed. The only remaining method of examination that we are aware of would require re=cval of a chip from each shaft. This chip cculd be used for microhardness and metallographic analyses and retained austinite measurements.
Met-Ed has censidered re=cving a chip frc: the center of each shaft but decced this to be inadvisable, since permanent damage to the shaft could result.
It is Met-Ed's present position that the heat treated conditicn of the Decay Heat Pu=p shafts has been adequately established and that further hardness and UT testing which requires shaft unceupling is not necessary. Unless otherwise directed, Met-Ed does not intend to perform further shaft testing.
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J. G. Herbein Vice President JGH:FJS:tas 992 188