ML20085B888
| ML20085B888 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry, 05000000 |
| Issue date: | 10/11/1972 |
| From: | Gilleland J TENNESSEE VALLEY AUTHORITY |
| To: | Jennifer Davis NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| Shared Package | |
| ML20085B883 | List: |
| References | |
| NUDOCS 8307080535 | |
| Download: ML20085B888 (12) | |
Text
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E*NNESSEE VALLEY AU,THC TY CHATTANOOGA. TENNESSEE 374ol
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M,.,, OctoberllY1072 I
Mr. John G.
Davis, Director Directorate of Regulatory Operations United States Atomic Energy Commission Region II - Suite 818 230 Peachtree Street, NW.
Atlanta, Georgia 30303
Dear Mr. Davis:
This is in reply to your September 11 letter, RO:II:CMU, 50-259/72 h, 50-260/72-2, 50-296/72-2, which pointed out certain areas wherein Browns Ferry main steam isolation valves (MSIV) appear to be in nonconformance with statements in the final aafety analysis report (FSAE).
Our responses are contained in the enclosure and are numbered to correspond to the items raised in the enclosure of your letter.
We hope these responses will be satisfactory.
Very truly yours, 0[,
J.
E. Gilleland Assistant to the Manager of Power Enclosure 8307080535 721031 PDR ADOCK 05000259 A
PDR An Eque: Opportunity Employer
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ENCLOSURE With reference to your list of items which appear to be in non-conformance i
with our FSAR, va have the following comments:
1.
You are correct.
The main steam isolation valves were ordered to the provisions of GE Purchase Specification No. 21A1062-AL, Isolation Valves, in the Main Steam System. 'Ihe corrosion allowance is listed in 21A1062, General Requirements for Isolation Valves, Steam Piping Systems, Par. 5 2 9 It requires a mininte corrosion anovance 0.088" for carbon steci for 40 years service.'
TheFSARvaspreparedatalaterdatethanthespecificatdon.
Current practice cal.is for an allegance for corrosion of.120", and, unfortunately,.
that is the figttre which vs.s quoted in the FSAR Section 4.6 3 The louer vala. vas proper at the Eine of fabrication.
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Ilowever, even with the additional corrosien allowance, the extra safety margin in the original design provides sufficient stock to cover the discrepancy.
The MSIV was designed for 1250 psig (Pd) at 575 F, which under the provisions of NB-3543 (c), AS'E Section III 1971, by inter-
, polation in the Pressure-Temperature Rating Tables of IJTSI B16.5, results in an equivalent primary service rating (PSR) of 655 lbs.
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- Temp, Table 5-600 lb Table 6-900 lb F
550 1180 1775 600 1110
_1660 70 115 575 1145 pt.
1717
=
P
=
2 600 p
=
ri "E r2
7-960+ (900-600){1250-11Ff*o 103 PSR 1
=
l'll7_1145rL 572' 600 + 300 x.1835 PSR
=
655 psi PSR
=
The Vendor used a PSR of 680 in his actual design, as shown in the second page of the calculations submitted to IIeadquarters previously.
The required vall thicknesses are summarized as follows:
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PSR = 680 PSR =' 655
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t = 1 5 - 680 x 23 1 5 -655 x 23 1
2 x 7000 - 1.2 x 680.
-2 x 7000 - 1.2 x 655-t 1 779 1.710 r
c/a
.088
.120.
t 1.867-
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1.830 min (Note that there is an error in the fifteenth page, resulting in an additional.01" required t,, but still within the castihg specified minimumthickness.)
It is to be emphasized that these are body vall and neck thickness requirements, even though the dimension used for sizing is'the port.
diameter.
In fact, IfB-3542.1, ASIS Section III 1971, states:
"The minimum thickness of its body vall, including the neck, is to be determined from table IIB-35142-1, using the larger of the basic valve body inside diameters, d, in the reg.an near the velding ends...".
In lieu of the table we used the actual formula in B16 5 to ca3culate t -
m 4
r,,
ie TVA position that the minimum wall thickn
, calculated'on the,
act' al design conditions, with the addition of.the corrosion allowance u
stated in the FSAR is well below the minimum body wall thickness pro-vided by the castings. We request that this item be closed.
2.
In reviewing this condition, TVA concurs withpur evaluation of non-conformance with USAS B16 5, Figure 10,. Note 3 General Electric QA personnel are also in agreement.
It is our conjecture that these valves were inspected when assembled for hydrostatic test::, at which time end caps were probably velded on to weld preparations which con-formed with the vendors drawings. These drawings show weld prep details in agreement with Figure 10, B16.5 After the tests, the inspectors must have signed off. The caps were removed, and new weld preps nachined, without meeting the provisions of Note 3 The problem area is located at top of the run, over approximately a 60 sector nea'r the body bonnet at the crotch. Field repair of this condition can be accomplished by grinding and blending, anc :has been ordered by the NSSS vendor.
TVA submits this as an interim report: We acknowleckge the non-conformance, and 'are proceeding with field repairs. At the ecmpletion of the work, DRO will be asked to reinspect the' MSIV's on all th ree units.
N 3
TVA takes exception to this item being considered a non-conformance, as it did during the inspection interview of June 8 and again on July 11.
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It may be worthwhile to present some background iilormation.
At the carlier necting called to discuss the apparent defect in a Unit 2 main steam isolation valve casting, a very rough hand drawn sketch, enclosed Attachment A, was prose..ted to indicate the results of UT measurement to establish wall thickness near the defect to determine what ASTM radiographic standards were to be used in evaluating the RT indication.
The sketch attempted to show come dimensional evaluation.
The figure of 21/4" was intended to show the maxianum distance which could be covered by.UT, using the center of the veld as reference.
The17/8" and 5/8" dins. vere the estimated length and vidth of the indication as determined by the probe.
The statement: UT measurements 1.03" to 1.45" was indicative of the measured thickncas of either side of the veld.
Unfortuna'.cly. two lines were present in the sketch which appear to j
chou that the 1.03" dimension exists closer to the thicker portion of the valve than the 1.h5" dimension. Durir.g the discussion, TVA suggested that this was not possible, and that the 1.03 " dimension I
was erroneous and should to 1.63," but TVA agreed to remeasure the valve.
As a result of this commitment, the eiCht main steam isolation valves in storage for Unit 3 were evaluated and several measurements were taken in the crotch area in question. These measurements were taken O
using micrometers, calipers and a UT thickness gage (where practical).
We enclose a sketch, Attachment B, showing the l'ocation of the measurc-It is ments, which are reported in the Table of Attachment C.
readily apparent that all values are acceptable.
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On September 1,1972, one valve (Str 40-919) was sMected at random and _
inspected with a Uf thickness gage for wall thickness in the seat area of the valve. Eight measurements were taken circu iferentially around the valve in the thinnest portion of the reference area. A detail sketch, Attachment D, shouing the actual measurements, again proves that the valves exceed the minimum wall requirements.
If the calculations of item 1 are used with the actual port dimensions and the higher value for corrosion allcmance we calculate:
PSR = 655_
_PSR = 680 680 x 23.652
,655 x 23 652 7
t=15 15
' 2 x 7000 - 1.2 x 655"
'- 2 x 7000 - 1.2 x 680
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t =.1 759 1.830 c/a=.120
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.120 t,1n= 1.879" 1 950" It can be seen that all the thickness mensecuents in the thinnect area
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of the body exceed the higher t by at least lo percent.
g To resolve the problem of the sketch, Attachment A, a UT measurement was performed on the Unit 2 valve FCV-2-80 SER # 28-919 Attachment E shows a sketch of the actual measurements. The probe was calibrated on
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one of the open Unit 3 valves a' d checked against micrometer readings.
n The results of the resurvey indicate that the TVA interpretation of the original sketch was correct.
The TVA position is that all velding ends meet the provisions of USAS B16.5, par. 6.1:
"The welding ends of valves may be reduced below these
v x/
values by nachining the inside and outside surfaces to meet the pipe vall thickness as shown in Figures 9, 10, 11, and 12."
The valves racet the minimum body wall requirements of E16 5 as verified by measurement.
A non-conformance does not exist and we request that this ite:n be closed.
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of S
hEr011T }DR USE E!SID3 TVA O!!LY Measurer::ents Serin 1 I!uaber IIent 1;u er A.
B.
O.32-919 F393-1.h20 1.629 2.560 33-919 F2373 1.h 26 1.653 2 353 34-919 F2306 1.452 3.649 2.589 35-919 F2421 1.427 1.661 2.678 36-919 F2463 1.447 1.681 p.hg5 37-919 F2hlh 1.h32 1.623 2 350
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39-919 F2511 1.h 34 1.671 2.420 40-919 F24h3 1.409 1.630
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Seat Area M1 = 2.200
. MS M2 = 2.100 6
M3 = 2.160
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