ML17037C148

Letter Concerning Stub Tube Post Hydro Inspection and Advising That Agreement on the Dye Test Procedures to Be Used with the Division of Compliance Has Been Reached

ML17037C148
Person / Time
Site:	Nine Mile Point
Issue date:	12/31/1968
From:	Pratt M Niagara Mohawk Power Corp
To:	Morris P US Atomic Energy Commission (AEC)
References
Download: ML17037C148 (4)

Text

NIAGARA MOHAWK POWER CORPORATION NIAGARA~

MOHAWK I

300 KRIK BOUI KVARO WKST SYRACUSC, N. Y l3202 December 31, 1968 CA I

>>>>t

~ -a Q

C r>

f>>I rn CJ Dr. Peter A. Morris Director Division of Reactor License Atomic Energy Commission Washington, D. C. 20545

Dear Dr. Morris:

Re:

Nine Mile Point Nuclear Station Docket No. 50-220 fl."

Stub Tube Post H dro Ins ection On December 17, 1968 you suggested we make a post hydro dye penetrant test on the remaining 54 stub tubes including the field welds, shop welds, and stub tube surfaces for the Nine Mile Point vessel and that we reach agreement on the dye test procedures to be used with the Division of Compliance before proceeding with the work.

Such agreement on procedures has been reached and willbe followed.

We respectfully request your further consideration of this matter.

We pro-pose to dye check only the remaining 54 stub tube field welds, omitting further shop weld and further stub tube surface inspections.

We present the following reasons in support of this proposal:

1) SHOP WELDS; All of the shop welds were installed, inspected, and tested prior to vessel shipment.

These welds passed shop and field hydro testing and vessel was stamped by code inspector following shop hydro.

There is, in our opinion, no justification or reason for re-inspection of these shop welds.

We say this with particular emphasis in view of the fact that we have ourselves inspected 75 of the 129 shop welds in the field following the field hydro and all were found acceptable.

2) STUB TUBE SURFACES:

Of the total 129 stub tubes, 75 were tested and all other accessible sensitized stainless steel surfaces were tested and found accep-table.

Further, the AEC, we understand, has not questioned and agrees that no

t l

t

stress corrosion cracking exists.

We understand that tests at other sites have shown that if stress corrosion did exist, it would have been detected in the testing which we have already done in the post hydro inspection.

3) FIELD WELDS:

We have ultrasonically tested all 129 stub tube field welds both before and after hydro testing.

The initial pre hydro ultrasonic testing did not indicate any significant defects.

Nevertheless, to assure no possibility of leakage over a long lifetime, we decided to cap 56 of these, field welds.

The capped welds were ultrasonically tested as the capping was done to assure that there was full integrity of the weld.

Following the field hydro tests, these 129 field welds were again ultrasonically tested and found to be satisfactory.

The ultrasonic inspection gives an in-depth testing of welds.

The dye penetrant inspection only shows surface conditions.

30 of the 56 field welds which were capped in July as described above are included in the remaining 54 field welds and have had the pre and post hydro ultrasonic tests in all cases as described above.

A dye penetrant test, however, was not applied to these 54 field welds following the hydro tests.

In view of the above, and to expedite the project schedule, we are proceeding at the present time to have the 54 remaining field welds dye penetrant tested.

We expect to complete this work about January 4, 1969.

'f you agree with our proposal, Supplement No.

5 willcontain suitable statements to properly amend previous statements contained in Suppl'ement No.

1 with an additional statement:

"The remaining 54 stub tube field welds ar'e in the process of being dye penetrant tested in accordance with procedures agreed upon by the AEC Division of Compliance."

Very truly yours, M. H. Pratt Vice President and Executive Engineer

J J

JL J J

/

4

~ r

A c

/ah h

VI

~

vcr I

1 f

r

~

r

~

II 4

J ',Q 1.I 40t J

~

I. LV c

r J'

r

-r e r J 0 r/ 0

/

J r

J A

A r

~ ~

r

=V V

vv, ~

h c

C t

r r ~ h --vI-<<L

'VJ "4k 'J~rrvv/WJ Q w V.~

I t

\\

Jc' r

~ I J'&5

~ v CSv I J.

/J.J0 A

r

~

r.

l~'

C J.

J'

/[

Ivr c

J.

vwV v

~

J JI

. C

~ hatt c.

r r

r'V r J4 r

~ ~

J QJ JI r

v II

~

5