ML20086B516

Forwards Stress Analysis of Modified Main Steam Safety Valve Nozzle & Adjacent Steamline

ML20086B516
Person / Time
Site:	Robinson
Issue date:	07/10/1970
From:	Lofy R PARAMETER, INC.
To:	Seidle W US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML19289B536	List: ML20086B507 ML20086B516 ML20086B524 ML20086B528 ML20086B568 ML20086B573 ML20086B591
References
NUDOCS 8311170462
Download: ML20086B516 (4)

Text

_. - mma - m,,- w ~m

(&' & - .

. A

• ~ ~ - ~

FOR OFR$L USE ONLY. Pag 2 1 of 4

• f

. " a r a m e te r, n c.

Consulting Engineers

• Design - Analysis - Development 13545 W ATERTOWN PLANK ROAD, ELM GROVE, WISCONSIN $3122 786 7580 July 10, 1970 e

Ttr. William C. Seidle, Senior Reactor Inspector United States Atomic Energy Comnission Division of Compliance - Region II 230 Peachtree Street - TM Suite 818 Atlanta, Georgia 30303 Copies: R. II . Engelken, CO:Hg.

L. Kornblith, CO:Hg.

II. R. Denton, CO :lig .

J . C. Bryant, CO-II

Reference:

AEC Contract AT(11-1)-1658, Task A Consulting Services -

PAR : 69-70 A Assignment DC-67 f

/

Enclosure:

Attachment-1, " Stress Analysis of Ttodified blain Steam Safety Valve Nozzle and Adjacent Steamline" 10 pages dated July 10, 1970

(

\

Dear b1r. Seidle:

In conjunction with my June 29-30 trip to Robinson-2 with bicssrs. L. Beratan, CO:Hg. and J. Bryant of your office for a review of pipe stresses and hangers, I had the opportunity to view the work in process on the safety valve nozzle modification. Although we did not make his a formal inspection item nor discussed it in our m tings at the site., bir. Bryant agreed that it would be ppropriate to pass the observations resulting from our visual inspec- l tion to you in writing. The as-built sketch, check on I nozzle reinforcement and bending stresses contained in f Attachment-1, should also serve to document the new design i and satisfy most of the questions Icf t open in our pre- (~  !

vious reports. A new question regarding shell stresses L

in the steamline is raised in Attachment-1. I i 9311170462 700922 / '

PDR ADOCK 05000261 l p PDR i C __ _ > * #

- .. - . . . . . . . . ~ ..,a___..... .. . - . . . . - . _ _ . . ,

l , % ,~ ,m d U a r b ut c $e r, n c.

CON SU LTING ENGINEERS ELM GROVE, W 15 C O N 5 8 N Letter to Mr. William C. Seidle United States Atomic Energy Commission Division of Compliance - Region II July 10, 1970 Page 2 At the time of our site isit, we were fortunate to see nozzles in all stages of welding: at fit-up, after welding of TIG root pass and (2) cover layers, after welding flush to the surface of the steam pipe, and after completion of the reinforcing fillet. All welds after the three (3) Tungsten Inert Gas (TIG) passes with filler metal were Shielded Metal Arc Welds (SMAW). Preheat was maintained with resistance heaters (Cooper Coils) around the circumference of the steam pipe on either side of the nozzles.

Visual weld quality appeared to be good and the work was being well supervised. We did not go into procedures, qualification of welders, materials certifications, etc.-

but all replacement nozzles of Schedule 160 pipe appeared to have heat numbers stamped on them.

Becausc uf the difference in material thicknesses between .

the nozzle and J-prep in the steamline, the writer felt that obtaining a full penetration root pass suitable for radiographic inspection might be a tricky operation.

Thus, special attention was given to inspecting the back side of three (3) nozzle welds with a mirror. Most areas :-

showed good fusion and a uniform bead. Where laps or lack of fusion occurred, they were able to get in and grind the back side of the weld smooth. Thus, with radiographic inspection imposed, there is no doubt that full penetra-tion and acceptable weld joints can be obtained with this design.

The sketch on Page 2 of the attachment was made to record the modification as the writer observed it visually. No measurements were made and the dimensions shown, particu-larly for the weld contour, are approximate.

3M

.. o

, ( O fa rb ns eler, bn c.

CON %ULTlNG ENGINEfR$

ELM GROVE, WISCON51N Letter to Mr. William C. Seidle United States Atonic Energy Commission Division of Compliance - Region II July 10, 1970 Page 3 All valves have been modified to a weld prep approximately as shown on the sketch, but have not yet been set on the nozzles. A machined backing ring will be used for this attachment weld.

The power operated valves have also been cut from the smaller nozzles a short distance upstream from the safety valves. The reduced thickness sections of these nozzles have been removed, but the remaining nozzle extension and reinforcing collar left in place. The valves will be rewelded to the full thickness nozzle. This modification was not reviewed in any further detail.

The computation of required area reinforcement on pages 3 and 4 of the attachment indicates that the actual rein-forcement (estimated) is adequate without the reinforcing pad or collar. We did not know what corrosion allowance was specified for the line, but an average excess material thickness almost 1/8" is available in the 26" pipe.

Based on the most severe reaction loads, (assumed in our stress evaluation, Attachment-1 to letter of June 9, 1970 R.A. Lofy to W. C. Seidle) longitudinal stresses in the nozzle have been reduced to the order of 10,000 psi as calculated in the attachment. These nozzle stresses are within code allowables with the valve installed as pre-viously in a cantilevered nanner.

Tiowever, local shell s tresses in the steamline due to the popping reaction alone have been estimated at approximately 44,000 psi (see Attachment-1, Page 9), or approximately twice the equivalent Code allowable (1.5 S) for local bending plus membrane of 22,500 psi. Total shell stresses should be considered by the A/E in the design, s

a

F~ .* **

p

('"}

V U a r b nt e lc ry In c.

CONSULTING ENGINEER $

ELM GROVE, W 15 C O N $ 1 H

Letter to Mr. Willian C. Seidle United States Atonic Energy Comnission Division of Compliance - Region II July 10, 1970 Page 4 External supports or braces, if installed, can absorb reaction forces and further reduce both gross bending stress in the nozzle and local shell stress. However, care must be exercised in the design of any braces to avoid imposing any new loads on the valves, nozzles, or steanline due to thernal restraint. We recommend a review of the final design in this regard.

I hope this helps to complete the picture on the Safety Valve ??ozzle failure and modification. Other reduced section joints were not reviewed in this last inspection.

It appears that I will be at Robinson again during the last week in July to complete the hanger review with Mr. Heratan. If there is anything further that I can do on the nozzle replacement or in other areas at that time,.

please let me know.

Very truly yours, Ps ' '?TER, Inc.

v

, e W Richard A. Lofy, P.E. .

Consulting Engineer RAL/jng 1

o e

o b