ML20084B122

Review of Replies to AEC Questions by Con Ed on Indian Point Unit 2 Safety & Relief Valve Installation Reanalysis

ML20084B122
Person / Time
Site:	Indian Point
Issue date:	03/30/1973
From:	Foley W, Lofy R PARAMETER, INC.
To:
References
DC-104, NUDOCS 8304060138
Download: ML20084B122 (14)

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4,r REPORT

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• REVIEW of REPLIES to AEC QUESTIONS

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by CONSOLIDATED EDISON COMPANY on

. . r. :, J.'- INDIAN POINI UNIT -2 SAFETY and RELIEF P'

f, <,, VALVE INSTALLATION REANALYSIS

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.e/3 .' , [ ,. . Report No. DC-104 March 30, 1973

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NOTICE

. This report was prepared as a n account of ,

work sponsored by the United States '

Government. Neither the United States nor the United States Atomic EnerJy Commission, nor any of their employees, n.>r any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or-responsibility for the accuracy, compiuto-ness or usefulness of any information, apparatus, product or process disclosed, or l represents that its use would not infringe privately-owned rights.

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' REVIEW OF REPLIES TO AEC QUESTIONS 9 ,

BY CONSOLIDATED EDISON COMPANY ON

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' INDIAN POINI UNIT -2 SAFETY AND RELIEF

,; .:p.' VALVE INSTALLATION HEANALYSIS

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References:

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)l" l' ' 1.

j ,;,, O , , l, Letter of February 9, 1973, Re: Indian Point, Unit -2,

( * ,' AEC Docket No. JO-247, W. J. Cahill, Consolidated Edison lt .,'., ai, ', ' ,' Co. of New York to R. C. Young, Assistance Director for

[43 -

. Pressurized Water Reactors, Directorate of Licensing, g g.b .

USAEC, and

Attachment:

34 pages entitled " Additional I'$ ,f 4,,* Information Concerning the Re-Analysis of Safety and

• l

'. - 9 Q' ' f . Relief Valve Installations for ASME Class -1 and

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Class -2 Systems in Indian Point, Unit No. 2", dated I

,y 3. q. s Feb. 9, 1973.

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't' " $ ', ,- 2.

Criteria and Guidelines for the Design of Safety and

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• , [ 4 Relief Valve Installations on Westinghouse Pressurized 4 / '

Water Reactor Plants, October 1972, Westinhouse Electric

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Corporation, Nuclear Energy Systems, PWR Division (Received by PARAMETER in connection with Assignaent No. DC-103 on Surry -1.)

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As a result of our review of Reference -1 on the above subject, we have the following comments: (Item numbers

'.s .. / 4 !'i',[,,5? ' .

ty y ~ , - 1, > , - refer to Question numbers in the reference.)

3/ 1. We concur in the use of Dynamic Load Factor 9,; f:;;, g .6 .c W- j,',,

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(DLF) of 2.0 in calculation of the equiva-lent static loads applied to piping systems f'i. j J{ ' 7 by open discharge safety valve thrusts. For

} ;,#. .,; , g r- a ;s the single degree of freedom system, 2.0 is h ..= :t ' ,, 6 ,

the upper limit of dynamic load application f,1.,p 6,' (' r. -(.' ' 'O"* for an ins tfMtaneously applied force. This is shown graphically in Figure 7-2, page 7.7 h/ [ < * -

.' of Ref. -1 for a rise time (tr) equal to zero.

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('[1* p*w' .' f ,"'a We further agree in the classification of all

' 'N,5(,ll local stresses at the valve (branch) to pipe

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(header) intersection due to discharge thrust as primary. stresses. (It is assumed, of t,[ W m y,*y,. . , , course, that

. f7 stresses due to the discharge thrust only are appropriately combined with t" ,Q'.][N[Q !j q -

stresses due to internal pressure, dead

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waight and seismic effects as applicable in l

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,w g,i j A , ,' 1. (continued) f * .( making the stress evaluation in this classi-G[d u $[,Ifd1j 'i ,%.:(*'t  % . -l #)M,,,' , -

fication). The word " conservatively" (last line) requires some modification. Because the v @ d *.4. 'v. i

.. . . . safety valve thrust has Itechanical follow- ,

,p. 3,~, *

,&f.'p..g.* * ,, up characteristics, stresses are not self t'

.h. k! relieving, and both membrane and bending

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. ".,.*' , ; ," stresses can be classified as primary.  !

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Therefore, it is not evident that a '

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substantial degree of conservatism results 7,,,g-g'.Of'C* from the primary stress classification per

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M Q/$ Q 4,o My*%. . [L'd,;d'>

.g G ,? fl, O;p , ' 2. The Welding Research Council Bulletin No. 107

,5ff..[ 4'7['. '/,[ '; is the presentation of the "Bijlaard Method" E 4de' f ,' in general use.

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4. % r , m (,,,,.'.Cid " ~, , (Note: The 3rd Revised Printing, i

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April, 1972 is more recent than Rev. 2, 1M / ; '. [,9 '

July, 1970 referenced and contains

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some corrections, but no fundamental changes.)

*;gi r k a.M" A . ' ..'* ,

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This method of analysis of local stresses at f h,(.'). M [ cc intersections of cylindrical bodies cue to hf[.J,# b,

forces and moments can be applied by hand s W, Ot l f calculations or adapted to computer programs j

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as has been done by any number of users. While g 4 6, ;af"*. \': ;, , , we are not familiar with the CYLNOZ program

'g.g* hk/ 3,u specifically, there is no reason to doubt

,(d.shjjk ..fc,s' that it correctly interprets and executes

. f./ . .p- the Bijlaard curves and methods of WRC-107.

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Evaluation of the stresses calculated by '

h[*IG((P,

,y#; .j-4;3,4 / g.

O't';p

<**1 d.h l.s the CYLNOZ program as primary stresses and comparison with ANSI B31.1.0 Code allowables g'p.g h.vU,{Jy . d p 1s reasonable and in agreement with the W,'4'4 *p .'h]$*,, recommendations

. 3 lower allowable stresses of Ref. -2. Using the 6 l of B31.1.0,which  !

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was evidently used for construction of the G.* Indian Point Unit -2 systems, recognizes that

v. b.age., u s. .

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N t.k the quality requirements which warrant use ,

$T h%k. 4.- h. , of higher stresses in ASME-Section III or l ' k!fM MP,z ; ' ,

B31.7 systems were not in force at the time

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• 4 . .E 2. (continued) iM,? .<;,5. S ',' of construction.

. 4 The writers feel that

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some desirable conservatism results from Q.i. k....

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this approach.

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,, 3. Assuming the correct application of strain

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gages and interpretation of data, the

'N '[.4 %(1 f

J experimental stress analysis test described b'C.7@ "~ ~ ,, . ,.

,.q.a !g*l e appears to provide an excellent verification

[tr I),pd ,ti '

of theoretically obtained force, moment and

,, frequency values,

, ( g .tu *

, a s s t.* s c, g , , -

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i/i*:E M),lM N* Verification of a DLF of less than 1.25 is of particular interest and agrees with that f *Di 5, '

$)d*dy((( which might be obtained from Fig. 7-2, Page '

lh Me.1 j,h, n ...e s. .- 7,7 by comparing valve opening time versus the period of natural vibration of the valve:

p a.3 < ,j. ,l ,

Nat. Frequency = 22.7 liz. (Ref. -1) t .5 G .;.g

' 1 r. v

/- *- g. h'}f,; Period:T = 1/22.7 = 0.044 sec.

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4,','. Note that the period of natural

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vibration is close to the valve

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r{ ,[y ',' ','

• ti'/P.k.', ' ' opening and closing times of O.060-0.080 sec.

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.,v. .- Checking the tr/T relationship l of Fig. 7.7, the following DLF p p .1,. ,,0 , ,, ,

values may be obtained for opening g a,7 4.7; [ p .

• times (tr) of .O60, .070 and .OPO sec:

y m.@~ c,..;;9 Q's'f. ..t .'y. ',a$ 6 " . . %,' t*r/T m=. 0.060/.044 = 1.36 DLF = 1.21 W. J.'hsM (* r. yJ '.- 'E ' tr/T = 0.070/.044 = 1.59 DLP = 1.19 Ql 4 ~.3 lp.ek,y%,.

giq'r

.<'. y,y '

tr/T = 0.080/.044 = 1.82 DLF = 1.12 1 ,, 4 i -

T (ic' +.m. .. #.>2 <; n.. .

t [+,ty4 i ,,c 4. + * .T4' These values are close to and less than 1 -

n a .s - the 1.25 DLF stated.

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Page 7 j s. ..- ,

Report No. DC-104 3

l.

,'.. 3.

" 4; ,

(continued)

'l -

Note is taken of the fact that high speed movies verified that the actual angle of

{ ,[' # , I discharge of exit steam from the exhaust j', [; / -

stack did not vary more than 20 from the 330 angle. This should provide confidence

' 4 , ., , ?

i 'C, t .J in the assumed line of thrust for systems where the turning elbow and extension

' ' y $,,'- { , pipe are effective.

^ ., While the length of

7;.')l'

"- extension pipe used on this test is not

,, , [ y,.

, given, it was no doubt long enough to be effective for the 33 turning angle.

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(Ref. -2 recommends that "A straight ,

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length of at least one pipe diameter should -

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t v ,* '~i:

3 ' be provided on the end of the elbow to ,

assure that the velocity is fully developed

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at the desired angle.")

There is a discrepancy with the steam exit

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angle defined by the test and that shown

, y ,[ ' . ; . '

" ' ' " for the modified installation of the main L

steam safety valves for Indian Point, P, ki-

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Unit -2 on Figure 8a, Page 8-2. The test

y, 1,' ,M.

description under Question -3 defines O

y, e. '

exit as horizontal discharge, 900 exit '

' , " c e .f , g

• as vertical discharge and 330 exit, 4, J > < d . ' presumably as 330 above the horizontal.

i c.

,I a- Ilowever, Figure 8a shows the installation

[,, - ' as having the nozzle exits 330 from the a"

i '

vertical (or equal to a " test" angle of 570).

.' U' If the test results as reported

)p](J/

A 5 "q

are for the smaller angle, as it appears,

<^ , j t ', they should be reviewed for applicability

'.

• and reconciled with the installed angle.

't g .' g , .

Similarily, a review of the analysis for

'y .s..

qh,c,.& header stresses should also be made to make sure that the correct angle for

'- @ ."/' . c.7 application of the thrust force was used. 3 "t .. .

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Report No. DC-104

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The piping flexibility and stress analysis computer programs ADLPIPE and BEL-40 have

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been in use for a long time, are well accepted and non-proprietary in the sense o that they are available commercially from various computer services organiza-i f .

tions. Their description by the licensee 0'

requires no further comment unless v

detailed technical questions would arise.

Refer to observations on CYLNOZ program t

s contained comments on Question -2 above.

F,

'A E ( ' , 3 ' . The writers cannot comment from direct

~

c,~' " - ' knowledge on the Westinghouse FLASH-IV

s. -

program.

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5. a.

The licensee states that " thrust loading effects on piping systems were 4, g y.- evaluated using equivalent static loads". We feel that they must have applied a dynamic load factor in

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,, g

• arriving at the " equivalent" static loads. As the MEL-40 program does

'r not

.,l in itself have dynamic capability,

. , , it seems reasonable to assume that the

• DLF values were applied in this fashion.

j ' ,' This appears to be in agreement with

' the analytical rationale described p',

g further in response to Question -7 following.

• ).*?. #

b. (1)

The calculational method presented for obtaining the reaction force J~ ^ L (or input forcing function) for

~',' open systems has not been evaluated

' by the writers.

,' It is taken directly i - '

from the Westinghouse Criteria,- Ref. -1.

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Page 9 Report No. DC-104 t

s .

5. b. (1) (continued)

In that document, it is given as a method of verifying by independent

' analysis the manufacturer's published reaction force data. Thus, the designer has two sources available to him and a built-in check in arriving at the values to be applied

,g' in the analysis of a given system.

5. b. (2) Transient hydraulic forces at various points in safety and relief valve discharge piping are the input

. forcing functions for closed systems.

• The licensee's presentation does not a contain the extensive technical information which would be necessary to evaluate the applicability or accuracy of the FLAS!I-IV program

[ ,

in computing these forces.

' The authors concur in the explanation that the following stated assumptions

~,

are conservative:

1. " Valve Opens Full in 40 Milliseconds" -

This is obviously more severe than opening to 70% flow as specified by valve manu-facturer.

2. " Loop Seal Water is Pushed Ahead of

• Steam" - This assumption implies that

?' the slug of water stays intact and from this one can conclude it will exert

'. the maximum inertia effect at each elbow.

I' Break-up of the water slug would reduce its average acceleration and

' extend the time intervah and reduce the r a force of impingement at each turn. <

v4 <

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4 r;..-' .-. .

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= EMD

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(j Page 10 Report No. DC-104 1

5 b. (2) (continued) 3.

"Two-Phase Flow in the Downstream Piping is Homogeneous." - Some water i will flash to steam and separate which would tend to cushion the effect of the water slug. By conservatively assuming a homogeneous

- mass, this effect is not taken into account.

4.

"No Credit is Taken for Power Operated Relief Valves" The above assumptions were taken directly from Ref. -2. That document also explains that

- the analytical model used for obtaining hydraulic transient forces is considered to be conservative. An experimental program was being carried out (in late 1972) involv-ing the test of a safety valve with a water

,s seal, the results of which are to be compared with the values obtained from the analytical methods specified for use to date.

5. c.

The licensee's answer to the question asking for a summary of stresses for open and closed systems at high changes of flexibility notes that points of maximum stress occur  !

at elbows, tees and support points as would be expected.

The stresses are reported generally to be well within allowable limits. No further comment is needed here. The " Summary Report of Safety and Relief Valve Installation and Re-Analysis for ASME Class System in Indian Point Unit -2",-1Julyand Class -2 13, 1972,

[ referenced in this paragraph was not available for this review.

e t

I

. 1

.- . .- .~. .

l

i G7 ~ Page 11 Report No. DC-104 1

6. The question asks for the licensee's justification for using 0.159 horizontal and 0.109 vertical Design Basis Earth-quake (DBE'j inputs in lieu of results from a multi-degree-of-freedom system. It would seem to that stem from the questioner's understanding those type in a static valuesanalysis.

were used as shock factors The licensee's response indicates that a dynamic analysis was indeed performed incorporating multi-degree-of-freedom mathematical models and response spectra appropriate to the piping systems. c As discussed earlier, these dynamic forces must be handled as " equi valen t static forces" when using the MEL-40 program with shock factors.

7.

] A valid question is posed in asking for justification for the use of a (dynamic) load factor of 2 for closed systems. In his that response, the licensee first explains the maximum DLF for a single-degree-of-freedom system and a single, one sided pulse, is 2.0. He goes on to explain that, theoretically, for a two sided pulse, the maximum DLP can be greater than 2.0.

(Examples are given in Fig. 7-4). There-fore, the use of 2.0 as a basis for design must be validated for the systems in question.

The narrative response provides an accounting of dynamic time-history analyses that were performed with Westinghouse computer programs on _ typical systems.

Actual DLF's were deter-mined as the ratio of the maximum stress from the time-history analysis to the '

maximum stress from a static load analysis.

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(continued) 1 .

DLF's on the order of 1.20 to 1.64 are reported in Table 7-1 on page 7.5. The results of the described analytical work are reported to substantiate the use of a DLF of 2.0 for closed steam systems.

No doubt this is a safe conclusion for the systems analyzed or very similar systems.

The writers consider, however, that the last sentence of the response goes too far in stating more or less generically that "Since these systems include those with relatively low 4

mayimum stresses and those wi th relatively high maximum stresses, a design dynamic load factor of two for closed steam systems is sufficiently conservative to be consistent with purrent design practices."

(underlining added) We feel that, because it has already been indicated that the DLF on a hypothetical system could be greater than 2.0 for certain loading conditions, it is incumbent on the designer to show that 2.0 is adequate for any system in question. No further justifi-cation appears to be necessary for Indian Point - Unit -2 systems but the generali-zation is to be avoided. In other words, it appears to be quite possible to design a system wherein hydraulic transients could result in DLP greater than 2.0.

8.

The question asks for sketches of the required modifications used for all typical systems (on Indian Point Unit -2) which are 3

provided in Figures Ba, 8b, Sc and 8d on which we have the following observations:

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8.

(continued)

Fig. 8a " Main Steam Safety Relief Valve Arrangements" The angle of inclination of the safety valve discharge pipes being 330

<. from the vertical, is not as 1 described in the valve test program.

(See comments under Question No. 3 above.) Because in the modified arrangement,the safety valve discharge flow now impinges on the stack wall, attontion to securing the stack and assuring that discharge flow is not restricted is important.

Ref.

-2 recommends that "---- stacks should be designed so that back pressure does not affect the blowing valve reaction force."

Fig. 8b

" Main Steam Safety Valve Nozzle Reinforcement - Weld Buildup -

Indian Point, Unit -2" It is noted that local reinforcement in the form of a weld deposited pad has been provideo on the steam header.

This integral buildup is the preferred method of providing material to spread the valve thrust loads out to a larger area of the header wall. The Bijlaard Method (or WRC Bulletin No. 107) as discussed in the comments on Question No. 2 above,is directly applicable only for integrally provided rein-forcement. (For other designs, such l

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8. (continued) i Fig. 8b (continued) as welded-on plate pads, simplifying assumptions and the uce of bracketing calculations must be used in j

applying the WRC-107 rules.)

Fig. 8c " Pressurizer Nozzle" i

No specific comment is offered in connection with this "fix" which is not included in the discussion of Ref. -1, except to say that it is assumed that the reinforce-ment was applied in the form of integral weld deposit employing suitable heat treatment and non-destructive testing procedures.

The material is not given. This nodification could result in the need to review or revise the fatigue analysis of the nozzle.

Fig. 8d

" Restraint Added on A Typical System - at Accumulator Tank No . 24" No comment is made on this sketch which is not discussed in Ref. -1.

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