ML17194B276

Forwards Target Technology,Ltd Revised Draft Interim Progress Rept, SEP Topic III-5.A,High Energy Pipe Breaks Inside Containment, Clarifying Five Items Identified in NRC Draft Evaluation Requiring Resolution

ML17194B276
Person / Time
Site:	Dresden
Issue date:	08/23/1982
From:	Rausch T COMMONWEALTH EDISON CO.
To:	Oconnor P Office of Nuclear Reactor Regulation
Shared Package
ML17194B277	List: ML17194B276 ML20063H048
References
TASK-03-05.A, TASK-3-5.A, TASK-RR NUDOCS 8209010170
Download: ML17194B276 (20)

Text

CommonweaAEdison One First Nationa~. Chicago, Illinois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 Mr. Paul O'Connor Project Manager Operating Reactors Branch No~ 5 Divtsion of Licensing U.S. Nuclear Regulatory Commission Washington, o;c. 20555

Subject:

Dresden.2 August 23~ 1982 SEP Topic:

III-5~A, High Energy Pipe Break Inside Containment

. NRC Docket*50-237 Reference (a): D~M~ Crutchfield Letter. to L~ 'o.'elGeorge *dated June 29, 19.82

'(b): T~J~ Rausch 'Letter to D.M. Cruchfield dated June 4, 1982

Dear Mr~ o**connor:

Reference. (a) requested additional infor~ation.concerning evaluatibn criteria for cbntainme~t integrity, dama~e crtteria for jet impingment, target pipe analysis criteria and fY'.act~~e mechanics approach which were evaluated in the Interim Progress Repoprt (Reference b)~

Enclosed for your review is Attachment 11 A 11 containing a revised draft report dated JlJlY 27, 1982~

Please address any que~tions you may h~ve concerning this matt~r to this office~

One (1) signed original and fdrty (40) copies of this transmittal have been provided for your use.

SPPJ:mnh Attachment cc:

RIII Resident Inspector, Dresden Very truly yours:

~cfl/'~

Thomas J. Rau~ch Nuclear Licensi*ng Administrator Boiling Water Reactors Gregg Ciwalina, SEP Integrated Assessment Project Mgr. (wtatta*c*hment}

-82o9010170-a2oa23 i

PDR ADOCK 05000237 P

PDR

--~-----

,\\,.,'..

/**

t' TARGET TECHNOLOGY LTD.

-*. ~*

8209010297 820823 PDR ADOCK 05000237 p

PDR ATTACHMENT A SEP TOPIC III-5.A HIGH ENERGY PIPE BREAKS INSIDE CONTAINMENT DRESDEN NUCLEAR POWER STATION UNIT 2 DOCKET NO. 50-237 I

I I

~..

July 27, 1982.

"~- f.

TARGET TECHNOLOGY LTD.

Commonwealth Edison Company submitted an Interim Progress Report on June 4, 1982 (Reference 1) which outlined the evaluation criteria, analytical approach, and results which were available at that time.

The NRC Draft Evaluation of SEP Topic III-5.A (Reference 2) identified areas where clari-fication of the methods used and where additional information concerning the assumptions are required for staff acceptance of* CECo's evaluation.

The five items (B.2, B.7, B.8, B.9, and B.10) identified by the NRC which remain to be resolved are addressed below.

The applicable portion of the NRC evaluation item is repeated for clarity.

B.2 "Current criteria require that through-wall leakage cracks be postulated in moderate energy line piping (<2000F and <275. psig)~

The license~ has not addressed this subject in this SEP topic

• assessment."

The effects of moderate-energy fluid_systems will be evaluated using the fol lowfog cr.i teri a:.

• .~ -*--;. _

~.*;

1. for piping systems that by plant arrangement and layout are isolated and physically separated and remotely-located from systems and components important to safety, through-wall leakage. cracks need not be postulated.

2.

For piping systems that are located.in the same areas as nigh-energy fluid systems which, by the criteria of Reference 1 Section 3.0 have postulated pipe brea~ locations, through-wall leakage cracks need not be

. postulated.

3.

For piping systems that are located in areas containing systems.

and components important to safety, but where no high-energy fluid systems are present, _through-wall leakage cracks should be postulated at the most

. *-adverse location _to.. evaluate the effects -of the resulting water spray and

-~--_.. __ ;*.flooding.*** Fluid flow from a crack is based on a circular opening of area equal to that of a rectangle one-half pipe-diameter in length and one-half pipe wall thickness in width..

-~

. ;, *~, *

• .. * -~ ~.:,* *... *. *~*. ':,'.'.

The environmenta 1 effects of pressur*e ~*'temperature, humidity and flooding are evaluated under SEP Topic III-12, "Environmental Qualification of Safety-Related Equipment" and were not considered in this evaluation.

Structural l~ading effects resulting from fluid flow through the crack, will be considered on safety-related systems, structures and components.*

• s.7 We have reviewed the information pertaining to the pipe whip and jet impingement interactions with the drywell liner, Reactor Pressure Vessel (RPV) pedestal and biological shield wall. Based on the information submitted in Reference 1, we have determined that the licensee's approach is, in general, acceptable except as follows:*

"~

I '

',-.., ~. ' -. ~

TARGET TECHNOLOGY LTD.*

a..

Section 4.2 of Reference 1 references Chicago Bridge & Iron.

• Company (CB&I) Test Report (Reference 5). The CB&I test indicates that when a spherical shell s~gment having a shell thickness of 0.75 inches is loaded over a large enough area, i.e., equivalent to a 14 inch diameter or larger circle, deformation of the plate over 3 inches can occur without failure of the plate segment.

Based on this test result, the licensee concludes that for breaks occuring in piping greater than 14 inches in diameter, even if contact occurred with the drywell liner, the amount of liner deformation, as limited by the concrete shi.eld wall, would not result in a liner failure. Accordingly, no acceptable interactions are con-sidered to result.with the drywell as a consequence of breaks postulated in piping greater than 14 inches in diameter.

• However, it should be noted that the CB&I test was performed

': under*essentially static conditions. *It.is not clear that

• *..

• the test result is also val id for the.dynamic loading which would be experienced.as a result of.pipe whip., In addition, the particular test applies a concentrated load of 235 tons over an area, equivalent to a 14 inch diameter or larger circle. This assumption may-not always be valid because the impact area of a 14 *inch diameter or 1 arger pipe may be

• smalle~ than the assumed area. Thus, oor concern is that

• in the case of applying concentrated dynamic load over a.

• small area the. steel plate may be perforated before the deformation is terminated by the concrete shield wall..

Ther.efore, based on the information submitted,* we have determined that the licensee has not provided a sufficient justification -

. ;*.. to use the CB&I test results in its case.*._.:

0

- :~.,.f:.. _-

'.J: ***p:'**

-*.. ~~*.** !'"-.'

• • -*-:*------~.*r::t_'-~-::--_-:*:*o:--*~*"--'--:~The*rrce*nsee should-*sele.ct a worst case* configuration or -

• ., other alternative to demonstrate that. the iinpact load or

• *energy produced*as a-result of postulated pipe break for piping greater than 14 inch diameter does not exceed the load or

. energy required to penetrate the co*nta i n*ment 1 i ner *and wall.

In performing this. evaluation with static analysis or static test~ the dynamic load factor has to be considered.

The licensee can take into account the following considerations:*-

i.

• Actual liner thickness with respect to.the impact location; and ff. The combined crack propagation time and break opening time of the pipe may be long enough to depressurize the system such that the whipping pipe could not produce

. sufficient energy to* penetrate th.e containment wall.*

\\*.

TARGET TECHNOLOGY LTD.

'The effects of postulated break locations in lines greater than 14 inches in diameter nave been reviewed.

Eleven break locations were identified as

.having interactions with the containment liner. Scaled drawings depicting the.movement of the whipping pipe into the containment liner have been prepared.

• The velocity component normal to the liner at impact is in the range of 10 to 236 feet per ~econd for the above eleven interactions.

The lower bound of the normal velocity range results from postulated pipe break locations in lines which.have a relatively small gap initially between the piping and the liner with the result that* the velocity buildup prior tc{*impact is relatively low.

References 3 and 4 present empirical formulations and test results of missile impact on steel plates.

One of the test configurations included a Schedule 40, 12-inch diameter steel pipe weighing 743 lbs. impacting the target panel (3/4 inch thick) end-on at 210 feet per ~econd. In the region of plate impact, the rectangular area unsupported by stiffeners was approximately J.

1-6 11 by 6 1

- l 11.

Although the test configuration appears to be stiffe~ than the free standing drywell liner at Dresden 2, the test target plate displacement was greater than 3 inches.

As the drywe 11 1 i ner at Dresden 2 is backed up by concrete after a 3 inch displacement of the liner, the pipe test results can be consider~d to be an upper bound on 'postulated pipe whip impact on the Dresden 2 liner.

The test velocity for the 12 inch pipe at impact was 210 feet per second.

A review of the normal velocities for the eleven postulated pipe whip/liner

~

interactions inditates that ten of the interactions have velocities 114 feet per second or less. The only interaction which is greater than the -test* velocity

.. of 210 feet per second is for a postulated break location in the feedwater line. The feedwater line appears to make contact with the liner at an 18 11xl2 11

• reducer in the feedwater line., and the impact for this interaction is considered

• . not to be as sev.ere as the 12 inch pipe end-on impact in Reference 4 *

. ~. !.. ~-.:*.. -:-,.:

.,----~.. -:.-~<~::_,'..b*::~..:.:.*The-Ticensee should prqvide the technical bases for Figure*....

• *. 4-1 of Reference* 1 with respect to the energy absorption capacity of containment liner (based:on 80 percent penetration).

• .The modified SRI formula, as presented *in* References 3* & 4;.is used in determining the energy absorption capacity of the containment 1 i ne~~***: Ji!_e "

formula is given below:

AE

.we K

DT2 = 4.128 + o.0967,,-

t0u

. ( Eq *. *7-l) where:

bE = E1 - Er = Kinetic energy* required for performation.

E1 = Initial kinetic energy of the missile.

E = Residual kinetic ~nergy of the missile after penetration r

(0 in our usage).'

Kt= -Target.energy absorption capacity reduction factor with respect to its ductile fracture temperature - 1.0 at room temperature

~.

t *

. ~*.

• TARGET TECHNOLOGY LTD.

r. = Effective crater radius measured from the center of impact l

along one o*f. the four approximately orthogonal directions;.

i - l, 2, 3, 4.

• .* re,= Full effective crater radius, - 3.6 0 if no edge or stiffener

• is less than this distance from center of impact.

~ -

. C = l_ I 3. {4. ~. ( T:) 2}. If: = l. 0 i f T = T 0 T = Actual or calculated thickness for which the *missile is just 0

stopped, i.e., E = D (incipient perforation).

r This.formula was used to calculate-the energy absorption capacity of the containment liner for 80% penetration. A plot of the energy capacity for pipe diameters of 2"-_to 14 11 was presented in.Reference las Figure 4-1.

~:

.. c.

The licensee should clarify the technical bases for Figure

• ., *::.-.,..

• 4. 2.of Reference l and the use of 2500 psi as an upper bound

*... *for jet-impingement loading on the drywell lin.er (page 11,

• -*:... _~-;*-:./.'.::~:.~-~~'ii~~::*...:.~~(:.:~:-;-:-<**,... _ Reference_ l )_~~----- **--

.. *->.-.. : l

~:.

As indicated in R.eference l, Figure 5-1, the work flow for the*pipe,

,..~*rupture evaluation is based on a two tier approach *. The first tier evaluation (Task 4) is based on conservative analytical criteria which are

. used to screen.the large number of postulated break.loca-tions in an efficient manner.

Figures 1 through 4-6 (Reference l) are *inten.ded to *facilitate the accomplishment* of thi~ streening process.

Figures* 4-1 through 4-6 do not represent necessarily the ultimate structural capability of the target.

If

. a target does not pass the Task 4 screening, then the unacceptable interaction is resolved at the second.tier level (Task 6) using more sophisticated.

methods of analysis.

The use of 2500 psi as an upper bound in the nonlinear finite element analysis is based on engineering judgment in order to limit excessive compu-tational expense.: An examination of Figure 4-2 (Reference 1), even fOr a circular loading area equivalent to 20 inches in diameter the curve is already tending toward being asymptotic at 2800 psi. The analysis was performed for circular loading areas as small as 4 inches in diameter in order to cover a full spectrum of target areas. The 2500 psi calculational limit does not imply that actual jet impingement pressures are limited to this value.

\\,,.

. -.. ~::r.

• TARGET TECHNOLOGY LTD.

The mathematical model (shown in Fig. 7-1) represents a segment of

• the spherical portion of the containment liner. The center of the loading

'. are~ is located at the center of the plate. The edges are assumed to be fixed.

The dimensions of the model are chosen such that the boundaries are sufficiently far away from the edge of the loading area. Based on small deflection theory, Reference 5 gives the following formula for calculating the minimum distance of the boundary from the edge of the load, for neglecting the boundary conditions.

a = R Sin-l. (1.65~)

{Eq. 7-2) where *

.R = Radius of curvature of the spherical shell t = thickness of the shell to~* R.~ 396" and t = 3/4",

a= 28.46 11

,.;l;

. for boundary condition effects to be sma 11..

.. '.~*...

The value of a as calculated from Equation 7-2 is used to determine the size of the generic mod~l.

For the loading areas corresponding to 4 11, 12", 24" and 36" diameters considered here, the dimensions of the plate used in the finite element

' model are as follows:

Loading area diameter

~--,*,.~-~,:,:;;,~-*-.,.:..,~.:.* ~.-.-.

'-*-'-*.~.*,.,..,-.. -. __

..._( 1_* n_c_h_es_,* ):;....** __ _

Siz~ of the model

( l : iii x l 'iii) '

4 12 '

24 36

. ~

72 x 12=*~

96 x 96 '

144 x 144 144 x l44 *.

Since the structure, the loading~ *and the boundary conditions are symmetrical about both x-axis and y-axis (Figure 7-1), symmetrical distribution of the stresses and deflections is expected about x and y-axes. Hence, for the ANSYS finite element analysis, only one-quarter portion of the model *

• located in the first quadrant is considered.

The following boundary *conditions are assumed in the ANSYS model:

o The displacement parallel to y-axis, i.e., UY is zero along the boundary y = 0.

o *The slope, g = au2 is zero at the boundary, y = 0.

x ay

-~.

... T

• ,/....... TARGET TECHNOLOGY LTD.

-- A T 1_~-.. i:,..

~

T*l*-*---

1 y

I T...

• . i J

*.* ~* *...,,

i.

.. ~-. '... '.

I"

-~----~.

• • -:~

• _'.. ~

1

• 1,*

• -.......... *.**. -.. ** x T; * -

Temperature outside *;mpingem_e~~ ~~~a

-~--:.4*. :, ~

c*. T0. =. Temperature outs_ide drywell,. *.

P = Pressure FIGURE 7-l.

MATHEMATICAL MODEL OF THE CONTAINMENT LINER -

EVALUATION OF JET IMPINGEMENT i'FFECTS. -...

!°-

• • .* TARGET TECHNOLOGY LTD.

0-The displacement parallel to x-axis, Ux is zero-along the

_boundary x = 0.

slope, Q = auz is zero along x = 0.

0 The y

a x 0

The liner is fixed at the remaining two boundaries.

The plastic triangle shell el~ment (STIF 48) in the ANSYS element library has been used in the finite element model of the liner.

By using this element, both the membrane stiffness and the bending stiffness in the liner are considered in the analysis. In addition, this element is suitable for.

analyzing the structure in the plastic domain.

- The foilowing loading conditions on the liner were considered in the

- anaiysis:

A.

Thermal Loads: -

In the jet impingement *area, the temperature of the line~ surface is 575°F.

Outside the impingement area, the liner surface is at l650F.

The temperature on the outside surface of the drywell is lQQOF.

B.

Pressur~ Loading:

_ A uniform pressure loading is applied in the jet impingement area.

The magnitude of the pressure is gradually increased in steps until either

_,)~~(- -

_;,-- ~~~e~r~~s~~~u~~;~~~~}.,~?O __ ps~ (calculational limit), or the deflection of the

• .:.;~" -':*. ;

. ~....... "'..'

---\\:r *--_-* _

• 'From ANSYS computer runs,-the maximum allowable pressure loadings

- -- on the liner for 4" ~

• 12H, 24" and 36".diameter loading areas were determined.

• For loading areas corresponding to other diameters, the allowable pressures were computed by interpolation.

,.* --~*. '

• ",. *r

. ;' i

d. - - The licensee should pro vi d-e the deta i 1 ed met,hodo logy including basic assumptions used in arriving at screening criteria for RPV pedestal and biological shield wall, i :e.-, the allowable pipe whip loads and maximum allowable jet impingement pressure,

-for postulated pipe break interactions with RPV pedestal and * -

biological shield wall (Figures 4-3 and 4-4, Reference 1).

The methodology used in arriving at evaluation criteria for postulated pipe break interactions with the RPV pedestal is explained below.

The

- criteria is basically intended to be in the form of curves relating the maximum static equivalent whip loads and jet impingement pressures to the various pipe diameters expected.

~ __ _

. -:: *, ~ -..

TARGET TECHNOLOGY LTD.

Various factors were considered in determining the location of the

.. load.

The horizontal load was applied on the outer surface of the pedestal

~. at the location of the haunch in order to include the effects of geometrical discontinuity as well as to be conservative in most cases for overturning

• stability considerations. Three different loading diameters were considered, viz. 36"0, 24"0, 12"0, along with vertical loads from the Biological Shield Wall and the Reactor Pressure Vessel.

I In conformance with the requirements for an initial screening criteria the fo]lowing conservative assumptions were made:

o All impulsive ~nd impactive loads can be equated to an equivalent static fcirce and the transient nature of the force does not result in adverse dynamic effects.

• o : Due to the *short duration of the jet impingement load the transient temperature effects on concrete can be neglected *.

~*-

o Pipe diameters less than 2~"0 will not be considered to affect*

the RPV pedestal.

Bending stresses were based on the requirements of Chapter 10 of the ACI Code (Ref. 6). The pedestal wall was analyzed in.both the hoop and meridional directions.

Balanced section conditions were determined using the following equation (Ref. 7).:

85 f I) c

...,.. +'A*' (f -.85 fc')(d - d' d") +A f.d"

• *s y

.

• s Y

~.:., -.-. ---

'f.

• • ')'

TARGET TECHNOLOGY LTD.

,...., r

.. ~... :

~:: *~.

~

• 1

. where:*

.... Pb: Mb * -

balanced section axial load and bending capacities

'*A s A I s

d b

f *I c

..' fy.

B.l.

= area of tension steel

= area of compression steel

= section depth

= section width compressive stre~gth of concrete'.

= yield ~trength of.~steel.

= ".85 t',.

.. Plastic Centroid T

IA s

b.*.

I.

1. '. ".

c* _,...*

• L-d*i*~..

e

..J ~d'.

0c----* *d __ _.,..L

---h -----~"""* *.

xb e'

87000d..

= f y + 87000'

= e.c.centri city of axial load rest of the terms are shown in L

e '---.. -. -.. -. --~,,, -:.

and the the sketch.*

For a section whos~ capacity is controlled by compression the follow-ing equation "'as used to evaluate the axial load capacity:,

• ~.{':,_.

,\\*.:.;.

. p *.: *=.. bhf. *;(*3he * + *3(d - d' }h) +

A.,.'~ It~

+,.~*.S) n... --

c T-. :"

2d 2 s. y

. d-d

~-

. ::\\.. ~-

• ',...../.'

  {*.- I; :.

,.. I*~...... :.

' **. _,.- ' 'J_.* '..... *:-

'* : \\. -;.,:

... * * ;. ~

-4~i ~

__ ':""" __.. -:... *...;.~

• ~,,.. :*/:...***

• • ~*

• ..,: ~*

... '. ).::/**:~;*'. *.*!* :: :-*,.*.

• .*}..

.**(,...

.1~

~*: *~

For*~ section wh~se ~~apacity. is controll.ed by tension the following

• equation was.. used to evaluate the axial* load capacity:*

= o. aS ;

• bd {-p + 1 - ~

Pn

. I

. c d

+ ~*1)

-Jo. - ~)2 + 2P [(m-1) (1 d'

+

- er>

. d where Pn = nominal ax.ial load capacity p

= As/bd and m = f /.85 f

• y c

j.

• TARGET TECHNOLOGY LTD.

--Shear~stren-gth was based on the requirements of Chapter 11 of ACI Code.

. :Stresses were conservatively considered at a section a distance less than

~ * 'd'.from the face of the load or reaction, where 'd' i~ the distance from

• .*the extreme compression fibre to the centroid of the tension steel. For sections urider*axial compression (hoop or meridional) the following equation was used to determine shear strength:

.... *~.

where.

Ve = ~-9 f

I + 2500 c

Mm = M Nu(4h - d)

.u 8

v d~

PW__!!..._

b d M

• w m

\\

. :....

• V~ *=*.Nominal shear'_ strength prov~ded by concr~t(_._.-.-~.* -~;, :\\: -.*..

• _

~

~ ;*1 -., -

-*~A 1* bd... :

___ ~.. _

... ~;~*. ---~:*.**, _*

~--.. *._-_.*.*

• • _-_,_*.-_-__~-~.. -_;: __ :~~_'._".-,.. -.~:_'_:_-:.. _* ___ --_----_.'_.. _*>~;: __.~:~_.-:~

~_;*.~.:,..-.-... ~-::.-.. ~::.. -;.:: *:.. ~:*,1:\\1<*d:'.,::*.. _-:.. :-*,..

_.,J.

PW=.. s.... -~-~...:-:--_~ -

_..: *,:'.':<.. _::.. **:_'.~~<_:;~~~>->AJ-2 :~::.p"*:: ;'*.

.-. vu =.. Facto~ed_* ~s~~ar for~~e" *at.: ~-~*c_t~ ~--~ _ \\ *

.._ "* *:.. >~* *.,,/~-:. ~j-:::*:'

t -

b = b = section width.... _ *

~-

'".* ~ "

-~ ;iij w

". *,,\\..

,.,~

M

. u and, N u

= moment corresponding to V

• u

= Fact?;e~ ~x_.i.al* l~ad at section. (+ve *:for -~~mpre~~io~ -~e ~:for

- tens 1 on) -.

\\ - * *..

L. -*-

For cases where ~ was negative the fol ~owing equation was used to - ; *

• determine V :

i

. c i -

' :*. ' j ~-

.-" *.~

• : ** -~

V c = 3.'s £'.. ~wd Y._

• • _t_./_.s_,:?Ag _', '.' r

,,';'.?'.~.*--~.~<<... ; ; :

where A = gross concrete area g

. *... ~ -~

,.. ~.. :.. : ~

i* *t '*

! ".~-

i

'I*

'(*

• ments using I..

• Punching shear evaluation was also based on the r~~uire*- *<":.

of Chapter 11 of ACI Code.

The allowable load was calculated the following *formula:

- ----, I.

-v11 __ _

_;J';. -

~*.

t d +d 1

_J

-I I

~ ~

~.-.~*

. ~..

-"~

-. -~*..

... *'" TARGET TECHNOLOGY LTD.

r,

Pn:.~ 4 {fc' * * {1T(d1 + d)d}

. P = ~omi~al horizontal load

• * *-~ whete n

• .d1 ='diameter of loaded area

• and d = depth of concrete section Overturning stability was.based on treating the pedestal as a hollow

. cylinder. A static analysis was perfonned to determine the maximum load that the pedestal cross section could allow before developing tension.

• ** tracked concrete section properties were computed for various cross-sections of the pedestal in both the hoop and meridional directions~

• These properties were utilized to determine equivalent Young's moduli in these

' "direct1"ons,.*.. :':* :-"*** :.... **

~.. " * **:

~.

. ~*: '..

~.... *.

The RPV p*edest~l.: ~as represented mathematically as an el~stic shell.':

... ** *. An ANSYS computer model using Element (STIF 25) was developed.

The full.

. Pedestal height was~required in ~odelling based on the calculation for decay length from the following equation (Ref. 8):

. ~ *. ~ [3(1. ~*~~.sYsxl !:]-**

i

~ere

lf.{. :.......... Lc :**~:.-/: ~~q~:i:~ed deca~, ~l~.n~th

. -,\\~{*~.. **......

~ '-:.:

a. =. *radius of cylinder... ';:, *; '.

<.~< :,.* *:.: ;:~_\\_:~~. }'/~:-~"!.~'.:?::/~\\:,~t:.. ~ ":''.'\\/. ',. c.

• ' :~* * >;

~

• -::**V:'.!*'**:.\\:.:-:.*..,.*:_;_*

h- *.=<thickness of wall

• ........... ~~- i*~/5.. ~:-*,,*..,_,_-:**..... t ':~ *. :.

l :::

~.. ~

,'\\

~

...,".. *.. - :.*-..... :<*Y~s*~ Ys~. -

• poi.sson*s ratio in meridional and hooi>>directions L

. c

= Young 1 s Modulus* in. meridional and hoop direct ions:

Horizontal loads were applied on t.hese models in the form of a harmonic se~ies of the form:

where

-0 f{e) a L {ancos ne + b sin ne) o n+l n

a 1 Jn f{e) de 21T 0

-1T 1 Jn f ( e.) cos nede a

=

n Tr Tr b

= 0 for an even function n

~

.'.,1

~

\\,..

I

\\,...

'..., TARGET TECHNOLOGY LTD.

Th~ analytic~l result for the effects of pipe whip and je~ impingement

.on the RPV pedestal were summarized and presented as Figures 4-3 and 4-4

~ *. in Reference 1.

The biological shield wall's structural response to pipe whip and jet impingement loads were* evaluated using finite elemerit analysis. The magnitude of the applied loading corresponded to the range of expected pipe diameters

• or jet impingement target areas.

• In conformance with the requirements for an initial screening criteria

• the fo_llowing conservative assumptions are made:

~., ** -

.. ~

• I'. : *

• o

~ ':.

All impulsive and impactive loads can be equated to an equivalent static force.

o. Due to the short.*duration of the Jet Impingement,. onl,y the loaded

• .* "area experiences. a thermal load,. and variations *of temperature

through thickness and along the surface can be neglected *

~

• l., ~

o Shielding concrete is capable of t~ansm~tting cbmpressive loads from the 1 oaded face to the rear face. * * -.

The shield wall was modelled as two thin cylindrical *shells connected by axial springs which represented the shielding concrete. It was assumed that the concret_e was not capable of transmitting vertical shears between the two plates and hence the choice Qf a spring-gap element.

.J

-~(:

The ANsvs**elements* chosen.*to mcid~l the shield wall ~re shown

". * *\\:.-..

. schematically infigure.7-2. The-elements.were chosen from-the ANSYS element

• ~":i.:W~-;t:*'.:

-:'.library.and-~ list of,elements,along with their salient features is given in 1*.**-.-

?;

. \\_-_:,:~~~-ab~~~-~!::::;:~;<~_:.. :*~:~,~~~.':"'*~?~-:~~-.w~-.

• _>* -.-*~* *

• ..,. ::. * :* *--Evaluations*.:were.... based *on the more conservative of :the following

• .. criteria:>

. =-- "---

~:

..... *~*-.......

• . *o )'An average deflection under the -loaded area of 4"._;

--~---~.. --.. :*_....:, _-.-_-*_

(2) A maximum strain of up to 50 percent of ultimate strain. *.

• An examination of the results indicated that the strains under applied loads were much lower than the limitation, and the deflection criteria governed in all cases.* Overall stability computations were performed to determine the capacity of anchoring mechanisms at the bases into the RPV Pedestal.

The-a~a1ytica1 results. for the effects of pipe whip and jet impingement on *the sacrificial shield wall were summarized and presented as Figures 4-5 and 4-6 in Reference 1.

• These figures are used in screening interactions with the sacrificial shield wall as part of the.Task 4 activity.

~ '

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f;,

1.*

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-*"'-; TARGET TECHNOLOGY LTD.

FIGURE 7-2.

SCHEMATIC SKETCH OF ANSYS ELEMENTS

~

-~ :.. : :

~

• ~ (.

~

I

-~.., *:

~"*:. ; ~

i. * *. '*

I

.,*:_:~; :.. :*:_>;. ~.*.* <_.* ~*.. -

. ~.

~:

~

' *~*~*-

• _-**.~-- :---*--.

TABLE 7-1 *. ANSYS ELEMENTS FOR SHIELD WALL MODELLING ELEMENT NO.

ANSYS ELEMENT NO.

' DESCRIPTION ANSYS FEATURES 2

'STIF 48 l/4n plate, front

& rear 1/4" plate, front

& rear Rectangular Shell Element.

Capabilities in the Elastic range of ~terial properties only. Six DOF's at each node.

Triangular Shell Element.

Permits properties in the Plastic range.

Six DOF's at each node. *This element enables the use-of nonlinear fsotrooic material

• 3

-~~--sTIF 43: ** -

Flange of-W27xl77 See Element No. 1 4

STIF 40 Concrete fn compression only Combination element with a gap. This element enables the use of only compression loading with no shear transfer, for modeling the concrete fill.

'I

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. ~ - *-

• ~

j

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• . TARGET TECHNOLOGY LTD.

. e

• s.8 In-considering the damage criteria (Section 4.5 of Reference l),

.... the l'icensee has used the assumption that° a jet or whipping pipe

• .. is considered to inflict no damage on other pipes of equal or

-~reater sfze and equal or greater thickness.

It is the staff's

• position' (Reference 7) that the effects of jet impingement should

.. be considered and evaluated regardless of the ratio bf impinged and postulated broken pipe sizes.

The jet thrust force acting on the end of a whipping pipe may be represEmted by a steady state function if a static model is used in the subsequent pipe motion analysis.

• The function should have a magnitude not less than '

T =. KpA. *;..

( Eq. 8-1)

W.~'.~~t:,.*~;2f ~:%:.:-_;~:; * :>., {.

• i ***** **.. *.*.

_.*~:*:. :* ::::./*:**.'.'. *..

~:*<,* p :=:system press*ure prior* to pipe break t',,,. _

-~*,*,... !>

• \\:<'*:.~,-.. P*~ :*~.

~.~--

,'~-.-

• -.*~

.. *~*..

• \\,,#:

.,"'

~-_~:

.. ~

.. : A = pipe break area*.*, *.**

_, *-~*

.,...... K ;*th~~~t co~fficient.

J"

• • 1

(...

Fo~ the case*of a ruptured pipe that is iriitially in ~ontact with the

.t

.

• target pipe, the equivalent *static force on _the tar_get pipe can be conservati-vely

• .. ~*

represented by...

~*_

~~

It

-~; *

~

F..._. =.(2~0)** (KA)

(Eq~ 8-2)

.... ':'_~;,~~z~*;.. : * *.\\L.-:..

.. __ : _ e;_." * *_..

p

, * -,~:

• ~:"IE{\\~'.-:;_.-*.*-::*~':'~~where the ~ynamic:Jo_ad_factor is conservatively selected as_2..:.0._.

.,~:

i.

':.::: *:_-., :*--~~>--~::~;~r.:;:*:,~~~-~j];~:i;:;t~Ei:~,fj:;-r:;-~:'.~:~;~~;~~~~. for~~:*. ~~a~n'.~t~*ng.'*f ro~

.. -*t~:~.-e~d ~f a brok~n; pipe can -..,*:*

_. *.. ".... _-:be _also _cons~ryatively represented by Equation 8-1.

• The equivalent static.

• ~.. * *.. * *.

~* * "* force on the*"* target __ pipe as a result of jet impingement can. a 1 so be con- *

".' * ~' *. - :servatively*_ r~presented by Equation 8-2...

~

... :***:.**.**~*...::*:*_::_.:;:-.~

• • ~~:*==::.--:.~*-.*7'**.--

'*~ -

.. ~*-*

.. - It can be concluded therefore that the equi~valent static force on -_

.the target pipe resulting_ from either pipe whip effects or jet.-impingement effects is of the same magnitude for the above case *. Consider next, the case of a ruptured pipe that is separated by a gap from the target pipe.

The jet thrust forte will be acting on the whipping pipe as in the first case.

However, because the whipping pipe is being accelerated through a gap prior to contact with the target pipe, an inertia force component will also

--. be present.

The equivalent static force due to pipe whip in the presence

• . :bf a gap can be expressed as

..: : ~..*.

.F

= (2.0) (KpA + Inertia F6rce Component)

. eq.

(Eq. 8-3) where a dynamic load factor of 2.0 is assumed.

• . TARGET TECHNOLOGY LTD.

• .r:

The NRC position as stated in Standard*Review Plan 3.6.2 is that an unrestrained whippirig pipe will not cause unacceptable damage in impacted pipes of the same or greater nominal pipe size and with the same or greater

. wall thicknesses.

On the basis of the results of Equations 8-2 and 8-3 which indicate that the equivalent static force from pipe whip is equ.al to or greater than the equivalent static force from jet impingement, it is concluded that

.*:.'the' same rule which is applicable to pipe whip should also be. applicable to

• ~* *, jet impingement _considerations.

.. ~.;: : *'; ~-~-~>**.. \\-:_ __ ~.._**

.... <.:*. *~-,~

• ."*:,*.::~.<..~~-:.!;,:~:.

• l.

\\

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.~Target pipe *interactions-fr.om pipe whip or *jet impingemen~. ar~ _evaluated

,_*_,,~.

using Equation 4-3 {Reference.l )_if the.reJationships

,

• dT.. ;*_<l~:~nd fr *;*~~~"_;,-*:*-* _.*,.*. *-*' :-. -~~:*-:.. ~_.:... _-.. :... :. *.

-~

'* :-* ~.. '**,_ ;*, -...-:...

~

-**where:._.*.... J... :;

r\\*.~.. -.... ~..

~:'.'.*:

d *.. = diameter: of target pipe

• d~ ~ diameter.of pipe with postulated break location

., t

. = "wall thickness of target pipe

,-. -~ -~ wal_l thic_k,n~ss <?f. pipe with, postula_ted break location*

are not satisfied -*

• • .. \\' :-~-<~:~.. t-

• -J

.:l;

-~-=--~-

• ~

>r*

• ,<**y*.,;*.e.9*1n determining the acceptability of target pipe(Section 4.3.2

• _,}:k *j'*:..,~-:~~-?l-:;-~*>.. ~*/***. of* Reference 1), the licensee has used a criterion that the

.,..,-;:*~§**;

• • '~c~.},.~-:r:~.:::'*:<::');:~-';.-limiting factor for an applied equivalent static-load is that the

_.*.<:.;_*:*~* ".<,:°:"*"'*/~c:t*.';":::~:;.:;. *.-_:resulting.strain.. in the. target pipe material does noLexceed

>:~:::_:;:::;::,:.:-.;'*.. 45.~.perce_n~.of :the minimum ultimate.*uniform.strain *of the*material

'.*~~::*..,~,_',.,'..~*:_;;:-;;;:at*~h~~appropr.i~te t~mperature~-~Thi~ crJteria i~-~cceptable for

~*.*avoiding cascading*pipe_breaks~~-However,*.some piping systems

'... * ~-_-.. *:*._-.;;.,.., ar.e_.. required:*to.*deliver:*certain~*rated.Jlow and should be designed

• * :**.-_:~-*_.. to *retain-dimensional --stability *when,stressed to the allowable.**:.

. : *~limits *associated with the emergency and faulted conditions, i.e.~

. *.. the functionaJ. capabil~ty pf.the piping is required to be demon-

• strated.

The licensee should provide justification *to assure that.

the target piping ~ill remain functional as a result of jet *.*-

impingement and pipe whip inter~ctions.

~

Plastic hinge formation of the target pipe is of a very localized nature

_ and the zone of plasticity is limited essentially to the hinge location.

It is therefore possible to achieve strain levels approaching 45 percent

/of the minimum uniform ultinJate strain of the material in a 'localized region without affecting the overall deformation or functionality of the target pipe.

• A parametrif ~ tudy covering a range of geometric and 1 oad parameters

. was performed using the ANSYS finite element program.

The nonlinear dynamic analysis results indicated the coexistence of large localized strain levels and small global deformations.

The above conclusion is illustrated by the following numerical results from the ANSYS computer program.

! ~

't,.

J...

• TARGET TECHNOLOGY LTD.

.. ~...

~

~..

Target pipe properties used were as follows:

Pipe = 16 inch diameter - Schedule 40 Wall Thickness= 0.5 inches a y = 3_5, 000 psi t '

~: -~, *.

' ** r

~

The-.plil:stic hing~.*wh1.ch. formed *at poir1t.A (point' ~-f :*load application).

. reached a* strain level. of 45 percent of. the minimum uniform ultimate strain

..._,:*,;.*of. the material.:-.. The downward displacement of point"A was.1.643 inches with

_.. _.,_*. an angle of rotation at.the support of 0.78 degrees.*.... :._*.

• r

~

~... ~ *;

'f It should be* noted that Section 4.3.2 *(Reference 1) was develo.ped *a:s a conservative screening criteria for application in the Task 4 activity.

~-.Interactions which are determined not to satisfy this consetvative criteria

.are evaluated in Task 6 using sophisticated analytical methods as appropriate

. on a case-by-case basis.

B. 10 The licensee's approach for.the alternative safety assessment for selected high energy pipe break locations using fracture mechanics analysis is not completely consistent with the staff

• -guidance-on the subject as described in Appendix 1 to Attachment to Enclosure 2. * :For example, ~the licensee did not address the detectabi 1 i ty requirements *.* :. The staff recommends that the

• iicensee consider th~staff guidance as pro~ided* in Enclosure*

2 *for resolution. of. µnresol ved.interacti ans*.. __ :.'."

• The staff. guid~n~~'-fo~:.t.he. *~f~~-/nJ"t~-~*~--~-~fe~;:;~~"~~~~~,-5~~nt of.high energy pipe break locations using fracture.mechanics analysis is.based onsatisfying the requirements for detectability, integrity and consideration of extreme loading conditions.*" The approach proposed by CECo for satisfying the integrity..

and extreme loading condition requirements reflects the guidance*provided.

. in Reference 2 (Appendix 1. to Attachment to Enclosure 2).

f' CECo's approach for satisfying the detectability requirement is based on the 1 eak-before-break concept and consists of the f o 11 owing.steps :

l.

• The initial crack size is based on a.Code allowable surface defect.

2.

Crack growth is based on a fatigue mechanism.

3.

The end-of-life crack size reflects the growth potential of the*

initial crack under expected operating conditions.

I

~,.

.. ~**-

TARGET TECHNOLOGY LTD.

,.~.... :

~

,.,.,._, **,j,.

.. :,~~"*\\I _..*:*:

4.

-*~The erid-of-life crack size is.compared to the critical crack

-length in order to establish the margin of safety.

5.

If the end-of-life crack becomes a through-th~-wall cr~ck~. then the leakage for _this crack l~ngth is calculated.

~::.. *;...-.

6.

Calculate th~ leakage from a* thro'ugh-the-wall crack.which *is of critical length and establish the margin of safety on leakage from the critical length crack as ~ompared to the leakage from the end-of-life crack.

. 7.

For the specific postulated.break location, detennine what the current capability to detect leakage is and compare this. capability*

• . to the leakage from the critical -1 ength crack.

Provide_ additional

• leakage* detection capability as required_~to ensure that the

... margin of* safety.Pn leakage.detection i_s greater than *100 percent.*

. *,*, ;:'.:** :.*** );':;;;~,1f ~~', *4* ~'.'..;T**{r*; z*:~r:}*:f ?;*~~~(:~~~~~.-.**..

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• 1.

REFERENCES

.Lett~~ from*T.J. Rausch {ctco) to D.M. Crutchfield (NRC), dated June 4, 1982, Attachment 1 - Report, "Dresden 2 Nuclear Power Station SEP Topic III-5.A, High Energy Pipe Break Inside Containment Interim

'Progress Repor.t," dated May.18, 1982. *

~

2.

Letter from D.M. Crutchfield (NRC) to L. DelGeorge (CECo), dated June 29, 1982, Enclosure 1, "SEP Draft Evaluation of Effects of Pipe Break on Structures, Systems and Components Inside Containment Topic III-5.A Dresden.2 Nuclear Power Station."

3.

"Report of 'the ASCE Committee on Impact.ive and.*impulsive Loads" -

Civil Engineering and Nuclear Power, Volume V, September, 1980.

4. -:-:_" _:. ;,.;p*e-c-i'a i /~~T~~~::~,~*i*:~~*~'.~~;~~~:d*>:f~~ _ -~h~- ~esig~ and~--kn'~i*Y*~~i ~ * ~f Floating

... *-"Nuclear Plant _Containment Structures," Tsai, J.c:, Orr, R.S.,

5.

6.

, *Transactions of the 4th International Conference on Structural Mechanics in Reactor Technology, Vol. J(a), August 19, 1977..

Roark, R.J., and Young, W.C., Formulas for Stress and~_Strain, 5th*

. Editiorn,. McGraw-Hill, 1975..

"Code Requirements for _N,uclear Safety Related Concrete Structures-,"

ACI 349-80 *.

,-.~;

, (

• '.. ~..

'.,~ *

• ,::.~/{f.. -..... _,:* i~ _ *salmon.and Wang-~* Reinforced Concrete Design, In text.* Press., 1973. *

-~:J

- 8. :., **:-~r~us*~....-H~,:;:rti_in:E1~~~i~:*:**.she1is~.-~ohn Wi.ley~-June*,-~*1961.:~_*._... ~:* _*

°"'~.

4'ti;if~:;f *_: ' ;_ ' ;;:; :

-* :. --. .<:'. / ' ; /':'.;t ~/-'.; -~-* '.~ ' _:::.. -; ~ '

~,

*:~:-~i... *:1...... :::-:*:.*. -..

.. ~

• ~~**.. ~.. ~~~:*::.:;-..

.,,* ;."' ~.

~. J

~:

• , _,*~J.:-o '.,... r.:..

• • ~ '. ~

.~..

.,.,.. ~

• 1....

"{

-~~. ~~*~...

• ~. '.***

.. '.*.... -.-1