ML20064K078

Impure Water in Steam Generators & Isolation Generators, Informal Rept for Limited Distribution

ML20064K078
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Issue date:	06/30/1980
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BNL-NUREG-281C INFORMAL REPOR7 LIMITED DISTRIBUTION g]'

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IIPURE WATER IN STEAM GENERATORS l

AND ISOLATION GENERATORS I.

4h Daniel van Rooyen and Martin W. Kendig 9

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1. l June 1980 Corrosion Science Group Department of Nuclear Energy Brookhaven National Lateratory k'

Uoton, New York 11973 Y

NOTICE:

This document antains oreliminary information and was precared crimarily for interim use.

Since it may be subject to revision or correction and does not represent a final report, it should not be cited as reference witnout the expressed consent of the author, s

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1.g TABLE OF CONTENTS Fage 1

SUMMAR1...........................................................

2 ST AT EtiENT O F P R0B L EH.....................................................

3 CHLORIDE STRESS CORROSION CRACKING........................................

5 CAUSTIC CRACKING..........................................................

6 Local Boiling. Chemical Reactions, Species in Solution..................

8 Rates of SCC of SS and Inconel 600 in Caustic...........................

CRACKING OF INCONEL AND SS IN RELATIVELY PURE WATER WITH A SMALL 10 AMO UNT O F O XY GEN P RE S ENT................................................

12 R E FE R E N C E S................................................................

13 FIGURE 1..................................................................

la TABLE 1...................................................................

I n..-)

A-1 APPENJIX A................................................................

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9 i

l 1

If1 PURE WATER IN STEAt1 GENERATORS AND ISOLATION GENERATORS

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Daniel van Rooyen and i'artin U. Kendig Corrosion Science Group Department of !:uclear Energy Brookhaven National Laboratory Upton, ?'ew York 11973 SU' WAD.Y 1.

Stress corrosion cracking (SCC) can occur in stainless steel (SS) and Inconel 600, but they do not behave in the same way.

• conel 500 is less crone to C.

SS is prone to SCC in Cl~ as well as 'laCH.

n SCC in NaOH, and nomally resists SCC in Cl".

3.

Innure water ingress into PWR steam generators or SWR isolation condensers is discussed in terms of Cl

- cracking and aOH crackino, takina into account the kinetics of chemical chances, concentration changes and SCC.

I Changes in chemistry are relatively racid.

is cresent. The cH croo

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d.

C1' cracking of SS can occur at icw art or if Og in the use of sea water is believed to be less imoortant than the cresence o# 0-2 5.

t!aOH cracking is a greater likelihood in SS than in Inconel, althouen both naterials are suscestible.

6.

Operation at temperature for up to a week with incure water may lead to SCC of the tubes by Cl or fla0H.

7.

Elinination of 0 will reduce the chances of Cl SCC of SS, :laOH cracking 2

of Inconel, or cure water cracking of sensiti::ec 35.

3.

Silica may hold cotential as an 'ncredient 10 sur: cress caustic for-ation due to concentration effects in alkaline incure waters.

3.

• Mrinn the temoerature as cuickiv as cossible wculd aise be bene #icial in a stean generator 41th Inconel 600 tu:es and a caustic-forning environrent.

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bN STATEMENT OF PROBLEM V)

A meetino was held in late June 1979 in Bethesda to discuss the matter of

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imoure water that may be introduced into PWR steam generators or BNP. isolation fu ;

J. R. Weeks and D. van Rooyen reoresented SNL.

It was said that

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condensers.

new plants are or will be recuired to have a 36-hour sucoly of feedwater avail-

!j able in case of emergency. Also, such new plants are being designed to be

f cacaole of reaching cold shutdown within a ceriod of 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

In older olants.

there are no such rules for suoplies of feedwater to be available, and if it 9tcomes exnausted for scre reascn then the olant woulc have to use an impure source for emergency cooling under cold shutdown is c'eacned.

Some of these plants

..g 5l*<j a'y only have a 30 minute suopiv of oure water on hand.

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Of major concern to the FRC is the possibility that stress corrosion crack-j ing (SCC) will occur. Tube materials are tycically stainless steel (55) or f

In:cnei 600, and both of these materials under certain conditions are subject 7.

l to SCC. The nest likely icoure water that would find entrv in steam generators v.1 Cj or isolation condensers would be sea water, lake water, river water cc water g.t ;i fecm a nunicipal sucoly.

n the case of sea water, the DH of the resultinn solu-

.. O) tior will droo and chloride can conceritrate in crevices or at areas of local y.. u 4 j toiling.

EMantially, three problems are associated with cnloride entry, i.e., those p..,)

of SCC, accelerated corrosion of carbon steel and cittinc. Of these, only the 7j racking of SS in chlorides is addressed in the sect on on sea water because 4

~.4 cittinn and denting are not forms of corrosion associated witn safety cuestions in the time ceriod of about one week.

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g Fresh water, from which carbon dioxide :0uid te excelled, ff introduced into a stear cenerator or isolation condenser, is usually excected to show a oH rise,

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~'e :P can also rise as a resu't j.y so tNat caustii: cracking may becore a oroblen.

of tne reaction of lla salts in the innure water #th existing oxides or hydroxide!

w ARJ in the tyster, givino free *:aCF.

In this case, both Inconel 500 and 55 are knewr

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tify.,

to underco SCC.

Eiver water er other sources :# #resq wate# ve known tc con-j.$

tain sodium salts, and therefore, the ratter of caustic crackinc will te dis-

>:ussed in this section, includir; both of these alloys.

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1 The cuestions that were raised by NRC for Brookhaven to look into concern In other words, how long can a certain impure water O

mainly the matter of time.

An additional

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be tolerated in the components that have been centioned above?

question concerns the possibility of additions or other steps that could be taken to reduce or mitigate the effects of the impure water on tube integrity.

l It was agreed that the Brookhaven review would consider a period of approx-imately one week,which would cover temperatures from operating temperature down i

In practice, a substantial portion of this time period would to cold shutdown.

involve coilinq and steaning while orderly emergency procedures and repairs are NRC felt that one week would be a 'easonable basis for the cresent carried out.

analysis.

CHLORIDE STRESS CORROSION CRACKING Chloride cracking is considered a potential problem for SS out not for The crackinc of SS in Inconel 600 tubing, which has a hich nickel content.

chlorides depends both on the chloride concentration, the DP of the solution, and the electrochemical potential. The higner the potential' the less chloride When is usually reouired for crackina to start, and the opecsite is also true.

g Cl" is introduced, the pH can be lowered in local recions such as crevices.

Er this to happen, local corrosion is needed.

The latter is stimulated by

,e oxidizing species. The pH droo will affect SCC, but since the oxidizinc scecies will do the same, we emphasize the oxidi:ing aspect in this discussion.

A curve showing the relationshio between chloride concentration and oxygen con-and is included in Fig. I with other centration was developed many years ago data taken from a recent naper by Gordon.III)

Subsecuent work by R. L. Jones has extended the knowledge about the effect of electrochemical potential, using solutions with.1 N Nacl (which is eouivalent to about 0.5", MaCl or 0.36", Cl")

l and tests which were made at C90 C.

No SCC was 'ound in 30-hour tests without t

High oxygen concentrations give rise to hich electrochemical cotentials, so that the clot of chloride versus oxynen concentration is the sare in princiole l

l The e'#ects of 09 per se can as cnloride versus electrochemical potential 4t the sare value by elTctronic

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di#fer from that of controlling the potentia a':caratus, as shown by ?.osbor: and Rosenaren 31 for sensitized SS in cure water.

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any apolied electrochemical potential, in tests done in an atmosphere of helium, a

Q As the potential was increased, using electrochemical h

1.e., no oxygen present.

instruments, SCC was observed to take place in about +1000 mV on the hydrogen This is ouite a high ootential, corresponding to an oxygen concentra-scale.

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tion well in excess of that in feedwater in contact with air.

Cracks start from yfj pits under these conditions and some additional work showed that when the in-

' hj strueents were switched off after pitting had started, in order to lower the potential, then no cracks penetrated the material.

This suagests that even if ilh cnlorice and oxynen are present 'or a time long enour *o start pittinq, SCC may Tire is obviously still not be serious if the oxygen is renoved soon encugh.

g[g cr'tical in this regard, but at any star;e the renoval of 02 will reduce the A coint of uncertainty rerains, since it is not established cnances of SCC.

whether an existing crack will qrow or would be arrested in the absence of 0 '

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Recent data also indicate that there is an absence of crackinc in C-rings (q

stressed above the yield point exoosed to solutions at 600 F with low 0,, and 0

i,)h These tests indicated only an extremely slight arount of inter-J hign chloride.

The oxygen granular cenetration, wnich was not tyoical of SCC in sensiti:ed 55.

pM g.q) was somewnere below 200 ppb, which was the maxinum level in the starting solu-v< ;

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tion; unfortunately the effluent frequently contained :ero or much less oxygen

. nan was introduced. Consequently, the tests can only be considered to have y;

oeen oxygenated to tne maximum of 200 opb, and under various (most?) time cer-M iods probably contained no oxynen at all. The test does reinforce the conclusion y

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• nougn that renoval of oxynen or keeping the oxycen very low will eliminate the hw risk of early SCC in SS.

E{q The use of sea water in an emernency situation for ccoline the stean cen-tt erator woulc necessarily intreduce an air-saturated aqueous electrolyte with

• r3 This, when in contact with SS at coeratine tercerature in the mw j;d ni';h chlorio.e.

vicinity of 290 C, would definitely cose i threat of early SCO, certainly well There-h within a one week ceriod unis.s the oxycen is renoved from the solution.

' ore, i' sea water is used as standby coolant, it should be deaerated or its use should be discontinued within a natter of hours in order to reduce the ha:ard of SCC in 55.

The coints o' carticular vulnerability here would be those sites where chlorides concentrate as a result of toilinn or as a resuit

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of corrosion takino place inside the crevices or inside pits that would forn

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The relationship between cracking and chloride concentration (as well as i

electrochemical potential), correlates well with the work by Jones, who found no cracking in his tests in a 30 hour3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> test neriod when 02 was absent, and po-tential not controlled. Also, he observed no oits in his tests.

It seems reasonable to assure that the test by Jones could have run considerably beyond

-turs witn ne sa e result, since the electrocherical octential was net cuit-3:le 'c cracks or cits to develoo.

Consequently, unfer sirilar ccnditiens a stea generator witn SS~ tubes or an isolaticn condenser wouic be excected to

era e without cracking for a ceriod of several days.

However, Jones' work

ces nct cover the case where local boilino takes olace and wnere cniorides c 'J : be concentrated by a larqe ' actor.

As discussed in the next secti n '#cr ca;st : crackin?), local changes in concentration due to nea: ?Iux can occur i

r relatively raoidly, so that the kinetics of SCC art excected to be rate de-t ter-ining.

Conditions of increased concentration and rea: ' lux.vould have to be exolored in grea:er detail before a final c:nclusion :an te drawn recarding the icw 0, solutions.

* ?.

Jej Additional laboratory results by Rosborg in Sweden ane 3. M. Gordon'

.'s s -ewnat to clarify the cuantitative ascects of the Ouestion of Cl' and

~i.1 includes older data ::gether with are recent re'ationsnics vels.

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.etween chloride and oxycen, as surrari:ed by ~ordon.

t a renark nere is needed concerning crack proca:ation and : rack ini:iation.

!n SS tne crack velocity can be of the order of 0.005 -

0.0'." cer nour. Con-I secuently, once cracks initiate, they could :enetrate a thin-all tuce cuite f

cuickly. '4any alloys with increased resistance :: Cl 5:C have !cncer survival ti es :niy because cracks do not initiate readiij.

n rure ' alloys, 00 a initiation and crocaration are extrereiv si w o,e a:sent.

CAUS*** COACKI'ic.

.hereas the influ.< o' sea water int a steam erers::e :r an 4sola: ion :On-denser causes a droo in CH, other catural waters suc9 as river water, lake. vater, l}.

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I ib and perhaps municipal water supplies would lead to higher oH and introduce the danger of caustic cracking.

Since the SCC problem is affected by several variables in this case, it is necessary to consider the two pertinent factors seoarately, in order to determine their effects on the kinetics of caustic SCC:

j The rate and degree of concentration of HaOH due to boiling, 1

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chemical reactions, and the effect on OH of solution chemistry.

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The SCC of the retals involved.

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local Boilinn, Chenical Reactions, Soecies in Solution r

It is irportant to establish sore idea of the time needed to 'em a 1-104 localized solution of NaOH from the natural imoure water and the environment within the condenser or stear, generator. Concentration of alkali in waters

[h, can result fecn the high tencerature shif t of the equilibrior below to the right:

(I)

NaHCO7NaOH+C0f 3

%)

The chemical kinetics are rapid and the snecies always exist at ecuilibrium kG However, scale femation and crevices within the go.

aven at low terperatures.

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eam generator oroduce high heat flux crevices where the sodium hydroxide will The chemical reaction will not detemine the extent of hich alka-q concentrate.

line femation, but rather the themal hydraulics will deternine the concentra-j Hence, if occluded high heat flux regions exist, NaCH will concentrate tica.

g from an influx of alkaline waters such as those containino MaHCO.

W. Pearl 3

g et al.(5) calculated a concentration of 0.1 nolal NaOH within an isolated crevice with a heat flux giving a 10 C temoerature rise above bulk during a 0

Fevever, hydroly able species sucn hycothetical influx of "ississipoi waters.

as silicates which consure OH' to for5 inscluble products will have a stronc 4, n.

nederating influence on the rise in OH~ concentration (see Aopendix A' The f

jj dynanics of the steam fomation orovide the rate determinino steo, not the chemical kinetics of reaction I.

Soecific rates will be qualitatively described later.

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The case for the situation where a dissolved sodium salt reacts with cor-rosion products to form the alkaline crevice is different, as eiscussed next.

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l The anions of some heat-flux-concentrated dissolved sodium salt: can react with netal oxide and hydroxides within occluded regions to produce free dis-solved NaOH. For example, a possible scheme by which sodium phosphate will j

react with nagnetite is as follows:*

hide-out (II) Na HPO4 (bulk)

Ma HP03 (crevice) 2 2

(III) 4 H 0 + 8 Na HPO4 + 3 Fe ) A c v ce; 3

2 3

Fe (F0 )2 + 6 Fe(P0 ) + 16 NaOH 3

3 3

i (see Econcey et al., ref. (A)

The steanino dynanics which cause local concentration as considered previously will determine the rate of (II). The chemical kinetics of (III), however, prob-ably determine the rate of the overall process renresented by the secuence of reactions.

Times between 10-15 hours are recuired for III to ecuilibrate at

. 280 C for.09 nole phosphate /kc H )*( }

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l There is more information sucgesting that the hide-out process is more p

- 4 than reaction (III).

S. Yasnira et al. reported the existence of a cor-

. A concentration of phosphate within a ser.i-isolated crevice to be inde-pendent of bulk chosphate concentration or Na/chosphate ratio as observed after the 400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> of the test.

Concentration of cyrochoschates oroduced the same rates as observed after 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />. The concentration process clearly is not the rate determining steo for corrosion.

In tests at BML, using a in exarole of crackinc that occurred in the field is Benznau, where it was sus-pected that Ma pnoschate reacted witn iron oxide forced earlier in :ne life of the steam cenerator and which was converted into NaOH and iron chosonate when dosinc with phosnhate was started. As will be exanined later, it has oeen specu-lated and calculated bv various scientists, that NaOH of a relatively high con-centration can be cenerated esoecially in areas where it will not readily diffuse away sucn as crevices or underneath decosits. Other incredients tu"er these local electrolytes, so that the final pH decends On the overall electrolyte con osition.

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.01 M Fe250 solution at 100 C, the concentration at a steam blanketed region 4

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via hide-out of Fe(OH)3 through precipitation occurred within 1-2 hours, as M

shown by a rapid drop in local solution conductivity.

O In sumary then, concentration of species produced by heat flux proceeds j,'

quite caoidly and will be controlled by the relative rates of flow into and steaming from occluded regions.

If concentration of NaOH proceeds merely by gj' a heat flux concentrating mechanism of NaOH in the bulk solution, it will occur E.t quite raoidly. Somewhat lonoer times will be required if chemical reactions i

between hide-out materials must occur to produce the alkalinity.

For the pur-L, cases of SCC predictions, it has to be assumed that the time to form dangerous levels of NaOH, once imourities have been introduced, is short, i.e., one day

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or less.

An interesting possibility for mitigating the ':aOH SCC problem is to add f'f silicate to the inoure water. As stated above, it is calculated to have strong sucpressing effects on the level of caustic that is famed locally.

(This is not standard cractice, so that unidentified secondary citf alls may exist, e.g.,

(ft.

cossible builduo of local acidity and scale femation.)

)

Rates of SCC of SS and Inconel 600 in Caustic EC 4

Laboratory tests with caustic have been done by various groucs such as 5I and 391(10) so that there is a ocod amount of data for k

4estinghouse G'

predicting wnat would haopen in NaCH solutions of various concentrations. Un-VJ

.~,i fortunately, an unknown asoect in this correlation to be made with field condi-t, tions is that the influx of impurities will not give rise to a credetemined 4'$

concentration of NaOH and a fixed electrochemical potential.

Therefore, in different parts of the stean generator a whole series of caustic concentrations

<e, may arise decending on location, as stated before, and also on the concentration in of other species such as silicates.

Consequently, it is necessary to consider kh the e' ?ect of several levels of ' tach and 0; plus other ions in trying' to determine 6

@4 how SS and Inconel alloy tubes will perform.

5

$g It is generally accepted that the use of slowly strainino specimens nives y

rost severe results, followed by U-bends, and that C-rings oive the longest failure times. However. since stresses of anknown levels can exist under oper-ating conditions, it is felt that sufficiently conservative conclusions can be 2, 4

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based on results with high stress, i.e., U-bends, for which the largest number 10" of data are available.

Mestinohouse data indicate that U-bends of Type 304 SS in deaerated 10",

NaOH can crack in three days or less and similar results are obtained in higher f

concentrations. At 90% and 1105 of the yield in 105 NaOH, 304 shows only minor surface penetrations in 220 days, and 25 mil cracks in 33 days, respectively.

j Obviously the stress level is proven to be quite significant. Compared to this, r

alloy 500 cracks in a matter of several months and Alloy 300 (Inconel) behaves ore like SS than the nickel base alloy.

Since the earlier discussions showed

• nat enemical changes can occur raoidiy to raise the pH, it is evident that there should be concern about SCC in SS within a matter of a few days if impure

[

(NaCh-forming) water is introducad. 9iticating factors would be (1) absence o' high stress, and (2) s?ecies in solution that suppress NaOH level.

For Inconel 600 in cases where 0 is not oresent, less probability of SCC within 2

one week exists, because laborator,v data indicate relatively lanc failure times.

This is believed to be a result of the hicher Ni content of Inconel.

The cerformance of SS, and tiloys 600 and 300 in 505 caustic with and with-cut additions is given in Table I, taken fran reference (3).

It is evident r ;

that Alloy 600 is much more resistant that 30455. Also, some additions such e Ob3 or SiO would be detrimental.

2 In practice, it nust be considered that tne introduction of river water other relatively "high Na" imoure water will be air-saturated, and the oxygen would be replenished as more and more of this solution is used, so tnat specific steos will be needed if 0 is to be removed.

Earlier International Nickel Co.

2 results showed that Inconel 500 cracks in caustic soda at high concentration with 3

an over-cressure of oxygen or air. '!hile the level of oxygen in the Inco test en was higher than the level of 6-8 ppn excected to be introduced by a solution in ecuilibrium with air, the field condition will nevertheless continue the supply

~fne was radually of air (0 ), whereas in the c. sed system used by Inco the 02 2

lowered by consunction during the test oeriod.

In this case, therefore, Inconel i

l 500 is in an ill-de#ined crey area where it is not certain whether it possesses adecuate resistance to SCC for one week i# air is not removed. Another complica-

/In1 tien is that results obtained by Theus at Bff indicated that a small shi't

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This observation in-in the anodic direction can introduce SCC in Inconel 600.

E 8 0, b.'

dicates that there are two bands of electrochemical potential in which there is the one lines at a high level, cor-4 a danger of SCC of Alloy 600 in caustic:

.b responding to a considerable over-pressure of air in the International Nickel

,uy M.

Co. tests, and the second one is lower and nearer the electrochemical potential o'f a deaerated solution and corresponds to the B&W and Westinghouse controlled d

P A safe zone is believed to exist between these two, and there-potential data.

fore there may all be cause for concern over a relatively low level of oxygen a

or otner oxidizing s;ocies which could cause a sufficient snif t of the corro-np sion potential in the deaerated's'olution to nove into the first. band of caustic levels. The amount cracking, which could be as dangerous as much higher 0 2

L 1g%h of oxygen recuired for this shift has not been determined accurately, and such tests are needed.

The bottom line for Inconel 600 is, therefore, that contact at ocerating M

temoeratures with ?!aOH-forming impure water should be avoided or discontinued can be removed, or (b) 'laCH 'or a-O in less than two or three days, unless (a) O2 Further, lowering the temperature as cuickly g

tion sucoressed in local regions.

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h) as possible would be beneficial, as caustic SCC of :nconel 600 is known to be kh Also, it is evident that a better knowledge of M

strongly temoerature-decendent.

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..nat local ccnditions in tems of TiaCH and stress may develoo in service, wou d Jg N

make predictions a great deal easier. The addition of SiO, which can buffer 2

the builduo of itaOH, nay also intensify the situation if large amounts of caustic K4 are cresent, as can be seen in Table I.

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CPACKINr, OF I!!C0!4EL AND SS IN RELATIVELY PURE WATER WITH A SMALL AfiOUNT OF

. &.f OxYGEtt PRESE!ai The crackino of SS in water with only a little oxygen present has occurred r

in sensitized SS even at low tenperatures.

Should such material be in service, then the simnle introduction of a snall aincunt of oxygen could oose a croblem g

The cracking rates appear to in highly stressed or actively straining reg.Jns.

be a 'aximum at 200 C.

An analysis of the situation in a steam cenerator or 0

isolation condenser indicates that the chances of such cracking are low, because the tubes are not usually installed in the sensiti:ed condition, so that th'e

~his tine reouired for cracking can be excected to be longer than one week.

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s l Os would not be the conclusion for sensitized material; for this reasoq, it is also important to consider welds, the original material, and also the possible longer term sensitization that is known to occur at operating temperature.

Experi-cental data along these lines are incomplete, and require emphasis if the SCC orablem in impure water is to be addressed comprehensively.

Reference to

" original material" abgve concerns mill practice which may not be sufficiently controlled to ensure delivery of 100% unsensitized. stainless steel tubing.

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e REFERENCES 1

W. L. Williams, Corrosion 14,,1958.

2.

R. L. Jones, Corrosion 31,, 1975.

B. Rosborg and A. Rosengren (Studsvik Energiteknik, Sweden), unpublished 3.

G. Economy et al., Proc. Intl. Water Conf. 36,, p.161 (1975).

4.

W. L. Pearl, S. G. Sawochka, "PWR Secondary Mater Chemistry Study " NW l

J Tenth Progress Report (EPRI Agreement 1404-1) Nuclear Uater Maste Tech 5.

P.O. Box 6406, San Jose, California 95150 (February 1978).

F. W. Pement, I.L.W. Wilson and 3. G. 8speden, Paoer *50, Annual NACE Con-t 6.

ference Atlanta, Georoia, arch 12-16, 1979.

7.

I.L.W. Wilson and R. G. Asoden, Corrosion 32, 193 (1976).

I.L.M. Wilson, F. W. Perent, 4. G. Asoden and R. 7 Begley, Nuclear Tech-3.

nology 31, 70 (1976).

34, 311 (1978).

I.L.W. Wilson, F. U. Penent and P.

G. Aspden, Corrosion 9.

10.

G. W. Theus, Nuclear Technolooy 28, 383 (1976).

B. M. Gordon, ffaterials Performance 19, =a (April 29, 1980).

~,

3) 11.

}

Literature references co the subject of SCC are overwhelming, and several dozen, if not several hundred, could well be cited here but would not add f

NOTE:

to the basic arnuments that were rade above.

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The Effects of Oxygen and Chloride on the SCC of Austenitic Stainless Steels in High Temoerature Water i

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(Ref.8)

Stress Corrosion Test Incidence of Te-NI-Cr Alloys in Strong Causue with Additivee v/

(Mill-annealed C-rings in duplicate, at 110% of yletd stre'ngth, exposed to equimolar 50%

l OCOH + NaOH) + additave; 620*T: 1,3, or 6-month exposure.

1 One sample / heat metallographically examined for cracking.l k.g

,g Type 304 N

Additive Months Stataless Steel Incoloy 800 Inconel 600'

.k Lt 1

Cracked Not cracked Not cracked None 3

Cracked Not cracked Not cracked 6

Cracked Cracked Cracked 6

Secondary sludge 3

Not cracked Cracked Not cracked b

h 6

Cracked Cracked Cracked 10% Sion 3

Cracked Cracked Cracked g@,

6 Cracked Cracked Cracked F Pb (as Pbo) 3 Crack ed Cracked Not cracked 6

Cracked Cracked Cracked 1000-ppm Cl* (as NaCI) 6 Cracked Not cracked Cracked 1000-ppm T* (as T*)

6 Cracked Not cracked Cracked ytj 0.5% As (as Aa:Os) 6 Cracked Cracked Cracked 1% B (as MsBosi

.i C' rack ed Crack ed Cracked 10% sodalita' 6

Cracked Cracked Cracked hh 5% 2n 6

Cracked Not cracked Cracked I

h 1% Cu (CuaO - Cup 6

Cracked Cracked Cracked h

5% Cr (as Cr:Os) 6 Cracked Cracked Cracked k

10% Na.NO:

6 Cracked Not eracked Cracked p, c.

rg*. y,

• Tive heats of Inconel 600,2 samples per heat.

b:S g of sludge in 500 ml of caustic solution. Studge from plant with : y of a!!-volatile treatment and 3 months j

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DISTRIBUTION LIST:

..M U.S. Hazelton V. Benaroya s ).

S.S. Pawlicki M.

F.M. Almeter M. Fletcher

[ j; B. Turovlin

$4 S*ll:

7 *. *,

4-h4 D. van Rooyen

1.. -

M.W. Kendig R.:

W.Y. Kato L.

.j Kf 98 Ee

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V- .L. .u. o + I g, a 1. APPENDIX A l %b 4 %. Taael and S. G. Sawochka* have made a calculation of the pH rise due - --- J.. c to concentration of impurities introduced by a tiississippi River inleakage. s. icked Concentrating effect is limited by B.P. elevation which was taken to be e ick.e 0 10 C i:ked y = -loa H H = H, concentration ,,4 e{DefinepH g I neutral pH is that where H = OH.- 24 i

• *d ied For an isolated cavilty with the 10 C temperature rise and a fresh water in-o

.g gress (!!ississippi Water), the hydroxyl ion may reach a concentration of .e ed 0.1 molal in the absence of silica. This correscends to a room temperature 'd cH of 13. ed 'd Silica can produce a suporessing (beneficial) effect. id Through hydrolytic precioitation silica.will buffer the solution to g g(a lower DH at high concentration factors. e.g.,100 opb silica will reduce :Se level to N 10 to 10-3 molal for the same conditions. suie PWR Secondary Uater Chemistry Study 10th Progress Report NUT 116-1C, Feb. '970, e EPRI =c04-1) Q. qj A.1 - -.=

._c-1 _~ 4., ~ - . _ m.., s.-.. _~ n ,) c' ,, c - i IC. g ENCLOSURE 2 iO '~ STAFF POSITIONS REGARDING S_EP SAFE SHUTOOWN SYSTEMS REVIEW 0YSTER CREEK NUCLEAR PLANT 1. The licensee must develop, by April 1981, plant operating / emergency pro-cedures for conducting a plant stiutdown and cooldown using only the systems and equipments identified in Section a.0 of the SEP Safe Shutdown Systems report. 2. The licensee' must propose a technical specification change to establish a minimum conden nte storage tank inventory of 90,000 gallons to accomodate the safe shutdown water requirements identified in Appendix A to the SEP Safe Shutdown Systems report. h t 9 l j _.}}