ML20040C002

Overview of Water Chemistry for Nuclear Power Plants, to Be Presented at ANS 1978 Annual meeting,780618-23

ML20040C002
Person / Time
Issue date:	06/23/1978
From:	Almeter F Office of Nuclear Reactor Regulation
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ML13319A635	List: L-79-421, Forwards Steam Generator Insp Results Re Cracking of Small Bend Radius Steam Generator Tubes at Turkey Point Unit 3. Concurrence Requested Re Proposed Corrective Actions ML13319A634 ML20040B988 ML20040B995 ML20040B998 ML20040C002 ML20040C010 ML20040C040 ML20040C045 ML20040C050 ML20040C055 ML20040C060 ML20040C061 ML20040C065 ML20040C071 ML20040C073 ML20040C075 ML20040C078 ML20040C081 ML20040C086 ML20040C090 ML20040C093 ML20040C097 ML20040C102 ML20040C105 ML20040C113 ML20040C116 ML20040C121
References
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Download: ML20040C002 (18)

Text

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Paper to bo Precented at American Nuclear Society 1978 Annual Meeting g

Juno 18-23, 1978 San Diego, California q

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AN OVERVIE'4 OF WATER CHEUSTRY N;

FOR NUCLEAR POWER PIMrS 81 a.3 37 T

w,

~ F. M. AU!ETER, Ph. D.

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m g'p U. S. Nuclear Regulatory Cc mission lj Vashington, D. C. 20555 Q].1

.:3 z-Y l$

sum ARY

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.7

.)7

..d This paper ste:.srizes NRC's overview of light water reactor water che:-

,Qt istry and its significance in the context of the rapidly rising inci-d

• 4

[,h donces of corrosics-induced degradatien of nuclear plant components

, and the need to implement means for nonitoring and control of both the

.g (1-5)

'64 primary and cecondary co,lant purity.

Control of water chenistry

, ;b 7'y) f.. " iln nuclear power generating systens should have these main ob.jectives:

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1. Reduce contamination in all systems to the lovest practical 1evel.

2; Control general' corrosion of metals and re-deposition of kW corrosion products.

dk 5.Proventstresscorrosioncrackingofausteniticstainless

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steel alloys.

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4. Improve steam purity and reduce contaminate carryover.

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5. Mininize plant conponent failures'and downtine to increase overall plant efficiency and reliability.

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. 6. ' Provide reasonable assursiee that plant integrity is not reduced below a level acceptablo for safety.

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D PRITMRY_ COOL.CT O'i'sLITY j

Regulatory Standard Technical Specifications require chloride end S

fluoride w..

.ancentrations in the PWR reactor coolant to be maintained

$3 (8) at less than 0.15 ppn during all nodes of operation.

Dissolved y

oggen is to be nairitained below 0.10 ppm during periods when the

.,?

yj naterial exposed to the reactor coolant is at te=peratures above 250 F.

0

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The halogen ions and oxygen limits reco=nended are specifically appli-

'Afj cable for new PWR facilities.

As these facilities achieve operating

?j time, the potential for halogen ion contamination of the primtry cool-

'9

]k ant becones less critical. ' Although o pgen must be continuously 3

scavenged with additions of hydrazine.

su

.n 3

(

,j Ad a c~o~ncequence of the increased incidences of stress corrosion crack

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. y]

ing of mnll diameter pipes up* to 10 inches)..\\inoperatingBWRfacil-3 3

(2) e water purity criteria spe:.lfied in ebe 4

.',i ities,.the NRC staff is chQ.i;

.]

(9)

_ -fz, 1973 for BUR 8s.

Water chedstry parameters should be controlled within

, ' j:1

'the following limits: Specific Co'nductance 1-10 pnhos/cm C 25 C c

AM

.h Chlorides 0.1-0.5 ppa, and pH 5.3-8.6 The new requircsents for

f

-BVR8s do not include the oxygen parameter because research needed for methods of control and a sound basis for limits is not yet conpleted.

,.E The current i.nvestigaticas on corrosion and oxidation in BWats by

'Y i

(10)

)

H. E. Indig and co-workers nay provide the basis for oxygen limits.

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SECONDARY COOLA"T QUALITY

.h) i Pressurized water reactor steam generator tube integrity can be degraded p,

N by corrosion induced vastage, pitting, stress coiresion cracking, reduct-

' ],j ion in tube diameter (denting.), and vibration ia.duced fatigue cracks.(6,7) d (11)

(12,13) 1.0 P. V. Frlakrishnan and others have shown that a corrosive envi-0 rcraent may be generated within the stean generator resultin'g from the

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concentration of various impurities that can contaninate the secondary

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)k cc.?l.mt via condenser in-leakage and possibly the feedvator heater tub-h

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9,y Three types of water chemistries ere-ree m uudea for the steam generator L

f secondary coolant to miniuize corrosion'and prevent r.cale for=ation en

,pd 1,y the exterior surface of the steam generator tubing: the congruent

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-7 sodium phosphate treatment, an' all volatile treatment (AVT), and a zero 5

9 J.P solids treatment (ZST).

All PWR plants. are;not co=mitted to an AVT

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,3 chemistry.

Two older units are using the phosphate treatnent.

Ifany -

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(14) g new plants, as well as some cider ones, have chosen the ZST method

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,sp for vater chc=istry control.

'l9

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For some time, the IEC staff has been enmining the factors that con-B tribute to the degradation of steam generator tubing.

In August 1976, 4

f NRC sent letters to PLbicensees requesting that they propose Technical y

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Specifications for steam generator secondary coolant.

For U tube designed steam generators, guid: lines voro suggested for a total cation

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pn);

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[4h -~~ ~'---' condudtivity of 0.2 }mhos/cm 0 250C on the condensci condensate and for x

the steam gone.ator blevdown a cation conductivity range of 3-10 p:hos/cs 9

(.h)

C 25*C, pH 8.5-10.,'and 1.0 ppm for free hydroxide.

These secondary '

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coolant' para.cters vere based on the known stat of-the-art that' retarded j'y (15)

,g vastage and caustic stre.s corrosion cracking on the O.D. tube su faces.

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Secondary coolant parameters for the avoidance of " denting" have, as yet, not nateriali::cd.

Chlorides,solublecopperand/ornichelions, 9N,.

and some cations in solution are suspected impdrities that catalyze the

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formation of nagnetite on the carbon steel tube support plates and 4)

(4,7) resultant denting.

3

.Mb Imposing a specific technical specification for the control of secendary vater quality would not be appropriate at this time; as it may prove

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yI to be wrong (e;g., Beaver Vaney Unit 1) and not linit specific types

.c.j' of severe tube degradation, particularly " denting".

Besides, any y

unproven secondary water chemistry para eter limits in a technical l 4)l gpecification nou for PUR8s may have an adverse effect on the stean f]

(5)

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.pur ty and cause potential failure of turbine ce=ponents.

Therefore, VM-

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NRC would be receptive to alternats technical specification proposals, 1<l3 frce tho utilities, that will reflect monitoring or surveillance.progra=s

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with appropriate correctivo actions to assure water quality control of

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AUELIARY SYSTMi FTIDS 1.*

Na

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Borated water used in the ECCS and contaire.ent spray systems of P'Ais

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. il should be centro 1 Icd to a nininum pH of 7.0 during operation.

In ElR8s,

.o v4Q tho t'ollowing linits should be maintained on the water ~used for the ECCS

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. Conductivity 3.-10 }nhos/c 0 25 C, j

and contairsent spray systas:

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. +5 Chloridd (as C1') f 0.50 ppm, pH 5.3-8.6 e 25 C, and Total Insolubles m

j 6 5 pF.

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l l ;q CONCLUSIONS

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',@*p The concern for high quality water in nuclear power plarils is important

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during all operations because vator is often transferred from one part

'k of the plant to another which increases the potential for contamination.

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Contaninated water can increase the probability of corrosion-induced l -,

l c.Q failure of the intregal camponents of the reactor coolant pressure

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Y Oral Precentatien at Ybd'sf f v.'

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/c.orican Duclear S6ciety 1978 lannual Mce' ting i

Juno 18-23 1978, San Diega, California

,/;

I AN OVERVIEW 0F WATER CHEMISTRY

,.gg FOR NUCLEAR POWER PLANTS by 2

.j F. M. Almeter, Ph. D.

f U. S. Nuclear Regulatory C emission, Washington D.C.

3 INTRODUCTION 1#

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.. i

,.y Relative to the requirements of Appendix A " General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50 which assures that the reactor w

coolant pressure boundary will have minimal probability of gross rupture q4 or rapidly propagating failure, the NRC's role includes constant monitor-9]

b ing and evaluating the operational performance of nuclear plants to 1.')

' 4..

ensure adequate health, safety, and protecti,on levels for the public.

( d.'i l ' 11 In the past several years, operating experience of light water reactors (LWRs) has indicated various operational problems related to the integrity ol.g of the reactor coclant pressure boundary. lA primary consideration for

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the assurance of this integrity is the ability to control corrosion by

../g avoiding contamination of the primary and secondary coolants. The lM l.,g concern for high quality water in nuclear power plants is inportant during-all operations because water is often transferred from one part of the

'j plant to another which increases the potentia,1 for contamination.

'q A1

!C 1.1 This paper scarices NRC's overviev of light water reactor water chemistry f]

and its significance in the context of the rapidly rising inci(ences of

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_j corrosion-induced degradation of nuclear plant components and the need

'S to implement means for monitoting and control of both the, primary and q#

secondary coolant purity.

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NEED FOR WATER CHEMISTRY CONTROL

{.h Laboratory tests and service experience have shown that chlorides.

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.'ij fluorides, dissolved solids, and dissolved gases that lower the solution d.3 pl{ are the. principle impurities in nuclear reactor coolant waters, that

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can cause general corrosion and stress corrosion crack'ing of normally

~p corrosion resistant materiais within the reactor coolant pressure boundary. ~

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.,y The effects of the halocen ions are well known and will not b.e discussed W

here.(1-4) Many survey papers have discussed the effects of oxygen and t

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'.YC pH on intergranular corrosion of austenitic stainless steels.(4-8) t

-ry

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Incffective control of impurities to 64m4_::e the correcive envirement

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! wj of the circulating coolant watern has led to sovere degradation of asso-.

..L.3 tr lt ciated piping systens in boiling vater rca'etorn hE's) and the tubing-3, and tube support plates of pressurized water reactor (P'.a) steam generators.

.-'h An adequate nargin of safety must be ncintained for these intregal components of the reactor coolant pressure boundary.

u.9 9;',j

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.)M Since 1965, stress corrosion cracking of type 304 and 316 austenitic

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stainless steels exposed to the reactor coolant environment of BWR

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' facilities.hac been related to chlorido intrusi6n in the reactc

coolant,

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!a but in most cases to a combination of significant amounts of opygen in d

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, :6 q:f the reactor coolant, high residual stress, and sensitization in the heat

'M; affected zone (liAZ) of welds.

Similar failures have not been prevelant.

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inPhlRs,mainlybecausethewaterpurificationmethod'sandthemechanisms l$

for reactor coolant corrosion are different in the BWRs. Although it is l}

'#j important to understand these differences, they have been discussed in 9

l?g another. review (9) and will not be covered in this paper.

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Pressurized water reactor steam generator tube in'tegrity can be degraded n

J.

by corrosion induced wastage, pitting, stress corrosion cracking, u.

Lj reduction in tube diameter (denting), and vibration induced fatigue cracks.

,8 l '..]

Wastage has occurred with a coordinated phosphate treatment of the second-et.s

, ary coolant and, in some cases, after the change-over from a phosphate

?b

• 9 treatment to an all volatile treatment (AVT). Wastage and pitting are

, }:Y

' attributed to the local concentration of residual acidic phosphates and possiblyimpurities.(D-N) Stress corrosion cracking originating on the exterior surface of the tubes is caused by either the formation of caustic

[

' compounds in the steam generator or caustic forming impurities carried in

• J by the feedwater.I

'")

Stress corrosion pracking originating on the

..e.

interior surface of cold-worked tubing occurred when LiOH was not added l9 t'o' raise the primary coolant pit and sufficient oxygen was not scavenged.(13,14)

'59 d

Denting is believed to be caused from the in4cakage of condenser vater 3

impurities corroding the carbon steel tube support plates in the rdgion o'f the' tube / tube s'up' port plate crevice.I I Fatigue cracking may be

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from high cycle vibration induced by excessive horizontal cross-flow of

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j water across the tube bundle.

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OBJECTIVES OF WATER QUALITY m

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.e4 Control of water chmistry in nuclear power generating systes should.

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?.sve these main objectives h

1.

Reduco contamination in all systes to the lovest practical 1 cycl.

S.Lj 2.

Control general corrosion of metals and re-deposition of corrosion i

'?.4 products.

h 3.

Prevent stress corrosion cracking of austenitic stainless steel alloys.

4.

Improve steam purity and reduce contaminate carryover.

,d.y 5.

Minimize plant component failures and downtime to increase overall

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,9 plant efficiency and reliability.

[.. e 6.

Provide reasonable assurance that plant integrity is not reduced below a.r;

~ T,],7 a level acceptable for safety.

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PRIMARY COOLANT QUALITY

3 4.f Prior to September 1974, the former U. S. Atomic Energy Commission (AEC) issued Regulatory Guides 1.44, " Control of the Use of Sensitized Steel"(I }

jyj and 1.56, " Maintenance of Water Purity in Boiling Water Reactors"(19) which l

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required the control of impurity levels in the reactor coolant of both

,2 1 :n PWRs and BWRs.

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PWR Water Chemistry

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9 Regulatory Guide 1.44 and subsequently Regulatory Standard Technical

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,5 Specifications require chloride and fluoride ion concentrations in l

y the PWR reactor coolant.to be maintained at less than 0.15 ppm during

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Q all modes of operation. Dissolybd oxygen is to"be maintained belo'w h*

0.10 ppm during periods when the material exposed to the reactor

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coolant is. at temperatures above 250*F.

These requirements are 3

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j designed to minimize the potential for stress corrosion cracking.

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The limits for chloride, fluoride, and oxygen M,m.et $Een- & ^d

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' f.or4R4eei+iMer * "ill ha n nemu M agog y -

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.y nngeniarv_rm m_L44_wMehai11kn43ceg h,s;m i m ye y

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~ acefeien-Hou provides control's for processing BWR sensitized welds l.

,.i. to prevent oxygen-assisted stress corrosion cracking. This change 3

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..,., has been made to emphasize that parameters for controlling water 9

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.:. quality in BWRs is different than PWRs eod 4 h u.y Guiae i. w i3 a

M rEN~^d 4 Rev4+ ion-No, & It should be noted tha't the halogen

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ions and oxygen iinits recomended in Regulatory Guide 1.44 arc specifically applicable for new PWR facilities. As these facilities j

7 achieve operating time, the potential for halogen ion contamination

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of the primary coolant becom's less critical.

nthough oxygen t:ust be e

3

.f

1. g continuously scavenged with additions of hydrazine.

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l, 2.

BWR Water Chemistry The June 1973 issue of Regulatory Guide 1.56 recomended control limits for conductivity and chlorides in the BWR water chemistry (Table'In).Theselimits.weredesignedtopreventchlorideintrusion d

of the reactor coolant and reduce the potential for similar incidences

'M

,like the one at 11111 stone Unit No.1 in 1972.(3) The BWR water cycle i

incorporates deaeration equipment, demineralizers, and a reactor water i

cleanupsystemtomaintainhigh-qaulitywater(Figure 1)

Therefore,

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1,9 Ii it is important that the feedwater at the outlet of the condensate

'demineralizers be free of ionic impurities (particularly C1' ions) 1

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.and suspended solids.

Conductivity is the most important criteron

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,for the establishment of high purity feedwater'in a BWR water cycle,

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i and it can be used for monitoring dem'.1eralizer performance.

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Tableib shows conductivity limits that were considered, prior to f

June 1973, to be indicative of imminent breakthrough in one or more

.y of tiie demineralizer units.

j T3 1

In September 1974, it became evident that small diameter pipes j

M (up to 10-inch diameter), containing stagnant or low velocity fluids, s1 f

are more susceptible to stress corrosion cracking than either small a

or laiger. diameter pipes containing a' continuously f' lowing fluid

&It during plant operation. Studies have shown that such cracking is e

te caused by a combination of the presence of significant amounts of oxygen, a low coolant pH, high residual stresses, and some sensitiz-

'ation in the heat affected zones (HAZ) adjacent to welds.(9)

Residual stresses and sensitization can be controlled to reduce the

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stress corrosion cracking susceptibility of BWR piping. However, alternate methods, other than deaeration for the control of oxygen, e

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are yet to be developed. This also applies to pH control which is

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currently maintained with demineralizers and the reactor cleanup 3.g

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High chloride concentration.s and low or high pit conditions in the 3

primary water can also promote stress corrosion cracking of unstabil-('

ized austenitic stainless steels.

Since some cxygen (0.2 ppm to 8 ppa)

.]f is alvhays present in the BWR primary system water and the most dif-

.i3i ficult to control, concentrated efforts are being made to maintain a h

?

dd water chemistry with low levels of chloride [and'a near n l

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E during. all modes of operation.

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tQgwl4 s h c%ff n, dj As a consequence of the inci;eated inc;iden f pip cracking in X 4

' opera ting BWR facilities, hWi-Nv.. i dv ' Regulatory Guide T.56-

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TablDe..ews proposkinew criteria for u

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and chlo' ride of t Y

conductivity, pH,fue.ev.Mw e "he rea'ct'or coolant water during D.44t. 2

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various plant operating conditions.

Control within these parameters will assure a reasonable stoichiometric relationship between 2i conductivity, pH, and chloride concentration.

Figure 2 gives this

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relationship in water at 25'c

which is useful in establishing

'*2

'y, approp'riate conductivity /pli limits and ala setpoints.(20) The h.y reactor water quality for BUR's does not include the oxygen parsnete:-

9 because research needed for nothods of control and a sound basis for J.

limits is not yet completed.

The current investigations on corrosion

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);j and oxidation in EUR's by M. E. Indig and co-workers may provide this

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basis gl1 j

The NRC staff believes that continuous nonitoring of the.conductirit'/ ct j

appropriate locations will assure adequate control of the reactor k

water quality.

Table 3 gives conductivity limits for the condensate

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treatnient sy' stem to indicate when corrective actions are required

% u w &; ' Regulatory Guide M

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i to maintain water chemistry purity.

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O 1.56 require conductivity measurements also at the inlet and outlet 1

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of the reactor water cleanup system (Figure 1).

New positions also l

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.:.0 require that for both the reactor cleanup system and the condensate j

demineralizer system the pH and chloride concentration of the y$y reactor Water be periodically measured and their relation to the 5

specific conductance be confirmed.

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' SECONDARY COOLANT QUALITY w

t c f:0 The secondary water cycle system in most PPRs is a closed-eyele dithout 3

g fij a purification system for water chemistry control. The_~ water quality of

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the secondary coolant is controlled by chemical additives which must be m.*.:

-Q of a type that will not become highly corrosive when concentrated in

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'l 7J crevice areas of the steam boiler.

High impurity concentrations occur

. c. a cJ at crevices between the tube / tube support. plate a,d where slud e 5

j deposits on the tube sheet.

P.V. Baiakrishnan(52) and others(D' d

-a M.)

' have shown that a corrosive environment may be generated within the steam

-.9 generator resulting from the concentration of various impurities that

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can contaminate the secondary coolant via condenser in-leakage and possibly

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- the feedwater heater tubing material.

Ineffective water treatment to O

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q.:. n

.3 remove the impurities and prevent local concentration in the steam c

1 2;\\

l,Q generator have lead to severe degradation of, Inconel-600 tubing. The h

types of degradation have been discussed earlier.

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Three types of water ::hemistries are recomended for the stcam generator

^.

, ]n secondary coolant to minimize corrosion and ' revent scair. formation on L '.

p 3

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, the ester.ior surface of the ' steam generato: tubing:

the. congruent sodium y

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ktNg q;c;q. w : v g ".n?.~. y..p y ;-p,y y.;.; m p p.

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f ry coolant parameters for the avoidance of denting L..m, o,m i., ~

nnt mf orinH mrL Chlorides, soluble copper and/or nickel ions, and some cations in solution are suspected impurities that catalyze the formation

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of magnetite on the carbon steel ' ube support plate.end resultant t

(15, 16) r;,,,,,,.,_,_,,.;t,,,;,, g,_',,,,,,,,,,

i a nunn Although it is clear that these impurities must be kept to a minimum, t no operating experience of domestic plants that have developed sore degree of denting (Table A) has not yet provided a solid basis s

to s7pecify water chemistry control limits for these irotrities.

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' degree..ofden_ ting (IahlAA)m -- ~

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STEAM QUALIT_Y_

j Sodium hydroxide, sodium sulfate, sulfides, chlorides, and silica are j

an example of impurities that may be in the steam phase of nuclear power plants.(27,13) Carry-over of these impurities to the turbine can cause s

damage to discs and blades due to corrosion, stress corrosion, and ccr-rosion fatigue. A high pH level in the steam phase may be another cause o

for caustic stress corresion in turbine components as indicated by 0

experiences in PWRs and fossil power plant units that use steam 1

. generators. (28, 29 ) Unlike these plants, the BWRs maintain a near neutral pH and tend to minimize the Ha ion cpacentration in the steam a,nd, so far, they have not had any caustic stress corrosion failures.

ibviously, NRC is concerned about the centrol of steam purity but safe

, acceptable impurity limits havo not been developed.

They may be

, dependent.on future controls' established for the PWR secondary coolant.

l l

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s 12 -

(1

S AUXILIARY SYSTEM FLUIDS

'n t

.;'Q; All LWRs should have controls on the water chemistry for their auxiliary G

d

.. systems to ensure tne integrity of any unstabilized austenitic stainless B

.y steel components and other materials that may be degraded by a corrosive 04 J

environment.

Revision Nc.1 of Regulatory Guide 1.44 has reconrnended D

4..,

guide lines for both WRs and SWRs.

Borated water used in the ECCS and

.3 g

containment spray systems of PWRs should be controlled to a minimum pH 3

of 7.0 during operation.

In BWRs the water used.in engineering safety

.g t

',[.

.syGems should be controlled to provide assurance against stress corrosion

~j cracking of stainless steel components.

Tfie followir,g limits should be d

r Ej maintained on the water used for the E^CS and containment spray systems:

?~4 Conductivity 3-10 pmhos/cm 0 25'C o '....

f Chloride (asC1)

<0.50, ppm ln-pH 5.3 to 8.6 0 25'C '

j Y)

Tctal Insolubles

<5 ppm -

l.y I *n

SUMMARY

AND CONCLUSIONS 1.f The importance of ensuring component integrity in nuclear power plant I

systems has been discussed' from a water chemistry control point of view.

7

't The need for eventual controls on imourity contamination in the secondary sj 2

. coolant inh].uding the steam phaso foi PWR's have.b'ecn described.

Condencor Y_1 cooling water in-leakage to the condensate has been identified as the i

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J

, major source cf impurity ingress in the BWR primary water and the PWR

~

1 4 seco'ndary wa' terr 7,

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',n ur..v n c p>7 3,p.-

' p - -, ;.p r -- r -,,,.3 3,7 9 7.;7 - -._. ;, w s <-

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2 New requirements on water quality for the prima,ry coolant and water

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chemistry controls for auxiliary systems in LWRs has been presented.

i g

g The additional specifications for conductivity measurements in con-t

. junction with pH and. chloride measurements will provide a more m

Q accurate control of reactor water quality in BWRs. The installation 4

1 of additional conductivity meters on plants in the CP and/or OL review

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stage is,not considered significant from a cost' standpoint, in view M

!s7 of their contribution in providing an early iarning of impurity g

7 intrusion and cafer reactor operations.

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Ej

-All PiTR plants are not c e itted to an AVT chemistry.

Two older-l 4

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l yy units are using the phosphate treatment.

Many ncv plants, as well as

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',*j sane older ones,(25)have chosen the ZST nethod for water chemistry

,a

'N control.

NRC recognizes that different utilities uso different p

'g secondary water treatment methods and each nethod is ualque for each 3

f

.y}i facility to inhibit the pote.ntial e nt u.. nation of the steam generators.

j :'. ;

NRC realizes that necting

sccendary cocInnt water quality criteria

\\

l would not be possible during all periods of operction.

Furthermore, t

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"O niacd%= 1. is nca.,uy that the post effective procedurcs M b

4hbised for re-establishing out-of-specification chemistry parameters n plen+ r; o_'i.. @ k War'd47 d i-+3

%t@ f g<*N W%.?

.N' is i,j This was made evident by the. need for NRC to revise the Beaver Valley

n j$

Unit 1 Technical Specifications. This Unit was operating with an

.4 AVT cli.'mistry and the NRC Technical Specifications cited 'above.

During 3

initial startup, the blowdown catien conductivity was exceeding the S.

j.g specified 3-10 pmhos/cm at 25*C by a factor of 4 to 5 and the limits 3

<.4

>M N

.v.v.? m ;q.

m y y*t

,m,w..y y y(.cr e Q19t'R5v myc.y vv e..e w > r.,qf t.>v.D #

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p.

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%%., :k%a

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.y could not be reduced to enable operations to pr ced beyond hot

~

-j yy shutdown.

It took approximately one month of blee nd feed to bring

'"y thd conductivity down to maximum allowable limits.

T is trend reoccurred t

sr -

s during subsequent startups. It "ee ne~e" c 6 d h. the unit to

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. exceed 15 jrnhos/cm 0 25'C conductivity on the blowdown for 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> M

during all stgrtup conditions.[A Q% c.4.m.c'A, 3

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Restri.ctions on the use of a specific water treatment method and

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..%y

, limitations on water chemistry parameters in a T'echnical Specification, I

or the requirement for plant shutdown until out-of-specification limits are corrected, would not provide the flexibility of adding specific b

.. chemicals associated with other water treat'ments methods; e.g., the

.7

}

jf CMDU mthod which may be more beneficial for the removal of harmful

~

s-impurities contaminating the secondary coolant. Other methods for j

6 assuring high quality water in the steam generator may prove to be j

more effective than an unwise Technical Specification; such as

'j maintaining a tight condenser and full flow condensate demineralizers for long term solution.

For short term solption, periodic chemical sj cleaning, flushing or free surface boiling, or the use of' chelating C

Agents may achieve satisfactory results with greater cost effectiveness.

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'4 Imposingd specific T chnical Specification for the control of seconjdar p

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/.

t

/

.l 'f wat r quality w u d 'not be appropriate at this

.c; as 'it may rcve

.s 1

[

4

• to be wror (e.g., Beaver Valley Unit 1 d not limit s cific typ

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of s ere tube degradation, parti arly " dentin.

Besides, n

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faty Ys[Tk*gfg{ '

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unproven secondary water chemis ry parame:.er limits 4r,i..sna W W

Spec F

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-- - r P'.as may have an adverse effect.on the steam 4

h purity and cause potential failure of turbine componen(ts.27,29) is-NRC's H. : '?

It 1

.P-y

\\

l .4 objective to assure the integrity of these,tomponents and avoid the i

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occurrence of turbine missiles.

1.

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-/:4 2,'M Although NRC believes reliable water chemistry parameters and secondary l' 1) i 4

coolant controls from the industry will be forthcoming; in the interim, WA the staff position is that some form of monitor'ing is essential to

[f ensure lopg term steam generator tube integrity.(20 P :#: :,

RC

'S3

.;*Nj wouW receptive to alternate technical specification proposals, from

'a N

g il the utili ies>that will reflect monitoring or surveillance programs -

I with appropriate corrective act(ons to assure water quality control of

, f.y the Ph'R secondary coolant.

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