ML19262A356

Inservice Insp of PWR Steam Generator Tubes, June 1974, W/Effective Date 740901

ML19262A356
Person / Time
Site:	Crane
Issue date:	06/30/1974
From:	US ATOMIC ENERGY COMMISSION (AEC)
To:
Shared Package
ML19262A351	List: ML19262A350 ML19262A356
References
REGGD-01.083, REGGD-1.083, NUDOCS 7910260676
Download: ML19262A356 (5)

Text

June 1974

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U.S. ATOMIC ENERGY COMMISSION

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he,* REGULATORY GUIDE DIRECTORATE OF REGULATORY STANDARDS

'Is o REGULATORY GUIDE 1.83 INSERVICE INSPECTION OF PRESSURIZED WATER REACTOR STEAM GENERATOR TUBES A. INTPODUCTION of a LOCA, steam hne break accident, or simdar incident through the early detection of defects and detenoration General Design Cntena 14 and 31 of Appendix A by periodic inservice inspection. This guide apphes only

" General Design Critena for Nuclear Power Plants," to to pressunied water reactors (PWRs). The Advisory 10 CFR Part 50, " Licensing of Production and Utiliza.

Committee on Reactor Safeguards has been consulted tion Faedines." require that the reactor coolant pressure concemmg this guide and has concurred in the regu-boundary have an extremely low probability of abnor-latory position.

mal leakage. of rapidly propagating fadure, and of gross B. OlSCUSSION rupture. General Design Cntenon 15 requires that the reactor toolant system and associated auxdiary, control, The heat transfer area of the steam generators and protecnon >ystems be designed with sufficient margin to assure that the design conditions of the associated with pressurized water reactors can comprise coolant pressure boundary are not exceeded well over 50"e of the total primary system pressure.

reactor durmg any condinon of normal operation, incluiing retaining boundary. The thm-walled steam generator anticipated operanonal occurrences. Furthermore, Gen-tubing therefore represents an integral part of a major eral Design Cnterion 32 requires that components which barrier against fission product releae to the environ-v ment. The steam generator tu'ing also represents a are part of the reactor coolant pressure boundary be barner against steam release to the contamment in the designed to permit penodic mspection and testing of critical areas to assess their structural and leaktight event of a LOCA, and the integnty of this barner is related to its freedom from cracks, perforations, and integrity.

general deterioration. The design entena used to estab-Failurel of the steam generator tubes, which consti-lish the structuralintegrity of the steam generator tubmg tute a portion of the reactor coolant pressure boundary, should include definition of the minimum allowable tube wall thickness which can sustam the pressure and resultmg from stress corrosion cracking, wastage, or frettmg could permit release of radioactive matenals to thermal loading resulting from the worst postulated the secondary coolant system. In addition, the weaken.

LOCA in combmauon with a safe shutdown earthquake mg of these tubes due to the same processes could,in (SSE).2 the esent of a loss-of coolant accident (LOCA), result in fadure of tubes and release of the energy in the The chemical environment of the secondary side of secondary system into the containment. This guide the steam generator has been identified as the pnme desenbes a method acceptable to the Regulatory staff source of steam generator tube degradation and f dure.

for implemenung these critens with regard to mini-There is evidence that pnneipal factors m steam-side nuzmg the probability and consequences of massive corrosion attack are restricted flow areas that pernut propagatmn of steam generator tube fadures in the event 2As defined in Appendix A "Setsnuc and Geologic Snng Irmlure n detined as f ull penetranon of the pressure boundary Cntena for Nuclear Power Plants," to 10 CFR Part 100

" Reactor Site Critena."

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, oiber impunties thai ncv er ver the steam generator are detected by monitonng the secondary system for iluough som!cuser micakve. Thercior. water chemistry radioactivity through instrument analysis of steam or speubcatio m must take mto account matenals of boiler feed samples. Once leaks are detected they can wostius uon m the secondar~ rysiera, and the support-usually be located bv eddy current exammation of

.ng aaxikary shemical feed system must he designed to suspect tubing. The use of eddy currents as probing mantam halanced feedwe ou>lity to each steam media is based on the presence of defect caused vana-generator. Dunng normal operations as well as mactive tions in effective electncal conductivity and/or magreti, periods. effective momtonne rf water chemistry by permeabdity of the matenal being tested. The eddy means of in.ime contiruct:s enalytical instrumentation.

current probmg techruque has excellent sensitivity in supported by plant laboraic? samohng analysis, of nonmagnetic matenals, so that decreases in effective steam, condensate return,.in/ G edwater is necessary to conducuvity due to a discontmuity in a tube wall are ensure that water quality is r.o; s'egraded below accept-measured directly by increases m cod voltage in the able limits by such events as cr1 doser inleakage or probe. Eddy current orobes designed for testmg from themical feed syNem r.<cp*m St could promote the ipsitt. cre rmtable for steam generator tubing tube depadatwn.

inspecuon. Scannmg of steam generator tubes from the inside w1th an eddy current probe has proven successful Mechanical or now.incW nbritions can cause in locating defect areas in a faded tube and m ascertam-hetting or faugue daman to steam generator tubes ing the overall condition of the tubing in numerous which could also lead to tube failures.

operating PWRs.

A program of penodic inserve 'nspection of steam Radiography is an attemative method for inservice generaters is essenual in order & monitor the integrity inspection of steam enerator tubing. %1ule radiography of the tubing and to maintain surveillance m the event does not offer the flexibility of eddy current methods.it that there is evidence of mechanical damage or progres-can supplement eddy current testing for defect charac-sive detenoration due to des:gn, manufactunng errors, or terization on a limited basis.

thenucalimbalance. Inservice inspection of steam genera-tor tubing also provides a means of characteri7ing the nature and cause of any tube degradation so that Leaking tubes and tubes with unacceptable defe.m corrective measures can be tucn.

are taken out of service by blocking both ends of the tube in the tube shrt with plugs. Two methods are Inspecunn nd subseqt"; ors 0le repm-to steam available for pluggmg: (1) manually weldmg plugs and generator tubmg in acerating o' ants generally involves (2) explosive pluggmg.

poten nal radiation exposure to personnel. Pnor to under takmg such en inspection, careful pre-job planning required to assure that radiation axposures are Exnenence has indicated that each steam generator n

mentamed as low as practicatle. The use of temporary design has critical areas (e.g. crevices. lowCow areas. and hieldmg. decontammation. sorcial tooling, jigs and regions that allow steam blanketing) where, when the tistures for remo'e mspec* ion, snd other design and secondary water chemistry is not properly mamtamed, pvmedural consideratons as outlined in Regulatory attack and degradation of the steam generator tubes may Gui4 M. "Informauon Relevant to Maintaining Occu.

occur. Mechanical damage to steam generator tubes may pational Radiation Exposure as Low as Practicable also occur in those areas subject to tiow induced iNuclear Reactors)," should be considered prior to such vibrations. Typically, the number of tubes that are contamed m these entical areas constitute less than 201 ms pectmns.

of the total steam generator tubes.

This guide is ipplicable to current " typical" once-through and U-bend steam generators that use Ni.Cr Fe Preoperational inspections to establish a baselme and stamless steel tubing. The steam generator tubingis should examme all accessible steam generator tubes, and seamless, cold drawn, and annealed andis manufactured basehne inspecuons for operaung plants should sample and tested in accordance with spaci6 cations of American tubes on a random basis. Subsequent inspections should Souety of Mechanical Engmeers f ASME) and Amencan concentrate on any entical areas idenufied. so that hiety tbr inimg and Matenals( ASTM).

defects found in these regions will represent a sign 46 cantly high proportion of the total defects which may Addinon.d testmg of manufactured tubing consists of exist in the entire steam generator. This selection hydrostatic, eddy current, and ultrasonic tests. After method can be expected to result in a ratio of tube iube.to. tubed ce! welding is nerformed. the weld. are defects found to total tubes inspected considerably mspected muaily and by dye penetrant techniques and higher than the rauo of defective tubes to total tubes in finally leak tested.

the steam generator.

1485 163 I.83 2

C. REGULATORY POSITION

g. To the extent practical, the equipment used for eddy current testmg should be designed so that opera-A program for mscrvice inspecuon oisteam generator ton may he shielded or the equipment may he operated tubmg should be established and should include the as far from high rathation fic!ds as prathcable.

followmg featurcs:

h. Personnel either directmg or mterpretmg the re.

I Access for inspect. ion sults of the eddy cunent mspection should be tested and qualified in accordance with American Soacty for

2. Steam generators m pressunzed water reactors Nondestructive Testmg standard SNT TC IA and sup-should be designed so that mspection ofindividual tubes plemen ts.'

can be performed,

i. The examinations should be conducted usmg

b. Sutficient access should be provided for personnel wntren procedures.

to perform these mspections and tube plugging as required.

e Provisions for exammation shcald ensure that personnel radiation exposure is maintained as low as

a. Plants not having an operating license as of the pracucable.

effective date of this guide should undergo a preopera-1 Examination Equipment and Procedures tional inspection of 100% of the accessible tube area to establish the baseline condition of the steam generator

a. Inservice mspection should include nondestructive tubing. This inspection should be performed after the exammanon by eddy current testing or other equivalent field hydrostatic test and pnor to initial plant startup.

Such examinations should be conducted under condi-techniques. The equipment should be capable aflocating tions and with equipment and techmques equivalent to and identifymg defects due to stress cortcsion cracking and due to tube wall thinning by mechanical damage, those expected to be employed in the subsequent mservice examinations.

chemical wastage, or other causes.

b The inspecuon equipment should provide a sensi-

b. For operating plants, the first inspection per-tivity that wdl detect defects with a penetration of 20%

formed according to Regulatory Positions C.4 and C.5 or more of the nunimum allowable as manufactured should be considered as constituting the baseline condi-tube wall thickness.

tion for subsequent inspections.

e. A suitable eddy current inspection system should

c. The condition of the steam generator tubing at consist of (I) an internal sensing probe, (2) a two baseline and subsequent inspections should always be channel cddy current tester. (3) a viewing oscilloscope, compared to typical as-budt tubing.

H) a convenuonal two-channel stnp chart recorder,and t 5) a magneae tape data recorder.

4. Sample Selection and Testing

d. Test data should be stored and maintained for the operstmg life of the facility.

Selection and testing of tubes from each steam generator should be made on the basis of the following:

e. Standards consisting of similar as manufactured steam generator tubing with known defects should be

a. No fewer than 3% of the total number of steam used to establish sensitivity and for calibration. Refer.

ence flaws should simulate defects based not only on generator tubes should undergo eddy current exanuna-depth but also on length and shape if flaw and be tion dunng each inservice inspection. (see Regulatory Positions C.3 and C.6) charactenstic of pnor defect history.

f. The equipment should have the capabdity of

b. Tubes for the baseline mspection for operating examinmg the enure length of the steam generator plants should be selected on a random basis except that tubmg in once through desiens and. to the extent one. third of the tubes in U-bend designs should be practie.il, the U.hend area in U. bend designs.?

inspected from the cold. leg side of the generator.

3tn ree.uit to ibe icneth of tube to be exanuned, for U-hend SNT TC-1 A and Supplemen 6 "Recommerded Practice for ile wns, cntry f rom enbcr the hot leg ude or the cold-leg sade Nondest uctive Testmg Perso inel Quahficauon and Cerufica-mth samin. mon f rom the pomt of entry up to the nudpomt tion." Copies may be obtamet' from the Amencan Society for of the bend tor as slose to the nudpomt as practical) is Nondestructsve Testmg,914 Clucaro Avenue. Evanston.11hnois

.onudered suiresient to constitute a tube mstwuon.

60202.

1.33-3 1485 164

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c. Inspecuon of U bend design steam generators

(>57d further penetration of tubes with previous mdi-should rouanely concentrate on the hot leg side of the cations, the mspecuon frequency should be as de6ned m generator after the first two inservice inspections.

the ASME Code (three 40-month intervals in a 10-year period) except that the cold-leg side of U. bend steam

d. Es e r>

mspecuan subsequent to the baseline in.

generators may be inspected as m Regulatory Position spesuon should include all tubes which previously had C.6.d, below.

defect indicauons (not including plugged tubes) and should 10 consider tubes iri those areas (including the

d. If two consecuuve inspections of the cold. leg side cold leg de) where design and experience have indi.

of U-bend steam generators result in no addinonal tubes ested potential problems.

with detectable wall penetration (>:0"a and no signi6 cant (>5%) further penetration of tubes with previous

5. Supplementary Sampling Requirements indicatiois, the inspection mterval may be extended to 10 year penods for cold-leg tubes.

If the eddy current inspection pursuant to Regu.

a 5

latory Position C.4 indicates that more than 10% of the

e. Unscheduled inspections should be conducted in mspected tubes have detectable wall penetration (>20%)

the event of pnmary to secondary leaks which exceed or that one or more of the mspected tubes have an technical specificauons, a seisnue occurrence greater mdication of an unacceptable defect (see Regulatory than an operating basis earthquake.2 a loss.of coolant Posinon C.7.a), (1) the steam generator should be accident requinng actuation of engmeered safeguards. or considered unacceptable for continued service until a major steam line or feed water ime break.

additional examinaticns are conducted and (2) an additional 3% of the tubes should be inspected, concen.

7. Acceptance Limits tratmg on tubes in those areas of the tube sheet array where tubes with defects were found.

a. An unacceptable defect is defined as one which would result in not satisfymg the calculated acceptable

b. If in the inspection made in Regulatory Position minimum tube wall thickness that can sustam a LOCA in C.S.a12) above, more than 10% of the inspected tubes combination with a safe shutdown earthquake.

have detectable wall penetration (>20%) or one or more of the mspected tubes has an indication of an unaccept.

b. If in the inspection performed under Regulatory abic defect, additional tubes (no less than 3% of the Position C.4,less than 10% of the tubes mspected have

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total tubes in the steam generator) in the area of the detectable wall penetration (>207c) and no tube has an defect should be inspected.

unacceptable defect, plant operation may resume.

6. Inspection Intervals

c. If in the inspections performed under Regulatory Position C.5,less than 10% of the total tubes inspected Scheduled inservice inspection of steam generators have detectable wall penetration (>20%) and no more J.

should be performed at intervals of not less than 12 or than three tubes have unacceptable defects. plant opera-more than 20 eaiendar months, except that the first tion may resume after required correcuve measures have scheduled inspection tfter the baseline inspecuon should been taken.

be at the first extended outage but should not be made before o months of operation, and the 20-calendar.

d. If in the inspections performed under Regulatory month mterval should not be exceeded.

Position C.5, more than 10% of the total tubes inspected have detectable wall penetration (>207d or more than

b. Inspecuons may be rnade coincident with refueling three of the tubes inspected have unacceptable defects.

outages or any shutdown for plant repair and mainte.

the situation should be immediately reported to the nance in accordance with the American Society of Commission in accordance with the facility license for Mechanical Engineers ( ASME) Boiler and Pressure Vessel resolution and approval of the proposed remedial action.

Code.Secuon XI.6 Additional samphng arid more frequentinspections may be required.

c. If two consecuuve mspections, excluding the baseline inspecuon, result in no additional tubes with

8. Corrective Measures detectable wall penetration (>20%) and no significant All tubes with unacceptable defects should be "In H mspectiont previoudy degraded tubes that exhibit plugged.

ugndiant D5H furiher wall penetrauon must be included m

9. Reporting

• llerematier referred to an ASME Code. Copws may be obtamed irom the Amencan Soacty of Mccharucal Engneers. United The results of the inservice inspection should be t ngincenng Center 145 lat 47th Street, New York, N.Y.

included in the Semiannual Operatmg Reports desenbed intH 7 1.83-4 1485 165

m Regulatory Guide 1.16, " Reporting of Operating the recommendations of Regulatory Poynom C and C.7.b.

h. for mation."

D. IMPl.EMENTATION

c. Operating plants wiuch had special mse mcc mspection requirements related to steam generaton The purpose of this section is to provide guidance to imposed by the Commission pner to the effective date applicants and licensees regarding implementation of an of this guide may be considered to have initiated acceptable scnedule for inservice inspection of steam implementation of this guide if the last inspectmn under generator tuoes of operating p' ants. Other programs of the special program meets the recommendations of mspection of tubes proposed to the Commission by Regulatory Position C.7.b. The last of the special applicants and licensees may be determmed to be inservice inspections may be considered a cascime acceptable if they provide a comparable level of inspec-inspection for subsequent mspections.

tion.

d. Inspections subsequent to the baselme mspecticn

1. The effective date of this guide is September 1,1974.

should be implemented accerding to the recommenda-tions of Regulatory Position C.6.

2. Operating plants should implement the baseline in-spection reccmmendations of Regulatory Position C.3.b

3. P ants not havmg an operating license as of the at the first estended outage, but within a period not to effective date of this guide should impkment the esceed twelve months after the effective date of this preoperational inspection recomniendations of Regu-latory Position C.3.a except that those plants scheduled guide.

for commercial operation within the 120-day penod

4. Operating plants which have their first extended after the effective date of this guide may forgo the outage scheduled withm a 120-day penod after the preoperational baseline inspection if an mservice inspee-effective date of this guide may perform the recom-tion cannot be scheduled prior to commercial operation.

mended mspection at the next scheduled outage.

These plants should meet the recommendations of paragraph D.2 above.

b. Operating plants which have had an inservice inspection of at least 3% of the total tubes in each steam

4. Technical specifications for assunng mspection and generator withm the 12. month penod prior to the reporting as recommended in Regulatory Position C v

effective date of this guide need not undertake a baseline should be incorporated in operating licenses as soon as mspection if the inspection methods and results meet practical.

b 1.83-5 1485 166