WATER LANCING OF BRUCE-A UNIT 3 AND 4 STEAM GENERATORS

CANDU MAINTENANCE CONFERENCE 1995

WATER LANCING OF BRUCE-AUNIT 3 AND 4 STEAM GENERATORS

Frank V. PuzzuoliOntario HydroNuclear Technology Services700 University AvenueToronto, OntarioM5G 1X6(416)592-5633

Brent MurchieOntario HydroBruce Nuclear Generating Station AProjects and Modifications GroupP.O. Box 3000Tiverton, OntarioNOG 2T0(519)361-2673

Steve AllenOntario HydroBruce Nuclear Generating Station AProjects and Modifications GroupP.O. Box 3000Tiverton, OntarioNOG 2T0(519)361-2673

ABSTRACTDuring the Bruce-A 1993 Unit 4 and 1994 Unit 3 out-ages, three water lancing operations were carriedout along with chemical cleaning as part of the sta-tion boiler refurbishment program. The water lancingactivities focused on three boiler areas: 1) supportplates to clean partially or completely blocked broachholes and prevent boiler water level oscillations, 2)hot leg U-bend supports (HLUBS) to removedeposits contributing to boiler tube stress corrosioncracking (SCO and 3) tube sheets to dislodge sludgepiles that potentially threaten boiler tube integrity andto flush out postchemical cleaning insolubleresidues.

The combination of water lancing and chemicalcleaning effectively reduced broach hole blockagefrom up to100% to 0-10% or less. As a result, boil-ers in Units 3 and 4 will operate for some time tocome without concerns over water level oscillations.However, deposits remained in most tube supportplate land areas.

For Units 3 and 4, the prechemical clean lancingoperations had limited success in dislodging HLUBSdeposits; although some deposit from the scallop barsurfaces was removed, hour glass areas remaineddirty. The postchemical clean lancing activities weremore effective in removing surface deposits fromthe HLUBS in Unit 3 boilers. This was mainly due tothe longer iron step performed during the Unit 3 boil-er chemical clean. Inspections carried out afterchemical cleaning and water lancing in either unit,showed that most hour glass areas remained filledwith deposit.

Water lancing of the Unit 4 boiler HLUBS in 1995,dislodged much of the scallop bar deposit left behindin 1993, but did not succeed in cleaning hour glassareas. Visual inspections performed on Unit 4HLUBS in 1995 revealed significant scallop bardegradation in Boilers 2 and 7, and relatively less

scallop bar decay in Boilers 1,3, 5 and 6; in Boilers 2,3, 6 and 7, degradation areas not identified during thefinal inspections in 1993 were found. The 1995inspections also showed far more scallop bar decayin the Boiler 2 HLUBS compared with the other Unit4 boilers.

Tube sheet lancing activities in Unit 4 after chemicalcleaning, effectively removed about 275 kg of wetsludge per boiler. The cold leg and outer hot leg areaswere cleaned down to the tube sheet, with thindeposits remaining in the original location of thesludge pile. In the hot leg central areas, hard tubedeposits did not allow lances to travel farther downthan 12.7-30.5 cm (5-12 inches) above the tube sheetand prevented tube sheet inspections in these areas.Attempts to remove the hard, tenacious tube scaleby water lancing did not succeed.

In Unit 3, the tube sheet lancing operations beforechemical cleaning removed about 222 kg of tubesheet sludge per boiler, while the postchemical cleanactivities dislodged roughly 109 kg of chemical clean-ing insolubles from each boiler. As in Unit 4, the coldleg and outer hot leg areas were cleaned to the tubesheet and hard tube collars were left in the centralhot leg areas; nearly all the hard tube collars presentbefore chemical cleaning were unaffected by thechemical cleaning process. This is thought to haveresulted from shielding of the tube collars by therapid build up of insoluble residues on the tubesheets during chemical cleaning.

1. INTRODUCTION

1.1 Bruce-A Steam Generator Features

The Ontario Hydro nuclear generating system con-sists of twenty pressurized heavy water reactorsspread over three sites: the Pickering, Darlington andBruce stations. The Bruce Nuclear PowerDevelopment in Tiverton. Ontario is the location of

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eight reactors, with the Bruce-A station housingUnits 1 to 4. Bruce-A Unit 2 started operations inJanuary of 1977 and the remaining units were in ser-vice by January 1979. Each Bruce-A unit has a gen-erating capacity of 760 MWe.Every unit at Bruce-A has eight recirculating boilersarranged in an east and west bank. The west andeast banks are made up of Boilers 1-4 and Boilers 5-8 respectively. Each bank of four boilers is connect-ed to a common steam drum, a feature unique to theBruce-A station. Individual boilers are 2.44 m (96inches) in diameter and contain 4200 tubes madefrom Inconel 600. The tube outer diameter and wallthickness are 1.30 cm (0.51 inches) and 0.11 cm(0.04 inches) respectively. Figure 1 shows a cutawayview of a Bruce-A boiler.

Within every Bruce-A boiler, there are seven 2.54 cm(1 inch) thick carbon steel support plates to help sup-port the tube bundle. The plates are numbered inascending order and are spaced about 89 cm (35inches) apart. Each plate contains trefoil broach holesthat allow steam and water to flow through the boil-er (See Figure 2). Broach holes are arranged in a 2.03cm (0.8 inch) triangular pitch pattern, with tube laneslocated at 30°, 90° and 150° relative to the no-tube-lane (NTL) (See Figure 3). Tube lanes are a nominal0.47 cm (0.18 inches) wide, while the NTL is about6.85 cm (2.7 inches) wide and has 4 tie rods along itscenter. Additional tie rods are located within the tubebundle. The tie rod pattern shown in Figure 3 iscommon to support plates 1 to 7.

Above support plate 7, there are three supports inthe U-bend area: one at 90° and the others on the hotand cold leg sides at 40°, to the horizontal. Nine car-bon steel arched bars tie together all three supports.Each of the carbon steel scallop bars making up thesupports is 1.27 cm (0.50 inches) wide and 1 cm(0.40 inches) high. During the U-bend supportassembly, the scallop bars were first stacked andthen drilled with tube location holes. Individual holeswere chamfered on both sides with about a 20°included angle, leaving a tube land or hour glass arearoughly 0.25 cm (0.1 inches) wide (See Figure 4). Asa result, each bar has half-tube scallops alternatingfrom top to bottom.

Scallop bar stacks are held together at the edge by aseries of short studs and through the center with car-bon steel clamping plates called forks. There are 6fork assemblies in each stack. None of the three U-bend supports hold tube rows 1 to 14. The 90° sup-port holds tube rows 15 to 95, while both 40° sup-ports hold tube rows 42 to 95 as shown in Figure 5.

The tube sheet is a 2.52 m (99 inch) diameter carbon

steel plate that is 36.8 cm (14.5 inches) thick in thetube region (See Figure 1). There are no tie barseither in the tube bundle or the NTL between sup-port plate 1 and the tube sheet. The tube pattern isotherwise identical to that of support plates 1 to 7(See Figure 3).

1.2 Steam Generator Cleaning Methods:Water Lancing and Chemical Cleaning

Over 1989 and 1990, boiler water level oscillationsobserved in Unit 2 and in Unit 1 led to unit deratings.The oscillations resulted from broach hole blockagecaused by a buildup of secondary-side deposits.Subsequent boiler problems also linked to thebuildup of secondary-side deposits are stress corro-sion cracking (SCO of boiler tubes in the U-bend areaand scallop bar degradation. Another potential prob-lem arising from deposit buildup is crevice formation.Within crevices, non-volatile feedwater componentscan collect and create localized, aggressive corrosionenvironments. This localized corrosion could result inboiler tube pitting and eventual failure.

Secondary side deposits in Bruce-A boilers typicallycontain 30-35% iron (mostly as Fe3O4), 35-45% cop-per (mostly as metallic Cu), 5-10% Zn (as ZnO), 1-5%Ni (as NiO) and minor amounts of other metallicoxides. Two integrated methods are used at OntarioHydro to remove these types of boiler deposits:chemical cleaning and water lancing. The chemicalcleaning method is based on the Electric PowerResearch Institute/Steam Generators Owners Group(EPRI/SGOG) process which involves the use of twosolvents: one to dissolve copper deposits and theother to remove iron oxides. Zinc and other metalsfound within deposits are also removed by thismethod. At the Pickering station, boiler chemicalcleans were part of maintenance activities in severalunit outages: Unit 5 in 1992, Unit 6 in 1993, Unit 1 in1994 and Unit 2 in 1995. Chemical cleans were alsoperformed during the Bruce-A 1993 Unit 4 and 1994Unit 3 maintenance outages.

The effectiveness of the chemical cleaning processdepends on deposit thickness and hardness.Although chemical cleaning effectively removes thindeposits typically found on boiler tubes, it does noteffectively penetrate and remove thick deposits likethose found on tube sheets. High pressure waterlancing is necessary to remove the bulk of the hard,thick material beforehand. The amount of hard mate-rial removed by water lancing is limited by sludgeaccessibility and hardness, and lance operating pres-sures as determined by qualification tests. Afterremoving as much bulk deposit as possible by waterlancing, the remaining thinner deposits can react

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more effectively with the chemical cleaning solvents.After chemical cleaning, low pressure water lancingis required to flush insoluble residues from the tubesheets.

To date, Ontario Hydro has used high pressure waterlancing systems for the following boiler cleaningoperations (at the stations shown in parentheses):1,2

1) Removal of tube sheet sludge piles to reduce therisk of under deposit corrosion and pitting(Pickering Units 1, 2, 5 & 6, Bruce-A Units 3 & 4and Darlington Unit 4).

2) Cleaning of broach holes (or lattice supports) par-tially or completely blocked with deposits torestore steam and water flow (Bruce-A Units 1, 2,3 & 4 and Pickering Units 1,2, 5 & 6).

3) Removal of deposits from the hot leg U-bend sup-ports (HLUBS) to reduce the risk of boiler tubestress corrosion cracking (SCO (Bruce-A Units3&4) .

The history of water lancing operations at OntarioHydro will not be discussed here but has been cov-ered in References 1 and 2.

Along with boiler chemical cleaning, the Bruce-A1993 Unit 4 and 1994 Unit 3 outages included highpressure water lancing operations to clean boilerbroach holes, HLUBS and tube sheets. For the 1995Unit 4 outage, HLUBS water lancing was repeated toremove deposit left behind after the 1993 outage.This paper will focus on each of these water lancingoperations with emphasis on equipment develop-ments and the results achieved.

2. LANCING STRATEGY AND RESULTS

2.1 Support Plate Water Lancing

2.1.1 Background

Boiler water level oscillations in Unit 2 provided thefirst signs of broach hole blockage in Bruce-A steamgenerators. However, a chemical cleaning processhad not been qualified for use at Bruce-A in the late1980s. As a result, high pressure water lancing waspursued as a viable short-term solution to cleanbroach holes and restore steam and water flow.

The water lancing operations performed on Unit 2boilers over 1989 and 1990, and on Unit 1 boilers in1990, involved the use of thin, flexible intertubelances developed by Babcock and Wilcox Ltd.(B&W). The water lances were constructed of stain-less steel pressure tubing encased in a rigid plastic(Refer to Figure 6 ) and were typically operated at10,000 psig (nozzle pressure). Since the lances hadlimited flexibility, they could only be inserted into 30°

tube lanes with the help of an adjustable guideplaced in the NTL through an external port. At best,this method allowed access to about 65% of thesupport plate areas. Despite the limited coverage,water lancing of the upper 2 support plates (6 & 7)removed enough broach hole deposit to restore Unit2 from a derated power of 73% to full power opera-tion. A similar approach followed about a year lateralso enabled Unit 1 to return to full power operation.

Throughout 1992, water level oscillations in Unit 4boilers indicated support plate blockage. As a result,the planned outage in 1993 included support platelancing as a maintenance activity. Since the supportplate lancing operations carried out on Units 1 and 2,B&W made several changes in the lance design toimprove lance flexibility. Two particular changesenhanced lance flexibility and made it possible toenter 90° tube lanes.

1) Replacement of stainless steel tubing withKevlar™ wrapped flexible tubing.

2) Substitution of the rigid plastic around the tubingwith a more pliant material.

Improvements in nozzle design and construction ledto increased cutting effectiveness. Lances withthese design features were first used during tubesheet lancing operations at Pickering Unit 5 in 1992.

The strategy for support plate cleaning in Unit 4 was to:

1) Use flexible lances to enter 90° tube lanes via theNTL with an adjustable 90° lance guide. By thismethod, about 83% of the support plate areacould be water lanced. The remaining 17% is notaccessible because of tie rods in the NTL andwithin the tube bundle.

2) Clean two support plates simultaneously from aport at the midspan distance (17.5 inches or 44.5cm) between them. For the lancing operationspreviously carried out in Units 1 and 2, the portswere located close to support plates 5, 6 and 7,which were the only support plates to be waterlanced. However, inspection and/or water lancingactivities were planned for all seven boiler supportplates in Unit 4. It was expected that there wouldbe a considerable time saving by cleaning 2 sup-port plates simultaneously. Consequently, portsaligned with the NTL were installed between thefollowing pairs of support plates: 1 & 2, 4 & 5 and6 & 7. Inspection/lancing ports for support plate 3(where required) were placed closer to this sup-port plate because of interference from the blow-down ring header (See Figure 1).

3) Perform visual inspections on all support plates.Support plates with nominally <40% broach hole

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blockage were not lanced since it was believedthe chemical cleaning solvents would effectivelydissolve these thin deposits (See footnotebelow1).

Access to support plates 1 & 2 for inspection and/orwater lancing required a man way to be cut into theboiler containment bellows (See Figure 1). A tempo-rary containment seal was being developed for thispurpose, but was not available until after the Unit 4boiler chemical cleans in 1993. However, contain-ment seals were installed early in the Unit 3 outagein 1994 to permit inspections and/or water lancing ofsupport plates 1 & 2 and tube sheets before andafter chemical cleaning.

2.1.2 Support Plate Lancing ResultsTables 1 and 2 summarize the pre- and postchemicalclean support plate lancing data for Units 4 and 3respectively. Lances were operated at nominally8,000 psig (nozzle) to reduce the risk of lance fail-ures. On average, about 95% of the target supportplate areas were accessed in both units where waterlancing was required: Sections 2.1.2.1 and 2.1.2.2below describe results of the lancing operations inUnits 3 4.

2.1.2.1 Unit 4Prelancing visual inspections showed broach holeblockages ranging from 30 to 100% for supportplates 3 to 7. Water lancing of support plates withnominally >40% broach hole blockage, usuallyreduced blockage to 0-10%; at worst, 10-20%remained in a few locations. In contrast, thepostchemical cleaning inspections of the same sup-port plates revealed 0-5% broach hole blockage forthose plates previously water lanced, with 0-10%blockage left in a few areas (See footnote below 1).The same inspections of support plates that had<40% blockage before chemical cleaning and werenot lanced, showed a blockage reduction to 0-10%.However, the tube land areas were not cleaned.

The postchemical cleaning conditions of supportplates 1&2 depended on the length of the ironremoval step during the chemical clean. Broach holeblockages did not exceed 0-5% in Boilers 5-8, whichwere subjected to a 40-hour iron removal step. Incontrast, the iron step during the west bank cleanwas stopped after 8.5 hours due to corrosion con-cerns. This left some areas of support plates 1 &2 inBoilers 1-4 with up to 100% broach hole blockage.

Water lancing reduced blockage to 10-20% or less inthese regions (See Table 1). The tube land areas ofsupport plates 1 & 2 in either bank remained filledwith deposit.

2.1.2.2 Unit 3

Based on the Unit 4 support plate lancing data, It wasfelt that the requirement for lancing individual sup-port plates before chemical cleaning could bechanged to >60% broach hole blockage comparedwith >40% for Unit 4. The rationale for this changewas modification of the Unit 3 chemical cleaningsequence to include a 100-hour iron step, comparedwith 8.5 and 40-hour iron steps for the Unit 4 westand east banks respectively in 1993. The longer ironstep was expected to improve deposit removal.

Visual inspections performed before lancing showedsupport plates in Unit 3 boilers to be much cleanerthan they were found in Unit 4 a year earlier. Onlysupport plates 1, 2 & 7 in a few Unit 3 boilers had>60% broach hole blockage (See Table 2). Waterlancing reduced broach hole blockage in theseregions to 10-20% or less. Postchemical cleaninginspections of support plates that were either lancedor originally had <60% blockage and were notlanced, usually showed blockages of no more than 0-10%; the most blockage seen was 10-20% on thehot leg side of support plate 5 in Boiler 6 (See Table2). Deposits remained in the tube land areas as inUnit 4 a year earlier.

2.2 HLUBS Water Lancing

2.2.1 Background

Stress corrosion cracking (SCO of boiler tubes in theHLUBS area is attributed to:

1) High local mechanical stresses due to supportstack growth. The growth is caused by accumu-lation of corrosion products between scallop bars.

2) A boiler tube material (I-600) susceptible to SCC.

3) Accumulated deposits that can promote a corro-sive environment.

When evaluating options for removing HLUBSdeposits from the Unit 4 boilers in 1993, it wasbelieved that chemical cleaning alone would not beeffective. Water lancing was considered a viableapproach because of previously successful applica-tions in tube sheet cleaning at the Pickering station in1992 and 1993, and support plate cleaning at Bruce-A Units 1 and 2.1,2,3

1 Broach hole blockages are "by eye" estimates from fibrescope inspections. A range of 0-5% indicates broach holes with an as newappearance, while a 0-10% range represents the case where broach holes were clean with a small percentage left with minordeposits. All other ranges show the average blockage observed.

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Before 1993, the only other attempt to water lancethe HLUBS area was made during a trial carried outduring the Bruce-A Unit 2 outage in 1992. The trialinvolved use of lancing equipment designed for oper-ation from inside the steam drum and did not suc-ceed for 2 reasons:

1) Heavy tube deposits prevented water lancesfrom entering the target tube lanes. The depositscould not be removed despite repeated attemptsto clear tube lanes with tube cleaning or "straightahead" lances.

2) Equipment problems along with worker radiationdose limits did not allow prolonged work insidethe steam drum.

The approach completely changed when during the1993 Unit 4 outage, a decision was made to utilizethe small gap between tube rows 14 and 15.Babcock and Wilcox Ltd. (B&W) received a contractto develop manually operated equipment that couldenter this gap through an external boiler port. Theequipment was designed to rotate and allow lancingof the HLUBS top and bottom sides via 90° tubelanes. Flexible water lances similar to those used forsupport plate cleaning were used. Figure 7 illustratesa few of the lancing equipments features.

To reduce dose uptake and shorten the water lancingschedule during the 1994 Unit 3 outage, Bruce-Acontracted B&W to develop automated U-bendwater lancing equipment. Several automated systemfeatures shown in Figure 8 are:

1) Separate drives for lance and guide movement,and setting the lance angle. All drives are remote-ly controlled by computers placed in a controlarea outside the boiler room.

2) Computer generated readouts of guide position,lane numbers, lance angle and lane coverage.

3) Newly developed water lances similar to thoseused during the 1993 Unit 4 operations. Thenewer lances contained six Kevlar™ wrappedpressure tubes instead of seven. This allowedholes necessary for coupling the lance to thelance drive, to be placed along the center of thelance.

The automated system was also used during the1995 Unit 4 outage.

2.2.2 HLUBS Lancing Results

Table 3 summarizes the "as left" boiler HLUBS con-

ditions for Unit 4 in 1993 and 1995, and Unit 3 in1994. For the initial Unit 4 cleaning activities in 1993,the nominal lance operating pressure was about6,500 psig (nozzle). Based on qualification tests runbefore the Unit 3 outage, the lance operating pres-sures were raised to 8,000 psig (nozzle) for the 1994Unit 3 and 1995 Unit 4 HLUBS water lancing opera-tions. Sections 2.1.3.1 and 2.1.3.2 describe theresults of HLUBS lancing operations in both units.

2.2.2.1 Unit 4

In 1993, coverage of the HLUBS top and bottomsides in Unit 4 boilers varied from 65-99% becauseof lane access restrictions. Visual inspections identi-fied misaligned tubes as the cause of the accessconstraints; other restrictions were not apparent.This was not surprising since additional HLUBSinspections showed bent or broken forks and studsthat likely resulted from stack height growth.

For the east bank boilers, water lancing before chem-ical cleaning had limited success; although somedeposit was removed from the scallop bar surfaces,most hour glass areas remained dirty. The lancingoperations after chemical cleaning removed moredeposit from scallop bar surfaces, but left most hourglasses filled with deposit. Postlancing inspectionsshowed about 30-60% scallop bar surface exposureon the top side and roughly 60-80% surface visibilityon the bottom side (See footnote below2).

Compared with the east bank boilers, postchemicalclean lancing of the west bank boiler HLUBS wasless effective in Boilers 1 to 3. In Boiler 1, HLUBS topand bottom side surface exposures after water lanc-ing were 0-50% and 0-90% respectively, whileBoilers 2 and 3 had respective top and bottom sidesurface exposures of 0-10% and 0-50%. Boiler 4 wasthe cleanest west bank boiler with surface expo-sures of 80-90% and 60-80% for the HLUBS top andbottom sides (See Table 3). Most hour glass areas inthe west bank boiler HLUBS remained filled withdeposit.

The difference in lancing effectiveness after chemi-cal cleaning for the east and west bank, depended onone or both of the following:

1) West bank boilers were not water lanced beforechemical cleaning. The west bank had beenchemically cleaned by the time a HLUBS port(aligned with the gap between tube rows 14 and15) was installed on each boiler. As a result, the

2 All reported inspection data are based on visual estimates of surface cleanliness. The ranges reported represent the maximum andminimum surface exposure observed. For example, a range of 40-80% means that one lane had a surface exposure of 40% and anoth-er lane showed 80% surface cleanliness; surface exposures for the remaining lanes fell between the two values.

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HLUBS deposits in Boilers 1 to 3 probablyremained thick enough to prevent effective pene-tration and removal by the chemical cleaning sol-vents.

2) The iron removal step was stopped after 8.5hours during the west bank clean to stay withinthe preset corrosion limits, while the east bankunderwent a 40-hour iron step.

Visual inspections done after chemical cleaning andwater lancing also showed small holes in the scallopbars of a few Unit 4 boiler HLUBS examined. Theseholes were the result of localized corrosion.

Due to the limited success in removing HLUBSdeposits from Unit 4 boilers, the water lancing oper-ations were repeated during the 1995 Unit 4 outage.By this time, B&W developed an automated lancingsystem that had already been used for the 1994 Unit3 outage. For the 1995 Unit 4 operations, B&W mod-ified the water lances by offsetting the cutting noz-zles about 50 from the vertical to focus the water jetsonto the hour glass areas.

Based on the 1993 experiences, the initial plan wasto perform visual inspections on one boiler per bankbefore water lancing and for all boilers afterwards.Water lancing operations were started on Boilers 1and 2, while carrying out prelancing visual inspec-tions of Boiler 3 in parallel. The Boiler 3 inspectionsshowed the HLUBS top and bottom sides to be dirtywith almost no visible scallop bar surface.Postlancing inspections of Boiler 1 revealed about 75and 85% surface visibility for the HLUBS top and bot-tom sides respectively. After lancing, the Boiler 2HLUBS had 5% or less surface visibility on the topside; inspections of the bottom side could not be car-ried out because of lane access restrictions.

An unexpected finding during the Boiler 2 postlanc-ing inspection was missing scallop bar sectionsbetween lanes 31 and 82. This was not seen duringthe final inspections in 1993 and forced an immedi-ate reassessment and expansion of the Unit 4 out-age plan and scope. An additional refurbishmentactivity resulting from the Boiler 2 condition evalua-tion, was antivibration bar (AVB) installationsbetween the 90° and hot leg U-bend supports on allUnit 4 boilers. The U-bend water lancing and inspec-tion program was revised to include:

1) Pre- and postlancing inspections on all boilerHLUBS that had not been water lanced (Boilers 3to 8) when the missing scallop bar pieces inBoiler 2 were discovered. This would identifyHLUBS degradation on the remaining Unit 4 boil-ers and in combination with activity 2) below,

help assess the benefits or drawbacks of waterlancing.

2) Inspections of the hot leg area on top of supportplate 7, in Boilers 2 and 7, for missing scallop barpieces. The 1995 inspections of the Boiler 2 and7 HLUBS revealed areas of scallop bar degrada-tion besides those seen during the final inspec-tions in 1993. However, the HLUBS inspectionsin 1995 showed far less deterioration in Boiler 7compared with Boiler 2. The results from the sup-port plate 7 inspections, before and after HLUBSlancing, would help to learn if water lancingcaused the scallop bar degradation in Boiler 2.

3) Installation of a nozzle to allow inspection and ifnecessary, water lancing of the Boiler 2 cold legU-bend support (CLUB). This also enabled inspec-tors to look for debris on the top side of the sup-port plate 7 cold leg area. The Boiler 2 HLUBScondition prompted concerns about possibleCLUBS degradation in all Unit 4 boilers.Inspection data from Boiler 2 were used to decidethe need for CLUBS nozzles on the remainingUnit 4 boilers.

4) Submitting any scallop bar pieces collected fromthe hot leg area on top of support plate 7 in Boiler2, to Ontario Hydro Technologies (OHT) for chem-ical analysis. The analytical results were used todetermine the extent of scallop bar corrosion.

The results of these additional operations were:

1) Pre- and post lancing HLUBS inspections forBoilers 3-8 showed no evidence of deteriorationcaused by water lancing. The HLUBS bottomsides in all east bank boilers were clean and werenot water lanced. Scallop bar erosion was seen inall eight boilers and small holes were found inBoilers 1, 3, 5, 6; Boilers 3 and 6 had a few addi-tional holes in the degradation area identified dur-ing the 1993 inspections.

Boiler 7 had many holes and several missing scal-lop bar sections between lanes 50 and 66, but farless scallop bar degradation than in Boiler 2. Theextent of scallop bar deterioration found in Boilers1,3, 5 and 6 was far less than observed in Boilers2 and 7.4 For Boilers 3-8, the postlancing condi-tions of the HLUBS top and bottom sides weresimilar to that of Boiler 1: roughly 70 and 80%surface visibility on the top and bottom sidesrespectively with few visible hour glass areas.

2) In Boiler 2, debris was found in the central hot legarea on top of support plate 7. Babcock andWilcox Ltd. quickly designed, built and qualified amanually operated flushing lance to remove most

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of the debris. Inspections of the same area inBoiler 7, before and after HLUBS water lancing,revealed no noticeable increase in debris levels.Later inspections of the hot leg on top of supportplate 7 area in Boiler 4, also showed no significantdebris buildup after HLUBS water lancing.

3) Visual inspections of the Boiler 2 CLUBS revealedthat the bottom side was clean with no apparentdegradation and the top side was covered withdeposit. Hour glass areas were not visible oneither side. The cold leg area on top of supportplate 7 had only a few pieces of loose tube scale.Based on these inspection data, only the CLUBStop side was water lanced. Postlancing inspec-tions of the CLUBS top side showed about 75%scallop bar surface visibility, with no signs ofeither scallop bar degradation or clean hour glass-es.

4) Chemical analysis done at OHT showed that thedebris collected from the hot leg area on top ofsupport plate 7 in Boiler 2 was solid magnetite,i.e., a corrosion product.

Based on these findings, it is unlikely that water lanc-ing contributed to the observed HLUBS scallop bardegradation found in Unit 4 boilers. Furthermore, theCLUBS conditions in the other Unit 4 boilers areprobably as good as or better than that of Boiler 2.

The 1995 lancing operations removed much of thesurface deposit left behind on the Unit 4 HLUBS in1993 (See Table 3), but did succeed in dislodginghour glass deposits.

2.2.2.2 Unit 3

Based on the 1993 Unit 4 results, HLUBS lancingwas carried out before and after chemical cleaning toincrease deposit removal. It was believed that includ-ing a 100-hour iron step in the chemical cleaningprocess would improve scallop bar deposit removal,compared with the1993 Unit 4 clean where shorteriron steps were carried out.

The prechemical cleaning lancing results were simi-lar to those achieved for Unit 4 in 1993; water lanc-ing removed enough deposit to expose part of thescallop bar surface including a few scallop divisions,but did not clean hour glass areas. Coverage of thetarget 90° lanes ranged from about 63 to 99% due toaccess restrictions. As in Unit 4 the previous year,misaligned tubes were identified as the primarycause of the access constraints.

A general inspection carried out from inside thesteam drum just after chemical cleaning but beforewater lancing, revealed the Unit 3 boilers HLUBS tobe cleaner than those in Unit 4 after the 1993 chem-

ical clean. This is attributed to the longer iron step inthe Unit 3 clean. Prelancing lane inspections per-formed after chemical cleaning for one boiler in eachbank, showed clean tube surfaces except areas justabove the scallop bar where dark deposits remained.These deposits covered most hour glasses and scal-lop bar surfaces on the HLUBS top and bottom sides.The bottom side appeared cleaner than the top side.

Postlancing HLUBS inspections in Unit 3 after chem-ical cleaning revealed:

1) Scallop bar surfaces that appeared much cleanerthan after the prechemical clean lancing opera-tions. About 50% of the scallop bar surface wasexposed on the top side. In contrast, the HLUBSbottom side had about 80% surface visibility (SeeTable 3).

2) A red surface oxide on most exposed scallop barsurfaces on the top and bottom sides. The lightsurface oxide likely formed after water lancing.

3) Tube deposit collars that filled most hour glassesand extended a few millimeters above the scallopbars on the HLUBS top sides. The HLUBS bottomsides in four boilers had more cleaned hour glassareas than the top sides.

4) No sign of scallop bar degradation or deformationsuch as was found in Unit 4 during the 1993 or1995 outages. This was not surprising since themeasured HLUBS stack growths for Unit 3 wereless than those in Unit 4

For both the HLUBS top and bottom sides, coverageof the target 90° tube lanes increased about 12%after chemical cleaning. This likely resulted from theeffective removal of tube deposit by the chemicalcleaning solvents.

2.3 Tube Sheet Water Lancing

2.3.1 BackgroundThe first production tube sheet lancing operations atOntario Hydro occurred during the Pickering Unit 5outage in 1992. Through-wall pitting and boiler tubeleaks in tube sheet areas where hard sludge pileshad collected, resulted in a forced outage. Manuallyoperated equipment designed and built by B&W wasused to remove as much tube sheet sludge as pos-sible. The lancing operations focused on removingsludge from the tube sheet hot leg areas that wereaccessible from a boiler port aligned with the NTL.Tube sheet coverage was limited by the tie rodswithin the tube bundle.

Similar lancing operations were carried out atPickering Unit 6 in 1993 and resulted in significantlyincreased tube sheet coverage compared with the

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Pickering Unit 5 operations a year earlier. This wasdue to the installation of 2 additional lancing ports onall Unit 6 boilers: one at 50° and another at 130° rel-ative to the NTL. Automated lancing systems laterdeveloped by B&W were successfully used duringoutages at Pickering Units 1 and 2 in 1994 and 1995respectively, and at Darlington Unit 4 in 1995.

Early in 1993 Bruce-A Unit 4 outage, tubes pulledfrom the primary side of Boiler 3 showed no evi-dence of pitting. None-the-less, about 25 cm (10inches) of sludge was measured through the open-ings left by the tube pulls. Due to the timing of thetemporary containment seal development, tubesheet lancing could only be carried out after chemicalcleaning.

Foster-Miller Inc.(FMI) received the contract award todevelop, supply and operate an automated tubesheet water lancing system. The equipment laterpurchased by Bruce-A, is based on FMIsConsolidated Edison Combined Inspection andLancing (CECIL®) technology. The lancing systems'key components are:

1) A six-piece rail on which various spray and robotmodules (described below) travel. The rail isinserted into the NTL just below support plate 1and is held in place by inflatable bladders.

2) A 90° barrel spray module that directs 8 low pres-sure water jets (4 per side) down 90° tube lanesfrom the NTL. By rotating this unit back and forth,loose sludge deposits are flushed toward theannulus and rennoved by the suction/filtration system.

3) A 307150° barrel spray unit that directs water jetsdown 30° and 150° tube lanes from the NTL andflushes away loosely bound shadow zonedeposits left behind after the 90° barrel sprays.This module was developed and used later duringthe 1993 Unit 4 outage.

4) A lance robot module to control lance movementand position.

5) A "straight ahead" lance with 4 flexible pressuretubes wrapped in Kevlar™. This lance is used athigher pressures than either the 90° or 307150°barrel spray unit to cut away hard deposit leftafter the low pressure barrel washes. Afibrescope in the center of the lance providesvisual feedback. Accurate tube sheet assess-ments are possible by continuous visual monitor-ing and computer generated readouts of robotposition, lance angle, depth and height from thetube sheet.

6) A "side-shooting" lance to clean shadow zonesleft behind after the 307150° barrel sprays. The

lance is similar to the straight ahead lance but thewater jets are directed sideways.

Figure 9 depicts several system components as theywould appear within the steam generator.

The lancing strategy for Unit 4 was to remove loosesludge by performing a combination of 90° and307150° barrel sprays, and using the side-shootinglance where required. Hard sludge piles thatremained would then be removed by the straightahead lance.

2.3.2 Tube Sheet Water Lancing Results

Table 4 shows the sludge quantities removed by theUnit 3 and 4 tube sheet cleaning operations. Nominalnozzle operating pressures for the barrel spray andstraight ahead lancing operations were 3,000 and5,000 psig respectively. The side-shooting lance wasoperated at 5,000 psig (nozzle). Sections 2.3.2.1 and2.3.2.2 below describe the results from each outage.

2.3.2.1 Unit 4Boiler 7 was the first Unit 4 steam generator to bewater lanced. Prelancing inspections revealed sludgeheights of about 35.6 and 30.5 cm (14 and 12 inchesrespectively) in the center of the hot and cold legsrespectively (See Figure 10). Repeated passes withthe 90° barrel spray unit cleaned the cold leg andouter hot leg areas down to the tube sheet. Theremaining shadow deposits were effectivelyremoved with the side-shooting lance. (The 307150°barrel spray unit was developed later for the westbank tube sheet lancing operations).

Hard, tenacious tube scale prevented the straightahead lance from entering the hot leg central areas;access was limited to about 7 inches above the tubesheet and tube sheet condition assessments couldnot be carried out in this region. This finding was con-sistent for all Unit 4 boilers. Despite repeatedattempts to remove the hard tube scale with eitherthe straight ahead lance or lances fitted with severaloffset nozzles, the hard deposits remained intact.However, hard sludge piles were not seen in any ofthe restricted hot leg areas. 5

On average, the automated system dislodged about275 kg of wet sludge per boiler. The percentage ofchemical cleaning insoluble residues in the removedsludge is not known since the lancing operationswere carried out only after chemical cleaning.

2.3.2.2 Unit 3

Based on the 1993 Unit 4 results, tube sheet lancingoperations for Unit 3 were carried out before andafter chemical cleaning. The prechemical cleaningoperations were performed to remove loose tube

196


sheet sludge and expose the hard tube deposits forreaction with the chemical cleaning solvents.Chemical cleaning insoluble residues were removedby the postchemical clean barrel washes.

Before chemical cleaning, prelancing inspections ofBoiler 5 showed maximum sludge heights of rough-ly 23-25 cm (9-10 inches) in the hot and cold legsides. The combination of 90° and 307150° barrelsprays cleaned the cold leg and outer hot leg areasdown to the tube sheet. Thin deposits remained inthe original location of the pile with no shadow zonesleft behind. Hard tube deposits similar to those left inUnit 4, were found in the hot leg central area; thislimited lance insertion to no more than 7.6-15.2 cm(3-6 inches) above the tube sheet and preventedtube sheet inspections in this area. As in Unit 4 theprevious year, hard sludge piles were not seen in therestricted hot leg areas.

The postlancing condition of the remaining boilersclosely resembled that of Boiler 5. Although hardtube scale was also found about 1-2 inches abovethe tube sheet in some cold leg areas inspected afterwater lancing, the tube sheet was visible in theseregions. Prechemical clean water lancing operationsremoved about 222 kg of sludge per boiler (See Table4). 2,6

The first boiler lanced after chemical cleaning wasBoiler 3. To estimate the depth of chemical cleaninginsoluble residues, a central hot leg and cold leg lanewas inspected before water lancing. Maximumsludge heights of 20.3 cm (8 inches) and 12.7 cm (5inches) were found in the center of the hot and coldleg sides respectively. Similar sludge heights werelater measured during more rigorous postchemicalclean and prelancing inspections in Boiler 5.

Postchemical clean lancing operations dislodgedabout 109 kg of residue per boiler. The post lancingcondition of Boiler 3 and the other Unit 3 boilers afterchemical cleaning, closely resembled their postlanc-ing appearance before chemical cleaning; althoughthe cold leg and peripheral hot leg areas had beencleaned down to the tube sheet, hard tube depositsabout 7.6-15.2 cm (3-6 inches) above the tube sheetremained in the central hot leg areas. Nearly all hardtube collars found near the tube sheet before chem-ical cleaning were unaffected by the chemical clean-ing process.

The persistence of hard tube collars probably result-ed from the rapid buildup of insoluble residuesaround the tubes and on top of the tube sheets dur-ing chemical cleaning. A likely scenario is that oncethe insolubles settled onto the tube sheet, they

became an effective barrier between the chemicalcleaning solvents and the hard deposits.

3 .0 CONCLUSIONS AND FUTURE BNGS-ABOILER CLEANING OPERATIONSBased on the Unit 3 and 4 water lancing data, theconclusions of this paper are:

1) The combination of water lancing and chemicalcleaning effectively removed broach holedeposits in Units 3 and 4. As a result, both unitswill run for some time to come without concernsabout boiler water level oscillations.

2) The water lancing and chemical cleaning opera-tions left the boiler HLUBS in Unit 3 cleaner thanthose in Unit 4. This was mainly due to the longeriron step carried out during the Unit 3 chemicalclean and improvements in the lancing technolo-gy. Much of the scallop bar surface deposit left onthe Unit 4 HLUBS in 1993 was removed duringthe 1995 lancing operations. However, the lanc-ing operations did not succeed in dislodgingdeposits from most hour glass areas in Units 3and 4. Modified chemical cleaning and/or waterlancing methods are required to remove thedeposits left behind on the Unit 3 and 4 boilerHLUBS. Currently, the addition of a crevice clean-ing step to the boiler chemical cleaning sequenceis considered the best alternative.

3) The tube sheet lancing operations efficientlyremoved soft sludge and cleaned the cold leg andouter hot leg areas down to the tube sheet.However, water lancing had little effect on thehard tube collars in the central hot leg areas.These deposits were unaffected by the chemicalcleans carried out on either unit. Additionalinspections in the area of the hard collars arerequired to determine the tube sheet condition.Further cleaning operations may be warrantedbased on the inspection results.

Late in 1994, water level oscillations in several Unit 1boilers indicated broach hole blockage. The upperboiler support plates in this unit were water lanced in1990 to restore steam and water flow to allow fullpower operation. Support plate, HLUBS and tubesheet water lancing operations are planned for theUnit 1 outage in September 1995. However, a smallscale lancing campaign was required in December1994 to clean the upper support plates in all eightUnit 1 boilers. This has provided short-term relief forthe oscillation problems.

The 1995 Bruce-A Unit 1 chemical clean will includea crevice cleaning step that may last up to 100 hours

197


at 121°C, compared with 93°C for the iron removalstep. The crevice clean will involve periodic vents toinduce solvent boiling and cleaning of tube land areasin the U-bend supports and broach plates. As aresult, it is expected that Unit 1 boiler tube supportswill be left in a much cleaner state than those ineither Units 3 or 4 after water lancing and chemicalcleaning. The outcome of the chemical cleaning andwater lancing operations in Unit 1 will help definefuture boiler cleaning programs for Bruce-A Units 3and 4.

4.0 ACKNOWLEDGEMENTSThe authors would like to thank the following OntarioHydro NTS staff for reviewing this paper and provid-ing many helpful comments: D. McCabe (SpecializedInspection and Maintenance), T. Dereski (Chemistryand Metallurgy Dept. - Cleaning Services Section), P.Spekkens (Manager, Chemistry and MetallurgyDept.) and J. Malaugh (Chemistry and MetallurgyDept. - Center for Heat Exchanger EngineeringSciences and Technology).

5.0 REFERENCES1) "Bruce-A Unit 4 Boiler Water Lancing Operations.

February-October 1993, Summary of Support

Plate, U-bend and Tube Sheet Water Lancing," byF. V. Puzzuoli, Ontario Hydro Report No: NK21-33110-940004, January 1994.

2) "Bruce-A Unit 3 Boiler Water Lancing Operations,May-August 1994, Summary of Support Plate, U-bend and Tube Sheet Water Lancing," by F.V.Puzzuoli, Ontario Hydro Report No: NK21-REP-33110-0004 REV.O, November 26, 1994.

3) "BNGS-A Unit 1 Short-Term Cleaning Program,"by D. Andrew and S. Chan, Ontario Hydro ReportNo: CPS-N-33110-0002, April 4, 1991.

4) "Bruce-A U4 33110 In-service Inspection ofBoiler Secondary Side Components," by D.McCabe, Ontario Hydro Report No: NK21-33110-955113 (Report in preparation).

5) "Ontario Hydro Bruce Nuclear Generating Station"A" Unit 4 - CECIL® System Tube Sheet WaterLancing Field Operation, August-October 1993,Foster-Miller Inc. Report issued November 5,1993.

6) "Ontario Hydro Bruce Nuclear Generating Station"A", Unit 3 - CECIL® System Boiler Tube SheetLancing Field Operations, April to August 1994,"Foster-Miller Inc. Report issued October 1994.

198

Table 1

HOT LEG

Percent Broach Hole Blockages in Unit 4 Boilers

SupportPlate

11

12

3

4

5

6

7

Boiler 1

PreLance

30-40

0-10

Nl

Nl

Nl

30-50

30-50

PostLance

10-20

0-10

NL

0-10

0-10

0-10

0-10

PostBOCC

0-10

0-5

0-5

0-5

0-5

Boiler 2

PreLance

100

10-40

NP

40-50

40-50

Nl

Nl

PostLance

0-10

0-10

-

0-10

10-20

0-10

0-10

PostBOCC

-

0-10

0-10

0-5

0-10

Boiler 3

PreLance

50-100

0-10

30-40

30-50

40-50

40-60

40-60

PostLance

0-5

0-5

NL

0-10

0-10

0-10

0-10

PostBOCC

0-10

0-5

0-5

0-10

0-5

Boiler 4

PreLance

0-10

0-10

NP

30-50

40-50

40-60

40-60

PostLance

NL

NL

NL

0-10

0-10

0-10

0-10

PostBOCC

-

0-5

0-10

0-5

0-5

COLD LEG

SupportPlate

11

'2

3

4

5

6

7

Boiler 1

PreLance

10-20

10-20

Nl

Nl

Nl

40-60

40-60

PostLance

NL

NL

NL

0-10

0-10

0-10

0-10

PostBOCC

0-10

0-5

0-5

0-5

0-5

Boiler 2

PreLance

10-20

0-10

NP

40-50

40-50

60-70

60-70

PostLance

NL

NL

. -

0-10

0-10

0-10

0-10

PostBOCC

-

0-5

0-5

0-5

0-5

Boiler 3

PreLance

10-20

0-20

30-40

30-50

40-50

40-60

40-60

PostLance

NL

NL

NL

0-10

0-10

0-10

0-10

PostBOCC

-

-

0-10

0-5

0-5

0-5

0-5

Boiler 4

PreLance

0-10

0-10

NP

40-60

40-50

50-60

50-50

PostLance

NL

NL

NL

0-10

0-10

0-10

0-10

PostBOCC

-

0-5

0-5

0-5

0-5

'For support plates 1&2, % Prelance blockage •after chemical cleaning.

% Postchemical clean blockage since these support plates were inspected and/or water lanced

NL = Not lanced Nl = Not inspected NP = No port installed.

Table 1 (Continued)

HOT LEG

SupportPlate

'1

12

3

4

5

6

7

Boiler 5

PreLance

NL

NL

40-60

50-70

40-60

50-60

60-80

PostLance

-

-

0-10

0-10

0-10

0-10

0-10

PostBOCC

0-5

0-5

0-5

0-5

0-5

0-5

0-5

Boiler 6

PreLance

NL

NL

50-60

40-50

50-70

50-70

70-100

PostLance

-

-

0-10

0-10

0-10

0-10

0-10

PostBOCC

0-5

0-5

0-5

0-5

0-5

0-5

0-5

Boiler 7

PreLance

NL

NL

Nl

Nl

Nl

50-70

50-70

PostLance

-

-

0-10

0-10

0-10

10-20

10-20

PostBOCC

0-5

0-5

Nl

0-5

0-5

0-5

0-10

Boiler 8

PreLance

NL

NL

40-50

60-70

50-60

50-60

60-80

PostLance

-

-

0-10

0-10

0-10

0-10

0-10

PostBOCC

0-5

0-5

0-5

0-5

0-5

0-5

0-5

COLD LEG

SupportPlate

M12

3

4

5

6

7

Boiler 5

PreLance

NL

NL

40-80

50-60

50-60

50-70

60-70

PostLance

-

-

0-10

0-10

0-10

0-10

0-10

PostBOCC

0-5

0-5

0-5

0-5

0-5

0-5

0-5

Boiler 6

PreLance

NL

NL

70-90

50-80

50-70

60-80

70-80

PostLance

-

-

0-10

0-10

0-10

0-10

0-10

PostBOCC

0-5

0-5

0-5

0-5

0-5

0-5

0-5

Boiler 7

PreLance

NL

NL

Nl

Nl

Nl

50-70

70-80

PostLance

-

-

-

0-10

0-10

10-20

10-20

PostBOCC

0-5

0-5

0-5

0-5

0-5

0-5

0-5

Boiler 8

PreLance

NL

NL

80-100

50-60

60-70

50-60

60-80

PostLance

-

-

0-10

0-10

0-10

0-10

0-10

PostBOCC

0-5

0-5

0-5

0-5

0-5

0-5

0-5

1For support plates 1&2,after chemical cleaning.

% Prelance blockage - % Postchemical clean blockage since these support plates were inspected and/or water lanced

NL = Not lanced Nl = Not inspected

Table 2

HOT LEG

Percent Broach Hole Blockages in Unit 3 Boilers

SupportPlate

1

2

3

4

5

6

7

Boiler 1

PreLance

20-30

40-60

NP

20-40

30-40

10-20

30-40

PostLance

NL

NL

-

NL

NL

NL

NL

PostBOCC

Nl

Nl

-

0-10

0-10

0-10

0-10

Boiler 2

PreLance

MO-60

30-50

NP

30-40

40-50

0-10

30-50

PostLance

0-10

Nl

-

NL

NL

NL

NL

PostBOCC

Nl

Nl

-

0-10

0-10

0-10

0-10

Boiler 3

PreLance

20-40

20-30

NP

20-30

40-50

10-20

20-40

PostLance

NL

NL

-

NL

NL

NL

NL

PostBOCC

20-520-5

-

0-5

0-5

0-5

0-5

Boiler 4

PreLance

30-50

30-40

Nl

20-40

30-40

10-20

40-80

PostLance

NL

NL

NL

NL

NL

Nl

10-20

PostBOCC

Nl

Nl

0-5

0-5

0-5

0-5

0-5

COLD LEG

SupportPlate

1

2

3

4

5

6

7

Boiler 1

PreLance

50-70

20-30

NP

20-30

30-40

20-30

20-40

PostLance

0-10

Nl

-

NL

NL

NL

NL

PostBOCC

Nl

Nl

-

0-5

0-5

0-10

0-10

Boiler 2

PreLance

30-50

10-2'.;

NP

20-30

20-40

10-30

50-70

PostLance

NL

NL

• -

NL

NL

Nl

0-10

PostBOCC

Nl

Nl

-

0-10

0-10

0-10

0-10

Boiler 3

PreLance

30-40

20-40

NP

20-40

30-40

10-30

30-40

PostLance

NL

NL

-

NL

NL

NL

NL

PostBOCC

20-5

20-5

-

0-5

0-5

0-5

0-5

Boiler 4

PreLance

30-50

20-30

Nl

20-30

20-40

20-30

50-70

PostLance

NL

NL

NL

NL

NL

Nl

0-10

PostBOCC

Nl

Nl

0-5

0-5

0-5

0-5

0-5

'The decision to lance was based on observations of heavy tube deposits near support plate 1.2 Postchemical clean inspections were possible only for Boilers 3 & 6 where temporary flanged nozzles were installed between support plates 1 &2.

NL = Not lanced Nl = Not inspected NP => No port installed.

Table 2 (Continued)

HOT LEG

s

SupportPlate

1

2

3

4

5

6

7

Boiler 5

PreLance

40-70

50-80

NP

20-40

30-40

0-10

60-80

PostLance

0-10

0-10

-

NL

NL

Nl

0-10

PostBOCC

Nl

Nl

-

0-5

0-10

0-5

0-5

Boiler 6

PreLance

50-70

20-40

NP

10-20

20-40

0-10

60-80

PostLance

0-10

Nl

-

NL

NL

Nl

0-10

PostBOCC

'0-5

'0-5

-

0-5

10-20

0-5

0-5

Boiler 7

PreLance

'40-60

30-50

NP

20-30

30-50

0-10

40-50

PostLance

10-20

10-20

-

NL

NL

NL

NL

PostBOCC

Nl

Nl

-

0-5

0-10

0-5

0-5

Boile • 8

PreLance

30-40

40-50

NP

30-50

40-60

10-20

50-70

PostLance

NL

NL

-

NL

NL

Nl

10-20

PostBOCC

Nl

Nl

-

0-5

0-5

0-5

0-5

COLD LEG

SupportPlate

1

2

3

4

5

6

7

Boiler 5

PreLance

20-40

20-30

NP

20-40

20-40

10-30

40-50

PostLance

NL

NL

-

NL

NL

NL

NL

PostBOCC

Nl

Nl

-

0-5

0-5

0-5

0-5

Boiler 6

PreLance

60-80

40-50

NP

20-30

20-40

10-30

30-50

PostLance

0-10

Nl

-

NL

NL

NL

NL

PostBOCC

'0-5

'0-5

-

0-5

0-5

0-5

0-5

Boiler 7

PreLance

'40-50

20-30

NP

20-30

30-40

0-10

20-30

PostLance

Nl

Nl

-

NL

NL

NL

NL

PostBOCC

Nl

Nl

-

0-5

0-5

0-5

0-5

Boiler 8

PreLance

20-30

30-40

NP

10-30

30-40

20-30

50-70

PostLance

NL

NL

-

NL

NL

Nl

0-10

PostBOCC

Nl

Nl

-

0-5

0-5

0-5

0-5

'The decision to lance was based on observations of heavy tube deposits near support plate 1.2Postchemical clean inspections were possible only for Boilers 3 & 6 where temporary flanged nozzles were installed between support plates 1&2.

NL = Not lanced Nl = Not inspected NP = No port installed

Table 3 Scallop Bar Surface Cleanliness Estimates for Bruce-A Unit 3 and 4 Boiler HLUBS

toow

Boiler

1

2

3

4

5

6

7

8

'Unit 4(1993)

TopSide

Range

10-50%

0-10

0-10

80-90

30-60

30-60

30-60

30-60

Average

19%

2

8

85

50

50

50

50

BottomSide

Range

0-90%

0-50

0-50

60-80

60-80

60-80

60-80

60-80

Average

44%

24

21

70

70

70

70

70

Unit 4(1995)

TopSide

Range

60-90%

0-5%

50-100

70-90

70-80

50-70

50-80

70-90

Average

75%

3

75

80

77

67

65

80

BottomSide

Range

75-85%

NA

60-100

75-90

250-90

260-90

250-80

280-90

Average

85%

-

85

87

83

78

75

87

Unit 3(1994)

TopSide

Range

50-70%

40-70

50-70

40-70

40-80

30-40

20-40

10-60

Average

60%

53

60

58

60

32

27

30

BottomSide

Range

70-80%

70-90

80-90

80-90

70-90

60-80

30-70

80-90

Average

75%

78

88

88

85

71

55

83

NA = Not accessible

'All reported data are based on "by eye" estimates of scallop bar surface cleanliness from visual inspections. The ranges reported represent theminimum and maximum surface exposures observed. For example.a range of 40-80% means that at least one lane had a surface exposure of 40%and at least another showed 80% surface cleanliness; surface exposures for the remaining lanes fell between the two values.

2Not water lanced.

3West bank boilers were not water lanced before chemical cleaning. The iron step during the west bank clean was stopped after 8.5 hours. Incomparison, the east bank clean involved a 40-hour iron step.

Table 4 Wet Tube Sheet Sludge Removed from Unit 3 and 4 Boilers1

(O

BANK

West

East

BOILER

1

2

3

4

Average

5

6

7

8

Average

Totals

SLUDGE REMOVEDPRECHEMICAL

CLEANING(Unit 3 1994)

219.0 kg

195.0

177.7

194.1

196.5 kg

229.3 kg

235.4

247.6

273.8

246.5 kg

1,771.9 kg

SLUDGE REMOVEDPOSTCHEMICAL

CLEANING(Unit 31994)

96.5 kg

234.5

147.0

124.5

150.6 kg

57.4 kg

73.6

86.0

55.2

68.1kg

874.7 kg

TOTAL SLUDGEREMOVED

(Unit 3 1994)

315.5 kg

429.5

324.7

318.6

347.1 kg

286.7 kg

309.0

333.6

329.0

314.6 kg

2,646.6 kg

TOTAL SLUDGEREMOVED FROMUNIT 4 BOILERS

(1993)2

295.6 kg

390.4

424.0

385.4

373.9 kg

189.7 kg

213.1

151.4

151.5

174.6 kg

2,201.1kg

1AII sludge weights were calculated by subtracting wet filter weights from the gross weight. The weights reported for Unit 4 in Reference 1 werecalculated using dry filter weights. The corrected Unit 4 weights are listed above.

2The 1993 Unit 4 tube sheet lancing operations were performed after boiler chemical cleaning.


FIGURE 1 Bruce-A Boiler Cutaway View

U-Bend Area

No-Tube-Lane

ContainmentBellows

Tube Sheett

SupportPlates

Blowdown RingHeader

FIGURE 2 Broach Hole Design

Broach HoleOpening ».-

Broach Plate

Tubes

205


O

03

to

JOOL

t:oQ.Q.3(0

i(0

a.o

ill

3—ol

8 8 s s E a :

o

2 0 6


FIGURE 4 Scallop Bar GeometrySCALLOP DIVISION

SCALLOP BAR

TUBE

TOP VIEW SIDE VIEW

FIGURE 5 Boiler U-bend Supports

o

Extent of 40° Supportsfl lii* lifi(Tube r o w s 4 2 t o 9 5 )mmmmmmm

80

20

too

TUBE COLUMNS 2 0 7

FIGURE 6 30° Lance Design Features

Connection for HighPressure Hose

8

Lance Body With 8SS Tubes Encased inRigid Plastic

Rear Lance Manifold Offsetting Water Jets(Parallel to BoilerTubes)

TYPICAL LANCE DIMENSIONS: 9 ft, 6 In long.0.115 in thick1.5 in wide

LanceNozzle(0.040"drilledhole)

Front ^Manifold rt

n

I8001


FIGURE 7 HLUBS Manual Lancing Equipment

Assembly Diagram

Lance Guide Head

Mounting Flange

. — Extension SleeveRetainer

Extension Sleeve

Rotary Collar

Lance Guide Bushing — '

Lance Guide •

As Setup at Boiler HLUBS Access PortLance

209


FIGURE 8 HLUBS Automated Lancing EquipmentAssembly Diagram

- Guide Head

- Lane* Guide

Mounting Rang*Assembly

Rotational OrtveAnambty

Guide DriveAssembly

Lance Ortve

As Setup at Boiler HLXJBS Access Port

Guide DriveAssembly

Lance DriveAssembly

\n2 1 0


FIGURE 9 CECIL® Components Within the Steam Generator

Till Module

Lance Barrel

Rail

Flexible Lance(Fitted withFibrescope)

From Reference 5

FIGURE 10 As Found Condition of Boiler 7 in Unit 4

Plan View

From Reference 5

211NEXT PAQE(S)

left BLANK

Documents

WATER LANCING OF BRUCE-A UNIT 3 AND 4 STEAM GENERATORS