ML11363A076

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Evaluation of Leakage and Deposit Formation in Painted Full-Scale Bmi Mockups, Final Report, Revision 2, Swri Project No. 18.16196, Ceng Purchase Order No. 6610691
ML11363A076
Person / Time
Site: Ginna Constellation icon.png
Issue date: 08/31/2011
From: Page R
Southwest Research Institute
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Office of Nuclear Reactor Regulation, Constellation Energy Group
References
18.16196, 6610691
Download: ML11363A076 (94)
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ENCLOSURE 3 Evaluation of Leakage and Deposit Formation In Painted Full-Scale BMI Mockups

Evaluation of Leakage and Deposit Formation In Painted Full-Scale BMI Mockups Final Report, Revision 2 SwRI Project No. 18.16196 CENG Purchase Order No. 6610691 By Richard A. Page Southwest Research Institute 6220 Culebra Rd.

San Antonio, TX 78238 Submitted to Ginna Nuclear Power Plant c/o Constellation Energy Group 1503 Lake Road Ontario, NY 14519 August 2011

  • SOUTHWEST RESEARCH INSTITUTE V.

SAN ANTONIO, TEXAS

Table of Contents 1IINTRO DUCTION ................................................................................................................................. 1-1

1.1 BACKGROUND

............................................................................................................................. 1-1 1.2 OBJECTIVE ................................................................................................................................... 1-1 2 EXPERIM ENTAL ................................................................................................................................ 2-1 2.1 TEST MOCKUP DESIGN AND ANALYSIS ....................................................................................... 2-1 2.2 LA S MATERIAL ........................................................................................................................... 2-1 2.3 BAC TESTING FACILITY .............................................................................................................. 2-2 2.3.1 FluidDelivery System .......................................................................................................... 2-2 2.3.2 Mockup andProcessFluidH eating..................................................................................... 2-3 2.3.3 Control andData Acquisition .............................................................................................. 2-3 2.4 PAINT APPLICATION PROCESS ..................................................................................................... 2-3 2.5 BORESCOPE EXAMINATIONS ....................................................................................................... 2-4 3 RESULTS .............................................................................................................................................. 3-1 3.1 TEST 1 .......................................................................................................................................... 3-1 3.2 TEST 2 .......................................................................................................................................... 3-2 3.2.1 10 M il Gap M ockup ............................................................................................................. 3-3 3.2.2 1 Mil Gap Mockup ............................................................................................................... 3-5 3.3 TEST 3 .......................................................................................................................................... 3-7 3.3.1 1 Mil Gap Mockup ............................................................................................................... 3-8 3.3.2 10 Mil Gap Mockup ............................................................................................................. 3-9 4 DISCUSSIO N ........................................................................................................................................ 4-1 4.1 THERMAL CYCLING DAMAGE ..................................................................................................... 4-1 4.2 LEAK TIME AND PRESSURE ......................................................................................................... 4-1 4.3 LEAK PATHS ................................................................................................................................ 4-2 4.4 DEPOSIT FORM ATION .................................................................................................................. 4-2 5 CONCLUSIONS ................................................................................................................................... 5-1 6 REFERENCES ...................................................................................................................................... 6-1 iii

Evaluation of Leakage and Deposit Formation In Painted Full-Scale BMI Mockups Final Report, Revision 2 SwRI Project No. 18.16196 CENG Purchase Order No. 6610691 By Richard A. Page Southwest Research Institute 6220 Culebra Rd.

San Antonio, TX 78238 Submitted to Ginna Nuclear Power Plant c/o Constellation Energy Group 1503 Lake Road Ontario, NY 14519 August 2011 Approval:

Ben H. Thacker, Director Materials Engineering Department

List of Figures Figure 2-1 Cut-away view of the BMI mockup design, from [3] ......................................................... 2-5 Figure 2-2 Cut-away of the fully assembled BMI mockup, from [3], showing the original insulation. All dimensions are listed in inches ................................................................... 2-6 Figure 2-3 Photograph of the fully assembled painted BMI mockup installed in the test cell ............. 2-7 Figure 2-4 Boric acid testing system process diagram ......................................................................... 2-8 Figure 2-5 Photograph of the masking tape applied to the bottom of the mockup ............................... 2-9 Figure 2-6 Photograph of the painted BMI mockup with the masking tape still in place .................... 2-9 Figure 2-7 Photograph of the painted BMI mockup after removal of the masking tape .................... 2-10 Figure 3-1 Photograph of the painted 1 mil gap Test 1 mockup after removal of the masking tape ........ 3-11 Figure 3-2 Photograph of the painted 10 mil gap Test 1 mockup after removal of the masking tap e .................................................................................................................................... 3 -11 Figure 3-3 Borescope image of the bubbled paint around the annulus in the 1 mil gap Test 1 mockup after two thermal cycles to 550'F ........................................................................ 3-12 Figure 3-4 Borescope image of the bubbled paint around the annulus in the 10 mil gap Test 1 mockup after two thermal cycles to 550°F ........................................................................ 3-12 Figure 3-5 Borescope image of cracking and delamination of the paint in the 1 mil gap Test 1 mockup after two thermal cycles to 550'F........................................................................ 3-13 Figure 3-6 Borescope image of cracking and delamination of the paint in the 10 mil gap Test 1 mockup after two thermal cycles to 550°F ........................................................................ 3-13 Figure 3-7 Photograph of the painted 1 mil gap Test 2 mockup after removal of the masking tap e .................................................................................................................................... 3-14 Figure 3-8 Photograph of the painted 10 mil gap Test 2 mockup after removal of the masking tap e .................................................................................................................................... 3-14 Figure 3-9 Plot of the mockup temperature versus time during thermal cycling of the 1 mil gap T est 2 mockup ................................................................................................................... 3-15 Figure 3-10 Plot of the mockup temperature versus time during thermal cycling of the 10 mil gap T est 2 mockup ................................................................................................................... 3-15 Figure 3-11 Borescope image of the paint condition in the 1 mil gap Test 2 mockup after thermal cycling to 350'F................................................................................................................ 3-16 Figure 3-12 Borescope image of the paint condition in the 10 mil gap Test 2 mockup after thermal cy clin g to 350'F ................................................................................................................ 3-16 Figure 3-13 Borescope image of the apparent wet spot present in the 10 mil gap Test 2 mockup after initiation of flow into the annulus but before closure of the bypass valves .............. 3-17 Figure 3-14 Borescope image of three leaks in the 10 mil gap Test 2 mockup that formed after closure of the bypass valves .............................................................................................. 3-17 Figure 3-15 Borescope image of multiple leaks in the 10 mil gap Test 2 mockup that formed after closure of the bypass valves .............................................................................................. 3-18 iv

List of Figures (continued)

Figure 3-16 Borescope image of coolant leaking from around the annulus exit in the 10 mil gap Test 2 mockup during the ambient temperature test ......................................................... 3-18 Figure 3-17 Borescope image of boric acid deposits around the annulus exit in the 10 mil gap Test 2 mockup that formed during heating of the mockup to 350°F by evaporation of the coolant that leaked from the annulus during the ambient temperature test ....................... 3-19 Figure 3-18 Borescope image of steam leaking out of the annulus exit in the 10 mil gap Test 2 mockup during the elevated temperature test .................................................................... 3-19 Figure 3-19 Borescope image of boric acid deposits on the nozzle surface beneath the steam leak in the 10 mil gap Test 2 mockup after 15 minutes of leakage ........................................... 3-20 Figure 3-20 Borescope images of boric acid deposits (a) around the annulus exit and (b) on the nozzle surface beneath the steam leak in the 10 mil gap Test 2 mockup after 75 minutes of leakage ............................................................................................................. 3-21 Figure 3-21 Front view of the bottom of the 10 mil gap Test 2 mockup post test ................................ 3-22 Figure 3-22 Right side view of the bottom of the 10 mil gap Test 2 mockup post test ........................ 3-22 Figure 3-23 Left side view of the bottom of the 10 mil gap Test 2 mockup post test .......................... 3-23 Figure 3-24 Back view of the bottom of the 10 mil gap Test 2 mockup post test ................................ 3-23 Figure 3-25 Stereomicroscope image of deposits present along the primary leak sites along the front of the annulus exit on the 10 mil gap Test 2 mockup ............................................... 3-24 Figure 3-26 Stereomicroscope image of a circumferential crack in the paint adjacent to the deposits present over the primary leak sites along the front of the annulus exit on the 10 mil gap Test 2 mockup ................................................................................................. 3-24 Figure 3-27 Stereomicroscope image of a circumferential crack in the paint along the annulus exit on the left side of the 10 mil gap Test 2 mockup .............................................................. 3-25 Figure 3-28 Stereomicroscope image of circumferential cracks extending beyond the deposits present at a secondary leak site along the back of the annulus exit on the 10 mil gap Test 2 m ockup ................................................................................................................... 3-25 Figure 3-29 Stereomicroscope image of linear cracks present in the paint remote from the annulus on the 10 mil gap Test 2 mockup ...................................................................................... 3-26 Figure 3-30 Stereomicroscope images of two perforations present in the paint beneath the area of heavy deposits at the primary leak site on the 10 mil gap Test 2 mockup after deposit remo v al .............................................................................................................................. 3 -2 7 Figure 3-31 Stereomicroscope image of a circumferential crack present beneath deposits at a secondary leak site along the back side of the annulus on the 10 mil gap Test 2 mockup after deposit removal ........................................................................................... 3-28 Figure 3-32 Stereomicroscope images of the paint penetration into the annulus gap on the 10 mil gap Test 2 mockup. Penetration depths of 3.2 mm and 3.9 mm were measured in (a) and (b), respectively .......................................................................................................... 3-29 Figure 3-33 Borescope image of leakage present in the 1 mil gap Test 2 mockup after initiation of flow into the annulus but before closure of the bypass valves .......................................... 3-30 v

List of Figures (continued)

Figure 3-34 Borescope image of coolant leaking from around the annulus exit in the 1 mil gap Test 2 mockup during the ambient temperature test......................................................... 3-30 Figure 3-35 Borescope images of boric acid deposits around the annulus exit in the 1 mil gap Test 2 mockup that formed during heating of the mockup to 350'F by evaporation of the coolant that leaked from the annulus during the ambient temperature test ................. 3-31 Figure 3-36 Borescope image of steam leaking out of the annulus exit in the 1 mil gap Test 2 mockup during the elevated temperature test .................................................................... 3-32 Figure 3-37 Borescope images of boric acid deposits (a) on the nozzle surface beneath the steam leak and (b) around the annulus exit in the 1 mil gap Test 2 mockup after 15 minutes o f leak age .......................................................................................................................... 3-33 Figure 3-38 Borescope images of boric acid deposits (a) on the nozzle surface beneath the steam leak and (b) around the annulus exit in the 1 mil gap Test 2 mockup after 40 minutes o f leak age .......................................................................................................................... 3-34 Figure 3-39 Front view of the bottom of the 1 mil gap Test 2 mockup post test .................................. 3-35 Figure 3-40 Right side view of the bottom of the 1 mil gap Test 2 mockup post test .......................... 3-35 Figure 3-41 Left side view of the bottom of the 1 mil gap Test 2 mockup post test............................ 3-36 Figure 3-42 Back view of the bottom of the 1 mil gap Test 2 mockup post test .................................. 3-36 Figure 3-43 Stereomicroscope image of deposits present along the front of the annulus exit on the 1 mil gap Test 2 mockup. Note the area of bare metal visible at the base of the nozzle near the center of the im age .............................................................................................. 3-37 Figure 3-44 Stereomicroscope image of deposits and a circumferential crack present along the left side of the annulus exit on the 1 mil gap Test 2 mockup .................................................. 3-37 Figure 3-45 Stereomicroscope image of deposits present along a primary leak site near the back of the annulus exit on the 1 mil gap Test 2 mockup ......................................................... 3-38 Figure 3-46 Higher magnification stereomicroscope image of the center of Figure 3-45 showing an apparent perforation through the paint ......................................................................... 3-38 Figure 3-47 Stereomicroscope image of deposits present at a primary leak site along the back of the annulus exit on the 1 mil gap Test 2 mockup .............................................................. 3-39 Figure 3-48 Higher magnification stereomicroscope image of the center of Figure 3-47 showing two apparent perforations through the paint ..................................................................... 3-39 Figure 3-49 Stereomicroscope image of linear cracks present in the paint remote from the annulus on the 1 mil gap Test 2 mockup ........................................................................................ 3-40 Figure 3-50 Stereomicroscope image of an area of bare metal along the front of annulus on the 1 mil gap Test 2 mockup following deposit removal ........................................................ 3-40 Figure 3-51 Stereomicroscope image of a circumferential crack present along one side of the annulus on the 1 mil gap Test 2 mockup following deposit removal ................................ 3-41 Figure 3-52 Stereomicroscope image of two apparent perforations through the paint at a leak site along the back side of the annulus on the 1 mil gap Test 2 mockup after deposit rem oval .............................................................................................................................. 3-4 1 vi

List of Figures (continued)

Figure 3-53 Stereomicroscope images of the paint penetration into the annulus gap on the 1 mil gap Test 2 mockup. Penetration depths of 2.7 mm and 2.5 mm were measured in (a) and (b), respectively .......................................................................................................... 3-42 Figure 3-54 Stereomicroscope images of pores present in the paint over the (a) I mil and (b) 10 mil annu ls gap ................................................................................................................... 3-43 Figure 3-55 Graph of the mockup temperature versus time during the thermal cycling of the 1 mil gap T est 3 mockup ............................................................................................................ 3-44 Figure 3-56 Graph of the mockup temperature versus time during the thermal cycling of the 10 mil gap Test 3 mockup ...................................................................................................... 3-44 Figure 3-57 Stereomicroscope image of typical circumferential cracking present in the paint over the annulus opening following thermal cycling of the 10 mil gap Test 3 mockup ........... 3-45 Figure 3-58 Borescope image of the leak site in the 1 mil gap Test 3 mockup 12 seconds after it form ed ............................................................................................................................... 3-4 5 Figure 3-59 Borescope image of the leak site in the 1 mil gap Test 3 mockup 1 minute and 11 seconds after it form ed ...................................................................................................... 3-46 Figure 3-60 Borescope image of deposits on the bottom of the LAS ring adjacent to the leak site in the 1 mil gap Test 3 mockup 1 minute and 49 seconds after the leak formed .............. 3-46 Figure 3-61 Borescope image of deposits on the nozzle surface beneath the leak site in the 1 mil gap Test 3 mockup 2 minutes and 58 seconds after the leak formed ................................ 3-47 Figure 3-62 Annulus pressure versus time plots for the 1 mil gap Test 3 experiment ......................... 3-48 Figure 3-63 Borescope images of deposits (a) on the bottom of the LAS ring and (b) on the nozzle surface adjacent to the leak site in the 1 mil gap Test 3 mockup at the completion of the experim ent .............................................................................................................. 3-4 9 Figure 3-64 Front view of the bottom of the 1 mil gap Test 3 mockup post test .................................. 3-50 Figure 3-65 Right side view of the bottom of the 1 mil gap Test 3 mockup post test .......................... 3-50 Figure 3-66 Left side view of the bottom of the 1 mil gap Test 3 mockup post test ............................ 3-51 Figure 3-67 Back view of the bottom of the 1 mil gap Test 3 mockup post test .................................. 3-51 Figure 3-68 View of the leak site on the bottom of the 1 mil gap Test 3 mockup post test ................. 3-52 Figure 3-69 Low magnification stereomicroscope image of deposits at the leak site in the 1 mil gap Test 3 mockup ............................................................................................................ 3-52 Figure 3-70 Higher magnification stereomicroscope images of a single slit in the paint at the leak site in the 1 m il gap Test 3 mockup .................................................................................. 3-53 Figure 3-71 Stereomicroscope images of the leaksite in the 1 mil gap Test 3 mockup. Note the single slit and the appearance of rumpling adjacent to the slit .......................................... 3-54 Figure 3-72 Stereomicroscope image of the paint penetration into the annulus gap on the 1 mil gap Test 3 mockup. A penetration depth of 9 mm was measured in this location ............ 3-55 Figure 3-73 Borescope image of apparent damage to the paint on the nozzle surface, identified by the arrows, following heating to 350°F but prior to the admission of liquid into the annulus of the 10 m il gap Test 3 mockup ......................................................................... 3-55 vii

List of Figures (continued)

Figure 3-74 Borescope image of boric acid deposits present along the front of the nozzle on the 10 mil gap Test 3 mockup after heating to 350°F but prior to the admission of liquid into the annulus following replacement of the orifice ....................................................... 3-56 Figure 3-75 Borescope image of boric acid deposits present along the left side of the nozzle on the 10 mil gap Test 3 mockup after heating to 350°F but prior to the admission of liquid into the annulus following replacement of the orifice ............................................ 3-56 Figure 3-76 Borescope image of boric acid deposits present along the right side of the nozzle on the 10 mil gap Test 3 mockup after heating to 350°F but prior to the admission of liquid into the annulus following replacement of the orifice ............................................ 3-57 Figure 3-77 Front view of the bottom of the 10 mil gap Test 3 mockup post test ................................ 3-57 Figure 3-78 Right side view of the bottom of the 10 mil gap Test 3 mockup post test ........................ 3-58 Figure 3-79 Left side view of the bottom of the 10 mil gap Test 3 mockup post test .......................... 3-58 Figure 3-80 Back view of the bottom of the 10 mil gap Test 3 mockup post test ................................ 3-59 Figure 3-81 Low magnification stereomicroscope image of boric acid deposits present along a region of damaged paint along the front of the nozzle on the 10 mil gap Test 3 m ocku p .............................................................................................................................. 3-59 Figure 3-82 Low magnification stereomicroscope image of boric acid deposits present along a region of damaged paint along the left side of the nozzle on the 10 mil gap Test 3 mocku p .............................................................................................................................. 3 -60 Figure 3-83 Higher magnification stereomicroscope image of boric acid deposits present along a region of damaged paint along the left side of Figure 3-81 .............................................. 3-60 Figure 3-84 Higher magnification stereomicroscope image of boric acid deposits present along a region of damaged paint along the right side of Figure 3-81 ............................................ 3-61 Figure 3-85 Low magnification stereomicroscope image of boric acid deposits present along a region of the annulus where four holes are evident in the paint covering the annulus exit on the 10 m il gap Test 3 m ockup ............................................................................... 3-61 Figure 3-86 Higher magnification stereomicroscope image of the single hole in the paint on the left side of Figure 3-84 ...................................................................................................... 3-62 Figure 3-87 Higher magnification stereomicroscope image of the two holes in the paint in the center of Figure 3-84 ......................................................................................................... 3-62 Figure 3-88 Higher magnification stereomicroscope image of the single hole in the paint on the right side of Figure 3-84 .................................................................................................... 3-63 Figure 3-89 Low magnification stereomicroscope image of the area shown in Figure 3-84 following removal of the boric acid deposits .................................................................... 3-63 Figure 3-90 Low magnification stereomicroscope image of the area shown in Figure 3-80 following partial removal of the boric acid deposits ......................................................... 3-64 Figure 3-91 Low magnification stereomicroscope image of the area shown in Figure 3-81 following partial removal of the boric acid deposits ......................................................... 3-64 Figure 3-92 Stereomicroscope image of the paint penetration into the annulus gap on the 10 mil gap Test 3 mockup. A penetration depth of 8 mm was measured in this location ............ 3-65 viii

List of Figures (continued)

Figure 4-1 Borescope image of deposits present in the annulus exit area during day 2 of MRP-2 8 8 Test 4 ............................................................................................................................ 4-4 Figure 4-2 Borescope image of deposits present in the annulus exit area during day 7 of MRP-2 8 8 Test 4 ............................................................................................................................ 4-4 Figure 4-3 Borescope image of deposits present in the annulus exit area during day 24 of MRP-2 8 8 Test 4 ............................................................................................................................ 4 -5 Figure 4-4 Borescope image of deposits present in the annulus exit area of the 10 mil gap Test 2 mockup after 75 minutes of leakage ................................................................................... 4-5 Figure 4-5 Borescope image of deposits present in the annulus exit area of the 1 mil gap Test 2 m ockup after 40 minutes of leakage ................................................................................... 4-6 Figure 4-6 Borescope image of deposits present in the annulus exit area of the 1 mil gap Test 3 m ockup after 75 m inutes of leakage ................................................................................... 4-6 ix

1 INTRODUCTION 1.1 Background Inspections of penetration nozzles in pressurized water reactor (PWR) vessel closure and bottom heads have shown that these Alloy 600 components may be susceptible to active aging degradation due to primary water stress corrosion cracking (PWSCC). A resulting potential safety concern is boric acid corrosion (BAG) of the low-alloy steel material of the reactor vessel closure and bottom heads from a leaking nozzle penetration. The large wastage cavity observed at the Davis-Besse plant in 2002 resulted from what is believed to be several years of leakage and concentration of the borated reactor coolant [1 ]. In response to these concerns, the U.S.

industry developed a set of periodic visual and surface/volumetric examinations.

In order to confirm the assumptions of the wastage models that form part of the technical basis for these examinations, the Materials Reliability Project (MRP) sponsored an extensive experimental boric acid corrosion program. The MRP program was designed to perform controlled experiments related to each of the three phases of the proposed degradation sequence.

Since the interaction between the different corrosion mechanisms involved was likely to be complex, and to vary significantly over time during the development of a sizeable wastage cavity, the experimental work culminated in full-scale mockup testing of leaking control rod drive mechanism (CRDM) nozzles with a wide range of leak rates and other prototypical conditions (Task 4 of the MRP program [2]). Subsequent to the Task 4 CRDM testing, a series of tests were completed on full-scale mockups of bottom mounted instrument (BMI) nozzles [3].

Although a wide range of prototypical conditions were examined during the CRDM and BMI testing, the effect of paint applied to the low alloy steel (LAS) surface around the annular gap was never examined. Hence, the ability of a paint layer to plug the annulus exit and prevent leakage or obscure deposit formation outside of the annulus and thus impair leak detection during visual inspections was unknown.

The purpose of this report is to describe the test results and conclusions arrived at through completion of a series of tests of painted full-scale BMI mockups designed to determine the ability of a paint layer to plug the annulus exit and prevent leakage or obscure deposit formation outside of the annulus under prototypical BMI nozzle leakage conditions.

1.2 Objective The primary objective of this program was to determine the effect of a paint layer applied to the bottom of the low alloy steel ring and covering the annulus gap on leakage out of the annulus and deposit formation around the leaking annulus. A secondary objective was obtaining information about the effect of the paint layer on pressures within the leaking annulus.

1-1

2 EXPERIMENTAL 2.1 Test Mockup Design and Analysis Two full-scale BMI mockups were used for the painted BMI testing described in this report; one mockup was machined with a 1 mil annulus gap and the other mockup was machined with a 10 mil annulus gap. These two mockups were similar to the mockups that were used throughout the MRP sponsored full-scale BMI mockup testing [3]. An extensive effort went into developing the full-scale BMI mockup to ensure that it simulates the thermal-hydraulic and chemical conditions that are predicted to exist along the effluent leak path for actual BMI penetrations. The BMI mockup provides leak rate control via a simulated crack (orifice) and simulates the thermal-hydraulic conditions predicted for a leaking field nozzle. Details of the BMI mockup and the analysis effort performed in support of its design can be found in the Reactor Vessel Bottom Head Boric Acid Corrosion Testing - Design and Analysis of Full-Scale BMN Mockups Report

[4]. An overall view of the BMI mockup design is provided in Figure 2-1. Two modifications were made to the original mockup design for the tests described in this report. First, two of the thermocouple wells along the front of the mockup, identified as A and B in Figure 2-1, were enlarged and drilled through to the annulus gap. Tubing and valves were connected to each of these ports and a pressure transducer was included in the line from port A. With one or more of the valves open, this modification allowed for full flow through the orifice and into the annulus without producing any significant pressure within the annulus. With both valves closed, exit through anywhere other than the bottom of the annular gap would be blocked. Additionally, the pressure transducer attached to port A would provide for monitoring pressure buildup within the annulus. Second, the insulation package was modified. As shown in Figure 2-2, the original design called for full insulation over all of the mockup, including an adjustable cap on the bottom of the mockup to permit adjustments in the insulation offset. The adjustable cap was not used in these tests to provide better visual access to the bottom of the mockup during the tests.

An assembled modified mockup installed within the test cell is shown in Figure 2-3.

2.2 LAS Material The original RPV heads were fabricated from low alloy steel reactor vessel plate material; either SA 302 Grade B or SA 533 Grade B Class 1. Early in the MRP BAC program a 20,000 lb section of A533 Grade B Class 1 low alloy steel (LAS) from the reactor vessel shell of a canceled plant was procured to serve as a common material for all four tasks of the program. The LAS material exhibited representative material processing and microstructure and a chromium content (0.4 wt%) at the low end of the range typical for PWR vessels [4]. This material, which was used in all of the Task 4 CRDM tests and the BMI tests, was also used for the mockups employed in these painted BMI tests.

2-1

2.3 BAC Testing Facility The test facility capable of delivering prototypical borated water to three independent mockup test cells constructed for the Task 4 testing was used for these painted BMI tests. The facility was designed to deliver borated simulated primary water at temperatures (600 0F) and pressures (1800 to 2500 psig) typical of those found in operating reactor vessels. The flow loops were configured in a once through mode to avoid any carryover fluid contamination. The facility was also designed to operate for extended durations, monitor flow rates in each test cell and operate in a pressure control mode, with an ability to increase pressure to compensate for reduced flow rate caused by partial blockage of the injection orifice.

2.3.1 Fluid Delivery System A process diagram of the test facility's fluid delivery system is provided in Figure 2-4. Makeup water was obtained from a de-ionized (DI) system with a water softener, carbon filter, sediment filter and reverse osmosis filter providing 18 Mo -cm water. Boric acid and lithium hydroxide were added to the DI water in a batch tank. The borated water was then held in two 1500 gallon tanks. Both tanks were continuously sparged with nitrogen gas to reduce oxygen levels in the water to less than 100 ppb.

Borated water from the storage tanks was supplied to the inlet of a high pressure pumping manifold. Three air driven high pressure pumps were employed in the manifold. Each pump could produce an outlet pressure of 3,000 psi @ 100 gpm flow with an air supply of 30 scfm @

100 psi. The three pumps fed a common header, with one pump serving as the primary and the other two serving in a secondary or backup role. All wetted parts in the pumps were compatible with long term usage in ambient temperature borated water.

The common pump manifold provided high pressure borated water to a stainless steel autoclave in each of the test cells in an on-demand basis. The liquid level in each autoclave was maintained with a K-TEK thermal dispersion switch installed in the autoclave head space which energized an electronic solenoid valve on the inlet line to the autoclave. With a drop in the liquid level of more than 1/8 inch within the autoclave, the thermal dispersion switch would open the solenoid valve allowing pressurized water into the autoclave until the level was restored. A hydrogen/nitrogen gas mixture was used to pressurize the head space in the autoclaves with the pressure in the delivery leg downstream of the autoclave set by the head space pressure. The hydrogen also provided additional oxygen reduction of the borated water, reducing oxygen levels to less than 50 ppb.

Preheating of the borated water to 200 to 250'F was also performed in the autoclaves.

The borated water exiting the autoclaves passed through an inline filter, a flow meter and a second inline filter before entering the superheater. Coriolis meters capable of accurate flow measurements well below the 0.001 gpm lower leak rate of these painted BMI tests were used to monitor flow. The superheater, which consisted of a length of stainless steel tubing coiled around a cartridge heater, brought the borated water up to its final delivery temperature before it passed through a third inline filter and then through the orifice into the annulus of the mockup.

The test mockup was situated in a stainless steel box located in front of the fluid delivery system.

The sides and top of the box were removable to facilitate insertion and assembly of the mockup.

Testing of the painted BMI mockups was performed with the front panel of the box removed to facilitate monitoring of the paint condition during the test.

2-2

2.3.2 Mockup and ProcessFluid Heating The finite element analysis (FEA) performed in designing the mockup indicated that eight cartridge heaters located outboard of the nozzle OD combined with a two-zone bottom plate heater were sufficient and flexible enough to provide the heat input necessary to accurately simulate BMI nozzle annulus temperatures for the range of leak rates of interest in this investigation (0.001 to 0.03 gpm). The eight cartridge heaters were spaced equally around the circumference of the LAS ring along with eight thermocouples inserted between the ID of the LAS ring and the centerline of the cartridge heater and 0.75 inch below the top surface of the LAS ring. The FEA analyses assumed symmetric flow into the annulus to define a symmetry plane across the injection point producing four independent thermal zones on each side of the symmetry plane. The cartridge heaters were controlled in pairs across the symmetry plane using one thermocouple as a set point control and the second thermocouple as an over temperature limit. In other words, the heater pairs on either side of the assumed symmetry plane received the same driving current defined by the control thermocouple located on one side of the symmetry plane. Symmetric flow within the annulus would, thus, be expected to produce similar temperature distributions on both sides of the mockup, whereas asymmetric flow would produce side-to-side differences in the mockup.

The FEA results for steady state conditions indicated that the required heat input from individual heaters in the LAS ring would range from 223W to 301W at the highest leak rate. The 1,500W cartridge heaters that were used in each position met these steady state requirements while providing sufficient excess wattage to achieve reasonable heating rates. Heating of the top of the LAS ring was achieved with a custom designed Interference Fit Construction (IFC) heater. To meet the FEA requirements, the IFC heater was designed with two independent zones with the capability to deliver up to the 600W required into each zone. Four thermocouples placed above the heater plate were used for control and monitoring.

Initial heating of the borated water up to 200 to 250°F took place in the autoclaves. Each autoclave was fitted with three 1,000W band heaters and two thermocouples. Superheaters producing up to 10,500W provided final heating of the borated water up to the delivery temperature of 550'F.

2.3.3 Control and Data Acquisition The six thermal zones in the mockup and the two process fluid thermal zones were controlled via independent PID controllers interfaced with an independent PC running Watlow's Watview software. Outputs from the thermocouples, pressure transducers and flow meters were recorded by the PC at regular intervals throughout each test. A UPS provided power backup for the control and data acquisition functions.

2.4 Paint Application Process Plant documentation has identified the paint present on the bottom head of the Ginna reactor as a Koppers bitumastic, hi-zinc content product. Since the original Koppers product was no longer available and Carboline had acquired the majority of the Koppers product line, Ginna personnel worked with a Carboline representative to identify a currently available coating that captured the major characteristics of the original product. Ginna then provided the paint, recommended by Carboline, that was used throughout this study.

2-3

Following assembly of the nozzle in the LAS ring, the outer edge of the bottom surface was masked, as shown in Figure 2-5, to prevent paint from getting into the cartridge heater holes. The paint was applied to an as-machined surface on the first two tests. Subsequent tests used glass bead blasting to prepare the surface prior to painting. The paint was mixed according to the following formula:

  • 300 gm Carboline Bitumastic 300 M Part A;
  • 75 gm Carboline Bitumastic 300 M Part B; and 0 407 gm of Powdered zinc.

With the surface under a heat lamp to produce a surface temperature of approximately 80'F, three to four coats of paint were applied by brush producing a dry film thickness of 15 to 20 mils.

The paint was applied over the bottom face of the LAS ring, over the annulus opening and a short distance up the outer surface of the nozzle. A typical as-painted surface with the masking tape still in place is shown in Figure 2-6. The painted surface following removal of the masking tape is shown in Figure 2-7. Following a period to allow the paint to cure, the painted mockups were installed in the test cells and exposed to a prescribed thermal cycle. A specified cure time and thermal cycle were defined for each test. Although the thermal cycles were employed in order to expose the paint to the same types of thermal degradation that had been experienced by the paint on the bottom reactor head during service, the amount of thermal damage to the bottom reactor head paint would be expected to be significantly greater than that formed by the thermal cycling of the painted mockups due to the longer time at temperature and the higher number of thermal cycles experienced by the bottom reactor head paint. The potentially degrading effects of long term radiation exposure were also not simulated in the mockup paint. The fact that the paint on the bottom reactor head was likely substantially more degraded, due to the combination of more extensive thermal exposure and long term radiation exposure, than the paint present on the mockups tested in this program suggests that the results obtained from the painted mockups should be conservative. In other words, they should over predict the effect of the paint.

The mockups were oriented in an inverted position relative to the reactor bottom head, i.e., the annulus between the nozzle and the LAS ring was open upward during painting. This orientation during painting allowed gravity to assist penetration of the paint into the annulus and likely produced conservative results relative to the actual bottom head, which was likely on its side when painted as it is three stories tall.

2.5 Borescope Examinations A borescope was used to monitor the condition of the paint in the area around the annulus during the tests. The examinations were performed while the tests were in progress, i.e., at temperature and pressure. Access was limited to the front, or injection, side of the annulus exit by the geometric constraints of the test cell. Still photographs were recorded to document the condition of the paint at selected locations and times. Video images were recorded to document the condition of the paint and the location of any effluent exiting the annulus.

2-4

IFc lone 2 f Heater Elemnen~s Hate (Sainless Mel)

`LIAS Wing (A-533, Gnade B. Ckjss1 L Lj Figure 2-1 Cut-away view of the BMI mockup design, from [3].

2-5

7500 AL- ... S.a.ries. Stleel 53?4 Insulation A Qffiet Figure 2-2 Cut-away of the fully assembled BMI mockup, from 131, showing the original insulation. All dimensions are listed in inches.

2-6

Figure 2-3 Photograph of the fully assembled painted BMI mockup installed in the test cell.

2-7

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12105-0DlRE EV Figure 2-4 Boric acid testing system process diagram.

2-8

Figure 2-5 Photograph of the masking tape applied to the bottom of the mockup.

Figure 2-6 Photograph of the painted BMI mockup with the masking tape still in place.

2-9

Figure 2-7 Photograph of the painted BMI mockup after removal of the masking tape.

2-10

3 RESULTS The six painted BMI tests were performed with DI water to which 1,500 ppm boron and 3 ppm lithium were added, which yields a pHT of 6.9. This is the same water chemistry that was used for all of the previous MRP sponsored CRDM and BMI tests. The tests were run as pairs with two mockups, one with a 1 mil annulus gap and one with a 10 mil annulus gap, included in each test. A 28 micron diameter laser drilled orifice, providing a leak rate of 0.001 gpm at operating pressure and temperature, was used in each mockup. Tests 1 and 2 were run on mockups using an o-ring to seal the annulus gap at the top of the mockup. Test 3 was run on mockups that employed a circumferential weld between the nozzle and the LAS ring to seal the top of the annulus. The results obtained in the six painted BMI mockup tests are presented below.

3.1 Test 1 Surface Condition The Bitumastic 300 M paint was applied to an as-machined surface that had been cleaned with acetone and then alcohol. Three coats were applied to each mockup. The three coats produced an average dry film thickness of 18 mils. Photographs of the bottom surface of each mockup after painting are provided in Figures 3-1 and 3-2.

Paint Curing and Thermal Conditioning Following a three day cure at ambient temperature, the painted mockups were installed in the test cells and exposed to thermal conditioning. The thermal conditioning was to include five cycles between ambient and 550'F. Heating from ambient to 550'F, which was accomplished in less than one hour, was followed by an eight hour hold at 550'F and then an overnight air cool back to ambient.

Examination of the paint with a borescope following completion of the second thermal cycle identified significant damage to the paint. While the paint present on the nozzle surfaces appeared to be in good condition, the paint on the LAS ring around the annulus exhibited significant bubbling, as shown in Figures 3-3 and 3-4. The paint on the LAS ring remote from the annulus region, while not bubbled, did exhibit large areas of cracking and delamination, as shown in Figures 3-5 and 3-6. Since neither the bubbling nor the cracking and delamination were representative of the current condition of the paint on the Ginna reactor bottom, the thermal cycling was halted and no further testing was performed on these two mockups.

3-1

3.2 Test 2 Test Methodology As described in Section 2.1, the mockup was modified to allow full flow of the simulated primary water through the orifice and into the annulus without producing any significant pressure within the annulus. This feature was used to ensure that the annulus was filled with primary water prior to the start of each Test 2 experiment. Each of the Test 2 experiments was considered to start when the two bypass valves were closed, which permitted pressure to begin to build within the annulus. The pressure that develops within the annulus is a measure of the paint's ability to seal the annulus, i.e., pressure only builds within the annulus if the paint is acting as a pressure barrier sealing the annulus gap between the nozzle and the LAS ring.

Surface Condition In order to improve paint adhesion, the surface of both LAS rings were first prepared by glass bead blasting and then cleaned with acetone and then alcohol. The bead blasting produced an anchor pattern profile depth of 1S70 using the Keane-Tator Surface Profile Comparator. Three coats of the Bitumastic 300 M paint were then applied by brush with the surface under a heat lamp to produce a surface temperature of approximately 800F. The three coats produced a dry film thickness that ranged from 15 to 20 mils. Photographs of the bottom surface of each mockup after painting are provided in Figures 3-7 and 3-8.

Paint Curing and Thermal Conditioning To eliminate the extensive paint damage that formed during the Test 1 thermal cycles, a longer cure time and a much more moderate thermal cycle were employed. The paint was allowed to cure at room temperature for a full seven days. Following the cure, the painted mockups were installed in the test cells and exposed to thermal cycles with moderate heating and cooling rates and a maximum temperature of 350 0 F. The thermal cycle employed is listed below.

1. Ramp from ambient to 350F at 20F/hr;
2. Hold at 350F for 4 hr;
3. Ramp to IOOF at 40F/hr;
4. Ramp to 350F at 40F/hr;
5. Hold at 350F for 8hr;
6. Ramp to lOOF at 40F/hr;
7. Repeat steps 4, 5 and 6 three or four additional times; and
8. Cool to ambient.

Plots of the mockup temperature versus time during the thermal cycle treatment are provided in Figures 3-9 and 3-10. This more moderate thermal cycle did not produce the bubbling and the cracking and delamination that were observed on the Test 1 mockups after the thermal cycles.

Borescope images illustrating the condition of the paint following the completion of the thermal cycles are provided in Figures 3-11 and 3-12.

3-2

3.2.1 10 Mil Gap Mockup Ambient Temperature Test Assuming that the paint's strength would decrease with increasing temperature, initial testing of the painted annulus was performed without heating of the mockup or the simulated primary coolant in order to operate more conservatively within the paint's maximum strength range.

Under ambient conditions the temperature of the mockup was 62°F and the temperature of the coolant was 63'F. With both bypass valves open, flow was initiated through the orifice and into the annulus by slowly increasing the pressure in the preheat autoclave to 1,500 psi. Prior to reaching 1,500 psi and with both bypass valves still open, what appeared to be a small wet area in the paint along the annulus gap was observed with the borescope, as shown in Figure 3-13.

This area appeared to be the result of a small leak of coolant through the paint.

Once the pressure within the preheat autoclave reached 1,500 psi and a stable flow of 0.001 gpm was achieved, video recording of the annulus exit with the borescope was initiated (Video 3-1 on the appended DVD). The measured pressure within the annulus at this point was 1 psi, and no additional leaks through the paint were evident. Both bypass valves were then closed (10:10:30 AM on Video 3-1) forcing all of the leakage passing through the orifice to either remain in the annulus or exit through the paint. After approximately eight seconds (10:10:38 AM on Video 3-

1) a leak became visible at the initial wet spot along the annulus. Three seconds later (10:10:41 AM on Video 3-1 and Figure 3-14) a second and third location began to leak, and two additional leaks developed five seconds later (10:10:46 AM on Video 3-1 and Figure 3-15). The measured pressure within the annulus had increased to 5 psi at this point. Steady streams of liquid continued to flow out of the annulus through these leak sites. Each of the leaks was located along the annular gap between the nozzle and the LAS ring. The coolant appeared to leak straight through the paint and then along the external surface. There was no visual evidence of coolant penetrating between the paint and the substrate. No damage to the paint was visible in the borescope images.

The pressure within the preheat autoclave was then raised to 2,000 psi. This increase in upstream pressure did not produce any visible change in the leakage out of the annulus. A still image of the leaks is provided in Figure 3-16. The measured pressure within the annulus also remained constant.

Elevated Temperature Test Following the ambient temperature test, both bypass valves were opened while the mockup was heated to 350'F and the coolant was heated to 550 0 F. Once stable temperature and flow conditions were achieved, video recording of the annulus exit with the borescope was initiated (Video 3-2 on the appended DVD). The measured pressure within the annulus at this point was 1 psi. White boric acid deposits had formed where the coolant that leaked during the ambient temperature test had evaporated, as shown in Figure 3-17. However, no visible steam leaks were apparent.

Both bypass valves were then closed forcing all of the leakage passing through the orifice to either remain in the annulus or exit through the paint (11:00:11 AM on Video 3-2). Although no leaks were visible within the field of view, wisps of steam appeared at 11:00:17 AM.

Approximately 17 seconds after the bypass valves were closed, a large steam leak became visible along the front of the annulus (11:00:28 AM on Video 3-2 and Figure 3-18). The measured 3-3

pressure within the annulus had increased to 52 psi when the steam leak formed. The steam exited the annulus at a high velocity creating a flow path down the exterior of the nozzle. White boric acid deposits were visible forming on the nozzle in this flow path in as little as ten seconds after the appearance of the steam leak (11:00:38 AM in Video 3-2). The steam leak was located over the annular gap between the nozzle and the LAS ring. The steam appeared to leak straight through the paint and then along the external surface. There was no visual evidence of any penetration between the paint and the substrate. No damage to the paint was visible in the borescope images.

Leakage under these high temperature conditions was continued for 75 minutes. Still photographs documenting the deposits that formed from the leaks were taken after approximately 15 minutes and 75 minutes of leakage. After 15 minutes, white boric acid deposits were easily visible on the nozzle surface beneath the leak site, as shown in Figure 3-19. After 75 minutes, deposits suggestive of a boric acid glass were present around the annular region at the leak site, as shown in Figure 3-20(a), while the white boric acid deposits that were present further down the nozzle after 15 minutes remained mostly unchanged, as shown in Figure 3-20(b).

Post Test Examinations - 10 mil Gap Following the completion of the leak test, the mockup was removed from the test cell and the insulation, heaters and thermocouples were removed to permit an unobstructed view of the annulus exit region. A combination of white and rust colored deposits were present on the nozzle and LAS ring surfaces at the locations where leakage through the paint occurred, as shown in Figures 3-21 through 3-24. The largest concentration of deposits was associated with the primary leak location along the front of the annulus, as shown in Figure 3-21. Two small areas of deposits, shown in Figure 3-24, suggested that small leaks were also present along the back side of the annulus.

The condition of the paint around the annulus was examined in a stereomicroscope at magnifications up to 40X. Deposits around the primary leak sites along the front of the annulus obscured the underlying paint, as shown in Figure 3-25. Circumferential cracking of the paint along the annulus exit was present adjacent to the deposit covered area, as shown in Figure 3-26.

Similar circumferential cracking of the paint, such as that shown in Figure 3-27, was present in deposit free areas around the annulus exit. Circumferential cracking was also evident extending from both sides of the small area of deposits on the back of the annulus exit, as shown in Figure 3-28. Some cracking was also present in the paint remote from the annulus. These isolated cracks were straight and followed the brush strokes present in the paint, as shown in Figure 3-29.

The deposits around the annulus exit were then removed with water to permit examination of the condition of the paint at the leak sites. Two small, rectangular shaped holes were present in the paint at the primary leak site, as shown in Figure 3-30. The shape of these two holes and the sharp edges that were present indicate that the holes were not holidays but were formed by the steam escaping the annulus. Similar holes were not found at the secondary leak site on the back side of the annulus. Rather, the only damage evident in the paint at the secondary leak site was a circumferential crack, as shown in Figure 3-31.

Following the documentation of the condition of the paint in the stereomicroscope, disassembly of the mockup was completed and the nozzle was removed from within the LAS ring.

Examination of the nozzle surface in a stereomicroscope indicated that the paint had penetrated 3-4

into the annular gap between the nozzle and the LAS ring, as shown in Figure 3-32. The penetration depth ranged from 3.2 to 3.9 mm.

3.2.2 1 MiY Gap Mockup Ambient Temperature Test Using the same assumptions regarding the effect of temperature on the paint's strength that were mentioned for the 10 mil gap test, initial testing of the painted annulus on the 1 mil gap mockup was also performed without heating of the mockup or the simulated primary coolant in order to operate more conservatively within the paint's maximum strength range. The temperature of the mockup was 66°F and the temperature of the coolant was 65°F under the ambient conditions.,

With both bypass valves open, flow was initiated through the orifice and into the annulus by slowly increasing the pressure in the preheat autoclave to 1,500 psi. Prior to reaching 1,500 psi and with both bypass valves still open, a small pool of water was observed beneath the back side of the mockup. Examination of the annulus exit area with the borescope revealed a leak along the back of the annulus, as shown in Figure 3-33. A steady stream of coolant leaking out of the back of the annulus through this leak site formed the liquid pool beneath the mockup. The measured pressure within the annulus at the time of this initial leak with both bypass valves open was 1 psi.

Once the pressure within the preheat autoclave reached 1,500 psi and a stable flow of 0.001 gpm was achieved, video recording of the annulus exit with the borescope was initiated (Video 3-3 on the appended DVD). The measured pressure within the annulus at this point was 1 psi, and no additional leak locations through the paint were evident. Both bypass valves were then closed forcing all of the leakage passing through the orifice to either remain in the annulus or exit through the paint (12:46:20 PM on Video 3-3). Almost immediately multiple drops became visible from the front of the annular gap (12:46:20 PM on Video 3-3 and Figure 3-34). Fluid continued to seep from these leak sites and within 5 seconds (12:46:25 PM on Video 3-3) began to drip from the annular gap. Examination of the visible region of the annular gap identified at least three separate locations at which active leakage was occurring. The measured pressure within the annulus had increased to 19 psi at this point. Steady streams of liquid continued to flow out of the annulus through these leak sites. Each of the leaks was located along the annular gap between the nozzle and the LAS ring. The coolant appeared to leak straight through the paint and then along the external surface. There was no visual evidence of coolant penetrating between the paint and the substrate. Additionally, no damage to the paint was visible in the borescope images.

Elevated Temperature Test Following the ambient temperature test, both bypass valves were opened while the mockup was heated to 350'F and the coolant was heated to 550'F. Once stable temperature and flow conditions were achieved, video recording of the annulus exit with the borescope was initiated (Video 3-4 on the appended DVD). The measured pressure within the annulus at this point was 1 psi. White boric acid deposits had formed where the coolant that leaked during the ambient temperature test had evaporated, as shown in Figure 3-35. However, no visible steam leaks were apparent.

Both bypass valves were then closed forcing all of the leakage passing through the orifice to either remain in the annulus or exit through the paint (1:28:55 PM on Video 3-4). Although no leaks were visible within the field of view, wisps of steam appeared at 1:28:56 PM. These were 3-5

followed almost immediately (eight seconds after the bypass valves were closed) by larger quantities of steam that appeared to come from an area on the back side of the annulus that could not be viewed with the borescope. Approximately 25 seconds after the bypass valves were closed, a steam leak became visible along the left side of the annulus (1:29:20 PM on Video 3-4 and Figure 3-36). The measured pressure within the annulus had increased to 149 psi when the steam leak formed. The steam exited the annulus creating flow paths both down the exterior of the nozzle and along the bottom surface of the LAS ring. White boric acid deposits were visible forming along these flow paths almost immediately after the appearance of the steam leak. The steam leak was located over the annular gap between the nozzle and the LAS ring. The steam appeared to leak straight through the paint and then along the external surfaces. There was no visual evidence of any penetration between the paint and the substrate. Additionally, no damage to the paint was visible in the borescope images.

Leakage under these high temperature conditions was continued for 40 minutes. Still photographs documenting the deposits that formed from the leaks were taken after approximately 15 minutes and 40 minutes of leakage. After 15 minutes, white boric acid deposits were easily visible on the nozzle surface beneath the leak sites and on the LAS surface adjacent to the leak sites, as shown in Figure 3-37. After 40 minutes, the deposits had not changed substantially, as shown in Figure 3-38.

Post Test Examinations Following the completion of the leak test, the mockup was removed from the test cell and the insulation, heaters and thermocouples were removed to permit an unobstructed view of the annulus exit region. A combination of white and rust colored deposits were present on the nozzle and LAS ring surfaces at the locations where leakage through the paint occurred, as shown in Figures 3-39 through 3-42. The largest concentration of deposits was associated with the primary leak location along the right rear of the annulus, as shown in Figures 3-40 and 3-42.

The condition of the paint around the annulus was examined in a stereomicroscope at magnifications up to 40X. Boric acid deposits were present along the front of the annulus, as shown in Figure 3-43. A narrow section of missing paint exposing the bare LAS substrate was also present just beyond the annulus opening. Circumferential cracking of the paint along the annulus exit was present on the left side, as shown in Figure 3-44. Boric acid deposits were present along both sides of the crack. Two areas of somewhat heavier deposits were present along the back side of the annulus. Both white and rust colored deposits were present in these areas, as shown in Figures 3-45 and 3-47. The open cracks that are apparent in the higher magnification images in Figures 3-46 and 3-48 appear to be the primary leak sites. Some cracking was also present in the paint remote from the annulus. These isolated cracks were straight and followed the brush strokes present in the paint, as shown in Figure 3-49. Although similar in nature to the cracking observed on the 10 mil gap Test 2 mockup, the cracking was more extensive on the 1 mil gap mockup.

Removal of the deposits around the annulus exit with water permitted a more thorough examination of the condition of the paint at the leak sites. With the deposits removed, the narrow area of bare metal along the front of the annulus appears to be composed of three overlapping thumbnail shaped sections, as shown in Figure 3-50. Images of the circumferential cracking and two of the open cracks at a primary leak site following deposit removal are provided in Figures 3-51 and 3-52.

3-6

Following the documentation of the condition of the paint in the stereomicroscope, disassembly of the mockup was completed and the nozzle was removed from within the LAS ring.

Examination of the nozzle surface in a stereomicroscope indicated that the paint had penetrated into the annular gap between the nozzle and the LAS ring, as shown in Figure 3-53. The penetration depth ranged from 2.5 to 2.7 mm.

3.3 Test 3 Test Methodology While the annulus was filled with primary water prior to the start of each Test 2 experiment, the Test 3 experiments were started with a dry annulus. The dry annulus starting condition was employed to simulate the condition in which a crack has just penetrated the nozzle wall producing leakage of primary water into an initially dry, paint covered annulus. The elapsed time between the start of the test and the first visible leak, thus, represents the time required to leak sufficient primary coolant into an initially dry annulus to build the annulus pressure to the level that is necessary to produce leakage through the paint and out of the annulus. The plumbing was modified to allow for this change in starting condition. A tee and two additional valves were added between the superheater and the mockup to isolate the mockup while the simulated primary water was brought to the desired temperature and flow rate. Additionally, the bottom port exiting the annulus was capped and the tubing leading from the top port was capped after the pressure transducer. The Test 3 experiments were run by heating the LAS ring to 350°F and then bringing the temperature of the primary water up to 550'F while the mockup was valved off from the primary water, i.e., the annulus was kept dry. The starting point for each experiment was the opening of the orifice valve that allowed 550'F primary water to reach the orifice and begin leaking into the annulus at a rate of 0.001 gpm.

Surface Condition The bottom surface of both of the Test 3 LAS rings were first prepared by glass bead blasting and then cleaned with acetone followed by alcohol. The bead blasting produced a surface condition similar to the 1S 70 condition. Four coats of the Bitumastic 300 M paint were then applied by brush with the surface under a heat lamp to produce a surface temperature of approximately 80'F. The four coats produced a dry film thickness that ranged from 15 to 20 mils.

The Bitumastic 300 M paint was mixed with a larger amount of solvent than had been used for the Test 2 mockups. This reduced the viscosity of the paint resulting in less obvious brush marks and the appearance of more penetration of the paint into the open annulus.

Paint Curing and Thermal Conditioning Following the same curing and thermal conditioning procedures that were used on the Test 2 mockups, the paint was allowed to cure at room temperature for a full seven days. Following the cure, the paint was examined in a stereomicroscope. Small pores, such as those shown in Figure 3-54, were evident in the paint over the annulus gap. These pores did not appear to penetrate through the entire paint layer. Cracking was not observed in any part of the paint. Following the stereomicroscope examination, the painted mockups were installed in the test cells and exposed to thermal cycles with moderate heating and cooling rates and a maximum temperature of 350'F that were identical to those used on the Test 2 mockups. The thermal cycle treatment employed is listed below.

3-7

1. Ramp from ambient to 350F at 20F/hr;
2. Hold at 350F for 4 hr;
3. Ramp to IOOF at 40F/hr;
4. Ramp to 350F at 40F/hr;
5. Hold at 350F for 8hr;
6. Ramp to 10OF at 40F/hr;
7. Repeat steps 4, 5 and 6 three or four additional times; and
8. Cool to ambient.

Plots of the mockup temperature versus time during the thermal cycle treatment are provided in Figures 3-55 and 3-56. Following the thermal cycles, the paint was again examined in a steromicroscope. No evidence of cracking or any other form of thermally induced damage was evident on the 1 mil gap mockup. However, circumferential cracking of the paint covering the annulus gap was present on the 10 mil gap mockup, as shown in Figure 3-57.

3.3.1 1 Mil GapMockup Elevated Temperature Test The video recording of the annulus exit with the borescope is provided in Video 3-5 of the appended DVD. With the mockup heated to 350'F and the primary water heated to 550 0 F, the valve admitting water to the orifice in the mockup was opened (2:41:34 PM on Video 3-5). The first visible leak was detected 19 minutes and 1 second after primary water started to leak into the annulus (3:00:35 PM on Video 3-5). The leak was located on the right, rear side of the mockup. Effluent leaking out of the annulus was visible flowing across the bottom of the LAS ring and down the O.D. of the nozzle. A still photograph of the leak shortly after it was first detected is provided in Figure 3-58. While effluent was visible at this point, only a small amount of boric acid deposit was present. The boric acid deposits present on the bottom surface of the LAS ring increased significantly during the next minute, as shown in Figure 3-59. Boric acid began to deposit on the O.D. surface of the nozzle within the next 30 seconds, as shown in Figure 3-60. The boric acid deposits on the nozzle surface had become quite significant only three minutes after the leak developed, as seen in Figure 3-61.

The annulus pressure increased to 23 psi during the first 40 seconds. The annulus pressure then exhibited a few oscillations before steadily increasing to 85 psi, as shown in Figure 3-62. The leak that developed at 3:00:35 occurred at or very near the peak annulus pressure of 85 psi. The annulus pressure dropped rapidly after the leak formed tailing off into the low 20 psi range within one hour of the leak formation. The test was terminated 75 minutes after the initial leak formed. No additional leaks formed during this 75 minute period. The boric acid deposits present at the conclusion of the test are shown in Figure 3-63.

Post Test Examinations Following the completion of the leak test, the mockup was removed from the test cell and the insulation, heaters and thermocouples were removed to permit an unobstructed view of the annulus exit region. White deposits were present on the nozzle and LAS ring surfaces only at the single location where leakage through the paint occurred, as shown in Figures 3-64 through 3-67.

3-8

The deposits were located along the path that the leaking effluent took across the LAS ring and down the O.D. nozzle surface, as shown in Figure 3-68.

The condition of the paint around the annulus was examined in a stereomicroscope at magnifications up to 40X. A low magnification stereomicroscope image of the leak site is provided in Figure 3-69. A single slit oriented in the axial direction was present in the paint on the nozzle surface just above the annulus gap at the leak site, as shown in the higher magnification images provided in Figures 3-70 and 3-71. This slit, which was approximately 2.4 mm long and 0.4 mm wide, was clearly the exit site for the escaping effluent. The paint on either side of the slit appeared to be lifted from the nozzle forming channels leading to the slit. What appeared to be bare metal was visible beneath the slit, as seen in Figure 3-70. These features suggest that the primary water from the annulus worked its way underneath the paint on the nozzle surface as it tried to exit the annulus. The pressure that built within the delaminated channel ultimately ruptured the paint thereby completing the leak path out of the annulus. The delaminated channel and slit that were present on the nozzle surface were the only damage observed in the paint at the leak site. Additionally, no damage of any type was observed in the paint at any other location around the annulus. The fine circumferential cracking of the paint around the annulus that served as the leak sites in both of the Test 2 mockups was not present in this mockup.

Following the documentation of the condition of the paint in the stereomicroscope, disassembly of the mockup was completed and the nozzle was removed from within the LAS ring.

Examination of the nozzle surface in a stereomicroscope indicated that the paint had penetrated into the annular gap between the nozzle and the LAS ring, as shown in Figure 3-72. The penetration depth ranged from 8 to 9 mm.

3.3.2 10 Mil Gap Mockup Elevated Temperature Test With the valve supplying simulated primary water to the orifice in the mockup closed, the mockup was heated to 350'F and the coolant was heated to 550'F. Borescope examination of the paint around the annulus exit prior to opening the valve to the orifice revealed the presence of damage to the paint on the nozzle surface slightly below the annulus, as shown in Figure 3-73.

This damage, which formed an apparent gap in the paint layer around the circumference of the nozzle, was clearly not present when the mockup was re-installed in the test cell following the thermal cycling. This damage appears to have formed during heating of the mockup to 350'F.

With the mockup heated to 350'F and the primary water heated to 550'F, video recording of the annulus exit with the borescope was initiated and the valve admitting water to the orifice in the mockup was then opened (11:50:08 AM on Video 3-6). The video recording of the annulus exit with the borescope is provided in Video 3-6 of the appended DVD. Recording of the annulus exit continued for 13 minutes and 19 seconds. During this time no evidence of any leakage out of the annulus was detected and the pressure reading in the annulus did not increase from its initial reading of 1 psi. At a leak rate of 0.001 gpm, the annulus volume of the 10 mil gap mockup should have been filled in one or two minutes. Since no leakage or pressure change was evident after 13 minutes, it appeared as though the orifice had plugged. Hence, the valve to the orifice was closed and the test was terminated. Readings from the Coriolis meter indicated that flow had 3-9

decreased to zero early in the test. Removal of the orifice after the mockup had cooled confirmed that it was totally plugged by boric acid crystals which had deposited in and around the orifice.

After installing a new orifice, the mockup was once again heated to 350'F and the primary water heated to 550'F, with the orifice valve still in the closed position. Once the temperatures had stabilized, the annulus exit was examined with the borescope prior to opening the orifice valve.

Extensive boric acid deposits, which were not present when the first test attempt was terminated due to the plugged orifice, were evident around the annulus exit. Borescope images of these deposits are provided in Figures 3-74 through 3-76. Due to the presence of these boric acid deposits, the test was not resumed and the mockup was cooled without ever re-opening the orifice valve. The boric acid deposits clearly formed when borated water leaked out of the annulus and then evaporated. This water must have passed through the orifice into the annulus after the orifice valve was opened at the start of the first test attempt and before the orifice plugged. The leakage and vaporization that formed the deposits most likely occurred during heating of the sealed annulus at the start of the second test attempt. No measurable pressure rise within the annulus was observed during this second heating of the mockup.

Post Test Examinations Following the completion of the test, the mockup was removed from the test cell and the insulation, heaters and thermocouples were removed to permit an unobstructed view of the annulus exit region. White boric acid deposits covered most of the circumference of the nozzle surface just above the annulus exit, as shown in Figures 3-77 through 3-80. Deposits were also located along what appeared to be the path that the leaking effluent took down the O.D. nozzle surface, as shown in Figure 3-79.

The condition of the paint around the annulus was examined in a stereomicroscope at magnifications up to 40X. The boric acid deposits on the nozzle surface were associated with areas of obvious damage to the paint. As shown in Figures 3-80 and 3-81, an irregular pattern of circumferential cracking and delamination was present in the paint on the nozzle surface above the annulus exit. This damage was located between 1 and 2 mm above the annulus exit and appeared to correspond with the location of the paint damage, shown in Figure 3-73, that was seen following heating of the mockup to 350'F prior to the initial pressurization of the annulus.

Sections of the nozzle surface appeared to be visible within these regions, as shown in Figures 3-82 and 3-83. One small section of the annulus exit, shown in Figure 3-84, had boric acid deposits located along the gap between the nozzle and the LAS ring. Narrow circumferential cracking and four holes that appeared to penetrate through the paint into the annulus were present within this section, as shown in Figures 3-85 through 3-87. Removal of the boric acid deposits with water provided a clearer view of the holes and circumferential cracking, as shown in Figure 3-88. The damage present in the paint on the nozzle surface was also more visible once some of the deposits had been removed, as shown in Figures 3-89 and 3-90.

Following the documentation of the condition of the paint in the stereomicroscope, disassembly of the mockup was completed and the nozzle was removed from within the LAS ring.

Examination of the nozzle surface in a stereomicroscope indicated that the paint had penetrated into the annular gap between the nozzle and the LAS ring, as shown in Figure 3-91. The penetration depth ranged from 8 to 10 mm.

3-10

Figure 3-1 Photograph of the painted I mil gap Test 1 mockup after removal of the masking tape.

Figure 3-2 Photograph of the painted 10 mil gap Test 1 mockup after removal of the masking tape.

3-11

Figure 3-3 Borescope image of the bubbled paint around the annulus in the 1 mil gap Test 1 mockup after two thermal cycles to 550'F.

Figure 3-4 Borescope image of the bubbled paint around the annulus in the 10 mil gap Test 1 mockup after two thermal cycles to 550'F.

3-12

Figure 3-5 Borescope image of cracking and delamination of the paint in the 1 mil gap Test 1 mockup after two thermal cycles to 550'F.

Figure 3-6 Borescope image of cracking and delamination of the paint in the 10 mU gap Test 1 mockup after two thermal cycles to 550 0 F.

3-13

Y4 Figure 3-7 Photograph of the painted 1 mil gap Test 2 mockup after removal of the masking tape.

Figure 3-8 Photograph of the painted 10 mil gap Test 2 mockup after removal of the masking tape.

3-14

400 350 300 u-o 250 200 CL a)

I--

150 100 50 0-0 20 40 60 80 100 120 140 160 Time, hours Figure 3-9 Plot of the mockup temperature versus time during thermal cycling of the 1 mil gap Test 2 mockup.

400 350 300 L-250 a)

C- 200 E

F-150 100 50 ....

0 20 40 60 80 100 120 140 160 Time, hours Figure 3-10 Plot of the mockup temperature versus time during thermal cycling of the 10 mU gap Test 2 mockup.

3-15

Figure 3-11 Borescope image of the paint condition in the 1 mil gap Test 2 mockup after thermal cycling to 350'F.

Figure 3-12 Borescope image of the paint condition in the 10 mil gap Test 2 mockup after thermal cycling to 350°F.

3-16

Figure 3-13 Borescope image of the apparent wet spot present in the 10 mil gap Test 2 mockup after initiation of flow into the annulus but before closure of the bypass valves.

Figure 3-14 Borescope image of three leaks in the 10 mil gap Test 2 mockup that formed after closure of the bypass valves.

3-17

Figure 3-15 Borescope image of multiple leaks in the 10 mil gap Test 2 mockup that formed after closure of the bypass valves.

Figure 3-16 Borescope image of coolant leaking from around the annulus exit in the 10 mil gap Test 2 mockup during the ambient temperature test.

3-18

Figure 3-17 Borescope image of boric acid deposits around the annulus exit in the 10 mil gap Test 2 mockup that formed during heating of the mockup to 350°F by evaporation of the coolant that leaked from the annulus during the ambient temperature test.

Figure 3-18 Borescope image of steam leaking out of the annulus exit in the 10 mil gap Test 2 mockup during the elevated temperature test.

3-19

Figure 3-19 Borescope image of boric acid deposits on the nozzle surface beneath the steam leak in the 10 mil gap Test 2 mockup after 15 minutes of leakage.

3-20

ta)

(b)

Figure 3-20 Borescope images of boric acid deposits (a) around the annulus exit and (b) on the nozzle surface beneath the steam leak in the 10 mil gap Test 2 mockup after 75 minutes of leakage.

3-21

Figure 3-21 Front view of the bottom of the 10 mil gap Test 2 mockup post test.

Figure 3-22 Right side view of the bottom of the 10 mil gap Test 2 mockup post test.

3-22

Figure 3-23 Left side view of the bottom of the 10 mil gap Test 2 mockup post test.

Figure 3-24 Back view of the bottom of the 10 mil gap Test 2 mockup post test.

3-23

Figure 3-25 Stereomicroscope image of deposits present along the primary leak sites along the front of the annulus exit on the 10 mU gap Test 2 mockup.

Figure 3-26 Stereomicroscope image of a circumferential crack in the paint adjacent to the deposits present over the primary leak sites along the front of the annulus exit on the 10 mil gap Test 2 mockup.

3-24

Figure 3-27 Stereomicroscope image of a circumferential crack in the paint along the annulus exit on the left side of the 10 mil gap Test 2 mockup.

Figure 3-28 Stereomicroscope image of circumferential cracks extending beyond the deposits present at a secondary leak site along the back of the annulus exit on the 10 mil gap Test 2 mockup.

3-25

Figure 3-29 Stereomicroscope image of linear cracks present in the paint remote from the annulus on the 10 mil gap Test 2 mockup.

3-26

(a)

(b)

Figure 3-30 Stereomicroscope images of two perforations present in the paint beneath the area of heavy deposits at the primary leak site on the 10 mil gap Test 2 mockup after deposit removal.

3-27

Figure 3-31 Stereomicroscope image of a circumferential crack present beneath deposits at a secondary leak site along the back side of the annulus on the 10 mil gap Test 2 mockup after deposit removal.

3-28

(a)

(D)

Figure 3-32 Stereomicroscope images of the paint penetration into the annulus gap on the 10 mil gap Test 2 mockup. Penetration depths of 3.2 mm and 3.9 mm were measured in (a) and (b), respectively.

3-29

Figure 3-33 Borescope image of leakage present in the 1 mil gap Test 2 mockup after initiation of flow into the annulus but before closure of the bypass valves.

Figure 3-34 Borescope image of coolant leaking from around the annulus exit in the 1 miu gap Test 2 mockup during the ambient temperature test.

3-30

(a)

MD Figure 3-35 Borescope images of boric acid deposits around the annulus exit in the 1 mU gap Test 2 mockup that formed during heating of the mockup to 350'F by evaporation of the coolant that leaked from the annulus during the ambient temperature test.

3-31

Figure 3-36 Borescope image of steam leaking out of the annulus exit in the 1 mil gap Test 2 mockup during the elevated temperature test.

3-32

(a)

(b)

Figure 3-37 Borescope images of boric acid deposits (a) on the nozzle surface beneath the steam leak and (b) around the annulus exit in the 1 mil gap Test 2 mockup after 15 minutes of leakage.

3-33

ta)

(b)

Figure 3-38 Borescope images of boric acid deposits (a) on the nozzle surface beneath the steam leak and (b) around the annulus exit in the I mil gap Test 2 mockup after 40 minutes of leakage.

3-34

Figure 3-39 Front view of the bottom of the 1 mil gap Test 2 mockup post test.

Figure 3-40 Right side view of the bottom of the 1 mil gap Test 2 mockup post test.

3-35

Figure 3-41 Left side view of the bottom of the 1 mil gap Test 2 mockup post test.

Figure 3-42 Back view of the bottom of the 1 mil gap Test 2 mockup post test.

3-36

Figure 3-43 Stereomicroscope image of deposits present along the front of the annulus exit on the 1 mil gap Test 2 mockup. Note the area of bare metal visible at the base of the nozzle near the center of the image.

Figure 3-44 Stereomicroscope image of deposits and a circumferential crack present along the left side of the annulus exit on the 1 mil gap Test 2 mockup.

3-37

Figure 3-45 Stereomicroscope image of deposits present along a primary leak site near the back of the annulus exit on the 1 mil gap Test 2 mockup.

Figure 3-46 Higher magnification stereomicroscope image of the center of Figure 3-45 showing an apparent perforation through the paint.

3-38

Figure 3-47 Stereomicroscope image of deposits present at a primary leak site along the back of the annulus exit on the 1 mU gap Test 2 mockup.

Figure 3-48 Higher magnification stereomicroscope image of the center of Figure 3-47 showing two apparent perforations through the paint.

3-39

Figure 3-49 Stereomicroscope image of linear cracks present in the paint remote from the annulus on the 1 mil gap Test 2 mockup.

Figure 3-50 Stereomicroscope image of an area of bare metal along the front of annulus on the 1 mil gap Test 2 mockup following deposit removal.

3-40

Figure 3-51 Stereomicroscope image of a circumferential crack present along one side of the annulus on the 1 mil gap Test 2 mockup following deposit removal.

Figure 3-52 Stereomicroscope image of two apparent perforations through the paint at a leak site along the back side of the annulus on the 1 mil gap Test 2 mockup after deposit removal.

3-41

(b)

Figure 3-53 Stereomicroscope images of the paint penetration into the annulus gap on the I mil gap Test 2 mockup. Penetration depths of 2.7 mm and 2.5 mm were measured in (a) and (b), respectively.

3-42

(a)

(b)

Figure 3-54 Stereomicroscope images of pores present in the paint over the (a) 1 mil and (b) 10 mil annuls gap.

3-43

400 350 300 IL 0

250

a. 200 E

F-150 100 50 0 20 40 60 80 100 120 140 160 Time, hours Figure 3-55 Graph of the mockup temperature versus time during the thermal cycling of the 1 mil gap Test 3 mockup.

400 350 300 IL 0

6 250-

0. 200 E

a) 1--

150 100 -

50 0 20 40 60 80 100 120 140 160 Time, hours Figure 3-56 Graph of the mockup temperature versus time during the thermal cycling of the 10 mil gap Test 3 mockup.

3-44

Figure 3-57 Stereomicroscope image of typical circumferential cracking present in the paint over the annulus opening following thermal cycling of the 10 mil gap Test 3 mockup.

Figure 3-58 Borescope image of the leak site in the 1 mil gap Test 3 mockup 12 seconds after it formed.

3-45

Figure 3-59 Borescope image of the leak site in the 1 mil gap Test 3 mockup 1 minute and 11 seconds after it formed.

Figure 3-60 Borescope image of deposits on the bottom of the LAS ring adjacent to the leak site in the 1 mil gap Test 3 mockup 1 minute and 49 seconds after the leak formed.

3-46

Figure 3-61 Borescope image of deposits on the nozzle surface beneath the leak site in the 1 mil gap Test 3 mockup 2 minutes and 58 seconds after the leak formed.

3-47

100 -

80 60 40 20 0

14:00:00 15:00:00 16:00:00 17:00:0(

Time, hours:minutes:seconds (a) 100 -

80 60 40 20 0

-20 -

0 20 40 60 80 100 120 Time, minutes (b)

Figure 3-62 Annulus pressure versus time plots for the I mil gap Test 3 experiment.

3-48

(a)

(b)

Figure 3-63 Borescope images of deposits (a) on the bottom of the LAS ring and (b) on the nozzle surface adjacent to the leak site in the 1 mil gap Test 3 mockup at the completion of the experiment.

3-49

Figure 3-64 Front view of the bottom of the 1 mil gap Test 3 mockup post test.

Figure 3-65 Right side view of the bottom of the 1 mil gap Test 3 mockup post test.

3-50

Figure 3-66 Left side view of the bottom of the 1 mil gap Test 3 mockup post test.

Figure 3-67 Back view of the bottom of the 1 mil gap Test 3 mockup post test.

3-51

Figure 3-68 View of the leak site on the bottom of the 1 mil gap Test 3 mockup post test.

Figure 3-69 Low magnification stereomicroscope image of deposits at the leak site in the 1 mil gap Test 3 mockup.

3-52

ta)

(b)

Figure 3-70 Higher magnification stereomicroscope images of a single slit in the paint at the leak site in the 1 mil gap Test 3 mockup.

3-53

(b)

Figure 3-71 Stereomicroscope images of the leaksite in the 1 mil gap Test 3 mockup. Note the single slit and the appearance of rumpling adjacent to the slit.

3-54

Figure 3-72 Stereomicroscope image of the paint penetration into the annulus gap on the 1 mil gap Test 3 mockup. A penetration depth of 9 mm was measured in this location.

Figure 3-73 Borescope image of apparent damage to the paint on the nozzle surface, identified by the arrows, following heating to 350'F but prior to the admission of liquid into the annulus of the 10 mil gap Test 3 mockup.

3-55

Figure 3-74 Borescope image of boric acid deposits present along the front of the nozzle on the 10 mil gap Test 3 mockup after heating to 350°F but prior to the admission of liquid into the annulus following replacement of the orifice.

Figure 3-75 Borescope image of boric acid deposits present along the left side of the nozzle on the 10 mil gap Test 3 mockup after heating to 350°F but prior to the admission of liquid into the annulus following replacement of the orifice.

3-56

Figure 3-76 Borescope image of boric acid deposits present along the right side of the nozzle on the 10 mil gap Test 3 mockup after heating to 350OF but prior to the admission of liquid into the annulus following replacement of the orifice.

Figure 3-77 Front view of the bottom of the 10 mil gap Test 3 mockup post test.

3-57

Figure 3-78 Right side view of the bottom of the 10 mil gap Test 3 mockup post test.

Figure 3-79 Left side view of the bottom of the 10 mil gap Test 3 mockup post test.

3-58

Figure 3-80 Back view of the bottom of the 10 mil gap Test 3 mockup post test.

Figure 3-81 Low magnification stereomicroscope image of boric acid deposits present along a region of damaged paint along the front of the nozzle on the 10 mil gap Test 3 mockup.

3-59

Figure 3-82 Low magnification stereomicroscope image of boric acid deposits present along a region of damaged paint along the left side of the nozzle on the 10 mil gap Test 3 mockup.

Figure 3-83 Higher magnification stereomicroscope image of boric acid deposits present along a region of damaged paint along the left side of Figure 3-81.

3-60

Figure 3-84 Higher magnification stereomicroscope image of boric acid deposits present along a region of damaged paint along the right side of Figure 3-81.

Figure 3-85 Low magnification stereomicroscope image of boric acid deposits present along a region of the annulus where four holes are evident in the paint covering the annulus exit on the 10 mil gap Test 3 mockup.

3-61

Figure 3-86 Higher magnification stereomicroscope image of the single hole in the paint on the left side of Figure 3-84.

Figure 3-87 Higher magnification stereomicroscope image of the two holes in the paint in the center of Figure 3-84.

3-62 I I

Figure 3-88 Higher magnification stereomicroscope image of the single hole in the paint on the right side of Figure 3-84.

Figure 3-89 Low magnification stereomicroscope image of the area shown in Figure 3-84 following removal of the boric acid deposits.

3-63

Figure 3-90 Low magnification stereomicroscope image of the area shown in Figure 3-80 following partial removal of the boric acid deposits.

Figure 3-91 Low magnification stereomicroscope image of the area shown in Figure 3-81 following partial removal of the boric acid deposits.

3-64

Figure 3-92 Stereomicroscope image of the paint penetration into the annulus gap on the 10 mil gap Test 3 mockup. A penetration depth of 8 mm was measured in this location.

3-65

4 DISCUSSION 4.1 Thermal Cycling Damage Post test examinations of both the 1 mil and 10 mil gap mockups used in Test 2 identified circumferential cracking of the paint over the annulus, which served as the leak sites. Although neither of these mockups were examined between the thermal cycling and the start of the leak tests, the evidence of some minor leakage while the annulus was being filled before pressurization suggests that the circumferential cracks formed during the thermal cycling. Both of the Test 2 mockups used an o-ring seal at the top of the annulus, rather than the welded seal which is present in the actual BMI nozzles. The o-ring seal produces a relatively flexible connection between the top of the nozzle and the LAS ring while the welded seal would produce a more rigid connection. It is possible that the circumferential cracking formed during thermal cycling of the Test 2 mockups was the result of the increased differential movement between the nozzle and the LAS ring brought about by the use of the o-ring seal. To test this hypothesis, a welded seal was used in both of the Test 3 mockups. While the welded 1 mil gap Test 3 mockup did not develop any circumferential cracking within the paint over the annulus during thermal cycling, circumferential cracking was evident after the thermal cycling of the 10 mil gap Test 3 mockup. This cracking was present both in the paint over the annulus gap, as was seen in the Test 2 mockups, and in the paint on the nozzle 1 to 2mm above the annulus gap. It can, thus, be concluded that circumferential cracking can be induced in the rigid welded seal configuration, even with the very mild thermal cycles utilized in both Test 2 and 3.

4.2 Leak Time and Pressure The time required to obtain the first visible leak through the paint covering the annulus and the annulus pressure at the time the leak appeared for each test completed are summarized in Table 4-1, It is obvious from these data that visible leaks developed quite rapidly at the relatively low flow rates of 0.001 gpm used in this study. For tests that started with an annulus already filled with water, the time to the first visible leak ranged from 0 seconds to 17 seconds. While starting with an empty annulus substantially increased the time to the first visible leak, the 1,141 seconds that elapsed before the first leak developed in the 1 mil gap mockup in Test 3 is still considered to be a very short time. This time to develop the first leak should scale with the leak rate into the annulus. Hence, even with an order of magnitude decrease in the leak rate to 0.0001gpm, the time to develop the first leak would still be only 11,000 seconds, or three hours.

The annulus pressures needed to produce leakage through the paint were also quite low. The ambient temperature tests, in which circumferential cracks likely formed in the paint during the thermal cycles, produced leaks at only 5 and 19 psi. The pressures obtained in the subsequent elevated temperature tests of the Test 2 mockups were substantially higher at 52 and 149 psi.

This increase suggests that boric acid deposits formed from prior leaks can temporarily seal the prior leak path and lead to slight increases in the pressure required to initiate a new leak.

4-1

However, at 52 and 149 psi, the pressure to initiate a new leak was still quite low. In the absence of any thermal cycling induced damage in the paint, the pressure needed to produce leakage through the paint was still quite low. The stereomicroscope examination of the 1 mil gap mockup used in Test 3 did not find any evidence of paint damage following completion of the thermal cycles. Nonetheless, a pressure of only 85 psi was required to create a leak through the undamaged paint, indicating that the rupture strength of the paint is very low at temperatures of 350'F and above.

4.3 Leak Paths Four different leak paths were observed in this study. Both of the Test 2 mockups leaked through thermal cycling induced circumferential cracks present in the paint over the annulus. Some widening of the crack through delamination and removal of paint along its edge developed driven by the escaping steam. In the 1 mil gap Test 3 mockup, which did not contain any thermal cycling induced cracking, the steam worked its way under the paint on the nozzle, lifting the paint locally to form a channel which ultimately ruptured to produce the leak path. The primary leak path on the 10 mil gap Test 3 mockup was through thermally induced cracking that was present in the paint on the nozzle surface above the annulus gap. The steam appears to have worked its way under the paint on the nozzle before escaping through the thermal induced cracks. Secondary leak paths on the 10 mil gap Test 3 mockup were through a number of roughly circular holes that had formed in the paint directly over the annulus opening.

4.4 Deposit Formation A single test,Test #4, was performed during the MRP-288 tests at the 0.001gpm leak rate that was used throughout the painted annulus tests described in this report [3]. The evolution of boric acid deposits around the annulus exit during the course of this MRP-288 test is shown in the borescope pictures present in Figures 4-1 through 4-3. Boric acid deposits were visible around the annulus exit during the second day of the test, as shown in Figure 4-1. The deposits showed considerable volume increase by the seventh day of the test, as shown in Figure 4-2, and continued to increase in volume out to day 24 of the test, as shown in Figure 4-3. For comparison, the deposits present after 75, 40 and 75 minutes of leakage during the three painted annulus tests which experienced steam leakage are shown in Figures 4-4 through 4-6. These deposits are clearly visible in the borescope images and are similar in size and volume to the deposits that were present during day 2 of MRP-288 Test 4, which was run at the same leak rate but without any paint covering the annulus exit. It, thus, appears that the presence of the paint on the bottom of the mockup does not alter either the volume or the location of the boric acid deposits that form from the steam escaping from the annulus.

4-2

Table 4-1 Time to leak and maximum annulus pressure for the painted annulus tests.

Maximum Thermal Annulus Annulus Cycling Mockup Coolant Time to Pressure Test Gap Tmax 'F, # Starting Temperature Temperature Leak at Leak Number (mils) of Cycles Condition OF OF (seconds) (psi) 1 1 550/2 Not tested due to excessive paint damage in thermal cycle 1 10 550/2 Not tested due to excessive paint damage in thermal cycle Full 2 1 350/6 annulus 66 65 0 19 Full 2 1 - Full annulus 350 550 8 149 Full 2 10 350/6 auls annulus 62 63 8 5 2 10 -F 350 550 17 52 annulus 3 1 350/6 Empty 350 550 1,144 85 annulus 3 10 350/5 Empty 350 550 During I annulus heating 4-3

Figure 4-1 Borescope image of deposits present in the annulus exit area during day 2 of MRP-288 Test 4.

Figure 4-2 Borescope image of deposits present in the annulus exit area during day 7 of MRP-288 Test 4.

4-4

Figure 4-3 Borescope image of deposits present in the annulus exit area during day 24 of MRP-288 Test 4.

Figure 4-4 Borescope image of deposits present in the annulus exit area of the 10 mil gap Test 2 mockup after 75 minutes of leakage.

4-5

Figure 4-5 Borescope image of deposits present in the annulus exit area of the 1 mil gap Test 2 mockup after 40 minutes of leakage.

Figure 4-6 Borescope image of deposits present in the annulus exit area of the 1 mil gap Test 3 mockup after 75 minutes of leakage.

4-6

5 CONCLUSIONS The following conclusions have been drawn from the results presented in this report.

1. Paint applied over the annulus exit on the bottom of the mockup was not an effective barrier for either liquid water or steam exiting the annulus. Leakage through the paint started quickly when pressure was applied, even under ambient temperature conditions. Low annulus pressures, 149 psi maximum, were sufficient to create the leak paths through the paint.
2. Thermal cycling can produce cracking of the paint over the annulus. These cracks serve as effective leak paths for effluent trying to leave the annulus.
3. Even in the absence of prior degradation, the paint does not provide an effective barrier to prevent or delay steam from exiting the annulus at elevated temperatures.
4. Once leaks form, the paint does not appear to alter either the location or the volume of the boric acid deposits that form from the steam escaping from the annulus.
5. If the presence of a stress corrosion crack provides a path for primary coolant to enter the annulus surrounding a BMI nozzle, the presence of paint on the bottom of the reactor around the nozzle should not provide any significant impediment to the steam exiting the bottom of the annulus nor to leak detection by visual inspection for the presence of deposits around the nozzle.
6. The small annulus pressure and time required to produce leakage through the paint indicates that the presence of the paint should not alter the boric acid wastage processes or rates within the annulus from those that would occur in an unpainted annulus.

5-1

6 REFERENCES

1. PWR Reactor Pressure Vessel (RPV) Upper Head Penetration Inspection Plan (MRP-75):

Revision 1, EPRI, Palo Alto, CA 2002. 1007337.

2. Reactor Vessel Head Boric Acid Corrosion Testing (MRP-266) Task 4: Full-Scale Mockup Testing, EPRI, Palo Alto, CA 2009. 1019085.
3. Materials Reliability Program: Reactor Vessel Bottom Head Boric Acid Corrosion Testing (MRP-288): Bottom Mounted Instrument Nozzle Mockup Testing. EPRI, Palo Alto, CA 2010.
4. Materials Reliability Program: Reactor Vessel Bottom Mounted Nozzle Boric Acid Corrosion Testing (MRP-268): Design and Analysis of Full-Scale BMN Mockups. EPRI, Palo Alto, CA 2010. 1020483.

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