ML20214N332

Rev 1 to Fuel & Plant Matls Technology,Corrosion Evaluation of Oyster Creek Drywell

ML20214N332
Person / Time
Site:	Oyster Creek
Issue date:	03/06/1987
From:	Gordon B, Gordon G GENERAL ELECTRIC CO.
To:
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ML20214N301	List: ML20214N297 ML20214N318 ML20214N332
References
87-178-003, 87-178-003-R01, 87-178-3, 87-178-3-R1, NUDOCS 8706020140
Download: ML20214N332 (96)

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{{#Wiki_filter:ff ' A GEN ER AL $ ELECTRIC rarMT Transmittai NUCLEAR ENERGY BUSINESS OPERATIONS No. 87-178-003 Rev. 1 FUEL & PLANT MATERIALS TECHNOLOGY CORROSION EVALUATION OF THE OYSTER CREEK DRYWELL Date: March 6, 1987 Prepared By: B.M. Gordon, Principal Engineer Plant Materials Performance Approved By: G.M. Gordon, Manager Fuel & Plant Materials Technology GENERAL ELECTRIC-COMPANY LEGAL INFORMATION NOTICE The only undertakings of General Electric Company (GE) respecting information in this document are contained in the agreement between GPU Nuclear and GE and nothing contained in this document shall be construed as changing the agreement. The use of this information for any purpose other than that for which it is intended, is not authorized and with respect to any unauthorized use GE makes no representation or warranty, (express or implied) with respect to the completeness, accuracy, or usefulness of the information contained in this document, or that the use of such information may not infringe privately owned rights, nor does GE assume any responsibility for liability or damage of any kind which may result from the use of any of the information contained in this document. 8706020140 870529 PDR ADOCK 05000219 P PDR, BMG8706.11 NEo 807 (REV 10/81) h

rr l F&PMT Transmittal No. 87-178-003 Rev. 1 l

1.0 INTRODUCTION

GPU Nuclear's Oyster Creek BWR is characterized by a Mark I containment as shown in Figure 1. During the 1980 refueling outage water was noted around penetrations at elevation 86'0" and running down the wall to floor elevation 75'3". Water was also observed at a penetration at elevation 47'0" and running down the wall to floor elevation 23'6".1 The presence of water at these locations indicated that an intrusion of water into the annular space between the drywell shell and concrete shield wall had occurred. Water collection was also observed during this outage on the torus room floor which originated from the leak drains in bays 3, 11 and 15, as shown in Figure 2. Water on the torus room floor was also noted following construction. When water samples were withdrawn from the drains in 1980 and were subsequently radiologically analyzed, the results indicated an activity level similar to primary water. It was concluded at this time that the probable sources of water were the (1) equipment storage pool, (2) reactor cavity, or (3) fuel pool. It was further concluded that the leakage occurred only during refueling when the reactor cavity, the equipment storage pool, and the fuel pool are flooded. When water was again noted leaking from the sand bed drains during the refueling outage in 1983, it was decided that corrosion of the drywell shell could be a concern and an inspection would be performed during the next outage (1986). However, prior to discussing the details of the program, it is critical to examine the geometrical configuration and construction of the Oyster Creek drywell. 2.0 OYSTER CREEK PRIMARY CONTAINMENT GEOMETRY I The Oyster Creek Mark I containment consists of a pressure suppression system with two large chambers as illustrated in Figure 3. The main chamber is 70' diameter spherical shell with a 33' diameter by 23' high cylindrical l l i i s 1 F&PMT Transmittal No. 87-178-003 Rev. I shell extending from the top. The pressure absorption chamber is a shell in the shape of a 30' diameter torus located below and around the base of the drywell. The two chambers are interconnected by 10 vent pipes 6'6" in diameter equally spaced around the circumference of the pressure absorption chamber, Figure 4. The drywell interior is filled with the concrete to an elevation 10'3" to provide a floor. Concrete curbs follow the contour of the vessel up to elevation 12'3" with cutouts around the vent lines, Figure 5. The drywell exterior is encapsulated in concrete of varying thickness from the base elevation up to the elevation of the top head, Figure 3. From this juncture, the concrete continues vertically to the level of the top of the spent fuel pool. The proximity of the concrete surface to the shell varies with elevation. The concrete is in full contact with the shell over the bottom of the sphere at its invert elevation 2'3" up to elevation 8'11.25". At that transition, the concrete is radially stepped back 15" to create a pocket which continues up to elevation 12'3", Figure 4. This pocket is filled with sand which creates a cushion to smooth the transition of the shell plate from a fully clamped condition between two concrete masses to a free standing condition. The sand pocket is connected to drains to allow drainage of any water which might enter the sand. It is within this sand cushion contact area with the drywell shell where corrosion was identified. Above elevation 12'3" the concrete is radially stepped back 3" from the shell. This gap is created during construction by applying a compressible, inelastic material to the outside of the shell prior to concrete installation. This material was later permanently compressed by controlled vessel expansion to create a gap between the vessel and the concrete V e F&PMT Transmittal No. 87-178-003 Rev. 1 2.1 Drywell Materials 2.1.1 Drywell Steel The drywell shell is fabricated of ASTM A212 B made to ASTM A-300 requirements. This material is basically a high tensile (70 Kai) carbon-silicon steel with a basic composition listed in Table 1 and is equivalent to SA-'516 Grade 70 steel. 'The shell was coated on the inside surface with an inorganic zine (Carboline Carbozine 11) and with " Red Lead" (Pb 0 ) primer identified as TT-P-86C Type I on the outside surface. The red 34 lead coating covered the entire exterior of the vessel from elevation 8'11.25" to 94'. 2.1.2 Sand Cushion The sand cushion was filled with sand specified as ASTM 633 from elevation 8'11.25" to elevation 12'3". The sand was a natural sand composed primarily of silica (SiO ) with some alumina (A1 0 ). Since the sand was 2 33 stored at a local dealer uncovered and exposed to the environment during storage and installation, it is a safe assumption that the sand was placed into the sand cushion region in a moist or wet condition. There is no information concerning the method or condition of-the backfilling of the sand - into the sand cushion gap. Both GPUN and GE performed leachate studies on the sand. Table 2 presents the GPUN leachate results on various sand samples plus an insulation sample which will be discussed in Section 2.1.3. The results of the GPUN analysis of the wet Bay 11 sand indicates measurable quantities of Na, K, Ca, Pb, Mg and C1 which are naturally occurring in sand. The Mg and C1 are also present in the insulation as will'be discussed in Section 2.1.3. The Fe present is probably from any corrosion product incorporated into the sand; the Pb is from the red lead primer. ns,

I e F&PMT Transmittal i-No. 87-178-003 Rev. 1. The sand samples from core samples 19C and ISA (to be' discussed in a detail in Section 5.0) also indicate nominal values of contaminants with the exception of plug 19C which has a significantly higher Fe content. Since this 4 plug is characterized by considerable corrosion, this result is not unexpected. Plug 15A, which initially was considered " pitted" but actually had inclusions with essentially no corrosjan, has a significantly lower Fe content in the sand behind it. 4 GPUN also performed an energy-dispersive x-ray analysis (EDX or EDAX) i with a scanning electron microscope (SEM) on some sand and small pebbles as i shown in Figure 6. The EDAX spectrum confirms the presence of silica and alumina plus chloride. The presence of C1 is consistent with the leachate. analysis. The GE leachate chemical analysis of the sand cushion specimen (plus j other samples to be discussed later) is presented in Table 3. ' Table 4 lists the ionic constituents of leachate samples in units of mil 11 equivalents per i liter. These values are calculated from the chemical analysis results using-some assumptions of metal species. Note that this charge balance calculation sum of the anions differs from the sum of the cations by no more than 14% for any of the test solutions. This degree of agreement tends to verify.the quality of the chemical analysis. Finally, Table 5 provides the chemical i analysis results of Table 3 expressed relative to the original samples by multiplying the concentrations reported for the leachates (in ag/L) by the leachate volume (L) then dividing by the weight of the leached material (g). A comparison of the GE sand leachate analysis " torus sand", with the Table 5, GPUN analysis Bay 11 sand, Table 2, reveals similar results, (note ppe vs. ppb units). The major difference, albeit of little technical I consequence, is the level of Fe. The Bay 11 sand contains 1.0-5.0 ppb of Fe f while the GE analysis of the torus sand contained <0.04 ppb Fe. Since the sand sample may be from different locations the results are not significant. The lead content in the Bay 11 sand sample also appears to be higher. I

e ?&PMT Transmittal No. 87-178-003 Rev. I 2.1.3 Insulation At all elevations above the sand layer, the external concrete mass is set back from the surface at the steel shell an amount calculated to allow unimpeded expansion of the shell during any design condition. As noted in ~ Section 2.0, this gap was created by applying a compressible, inelastic material to the exterior surface of the vessel prior to pouring concrete. The material properties were selected to provide resistance to crushing by the pressure induced by the head of concrete but of low compressive strength to allow collapsing by induced vessel expansion. Design considerations necessitated that a gap of 2" was required from elevation 12'3" to elevation 23'6" and a gap of 3" above 23'6". The criteria used to select the gap material was as follows: 1. Tight adherence to curved, painted steel plate surfaces in horizontal and vertical positions. 2. Insignificant deformation under fluid pressure of wet concrete estimated at 3 psi. 3. Would be reduced in thickness inelastically by approximately one inch from an initial thickness of 2 to 3 inches under a pressure of not more than 10 psi. 4. Dimensionally stable at the reduced thickness without significant flaking or powdering. 5. Unaffected by long term exposure to radiation and heat. 6. Unaffected when exposed on the vessel prior to concrete installation. l t m

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h t *'4 The2"gapdisc$sedabovawasformedbyusingOwens-Corning FiberglasalSF Vapor Sedl Duct Insu1 Pion and wasl applied to the vessel shell from elev tion 12'3" to 23'6". The material was applied as individual boards a .a [ 2"' thick with a factory applied laminated asphalt kraft paper (high in sulfur and chlorine) water proof exterior,-face and was attached to the vessel with mastic and insulation pins. The fiberglass strands were embedded in phenol formaldehyde. Joints between'.the boards, edges and penetrations were sealed with glass fabric reinforced mastic. i 2.' 1. 3. 2 Firebar-D Insulation l' 2.1.3.2.1

Background

s The gap material used above elevation 23'6" was Firebar-D,'a proprietary asbestos fiber-magnesite cement product applied as a-spray coat. The manufacturer of this material was All Purpose Fireproofing Corporation. The material was subsequently modified by Certified Industrial Products,.Inc. to achieve a reduced density. The solid materials, asbestos fibers, magnesite and magnesium sulfate (%75% asbestos), were premixed and combined in a mortar mixing machire with water and, to control density, with foam (aerosol PK, a protein, as a foaming agent) to form a slurry suitable for spray application. The first coat (i inch thick) was standard density while the second and third coat (one inch thick each) was at a reduced density. After application and drying, the material surface was faced with Griffolyn (chloride content not known) 4 mil clear polyethylene sheet with all edges sealed by tape and held in by insulation pins. The polyethylene sheets formed.the bond-breaker for the concrete pour. It is important to note that the Firebar-D is said to be 75% asbestos in magnesite. To a geologist, magnesite is the mineral form of magnesium carbonate,-MgC0. Complete calcination or dead burning of magnesite produces 3 magnesium oxide, Mg0. Commercially however, magnesite refers to " dead burnt"

4 F&PMT Transmittal No. 87-178-003 Rev. 1 magnesium oxychloride, also known as Sorel's cement. This material is produced by the exothermic action of a 20% solution of magnesium chloride, MgC1, and a blend of magnesia, Mgo, by calcining magnesite and magnesia 2 obtained from brines 3 Mg0+MgC1 +11 H O ---) 3 Mg0eMgC1 11 H 0. 2 2 2 2 The resulting crystalline oxychloride contributes the cementing action to the commercial cements. The product is hard and strong but is dimensionally unstable, facks resistance to weathering, and most importantly is readily attacked by water which leaches out the MgC1 and thus is highly 2 corrosive. 2.1.3.2.2 Firebar-D Analysis Leachate analysis of the Firebar-D was performed by both GPUN and GE. As shown in Table 2 for the GPUN analysis of this insulation, Firebar-D consisted of a mixture of fiber, foam and concrete had high levels Na, K, Ca, Mg, C1, NO, SO and total organic carbon (TOC). The Na, K and Ca are 3 4 centained in asbestos. The Mg is also present in asbestos and of course the Firebar-D. The C1 and SO are major compasitional factors of the Firebar-D. 4 The TOC of 1056 ppm is most likely due to the foaming agent Aerosol PK which is a protein. [This material along with the sulfa m could serve as a food for any microbiological 1y influenced corrosion (MIC). However, this subject is beyond the scope of this report.] Although the source of the nitrate is not obvious, it is present in small quantities in seawater. The GE analysis of a 14 gram insulation leachate is shown in Tables 3-5. A comparison between the GPUN and GE results, Table 2 and 5, respectively, revealed similar results. For example, 573 vs 610 ppb C1, 1936 vs. 1400 ppb Mg, 2850 vs. 2500 SO, 132 vs. 130 NO3, 1056 vs. 900 ppb total 4 organic carbon, etc. were observed for the GPUN and GE analysis, respectively. 4 F&PMT Transmittal-No. 87-178-003 Rev.-1 4 3.0 POTENTIAL SOURCES OF WATER INTRUSION 3.1 Leakage Paths and History As noted in Section 1.0, leakage of water from the sand bed drains were observed during the 1980 and 1983 refueling outages. A series of. investigations were performed by GPUN to identify the source of the water and its leak' path. Since the same range of radioactivity was found in this leakage water as is found within. the reactor, the leak path was believed to have been from the reactor cavity located immediately above the drywell. This cavity is filled with water during refueling operations. It.was believed that i a leak from this cavity through the bellows seal, Figures 7 and 8, at the bottom drained into the space between the drywell and the space filled with Firebar-D. Extensive leak tests finally revealed that the most probable source of the water was the drain line gasket, Figure 8. This gasket was replaced and subsequent leak tests performed on the bellows revealed no I additional leaks. Inspections of the areas-previously characterized by l 1eakage indicated that the leakage had been arrested. However, this history of leakage, which may have initiated at the first refueling outage plus any condensation in the gap between the Firebar-D and the drywell shell, means that the Firebar-D could have been intermittently wetted and leached of corrosive MgC1 which collected in the sand' cushion. As 2 will be discussed later, the establishment of this electrolyte in the sand is 4 considered the key factor in the drywell corrosion phenomenon. 3.2 Leakage Water Analysis i During the 1986 Oyster Creek refueling outage, water samples were obtained from a drain line and analyzed by GPUN and GE. In addition to tritium, these samples were analyzed for contamir. ants. i [ The results of the GPUN analysis is shown in Table 6. Significant 4 are present. The sources of these substances amounts of Na, K, Mg, C1 and SO

s a F&PMT Transmittal No. 87-178-003 Rev. 1 include the natural substances found in sand, a marine environment and the Firebar-D. The conductivity is high (680-1100 uS/cm as compared to 0.2, 1, 70 and 1000 pS/cm for good reactor water, good quality distilled water, excellent quality raw water, and 0.05% Nacl solution, respectively) and thus clearly indicates that the drain line water would serve as a suitable electrolyte for corrosion. The results of the GE analysis, Table 3, of the leakage water again reveals similar results for elements K, Na, Ca, Mg, A1, C1, NO, SO, TOC and 3 4 conductivity. The only measurable differences between the two analyses was in the Fe and Sr. 3.3 Deposit Analysis Various scrapings from horizontal and vertical surfaces were obtained between the torus and drywell at Oyster Creek. These deposits were analyzed by inductive couple plasma by GPUN, Table 7, and by EDAX and leachate by GE, Tables 8 and 3, respectively. Table 7 reveals the presence of various metal oxides with Fe 0, hematite (" rust") being the dominant material for material 23 removed by Bay 7 and 11. The only unusual oxide is the B 0 which suggests 23 the presence of reactor water. The GE analysis of a scraping from Bay 7 only as investigated by EDAX, Table 8, revealed high percentages of Fe, C1, K, S and Pb. The results of the GE analysis is fairly consistent with GPUN's investigation although different analytical methods were utilized. The quantity of Fe is consistent and anticipated. The presence of lead, Pb, is consistent with the red lead primer coat. Manganese may be due to the presence of manganese sulfides in the steel. Although the existence of Na, C1, and K are consistent with the presence of Firebar-D, the presence of these l three elements plus bromine is suggestive of a marine environment since Br is also found in seawater. l The results of the leachate analysis of the Bay 7 deposit is presented in Table 5. The results are consistent with the other analytical results from F&PMT Transmittal 'No. 87-178-003 Rev. 1 [ this sample in that significant amounts of SO, C1, Ca, K and Na leached out 4 I of the specimen. Pb, B, Sr, Ba and Al were also identified. With the exception of Pb, all of these elements are present in seawater. 4.0 DRYWELL THICKNESS MEASUREMENTS Motivated by the presence of water in the drain lines and other penetrations, GPUN performed extensive ultrasonic thickness measurements of the drywell to determine if degradation was occurring. Approximately 1000 ultrasonic testing (UT) measurements were obtained through the use of.an .{ ultrasonic thickness gauge device (D-meter). The D-meter measures the time for a longitudinal ultrasound wave to travel to a reflection (backwall or midwall reflector) and-back. Expanded UT examinations were accomplished through the use of a "A-Scan" UT technique where the character, location and amplitude of various ultrasound reflectors are displayed on a cathode ray tube. The initial UT measurements (D-meter) were made from the inside of the drywell at elevations of 51' and the 11'3" sand cushion, Figure 9. The sand cushion measurements obtained in the bays corresponding to known water leaks indicated that wall thinning had occurred. Measurements just above these ares in the same plate and at the 51' elevation indicate nominal plate thicknesses. Measurements were obtained with both the inside surface coating of Carbo zine 11 in place and removed. As a result of the initial low thickness readings,. additional thickness measurements were obtained as described in detail elsewhere.I To determine the vertical profile of the thinning, a trench was excavated into the concrete floor in Bay 17 and Bay 5. Bay 17 was chosen since the extent of thinning at the floor level was the most severe. The additional thickness measurements indicated that thinning below the initial measurements were no more severe and become less severe at the lower portions of the sand cushion. Bay 5 was selected to determine if the thinning line was lower than the floor a

o a F&PMT Transmittal No. 87-178-003 Rev. I level in areas where no thinning was identified. No significant indication of thinning was found in the sub floor region of Bay 5. Aside from UT thickness measurements performed by the GPUN staff, independent analysis was performed by the EPRI NDE Center and the GE Ultra Image III "C" scan topographical mapping system. The EPRI investigation verified GPUN's thickness and mid-wall reflector 7 results and the GE mapping confirmed a corrosion transition at seven to eight inches up from the concrete curb in Bay 19. The Ultra Image results will be used as a baseline profile to track continued wastage. GPUN also used a UT integration method (30-70-70 technique) to detect minor changes in back wall surface conditions. This technique was able to verify the roughness condition of wastage and the light corrosion areas of the containment wall as compared to reference standards. Finally, UT investigations of various plate to plate welds and heat affected zones revealed no indications of wastage or cracking. 5.0 CORE SAMPLING To evaluate if the UT measurements were valid, characterize the form of damage, and determine the cause (i.e., due to the presence of contaminants, microbiological species, or both), it was considered prudent to obtain core samples from various bay locations. Areas that wer.e characterized by sharp deviations in thickness of less than half the 1.154" nominal wall were designated " pitted / inclusion" areas. Regions that had UT indications of thinning were designated as " wastage" areas. Regions above the wastage area and within the sand cushion region that appeared to have no thinning or " pitting" were also selected as candidate core sample sites. Table 9 summarizes the UT characterizations by bay number. Core samples of the drywell wall were obtained at seven locations. To produce an adequate sample size, an opening large enough to allow removal of sand samples and insertion of a miniature video camera and allow a simple plug j design, the sample diameter was optimized at 2" in diameter. Table 10 n.c

t F&PMT Transmittal: No. 87-178-003 Rev. summarizes the seven core sample locations, the. type of samples obtained and the organization who performed the subsequent analysis. ~The core samples were cut in such a manner.to eliminate any possible contamination from the cutting operation. ' Distilled water was used during the' initial cutting operation as a coolant.- The final cut'through the wall was performed without coolant and the shell temperature was maintained below l s150*F to prevent the premature death of any viable microrganisms. Biological' samples were taken from four plugs and analyzed by another party for GPUN. The next five sections present the results of the core sample analysis. 5.1 Core Sample 15A - Minimum Thickness Specimen - GPUN Core sample 15A which was removed from Bay 15 was the key specimen for detailed analysis. This'particular area was characterized by the lowest through-wall thickness (0.490") as observed randomly by UT examination, surrounded by adjacent areas with nominal thickness of 1.17". Therefore, the question was whether this area was suffering from some sort of localized " pitting" attack or did the plate in this location contain. inclusions. The removal of plug 15A immediately revealed that there was no pitting or in fact any serious corrosion attack. The sample measured 1.17" average thickness and was covered with a uniform dark brown (magnetic) scale. Elemental analysis of this oxide by EDAX indicated that Fe was'the major (>10 "/o) constituent, followed by Pb (>l "/o) from the red lead primer and traces (<1 "/o) of A1, Si, Ca, C1, K, S and Mn, Table 11. Figures 10 and 11 present overall cross-section view of plug 15A and detail region where EDAX was performed, respectively. Figure 12 presents the energy dispersion line profile of plug 15A which clearly reveals a constant low level distribution of C1 and a high level concentration of Fe in the scale. EDAX analysis _of a-sand sample from plug 15A revealed that Si was the major constituent (>10 "/o) with minor amounts of Al and Fe (>l "/o) and trace amounts of C1, K, Pb and Ti (<1 "/o), Table 12.

4 -l F&PMT Transmittal i No. 87-178-003 Rev. 1 f GPUN also~ prepared metallographic specimens from this core plug in both the rolling direction and perpendicular to the rolling direction, Figure

13. As shown in Figure 10 and 11, minor pitting (<5 mils) was observed on the-surface. The mid plane of the specimen was characterized by a -band of i

alustalde stringers, Figures 14 and 15. These inclusions are sufficiently -dense to produce a reflection for ultrasound. In fact, the measured depth of these inclusions correlated with the depth determined by the initial UT examination. The validity of the overall UT thickness measurements was also confirmed by actual thickness measurements. The ability of the A-scan to-identify areas of inclusions, as opposed to pits, was also confirmed. i 5.2 Core Sample 19C -- Wastate -- GPUN When core sample 19C was cut, GPUN noticed that a hard black crust remained in the hole at the sand interface. The crust was approximately 0.5" } thick and was subsequently removed for analysis. Other wastage samples ~were also characterized by this corrosion product crust. 4 Figure 16 presents an overall view of plug 19C. The surface has the classic appearance of general corrosion. The measured thickness was approximately 0.825" which corresponds with the UT. determination of 0.815". The surface was covered with a thick black powder deposit which varied in i thickness up to %30 mils. EDAX analysis of the surface, Table 11, revealed that again Fe was the major constituent (>10 */o) as was the case of plug 15A. However, for this wastage sample the minor element (>l "/o) was C1 and not Pb. Trace amount of A1, Si and Mn were also identified, Figure 17. A i cross-section of plug 19C, Figure 18, prepared through one of the valleys on j the corroded surface reveals the corrosion product. An EDAX analysis along the indicated profile location, Figure 19, reveals a chloride peak in a 2 mil t thick region adjacent to the steel surface. EDAX analysis of the magnetic crust / flake deposit removed with plug 19C revealed that the primary con-stituent was Fe (>10 "/o) with only trace amounts of Si and C1 (<1 "/o), Table l 13. The pH, as determined by litmus paper, of the scale was measured at 4. I-

F&PMT Transmittal No. 87-178-003 Rev. I Meta 11ographic examination of the plug sample 19C also revealed that scale contained manganese-sulfide inclusions, Figure 20, Manganese inclusions were also found beneath the surface of the plug, Figure 21. These two figures clearly indicate that the wastage is proceeding through the wall and is capable of retaining inert materials in the original position and orientation. This result also explains the presence of Mn in the EDAX analysis presented in Figure 17. 5.3 Core Sample 17D - Wastage - GE This plug sample was also characterized by general corrosion / wastage. The pre-removal UT thickness was determined to be approximately 0.840". Upon removal actual thickness measurement revealed an average thickness of 40.860". SEM examination of the surface of plug 17D, Figure 22, revealed a fairly uniform distribution of oxide particles. An EDAX analysi' of this surface revealed a high concentration of C1 (3.71 - 4.92 "/o) and Fe (92.73 - 94.60 "/o), Table 14. Similar results were obtained for an analysis, Figure 23, of the cross-section of the oxide, Table 15, where 3.45 "/o C1 and 94.40 "/o Fe was identified. This analysis confirms the GPUN studies on wastage sample 19C where a b4h chloride peak was associated with the significant general corrosion attack. The corrosion product crust removed from plug 17D was analyzed by both EDAX and x-ray diffraction (XRD). The EDAX analysis of the crust reveals that Fe is present in the highest concentrations (88.32 - 98.26 "/o), Table 16, followed by Mn (1.54 - 10.42 "/o), Si (0.00 - 0.63) and C1 (200 - 3800 ppm). XRD analysis of this dark brown to black crust was performed on magnetically separated material as discussed below. The results of the XRD analysis revealed that the non-magnetic aliquot was composed of major amounts of alpha quartz (a - SiO ) with small amounts of 2 face-centered-cubic (FCC) M 0 spinel type phase plus trace amounts (<2 "/o) 34 of an unidentified phase. The magnetic aliquot composition was essentially F&PMT Transmittal No. 87-178-003 Rev. 1 just the opposite of the non-magnetic sample, that is, the magnetic aliquot consisted of a major phase (>90 "/o) of FCC M 0 spinel with small to trace 34 amounts of a SiO. The lattice parameter value for the spinel phases was 2 determined to be a, = 8.387 2 0.004 A. This value is close to the lattice parameter of stoichiometric Fe 034 at a, = 8.3963 A. The slightly smaller measured lattice parameter of this magnetic phase can be most likely attributed to small amounts of other transition elements in substitutional solid solution with the major element Fe. It should also be noted that the error on the lattice parameter could indicate no change in composition has occurred and the spinel phase could be pure Fe 0. 34 Other compounds such as FeC1, FeC1, a Fe 0 and y Fe2 3 "*#* 2 3 23 specifically analyzed for in the sample, but none were identified with the possible exception of a weak trace of a Fe O. The detection limit for these 23 types of phase in this type of material is estimated to be one to two weight percent. Meta 11ogrpahic examination of plug 17D revealed similar corrosion product buildup as seen on wastage plug 19C, as seen by comparing Figure 18 with Figures 24 and 25. The microstructure of the steel, Figure 24, and the 81-84) were tyP cal for this type of steel. hardness values (R i B The leachate analysis of the sand behind plug 17D revealed significantly less contaminants than observed for plugs 19C and 15A. The only contaminant present in significant quantities is 19 ppm K, 9 ppm Na and 4 ppm Ca. The chloride content in this sand, 1.8 ppm, is significantly less than observed in the sand behind plugs 19C and 15A at 45 and 93 ppm, respectively. It should be noted, however, that the plug core sand samples were received in plastic jars and not as a core sample per se. Therefore, any higher concentration of contaminate adjacent at the plug / sand interface could have been diluted by mixing..

F&PMT Transmittal No. 87-178-003 Rev. 1 5.4 Core Sample 19A - Wastage - GE This sample was the second wastage sample received by GE for analysis. The pre-removal UT thickness measured by GPUN averaged 0.830". The post-removal average thickness was 0.847". SEM examination of the surface of plug 19A, Figure 26, revealed a surface which is quite different than that observed on the previous wastage sample plug 17D. Only a very fine powder deposit is observed on this surface. An EDAX analysis of this surface revealed primarily Fe (96.07 - 97.45 "/o) with lower amounts of C1 (0.34 - 1.25 "/o) than plug 17D, Table 14. The lower chloride content could explain the difference in surface morphology. The cross-section analysis, Figure 27, of plug 19A, Table 15, revealed the absence of many of the elements observed in plug 17D. Again Fe dominates the analysis (98.37 "/o) followed by Mn (1.24 "/o). The source of Mn is most likely the manganese-sulfide inclusions in the steel. The corrosion product crust removed from plug 19A was also analyzed by EDAX and XRD, Table 16. In this case, plug 19A crust was characterized by Fe (64.69 - 93.36 "/o), Si ( 3.81 - 30.34 "/o), Mn (up to 1.50 "/o), Ti (up to 2.98 "/o) and C1 (3300 to 19,300 ppm). The XRD analysis revealed a non-magnetic and magnetic phase compositions that are nearly identical to that obtained on pit:g 17D.5 The only difference found was that the lattice 34 spinel was a, = 8.396 2 0.003 for plug 19A which is parameter for the M 0 exactly the value for stoichiometric Fe 0. As was also the case of the crust 34 from plug 17D, no FeC1, FeC1, a-Fe 0 r y-Fe 02 3 "*#* Id*"*ifi*d I" *"7 2 3 23 measurable amounts. Meta 11ographic examination of wastage plug 19A, Figures 28 and 29, revealed similar results as observed on plug 17D, that is, thick corrosion product on the surface, normal microstructure and hardness values (R ~ B -

F&PMT Transmittal No. 87-178-003 Rev. 1 The leachate analysis of the sand behind plug 19A reveals similar results to that obtained behind plug 17D, Table 5, but again different results as compared to the two GPUN analyzed plugs. 5.5 Core Sample 11A - H - Above Wastage - GE This core sample was removed from above the wastage region of the drywell but still in a region in contact with the sand cushion. The thickness measured by UT was 1.170". After removal of the plug, the thickness measurement measured at the center of the plug was 1.19". Thus there was essentially no corrosion on this specimen. SEM examination of the surface of plug 11A-H (H = high, i.e., above sample 11A), Figure 30, revealed a surface with isolated islands of deposits. Higher magnification examination (1500X) revealed the presence of a non-uniform powdery scale. The EDAX analysis indicated the Pb (52.61 - 59.77 "/o) and not Fe (21.72 - 28.87) dominate the surface, Table 14. This indicates that the red lead paint (Pb 0 ) was still present on the surface. 34 This result is anticipated since this plug suffered no corrosion. It is important to note that the Pb is present because no corrosion occurred at this area and not that the red lead inhibited the corrosion. The high presence of S in both the surface analysis and cross-section analysis (Figure 31 and Table

15) may be due to the affinity of sulfate to combine with the red lead paint to produce PbSO. The sulfate may be a leachate from the Firebar-D or from 4

the marine environment. Significant amounts of chloride are also present. Since plug 11A-H had essentially no corrosion, there was no crust to analyze by EDAX or XRD. Meta 11ographic examination of plug 11A-H, Figures 32, 33 and 34, revealed the absence of severe corrosion. There was only mild attack observed at higher magnifications (125X) on the cross-section of the plug, Figure 33. Hardness measurements again revealed nominal values (R ~ B F&PMT Transmittal No. 87-178-003 Rev. 1 The leachate analysis for the sand behind low-corrosion plug 11A-H reveals some interesting differences as compared to plugs 17D and 19A. For example, despite the fact that this sand was characterized by an order of magnitude higher chloride (26 vs. 2 ppm), sulfate (40 vs. 4 ppm) and magnesium (16 vs. %3 ppm) content, this plug had essentially no corrosion. This result is consistent with the GPUN results for plugs 19C and ISA sand, where no-corrosion plug ISA was characterized by higher chloride, sulfate'and magnesium in the sand. The key difference in corrosion response lies not with the relative contamination levels in the sand, but rather the moisture content. As is shown in Table 5, the sand sample behind plug 11A-H was dry as opposed to 1.1 - 2.6% moisture for plugs 17D and 19A, respectively. The absolute difference in the contamination levels of the sand are significant on a percentage basis, but not on a corrosion basis. The key here is the absence of an electrolyte. 6.0 DISCUSSION The results presented in the previous sections on the analysis of various sand, plug, deposit and water samples indicate that a suitable environment for the corrosion of carbon steel is present in the sand cushion area. In other words, the corrosion of the drywell as exposed to this particular environment could not be considered unexpected. The question is whether the amount of corrosion is particularly high and what role did other factors such as the Firebar-D insulation, contaminants, differential aeration, red lead primer, or concrete play in the corrosion phenomenon. 6.1 General Factors Affecting the Corrosivity of the Sand Cushion There are numerous factors which would affect the corrosivity of the sand cushion relative to the carbon steel drywell. These factors include the sand porosity, electrolyte conductivity, contaminant level, moisture level, acidity / alkalinity and the presence of bacteria. a

F&PMT Transmittal No. 87-178-003 Rev. 1 The relative porosity of the sand cushion would be affected by the method of back-filling the sand into the sand cushion region during construction, the settling of the sand, the initial moisture content of the sand, whether it was subsequently wetted after installation, etc. The porosity of the sand would affect the moisture that could be retained in the sand cushion and the establishment of local areas of high aeration. The more porous the sand the more moisture would be present over an extended period of time and the more optimum the degree of aeration. Both of these factors would tend to increase the initial corrosion rate. The degree of aeration of the sand would also affect the type of corrosion products formed on the steel surface. 6 For example, studies by Romanoff have indicated that in well-aerated soils the rate of pitting / corrosion, although initially high, falls off rapidly with time because in the presence of an abundant supply of oxygen, oxidation and precipitation of iron as ferric hydroxide (Fe(OH)3] ccurs close to the metal surface, and the protective membrane formed in this manner decreases the subsequent corrosion rate. As noted on the plug specimens from the Oyster Creek drywell only shallow pitting was observed on some of the specimens. In poorly aerated regions, Romanoff noted that the initial rate of corrosion decreases slowly, if at all, with time. Under such conditions the corrosion products, remaining in the deoxidized state, tend to diffuse outward into the soil, offering little or no protection to the corroding metal. (The actual corrosion products observed on the drywell will be discussed in more detail below.) The role of conductivity of the sand cushion is more straight forward. The higher the conductivity, the greater amount of corrosion would be anticipated. The conductivity of water samples removed from various drain lines at Oyster Creek ranged from 680 to 1100 US/cm. The conductivity of pure water at similar temperatures is three orders of magnitude lower than these values. Hence, the sand / water environment was sufficiently conductive to establish a viable electrolyte for corrosion. F&PMT Transmittal No. 87-178-003 Rev. 1 As noted in Tables 2 through 6, the sand, scrapings and drain water had high levels of contaminants which would be expected to increase the corrosion rate of carbon steel. In particular, high levels of detrimental chloride and sulfate were noted in virtually all the samples analyzed. The mere fact that corrosion occurred at Oyster Creek indicates that moisture was present in the sand cushion. As discussed in Section 3.0, the sources of moisture include a known leakage of water from the fuel pool which most likely occurred through a drain line gasket, installation of moist sand during construction, water " squeezed" out of the Firebar-D slurry during pressure testing of the drywell and' condensation. The moisture content of the sand samples as measured by GE ranged from 1.1 to 12.6%. The only dry sand sample was from plug IIA-H, which did not suffer any significant corrosion. High pH is beneficial for the corrosion resistance of iron base alloys. The pH observed from sand and drain water samples ranged from 5.99 to 8.90, Table 2, 3 and 6. Most of the pH values were somewhat greater than neutral pH 7. However, average pH values alone can be misleading. As will be discussed later, the establishment of local anode and cathodic sites due to differential aeration will affect the local pH values. Deaerated anodic regions will have a lower pH while the cathodic regions will have a higher pH. Also sections of the drywell adjacent to the concrete would benefit from the high alkalinity of concrete. Corrosion induced by microbes is a widely recognized phenomenon in a number of systems such as oil wells, pipe lines and municipal sewage. Microbiological 1y influenced corrosion (MIC) has also been identified in nuclear power plants. However, the role of MIC in this particular system is being independently investigated and is therefore beyond the scope of this report. It should be noted that preliminary evidence presented during discussions of the drywell corrosion at Oyster Creek have indicated that the role of MIC, if any, is not considered to be significant. M

F&PMT Transmittal No. 87-178-003 Rev. I 6.2 Specific Influences on Oyster Creek Drywell Corrosion 6.2.1 Firebar-D Due to the known high corrosivity of Firebar-D on steel, ' one of the primary motivations in the investigation of the corrosion of the Oyster Creek drywell was the determination of the role of Firebar-D on the corrosion mechanism. As noted in Section 2.1.3.2, Firebar-D is composed of Mg0, MgC12 and water. Studies by Bilinski, et al have revealed that SMg(OH )*MgC12* 2 8H O is the predominant reaction product in mechanically-sound hardened 2 magnesium oxychloride cement. This material is extremely sensitive to exposure to water since there is an extremely narrow concentration range of magnesium and chloride ions in solution in which SMg (OH)2 HgC12 8H O is 2 stable. It is the presence of leachable MgC1 which can produce severe 2 corrosion problems. The specific corrosivity of magnesium oxychloride cements has been investigated by Kawa11er. Observations of steel exposed to direct contact with damp magnesium oxychloride reveals a distinctive dark black rust (Y-Fe 0 ), typical of corrosion which occurs in either a low oxygen or a 23 caustic environment. XRD investigations by GE specifically designed to determine the presence of Y-Fe 0 were negative. 23 An analysis of the chemical structure by Kawa11er revealed that when magnesium oxychloride is exposed to 100% humidity, leaching of surplus magnesium chloride results in the formation of magnesium hydroxide. Carbon dioxide extracted from the atmosphere combines with this material to form a surface layer of magnesium chlorocarbonate [Mg(OH)2* MgC1 2MgC0

• 6H 0].

2 3 2 This surface layer slows the. leaching process. As additional NgC1 18 2 leached, a surface crust of hydromagnesite (SMgC0

• 4CO
• SH O) is formed.

2 2 2 These insoluble carbonates and hydromagnesites help to improve the weathering stability of magnesium oxychloride materials.

F&PMT Transmittal No. 87-178-003 Rev. 1 The lack of Y-Fe 0 in the oxide on the core plug surface / crust, the 23 relatively low amount of Mg in the sand samples and the absence of corrosion at the 51' elevation level suggests that the role of Firebar-D in the degradation of the Oyster Creek drywell corrosion :'enomena is not significant. The levels of chloride and magnen. A.dentified in the various laboratory samples may be as much the result of the marine environment as the leaching of the Firebar-D. The formation of the insoluble carbonates and hydromagnesites discussed above may have reduced any potential contribution of Firebar-D to the corrosion reaction. 6.2.2 Contaminants Table 17 presents the typical constituents of seawater. A comparison of Table 17 and the results of leachate analyses, Tables 2 and 3, the drain water analysis, Table 6,.and the deposit analyses, Tables 7 and 8, reveal that many of the contaminants observed in these analyses could be from the Oyster Creek marine environment. In particular, the presence of Ba, A1, Br, B, Ca and Sr can be explained. However, the boron and strontium may be from the fuel pool as discussed in Section 3.0. The primary role of any of the ions in the corrosion of the Oyster Creek drywell would be the enhancement of the electrolyte, that is, an increase in the conductivity. A secondary role for these ions, and in particular, chloride and sulfate, would be the breakdown of any passive film established on the carbon steel surface. As seen in Figure 19, higher concentrations of chloride are observed at the drywell wall-oxide layer interface. The presence of the higher chloride at this interface may be the result of the alternate wetting and drying of the sand cushion. Regardless of the source of the contamination, that is, the marine environment and/or the Firebar-D, the presence of such known " bad actors" as chloride and sulfate will increase the corrosion rate of the drywell. n

F&PMT Transmittal No. 87-178-003 Rev. I 6.2.3 Differential Aeration In most systems which are in contact with atmospheric oxygen, geometrical situations arise where transport of oxygen through the solution by convection (natural or forced) and diffusion to one part of the metal occurs rapidly, whereas it is slow or even negligible at another. The areas characterized by high oxygen will serve as cathodes where the reduction of oxygen to hydroxyl occurs: ~ 2 + 2H O + 4e ---) 40H-0 2 Areas depleted in oxygen will become anodic with the corrosion of the carbon steel: Fe --) Fe * + 2e ~ Therefore, areas of the sand cushion adjacent to ready oxygen access suchaslowerregIcnsnearthedrainlineandupperregionsnearthe insulation gap would become cathodic while areas in the middle of the sand cushion would become anodic. UT measurements appear to verify this topographical evaluation. Also, differences in local concentrations of Nacl may result in differences in oxygen concentration as suggested by Schaschi and Marsh.10 The higher the salt concentration the lower the solubility of oxygen so that these depleted zones become the anodic zones of the differential aeration cell. 6.2.4 Role of the Red Lead Primer The outside of the drywell was painted with red lead which is lead oxide, Pb 0, or more accurately Pb Pb0, in linseed oil. Water reaching the 34 2 4 surface dissolves a certain amount of pigment and makes the water less " corrosive." In general, corrosion inhibiting pigments must be soluble enough to supply the minimum concentration of inhibiting ions necessary to reduce the corrosion rate, yet not so soluble that the are soon leached out of the paint. 9 \\ F&PMT Transmittal No. 87-178-003 Rev. 1 The inhibiting ion for red lead is probably Pb04 which can passivate steel. However, in the presence of SO or CO the passivating effects of red 4 2 lead can rapidly disappear. Sulfate was identified in many of the analyses and carbon dioxide is readily available in the atmosphere. It was noted throughout the analysis of the removed core plugs that lead was found on the surfaces of the plugs that suffered minimal or essentially no corrosion. It is strongly believed that lead was found on such samples because no corrosion occurred due to the lack of moisture (dry sand) and not due to corrosion inhibition of the red lead paint. Red lead paint alone simply does not provide long term corrosion protection. 6.2.5 Role of Adjacent Concrete Concrete provides an alkaline environment and, under moist conditions, passivates iron and steel. Regions of the sand cushion /drywell adjacent to the concrete could be benefited by this local alkaline environment. This factor can explain why the lower regions of the drywell below the 8'11.25" elevation which are in direct contact with the concrete did not suffer any measurable corrosion. Since part of the drywell is in contact with the passivating concrete and part of the drywell in contact with the moist-high conductivity sand; a macro-galvanic cell is established. This will result in the acceleration of the corrosion of the drywell in contact with the wet sand cushion. As will be discussed in Section 6.3, the presence of chloride in the sand will only amplify this effect. 6.3 Relevant Corrosion Reactions It is considered prudent to briefly examine the possible corrosion reactions which are occurring on the surface of the drywell embedded in moist sand. Iron (steel) ions will go into solution at anodic areas in an amount electrochemical 1y equivalent to the reaction at the cathodic areas. As noted o a F&PMT Transmittal No. 87-178-003 Rev. I earlier, the anodic areas of the drywell are characterized by the following basic oxidation reaction: ~ Fe --) Fe + 2e The relevant cathodic reaction in aerated solutions is the reduction of oxygen to hydroxyl ions: 2 + 3 0 + 4e --Y 40H-0 2 However, the corrosion of iron or steel is not as straight forward as illustrated above. As shown in Figure 35, numerous corrosion reactions can occur depending on the local oxygen concentration, inter alia. As will be discussed below, the presence of chloride and sulfate as observed in the Oyster Creek sand cushion, also affects the corrosion reactions. In the absence of chloride and sulfate, Figure 35, hydrous ferrous oxide (Fe0 a nH O) or ferrous hydroxide (Fe(OH)2} c 2 Poses the diffusion 2 barrier adjacent to the iron surface through which oxygen must then diffuse.11 The pH of saturated Fe(OH)2 is approximately 9.5. Pure Fe(OH)2 is typically white in color but rapidly oxidizes in air to green to greenish black. At the outer surface of the oxide film, access to dissolved oxygen allows the ferrous oxide to react to form hydrous ferric oxide or ferric hydroxides Fe (OH)2 + 1/2 H O + 1/4 02 2 ---) Fe (OH)3 Hydrous ferric oxide is orange to red brown in color and is the main constituent of " rust." It primarily exists as non-magnetic nFe 02 3 (hematite) or magnetic YFe O where hematite is more stable. Saturated Fe(OH)3 has a 23 nearly neutral pH. A magnetic hydrous ferrous ferrite, Fe 0. nH 0, often 34 2 forms a black intermediate layer between the hydrous Fe O and Fe0, Figure 35. 23 Therefore, as observed on some of the core samples from the drywell, rust films of various colors (states of oxidation) can exist simultaneously. = a 1 F&PMT Transmittal No. 87-178-003 Rev. I Motivated by the denting of carbon steel support plates in PliR steam generators, more sophisticated studies had been performed on the " rusting" of carbon steel. It is believed that this work performed by Pourbaix, et al is particularly relevant to Oyster Creek. In particular, Pourbaix, et al were looking for conditions which would produce acid chloride attack of the carbon steel. The mechanism proposed to explain this formation of acid is the hydrolysis of soluble corrosion products with formation, inter alia, of non protective magnetite which is found in large quantities where denting has occurred. If no contaminants are present (contaminants are ions other than H+, OH and Fe ), no acid hydrolysis would occur. When contaminants (such as ~ C1,Br,S0[)arepresent,noacidhydrolysiswilloccurprovidedthereare ~ ~ 4 no oxidants (such as dissolved oxygen) and no concentration by evaporation. Problems may result from the presence of contaminants when concentration by evaporation occurs even without oxidants and from the presence of contaminants when oxidants are present, even without evaporation. Since the Oyster Creek sand cushion is most likely characterized by all three factors (contaminants, oxidants and alternate wetting and drying concentration 4 mechanisms), acid formation is expected. The hydrolysis of ferrous ions in the presence of chloride or sulfate leads to acid and concentrated ferrous chloride or ferrous sulfate solutions: Fe --) Fe + + 2e ~ Fe + + H O ---) Fe0H+ + H+ 2 Fe0H+ + 2H+ + 3C1 -+ FeC1 + hcl + H 0 ~ Fe0H++4H++2S0[--yFeS + H SO HO 2 4 2 The corrosion rates of iron in these solutions are higher than in neutral or alkaline solutions. For example, instantaneous corrosion rates were measured by Pourbaix, et al, at 212*F (higher than the drywell) in 4 molar FeC12

• I"*I " i" "1 **d system without an oxidant was 1.6 mils per year (mpy). When in contact with magnetite, the instantaneous corrosion rate of iron increased to 8 mpy, and _ _ _

F&PMT Transmittal No. 87-178-003 Rev. I was well over 120 mpy when ferric contaminants were present. Magnetite, as was identified in the plug crusts at Oyster Creek, is considered by Pourbaix as such an oxidizer and not a stable form of iron in mildly oxidizing environments. The oxidizing power of magnetite is illustrated in Figure 36. The stable form of iron is a ferric oxide or a ferric hydroxide. Magnetite was considered as the normal and stable corrosion p u of iron in boiler conditions because most boilers operate satisfactorily. However, the opinion that protection is due to ferric oxide, and not to magnetite, now receives more and more support. At room temperature it has also been more and more generally accepted that magnetite is not protective in the presence of aqueous solutions. The passive films on iron in aqueous solutions at room temperatures appears to consist of Fe 0 at the metal-oxide 34 interface of of yFe 0 maghemite at the oxide-solution interface. Although 23 yFe 0 is difficult to distinguish from magnetite since maghemite is also 23 black and magnetic, and has the same XRD lines as magnetite, it was not identified in the GE analysis. However, this similarity between magnetite and maghemite could be responsible for the long accepted opinion that magnetite is the protective oxide in boiler waters. When magnetite particles are removed from the steel surface, they can be oxidized to hematite (aFe 0 ), maghemite (aFe 0 ) or goethite (aFe00H), in 23 23 the presence of water containing as little as 1 ppb dissolved oxygen.9 6.4 Corrosion Rate of Oyster Creek Drywell It is mandatory that the corrosion rate of the Oyster Creek drywell be estimated so that the present design life can be calculated. A comparison of this value with corrosion rate data available in the open literature will also be useful in determining the relative corrosion performance of the drywell. An estimation of the Oyster Creek drywell corrosion rate is straight forward since the reduced shell thickness as measured on the removed core plugs, Table 18, was approximately 0.85" and the initial thickness was 2 i u

F&PMT Transmittal No. 87-178-003 Rev. I approximately 1.15", the typical loss in thickness is 40.3". If it is assumed that the corrosion initiated with the installation of the sand 17 years ago, the average corrosion rate is approximately 20 mpy. The assumed initiation date is considered realistic since the sand was installed in at least a " moist" condition, was wetted / revetted during the expansion of the drywell which squeezed out the water from the Firebar-D slurry, and exposed to numerous condensation cycles. If it is assumed that corrosion only initiated 6 years ago when the first fuel pool leak was noted, then the estimated corrosion rate increases to approximately 50 mpy. A review of the open literature on investigations concerning the corrosion of carbon steel in air saturated environments is summarized in Table 19 and Figure 37. Data was selected for only tests with reasonable exposure periods, that is, corrosion test data based on 24 hours exposure were not used. In some cases, however, the exposure period was not provided. A more recent literature review performed for GPUN/EPRI on this subject by Pednekar of Battelle Columbus Division also reveals similar corrosion rates. It is interesting to note that the 20 mpy corrosion rate estimate for the Oyster Creek drywell falls among the data for carbon steel exposed to water ranging in quality from distilled to ambient seawater to a mixture of soils. If the 6 year-based average of 50 mpy is used, the results are compatable to Warsaw tap water or warm seawater. The results of this comparison may, at first, appear somewhat surprising. The discussion and results from Section 6.3 suggests that the sand cushion environment with high chloride and sulfate, oxygen, high conductivity, etc. would create an environment which would produce higher corrosion rates than specimens immersed in air saturated high quality water. However, there are a few factors which may be reducing the overall corrosion rate of the drywell. First, when a metal corrodes in a substance like sand, the sand tends to retain the corrosion products in place which physically stifies further corrosion. For a specimen immersed in water, the corrosion products can be transported away from the surface allowing corrosion to

k f P F&PMT Transmittal No. 87-178-003 Rev. 1 1-. continue physically uninhibited. Second, during operation the sand cushion adjacent to the drywell may dry out and thus temporarily terminate any corrosion reaction. When the sand is rewetted due to condensation and/or leaks, corrosion reinitiates. This last scenario would evolve an overall [ lower average corrosion rate, that is, a combination of high corrosion followed by long periods of dormancy. I 6 1 Pednekar notes that the corrosion rates, corrosion products, and pH changes observed in the Oyster Creek drywell corrosion are those that are observed for corrosion of carbon steels in aerated, chloride solutions. i 1 ) 6.5 Possible Corrosion Scenario of Oyster Creek Drywell Degradation i As illustrated in Figure 38, a series of factors / events most likely. affected the corrosion of the Oyster Creek drywell. Such a corrosion scenario g is listed below: 1. Backfilling of moist sand into the transition zone creates an j initial electrolyte. Sand is contaminated by open exposure to l marine environment during storage and installation. Backfilling l also affects porosity of sand which affects moisture retention j quality and creates randon air pockets. r i j 2. Expansion of drywell during pressure testing " squeezes" water out j of the Firebar-D slurry which flows down into the sand bed. This ] water contains initial high quantities of chloride and sulfate. i l 3. Corrosion of the steel drywell initiates. Red lead primer providessomeinitialprotectionduetotheformationofPbO[. l However, carbon dioxide from the air and sulfate from the sand /or Firebar-D accelerate the breakdown of the limiting inhibitive ) qualities of the red lead primer. i l I~ m

F&PMT Transmittal No. 87-178-003 Rev. 1 4. Areas with more ready access to oxygen such as the insulation gap and drain become local cathodes. 5. Areas adjacent to concrete are provided some corrosion protection due to local alkalinity. A macro galvanic cell is established between the steel adjacent to the concrete and the steel adjacent to the sand cushion. 6. Condensation cycles and leaks from fuel pool bellows gasket contribute air saturated water to maintain moist sand cushion. Additional chloride and sulfate may leach out of Firebar-D and be carried into the sand cushion. I 7. Some regions of the sand cushion see alternate wetting and drying during startup/ shutdown cycles. This results in a concentration of chloride at the metal / sand interface. 8. Sand maintains corrosion products close to metal surface and thus physically stifies corrosion rate. 9. Corrosion proceeds intermittently during " wetting" periods (condensation, leaks) or on a continuous basis. 7.0 RECOMMENDATIONS The locs of containment integrity at Oyster Creek is an obvious concern. The corrosion mechanism is fairly well defined and an estimated overall corrosion rate of %20 mpy has been established. It is now time to address this problem and identify potential mitigation steps for this phenomenon. At the specific request of CPUN, three areas of mitigation have been analyzed by GE;

1) polymer replacement / addition to the sand cushion;

2) corrosion inhibitors, and, albeit superficially, 3) cathodic protection.

I F&PMT Transmittal No. 87-178-003 Rev. I 7.1 Polymer Replacement / Addition to Sand Cushion It has been suggested that the removal of the sand cushion could be accomplished by sluicing. If the sand cushion was removed and if the subsequent void was dessicated, corrosion of the drywell would essentially stop. However, due to structural requirements on the containment, which are beyond the scope of this paper, it may be necessary to refill the sand cushion void with an alternate material which would have suitable mechanical properties. Therefore, GPUN has requested that a brief review be performed on candidate cushion materials with particular emphasis on polymers. The first concern for a polymer replacement would be identifying a suitable means of injecting the material into the void. It would be possible to spray pellets of plastic through numerous core holes cut through the containment. Although there would be some procedural difficulties, it should be possible to obtain a relatively uniform distribution of plastic pellets. Scrap material such as polycarbonate resin (e.g. Lexan) and thermoplastic resin (e.g. Noryl) are available. 6 8 Lexan and Noryl can withstand doses of approximately 8X10 and IX10 rads, respectively, before any structural damage occurs. Above these total dose levels, the materials would experience degradation by cracking. However, this cracking and eventual fracturing would probably have little effect on its structural qualities to serve as a transition cushion. Since, in this particular application, the sand and plastic would obtain their respective spring constants more from the voids in the cushion rather than any intrinsic material property, both materials should have similar spring constraints. However, it is recommended that this assumption be confirmed by a soil geologist. If it is desired to have a cushion with more support strength, then any candidate polymer should be able to be applied in a sufficiently fluid state so that it could be poured into place. This material could then completely cover the steel surface and fill the sand cushion void. Since -RR-

F&PMT Transmittal No. 87-178-003 Rev. I there will probably be no opportunity for heat curing, then the candidate material should be characterized by an ambient temperature cure. If a particular polymer is not completely wettable, it may form a crevice against the steel surface which can promote localized corrosion if any >4 electrolyte is allowed access. Therefore, assurance that any poured-in place ~ polymer adheres well to the steel must be obtained. Good adhesion will also depend on the skill with which the monomer or partially polymerized resin is installed. Epoxies would probably be the best candidates for an intrawall resin injection since any remaining sand would behave as a filler. The epoxies would also be likely to adhere to steel surfaces. The short " pot life" and the viscosity of the epoxy resins would make application troublesome; in addition epoxies are relatively costly. Coal tar epoxies would probably be the best candidates. Presumably a " Nuclear Grade" material (i.e., one especially low in halogens, sulfur, and embrittling metals) would not be needed. An epoxy spray paint could be used if the main concern is to procqct the steel surface. If the sand can be removed, possibly a coal tar epoxy paint could be sprayed or poured into the intrawall region (i.e., Napko 538 Amine Coal Tar Epoxy). Then dry sand might be re-installed into the intrawall area for mechanical support, if necessary. Napka 539 Aluminum Mastic Epoxy is an aluminum powder-filled polyamide epoxy paint that is good for application to " minimally cleaned" surfaces. It satisfactorily penetrates residual rust on steel surfaces and generally wets steel surfaces thereby assuring more thorough coverage. Napko 682 Splash Zone Barrier Costing is an epoxy amide capable of application under water, if required. l If the sand is not removed, a paint may still be used since spray paint versions of epoxies or other resins would be more fluid than the corresponding resin and would be more likely to penetrate the sand and reach the steel surface. There is no obvious way to assure that complete steel

F&PMT Transmittal No. 87-178-003 Rev. I surface coverage in the sand area is obtained. The most that might be accomplished would be assuring that excess paint is introduced to the intrawall region i.e., there is enough paint present for the sand to be saturated and coat all the entire drywell wall. For fillers that may provide support as a substitute for or an addition to the sand, materials generally used as temporary sealants for valves, flanges, and pipes might be suitable. These materials would be the elastomers (fiber-reinforced, the fiber usually being glass) used for leak sealing by Leak Repairs Inc. (Division of Team Inc., Houston, TX) or by Furmanite Inc. (Virginia Beach, VA). It would not be possible to use these materials with fiberglass if the sand was not removed. However, it may still be desirable to paint the steel surfaces first. If a polymer with good mechanical strength is desired, then materials might be used that are applied like " potting" polymers used for electrical insulation of motors (i.e., pouring of the prepolymerized material into place in a large holding container). However, the highest strength material, (20 ksi UTS) would be 20% glass-reinforced polyaryletheretherketone (i.e., PEEK). The polymer is castable at 700*F but is currently rather costly. It is available from ICI Americas Inc., (Wilmington, DE) or from a licensee (Greene, Tweed Engineered Plastics, Harleysville, PA) under the trademark "Arlon". Arlon is injection-moldable. Arlon 1260 (carbon fiber-reinforced PEEK) has a 30 kai UTS. Addition of polymer resin to existing sand precludes the use of fiber-containing resins. There is no assurance that sand as a polymer filler would add to the strength of a polymer; such a filler, in fact, usually results in a weaker product. A high hardness polyetiierurethane polymer would provide up to 7 kai UTS and a 15% carbon fiber-reinforced aromatic polyetherurethane would provide approximately 18 kai UTS. A styrene-maleic anhydride copolymer with 20% glass fiber reinforcement and proper processing may have a 10 to 14 kai UTS. The only other high strength materials approaching that of PEEK, are the fiber-reinforced epoxies. Injection grade, 20% glass fiber-reinforced ABS

F&PMT Transmittal No. 87-178-003 Rev. I have a 10 to 13 ksi UTS. Silicone / nylon 6, 6 pseudo interpenetrating networks (i.e., Petrach Systems, Bristol, PA), made by mixing the two components into a powder or granular form, may achieve 10 to 12 kai UTS. I 7.2 Corrosion Inhibitors The primary probicm with corrosion inhibitors involves obtaining a uniform distribution over the entire surface of the steel or, as with the paint discussed above, corrosion may become focused at unprotected areas. At the same time, some prohibited inhibitors (i.e., chromates) may have to be avoided. Limited life or short-term inhibitors are not useful unless the sand cushion area is made virtually airtight. Therefore, inhibitors that operate by scavenging oxygen may not be usable. However, those that promote protective oxide formation on steel surfaces appear to be the most promising. The difficulty is in identifying all of the required properties for this inhibitor in one inhibitor. Volatile inhibitors are usually of the type that scavange oxygen thereby making them limited-life inhibitors. Yet water-soluble but volatile corrosion inhibitors would be most likely to provide complete coverage of the steel surface of the sand cushion area. Molybdate could be used as a replacement for chromate to provide an inhibitor that promotes protective oxide film formation on steel; but molybdate is not available in a volatile form. Sodium molybdate is available from Noah Chemical, Farmingdale, NY. Molybdate corrosion inhibitors, but only for cooling water, have been studied by Houseman (Burnham) Ltd. of the Portals Water Treatment Group in Great Britain. Molybdates are also available from Climax Molybdenum Co., Calgon Corp., Exxon Chemical Co., Magna Corp., Nalco Chemical Co., Newage Industries Inc., and R.T. Vanderbuilt Co. A water-soluble (in case of the presence of any liquid phase moisture), volatile corrosion inhibitor such as one that might be used for packaging or in long-term storage is the only type feasible for sand cushion use to inhibit further steel wall corrosion. Cortac Corporation (St. Paul, MN; contact Boris Miksic) is outstanding in this area. They have produced a m

F&PMT Transmittal No. 87-178-003 Rev. 1 volatile, water-soluble inhibitor dicyclohexylammonium chromate (U.S. Patent 4,275,835; June 30, 1981). They may also have the molybdate version of this inhibitor or the chromate may possibly be acceptable for Oyster Creek since it is not likely to escape the sand cushion region). Just as was the case for coatings, incomplete coverage by an inhibitor can concentrate corrosion in unprotected areas. However, some corrosion inhibitors pose another problem. Nitrites, for example, should be avoided since there are certain moderate concentration ranges (depending on other environmental parameters) which would promote corrosion instead of inhibiting it. If the presently existing sand is not removed, volatile corrosion inhibitors may not work. The sand will readily absorb this type of corrosion inhibitor. In fact, this would also be true of any inhibitor applied as a solution, aqueous or otherwise. The same problem exists here as it did for considering the use of resinous fillers or paints in the presence of the existing sand: a sufficient excess of inhibitor, as a solution or as a vapor, must be used so as to assure that the inhibitor reaches the steel wall and coats it completely. Otherwise localized corrosion may occur. Since liquids will be absorbed throughout the sand more readily than vapor, an oil-soluble version of an inhibitor may be suitable for application in this case. Cortec Corporation has oil-soluble versions of its inhibitors. Using one thte is oil-soluble and volatile may be suitable since it would help ensure coating of the steel wall with the inhibitor in onc manner or another. Cortec VCI-320 would be one such product. Preservative petroleum lubricating oils could aise be suitable. Examples are Oilcoat VT and Oilcoat A (formerly Gulf products but now Chevron products), Mobil VaporTech Light Oil, SACI-100 (Witco Chemical Corp.) and Tower 640RP (Tower Chemical Corp., Palmer, PA). Similar materials may be available from other sources, but it is best to use a product containing a volatile corrosion inhibitor. (Note that these materials are bound to very flammable.) a

F&PMT Transmittal No. 87-178-003 Rev. 1 Pednekar also provides a list of organic and inorganic inhibitors for t carbon steel in aerated chloride solutions 7.3 Cathodic Protection Basically, cathodic protection is a means of reducing the corrosion of a component by making the metal a cathode by means of an impressed current or attachment to a sacrificial anode (such as magnesium, aluminum or zine). Since the cathodic protection (CP) system forces electrons into the metal creating this cathode, the basic principle of applying CP is quite simple. In general, the practical application of this corrosion control method is much more difficult. For the specific case of the Oyster Creek drywell, it may be extremely difficult. For example, CP systems are designed to protect coated structures, that is, provide protecticn against any defects (holidays) in the coating. This minimizes the re uired applied current for protection. For Oyster Creek, the drywell is presen ly uncoated and therefore significant and perhaps prohibitive currents may be required. Other concerns include what source of direct current should be use; can a suitable anode be designed and, in fact, installed around the entire sand cushion; and how can it be ascertained, on completely buried structure, whether or not the entire surface has, in fact, been made a cathode and all corrosion mitigated. Information which can answer such questions are beyond the scope of this report. 7.4 Mitigation Recommendation It appears that a multiple approach should be used for the mitigation of corrosion of the Oyster Creek drywell. Since it appears that the main j source of the corrosion problem is the wet chemically contaminated sand, the j most suitable mitigation step would be the removal of the sand and drying of -fl?p l

F&PMT Transmittal No. 87-178-003 Rev. I the cavity. This, by itself, would reduce the corrosion rate of the drywell to a vanishingly small level. If no structural support is required, a further corrosive mitigation improvement would be a back spray painting of the drywell to provide coating protection with an aluminum powder-filled polyamide epoxy paint followed by application of a volatile corrosion inhibitor to mitigate any holidays in the coating. If the sand cannot be removed, then the application of an excess quantity of an oil-soluble vapor phase inhibitor may be the best approach. If excass water is a problem, then an application of an excess of a sufficiently diluted epoxy paint such as Napko 682 Splash Zone Barrier epoxy aside may be the best choice. This paint application could then be followed by the excess application of an oil-soluble volatile corrosion inhibitor. As noted above, the use of cathodic protection as a suitable corrosion mitigation step is considered beyond the scope of this review and therefore will not be discussed.

8.0 CONCLUSION

S The results of metallurgical analysis by both GPUN and GE, data from the open literature and the abeve discussions have indicated the following conclusions concerning the corrosion cf the Oyster Creek drywell: 1. The corrosion / wastage of the drywell is due to the presence of oxygenated moist / wet sand and exacerbated by the presence of chloride and sulfate in the sand cushion. A contaminate concentrating mechanism due to alternate wetting and drying of the sand cushion may have also contributed to the corrosion phenomenon. co- -

F&PMT Transmittal No. 87-178-003 Rev. 1 2. Although Firebar-D is a known corrosive agent to steel, its role ~ in this phenomenon is'probably' secondary.. The' source of contaminants in the sand cushion may have been primarily from the local marine environment. 3. Since the wall thickness measured by UT are extremely close to~ those measured on actual removed specimens, UT ' appears to be an ' accurate non-destructive method of monitoring wall thickness. 4. The estimated corrosion rate of the Oyster Creek drywell is %20 apy. This rate reflects the average corrosion over 17 years of service regardless of the relative continuity of the corrosion reaction, i.e. there may be periods of high corrosion rate activity during wetting cycles followed by dormancy'during " dry" periods. 5. Excluding cathodic protection which is beyond the scope of this report, the optimum method of mitigation of the corrosion of the-Oyster Creek drywell appears'to'be the combination of sand removal, back spraying of a protective paint and application of a-volatile corrosion inhibitor. l 4

F&PMT Transmittal No. 87-178-003 REFERENCES 1. GPUN Safety Evaluation No. 000243-002, December 12, 1986. 2. C.R. Judd, " Leaching Tests and Chemical Analysis Results for Oyster Creek Drywell Samples," FMT Transmittal 87-212-0004, January 23, 1987. 3. G.T. Austin, Shreve's Chemical Process Industries, Fifth ed., McGraw-Hill, New York, 1984. 4. C.A. Sorrell and C.R. Armstrong, " Reactors and Equilibria in Magnesium Oxychloride Cement," Jour. of ACS, Vol. 59, No. 1-2, Jan-Feb., 1976. 5. J.E. Lewis Letter to B.M. Gordon, "X-Ray Diffraction Analyses of Corrosion Crust from Inner Surface of Oyster Creek Drywell," December 19, 1986. 6. M. Romanoff, Underground Corrosion, National Bureau of Standards, 1957. 7. Bilinski, et al, "The Formation of Magnesium Oxychloride Phases in the Systems Mg0-MgC1 -H 0 and NaOH-MgC1 -H 0," Journal of the American 2 7 2 2 Cermaic Society, VoI. 64, No. 4, April 1984. 8. S.I. Kewaller, " Update on Magnesium Oxychloride Fireproofing," Fire Technology, Vol. 13, May 1977. 9. M. Pourbaix, et al, " Chemical Aspects of Denting in Steam Generators," NP-2177, EPRI, Palo Alto, CA, December 1981. 10. E. Schaschi and G.A. Marsh, Corrosion, Vol. 16, 1960. 11. H.H. Uhlig, Corrosion and Corrosion Control, John Wiley and Sons, New York, 1971. 12. H.H. Uhlig, editor, Corrosion Handbook, John Wiley and Sons, New York, 1948. 13. W.E. Berry, et al, " Survey Report on Corrosion Behavior of Carbon Steel in Pure Water at Ambient Conditions," June 30, 1975. 14. L.L. Shreir, editor, Corrosion, Newness-Butterworths, London 1976. 15. N.E. Hamner, Corrosion Data Survey, NACE, Houston, Texas, March 1974, 16. S.P. Pedneckar, " Corrosion of Carbon Steel in Aqueous Environments at Temperatures Below Boiling - A Literature Review," Battelle Columbus Division, February 10,-1987. 17. R.S. Tunder letter to B.M. Gordon, "Information Relating to Drywell Containment Wall Corrosion at Oyster Creek," January 8, 1987. TABLE 1. DRMLLSTEEL SPECIFICATION: ASIM:A-212-61TGrB FIREB0XFINEGRAIN-NORMALI2ED CHEMISHY: 0 .23 (TYPICAL) Mn-1.06 P .010 S .023 Si .21 SHENGTH: TENSILE-75,000 PSI (If?ICAL) YIELD -50,000 PSI ELONG -35% NOTE: MATRIALWASIMPACTTESTED

TABLE 2. GPUN Sand and Firebar-D Leachate Analysis Moist Moist Moist Dry Sand Imachate Sand Imachate Sand Inachste Sand Imachate Firebar-D* Leachate Bay 11 Drain Bay 11 Drain Plig #1 (19C) Ping #2 (15A) Analytical 1 Hr. 60* C 24 Hra, Room Temp i Hr 90* C 1 Hr 60* C 1 Hr. 60* C Parametera (ug/g) (ug/g) (ug/g) (ug/g) (ug/g) Na 777 25 25 37 47 K 784 25 20 37 23 Ca 176 30 25 47 < 23 Mg 1936 30 10 10 < 23 Al < 0.3 40.5 1.5 39 2.3 Ni 4 0.3 < 0.5 0.5 <.33 < 2.3 Fe <. 0. 3 5.0 1.0 82 8.4 Cr < 0.3 4 0.5 < 0.5 4. 33 < 2.3 Mn < 0.3 0.5 < 0.5 3.7 < 2.3 Pb

0. 6 1.5

<. 0.5 <.33 c 2.3 NH (N) 3 C1 573 10.5 6.5 45 93 NO3 132 2.5 1.5 e 17 6 SQr. 2850 < 25 32 28 79 PQ N.D. N.D. N.D. N.D. N.D. F 14 N.D. N.D. N.D. N.D. TOC 1056 39 37 46.6 N.D. Organte Acida < 20 <5 <5 Total Sulfur s 50 B Conductivity 588 pH 8.46 7.43 7.58 7.02, 5.99

e Table 3. Test Det. Erpressed Relative to the Water or Leacbete - GE Moist Hoist Dry Insulation Bay 97 foras Sand Saad Core V1ms#4 Seed Area 6 Drywell Leschete Scrapings Leechste Sample #3 Core Sample Saad Sample Pipe Leak Leachate Leechste Leeshete Leechate Water Seeple WSf6152-86 WSf6153 86 WSf6154-86 WSf6260-45 WSf6281-08 WSf6262-86 WS#6221 06 130 64 4 i n A - l., Leached Material (g) _13.647 8.8 280.5 247.8 151.2 330.5 Valuse of Leechste (mL) 36 283 See $45 S30 97 3.6E-06 Co-60 (mC1/L) 1,8E-06 1.et-07 Ca-137 (oci/L) s.2E 07 7.et-07 fross Beta (mci /L) <tE-07 5.3E-07 <0E-07 40E-07 88E-07 2.4E-06 1.7E-06 tross Alpha (mC1/L) <3E-07 <3E-07 <3E-07 43E-07 <3E-07 <3E-07 <3E-07 Tritius (oC1/L) <4E-06 e4E 06 1.4E-04 44E-08 8.0E-06 S.SE-06 2.st-03 PB 8.5 8.9 7.0 7.8 7.1 8.S 8.8 Canductivity (u.ahos / cm) S40. 2300. SS. 47. 45. 80. 880. Alkalinity as CECO (as/L) Bicarbonate 170,. 110. 44. 23. 24 8. 260. Carbonate b. 16.

• 1

<1 <1 <1 21. Eydroxide <1 <1 <1 <1 si <1 c1 Total 180. 130. 44 22. 24 9.0 280. Total Crsanic Carbon (ms/L) 34 22. 3.0 2. 3.8 12. 19. Total Su1Eur es 50 (msSO /L) 80. 880. 7.8 2.4 2.2 16. 56. Chloride (as/L) 23. 240. 2. 0.8 0.S 0.0 20. Fluoride (as/L) 0.5 0.6 0.1 0.1 0.2 0.4 0.2 51trogen, Nitrate (msN/L) S. 0.1 0.4 <0.05 <0.05 0.06 6.3 pitrosen. Nitrite (agN/L) 0.66 0.13 <0.04

• 0.04
• 0.04

<0.04 <0.04 Phosphate, Crtho (asp /L) 40.1 <0.1 <0.1 =0.1 <0.1 <0.1

• 0.1 Sulfate (asSO /L) 86.

750. 7.4 1.4 1.0 14 62. Fotassium (as/L) 46. Sec. 12. 7.4 4.8 3. 88. Sodium (as/L) 36. 220. 8.3 3.S 2. 1. 110. Mesnesium (ms/L) S3. 3. 1.7 0.71 1.3 S.7 11. Iron (as/L) <0.02 =0.03 <0.02 0.14 <0.02 0.27 0.1 Calcius (es/L) S.S 7.8 4.0 1.7 3.5 1.5 6.4 Boron (as/L) 0.09 0.03 0.46 0.074 <0.03 0.24 0.92 Strontium (es/L) 0.041 0.094 0.13 0.02 0.076 <0.014 0.28 Aluminum (as/L)

• 0.02

<0.03 40.02 <0.32 0.18 <0.02 <0.1 Lead (as/L) 0.042 0.15 <0.03 =0.03 46.03 0.1 <0.3 Barium (as/L) 0.036 40.005 0.0037 <0.003

• 0.003 0.0042

<0.03 f Arsenic (as/L) 0.035 0.05 40.03 <0.03 =0.03 <0.03 <0.3

Table 4. Calculation of Cherse Salences - GE (Ien Concentratione in M1111eguivalente per Litor) Insulation Bay 97 forus Send Sand Core Flas#4 Sand Area S Drywell Leechste Screpingo Leechste Sample #3 Core Snaple Sand Sample Pipe L.sk Lesebate Leathete Leachete Lesebate Water Sample WSf6152-86 WSf6153-06 WSf6154-86 WSf6280-86 W5fs261-06 W548262-86 WSf6221-86 l}3 181 4 IIA-H 31cerbonate 3.4 2.2 0.48 0.46 0.48 0.18 S.2 0.42 Carbonate 0.16 0.32 Chloride 0.83 4.8 0.056 0.023 0.014 0.25 0.36 Fluoride 0.028 0.032 0.0053 0.0053 0.011 0.021 0.011 0.0043 0.45 0.36 0.007 0.029 Nitrate 0.047 0.C00 Nitrite Sulfate 2.0 18 0.15 0.029 0.021 0.29 1.3 Soren se borate 0.082 0.006 0.043 0.0068 0.022 0.085 Areenic as arsenate 0.0014 0.0020 Sus of,Anione (se/L) 8.7 25 1.2 0.S2 0.53 0.77 0.0 Foteesium as K+ 1.2 27 0.31 0.19 0.12 0.077 2.5 Sodium as pe+ 1.8 0.6 0.36 0.15 0.087 0.043 4.8 Mesnesius as Ms++ 4.4 0.25 0.14 0.058 0.11 0.47 0.80 0.005 0.0097 0.33 Iron se Fe++ Calcium se Ca++ 0.27 0.38 0.24 0.085 0.17 0.075 0.32

• Strontius se Sr++

0.0039 0.0021 0.003 0.000$ 0.0017 0.0064 0.018 Aluminum se A1+++ 0.001 Lead se Fb++ 0.0004 0.0018 0.0001 Barius se Ba++ 0.0014 0.0001 Sua of Cations (me/L) 7.5 27 1.1 0.49 0.51 0.68 8.9

?' i

5. Test Data Zapressed metative to the sample Welskt-GE Table Insulation Bay #7 Torus Sand Sand Core Flugf4 Sand Area 6 Screpinsa Sample #3 Core Enople Sand Sample l }-0 IS A ll4-H WSf6152-86 WSf6153-86 W846154-86 WSf6260-86 WSf6261-84 W546262-86 Moeoture Content Dry Dry 12.62 1.12 2.42 Dry LEAC5ABLE CEARACTERISf!CS:

Alkalinity as CACO, (as/s) Dicarbonate 4.S 4.9 0.083 0.04 0.086 0.026 0.21 0.71 <0.002 80.003

• 0.004
• 0.003

' Carbonate 40.03 <0.05 =0.002

• 0.003 a0.004
• 0.003 Bydroside Total 4.7 S.8 0.083 0.037 0.086 0.026 Total Organic Carbon (ag/s) d.8 0.98 0.0083 0.0052 0.014 0.034 2.1 39.

0.016 0.0063 0.0078 0.045 Total Sulfur as 50, (asSO,/s) Chloride (as/s) 0.61 11. 0.0042 0.0021 0.0014 0.026 Fluoride (as/s) 0.013 0.027 0.00021 0.00026 0.00071 0.0011 - 51trogen, Bitrate (ag5/s) 0.13' O.0044 0.00084 40.0002 40.0002 0.00017 Nitrogen. 51 trite (as5/s) 0.017 0.0058 40.0001 a0.0001 80.0002

• 0.0001 Phosphate, Ortho (asF/s)
• 0.003

<0.005 <0.002

• 0.0003
• 0.0004
• 0.0003 sulfate (asso /s) 2.S 33.

0.016 0.0036 0.0036 0.04 Fotassius (as/s) 1.2 30. 0.025 0.010 0.017 0.0086 Sodium (as/s) 0.95 9.8 0.017 0.0001 0.0071 0.0029 Magnesius (ms/s) 1.4 0.13 0.0036 0.0018 0.0046 0.016 Iron (as/s)

• 0.0006

<0.002 80.00004 0.00036 40.00007 0.00077 Calcius (as/s) 0.14 0.35 0.01 0.0044 0.012 0.0043 Boron (as/s) 0.023 0.041 0.00097 0.00019 40.00011 0.00069 Strontius (as/s) 0.0011 0 32 0.00027 0.0000S 0.00027 <0.00004 Aluminus (es/s)

• 0.0006

<0.002 =0.00004

• 0.0009 0.00057

=0.00006 Lead (as/s) 0.0011 0.0067 =0.00006 <0.00008

• 0.00011 0.00029 4

Berius (es/s) 0.002S

• 0.00022 0.00001
• 0.00001

=0.00001 0.00001 Arsenic (es/s) 0.00002 0.0022 40.00006 40.00008

• 0.00811 so.0009

A Table 6. pRYWELL BAY 11 DRAIN VATER (GPUN) BAY 11 DRAIN WATER BAY 11 DRAIN WATER 12/1/86 12/6/86 (ppm) (ppm) 96 145 Sodium 85 142 Potassium 6.4 7.5 Calcium 11 30 Magnesium 0.33 0.02 Aluminum < 0.02 < 0.01 Nickel 0.74 < 0.01 Iron < 0.02 < 0.01 Chromium 0.02 < 0.01 ~ Manganese 0.06 < 0.02 Lead 3.6 NH3 (N) j 25 32.5 Chloride 6~ 8.7 Nitrate 60 153 Sulfate ND 5 Phosphate 1 i Fluoride 51 23.3 TOC < 0.1 Organic Acid 4 Total Sulfur as 50 " 153 4 814 1100 Conductivity (uS/cm) 8.90 8.70 pH 260

• Alkalinity

~ All Alkalinity Present As HC03 i l Iu

Table 7. OYSTER CREEK DEPOSIT SAMPLES (1) (GPUN) 144036 Deposit - Scrapings from Bay No. 7 between torus and drywell (Oyster Creek No. WS-6153-86) Deposit - Scrapings from in back of No.11 expansion ' joint found 144037 in Bay No.11 between torus and drywell (O. C. No. WS-6280-86) 144038 Deposit - Scrapings from under downconer found in bay No.11 between torus and drywell (Oyster Creek No. WS-6281-86) 144036 144037 144038 Aluminum (A1 0 ) 0.09% 0.23% 0.38% 23 Boron (B 0 ) 0.35 0.35 0.32 23 Calcium (Ca0) 0.21 2.07 1.39 Chromium (Cr2 3) 0.006 0.004 0.045 0 Copper (Cuo) 0.013 0.038 0.038 Iron (Fe2 3) 78.51 69.93 65.35 O Lead (PbO) 0.55 0.51 8.72 Magnesium (Mgo) 0.27 2.12 4.78 Manganese (Mn0) 0.33 0.25 0.48 Nickel (NiO) 0.013 0.025 0.044 Potassium (K 0) 1.58 0.12 0.16 2 Sodium (Na2 ) 1.15 0.11 0.19 0 Total Yields 83.07% 75.76% 81.96% { The remainder of the deposit was verified by EDAX to be silicon which is not soluble in hydrochloric acid. The chloride detected by EDAX is due to solvent. (1) Samples taken between 12/1/86 and 12/6/86.

1 i i Table 8. EDAX Elemental Analysis of " Deposit" from Bay 7 - GE A,erage (Wt.%) Element Detected Range (Wt.%) v Na 0.00 - 2.09 0.61 l S1 0.00 - 0.66 0.15 S 0.00 - 11.65-4.15 4 C1 0.40,- 6.74 2.11 K 0.76 - 21.24 8.00 Ca 0.00 - 1.30 0.20 0.00 - 0.93 0.25 Mn Fe 41.37 - 96.82 73.49 Br 0.00 - 4.38 0.72 Pb 0.00 - 34.39 10.27 j m, r

4 4 Table 9. UT Characterization of Damage by Bay Number UT Characterization B,ay No. 1 Minor damage 3 Minor damage 5 Pitting / inclusion 7 ~ Minor damage 9 Pitting / inclusions 11 Wastage 13-Wastage 15 Pitting / inclusions 17 Wastage 19 Wastage 4 f

Table 10. Core Sample Locations Sample Bay / No. Location 1)rjxt Elevation Samples Obtained Organization 1 19C-Wastage 11'-3 5/8" Core, sand, GPUN bacteriological

• 2 15A Pit /Inc1 11'-5 1/4" Core, sand, GPUN bacteriological 3

17D Wastage 11'-3 3/4" Core, sand GE 4 19A Wastage 11'-3 3/8" Core, sand GE bacteriological 5 11A Wastage 11'-3" Core, sand GPUN-Archive 6 11A-H Minor damage. 12'-2 3/4" Core, sand GE bacteriological 7 19A Minor damage 12'-1" Core, s.ind GPUN. Archive

• Bacteriological analysis performed at York College 4

TABLE 11. ENERGY DISPERSION ANALYSES FROM THE SURFACE OF THE PLUG SAPPLES (GPUN) ELEENTAL COWOSITION

• SAMPLE MAJOR MINOR TRACE ISA Fe Pb Al,SI,Co,Mn

~ 19C Fe Cl Al,Si,Mn

• MAJOR 10 wt. %

MINOR 1 wt. % TRACE 1 et. % ELEMENTS BELOW ATOMIC NUMBER OF 11 ARE NOT DETECTABLE.

TABLE 12. EERGY DISPERSION ANALYSIS OF THE SAND SATLE FROM THE 15A SATLE LOCATION (GPUN) ELEENTAL COMPOSITION

• MAJOR Si MINOR Al,Fe TRACE Cl,K,Pb,Ti
• MAJOR

> 10 wt. % MINOR 7 1 wt. % TRACE ( l wt. % 1

ENERGY DISPERSION ANALYSIS TABLE 13. 4 OF THE FLAKE DEPOSIT FROM THE 19C PLUG SAMPLE (GPUN) ELEMENTAL COMPOSITION

• MAJOR Fe MINOR TRACE Si,Cl pH DETERMINED BY LITMUS PAPER 4
• MAJOR

> 10 wt. % MINOR 7 I wt. % TRACE 4 1 wt. % 1

Table 14. Oyster Creek Core Plug Corrosion Surfaces GE Element Core Plug Core Plug Core Plug Conc. Range 17D 19A IIA-H 0.00-0.04 A1 1.42-2.45 Si 9.83-11.31 S 0.17-0.20 C1 3.71-4.92 0.34-1.25 4.39-5.37 0.00-0.16 K 0.00-0.03 0.14-0.68 Ca Mn '1.36-1.93 1.87-2.48 0.00-0.11 Fe 92.73-94.60 96.07-97.45 21.72-28.87 52.61-59.77 ^ Pb Br 0.00-0.35 0.00-0.16 1.17-1.37 Cu Ti 0.04-0.07 0.03-0.07 Cr 0.08-0.09 0.06-0.10

Table 15. Oyster Creek Core Plug Cross-Section Analysis,GE Typical Concentration {Wt.%) Element Plug 17D* Plug 19A Plug 11A-H Al Si 0.08 0.30 S 0.23 16.40 C1 3.45 0.14 2.57 K 0.02 Ca '0.02 Mn 1.63 1.24 0.01 Fe 94.40 98.37 0.66 79.56 Pb Br 0.08 0.16 0.27 Cu Ti 0.04 0.07 0.05 Cr 0.09 0.18 0.02 l

• Average of (2) values 1

I l

Table 16. Oyster Creek Plug Crust Samples (Wt.%) - GE, Elemental Cone. Range Plug 17,D Plug 19A 0.00-1.03 A1 Si 0.00-0.63 3.81-30.34 0.07-1.72 S C1 0.02-0.38 0.33-1.93 K 0.00-0.09 0.00-0.65 Ca 0.00-0.11 0.00-0.66 i Mn 1.54-10.92 0.00-1.50 Fe 88.32-98.26 64.69-93.36 Pb Br Cu 0.00-0.23 0.00-0.52 Ti 0.00-2.98

Elements Present in Seawater' Table 17. \\ Anions, ppm Cations, ppe C1 18980 Na 10561 SO 2652 Mg 1272 4 Br 65 Ca 400 F 1.4 K 380 I 0.05 Sr 13 Inorg. C 28 SiO 0.01-7.0 2 Org. C 1.2-3.0 B 4.6 N(NO ) 0.001-0.7 H B0 26 3 3 3 N(NO ) 0.001-0.05 Si 0.02-4.0 3 N(NH ) , 0.005-0.05 A1 0.6-1.9 3 Org. N 0.03-0.2 Rb 0.2 P(PO ) 0.001-0.10 Li 0.1 4 Org. P 0-0.016 Ba 0.05 As 0.003-0.024 Fe 0.002-0.02 Zn 0.005-0.014 + Cu 0.001-0.09 j t ~ .a.,-

Table 18. Summary of Core Plug Thickness Measurements, Pre-Removal Post-Removal Average Average Comments Sample Thickness, in Thickness, in 19C 0.815 0.825 Wastage, thick corrosion product 15A (0.490 min) 1.17 Inclusions, superficial corrosion 1.17 17D 0.840 0.860 Wastage, thick corrosion product 19A 0.830 0.847 Wastage, thick corrosion product 11A 0.860 0.885 Wastage - Archive specimen 11A-H 1.17 1.19 center Above wastage, no significant corrosion 19A 1.14 1.18 center Above wastage, no significant corrosion

4 TABLE 19. CORROSION RATES OF CARBON STEEL UNDER 12-16 STATIC-AIR SATURATED CONDITIONS WATER TEMP EXPOSURE CORROSION TYPE

• C(*F)

PH PERIOD, DAYS RATE, MPY REF 23.8 UHLIG/ DISTILLED + 40(104) 4.5-8 WHITMAN NA0H/ HCL 16.6 UHLIG/ 22(72) 4.1-9.5 WHITMAN 62 2.1 BRUSH PARTIAL DEMIN 52(125) 145 5.6 BRUSH (0.1/3.6uS/cM) 12 SPELLER NA 40(104) 14 SPELLER 60(140) DISTILLED 25(77) 5.4-6.5 100 1.4 MERCER 40(104) 5.4-7.0 100 2.9 MERCER 60(140) 5.4-8.0 100 6.6 MERCER TAP 40(104) 7.2-7.7 90 53.5 KHOMITCH 50(122) 7.2-7.7 90 54.0 KH0MITCH 60(140) 7.2-7.7 90 61.7 KH0MITCH I 35 8 BREDEN CONDENSATE 25(77) i 20 N0E FEEDWATER 45(113) CONDENSATE 45(113) 7.5-11 365-1095 20 WAGNER 15 OBRECHT CONDENSATE 45(113 >6 3.5 HUDSON SEAWATER 25(77) s7 >50. NACE SEAWATER 50(122) $7 S0ll MIX 15(59) s7 1456 $18 UHLIG

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j i l l ~ i s l l 1 Plug #1 I \\ i ~ gauga 16. Plus19C outer wal1 surface microplane is 1ocatec!__

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i FIGURE.18. PLUG 19C SCALC CHARACTERIZATION MAGNIFICATION = 56X SCALE DRYWELL WALL i i t j f I i

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l l LINE REPRESENTS ENERGY DISPERSION LINE PROFILE LOCATION.

Figure.19. OYSTER CREEK PLUG 1 (19C) 55E:iM LE WE

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LOCATION, THE ARROW LOCATES A I

MANGANESE-SULFIDE INCLUSION WITHIN THE SCALE LAYER, 1 l l

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FIGURE 35. CORROSION PRODUCTS OF IRON / STEEL WITHOUT CONTAMIN FE0 NH 0 FE 0 NH O FE 023 2 34 2 OR OR FE(OH)3 HC 2 FE(0H)2 FE 0 +2H 0+H FE 3FE(OH)2 34 2 2 02 FE(OH)3 FE(OH)2+1/2 H 0+1/402 2 HYDROUS FERROUS HYDROUS FERROUS HYDROUS FERRIC 0XIDE FERRITE OXIDE ( FERROUS HYDR 0XIDE MAGNETITE FERRIC HYDR 0XIDE PH 9,5 PH 7.0 PH 7,0 ORANGE / BROWN RED WHITE (PURE) BLACK (RUST) GREEN MAGNETIC NON MAGNETIC FE 02 3 HEMATITE GREENISH / BLACK MAGNETIC vFE 023

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w. plGURE 38, POSS B , Cl-gN M 0F OYSTER 12'3" CREEK DRYWELL -gg AREA CORE SAMPLES WASTAGE FIBERGLASS 11',Y RED LEAD BOTTOM CURB 02 DEPLETED AREA ET SAMD 10'3 2 Fe -> Fe ^ + 2e-2 Fe + + 2Cl -g FeCl 2 FLOOR 2 + 2H O + 4e' -+ 6 0 2 RICH AREA 02 + + OH -+ M0H HIGHER pH 8'114 DUE TO CONCRETE e ~ CO2 02 CONCRETE CONCRETE DRAIN C t ~ -}}