A97016, Provides Response to 970107 RAI Concerning Containment Coatings at Plant

Provides Response to 970107 RAI Concerning Containment Coatings at Plant

ML20216E741
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	09/05/1997
From:	Brons J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20216E746	List: A97016, Provides Response to 970107 RAI Concerning Containment Coatings at Plant ML20216E804 ML20266A412 ML20266A416
References
ZRA97016, NUDOCS 9709110060
Download: ML20216E741 (20)

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September 5,1997 U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attention: Document Control Desk i

Subject:

Zion Nuclear Power Station, Units 1 and 2 Response to Request for Additional Information Concerning Cantainment Coatings  ;

i NRC Docket Nos. 50-295 and 50-304 i

References:

1) letter from C. Shiraki, NRC, to 1. Johnson, Commonwealth lidison, dated May 23,1997, Request for Additional Information Concerning Containment Coatings at Zion Station, Units I and 2 g 2) Ixtter from J. H. Mueller, Commonwealth lidison, to U.S.

Nuclear Regulatory Commission, dated I;ebruary 5,1997,

Submittal of Requested Documentation

3) 1.elter from A.11. Ileach, NRC, to J. H. Mueller. Commonwealth lidison, dated June 6,199i, Supplement to Confirmatory Action Ixtter Rlll-97-002 This letter provides Commonwealth lidison's (Comlid's) response to the NRC Request for Additional Information (RAl) concerning containment coatings at Zion Station

(Reference 1).

During the current Unit 2 outage, concems were identified regarding the qualification and condition of coatings in the containment building. In response to an NRC request  ;

made in a January 7,1997, teleconference, Comlid submitted, via Reference 2, J

documentation associated with the containment coating issues.1;ollowing additional teleconferences, on May I and May 15,1997, the NRC requested. in Reference 1, additional information concerning these issues. In a letter dated June 6,1997,

(Reference 3) the NRC supplememed a previous Confirmatory Action lxtter, and documented Comlid's intent to resolve containment coating concerns prior to re-start of  ;

the unit. Comlid's response to the RAI is provided in Attachment A to this letter. L I

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llased on the cotr.plexity of the coating issue, we would be pleased to meet with you at J your earliest convenience to discuss the details of this R AI response.

9'09110060 970905 pia ADOCK 05000295 -

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1 ZRA97016 Page 2 cf 2

= Attachment C to this letter lists the commitments made by ComErl in this submittal.

Ples.w direct any questions you may have concerning this submittal to this office.

Respectfully, ohn C. Brons ite Vice President Zion Nuclar Station Attachments Enclosures cc: NkC Regional Administrator- Rlil Zion Station Project Manager - NRR Senior Resident Inspector - Zion Station Office of Nuclear Facility Safety - IDNS IDNS Resident inspetor Zion NLA Engineering Manager r Master Files Reg. Assurance File IX'D Licensing

ZRA970'.6 ATTACIIMENT A RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION CONCERNING '

CONTAINMENT COATINGS AT ZION STATION i

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ATTACHMENT A RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION CONCERNING CONTAINMENT COATINGS AT ZION STATION Requested Information

1. In discussions with Comed, the staff was informed that a zone of influence with a radius of 20 feet was selected. Ilowever, the analysis in the February 5,1997, subndital gives a variety of calculated radil for the zones of innuence depending on the type of coating, some of which are greater than 20 feet.

- What is the basis for the 20 foot zone of innuence?

Comed Response The inlual 20 foot Zone of Influence (ZOI) was based on preliminary information provided by the preparers of the ZOI Calculation (Attachment A of Reference 2). At that time the majority of the ZOls calculated were 20 feet or less. The 20 foot ZOI was used -

for focusing the initial removal of unqualified coatings effort. Subsequently, the one 20 foot 201 was superseded by individual ZOls, based on component coating type. The 201 for a particular coating is a function of specific gravity and dry film thickness (DIT).

The final ZOI Calculation addresses a range of coating systems, including coating systems not found in the Zion containment. The results of the ZOI Calculation are summarized in Tables I through 3 of the ZOI Calculation.

• Table I summarizes the results of the calculation for undocumented coatings inside

Zion containment with known specific gravities.

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• Table 2 summarizes the results of the calculation for undocumented coatings for three different specific gravities with various DITs. The Table 2 information is uxd to estimate ZOls for undocumented coatings inside the Zion containment with unknown specific gravities.

• Table 3 summarizes the results of the calculation for documented coatings inside Zion containment. The information in this table does not play a role in evaluating the quantity of undocumented coating which may reach the containment sump.

Note: the terms " qualified" and " documented" in the context of this attachment are synonymous as are " unqualified" and s ndocumented."

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Requested Information

2. De February 5,1997, submittal describes a zone of influence calculation and a net positive suction head (NPSil) calculation. The zone of influence calculation determined a zone of influence for each paint type and the NPSil calculation predicted the largest amount of blockage that could be tolerated without loss of NPSil. Ilowever, there does not appear to be a connection between the two calculations.

. Describe how the calculations are used.

Comed Response The Z01 Calculation establishes the ZO! for a variety of coating systems. The net positive suction head (NPSH) calculation (Attachment 11 of Reference 2) establishes that

11.56ft' of sump screen open area blockage can be tolerated without affecting RHR pump operation. Using the System Materials Analysis Department (SMAD) Report M 00282 97 (Attachment C of Reference 2) and the information detailed below, the maximum quantity of unqualified coating postulated to reach the sump screen was estimated to be approximately I ft'. The i ft' was established based on an undocumented 4

coating (SMAD Report, Table 1. Item 195) that was not removed and has a credible pathway to the sump. This is much less than the i1.56 ft' of screen blockage pestulated to affect pump operation.

SMAD Report, Table I represents a listing of items inside the Unit 2 containment for which the status of the coating qualification was unknown. Subsequent to the initial preparation of the list, several items in SMAD Report, Table I were determined to have qualified coatings (3371 ft') This is reflected by a "Y" in the SMAD Report, Table I column labeled " Accept w/o Rem." (i.e., Acceptable Without Removal). Two items on the list (items 5 and 103, totaling 3 ft') were determined to have no coating.

Items with undocumented coating which were removed are annotated with a "Y" in the SMAD Report, Table I column labeled " REM ITM" (i.e., Removed item). Items whose coating was removed are annotated with a "Y"in the SMAD Report, Table I column labeled " REM PNT"(i.e., Removed Paint). This represents 2186 ft' of undocumented coating.

For the remaining items on the list, with the exception of item 152, dry film thickness (DIT) measurements were made and representative samples of specine gravities were determined such that the item's Z01 could be estimated. The coating associated with item 152 (Main Steam Line Supports) was determined to have a tortuous (not credible) i path to the sump and no measurements were recorded. The ZOls for the undocumented l coatings were estimated utilizing the measured DFTs, an assumed specific gravity r.ad the parametric evaluation of ZOls provided in ZOI Calculation, Table 2. The specific gravity was assumed to be 1.6. This value is rounded down from the lowest specinc gravity value found in the undocumented coatings inside the Zion containment with known specific gravities (1.61 from ZOI Calculation, Table 1).

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The undocumented coatings with a ZOI of less than 20 feet were either removed or were confirmed to be located outside their ZOI. While the ZOI calculations are based on the centerline of the sump, removal of coatings or components was based on radial measurement from the nearest edge of the sump For example,if a component was t- calculated to have a ZOI of 18.5 feet and it was physically located 18.5 feet radially from the centerline of the sump, but was located only 16 feet radially from the nearest edge of the sump screen, the coating or component would have been removed.

For the items with unqualified coatings, with a Z01 greater than 20 feet, the coating location was veriGed to be outside its respective ZOI with 3 exceptions: items 34,161, and 195. For all items except item 195, based on the experience of the personnel, the knowledge from walk downs, and a review of general arrangement and structural drawings, it was determined that the path from the component (s) to the sump was tortuous to the extent that the coating could not be transported to the sump (not a credible pathway), or that the trash curb at elevation 568' would prohibit the coating debris from reaching the sump. Item 195 is located inside its respective ZO!. The quantity of coating associated with this item is approximately I ft'. Conservatively, it is assumed that the I ft'is transported to the sump and bhicks the open area of the sump screen.

Requested Information

3. Comed took numerous actions to ensure the integrity of the Unit 2 comninment coatings.

a. Describe,in detall, the steps taken to remove failed, undocumented and unquallfled coatings from the Zion, Unit 2, containment prior to its next startup.

Comed Response identined failed coadngs were removed by scraping or grinding, as appropriate.

Undocumented coatir.gs were removed by either removing the components containing the undocumented coating or removing the coating by scraping or grinding. This is renected by a "Y"in the SMAD Report, Table I columns labeled " REM PNT" (i.e.,

Removed Faint) and " REM ITM" (i.e., Removed item).

Identification of the coating to be removed came from several sources. Zion personnel along with coating specialists performed walk downs of the Unit 2 containment speciGcally to identify h> cations of failed or undocumented coativ, In addition, system readiness walk down teams were alerted to look for degraded coating during subsequent system walk downs in the containment. When identified, failed coatings were removed.

The disposition of undocumented coatings is described in the response to Question 2.

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Requested Information

b. Estimate the amount of unquallfled paint remaining.

Comed Response It is estimated that 3100 ft' of undocumented coating remains in Unit 2 containment.

Table 1 of the SMAD Report identified 8021 ft' of equipment and component coatings for which the status of the coating qualification was initially unknown. As described in the response to Question 2,3371 ft' of coatings were subsequently determined to be quallfled; 2186 ft' of coatings were removed; and items representing 3 ft' were determined to not have a coating.

The remaining items on SMAD Report, Table I represent 2461 ft' of undocumented coatings in containment. While the walkdowns which generated SMAD Report, Table 1 -

were extensive, some areas could not effectively be examined, either from a radiological standpoint or from an inability to crect scaffolding to allow direc: m nination, llased on these uncertainties, Comed estimates that the 2461 ft' represents alg.oximately 90% of the undocumented coatings inside containment. For additional conservatism, Comed decreased the confidence level to 80% (or 3100 ft' of undocumented coatings remain inside containment).

Requested Information

c. Describe any in situ testing done on the remaining coatings.

Comed Response Adhesion tests were performed on qualified coatings inside containment, and dry film thickness and specific gravity determinations were made on unqualified coatings.

The adhesion tests were performed by a Level 3 Coatings inspector to verify that the coating systems meet ANSI N5.12. " Protective Coatings for the Nuclear ladustry,"

Paragraph 6.4 requirements. The minimum adhesion strength specified by ANSI N5.12 is 200 psi. No adhesion test of qualified coating in proper application failed the acceptance criterion. One test which failed the criterion was for a qualific<1 coating in an improper application. This coating was subsequently removed.

Thirty-three adhesion tests were performed at various elevations, on various surfaces; including concrete surfaces, carbon steel liner plate, structural steel carbon steel surfaces and component carbon steel surfaces. Test areas were chosen based on visual observations and included areas of previously distressed or visibly degraded coatings, as well as areas where coatings appeared to be in good condition. In the areas near prior coating failure (and subsequent removal), tests were performed within 3 inches,16 inches, and 36 to 48 inches of the failed edge to determine if adhesion had been degraded in the vicinity of the failure. A minimum clearance of 3 inches from the failed edge was necessary to properly mount the Elcometer adhesion tester.

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Requested Information 4.- The analysis calculates the furthest distance from which a paint particle would be transported to the sump (the radius of the zone ofinfluence). But the analysis uses a radial model and does not address the height above the water level in the zone of influence.

- To what height above the elevation 568 foot floor level were the coatings removed?

Comed Response Coatings were visually examined from elevation 568' up to and including the dome.

Unqualified coatings were found and removed on elevation 617', as renceted by a "Y"in the SMAD Report, Tabic 1, columns labeled "RiiM PNT"(i.e., Ro aoved Paint) and "RIIM ITM"(i.e., Removed item), in addition, unqualified coatings were found and subsequently removed on the 2A and 2C Steam Generator catwalks (elevation 624'),

The ZOI Calculation considers the ZOI to be a cylinder with a vertical axis at the center of the containment sump with a height extending tc the surface of the water, llowever, the removal of coatings was based on extending the cylinder to the containment dome.

As described in the response to Question 2, the removal of coatings or components was based on radial measurement from the nearest edge of the sump rather than the centerline of the sump.

Requested Information

5. Comed has reapplied the conting to sections of the Unit 2 containment.

a. Describe the extent of the recoating being done in the Zion, Unit 2, containment.

( Comed Response The Unit 2 containment recoating is near completion in the following areas:

1. An area outside the missile barrier bounded by the containment wall and the missile barrier wall at I!!cvation 568' between Azimuth Z22 and Z23, floor to ceiling. This area is approximately 25 feet long. The coating effort will include the coating of concrete walls and floors, containment liner, and structural steel.

l 2. An area inside the missile barrier at lilevation 568' centered at Azimuth Z22. This area is approximately 32 feet by 12 feet and will include the concrete Door and adjacent walls to a height of approximately 10 feet.

3. Components which had undocumented coatings removed within 20 feet measured radially distance from any edge of the sump.

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J As discussed in the May 15,1997, teleconference, this inillal scope of containment recoating is scheduled to be complete prior to Unit 2 startup. In addition, an overall plan for the long term inspection and maintenance of containment coatings is under development. This plan will be completed by second quarter,1998.

Requested Information

b. What standards were used for this recoating?

Comed Response The followint standards are being used for the recoating effort during the Z2R14 outage:

. 10 CFR 50 Part B, Quality Assurance

. ANSI N101.4, Quality Assurance for Protective Coatings Applied to Nuclear Facilities

. ANSI N101.2, Protective Coatings for Light Water Nuclear Reactor Containment Facilities

. ANSI N5.12, Protective Coatings for the Nuclear Industry

. ANSI N45.2, Quality Assurance Program Requirements (Design & Construction)

Requested Information l

c. Will any in situ testing of the newly applied coatings be performed?

Comed Response ,

Testing of the newly applied coating system consists of dry film thickness measurements and visual examination of the completed application. This testing is performed by certified coating inspection personnel. These activities are performed per work specifications and procedures to assure that the field application meets installation i requirements such that the qualification of the coating remains valid.

Requested Information

6. The' transport calculations assume a steady slow flow toward the containment sump. The coating particles are r.ssumed to drop onto the surface of the water and flow toward the sump while they are settling at the terminal velocity.

a. Ilow would the turbulence due to the break discharge, spillage, and operation of the containment sprays, occurring during and following blowdown, affect the amount of coating material reaching the sump?

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Comed Response The effects of turbulence are not considered in the ZOI Calculation. Ilased on test results, discussed in Question 8, significant margin exists telween the quantity of unqualined coating remaining inside containment and the quantity of coating required to create appreciable effects on available NPSil. Given this margin and the qualitative points discussed below, specific analyses to determine the potential effects of turbulence is considered unnecessary.

The issue of turbulence during blowdown (break discharge) can be considered in terms of general turbulence outside the jet impingement zone, and jet impingement from the break. General turbulence outside the jet impingement region during the relatively short blowdown period is not expected to generate additional qvutities of coating material that would reach the sump screens because 1) in the absence of jet impingement, failure of unqualified coating material is a time dependent process and 2) documented coatings are qualified for the 1 OCA environment such that the coating system would remain on the substrate that it coats.

Jet impingement from the break has the potential to create debris from coating, insulation and other material. Ilowever, the velocity of the now in the vicinity of the break is expected to be less than the velocity at the sump screen (0.72 ft/sec) because of the increased surface area over which the break How will travel. The decreased velocity would increase the potential for material to stay in the vicinity of the break versus being carried to the sump. Insulation debris is discussed in the response to Question 7. The response to Question 11, describes activities which would minimize the existence of other material that could be carried to the sump.

Turbulence following blowdown is considered in terms of turbulence prior to and upon recirculation now initiation. Recirculation is not expected to occur until approximately 30 minutes aftar the I.OCA while blowdown is expected to last approximately 30 seconds. Therefore, a uniform velocity field on the containment floor is not expected until slightly after recirculation flow initiation, llowever, as described in the response to Question 9, the ZOI Calculation conservatively models velocities and Dow, maximizing the Z01 and minimizing sliding velocities, which would compensate for the effects of recirculation How initiation turbulence.

Spillage flow out of the break is not expected to create signiGeant turbulence in the area of the sump. Ily the time the spillage reaches the sump area, the flow would not significantly impact the uniform veh> city field in the sump assumption (associated with the 9000 gpm recirculation Dow rate) considered in the ZOI Calculation. The velocity of l the spillage in the vicinity of the break is expected to be less than the velocity at the sump screen (0.72 ft/sec) because of increased surface area over which the spillage will How.

l This would minimize the transport of debris.

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17inally, containment spray rapidly disperses as fine particles covering the majority of containment surfaces. Spray impingement on containment surfaces is much less severe than jet impingement eftects from the initial break and therefore the effects of containment spray on the quantity of material transported to the sur !;,s screens is considered negligible.

NEl and the NRC are in conversation with respect to a planned review of PWR ECCS sump designs based on insights gathered from ECCS strainer blockage at ilWRs. How to properly account for turbulence and jet impingement is best handled in a generic matter by the industry with participation of all PWRs. These generic efforts may result in modifications to the estimates of material reaching the sump. liowever, Comed believes that any additional amount of coating that might reach the sump as the result of turbulence will not change the conclusion that adequate NPSli would be available.

Requested Information

b. In particular, would coatings located outside the zone of influence be swept into the zone of influence by these effects?

Comed Response The only coatings outside their associated ZOI that might be postulated to be swept into the ZOI are the remaining unqualified coatings, liased on the test results discussed in the response to Question 8, which demonstrate significant margin exists between the quantity of unqualified coating remaining and the quantity of coating required to appreciably affect the available NPSH, no specific analyses have been performed nor are deemed necessary to determine if coatings located outside their ZOI would be t. wept into their ZOI by turbulence.

In addition, based on the containment layout and the conservative calculation of the 201, it is not expected that sufficient quantifies of undocumented coatings outside the ZOI would be swept into the ZO! so as to jeopardize the available RHR pump NPSH.

Requested Information

c. Justify why it is not necessary to account for these effects in the analysis.

Comed Response To summarize the response provided in parts a and b of this question. Comed believes it l Is not necessary to account for the effects of turbulence in the analysis for the following reasons:

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+- Test results (refer to the response to Question 8) indicate significant margin is available between the quantity of unquallned coating remaining inside containment and the quantity of coating required to develop any appreciable loss in the available NPSH.

• Conservatisms in the NPSH and ZOI calculations would offset some of the effec's of turbulence.

• - For coatings located outside the general sump area (e.g., unqualined coatings outside their 201), the containment layout would typically provide a pathway which was tortuous to the extent that the coating would not reach the sump.

Furthermore, because NEl and the NRC are in conversation with respect to properly accounting for turbulence and jet impingement effects in analyses, modifying the analyses to account for these effects may be contrary to the final resolution of the issue between the NRC and the industry.

Requested Information d, What action was taken for those coatings that are undocumented, unquallfled or failed that may have a calculated zone of influence greater than that selected (20 feet), or have an " unbounded" zone of influence (l'able 3 of Calculation 22S B 040M 002, Revision 1, Page 26) but that may enter the zone ofinnuence through the mechanisms described above?

Comed Response As described in the response to Question 2, there is only one case where the unqualified coating with a 201 greater than 20 feet remains inside its respective ZOI and is postulated to have a credible pathway to the sump. The quantity of coating is appioximately 1 ft' The other coatings were determined to be located outside their respective ZOI. The unbounded ZOls in Table 3 of Calculation 22S-II-040M 002 (ZOI Calculation) are for qualified coating systems which do not play a role in the determination of how much undocumented coating may reach the containment sump. As described in the response to Question 3, part a, any identified failed coatings were removed. Thus the only coatings of concern would be unqualified coatings outside their respective ZOls. llecause these coatings are not postulated to reach the sump screen, no

- action has been taken for these coatings. However as discussed in the response to Parts a and b of this Question, any additional undocumented coatings entering the ZOI would not be expected to change the conclusion that the RHR pumps will have adequate NPSH.

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Requested Information

7. This analysis does not account for any insulation debris which may be transported to the sump screens as a result of a loss of coolant accident (LOCA). If any coatine,s are assumed to reach the sump (i.e., all coatings which could reach the sump are not removed prior to the next plant startup) then the combined effect of the paint and the Insulation must be taken into consideration since the pressure drop from this combination of debris can be significantly higher than that due only to failed coatings (see NUREG/CR 6224," Parametric Study of the Potential for BWR ECCS Strainer Blockage Due to LOCA Generated Debris" dated October 1995; see especially Appendix B) and the method of calculating NPSil margin in Section 2.3 of Calculation 22S H008M 092 would not be correct.

a. Verify and provide calculations that show that the zone of influence is determined so that either no coatings will reach the sump or that the effect on the pressure drop across the sump screens of any that do reach the sump is correctly calculated.

Comed Response The phenomenon described in the introduction to Question 7 is not applicable because the NPSil calculation assumes complete screen blockage of a percentage of the screen area. The method of calculating NPSH margin (Section 2.3 of Calculation 22S B 008M-092) is not affected by the type of material postulated to cacse blockage. The amount of undocumented coatings postulated to reach and block the sump screen (1 ft')is small relative to the 69% of the open screen surface that can be blocked per the NPSH calculation (11.56 ft'). as described in the response to Question 2. In addition, the tests described in the response to Question 8 indicate that failure of large quantities of coatings would not result m appreciable pressure loss across the. sump screens.

- Requested Information

b. What type ofinsulation is used in the Zion, Unit 2, containment?

Comed Response i

Insulation inside the containment missile barrier is stainless steel reflective metal (mirror) type insulation (RMI). Three hundred and thirty seven cubic feet of stainless steel l Jacketed fiberglass insulation is installed on service water piping outside the missile barrier. No other insulation type is installed inside the containment.

l Requested Information

c. Is it a type which could readily clog screens?

! 100fl4

CosnEd Response RMI has a density greater than paint, and it would therefore have a relatively small ZOI.

Based on the approach velocity determined in the ZOI Calculation and the information l

provided in NUREG/CR-3616, " Transport .nd Screen Blockage Characteristics of Reflective Metallic Imulation Matedals," RMI outside the 711D is not expected to reach i the sump screens. Furthermore, NUREG 0737, Supplement 9 for Commanche Peak, concluded that the RMI dislodged from jet impingement would not travel to the sump screen. While specific analyses have not been performed, based on the conclusions for Commanche Peak, Comed does not believe that any RMI dislodged from jet impingement would reach the sump screens so as to clog the screen or act as a filter media.

The stainless steelJacketed fiberglass insulation is not postulated to reach the sump screens since it is outside the missile barrier (i.e., will not be subjected to jet impingement from a postulated reactor coolant system pipe break), Jacketed with stainless steel, and banded to preclude failure during a I.OCA or postulated high energy line break. The stainless steel Jacketed insulation is not affected by the spray effects of containn.ent spray flow.

Requested Informnsion

8. Describe any experimental verification of the zone of innuence or NPSII analyses or other relevant experimental work and provide any available documentation.

Comed Response Flow model tests performed by Continuum Dynamics incorporated (CDI) for Zion Station demonstrate a large volume of pair t (several thousand square feet) can fail within the ZOI without an appreciable pressure loss across the sump screens. (5000 ft' of coating would result in a pressure drop of 0.25 inches of water.) Final tests were completed in July. These tests use parameters that are representative of the conditions at Zion (e.g., screen opening size and flow rates). The final test report is included as Enclosure I to this letter. Attachment B provides a brief discussion of some of the CD1 test parameters aad their correlation to the parameters utilized in the ZOI Calculation.

Requested Information

9. List and discuss any conservatisms in the Zion zone of innuence calculation and NPSit calculation.

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Comed Response 201 Calculation conservatisms:

a) The maximum dimension of the failed paint chips is assumed to be equal to the outer sump screen mesh opening,0.5 laches. A larger particle size would result in a smaller calculated ZOI, based on the greater velocity required to initiate sliding of the particle, b) The dynan:ic coefficient of friction between failed paint chips and concrete is assuined to be 0.35. This is conservative with respect to the Gibbs & 11111 report documented in NUIEG 0797, Supplement 9, which uses a value of 0.42 for the dynamic coefficient of friction. Using this conservative coefficient of friction results in lower velocities required to slide debris along the containment Door. Thus, the calculated 201 is larger. Similarly, the static coefficient of friction is conservatively assumed to be 0.40 versus the 0.60 used in the Gibbs and 11111 report documented in NUllEG-0797, Supplement 9. Using this conservative coefficient of friction results in lower velocities required for coatings to begin to slide along the containmer t floor, c) When calculating the terminal velocity of a sinking coating particle, the debrie was modeled as a circular disk parallel to the floor. The terminal velocity is minimized for horizontal alignment, since the greatest possible an'a is projected normal to the direction of motion, maximizing the drag force. %nimum terminal velocities result in longer transit times for a sinking particle. Thus, the calculated 201 is larger.

d) Worst case flow conditions were assumed to occur when calculating the ZOls.

Specliically, maximum 111111 pump flow rate of 9000 gpm during recirculation which maximizes the approach velocities is assumed. A conservatively low water temperature of 100 "F, which maximizes the water density and correspondingly minimizes the calculated vehicity to initiate particle slide and terminal particle velocities is assumed, e) ZOls were calculated at both the minimum and maximum expected flood heights and the largest of the calculated ZOI was used. (See the response Question 10). The largest ZOI calculated under these bounding conditions is presented in summary Tables I through 3 of the ZOI Calculation.

NPSil Calculation conscrullsm3 a) No credit is taken for elevated containment pressures which may exist following a I.OCA, nor is credit taken for nominal atmospheric pressure at which the containment is maintained. These pressures would increase the available NPSil, b) Maximum pipt lengths and number of fittings for the Itilit system are used. This maximizes the pressure drop which increases the required NPSil.

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c) The available NPSil is compared to the required Ni>Sil at pump run out conditions (4500 gpm per pump; 9000 gpm total). This is conservative since the required RiiR pump Dow at the time of cold leg recirculation is much less than run out conditions.

Using maximum flow also :caximizes system pressure drop, which increases the -

required NPSii.

d) The sump Dood level is taken to be i foot above the containment floor prior to initiating recirculation. Actual flood level:turing a large break LOCA is expected to be greater than 1 foot. (The maximum levtl is 5.06 feet.) The increased sump flood level would increase available NPSii, e) For purposes of determining the kinematic viscosity. !he minimum sump water temperature at the time of recirculation is assumed to ua 150 'F. This maximizes system pressure drop. Act':al sump temperature during a large break LOCA, at the time of recirculation, is expected to be greater (on the order of 225 *F).

Requested Information

.10. Explain why the zone ef influence is less at n depth of 3 feet than at 1 foot or 5.06 feet of water above the containment floor. (Calculation 22S.Il 040M 002, Section 7,

SUMMARY

AN!' CONCLUSION.)

Comed Response The ZOI calculated at a flood height of 3 feet is not always less than the calculated 201 for a flood height of I foot or the ZO! calculated for a flood height of 5.06 feet, flowever, the ZOI at a flood height of 3 feet is always less than the ZOI reported, because the reported ZOI represents the bounding value of the I foot Good height RI the 5.06 feet flood height value. As stated in the Conclusion Section of the ZOI Calculation, the bounding 201 was always used.

The ZOI for a particular coating system is chosen based on two values. The first value represents the maximum radius from the centerline of the sump for possible coating particle movement along the containment Door. The second value represents an assessment of the coating particle trajectory as it sinks to the containment Door.

The radius of potential particle movement is maximized by high horizontal water velocities. The minimum Good height of I foot maximizes this horizontal water velocity. The particle trajectory is maximized when the particle has the largest possible residence time in the water before making contact with the containment Door. This translates to the Good height of 5.06 feet value. (Refer to Figure 1 of the ZOI Calculation.)

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l Requested information D. Describe the Zion Foreign Materials Exclusion Program and how it prevents foreign material (tools, clothing, plastic shecting, etc.) from clogging or damaging the sump screens. His seems especially important to Zion, given the relatively l I

small area of the sump screen.

Comed Response The Foreign Material Exclusion (FMl!) Program applies to all personnel who perform functions that have the potential to introduce foreign material inta any plant system. The program includes specific work practicu and requirements for training of personnel, in addition to the FME program requirements. Zion Checklist E " Containment Close out for il/U or S/U" of GOP 0. " Plant Startup Documentation Requirements" requires that Operating personnel perform a containment walk down prior to Unit operation. This check list specifically requires inspection of containment areas for material which could potentially clog the containment sump, Adherence to the requirements of the FME program and GOP 0 provides assurance that the items referred to in this question are not left in the containment during operation. Checklist E of GOP 0 is provided for reference as Enclosure 2 to this letter.

Requested Information

12. Provide the following documents that are referenced in the February 5,1997, submittal, a [ Reference, sic] 5.14 of Calculation 22S.II.008M.092. ,

b. (Reference, sic] 5.5 of Calculation 22S.II.008M 092,

c. Table on page 210 of Reference 5.2.

d. Page 17 of Reference 5.17.

c. Drawing of the containment sump.

Comed Response The requested information is provided as Enclosures 3 thrr, ugh 7. It should t e noted that items 12a and 12b (l!nclosures 3 and 4) were referenced in Calculation 22S-II.008M-092 for historical purposes and are considered superseded by that calculation.

Also note that the statement at the bottom of item 12d (Enclosure 6), indicating that the document is not to be sent outside of Sargent & Lundy, may be disregarded. Sargent & '

Lundy has authorized Comed to release this page to the NRC as public information.

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ATTACIIMEN1'B CDI TEST PARAMETERS CORRELATION TO ZONE OF INFLUENCE  :

' CALCULATION PARAMETERS C= sin = Snecific Graylgy .

'Ihe coating used in the test is der.cribed in Section 3.1 of the CD1 rt port (page 7), Ameron/Amercoat 9011S, was in stock ready for une at CDI. This coating has a specific gravity of 1,4 to 1.5. As described in the Zone of Innuence (ZOI) calculation (Reference 2, Attachment A), tae postulated lowest specine gravity of coating at Zion Station is 1.6. Using material with a slightly lower specinc gravity in the flow model tests is conservative, lower '

specinc gravity results in larger ZOls due to lower velocities required to initiate sliding and increased transport time. (Refer to Reference 1, Comed response to Question 10.)

Screen Size and Orientsion

.The vertically oriented screen segment used in the test is the rame height and vertical orientation as the Zion recirculation sump screens, The screen segment was provided by Cc:aEd to CDI aci has the same size grid i penings as the Zion sump screens.

C=rlag Thickneu and Chin Fjzg

'lhe coating chip thicknesses used in the CDI tests (2-3 mits) are representative of the paint thicknesses Jaund in Zion Station (Refer to ZOI Calculation, Table 1). Additional qmmoties of coatings with different thicknesses were also used to obtain as much information as possible on the impact of large volumes of paint on the pressure drop across the sump screen (Refer to Section 3.3 of the report). The chip sites were of a random site distribution ranging between 1/8" x 1/8" to 2" x 2". The ZOI Calculation conservatively assumed the maximum dimension of the chips to be equal to the outer sump screen mesh opening, or 0.5 inches. The utilization of varying paint chip

, slies is appropriate. A varying chip sie.e would be expected in reality. The ZO! Calculation states that the asumpthm is conservative since a larger particle site would have a smaller ZOl. Ilowever, the utilization of larger chips in the relatively (compared to Containment) small test apparatus, would tend to cause more restriction of the sump screens.

Water licight '

The height of water in the test tank was chosen to be one foot to correspond to the height at which recirculation is initiated. As described in the response to Question 10, a height of one foot maximizes the horizontal water veksity, which in turn maximizer the radius of potential particle movement.

Flow Velocity The test flow veksty of 0.72 ft/sec was based on the expected Zion maximum vekrity (Refer to Z01

- Calculation, Table 1).

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ATTACllMENT C L[st of Commitments identified in ZRA97016 The following table identifies those actions committed to by Comed in this document.

Any other actions discussed is this submittal represent intended or planned actions by Comiki. They are described to the NRC for the NRC's information and are not regulatory commitments. Please notify Mr. Robert Godley, Zion Station Regulatory Assurance Manager, of any questions regarding this document or any associated regulatory. commitments.

Commitment Committed Date or Outage Comed will develop an overall plan for the long term inspection and Second Quarter maintenance of containment coatings 1998 Testing of newly applied coating systems will include dry film Ongoing .

thickness measurements and visual examination of the completed application.

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i ZRA97016 ENCLOSUREI CONTINUUM DYNAMICS, INC. TEST REPORT l

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