ML061020638

Drywell Containment, Attachment 1 to Letter Dated 04/07/2006

ML061020638
Person / Time
Site:	Oyster Creek
Issue date:	11/26/1990
From:	Devine J GPU Nuclear Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
2130-03-20289, 5000-90-1993, C320-90-264, TAC MC7624
Download: ML061020638 (151)

Text

ATTACHMENT 1 (GPU Letter to NRC dated November 26, 1990)

OPU tduear Coportllon Nuclear November 26, 1990 Ono Upper Pond Road Parsippany. Now Jersej 07054 201.316.7000 TELEX 13-482 5000-90-1993 Writers Direct Dial Number:

C320-90-264 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Gentlemen:

Subject:

Oyster Creek Nuclear Generating Station (OCNGS)

Docket No. 50-219 License No. DPR-16 Oyster Creek Drywall Containment References; (1) NRC letter dated October 3, 1990 - Summary of September 19, 1990 meeting (2) NRC letter dated October 16, 1990 - Requested clarifications on Wednesday, September 19, 1990, a meeting was held with the NRC at the NRC offices, One White Flint North, Rockville, Maryland. The purpose of this meeting was to discuss OPUN's overall plan to address the drywell corrosion issue at the Oyster Creek Nuclear Ganarkting Station. The Reference (1) lettex documents the participants, morning and afternoon presentations and summarizes the significant items discussed.

The NRC requested detailed supplemental information supporting GPUN't assessment be submitted no later than December 31, 1990.

The requested information specified by Reference (2) consists of the following four (4) items:

(1) Drywall Inspection Plan Details (original and augmented) which includes justification of Sampling Techniques and statistical methodology.

(2) Point-By-Point Code Comparison justifying ASME Section III, NE Methodology for the ASME Section VIII Drywell/Containment Vessel.

(3) Structural Design Report justifying operation to 14R refueling outage based on ASH!Section III, HE Methodology using 62 psig as drywell design pressure.

(4) OPUN Actions to prevent leakage into the drywoll gap and the effects of leakage on other structures or equipment.

GPU Nuclear Corpornion is a subsidiary of General Public Utilities Corporation

oyster creek Drywall Containment C320-90-264 Pago 3 In order to expedite NRC teview of the requested information, individual oubmittals will be provided an the documentation of each item is finalized.

Attachment I to this letter provide. the information requested by the KRC for Item (1 and includes a brief summary of the overall drywell inspection plan and the following technical documentation.

• GPU11 TDR 948, Rev. 1, "Statistical Analysts of Drywall Thickness Data.,,

OGPUI specification IS-32B227-004, Rev. 8, "Functional Requirements for Drywall contaLnment Vessel Thickness Bxamination."

• OPW Calculation C-1302-187-5300-011, Rev. 0, "Statistical Analysis of Drywall Thickness Data from 4/24/90" (Appendices 6.1 to 6.3 not attached).

• OPUf TDR 1027, Rev. 1, "Design of a UT Inspection Plan for the Drywell Con 4 :ainment Using Statistical Inference Hethods.t

• GPUA Specification IS-402950-001, Rev. 0, "Functional Requirement for Augnented Drywell Inspection."

It is GPUN's goal to provide submittal items (2) through (4) an they become available but no later than December 31, 1990. GPUH will, of course, inform the NRC of any changes to the corrosion assesnment which would compromise our technical justification for continued operation of the OCNGS.

if you have any questions on this submittal or the overall drywell corrosion program, please contact Kr. Michael Laggart, Manager, Corporate Nuclear Licensing at (201) 316-7968.

Sinceral 1L&Jk J. C. DeVtno, Jr.

L Vice President, Technical Functions JCD/RZ /plp Attachment cc's on next page RH:C30261

oyster Creek Drywell containment C320-90-264 Page 3 cc: Admsinistrator RegLon I U.S. Nuclear Regulatory commiesion 475 Allendale Road King of Prussia, PA 19406 NRC Reoident Inspector Oysl:er Creek Nuclear Generating Station Forked River, NJ 08731 Project Manager U.S. Nuclear Regulatory Commnifison MaiL Station P1-137 WasI.hington, DC 20555 RZ:C02=

.ATAC!JENT I

SUMMARY

OF GPUN OVERALL DRYW!ELL INSPECTION PLAN The CPUN drywell inspection plan is separated in two portions. The first portion is an inspection program intended to determine corrosion rates which are utilized to develop conservatlve projections.

in this portion of the program, UT inspections are performed over tiffe at the same specific locations. The inspections are performed during outages of opportunity when a drywell entry is made for reasons other than program inspections. 20 priority #1 locations are inspected not more frequently than 3 months, and 7 priority #2 locations are inspected not more frequently than 18 monthi. These inspection location. wore identified during detailed inspection of elevations 11'-3", 50'-2V, 51'-10" and 87-5" conducted in 1986, 1987 and 1990. During the 13R outage, CPUN will perform inspection of all priority #1 locations, once at the beginning of the outage and once at the end of the outage. Included in this attachment are copies of the GPUN internal reports which provide details of data collection and data reduction, as well as the most recent results for inspection up to April 1990. Also provided is Specification XS-328227-004, Rev.

8 which presents functional requirements for inspection implementation.

Thei second portion of the program will be implemented for the first time during the 13R outage and is intended to statistically confirm reuired drywell thicknesses. This portion of the program relies on UT inspection of 57, 6 x 6 inch randomly chosen locations. The reoulting inspection data will characterize the condition of the upler elevations of the drywell.

AJ part of this Attachment are copies of a cPUK Report which provides details of how the amount and the location of the 57 inspection locations were determined and specification IS-402950-001 which prsefnts functional requirements for this augmented inspection implementation in 13R.

PT'fDrY

AMACHMENT I (CQNTINUED)

TECHNICAL DOCUMENTATION

° GPUN TDR 948, Rev. 1, "Statistical Analysis of Drywell Thickness Data. I e CPUN Specification IS-328227-004, Rev. 8, "Punctional Requirements for Drywell Containment Veosel Thickness Examination."

0 GPUN Calculation C-1302-187-5300-011, Rev. 0, -Statistical Analysis of Drywall Thickness Data from 4/24/90" (Appendices 6.1 to 6.3 not attached).

• GPUN TDR 1027, Rev. 1, "Design of a UT Inspection Plan for the Drywell Containment Using Statistical Inference Methods."

• GPUN Specification IS-402950-001, Rev. 0, "Functional Requirement for Augmented Drywall Inspection."

PT/Dry

.y

'%V.

Ej 2J Nuclear EM ZDR No. 948 lN Budget Technical Data Report Activity No. 315302 Page 1 of 26 Project: Department/Section 5300 OYSTER CREEKD

_ ~Revision Date 2 -/-8 7 Docurlent

Title:

STATISTICAL ANALYSIS OF DRYWELL THICKNESS DATA Origi.nator Signature Date Approval(s) Signature Date ark i_ /x~f23<a7LZ;/

I-T.6 ,4-, T 14" j ,Approval for External Distribution Date Does this TDR include recommendation(s)? __Yes X No If yes, TFWR/TR# __,

C Distribution Abstract:

J.. D. Abramovici Statement of Problem B.. P. Barbieri G., R. Capodanno The design of the carbon steel drywell includes a sand D.. W. Covill bed which is located around the outside circumference D., G. Jerko between elevations 8' 1/4" and 12'-3". Leakage M. W. Laggart was observed from the sand bed drains during the 1980, L. C. Lanese 1983 and 1986 refueling outages indicating that water S.. D. Leshnoff had intruded into the annular region between the J. A. Martin drywell shell and the concrete shield wall.

J.. P. Moore M. A. Orski A long term monitoring program was established in 1986 S.. C. Tumminelli to take Ultrasonic Thickness (UT) measurements at rep-M.. 0. Sanford resentative locations on the drywell shell to determine D., G. Slear the corrosion rate and monitor it over time. The W. Keaten initial program included six locations in the sand bed region. The program wan expanded in 1987 to include measurements at higher elevations.

(For Additional Space Use Side 2)

This is a report of work conducted by an individual(s) for use by GPU Nuclear Corporation. Neither GPU Nuclear Corporation nor the authors of the report warrant that the report is complete or accurate. Nothing contained in the report establishes company policy or constitutes a commitment by GPU Nuclear Corporation.

• Abstract Only

AtSfnet Continuation TDR No. 94B Revision No. 1

,2 Ahsrract Continuation TDFt No. 948 ReviWn Nm 1 A cathodic protection system is being installed in selected regions of the sand bed to minimize corrosion of the drywall. The long term monitoring program was further expanded in 1988 to monitor the effectiveness of the cathodic protection system and to monitor additional sand bed regions not covered by catholic protection.

A critical part of the long term program is the sstatistical analysis of the UT measu:rements to determine the corrosion rate at aeach location. This report documnvnts the assumptions, methods, and results 4of the statistical analyses (if UT measurements taken through December 31, 1988.

Summ ry of Key Results Bay Apea Location Corrosion Rate** Mean Thickness***

1IA Sand Bed Not significant 908.6 +/-+5.0 mile liC Sand Bed Indeterminable 916.6 +/-10.4 mile 17D Sand Bed -27.6 +6.1 mpy 864.8 milo 19A Sand Bed -23.7 +4,3 mpy 837.9 +4.8 mile 19B Sand Bed -29.2 +0.5 mpy 856.5 mile 19C Sand Bed -25.9 +/-4.1 mpy 860.9 mile 9D Sand Bed Indeterminable* 1021.4 +9.7 mile 13A Sand Bed Not significant* 905.3 +10.1 mils 15D Sand Bed Possible' 1056.0 +9.1 mile 17A Sand Bed Indeterminable* 957.4 +9* 2 mile 5 51' Elev. -4.3 +0.03 mpy 750.0 +0.02 mils 9 87' Elev., Not significant 620.3 +/-1.0 mile 13 87' Elev. Not significant 635.6 +0.7 mils 15 87' Elev. Not significant 634.8 +0.7 mile 17D Trench Not significanta 981.2 +6.7 mils 17/19 Frame Cutout Indeterminable' 981.7 ;4.4 mils ID Sand Bed Indeterminable* 1114.7 +30.6 mils 3D Sand Bed Not significant* 1177.7 +5.6 mila SD Sand Bed Not significant' 1174.0 42.2 mile 7D Sand Bed Possible* 1135.1 +4.9 mils 9A Sand Bed Indeterminable* 1154.6 +/-4.8 mils 13(3C Sand Bed Not significant' 1147.4 +3.7 mile 13D Sand Bed Not significant* 962.1 +/-22.3 mile ISA Sand Bed Not significant* 1120.0 412.6 mils One data point in Bay 19A and one data point in Bay 5 Elev. 51' fell outside the 99% confidence interval and thus are statistically different from the mean thickness.

• Baited on limited data. See text for interpretation.

• • Mean corrosion rate in mile per year +/- standard error of the mean

• • • Cu:rent mean thickness in mile + standard error of the mean Page :la N 00301J (02-88)

7 14 . j E5IgNuclar lTDR 948 TITIE STATISTICAL ANALYSIS OF DRYWELL THICKNESS DATA REV

SUMMARY

OF CHANGE APP OVAL DFTE 1 Corrected outage numbers on pages 3 and 5 1-30-89 (two places). ,

Deleted redundant discussion of Bay 15D on pages 12, 19, 25 and 26. 2fI, to.s II-ll lb

TDR 948 Rev. 0 Page 2 of 26 TABLE OF CONTENTS Sections Page

1.0 INTRODUCTION

3 1.1 Background 3 1.2 Statistical Inferences 4 2.0 METHODS 5 2.1 Selection of Areas to be Monitored 5 2.2 UT Measurements 6 2.3 Data at Plug Locations 6 2.4 BaBes for Statistical Analysis of 6"x6" Grid Data 7 2.5 Analysis of Two 6"'x6'1 Grid Data Sets 9 2.6 Analysis of Single 6"x6" Grid Data Set 10 2.7 Analysis of Single 7-Point Data Set 11 2.8 Evaluation of Drywell Mean Thickness 13

3.0 REFERENCES

15 4.0 EVALUATION OF DATA THROUGH 12/31/88 15 4.1 Results for 6"x6" Grids in Sand Bed Region at original Locations 15 4.2 Results for 6"x6" Grids in Sand Bed Region at New Locations 18 4.3 Results for 6"x6" Grids at Upper Elevations 20 4.4 Results for Multiple 6"x6" Grids in Trench 22 4.5 Results for 6" strips in Sand Had Region 23 4.6 Summary of Conclusions 25

TDR 948 Rev. 1 Page 3 of 26

1.0 INTRODUCTION

1.1 Background The design of the carbon steel drywell includes a sand bed which .16 located around the outside circumference between elevations 8'-11-1/4" and 12'-3". Leakage was observed from the sand bed drains during the 1980, 1983 and 1986 refueling outages indicating that water had intruded into the annular region between the drywetl shell and the concrete shield wall.

The drywall shell was inspected in 1986 during the 11R outage to determine if corrosion was occurring. The inspection methods, results and conclusions are documented in Ref. 3.1, 3.2, and 3.3.

As a result of these inspections it was concluded that a long tern monitoring program would be established. This program includes repetitive Ultrasonic Thickness (UT) measurements in the sand bed region at a nominal elevation of 11'-3" in bays 11A, lC, 17D, 19h, 19B, and 19C.

The continued presence of water in the sand bed raised concerns of potential corrosion at higher elevations. Therefore, UT measurements were taken at the 51' and 87' elevations in November 1987 during the 11M outage. As a result of these inspections, repetitive measurements in Bay 5 at elevation 51' and in Bays 9, 13 and 15 at the 87' elevation were added to the long term monitoring program to confirm that corrosion is not occurring at these higher elevations.

A cathodic protection system is being installed in selected regions of the sand bed during the 12R outage to minimize corrosion of the drywall. The long term monitoring program was also expanded during the 12R outage to include measurements in the sand bed region of Bays iD, 3D, SD, 7D, 9K, 13A, 13C, 13D, 15A, ISD and 17A which are not covered by the cathodic protection system. It also includes measurements in the sand bed region between Bays 17 and 19 which is covered by the cathodic protection system, but does not have a reference electrode to monitor its effectiveness in this region.

Some measurements in the long term monitoring program are to be taken at each outage of opportunity, while others are taken durirg each refueling outage. The functional requirements for these inspections are documented in Ref. 3.4. The primary purpose of the UT measurements in the sand bed region is to determine the corrosion rate and monitor it over time. When the cathodic protection system is installed and operating, these data will be used to monitor its effectiveness. The purpose of the measurements at other locations is to confirm that corrosion is not occurring in those regions.

This report documents the assumptions, methods, and results of the statistical analyses used to evaluate the corrosion rate in each of these regions. The complete analyses are documented in Ref. 3.7.

TOR 948 Rev. 0 Page 4 of 26 1.2 Statistical Inferences 1.2.1 Statistical Hypotheses The objective of these statistical analyses is to make statistical decisions or Inferences about populations on the basiso of sample information. In attempting to reach these decisions, it is useful to make assumptions or guesses about the populations involved. Such assumptions, which may or may not be true, are called statistical hypotheses and in general are statements about the probability distributions of the populations.

In many instances we formulate a statistical hypothesis for the sole purpose of rejecting or nullifying it. For example, in performing a t-test to test the difference between the means of two samples we first hypothesize that there is no difference between the two means. This is referred to as a null hypothesis. Any hypothesis which differs from the null hypothesis is referred to as an alternative hypothesis, eg., the means are not equal, one mean is greater than the other, etc.

1.2.2 Teats of Hypotheses and Significance if on the supposition that a particular null hypothesis is true we find that results observed in a random sample differ markedly from those expected under the hypothesis on the basis of pure chance, we would say that the observed differences are significant and we would be inclined to reject the hypothesis (or at least not accept it on the basis of the evidence obtained). Procedures which enable ug to decide whether to reject or not reject hypotheses are called tests of hypotheses.

1.2.3 Type I and Type II Errors If we reject a hypothesis when it should not have been rejected, we say that a Type I error has been made. If, on the other hand, we fail to reject a hypothesis when it should have been rejected, we say a Type II error has beer.

made. In either cane a wrong decision or error in Judgement has occurred.

1.2.4 Level of Significance In testing a given hypothesis, the maximum probability witch which we would be willing to risk a Type I error is called.

the level of significance of the test. This probability Js usually denoted by the Greek letter alpha. In practice a level of significance of 0.05 (5) or 0.01 (1%) is customary. If 0.05 has been selected, we say that the hypothesis is rejected (or not rejected) at a level of significance of 0.05.

TDR 948 r; Rev. 1 Page 5 of 26 2.0 METHODS 2.1 Selection of Areas to be Monitored A program was initiated during the 11R outage to characterize the corrosion and to determine its extent. The details of this inspection program are documented in Ref. 3.3. The greatest corrosion was found via UT measurements in the sand bed region at the lowest accessible locations. Where thinning was detected, additional measurements were made in a cross pattern at the thinnest section to determine the extent in the vertical and horizontal directions. Having found the thinnest locations, measurements were made over a 6-6" grid.

To determine the vertical profile of the thinning, a trench was excavated into the floor in Bay 17 and Bay 5. Bay 17 was selected since the extent of thinning at the floor level was greatest in that area. It was determined that the thinning below the top of the curb was no more severe than above the curb, and became less severe at the lower portions of the sand cushion. Bay 5 was excavated to determine if the thinning line was lower than the floor level in areas where no thinning was detected above the floor. There were no significant indications of thinning in Bay !;.

It was on the basis of these findings that the 6"x6" grids in Bays 11A, 11C, 17D, 19A, 19B and 19C were selected as representative locations for longer term monitoring. The initial measurements a:

these locations were taken in December 1986 without a template or markings to identify the location of each measurement.

Subsequently, the location of the 6"x6" grids were permanently marked on the drywall shell and a template is used in conjunction with these markings to locate the UT probe for successive measuremehts. Analyses have shown that including the non-template data in the data base creates a significant variability in the thickness data. Therefore, to minimize the effects of probe location, only those data sets taken with the template are included in the analyses.

The presence of water in the sand bed also raised concern of potential corrosion at higher elevations. Therefore, UT measurements were taken at the 51' and 87' elevations in 1987 during the 1iM outage. The measurements were taken in a band on 6-inch centers at all accessible regions at these elevations.

Where these measurements indicated potential corrosion, the measurements spacing was reduced to 1-inch on centers. If these additional readings indicated potential corrosion, measurements were taken on a 6"x6" grid using the template. It was on the basis of these inspections that the 6"x6" grids in Bay S at elevation 51' and in bays 9, 13 and 15 at the 87' elevation were selected as representative locations for long term monitoring.

TDR 948 Rev. 0 Page 6 of 26 The long term monitoring program was expanded as follows during the 12R outage (1) Measurements on 6"x6" grids in the sand bed region of Bays SD, 13A, 15D and 17A. The basis for selecting these locations is that they were originally considered for cathodic protection but are not included in the system being installed.

(2) Measurements on 1-inch centers along a 6-inch horizontal atzip in the sand bed region of Bays ID, 3D, 5D, 7D, 9A, 13C, and 15A. These locations were selected on the basis that they ere representative of regions which have experienced nominal corrosion and are not within the scope of the cathodic protection system.

(3) A 6"x6" grid in the curb cutout between Bays 17 and 19. ThQ purpose of these measurements is to monitor corrosion in this region which is covered by the cathodic protection system but does not have a reference electrode to monitor its performance.

2.2 UT Measurements The UT measurements within the scope of the long term monitoring program are performed in accordance with Ref. 3.4. This involves taking UT measurements using a template with 49 holes laid out on a 6"x6" grid with 1" between centers on both axes. The center row is used in those bays where only 7 measurements are made along a 6-inch horizontal strip.

The first set of measurements were made in December 1986 without the use of a template. Ref. 3.4 specifies that for all subsequert readings, 'QA shall verify that locations of UT measurements performed are within +1/4" of the location of the 19B6 UT measurements. It also specifies that all subsequent measurements are to be within +1/8" of the designated locations.

2.3 Data at Plug Locations Seven core samples, each approximately two inches in diameter were removed from the drywell vessel shell. These samples were evaluated in Ref. 3.2. Five of these samples were removed within the 6"x6" grids for Bays 11A, 17D, 19A, 19C and Bay 5 at elevation 51'. These locations were repaired by welding a plug in each hole, Since these plugs are not representative of the drywell shell, UT measurements at these locations on the 6"x6" grid must be dropped from each data set.

TMR 948 Rev. 0 Page 7 of 26 The following specific grid points have been deleted:

Bay Are Points 11A 23, 24, 30, 31 17D 15, 16, 22, 23 19A 24, 25, 31, 32 19C 20, 26, 27, 33, 5 20, 26, 27, 28, 33, 34, 35 2.4 Bases for Statistical Analysis of 6VxW" Grid Data 2.4.1 Assumptions The statistical evaluation of the UT measurement data to determine the corrosion rate at each location is based or; the following assumptions:

(1) Characterization of the scattering of data over each 6"x6" grid is such that the thickness measurements are normally distributed.

(2) Once the distribution of data for each 6"x6" grid is found to be normal, then the mean value of the thickness is the appropriate representation of the average condition.

(3) A decrease in the mean value of the thickness with time is representative of the corrosion occurring within the 6"x6" grid.

(4) If corrosion has ceased, the mean value of the thickness will not vary with time except for random errors in the UT measurements.

(5) If corrosion is continuing at a constant rate, the mean thickness will decrease linearly with time. In this case, linear regression analysis can be used to fit the mean thickness values for a given zone to ii straight line as a function of time. The corrosion rate is equal to the slope of the line.

The validity of these assumptions is assured by:

(a) Using more than 30.data points per 6"x6" grid (b) Testing the data for normality at each 6"x6" grid location.

(c) Testing the regression equation as an appropriate model to describe the corrosion rate.

TDR 948 Rev. 0 Page 8 of 26 These tests are discussed in the following section. In cases where one or more of these assumptions proves to be invalid, non-parametric analytical techniques can be used to evaluate the data.

2.4.2 Statistical APProach The following steps are performed to test and evaluate the UT measurement data for those locations where 6"x6" grid data has been taken at least three timani (1) Edit each 49 point data set by setting all invalid points to zero. Invalid points are those which are declared invalid by the UT operator or are at a plug location. (The computer programs used in the following steps ignore all zero thickness data points.)

(2). Perform a chi-squared goodness of fit test of each 49 point data set to ensure that the assumption of normality is valid at the 9$ and 99% confidence levels.

(3) Calculate the mean thickness of each 49 point data set.

(4) Using the mean thickness values for each 6"x6' grid, perform linear regression analysis over time at each location.

(a) Perform F-test for significance of regression at the 95% confidence level. The result of this test indicates whether or not the regression model is more appropriate than the mean model. In other words, it tests to see if the variation of the regression model is statistically significant over that of a mean model.

(b) Calculate the co-efficient of determination (Ru) to assess how well the regression model explains the percentage of total error and thus how useful the regression line will be as a predictor.

(c) Determine if the residual values for the regression equations are normally distributed.

(d) If the regression model is found to be appropriate, calculate the y-intercept, the slope and their respective standard errors.

The y-intercept represents the fitted mean thickness at time zero, the slope represents

TDR 948 Rev. 0 Page 9 of 26 the corrosion rate, and the standard errors represent the uncertainty or random error of these two parameters.

(5) Use a z score of 2.58 and the standard deviation to ostablish a 99% confidence interval about the mean thickness values for each 6"1x6" grid location to determine whether low thickness measurements or "outliers" are statistically significant. If the data points are greater than the 99% lower confidence limit, then the difference between the value and the mean is deemed to be due to expected random error.

However, if the data point is less than the lower 9S%

confidence limit, this implies that the difference is statistically significant and is probably not due tc chance.

2.5 Analysis of Two 6"x6" Grid Data Sets Regression analysis Is inappropriate when data is available at only two points in time. However, the t-Test can be used to determine if the means of the two data sets are statistically different.

2.5.1 Assumptions This analysis is based upon the following assumptions:

(1) The data in each data set is normally distributed.

(2) The variances of the two data sets are equal.

2.5.2 Statistical Approach The evaluation takes place in three steps:

(1) Perform a chi-squared test of each data set to ensure that the assumption of normality is valid at the 95S, and 99% confidence levels.

(2) Perform an F-test of the two data sets being compared to ensure that the assumption of equal variances is valid at the 95% and 99% confidence levels.

(3) Perform a two-tailed t-Test for two independent samples to determine if the means of the two data sets are statistically different at the 0.05 and 0.01 levels of significance.

A conclusion that the means are not statistically different is interpreted to mean that significant corrosion did not occur over the time period represented by the data.

However, if equality of the means is rejected, this implies that the difference is statistically significant and could be due to corrosion.

TDR 948 Rev. 0 Page 10 of 26 2.6 knalysis of Single 6"x6" Grid Data Set In those cases where a 6"x6" data set is taken at a given location for the first time during the current outage, the only other data to which they can be compared are the UT survey measurements taken in 1986 to identify the thinnest regions of the drywall shell in the sand bed region. For the most part, these are single point measurements which were taken in the vicinity of the 49-point date.

set, but not at the exact location. Therefore, rigorous statistical analysis of these single data sets is impossible.

However, by making certain assumptions, they can be compared with the previous data points. If more extensive data is available at the location of the 49-point data set, the t-test can be used to compare the means of the two data sets as described in paragraph 2.5.

When additional measurements are made at these exact locations during future outages, more rigorous statistical analyses can be employed.

2.6.1 Assumptions The comparison of a single 49-point data sets with previous data from the same vicinity is based on the following assumptions; (1) Characterization of the scattering of data over the 6'"x6'" grid is such that the thickness measurements are normally distributed.

(2) Once the distribution of data for the 6"x6" grid is found to be normal, then the mean value of the thickness is the appropriate representation of the average condition.

(3) The prior data is representative of the condition a-this location in 1986.

2.6.2 Statistical Approach The evaluation takes place in four steps:

(1) Perform a chi-squared test of each data set to ensure that the assumption of normality is valid at the 95%

and 99% confidence levels.

(2) Calculate the mean and the standard error of the mean of the 49-point data set.

(3) Determine the two-tailed t value from a t distribution table at levels of significance of 0.05 and 0.01 for n-i degrees of freedom.

-TDR 948 Rev. 0 Page 11 of 26 (4) Use the t value and the standard error of the mean to calculate the 95% and 99% confidence intervals about.

the mean of the 49-point data set.

(5) Compare the prior data point(s) with these confidence intervals about the mean of the 49-point data sets.

If the prior data falls within the 95% confidence intervals, it provides some assurance that significant corrosion has not occurred in this region in the period of time covered by the data. If it falls within the 99' confidence limits but not within the 95% confidence limits;,

this implication is not as strong. In either case, the corrosion rate will be interpreted to be "Not Significant".

If the prior data falls above the upper 99% confidence limit, it could mean either of two things: (1) significant corrosion has occurred over the time period covered by the data, or (2) the prior data point was not representative of the condition of the location of the 49-point data set in 1986. There is no way to differentiate between the two.

In this case, the corrosion rate will be interpreted to bi "mPossible".-

If the prior data falls below the lower 99% confidence limit, it means that It is not representative of the condition at this location in 1986. In this case, the corrosion rate will be interpreted to be "Indeterminable"..

2.7 Analysis of Single 7-Point Data Set In those cases where a 7-point data set is taken at a given location Tor the first time during the current outage, the only other data to which they can be compared are the UT survey measurements taken in 1986 to identify the thinnest regions of thi drywell shell in the sand bed region. For the most part, these are single point measurements which were taken in the vicinity of the 7-point data sets, but not at the exact locations. However, by making certain assumptions, they can be compared with the previous data points. If more extensive data is available at the location of the 7-point data set, the t-test can be used to compare the means of the two data sets as described in paragraph 2.5.

When additional measurements are made at these exact locations during future outages, more rigorous statistical analyses can be employed.

2.7.1 Assumptions The comparison of a single 7-point data sets with previous}

data from the same vicinity is based on the following assumptions; (1) The corrosion in the region of each 7-point data set is normally distributed.

TDR 948 Rev. 0 Page 12 of 26 (2) The prior data is representative of the condition at this location in 1986.

The validity of these assumptions cannot be verified.

2.7.2. Statistical Approach The evaluation takes place in four steps:

(1) Calculate the mean and the standard error of the mean of the 7-point data set.

(2) Determine the two-tailed t value using the t distribution tables at levels of significance of 0.05 and 0.01 for n-l degrees of freedom.

(3) Use the t value and the standard error of the mean to calculate the 95% and 99% confidence intervals about.

the moan of the 7-point data set.

(4) Compare the prior data point(s) with these confidence intervals about the mean of the 7-point data sets.

If the prior data falls within the 95% confidence intervals, it provides some assurance that significant corrosion has not occurred in this region in the period of time covered by the data. If it falls within the 99%

confidence limits but not within the 95% confidence limits, this implication is not as strong. In either case, the corrosion rate will be interpreted to be "Not Significant".

If the prior data falls above the upper 99% confidence interval, it could mean either of two things: (1) significant corrosion has occurred over the time period covered by the data, or (2) the prior data point was not representative of the condition of the location of the 7-point data set in 1986. There is no way to differentiate between the two. In this case, the corrosion rate will be interpreted to be "Possible".

If the prior data falls below the lower 99% confidence limit, it means that it is not representative of the condition at this location in 1986. In this case, the corrosion rate will be interpreted to be "Indeterminable"..

2.8 Evaluation of Drywell Mean Thickness This section defines the methods used to evaluate the drywall thickness at each location within the scope of the long term monitoring program.

2.8.1 Evaluation of Mean Thickness Using Regression Analysis The following procedure is used to evaluate the drywell mean thickness at those locations where regression analyB;Ls has been deemed to be more appropriate than the mean model.

TDR 948 Rev. 0 Page 13 of 26 (1) The best estimate of the mean thickness at these locations is the point on the regression line corresponding to the time when the most recent set of measurements was taken. In the SAS Regression Analysis output (Ref. 3.7), this is the last value in the column labeled "PREDICT VALUE".

(2) The best estimate of the standard error of the mean thickness is the standard error of the predicted value used above. In the SA Regression Analysis output, this is the last value in the column labeledi "STD ERR PREDICT".

(3) The two-sided 95% confidence interval about the mean thickness is equal to the mean thickness plus or minus t times the estimated standard error of the mean. This is the interval for which we have 95%

confidence that the true mean thickness will fall within. The value of t is obtained from a t distribution table for equal tails at n-2 degrees of freedom and 0.05 level of significance, where n is the number of sets of measurements used in the regression analysis. The degrees of freedom is equal to n-2 because two parameters (the y-intercept and the slope) are calculated in the regression analysis; with n mean thicknesses as input.

(4) The one-sided 95% lower limit of the mean thickness is equal to the estimated mean thickness minus t times the estimated standard error of the mean. This is the mean thickness for which we have 95%

confidence that the true mean thickness does not fal.

below. In this case, the value of t is obtained from a t distribution table for one tail at n-2 degrees of freedom and 0.05 level of significance.

2.8.2 Evaluation of Mean Thickness Using Mean Model The following procedure is used to evaluate the drywall mean thickness at those locations where the mean model is deemed to be more appropriate than the linear regression model. This method is consistent with that used to evaluate the mean thickness using the regression model.

(1) Calculate the mean of each set of UT thickness measurements.

(2) Sum the means of the sets and divide by the number Df sets to calculate the grand mean. This is the best estimate of the mean thickness. In the SAS Regression Analysis output (Ref. 3.7), this is the value labelled "DEP MEAN".

TDR 948 Rev. 0 Page 14 of 26 (3) Using the means of the sets from (1) as input, calculate the standard error. This is the best estimate of the standard error of the mean thickness.

(4) The two-sided 95% confidence interval about the mea:

thickness is equal to the mean thickness plus or minus t times the estimated standard error of the mean. This is the interval for which we have 95%

confidence that the true mean thickness will fall within. The value of t is obtained from a t distribution table for equal tails at n-1 degrees oE freedom and 0.05 level of significance.

(5) The one-sided 95% lower limit of the mean thickness is equal to the estimated mean thickness minus t times the estimated standard error of the mean. This is the mean thickness for which we have 95%

confidence that the true mean thickness does not fall below. In this case, the value of t is obtained from a t distribution table for one tail at n-1 degrees of freedom and 0.05 level of significance.

2.8.3 Evaluation of Mean Thickness Using Single Data Set The following procedure is used to evaluate the drywell thickness at those locations where only one set of measurements is available.

(1) Calculate the mean of the set of UT thickness measurements. This is the best estimate of the mean thickness.

(2) Calculate the standard error of the mean for the set of UT measurements. This is the best estimate of the standard error of the mean thickness.

Confidence intervals about the mean thickness cannot be calculated with only one data set available.

3.0 REFERENCES

3.1 GPUN Safety Evaluation SE-000243-002, Rev. 0, "'Drywell Steel Shell Plate Thickness Reduction at the Base Sand Cushion Entrenchment Region" 3.2 GPUN TDR 854, Rev. 0, "Drywell Corrosion Assessment" 3.3 GPUN TDR 851, Rev. 0, "Assessment of Oyster Creek Drywell Shell" 3.4 GPUN Installation Specification IS-328227-004, Rev. 3, "Functional Requirements for Drywell Containment Vessel Thickness Examination"

TDR 948 Rev. 0 Page 15 of 26 3.5 Applied Regression Analysis, 2nd Edition, N.R. Draper & H. Smith, John Wiley & Sons, 1981 3.6 Statistical Concepts and Methods G.K. Bhattacharyya & R.A. Johnson, John Wiley & sons, 1977 3.7 GPUN Calculation C-1302-187-5300-005, Statistical Analysis of Drywell Thickness Data Thru 12/31/80.

4.0 EVALUATION OF DATA THROUGH 12/31/88 4.1 Results for 6 11x6" Grids in Sand Bed Region at Original Locations 4.1.1 Bay 1hA: 5/1187 to 10/8/88 Six 49-point data sets were available for this bay covering the time period from May 1, 1987 to October 8, 1988. Since a plug lies within this region, four of the points were voided in each data set. The data were analyzed as described in paragraphs 2.4 and 2.8.2.

(1) The data are normally distributed.

(2) The mean model is more appropriate than the regression model.

(3) The current mean thickness + standard error is 908.6

+5.0 mile.

(4) There was no significant corrosion from May 1, 1987 to October 8, 1988.

4.1.2 Day lC: 5/1/87 to 10/8/88 Five 49-point data sets were available for this bay covering the time period from May 1, 1987 to October 8, 1988. These data were analyzed as described in paragraphs 2.4 and 2.8.2. The initial analysis of this data indicated that the data are not normally distributed.

The lack of normality was tentatively attributed to minimal corrosion in the upper half of the 6"x6" grid with more extensive corrosion in the lower half of the grid. To trtst this hypothesis, each data set was divided into two subsets, with one containing the top three rows and the other containing the bottom four rows.

The top subset was normally distributed but the bottom subset was not. For both subsets, the mean model is more appropriate than the regression model.

Since there is an observable decrease in the mean thickness with time, there appears to be some on-going corrosion at.

this location. Further analysis is required.

TDR 948 Rev. 0 Page 16 of 26 The current mean thickness + standard error is 916.6 +10.4 mile for the lower subset and 10S7.6 416.9 mile for the upper subset.

4.1.3 Bay 17D: 2/17/87 to 10/8/88 Six 49-point data sets were available for this bay covering the time period from February 17, 1987 to October 8, 1988.

Since a plug lies within this region, four of the points were voided in each data set. The data were analyzed as described in paragraphs 2.4 and 2.s.i.

(1) The data are normally distributed.

(2) The regression model is appropriate.

(3) The regression model explains 84% of the total variation about the moan.

(4) The residuals are normally distributed.

(5) The current mean thickness + standard error is 864.8

+6.8 mils.

(6) The corrosion rate + standard error is -27.6 +6.1 mile per year.

(7) The measurements below 800 mile ware tested and determined not to be statistically different from the3 mean thickness.

4.1.4 Bay 19A: 2/17/87 to 10/8/88 Six 49-point data sets were available for this bay covering the time period from February 17, 1987 to October 8, 1988.

Since a plug lies within this region, four of the points were voided in each data set. The data were analyzed as described in paragraphs 2.4 and 2.8.1.

(1) The data are nearly normally distributed.

(2) The regression model is appropriate (3) The regression model explains 88% of the total variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness + standard error is 837.9

+4.8 mils.

(6) The corrosion rate + standard error iB -23.7 +4.3 Wpy.

TDR 948 Rev. 0 Page 17 of 26 (7) One data point that was below 800 mils at two different times Was tested and determined to be statistically different from the mean thickness. The probability of this occurring is less than 1% at each specific time.

4.1.5 Bay 19B: 5/1/87 to 10/8/88 Five 49-point data sets were available for this bay covering the time period from May 1, 1987 to October 8, 1988. The data were analyzed as described in paragraphs 2.4 and 2.8.1.

(1) The data are normally distributed.

(2) The regression model is appropriate.

(3) The regression model explains 99% of the total variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness + standard error Is 856.!

+0.5 mile.

(6) The corrosion rate + standard error is -29.2 +0.5 mpY.

(7) The measurements below 800 mils were tested and determined not to be statistically different from tILe mean thickness.

4.1.6 BNY 19C: 5/1/87 to 10/8/88 Five 49-point data sets were available for this bay covering the time period from May 1, 1987 to October 8, 1988. Since a plug lies within this region, four of the points were voided in each data set. The data were analyzed as described in paragraphs 2.4 and 2.8.1.

(1) The data are normally distributed.

(2) The regression model is appropriate.

(3) The regression model explains 91% of the total variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness + standard error is 860.S 44.0 mile.

(6) The corrosion rate + standard error is -25.9 +4.1 mpy.

TDR 948 Rev. 0 Page 18 of 26 (7) The measurements below 800 mile were tested and determined not to be statistically different from the mean thickness.

4.2 Results for 6"x6" Grids in Sand Bed Region at New Locations 4.2.1 Bay 9D: 11/25/86 to 12/19/88 The 6"x6" grid data was taken in December 1988 during the 12R outage. This bay was considered for cathodic protection, but is not within the scope of the cathodic protection system being installed. The primary purpose oal this data is to establish a base line to monitor corrosion in the future. However, previous measurements were taken in November 1986 in a 10-point 6"x61' cruciform pattern.

Measurements were also taken in a 6"1x6" grid in December 1986. The new data were compared with both of the previous data sets. These comparisons were made using the chi-squared test, F-test and two-tailed t-test as describod in paragraph 2.5. The mean thickness was determined as described in paragraph 2.8.3.

(1) The data are normally distributed.

(2) The variances are equal in both ccmparisons.

(3) It is appropriate to use the two-tailed t-test in both comparisons.

(4) The difference between the means of the 1988 49-point data set and the 1986 10-point data set is not significant. However, there is a significant difference between the means of the 1988 49-point data set and the 1986 49-point data set. Therefore.,

significance of the corrosion rate is classified as "Indeterminable".

(5) The current mean thickness + standard error is 1021.4

+9.7 mile.

4.2.2 Bay 13A; 11/25/86 to 12/17/88 The 6"x6t grid data was taken for the first time in December 1988 during the 12R outage. This bay was considered for cathodic protection, but is not within the scope of the cathodic protection being installed. The primary purpose of this data is to establish a base line to monitor corrosion in the future. However, previous measurements were taken in November 1986 in abutting 6"x6" cruciform patterns across the entire bay. As a best approximation, 13 of these data points are at the same location as the new 6"x6" grid data set. Therefore, the new data were first compared with these 13 data points, aid then with 21 data points which include the 13 plus 8

TDR 948 Rev. 1 Page 19 of 26 additional points within one inch on either side. These comparisons were made using the chi-squared test, F-test and two-tailed t-test as described in paragraph 2.5. The mean thickness was determined aS described in paragraph 2.8.3.

(1) The data are normally distributed.

(2) The variances are equal in both comparisons.

(3) It is appropriate to use the two-tailed t-test in both comparisons.

(4) The difference between the means of the data sets is not signficant. Therefore, the corrosion is classified as "Not Significant".

(5) The current mean thickness + standard error is 905.3

+10.1 mile.

4.2.3 Bay 15D: 11/25/86 to 12/17/88 The 6"x6" grid data was taken for the first time in December 1988 during the 12R outage. This bay wan considered for cathodic protection, but is not within the scope of the cathodic protection being installed. The primary purpose of this data is to establish a base line to monitor corrosion in the future. However, a previous 1-point measurement was taken in November 1986. The location of this point may have been somewhat removed fran the location of the new 6"x6" grid data set. The previous measurement was compared with the new data set using the methods described in paragraph 2.6. The mean thickness was determined as described in paragraph 2.8.3.

(1) The new data are normally distributed.

(2) The previous measurement falls above the 99% upper bound of the new data.

(3) This implies that the corrosion may have occurred in the time period covered by this data. Therefore, the corrosion is classified as "Possible".

(4) The current mean thickness + standard error is 1056.0

+9.1 mils.

4.2.4 Bay 17A: 11/25/86 to 12/17/88 The 6"x6" grid data was taken for the first time in December 1988 during the 12R outage. This bay was considered for cathodic protection, but is not within the scope of the cathodic protection being installed. The primary purpose of this data is to establish a base line t:o monitor corrosion in the future, However, a previous

TDR 948 Rev. 0 Page 20 of 26 I-point measurement was taken in November 1986. The location of this point may have been somewhat removed from the location of the new 6"x6" grid data set. The previous measurement was compared with the new data set using the methods described in paragraph 2.6. The mean thickness was determined as described in paragraph 2.8.3.

(1) The new data are not normally distributed. However, the top three rows and the bottom four rows are each normally distributed.

(2) The previous measurement falls below the 99%

confidence interval for the top three rows, and abcve the 99% confidence interval for the bottom four rows.

(3) The corrosion is classified as "Indeterminable".

(4) The current mean thickness + standard error is 1133.1

+6.9 milsfor the top three rows and 957.4 +9.2 mils for the bottom four rows.

4.3 Result. for 6"x6' Grids at Upper Elevations 4.3.1 Bay 5 51' Elevation: 11/01/87 to 10/8/88 Three 49-point data sets were available for this bay covering the time period from November 1, 1987 to October 8, 1988. The data were analyzed as described in paragraphs 2.4 and 2.8.1.

(1) Except for the first data set, the data are normally

's distributed.

(2) The regression model is appropriate.

(3) The regression model explains 99% of the total variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness + standard error is 750.0

+0.02 mils.

(6) The corrosion rate + standard error is -4.3

+0.03 mpy.

(7) One data point was determined to be statistically different from the mean thickness. The probability of this occurring due to expected random error is less than 1% at each specific time.

TDR 948 Rev. 0 Page 21 of 26 4.3.2 Bay 9 87' Elevation; 11/6/87 to 10/8/88 Three 49-point data sets were available for this bay covering the time period from November 6, 1987 to October 8, 1988. The data were analyzed as described in paragraphs 2.4 and 2.8.2.

(1) The data are normally distributed.

(2) The mean model is appropriate than the regression model.

(3) There was no significant corrosion from November 6, 1987 to October 8, 1988.

(4) The current mean thickness + standard error is 620.2

+1.0 mile.

4.3.3 Bay 13 87' Elevation: 11/10/87 to 10/8/88 Three 49-point data sets were available for this bay covering the time period from November 10, 1987 to October 8, 1988. The data were analyzed as described in paragraphs 2.4 and 2.8.2.

(1) The data are normally distributed.

(2) The mean model is more appropriate than the regression model.

(3) There was no significant corrosion from November 10, 1987 to October 8, 1988.

(4) The current mean thickness + standard error is 635.6

+0.7 mile.

4.3.4 Bay 15 87' Elevation: 11/10/87 to 10/8/88 Three 49-point data sets were available for this bay covering the time period from November 10, 1987 to October 8, 1988. The data were analyzed as described in paragraphs 2.4 and 2.8.2.

(1) The data are normally distributed.

(2) The mean model is more appropriate than the regression model.

(3) There was no significant corrosion from November 10, 1987 to October 8, 19B8.

(4) The current mean thickness + standard error is 634.E1

+0.7 mile.

TDR 948 Rev. 0 Page 22 of 26 4.4 Results for Multiple 6"x6" Grids in Trench 4.4.1 Bay 17D Trench: 12/9/86 to 12/23/88 The two sets of measurements in the Bay 17D Trench were taken on December 9, 1986 and December 23, 1988. The 1986 data is a 7 column by 36 row array. The 1988 data is a 7 column by 42 row array. The 1986 data is at the same elevation as the lower 36 rows of the 1988 data, but is centered about 3-/12 inches to the left of the 1988 data.

To compare these two data sets, the 1986 data set and the lower 36 rows of the 1988 data set were each subdivided into six 7 column by 6 row subsets. Each pair of subsets was compared as described in paragraphs 2.5 and 2.8.3.

Fourth Subset From The Top:

The chi-squared statistic for the fourth subset from the top from the 1986 data set slightly exceeded the critical value for level of significance of 0.05, but was within the critical value for level of significance of 0.01. Also, the F statistic exceeded the critical value for levels of significance of 0.05 and 0.01. Therefore, it is inappropriate to apply the two-tailed t-test based on equal variances. However, the approximate t-test based on unequal variances can be applied. From the results of this test, it is concluded that the difference between the mean thicknesses is not significant. This implies that corrosion at this location was not significant.

All Other Subsets:

(4) The data are normally distributed.

(2) The variances are equal.

(3) Comparison of the means using the two-tailed t-test is appropriate.

(4) The difference between the means of the subsets was not significant. This implies that there was no significant corrosion in the period from December 9, 1986 to December 23, 1988.

(5) The current mean thickness + standard error of the top subset is 981.2 +6.7 mils. This is the thinnest.

area in the trench.

TDR 948

.; eRev. 0 Page 23 of 26 4.4.2 Bays 17/19 Frame Cutout: December 1988 Two sets of 6"x6' grid measurements were taken in December 1988. The upper one is located 25" below the top of the high curb and the other below the floor. There is no previous data. The upper location has been added to the long term monitoring program. with no prior data, the only possible analysis was to check the data sets for normality using the chi-squared test.

The data at the upper location are not normally distributed. The lack of normality was tentatively attributed to minimal corrosion in the lower half of the 6"x6" grid with more extensive corrosion in the upper half of the grid. To test this hypothesis, each data set was divided into two subsets, with one containing the top three rows and the other containing the bottom four rows. These subsets proved to be normally distributed, thus confirming the hypothesis. The current mean thickness + standard error is 981.7 +4.4 mile for the top three rows and 1003.8

+6.6 mile for the bottom four rows.

The data at the location below the floor is normally distributed. Also, the mean thickness is higher than at the upper location. The mean thickness + standard error is 1034.1 +6.8 mile.

4.5 Results for 6" Strips in Sand Bed Region 4.5.1 Bay ID: 11/25/86 to 12/17/88 The 7-point data set was taken in December 1988 and a single point measurement was taken in November 1986. The data were compared as described in paragraph 2.7. The previous measurement falls below the 99% lower bound of the new 7-point data set. Thus, the corrosion rate is class-ified as indeterminable. The current mean thickness +

standard error is 1114.7 +30.6 mile.

4.5.2 Bay 3D: 11/25/86 to 12/17/88 The 7-point data set was taken in December 1988 and a single point measurement was taken in November 1986. The data were compared as described in paragraph 2.7. The previous measurement falls within the 99% upper and lower bounds of the new 7-point data set. This implies that significant corrosion has not occurred at this location in the time period covered by the data. The current mean thickness + standard error is 1177.7 +5.6 mils.

4.5.3 Bay SD 11/25/86 to 12/17/88 The 7-point data set was taken in December 1988 and a single point measurement was taken in November 1986. The data were compared as described in paragraph 2.7. The

TDR 948

'Rev. 0 Page 24 of 26 previous measurement falls within the 95% upper and lower bounds of the new 7-point data set. This implies that significant corrosion has not occurred at this location in the time period covered by the data. The current mean thickness rate + standard error is 1174.0 +2.2 mils.

4.5.4 Bay 7D: 11/25/86 to 12/17/88 The 7-point data Set was taken in December 1988 and a single point measurement was taken in November 1986. The!

data was compared as described in paragraph 2.7. The previous measurement falls just above the 99% upper bound of the new 7-point data set. This implies that corrosion has possibly occurred at this location in the time period covered by the data. The current mean thickness + standerd error is 1135.1 +4.9 mile.

4.5.5 Bay 9A: 11/25/86 to 12/17/88 The 7-point data set was taken in December 1988 and a single point measurement was taken in November 1986. The.

data were compared au described in paragraph 2.7. The previous measurement falls below the 99% lower bound of the new 7-point data set. Thus, the corrosion rate is clans-s ified as indeterminable. The current mean thickness +

standard error is 1154.6 +4.8 mile.

4.5.6 Bay 13C: 11/25/86 to 12/17/88 The 7-point data set was taken in December 1988 and a single point measurement was taken in November 1986. The data were compared as described in paragraph 2.7. The previous measurement falls within the 95% upper and lower bounds of the new 7-point data set. This implies that significant corrosion has not occurred at this location Ln the time period covered by the data. The current mean thickness + standard error is 1147.4 +/-3.7 mils.

4.5.7 Bay 13D: 11/25/86 to 12/17/88 The 7-point data set was taken in December 1988 and a single point measurement was taken in November 1986. The data were compared as described in paragraph 2.7. The previous measurement falls within the 95% upper and lower bounds of the new 7-point data set. This implies that significant corrosion has not occurred at this location :n the time period covered by the data. The current mean thickness + standard error is 962.1 +22.3 mils.

4.5.8 Bay 15A: 11/25/86 to 12/19/88 The 7-point data set was taken in December 1988 and a single point measurement was taken in November 1986. Aliio, a 6"x6" grid data set was taken on December 2, 1986 at this

TDR 948 IL I RQV. 1 Page 25 of 2fi location. As a best approximation, the first 5 points in the 7-point data net are at the same location as points '18 to 42 of the 6"x6" grid, These five points all fall within the 99% confidence interval of the new 7-point data set.

The single measurement falls below the 99% lower bound.

This implies that significant corrosion has not occurred at this location in the time period covered by the data. The current mean thickness + standard error is 1120.0 +12.6 mils.

4.6 Summary ofconclusions Location Corrosion Rate** Mean Thickness***

4.6.1 6"x6" Grids in Sand Bed Region at Original Locations 11A Sand Bed Not significant 908.6 +5.0 mile liC Sand Bed Indeterminable 916.6 +10.4 mils 17D Sand Bed -27.6 +6.1 Epy 864.8 +6.8 mils 19A Sand Bed -23.7 74.3 mpy 837.9 +4.8 mile 19B Sand Bed -29.2 +0.5 mpy 856.5 +/-0.5 mile 19C Sand Bed -25.9 +4.1 mpy 860.9 +/-4.0 mile 4.6.2 6"x6" Grids in Sand Bed Region at New Locations 9D Sand Bed Indeterminable* 1021.4 +9.7 mils 13A Sand Bed Not significant* 905.3 +10.1 mile 15D Sand Bed Possible* 1056.0 +9. 1 mile 17A Sand Bed Indeterminable* 957.4 +9.2 mils 4.6.3 6"x6" Grids atUpper Elevations 5 51 ' Eleu. -4.3 +0.03 mpy 750.0 +0.02 mils 9 87' Elev. Not significant 620.3 +1.0 mils 13 87' Elev. Not significant 635.6 +0.7 mile i5 87' Elev. Not significant 634.8 +0.7 mils 4.6.4 Multiple 6'x6" Grids in Trench 17D Trench Not significant* 981.2 +6.7 mils 17/19 Frame Cutout Indeterminable* 981.7 ;4.4 mile

TDR 948 Rev. 1

.4 x Page 26 of 26 4.6.5 6" Strips in Sand Bed Region ID Sand Bed Indeterminable* 1114.7 +/-30.6 mile 3D Sand Bed Not significant* 1177.7 +5.6 mile ED Sand Bed Not significant* 1174.0 +2.2 mils 7D Sand Bed Possible* 113S.1 44.9 mile 9A Sand Bed Indeterminable* 1154.6 4..8 mile 13C Sand Bed Not significant* 1147.4 73.7 mils 13D Sand Bed Not significant* g62.1 +22.3 milo ISA sand Bed Not significant* 1120.0 412.6 Milo 4.6.6 Evaluation of Individual Measurements Below 800 Mils One data point in Bay 19A and one data point in Bay 5 Elev. 51' fell outside the 99% confidence interval and thus are statistically different.

from the mean thickness.

• Based on limited data. See text for interpretation.

• • Mean corrosion rate in mile per year + standard error of the Mean

• • • Current mean thickness in mile + standard error of the mean

Arft4 A% e-,I I1 EJ Nuclear SPECIF ICAT ION IS-32F t227-0l04 I I .__,. ._.*::.............

INSTALLATION SPECIFICATION FOR OYSTER CREEK FUNCTIONAL RE.OUIRE-ENTS FOR DRYWELL CONTAINXENT VESSEL THICKNESS EXAMINATION wl *_ _lw WA PREPARATION Q~j. (. V i DATE air ENGINEERING APPROVA - DATE a_

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E23 Nuclear NO.

DOCUMENTrS-328227-004 lTfLE FUNCTIONAL REQUIREHENTS FOR DRYWELL CONTAINMENT VESSEL THICKNESS EXAMINATION REV SJMMARY OF CHANGE APPROVAL DAIE 8 Revision 8 adds a new priority #1 Inspection location based on previous inspection. at elevation 51' 10". Also, the requirefent for "IL/-

an expanded scope inspection of this elevation 5/2/ I (performed in April per revision 7) was deleted.

O A a e . L4 f 4' aJtJ - Er jt".t In N0036 (03.90)

15-328227-004 Rev. 8 Page 2 of 10 TAI or CONNTs SEcTIOl TPAGE 1.0 SCOPE 3

2.0 REFERENCES

3 3.0 REQUIREMNTS 4 4.0 QWMITY ASSURANCE 7 5.0 iMFORNATION To BE SUBMITTED 8 6.0 ATTACMUMS a 004100:22.4

IS-328227-004 Rev. 8 Page 3 of 10 1.0 SCOPE This specification establishes the minimum requirements for ultrasonic te£sting (examination) of the Oyster creek drywell containment vessel for wall thickness measurements.

1.1 Revision 8 of this specification provides an inspection scope and frequency up to the 13R outage. Ultrasonic testing (UT) is to be performed during forced outages whenever a drywell entry is otherwise planned or required (referred to an "Outage of Opportunity") as well as refueling outages. Data shall be taken as a minimum at the time indicated in Section 3.1.3 herein.

1.2! All data shall be forwarded to Technical Functions for evaluation. Evaluation of data is not required for plant restart.

2.0 REITRMCBS 2.:L ASHE BCPV Code section V, 1977 Edition through Addenda Summer, 1978.

2.2 ASME B&PV Code Section XI, 1977 Edition through Addenda Summer, 1978.

2.:3 NRC letter dated January 14, 1987, titled 'December 19, 19B6, Third Meeting with GPU Nuclear (GPUN) to Discuoo Corrosion of the Outer Surface of the Drywell Shell."

2.41 PUN 6100-STD-7230.01, "NDE Personnel Qualification and Certification."

2.!; GPUN 6130-QAP-7209.24, Rev. 0, "Ultrasonic Thickness Measurement."

2.1; GPU" Sketch, Dwg. No. SK-S-89.

2.7 GPU Sketch, Dwg. No. SK-253.

2.13 QC Thickness Data Sheet as listed herein.

004/0022.5

IS-328227-004 Rev. 8 Page 4 of 10 3.0° BEUIBMORTS 3.1 Non-destructive Examinations 3.1.1 Personnel Qualification 3.1.1.1 Ultrasonic personnel shall be qualified and certified in accordance with Reference 2.4 or a GPUN approved vendor SNT-TC-1A program.

3.1.2 Examination Methods/Equipmnt 3.1.2.1 Ultrasonic examination pulse-echo equipment cap-able of thickness measurement by the digital and A-scan on a CRT screen shall be utilized. One inmtrument capable of both presentations or two separate instruments are acceptable.

Digital readout equipment shall have printout capabilities and memory storage traceable to sequential readings.

The digital readout equipment shall be the primary technique employed to measure wall thinning. A-scan on a CRT screen shall be utilized to confirm in wall reflectors. The UT method shall be performed in accordance with Reference 2.5.

3.1.3 Data Acquisition Priorities Locations 3.1.3.1 Each area indicated in Section 3.1.3.2 shall be inspected, at the time interval required, on the basis of Its assigned priority.

Inspection requirements for each priority are as follows Priority 1 areas are to be inspected in each outage of opportunity but not more frequently than approximately once every three months.

Priority 2 areas are to be inspected in an outage of opportunity if the previous set of data was taken 18 months or more before the outage.

3.1.3.2 Revision 8 of this specification adds several priority #1 locations at elevation 51' 10i. Those locations were initially inspected in April 1990.

004/0022. 6

1S-328227-004 Rev. 8 Page S of 10 The drywell vessel wall at the following locatLone shall be invostigated:

a. Grids at floor elevation 11'3" original QC 6"x6" Grid Thicknoan (SO@ Exhibits Data Sheet 1 & 2 Number priority 9 D 87-026-59 1 11 A 86-049-24 1 11 C 86-049-37 1 13 A 87-026-58 1 13 D 87-026-67 1 15 0 87-026-58 1 17 A 87-026-58 1 17 D 86-049-26 1 17/19 Frame 87-026-66 1 19 A 86-049-27 1 19 B 86-049-28 1 19 C 86-049-29 1

b. Original QC Thickness Grids At Data Sheet Floor Elevation 51-Di 87-026-26 1 Zlevation 51', Day 13 87-026-122 1 Elevation 51', Bay 5 87-026-124 1 Elevation 51', say 15 87-026-123 1 Elevation 52', Bay 13 (area 32)

Top of Biological 87-026-144 1 I

Shield 86-20 87-026-30 1 004/0022.7

IS-328227-004 Rev. 8 Page 6 of 10

b. (Cont.) Original QC Thickness Gride At Data sheet Ptriorty Top of Biological Shield 86-28 - 87-026-37 1 Top of Biological Shield 86-31 87-026-38 1 C. Strips at original QC Ploor Ele- Thickness vation 1183- D 6t Sheet

- Priority 1D 87-026-54 2 3D ~87-026-SS 5D 87-026-56 2 7D 87-026-57 2 9A 87-026-60 2 13C 87-026-61 2 15A 87-026-62 2 3.1.4 Records 3.1.4.1 All grid UT data in Section 3.1.3.2 shall be taken at the same locations as those taken previously and using the 6"x6" grid (7x7 array) am defined in QC data sheet 86-049-13. The readings shall be taken within the tolerance specified in 4.2.1.

3.1.4.2 All UT data in Section 3.1.3.2 shaLl be taken at the name location, an those indicated on the original thickness data sheets.

3.2 Organizational and Functional Reeuirement" 3.2.1 Work to be performed by Maintenance, Construction and Facilities (MCP) 3.2.1.1 Supply tools and materials required for surface preparation of the coated steel (coating removal) as required.

3.2.1.2 Prepare the 6"x6' grid identified in 3.1.3.1 and 3.1.3.2, and 3.1.3.3 as directed by Quality Control (QC). Preparation technique shall be such that no base material in removed.

004/0022.8

IS-328227-004 Rev. 8 Page 7 of 10 3.2.1.3 After UT inspection of grids, the area shall be coated with Syncogel whit. Z.P. grease stock

1. 412-120-66-00-0.

3.2.1.4 Temporary planking shall be provided as necessary at the top of the biological shield extending to the drywell wall. It is not intended that the planking be continuous for the entire circumference. The planking shall be ouch that it can be moved along as work continues.

3.2.2 Duties to be performed by Quality Assurance Department 3.2.2.1 The NDE/ISx Group shall perform the thickness examinations required by this specification and interface with Technical Functions as required.

3.2.2.2 The NDE/ISI Group shall be responsible for the conduct and implemontation of the requirements of this specification and the interface requirements of 3.2.2.

4.0 D9aL!TT ASSURANCE 4.1 All work shall be performed in accordance with OPUN Operational QA Program. This work is classified Important to Safety/Nuclear Safety Related.

4.2 Locations of Inspection Points 4.2.1 NDZ/ISI shall verify that locations (specified in Section 3.1.3.2) of UT measurements performed are within +/-1/8" of the designated locations. This shall be accompliuhed by use of a template (see Exhibit 2). The drywell wall was previously stamped at the notches provided In the tem-plate with low stress die stamps. The locations of investigation shall be repeated by use of these stamp.

for relocating the template.

4.2.2 This template shall be made of 304 or 316 S5 sheet metal of approximately .030 inch thickness. The template shall be six inches square with circular holes cut out on one inch centers. The diameter of the holes shall be suffi-cient to allow 1/2 inch diameter UT transducers to fit through tho template. Typical grid pattern shall be as shown in Exhibit 2.

004/002:2.9

Is-328227-004 Rev. 8 Page 8 of 10 5.0 INtWORTrON TO BE SUBMWITED 5.3. UT data sheets and calibration sheets in accordance with Reference 2.5. Analysi, of data is not required prior to restart.

6.0 hfalCR^NTS 6.1 Exhibit 1 - Typical Area of Exams at Elevation 11'3".

6.2 Exhibit 2 - Typical Grid Pattern (60x6 M ).

6.I Exhibit 3 - UT Layout Number System.

004/0022.10

IS-328227-004 Rev. 8 Page 9 of 10 EXHIBIT 1 Typical Area of exams at RlOtatIon 11' 3" Q@LribO£4

// Il30 EXHIBIT 2 Tpic4al arid Pattern 16" x 6")

.L IT 0VIP 004/0022.11

IS-328227-004 Rev. 8 Page 10 of 10 EXHIBIT 3 UT Layout NuMberina System A B C D Bay 1 1 2 3 4 3 5 6 7 8 5 9 10 l1 12 7 13 14 15 16 9 17 18 19 20 11 21 22 23 24 13 25 26 27 28 15 29 30 31 32 17 33 34 35 36 19 37 38 39 40 004/0022 . 12

L The basic purpose of this calculation ia to update the thickness measurement analyses documented in References 3.7, 3.8, and 3.11 by incorporating the measurements taken in March and April 1990.

Spocific objectives of this calculation are:

(1) Statiutlcally analyz. the thickness measurements in the sand bad region to determine the mean thickness and corrosion rate.

(2) Analyze the data taken since the 12R outage for Says llA, 11C, 17D, 19A, 19B, 19C, and the Frame Cutout between Bays 17 and 19 to determine If cathodic protection has reduced the corrosion rate.

K (3) Statistically analyze the thickness measurements for Bay 5 at elovation 51 and Bays 9, 13 and 15 at Alevation 87 to determine the mean thickness and corrosion rate.

(4) To the extent possible, analyze the data for the now locations at elevation 51' and elevation 52'.

001/0004J.

N 010(10088

I Calc. No. C-1302-187-5300-C11 Rev. NO. 0 Page 2 of 454 2 0 SUMHMRY OF WSMLT8 Bay LAMA Corrooion Rate ** Mean Thickness "* F-Ratio 2.1 sand Hed Reoion With Cathodic Protection - All Data 11A -15.6 +/-2.9 mpy 870.4 + 5.7 mile 5.4 11C 5'op -35.2 +/-6.8 mpy 977.0 +/-12.5 milo 4.6 11C ilottom -22.4 +4.3 mpy 865.0 +/- 7.8 milo 4.9 17D -25.0 +2.0 mpy 829.5 +/- 4.0 milo 29.4 19A -21.4 +/-1.5 mpy 807.6 +/- 3.0 mile 39.5 19D -19.0 +/-1.7 mpy 836.9 +/- 3.2 mile 21.3 19C -24.3 +/-1.3 mpy 825.1 +/- 2.3 milo e 66.2 2.2 Sand Bed Region With Cathodic Protection - Since October 1988 11A Not significant* 878.0 t 5.9 mile 11C Top Not Significant* 996.6 +/- 8.3 milo liC Bottom Not Significant* 878.1 . 5.6 milo 17D -23.7 +/-4.6 mpy 830.1 +/- 3.8 mile 2.7 19A -20.6 13.9 mpy 808.2 +/- 3.2 mile 2.8 19B -11.8 +/-3.9 mpy 841.2 + 3.3 milo 0.9 19C -21.5 13.5 mpy 826.3 + 2.9 mile 3.7 2.3 Sand Bed Reaion Jraine Cutout 17/19 Top Not Significant* 986.0 + 4.7 mile 17/1S5 Bottom Not Significant* 1008.4 +/- 3.9 milo 2.4 Sand Bed Region Without Cathodic Protection 9D Not Significant* 1021.7 + 8.9 mile 13A -39.1 +/- 3.4 mpy 853.1 +/- 2.4 mile 16.9 13D Indeterminate 931.9 +/-22.6 mile 15D Not Significant* 1056.5 + 2.3 milo 17A Iop Not Significant* 1128.3 + 2.2 milo 17A Bottom Not Significant* 745.2 + 2.1 mile 1.3

• Net statistically significant compared to random variations in measuremerto

• • Mean corrosion rate in mile per year +/- standard error of estimate

• • • Beat estimate of current mean thicknesm in mile +/- standard error of the mean 001/0004.2

I Calc. No. C-1302-187-5300-O:1 Rev. No. 0 Page 3 of 454 Bay l Area Corgosion Rate ** Mean Thicknesn ***

2.5 Elevation 51' 5/D..12 - 4.6 + 1.6 745.2 + 2.1 Mils 1.3 5/5 Indeterminate 745.1 + 3.2 mile 13/3% Indeterminate 750.8 +/-11.5 mila 15/23 Indeterminate 751.2 +/- 3.8 mile 2.6 Elevation 52' 7/2!i Indeterminate 715.5 + 2.9 13/6 Indeterminate 724.9 + 2.9 13/3;2 Indeterminate 698.3 + 5.0 19/1:i Indeterminate 712.5 + 3.1 2.7 Elevation-2t 9 Not significant* 619.9 +/- 0.6 13 Not Significant* 636.5

• 0.8 15 Not Significant* 636.2 +/- 1.1 2.5 Apparent Corrosion-Rateg These estimates of the corrosion rate are based on a least equares fi1:

of the data. In those case. where the F-Ratio is less than 1.0 they should not be used to make future projections. For bays with cathodic protection, thqu. appgrent rate. are for the period from October 1988 to April 1990. For the other bay*, it is for all data.

Apparent Apparent Corrosion Corrosion Rate (mov) F-RRLU2 Say Rate (mptl F-Ratio 11A -16.2 +/- 8.6 0.2 9D -21.0 +/-18.1 0.1 lic I'op -25.0 +/-10.6 0.6 13A -39.1 +/- 3.4 16.9 liC Hottom -16.7 + 7.1 0.6 15D - 4.6 +/- 4.8 0.1 17D -23.7 +/- 4.6 2.7 17A Top - 6.8 + 3.7 0.3 19A -20.6 +/- 3.9 2.8 17A Bottom -17.7 +/- 7.6 0.01 193 -11.8 + 3.9 0.9 5 21. 51' - 4.6 + 1.6 1.3 19C -21.5 + 3.5 3.7 9 EL 87' - 0.2 +/- 0.9 zero 17/19 Top - 8.2 +10.7 0.1 13 EL 87' zero 17/11I Bottom -13.1 +11i. 6 0.1 15 EL 87' zero 001/0004.3

aI Calc. No. C-1302-187-5300-CIl Rev. No. 0 Page 4 of 454 2.6 Evaluaticn of lndividual Moasuraments ExCeedina 99%i99% Tolerance interval One data point in Bay 5 Elov. 51' fell outside the 99%/99% tolerance interval and thus is statistically different from the mean thickness.

Based on a linear regression analysis for this point, it is concluded.

that the corrosion rate in this pit is essentially the same as the overall grid.

001/0004.4

6 Cale. No. C-1302-187-S300-011 Rev. No. 0 Page 5 of 454 3.0 !tMERENCES

.3.1 GPUN Safety Evaluation SE-000243-002, Rev. 0, "Drywell Steel Shell Plate Thickness Reduction at the Base Sand Cushion Entrenchment Region'

.3.2 OPUN TDR 854, Rev. 0, "Drywall Corrosion Assessment" 3.3 0PUX TDR 851, Rev. 0, -Assessment of oyster Creek Drywell Shell"

.3.4 GPUN Installation Specification IS-328227-004, Rev. 3, 'Functional Requirewanta for Drywall Containment Vessel Thickness Examination"

3.5 Applied Regression Analysis, 2nd Edition, N.R. Draper & H. Smith, John Wiley & Son8, 1981

3.6 Statistical Concepts and Methods, G.X. Bhattacharyya & R.A.

Johnson, John Wiley & sons, 1977

.3.7 GPUN Calculation c-1302-187-S300-00S, Rev, 0, "Statistical Analysis of Drywall Thickness Data Thru 12-31-88"

3.8 GPUN TOR 948, Rev. 1, "Statistical Analysi. of Drywell Thickness Data*

3.9 Experimental Statistics, Mary Gibbons Natrella, John Wiley & Soan, 1966 Reprint. (National Bureau of Standards Handbook 91) 3.10 Fundamental concepts in the Design of Experiments, Charles C.

Hicks, Saunders College Publishing, Port Worth, 1982

.3.11 GPUN Calculation C-1302-187-5300-008, Rev. 0, "Statistical Analys~s of Drywall Thickness Data thru 2-8-90w 001/0004.5

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 6 of 454 4.0 ISSUNPTWVU J UBSI3C O&A 4.1. Ackcrqund The design of the carbon steel drywell Includes a sand bed which is located around the outside circumference between elevations 8'-11-1/4' and 12'-3". Leakage was observed from the sand bed drains during the 1980, 1983 and 1986 refueling outages indicating that water had intruded into the annular region between the drywell shell and the concrete shield wall.

The drywall shall was inupected in 1986 during the 10R outage to determine if corrosion was occurring. The inspection methods, results and conclusions are documented in Ref. 3.1, 3.2, and 3.3.

As a result of these inspections It wag concluded that a long term monitoring program would be established. This program includes repetitive Ultrasonic Thickness (UT) measurements In the sand bed region at a nominal elevation of 111-3" in bays 112, llC, 17D, 19A, 19B, and 19C.

The continued pretence of water in the sand bed raised concerns of potential corrosion at higher elevations. Therefore, UT measurements were taken at the 51 and 87' elevations in November 1987 during the llR outage. As a result of these inspections, repetitive measurements in Bay S at elevation 1S and In Says 9, 13 and IS at the 87' elevation were added to the long term monitoring program to confirm that corrosion ia not occurring at these hlgher elevations.

A cathodic Protection system was installed in selected regions of the sand bed during the 12R outage to minimize corrosion of the drywell. The cathodLc protection system was placed in service on January 31, 1989. The long term monitoring program was also expanded during the 12R outage to Include measurements in the sand bed region of Bays ID, 3D, 50, 7D, 9A, 13A, 13C, 13D, ISA, 150 and 17A which are not covered by the cathodic protection system. It also includes measurements in the wand bed region between fays 17 and 19 which is covered by the cathodic protection system, but does not have a reference electrode to monitor its effectiveness in this region.

The high corrosion rate computed for Bay 13A in the sand bed region through Uebruary 1990 (Ref. 3.11) raised concerns about the corrosion rate in the sand bed region of Bay 130. Therefore, the monitoring of this location using a 6"x6V grid was added to the long term monitoring program. In addition, a 2-inch core sample was removed in hArch 1990 from a location adjacent to the 6"xVW monitored grid in Say 13A.

001/0004.6

Calc. No. C-1302-187-5300-D11 Rev. No. 0 Page 7 of 454 Measurements taken in Bay S Area D-12 at elevation 51' through March 1990 indicated that corrosion Is occurring at his location.

Therefore, survey measurements were taken to determine the. thilnnest locations at elevation 51'. As a result, three new locations were added to the long term monitoring program (Bay S Area 5, Bay 13 Area 31, and Buy 15 Area 2/3).

The indication of ongoing corrosion at elevation 51' raised concerns about potential corrosion of the plates immediately above which have a smaller nominal thickness. Therefore, survey measurements were taken in April 1990 at the 52' elevation in aLl bays to determine the thinnest locations. As a result of this survey, four now locations were added to the long term monitoring plan at elevation 52' (Bay 7 area 25, Bay 13 Area 6, Bay 13 Area 32, and Bay 19 Area 13).

Some measurements in the long term monitoring program are to be taken at each outage of opportunity, while others are taken dur..ng each refueling outage. The functional requirements for thesn inspections are documented in Ref. 3.4. The purpose of the UT measurements iv to determine the corrosion rate and monitor it over time, and to monitor the effectiveness of the cathodic protection system.

4.2 Selection of Areas to be Monitored A program was initiated during the 11R outage to characterize the corrosion and to determine its extent. The details of this inspection program are documented in Ref. 3.3. The greatest corrosion was found via UT measurements in the sand bed region at the lowest.,accessible locations. Where thinning was detected, additional measurements were made in a cross pattern at the thinnest section to determine the extent In the vertical and horizontal directions. Having found the thinnest locations, measurements were made over a 6"x6" grid.

To determine the vertical profile of the thinning, a trench was excavated into the floor in Bay 17 and Day 5. Bay 17 was select:ed since the extent of thinning at the floor level was greatest in that area. It wan determined that the thinning below the top o:

the curb was no more severe than above the curb, and became leou severe at the lower portions of the sand cushion. Bay 5 was excavated to determine if the thinning line was lower than the floor level in areas where no thinning wao detected above the floor. There were no significant indications of thinning in Bay S.

001/0004.7

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 8 of 454 It was on the basis of these findings that the 6"x6" grids in Bays 11A, 11C, 17D, 19A, 19B and 19C were selected as representative locations for longer term monitoring. The initial measurements at these locations were taken in December 1986 without a template or markings to identify the location of each measurement.

Subsequently, the location of the 61x6" grids were permanently marked on the drywell shell and a template in used in conjunction with theose markings to locate the UT probe for successive measurements. Analyses have shown that including the non-template data in the data base creates a significant variability in the thickness data. Therefore, to minimize the effects of probe location, only those data set. taken with the template are included in the analyses.

The presence of water in the sand bed also raised concern of potential corrosion at higher elevations. Therefore, UT measurements wore taken at the 51 and 87' elevations in 1987 during the 11M outage. The measurements were taken in a band on 6-inch centers at all accessible regions at theoe elevations.

Where these xeasurements Indicated potential corrosion, the measurements spacing was reduced to 1-inch on centers. If these additional readings indicated potential corrosion, measurements were taken on a 6"x6" grid using the template. It was on the basis of these inspections that the 6"x6" grids in Bay 5 at elevation 513 and in bays 9, 13 and 15 at the 87 elevation were selected as representative locations for long term monitoring.

A cathodic protection system was installed in the sand bed region of fays 11A, 11C, 17D, l9A, 19B, 19C, and at the frame between Bays 17 and 19 during the 12R outage. The system was placed in service on January 31, 1989.

The long term monitoring program was expanded as follows during the 12R outage:

(1) Measurements on 6"x6" grids in the sand bed region of Bays 9D, 13A, 150 and 17A. The basis for selecting these locations to that they were originally considered for cathodic protection but are not included in the system being installed.

(2) Measurements on 1-inch centers along a 6-inch horizontal strip in the sand bed region of Day. 10, 3D, 5D, 7D, 9A, 13C, and ISA. These locations were selected on the basis that they are representative of regions which have experienced nominal corrosion and are not within the scope of the cathodic protection system.

001/0004.8

Calc. No. C-1302-187-5300-011 Rov. No. 0 Page 9 of 454 (3) A 6"X6" grid in the curb cutout between Bays 17 and 19. The purpose of theme measurements is to monitor corrosion in thi..

region which is covered by the cathodic protection system bu.t doea not have a reference electrode to monitor its performance.

The long term monitoring program was expanded in March 1990 au followas (1) Measurements in the sand bed region of Bay 13D: This location was added due to the high indicated Corrosion rate in the ca.nd bed region of Bay 13A. The measurements taken in March 199CI were taken on a lx6" grid. All subsequent measurements are to be taken on a 6Wx6" grid.

(2) Measurement. on 6Wx6" grids at the following locations at elevation 51s: Bay S Area 5, Bay 13 Area 31, and Bay 15 Area 2/3. These locations were added due to the indication of ongoing corrosion at elevation 51', Bay 5 Area D-1.

The long term monitoring program was expanded in April 1990 by adding the following locations at elevation 52': Bay 7 Area 25, Bay 13 Area 6, Bay 13 Area 32, and Bay 19 Area 13. All measurements are taken on 6'x6" grids. Those locations were added due to the indIcation of ongoing corrosion at elevation 51' and :he fact that the nominal plate thickness at elevation 52' is less than at elevation 51'.

4.3 t? Measurements The UT measurements within the scope of the long term monitoring program are performed in accordance with Ref. 3.4. This involves taking UT measurements using a template with 49 hole. laid out on a 6"x6" grid with 1" between centers on both axes. The center row is used in those bays where only 7 measurements are made along a 6-inch horizontal strip.

The first oet of measurements were made in Deocember 1986 without the use of a template. Ref. 3.4 epecLfleo that for all submequent readinga, QA shall verify that locations of UT measurements performed are within +/- 1/4" of the location of the 1986 UT measurements. It also specifies that all subsequent measurements are to be within +/- 1/8" of the designated locations.

001/0004.9

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 10 of 454 4.4 Data at Plug TLocations Seven core samples, each approximately two inches in diameter wex*

removed from the drywell vessel shell. These sample. were evaluated in Ref. 3.2. Five of these sample. were removed withi:-i the 6"x6" grids for Days llA, 17D, l9A, 19C and Say 5 at elevation 51'. These locations were repaired by welding a plug in each hole. Since these plugs are not representative of the drywell shell, UT measurements at these locations on the 6~x6W grid must be dropped from each data set.

The following specific grid points have been deleted:

Bay Area Points 11A 23, 24, 30, 31 17D 15, 16, 22, 23 19A 24, 25, 31, 32 19C 20, 26, 27, 33, 5 EL 51' 13, 20, 25, 26, 27, 28, 33, 34, 35 The core sample removed in the sand bed region of Bay 13A was no1:

within the monitored 6"x6 grid.

4.5 Bases for Statiotical Analysis of 6"x6V Grld Data 4.5.1 Amsumptions The statistical evaluation of the UT measurement data to determine the corrosion rate at each location is based on the following assumptions:

(1) Characteriation-of the scattering of data over each 6"x6 grid is such that the thickness measurements are normally distributed.

(2) Once the distribution of data for each 6"x6" grid is found to be normal, then the mean value of the thickness is the appropriate representation of the average condition.

(3) A decrease in the mean value of the thickness with time is representative of the corrosion occurring within the 6"x6" grid.

001/0004.10

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 11 of 454 (4) If corrosion has ceased, the moan value of the thickness will not vary with time except for random errors in the UT measurements.

(5) If corrosion is continuing at a constant rate, the mean thickness will decrease linearly with time. In this cage, linear regression analysis can be used to fit the mean thickness values for a given zone to a straight line as a function of time. The corrosion rate in equal to the slope of the line.

The validity of these assumptions in assured by:

(a) Using more than 30 data points per 6"x6" grid (b) TetiLng the data for normality at each 6"x6" grid location.

(c) Testing the regression equation as an appropriate model to describe the corrosion rate.

These tests are dlscusoed in the following section; In cases where one or more of those assumptions proves to be invalid, non-parametric analytical techniques can be used to evaluate the data.

4.5.2 Statistical Ayuroach The following steps are performed to test and evaluate the UT measurement data for those locations where 6"x6" grid data has been taken at least three times:

(1) Edit each 49-polnt data set by setting all invalid points to zero. Invalid point. are those which are declared invalid by the UT operator or are at a plug location. (The computer programs used in the following steps ignore all zero thickness data points.)

(2) Perform a Chi-squared goodness of fit test of each 49 point data set to ensure that the assumption of normality is valid at the S% and IS level of significance.

(3) Calculate the mean thickness and variance of each 49 point data set.

(4) Perform an Analysis of Variance (ANOVA) P-test to determine if there Le a significant difference between the means of the data sets.

001/0004.11

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 12 Of 454 (5) Using the mean thickness values for each 6"x6V grid.,

perform linear regression analyule over time at each location.'

(a) Perform F-test for significance of regression at the 5 level of significance. The result of this test indicates whether or not the regression model in more appropriate than the mean model. In other words, lt toets to see if the variation of the regression model is -

statistically significant over that of a mean model.

(b) Calculate the ratio of the observed F value to the critical F value at 5% level of significance. For data sets where the Residual Degroes of Freedom in ANOVA is 4 to 9, this F-Ratio should be at least 8 for the regression to be considered "useful" as opposed to simply "significant." (Ref. 3.5 pp. 92-93, 129-133)

(c) Calculate the coefficient of determination (l2 ) to assess how well the regression model explain. the percentage of total error and thus how useful the regression line will be as a predictor.

(d) Determine If the residual values for the regression equations are normally distributed.

(e) It the regression model is found to be appropriate, calculate the y-intercept, the slope and their respective standard errors.

The y-Lntercept epresents the fitted mean thickness at time zero, the slope represents the corrosion rate, and the standard errors represent the uncertainty or random error of these two parameters.

(6) Uue a X factor from Table A-7 of Reference 3.9 and the standard deviation to establish a one-sided 99%/99% tolerance limit about the mean thickness values for each 6"x6" grid location to determine whether low thickness measurements or Ooutliers" are statistically significant. If the data points are greater than the 99%/99% lower tolerance limit, thon the difference between the value and the mean Ls deemed to be duo to expected random error. However, if the data point is less than the lower 99%/99%

tolerance limit, this implies that the difference ia statistically significant and is probably not due to chance.

001/0004.12

calc. No. C-1302-187-5300-01l Rev. No. 0 Page 13 of 454 4.6 AnalvaLe of Tw-o 6 x" Grid Data0Seto Regresuion analysis is inappropriate when data is available at only two points in time. However, the t-test can be u.4d to determine If the means of the two data veto are statiutically dlfferent.

4.6.1 AssumotLons, This analysis is based upon the following assumptions:

11) The data in each data set la normally distributed.

(2) The variancoo of the two data Bets are equal.

4.6.2 Statiotical ADiroach The evaluation takes place in three steps:

(1) Perform a chi-oquared test of each data net at 5% and 1i levels of significance to ensure that the assumption of normality is valid.

(2) Perform an F-test at 5% and 1% level of significance of the two data sets being compared to ensure that the assumption of equal variances is valid.

(3J Perform a two-tailed t-teet for two independent samples at the 5% and 1i levels of signlficance to determine if the means of the two data sets are

.statistically different.

A conclusion that the means are _=nstatistically different is interpreted to mean that significant corrosion did not occur over the time period represented by the data.

However, if equality of the means is rejected, this implies that the difference is statistically significant and could be due to corrosion.

4.7 Analysis of Single 6"x6" Grid Data Set In those cases where a 6"x6" data sot is taken at a given location for the first time during the current outage, the only other data to which they can be compared are the UT survey measurements taken at an earlier time. For the most part, theme are single point measurements which wers taken in the vicinity of the 49-point data oet, but not at the exact location. Therefore, rigorous statistical analysis of these single data nets is impossible.

However, by making certain assumptions, they can be compared with the previous data points. If more extensive data is available at the location of the 49-point data met, the t-teot can be used to compare the means of the two data sets as described In paragraph 4.5.

001/0004.13

Calc. No. C-1302-187-S300-011 Rev. No. 0 Page 14 of 454 When additional measurementu are made at those exact locations during future outages, more rigorous statistical analyses can be employed.

4.7.1 Assumptions The comparison of a single 49-point data sets with previoas data from the same vicinity in based on the following asuumptione:

(1) Characterization of the scattering of data over the 6Wx6 grid is such that the thickness measurements are normally distrLbuted.

(2) once the distribution of data for the 6"x6" grid Lo found to be normal, then the mean value of the thickness is the appropriate representation of the average condition.

(3) The prior data is representative of the condition al; this location at the earlier date.

4.?.2 StatIstical hporoach The evaluation takes place in four stepst (1) Perform a chi-squared test of each data set to onsure that the assumption of normality li valid at the 951 and 99% confidence levels.

(2k) Calculate the moan and the standard error of the mean of the 49-point data aet.

(3) Determine the two-tailed t value from a t distribution table at levels of significance of 0.05 and 0.01 for n-. degrees of freedom.

(4) Use the t value and the standard error of the mean to calculate the 95% and 99% confidence intervals about the mean of the 49-point data set.

(5) Compare the prior data point(s) with these confidence intervals about the mean of the 49-point data sets.

If the prior data falls within the 95% confidence intervals, it provides some assurance that significant corrosion has not occurred in this region in the period cf time covered by the data. If it falls within the 99%

confidence limits but not within the 95% confidence limits, this implication is not as strong. In either cane, the corrosion rate will be interpreted to be "Not Significant".

001/0004.14

Cale. No. C-1302-187-5300-011 Rev. No. 0 Page 15 of 454 If the prior data falls above the upper 99% confidence limit, It could mean either of two thlngs: (1) qignificstnt corrosion has occurred over the time period covered by the data, or (2) the prior data point was not representativo of the condition of the location of the 49-point data set J.n 1986. There in no way to differentiate between the two.

In this case, the corrosion rate will be interpreted to be "Possible".

If the prior data falls below the lower 99% confidence limit, it means that it in not representative of the condition at this location at the earlier date. In thia case, the corrosion rate will be interpreted to be "Indeterminable".

4.8 Analysis of Single 7-Point Data Set In those cases where a 7-point data uet li taken at a given location for the first time during the current outage, the only other data to which they can be compared are the UT survey measurements taken at an earlier time to identify the thinnest regions of the drywell ahell in the sand bed region. For the most part, these are single point measurements which were taken in the vicinity of the 7-poLnt data Bets, but not at the exact locations.

However, by making certain assumptions, they can be compared wi:h the previous data points. If more extensive data is available at the location of the 7-point data net, the t-test can be used to compare the means of the two data sets as described in paragraph 4.5.

When additional measurements are made at these exact locations during future outages, more rigorous statistical analyses can be employed.

4.8.1 Aefumotions The comparison of a single 7-point data Rets with previous data from the same vicinity Ls based on the following assumptions (1) The corrosion in the region of each 7-point data ziet is normally distributed.

(2) The prior data is representative of the condition at this location at the earlier date.

The validity of these assumptions cannot be verified.

001/0004.15

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 16 of 454 4.8.2. statietical Approach The evaluation takes place in four steps:

(1) Calculate the nean and the standard error of the mean of the 7-point data set.

(2) Determine the two-tailed t value uoing the t distribution tableo at levels of significance of 0.05 and 0.01 for n-1 degrees of freedom.

(3) Use the t value and the standard error of the mean to calculate the 95% and 99% confidence intervals about the mean of the 7-point data get.

(4) compare the prior data point(s) with thee. confidence intervals about the mean of the 7-point data sets.

If the prior data falls within the 95% confidence intervals, it provides some assurance that significant corrosion has not occurred in thin region in the period of time covered by the data. if it falls within the 99%

confidence limits but not within the 95% confidence limits, this implication is not as strong. in either case, the corrosion rate will be interpreted to be "Not Significant".

If the prior data falls above the upper 99% confidence interval, it could mean either of two thingqs (1) significant corrosion has occurred over the time period covered by the data, or (2) the prior data point was not representative of the condition of the location of the 7-point data set in 1986. There Ls no way to differentiate between the two. In this case, the corrosion rate will be interpreted to be "Possible".

If the prior data fails below the lower 99% confidence limit, it moans that it lI not representative of the condition at this location at the earlier date. In this case, the corrosion rate will be interpreted to be ZIndeterminableo.

4,.g Evaluation of Drywell hean ThLcknges This section defines the methods used to evaluate the drywell thickness at each location within the scope of the long tetm monitoring program.

001/0004.16

4 I Calc. No. C-1302-187-5300-011 Rev. No . 0 Page 17 of 454 4.9.1 Evafytion of Moan Thickr Us no Iteprerssion MAlysig The following procedure is used to evaluate the drywell mean thickness at those locations where regression analysis has been deemed to be more appropriate than the mean model.

(1) The bout estimate of the mean thickness at thaws locations is the point on the regression line corresponding to the time when the most recent sot of measurements was taken. Xn the SAS Regression Analysis output (App. 6.2), this is the last value in the column labeled *PREDICT VALUE*.

(2) The best estimate of the *tandard error of the mean thickness is the standard error of the predicted value used above. In the SAS Regression Analysis output, this in the last value in the column labeled "STO ZRR PR0DICT".

(3) The two-sided 95% confidence interval about the mean thickness Ls equal to the mean thickness plu. or minus t times the estimated otandard error of the mean. This is the interval for whlch we have 95%

confidence that the true mean thickness will fall within. The value of t in obtained from a t distribution table for eoual talla at n-2 degrees of freedom and 0.05 level of significance, where n Le the number of sets of measurements used in the regression analysis. The degrees of freedom is equal to n-2 because two parameters (the y-intercept and the slope) are calculated in the regression analysis with n mean thicknesees as input.

(4) The one-sided 95V lower limit of the mean thickness is equal to the estimated mean thickness minus t tims4 the estimated standard error of the mean. This is the mean thicknes, for which we have 95%

confidence that the true mean thickness does not fall below. In this case, the value of t Is obtained from a t distribution table for QM tail at n-2 degrees of freedom and 0.05 level of significance.

4.9.2 Evaluation o£ Mean Thickness Uuing Mean Model The following procedure Ls used to evaluate the drywoll mean thickness at those locations where the mean model is deemed to be more appropriate than the linearoregresaion model. This method is consistent with that used to evaluate the mean thickness using the regression model.

001/0004.17

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 18 of 454 (1) Calculate the mean of each met of UT thickness measurements.

(2) Sum the means of the sets and dLvide by the number of sets to calculate the grand moan. This is the best estimate of the mean thickness. In the SAS Regression Analysis output, this is the value labelled "DEP MEAN".

(3) Using the means of the sets from (1) am input, calculate the standard er about the mean. This is the beat estimate of the standard error of the mean thickness.

(4) The two-sided 95% confidence interval about the mean thickness is equal to the mean thickness plus or minus t times the estimated standard error of the mean. This is the interval for which we have 95%

confidence that the true mean thickness will fall within. The value of t in obtained from a t distribution table for eoual tails at n-l degrees of freedom and 0.05 level of significance.

(S) The one-sided 95% lower limit of the mean thickness is equal to the estimated mean thickness minus t times the estimated standard error of the moan. This is the mean thickness for which we have 95%

confidence that the true mean thickness does not fall below. In this case, the value of t is obtained from a t distribution table for one til2 at n-1 degrees of freedom and 0.05 level of significance.

4.9.3 Evaluation of Mean Thickness Usino Single Data Set The following procedure is used to evaluate the drywell thickness at those locations where only one set of measurements li available.

(1) Calculate the mean of the set of UT thickness measurements. This io the best estimate of the mean thickness.

(2) Calculate the standard error of the mean for the set of UT measurements. Thi is the best estimate of the standard error of the mean thickness.

Confidence intervals about the mean thickness cannot be calculated with only one data set available.

001/0004.18

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 19 of 454 4.10 Evaluation of Drywell Corrosion Rate 4.10.1 Mean Hodol If the ratio of the observed F value to the critical F value in less than 1 for the F-teat for the significancti of regression, it indicates that the mean model i+/- more appropriate than the regression model at the 5t level oi significance. In other words, the variation in mean thickness with time can be explained solely by the randco variationo in the measurements. This means that the corrosion rate is not significant compared to the randoni variations.

In this case, an F-test is performed to compare the variability of the data oat moans between data sets with the variability of individual measurements within the da.ta sets. If the observed F value is less than the critical F value, it confirms that the mean model is appropriate.

If the F-tost indicates that the variability of the mearis is significant, the Least Significant Difference (LSD) is computed. This is the maximum difference between data set mean thicknesses that can be attributed to random variation in the measurements. If the difference between the mears of data sets exceeds LSD, it indicates that difference is significant. The difference between means Is subtracted from LSD and the result is divided by the time between measurements to estimate the "Significant Corrosion Rate" in mile per year (mpy). If the difference between the mqeano does not exceed LSD, then it li concluded that no significant corrosion occurred during that period of tinae.

4.10.2 ReareeSion Model If the ratio of the observed F value to the critical F value is 1 or greater, it indicates that the regression model is more appropriate than the mean model at the St level of significance. In other words, the variation ir.

mean thickness with time cannot be explained oolely by the random variations in the measurements. This means that the corrosion rate is significant compared to the random variations.

Although a ratio of 1 or greater indicates that regression is significant, it does not mean that the slope of the regression line li an accurate prediction of the corrosion rate. The ratio should be at least 4 or 5 to consider the slope to be a useful predictor of the corrosion rate fRof.

001/0004.19

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 20 of 454 3.5, pp. 93, 129-133). A ratio of 4 or 5 means that the variation from the mean duo to rogre.oion in approximately twice the standard deviation of the residuals of the regression.

To have a high degree of confidence in the predicted corrosion rate, the ratio should be at least 8 or 9 (Ref.

3.5, pp. 129-133).

4,10.3 Beat Estimate of Recent Corrogion Rate In most instances, four sets of measurements over a period of about one year do not provide a significant regression model which can be used to predict future thickneases.

However, a 1east squares fit of the four data points does provide a reasonable estimate of the recent corrosion rate. This information is particularly valuable for assessing the effectiveness of cathodic protection and the draining of the sand bed region. Since a linear regression analysis performs a linear least squares fit of the data, the best estimate of the recent corrosion rate is the elope from the regression analysis for the period of interest.

These values are tabulated as the "Apparent Corrosion Rate" in paragraph 2.5.

001/0004.20

Calc. No. C-1302-187-5300-012 Rev. No. 0 Page 21 of 454 5.0 CaRLCUTOdS 5.1 6*x6" Grids in Sand Bed Raaion WIth Cathodic Protection 5.1.1 BAy Inh 5.1.1.1 Bav_ 11: 5/1/87 tQ 21BI90 Nine 49-point data sets wore available for this bay covering 4/24/90 period. Since a plug lies within this region, four of the points wore voided in each data set. The data ware analyzed as described in paragraphs 4.4, 4.S.1 and 4.6.1.

(1) The data are normally distributed.

(23 The regresseon modal ls appropriate.

(3) The regression model explains 78.3% of the variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thLckness +/- standard error is 870.4 +/- 5.7 mils.

(6) The corrosion rate +/- standard error is

-15.6 +/- 2.9 mile per year.

(7) J/F critical w 5.4.

(8) The measurement below 800 mils was tested and determnned not to be statistically different from tha mean thickness.

5.1.1.2 Bay 12A: 10/8188 to 4124190 Five 49-point data sets were available for this bay covering this period.

(1) The data are normally distributed.

(2) The mean model is more appropriate than the regression model.

(3) The 9-test for the significant of the difference between the means shows that the difference between the mean thickness are not significant.

001/0004.21

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 22 of 454 (4) The t-toot of the last two data sets eholde that the difference between the mean thickness in not significant.

(5) The current thickness based on the mean model is 878.9 +/- S.9 mile.

(6) These analyses indicate that the corrosion rate with cathodic protection is not significant compared to random variations in the measurements.

(7) The beot estimate of the corrosion rate during the period based on a least aquaria fit is -16.2 + 8.6 mil9 per year.

5.1.2 Bay 11C 5.1.2.1 Bay llc: S,1/87 to 4/24/90 Nine 49-point data sets were available for this bay covering this poriod. The initial analysis of this data indicated that the data are not normally distributed. The lack of normality was tentatively attributed to minimal corrosiOn in the upper half of the 6"x6" grid with more extensive corrosion in the lower half of the grid. To test this hypothesis, each data sot wag divided into two subsets, with one containing the top three rows and the other containing the bottom four rows.

Too 3 Rowe (1) The data are normally distributed.

(2) The regression model is appropriate.

(3) The regression model explains 79% of the total variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness + standard error is 977.0 +/- 12.5 mile.

(6) The corrosion rate is -3S.2 +/- 6.8 mile por year.

(7) F/F critical - 4.6.

001/0004.22

Calc. No. C-1302-187-5300-)11 Rev. No. 0 Page 23 of 454 Bottom 4 Rows (1) Seven of the nine data eets are normally distributed. The other two are skewed toward the thinner side of the mean. The Chi-uquare test shows that they are close to being normally distributed at the 1%

level of significance.

(2) The regression model is appropriate.

(3) The regression model explains 80% of the total variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness +/- standard error is 865.0 +/- 7.8 mile.

(6) The corrosion rate + standard error is

-22.4 +/- 4.3 mile per year.

(7) F/F critical - 4.9 S.1.2.2 B ay l1C: 10/8/88 to 4/24/90 rive 49-point data sets were available for this period. These data were divided into two subsets as described above.

TOR 3 Rows (1) The data are normally distributed.

(2) The mean model is more appropriate than the regression model.

(3) The F-test for the significance of the difference between the means shows that the differences between the mean thicknesses are not significant.

(4) The t-teot of the last two data sets shows that there is no statistical difference between their means.

(5) These analyses indicate that the current corrosion rate with cathodic protection Is not significant compared to random variations in the measurements.

001/0004.23

Calc. No. C-1302-167-5300-011 Rev., No. 0 Page 24 of 454 (6) Based on the mean model, the current thickneos +/- standard error in 996.6 +

0.3 mile.

(7) The best estimate of corroolon rate during this period based on a least squares fit in -25.0 +/- 10.6 mile par year.

Bottom 4 Rows (1) Four of the five data note are normally distributed. (So 5.1.2.1 above).

(2) The mean model ls more appropriate than thq regression model.

(3) The F-test for the significance of the difference between the means shown that the differences between the mean thicknesses are significant.

(43 The t-test of the last two data sets shows that there in no significant atatistLcal difference between their means.

(5) Based on the mean model, the current thicknceas +/- standard error in 878.1 +/-

5.6 mllo.

(6) Based upon examination of the distribution of the five data set mean values, it in concluded that the current corrosion rate is not significant compared to random variations in the measurements. The measurements alternated as follows: 897, 877, 891, 869, 863. Therefore the difference must be due to variations other than corrosion.

(7) The bent estimate of the corrosion rate during this period based an a least squares fit is -16.7 +/- 7.1 mle per year.

001/0C04.24

Cal. No. C-1302-187-5300-oll Rev. No. 0 Page 25 of 454 5.1.3 Bay 17D 5.1.3.1 Bay 17D: 2/17/87 to 4/24/90 Ton 49-point data sets were available for this period. Since a plug lies within this region, four of the points were voided in each data set. Point 24 in the 2/8/90 data wae voided oince it is characteriatic of the plug thickness.

(1) The data aro normally distributed.

(2) The regression model is appropriate.

(3) The regressLon model explains 95% of the total variation about the mean.

(4) The residuals are normally distributed.

(S) The current mean thickness +/- standard error Lo 829.5 + 4.0 mils.

(6) The corrosion rate + standard error is

-25.0 +/- 2.0 mils per year.

(7) F/F critical - 29.4 (8) The measurements below 800 mile were tested and determined not to be statistically different from the mean thicknesu.

5.1.3.2 Bay 17Dt 1012/88 to 4/24/90 Five 49-point data nete were available for this period.

(1) The data are normally distributed.

(2) The regression model iL more appropriate than the mean model.

(3) The regression model explains 90% of the variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness +/- standard error is 830.1 + 3.8 mile.

001/C004.25

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 26 of 4S4 (6) The corrosion rate +/- standard error is

-23.7 +/- 4.6 mpy.

(7) P/F critical - 2.7 5.1.4 Bay 19 5.1.4.1 say 19A:, 2/17/87 to 4/24/90 Ten 49-point data sets were available for thia period. Since a plug lies within thi, region, four of the points wore voided In each data get.

(1) The data are normally distributed at the 1I level of significance.

(2) The regression model is appropriate (3) The regression model explains 96% of the total variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness +/- standard error is 807.6 +/- 3.0 mile.

(6) The corrosion rate +/- standard error is

-21.4 +/- 1.5 mpy.

(7) F/F critical - 39.5 (8) The data points that were below 800 mile were tested and determined not to be statistically different from the mean thickness.

5.1.44.2 Rav l9qk lO/A/A8 to 4/24190 Five 49-point data nets were available for this period.

(1) The data are normally distributed.

(2) The regression model is more appropriate than the mean model.

001/0004.26

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 27 of 454 (3) The regression model explains 90% of the variation about the moan.

(4) The residual. are normally distributed,.

(5) The current mean thickness +/- standard error is 808.2 + 3.2 mile.

(6) The corrosion rate + standard error Le

-20.6 +/- 3.9 mpy.

(7) FJF critical - 2.8 5.1.5 8aY 198 5.1.5.1 My 19R: 5/1/81 to 4/24/90 Nine 49-point data sets were available for this period.

(1) The data are normally distributed.

(2) The regression model in appropriate.

(3) The rgreossuon model explains 94% of the total variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness + standard error le 836.9 +/- 3.2 mile.

(6) The corrosion rate + standard error is

-19.0 + 1.7 mpy.

(7) F/F critical = 22.3 (8) The measurements below 800 mile were tested and determined not to be statistically different from the mean thickness.

5.1.5.2 Dav 198, 1018/18 to 4/24/90 rive 49-point data sets were available for this period.

(1) The data are normally distributed.

(2) The regression model is more appropriate than the mean model.

001/0004.27

I 9 Calc. No. C-1302-187-5300-)ll Rev. No. 0 Page 28 of 454 (3) The regression model explains 75% of tho variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness +/- standard error is 841.2 +/- 3.3 mile.

(6) The corrosion rate + standard error is

-11.8 + 3.9 mpy.

(7) F/F critical - 0.9 5.1.6 Bay 19C 5.1.6.1 Bay 12C: 5/1/87 to 4/24/90 Nine 49-point data note were available for this period. since a plug lies within this region, four of the points were voided in each data get.

(1) The data are normally distributed at the 1t level of scgnificance, but appears to be developing two peaks.

(2) The regression model is appropriate.

(3) The regression model explains 98% of the total variation about the mean.

(4) The residuals are normally distributed.

(S) The current mean thickness +/- standard error is 825.1 + 2.3 mils.

(6) The corrosion rate +/- otandard error is

-24.3 +/- 1.3 mpy.

(7) F/F critical c 66.2 (8) The measurements below 800 mile were teoted and determined not to be statistically different from the mean thickness.

001/D004.28

I I Calc. No. C-1302-187-5300-011 Rev. NO. 0 Page 29 of 454 5.1.6.2 Bay 19C: 10/8/88 to 4/24/90 Five 49-point data eote were available for this period.

(1) The data are normally distributed at tha 1i level of significance.

(2) The F-teot for significance of regression indicates that the regression model in appropriate.

(3) The regression model explain. 93% of thie total variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness +/- standard error is 826.3 +/- 2.9 mile.

(6) The corrosion rate +/- standard error is

-21.5 + 3.5 mpy.

(6) F/F critical - 3.7.

5.1.7 Bays 17/19 Frame Cutout 12/30/88 to 4/24/90 Two sets of 6"x6" grid measurements were taken in Decemier 1988. The upper one is located 25" below the top of the, high curb and the other below the floor. There is no pxevious data. The upper location was added to the lonc; term monitoring program.

Five 49-point data sets were available for this period.

These data were analyzed as described in 4.4, 4.5.2 and 4.6.1. The initial analysis of this data indicated thal:

the first and last data oats are not normally distributed.

The lack of normality was tentatively attributed to moro extensive corrosion in the upper half of the grid than lhe bottom half. To tent this hypothesis, each data set wais divided into two subsets, with one containing the top three rows and the other containing the bottom four rows.

001/C0004.29

I.

Calc. NO. C-1302-187-5300-011 Rev. NO. 0 Page 30 of 454 Top 3 ROw$

(1) Four of the five subsets are normally distributed at the 1% level of significance but one is not.

(2) The mean model is appropriate.

(3) The F-teat for the significance of the difference between the means shows that the differences between the mean thicknesses are not significant at Is level of significance.

(4) These analyses indicate that the corrosion rate is not significant compared to the random variation, in the measurements.

(5) Based on the mean model, the current thickness +/-

standard error is 986.0 +/- 4.7 mils.

(6) The best estimate of the corrosion rate during this period based on a least squares fit is -8.2 + 10.7 mile per year.

Bottom 4 Rows (1) Four of the five subsets are normally distributed at the 5% level of significance, and one at the 1I level of significance.

(2) The mean model is appropriate.

(3) The F-test for the significance of the difference between the means shows that the differences between the mean thicknesses are not tignif icant at 1% level of significance.

(4) These analyses indicate that the corrosion rate is not significant compared to the random variations i the measurements.

(5) Based on the mean model, the current thickness +

standard error is 1005.7 +/- 5.6 mile.

(6) The best estimate of the corrosion rate during this period based on a least squares fit is -13.1 +/- 11.6 mils per year.

001/0004A.1

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 31 of 454 5.2 6wx6' Grids in Sand Bed Reaion Without Cathodic Protection 5.2.1 Bay 9Dt 12/19/88 t2 4/24/90 Five 49-point data sets were available for this period.

(1) The data are normally distributed.

(2) The mean model in more appropriate than the regression model.

(3) The current mean thickness ia 1021.7 + 8.9 mile.

(4) The P-test for the significance of the difference between the mean thicknesses indicates that the differences between the means are significant. The LSD analysis shows that this in due to the second measurement on 6/26/89 which is 33 to 52.3 mile higher than the other four.

(5) The t-teot of the last two data sets shows that the difference between the mean thickneesom io not significant.

(6) The overall analysis indicates that there was no significant corrosion from December 19, 1988 to April 24, 1990.

(7) The beet estimate of the corrosion rate during this

.period based on a least squares fit is -21.0 +/- 15.1 mile per year.

5.2.2 Bay 13^ 12/17/88 to 4124/90 Seven 49-point data osts were available for this period.

(1) The data are normally distributed.

(2) The regression model is appropriate.

(3) The regression model explains 97% of the total variation about the mean.

(4) The residuals are normally distributed.

(5) The current mean thickness + standard error is 853.1

+/- 2.4 mile.

001/0004A.2

1. I '.

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 32 of 454 (6) The indicated corrosion rate + standard error is

-39.1 +/- 3.4 mile per year.

(7) F/P critical - 16.9 (8) The measurements below 800 mile were tested and determined not to be 5tatLstically different from the mean thicknoss.

5.2.3 Bay 130D 3/28/90 to 4/25/90 One 7-point data set and one 49-point data set are available for this bay covering thip period.

(1) The 7-point data set is normally distributed at St level of significance. The 49-point data aet is normally distributed at 1% level of significance.

However, there lu a diagonal line of demarcation separating a zone of minimal corrosion at the top from a corroded zone at the bottom. Thus, corrosion has occurred at this location.

(2) The mean of the 7-point data set la not significantly different from the mean of the corresponding 7 points in the 49-point data set.

(3) The Current means thickness in 931.9 +/- 22.6 miLe.

It in concluded that corroeion has occurred at this location. However, with minimal data over a one-month period, it is impossible to determine the current corrosion rate.

5.2.4 Bay 1SD: 12/17/88 to 4/24/90 Five 49-point data sets were available for this period.

(1) The data are normally distributed.

(2) The mean model is more appropriate than the regression model.

(3) The current mean thickness I standard error io 1056.5

+/- 2.3 mile.

(4) The F-teat for the vignificance of the difference between the mean thicknesses indicates that the differences between the mean. are not aignificant.

001/0004A.3

4'.

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 33 of 454 (5) The t-test of the last two data oets shows that the difference between the mean thicknes**o in not significant.

(6) There wan no significant corrosion from December 17, 1988 to April 24, 1990.

(7) The beot estimate of the corrosion rate during this period based on a least squares fit -t -4.6 mil1 per year.

5.2.5 BaY 17A: 12/117/88 to 4/24/90 Five 49-point data set. were available for this period.

The initial analysis of this data indicated that the data are not normally distributed. The lack of normality was tentatively attributed to minimal corrosion in the upper half of the 6"x6 grid with more extensive corrosion in the lower half of the grid. To test this hypothesis, each data set was divided into two subsets, with one containing the top three rows and the other containing the bottom fout rows.

Too 3 Rows (1) The data are normally distributed.

(2) The mean model is more appropriate than the regression model.

(3) The current mean thickness +/- standard error is 1128.3

+/- 2.2 mil.

(4) The F-test for the significance of the difference between the mean thicknesses indicates the differences between the means are not significant.

(5) The t-test of the last two data sets indicates that the difference between the mean thicknesses is not significant.

(6) There was no significant corrosion during this period.

(7) The best estimate of the corrosion rate during this period based on a least squares fit is -6.8 + 3.7 mils per year.

001/0004A.4

Calc. No. C-1302-187-5300-011 Rev. NO. 0 Page 34 of 454 Bottom 4 Rows (1) The data are normally distributed.

(2) The mean model is more appropriate than the regression model.

(3) The current mean thickness +/- standard error 950.83 t 5.3 mile.

(4) The F-test for the significance of the difference between the mean thicknesses indicates that the differences between the moans are not significant.

(5) The t-teat of the last two data sets indicates that.

the difference between the mean thicknesses is not significant.

(6) There was no significant corrosion during this period.

(7) The best estimate of the corrosion rate durLng thifs period based on a least squares fit is -17.7 +/- 7.6 mile per year.

5.3 6"x6" Grids at 51' Elevation 5.3.1 Bay 5 Area D-1 2 51' Elevation; 1111187 to 4/24/90 Eight 49-point data sets wore available for this period.

The initial analysis of this data indicated that the data are not normally distributed. These data sets names start with E. The followLng adjustments were made to the data:

(1) Point 29 in the 9/13/89 data is much greater than ehe preceding or succeeding measurements. Therefore, this reading was dropped from the analysis.

(2) Point 9 la a significant pLt. Therefore, It was dropped from the overall analysis and is evaluated separately.

(3) Pointe 13 and 25 are extremely variable and are located adjacent to the plug which was removed from this grid. They were also dropped from the analysLs.

(4) Point 43 in the 11/01/87 data is much less than any succeeding measurement. Therefore, this reading wais dropped from the analysis.

001/0004A.5

. . I .

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 35 of 454 With these adjustments, the first and last data sets ario normally distributed at the 1% level of significance ant the other five at 5t. These data set names start with ?.

It was noted that the D-Moter calibration at 0.750, yielded readings which ranged from -1 mll for one set of measurements to + 4 mile for another. The data was adjusted to eliminate these biases. These data set namias start with G. The final analyses are based on these adjusted data sets.

(1) The data are normally distributed.

(2) The regression model ii appropriate.

(3) The regression model explains 57% of the total variation about the mean.

(4) The residuals are normally distributed.

(S) The current mean thickness +/- standard error ls 74!'.2

+ 2.1 mile.

(6) The indicated corrosion rate +/- standard error is -4.6

+/- 1.6 mil per year.

(7) F/F critical a 1.3. Thus, the regression is just barely significant.

(8) The F-test for significance of the difference betw'een the mean thickness indicates that the differences are significant.

(9) The t-tent of the last two data sets shows that tFhe difference between the mean thickness is not significant.

(10) The measurements of the pit at point 9 were 706, 146, 696, 694, 700, 688, 699 and 689 mils. The mean value of these measurements is 702.3 +/- 6.5 mile. A leaat squares fit shows that the beat estimate of the corrosion rate during this period is -11.5 milo per year with R2 -31%. The second measurement is much higher than the others. Dropping this point, the mean of the remaining measurements is 696.0 +/- 2.4 mile, and the best estimate of the corrosion rate is

-4.9 mill per year with R2

• 49%. Recognizing that the variability of single measurements will be abcut 6 times the variability of the mean of 40 measure-ments, it is concluded that the corrosion rate in the pit is ensentially the same as the overall grid.

001/0004A. 6

9 Ca1c. No. C-1302-187-5300-011 Rev. No. 0 Page 36 of 454 5.3.2 Bay 5 Area 61-5 at 51' Elevation: 3/31190 to 4/25/90 Two 49-point data sets are available for this time period.

(1) The data are not normally distributed. This is due to a large corroded patch near the center of the grid, and several small patches on the periphery.

When the data less than the grand mean were segregated, it was found that theme subsets are normally distributed.

(2) The t-testu of the two complete data oets and the two subsets indicate that the difference between the mean thicknesses are not significant.

(3) The current mean thickness + standard error is 745.1

+ 3.2 mile.

It is concluded that corrosion has occurred at this location. However, with minimal data over such a brief period, it is impossible to determine the current corrosion rate.

5.3.3 Bay 13 Area 31 Elevation 51': 3/31/90 to 4/26/90 Two 49-point data sate are available for this time period.

(1) The data are to normally distributed. This is due to a large corroded patch at the left edge of the grid.

When the data loss than the grand mean were segregated, it was found that these subsets are normally diutributed.

(2) The t-test of the two complete data sets indicate that the difference between the means is statistically significant. However, the difference between the means of the two subsets is not statistically significant.

(3) The current mean thickness is +/- standard error is 750.8 +/- 11.5 mile.

It is concluded that corrosion has occurred at this location. However, with minimal data over such a brief period, it is impossible to determine the current corrosion rate.

001/50O04A.7

Calc. No. C-1302-187-5300-0l1 Rev. No. 0 Page 37 of 454 5.3.4 Bay 15 area 23 E1Evatiozi S1't 3/31/90 to 4/25/90 Two 49-paint data gets are available for this time period.

(1) The data are not normally distributed. This is due to a large corroded patch.

When the data leso than the grand mean were segregated, lt waa found that these two subsets are normally distributed.

(2) The t-tests of the two complete data sets and the two subsets indicate that the differences between the mean thicknesses are not significant.

(3) The current mean thickness t standard error is 751.2 t 3.5 mull.

It io concluded that corrosion ha. occurred at this location. However, with minimal data over such a brief period, it La Impossible to determine the current corrosion rate.

5.4 6" x 6" Grids At 52' Elevation 5.4.1 Say 7 area 25 elevatlon S2V 4/26/90 one 49-point data set is available.

(1)  %.The data are not normally distributed.

The subset of the data lose than the mean thickness is not normally distributed.

When four points below 700 mile were dropped from the data not, the remaining data was found to be normally distributed. Therefore, the lack of normality of the complete data set in attributed to those thinner points. Three of theme could be considered to be pito (626, 657 and 676 mile) since they deviate from the mean by more than 3 sigma.

(2) The cutrant mean thickness +/- standard is 715.5 +/- 2.9 mile.

It is concluded that corrosion has occurred at this location.

001/Co04A.8

. 0 '.. .

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 38 of 454 5.4.2 Bay 13 Area 6 Elevation 52: 4/26/90 One 49-point data oat is available.

(1) The data are not normally distributed.

The subset of the data loos than the mean thicknesi is normally distributed. Thus, the lack of normalLty of the complete data set is attributed to a large corroded patch at the left side of the grid.

(2) The current mean thickness +/- standard error is 724.9

+/- 2.9 mile.

(3) It is concluded that corrosion has occurred at thio location.

5.4.3 Bay 13 -Aga 32 ElevatLon 52': 4/26/90 One 49-point data oat is available.

(1) The data are not normally distributed.

The subset of the data less than the mean thicknesia in normally distributed. Thus, the lack of normality of the complete data set lo attributed to these corrouion patches.

(2) The current mean thickness + standard error in 698.3

• 5.0 mile.

It is concluded that corrosion ham occurred at this location.

5.4.4 Bay 19 Area 13 Elevation 52' 4/126/90 One 49-polnt data met is available.

(1) The data are normally distributed. However, two adjacent points differ from the mean by 3 sigma and 5 sigma. Thus, there is a pit.

(2) The current means thickness +/- standard error is 71:2.5

+ 3.1 mils.

it lo concluded that some corrosion has occurred at this location.

001/0004A. 9

- -- I Cale. No. C-1302-187-5300-011 Rev. No. 0 Page 39 of 454 5.5 6" x 6" Grids at 87' Elevation 5.5.1 Bay 9 87- Elevation: 11/6/87 to 3/28/90 Five 49-point data sets were available for this period.

(1) The data are normally distributed.

(2) The mean model is more appropriate than the regression model.

(3) Ther- was no significant corrosion during this period.

(4) The current mean thickness +/- standard error li 619.9

+/- 0.6 mil.

(5) The best estimate of the corrosion rats during this period based on a least squares fit is -0.2 +/- 0.9 milu per year.

5.5.2 Bav 13 87' Elevation: 11/10/87 to 3/28/90 Five 49-point data sets were available for this period.

(1) The data are normally distributed.

(2) The mean model is more appropriate than the regression model.

(13 There was no significant corrosion during this period.

(4) The current mean thickness +/- standard error La 636.5

+ 0.8 mile.

(5) The beat estimate of the corrosion rate during this period based on a least squares fit is zero mils per year.

5.5.3 Bay 15 87' Zlevation: 11/10/87 to 3/28/90 Five 49-point data sets were available for this period.

(1) The data are normally distributed.

(2) The mean model in more appropriate than the regression model.

001/0004A.10

Calc. No. C-1302-187-5300-011 Rev. No. 0 Page 40 of 454 (3) There was no significant corrosion during this period.

(4) The current mean thickness + standard error is 63,.2

+/- 1.1 milo.

(5) The beat estimate of the corrosion rate during this period based on a least square. fit is zero mile pir year.

001,'0004A.11

Cabc. No. C-1302-187-5300-011 Rev. No. 0 Page 41 of 454 6.0 ArPMNICHO 6.1 SPSAMES Programs 6.2 SAS Program 6.3 Computer calculations OOl/DO04A.12

• I E.I2Nuclear TDR No . 1027 Revision No. I Budget Technical Data Report Activity No. 402950 l Page 1 of .IL Pro j ct I Department/Section ZKGINERINC i DESIIN_

OYSTER CREEX DRYWELL CORROSION Release Date Revision Date Doi:ument

Title:

DESIGN OF A UT INSPECTION PLAN FOR THE DRYWELL CONTAZINMENT USING STATISTICAL INFERENCE METHODS Or.iginator Signature Date Approval(s) Signature Date SJ.P.

p.LEOEO F d_ _ 4 ApprovAl for External Vietribution Djtf Doll$ this TDR include recommendation(s)? _Yeo %No If yes, TFWR/TRI _-

• Distribution Abstracts A. R. taig B&C4CCROUND:

F. P. Barbieri An a result of drywall corrosion at Oyster Creek, B. D. Elam, Jr. Ultrasonic Test (ut) thickness measurements are J. C. Flynn periodically being taken. In the past these measure-J. P. Moore, Jr. ments have been utilized to identify locations whose H. A. Orski thickness is reduced. By repeated measurements in D. 0. Slear these areas at the same location, statistically derivod P. Tamburro corrosion rates have been determined. A now UT inspection plan whosS purpose was to provide a basis for statistical inference that the drywell thickness satisfieo minimum required wan developed. The drywel:L is statistically characterized using a limited number of plate thickness measurements. The purpose of this TDR is to document the basis for this inspection plan.

11 (For Additional Space use Side 2)

This is a report of work conducted by an individual(s) for use by CPU Nuclear Corporation. Neither CPU Nuclear Corporation nor the authors of the report warrant that the report is complete or accurate. Nothing contained in the report establishes company policy or constitutel a commitment by GPU Nuclear Corporation.

• Xbstract Only

, Abstract Continuation TDR No._ 1027_ RevisLOn No. I

• Abstract ContinuatiOn TD NO. 1027 Usting 6" x 6" grids for UT measurementu, randomly choose 60 loctaion- but do not include sand bed grids. Finding no unsatisfactory areas in remaining observations in the basil to conclude, with a 5% riok of error, that 9S% of the drywell is free of such areas. A different sample is used each time that the aooeooment ia made. Finding no repairable areas within grids provideo a level of assurance of better than 99% that the drywell La free of ovich areas. Apply statistical inference methods as far as possible and where there are limitations une a judgement approach in order to determini3 whether corrosion ia or is not occurring.

la

NuclzrTDR 1027 iTnIE DESIGN OF A UT INSPECTION PLAN FOR THE DRYWELL CONTAINXMNT USING STATISTICAL INFERENCI METHODS ____ .,_

REV

SUMMARY

OF CHANGE APPROVALI C'ATE

1. Add to both Background and Solution sections that there are limits to statistical inference which are overcome by judgement methods.

2. Change derived to estimated.

3. Change Reference in text.

4. Add section for References.

S. Clarify Table 1.

6. Explain simulation notation and practice and number of units sampled.

7, Use Figure lb for section distribution oqual to 0.05.

8. Define utratification.

9. Use sand bad plates instead of sand bed when describing stratification.

10. Use estimate instead of failure and clarify multiple trials.

11. Add a statement showing that simulatLons demonstrate both accuracy and sensitivity of inspection plan.

12. Introduce insignificant change when uuing acutal number of plates per strata.

13. Add section addressing finding one or more unacceptable observation., Including Figure 3.

14. Add statements to clarify approach to local low areas.

15. Correct equations for variance.

16. Add section an dispoeition oa results.

N0036 (03.90)

LD

TDR 1027 RQv. 1 Page 2 of 38 TABL! OF COWTNTS RMI Background 3 Solution 3 Technical Approach 4 Simulation of Stratified sampling 7 Accuracy of Random Sampling by Simulations 7 More Complicated sim'lations and Recommended Sampling Plan 9 rinding One or More Unacceptable Observations 13 I

Use Of Calls Within Grids 13 Scope of Application 19 Acceptance Criteria 19 Sampling Scheme Contingency Plan 20 Dispouition of RWsults 20 Refxoences I

21 Attachmont IA: Simulation of Five Part Stratified Samplini; Plan 25 Ba Additional Simulation ot rive Part Stratif.Led 31 Sampling Plan : Sand Bad Zone Excluded 34 : Non-Stratilfied Sampling 37 012/0179 .4

TDR 1027 Rev. 1 Page 3 of 38 Bjfc ROUND:

As a result of drywell corrosion at OystQr Creek, ultrasonic Test (UT) thickness measurements are periodically being taken. In the past theos measurements have been utilized to identify locations whos. thickneus is reduced. By repeated measurements in these areas at the same location, statistically estimabed corrosion rates have been determined. A now UT inspection plan whose purposo was to provide a basis for statistical inference that the drywsll thickness satisfies minimum required was developed. The drywall is statistically characterized using a limited number of plate thickness measurements. The purpose of this TDR is to document the basis for this inspection plan.

SOLUSL Using 6" X 6" grids for UT measurements, randomly choose 60 locations of a possible 60,000 but do not include sand bed grids. Finding no unsatisfactory areas in remaining observations io the basis to conclude, with a 5% risk of error, that 95% of the drywall is free of such areas. Therefore, this sampling plan will develop 95S confidence that 95% of the drywell is free of such areas. A different sample is used each time that the assessment is made. Finding no repairable areao within grids provides a level of assurance t of better than 99% that the drywall is free of auch areas. Apply statistical inference methods as far as possible and where there are limitations use a judgement approach in order to determine whether corrosion is or is not occurring.

012/079.5

T3R 1027 Rev. I Page 4 of 38 Tl2'CC APPACH:

A nor.-parametric statistical approach using attribute sampling that assumes no prior knowledge of the distribution of corrosion above the sand bed region li the basis for the augmented inspection plan. The acceptance criteria is that the sean and local thicknesses of the shell equals or exceeds a required miniium thickness plus a corrosion allowance necessary in order to reach the next inspection.

statistically, a predicted value, Au, of the maximum number of defects in the population, N, reflecting a selected level of risk can be used so that fcr 0

this value *aa defects in sample "n" are expected at a low probability,C u.

The lower the probability, the larger the sample size. If a" or leas are found, then the selected rink is not exceeded. If *>a" are found, the selected risk is exceeded. Sample size "no can be computed given Au and

• For 5% of the surface an unacceptably degraded for Au, then "nn Is found to be S9 atO(u - 0.05 and a - 0. That ls, no observations which do not satisfy the acceptance criteria (I.e., grids) can be found in a sample of 59 with a 5% risk that the actual number of grids which would not satisfy the acceptance criteria exceeds Au without rejecting the hypothesis. Using 60 grids, there is only a 5% chance of finding no grids whose thickness in below the acceptance criteria given 5 of the population below this thickness.

Finding none in a sample of 60 in remote so that if none are found below this thickness, then the assumption about the defective proportion below the acceptance criteria thickness is probably an overestimate. Sixty 012/079.6

TDR 1027 Rev. 1 Page S of 38 observations is a good basis for a sampling plan. There is also the poalsbility that the actual number of defoctLve grLds ie less than AU and the hypothesis is rejected due to chance alone. This in evaluated in the dLocuasion of finding one or more unacceptable observations (oae bolow). Thio detenmination of the appropriate sample size li expressed formally byt a.

Pr (L, n-i) I(AU, N-AU)

i. O 0

(A Ca) x ((N-Ah) 0 (n-a)) / MCn 'i4u (Ref. 1)

Where N Cn in the number of combinations of n units chosen from N, N Ca Nl nl (N-n)l Results as shown in Table 1 For at sample size n = 59 observations, it is evident from Table 1, that the probability for finding zero unsatisfactory observations is 0.0482, which is lens than the assumed value of 0.05. Therefore, finding no occurrences in 59 observations satisfies the selected level of risk with only a 05 probability of error.

It lo also evident from Table 1 that for a sample size n - 124 that the cumulative probability of finding up to two occurrences of failures, which lo the sium of all three row entries, also satisfies 05. Xi, for this larger sample only one occurrence ls observed, then this is the basis to conclude that the actual number of occurrences in the population is less than the asswned value. Furthermore, finding no occurrences is even more evidence of this.

TDR 1027 Rov. .

Page 6 of 38 TASBL 1 PROBAILIT OF OCCU1RENgIS N a 60,000 NUMBER OF OCCUPRENCES SAMPLE S12K 0 1 2 2 -----

58 0.0508 0.156 .234 59 0.0482 0.15 .230 123 0 0.0116 0.0374 124 0 0.0111 0.0361 0121039.8

I.4 TDR 1027 Rev. 1 Page 7 of 38 Uating this same method, it can be shown that for 10% of the total surface areon as tho0 selected risk, the sample size is reduced to 29 at a S% risk. At n , 61), the risk is only 21.

The rtaults in Table 1, the work of Mr. J. P. Moore of GPUN; have been independently verified by Dr. D. G. Harlow, Associate Professor of Mechanics, Deparl:ment of Mechanical Engineering and Mechanlcs, Lehigh University.

Simulition of Stratified Samolinat The wtcst eavere corrosion has occurred in the sand bad region. This region may n'ot always contain the most service lLmLtLng location, however, because of as-nupplied local thickness. The previous measurement locations in this region will not be abandoned an part of this program since these are necessar' in order to determine corrosion rate. It is appropriate to deliberately proportion the new observation locations in order to limit the total number of randorm grids that can fall in any one region. For purposes of assessing the perfo2?mance of a random sampling, simulations will be performed.

Accuricv of Rando= Samoling Evaluated by Simulations:

A Strntified sampling plan has been simulated by Professor Harlow. In Figure la, a total of 100 panels Is used to represent the total number of plates usel to fabricate the drywell. Consider the drywell divided into two strata without bias as to proportion of occurrences when the acceptance criteria lo not mrit, the sand bed region and everywhere else. Ten plates, which are not necesisarlly contiguous, represent the lower strata, Including portions of 012/0-79.9

TOR 1027 Rev. 1 Page 8 of 38 those plates which may be under the drywoll floor and 90 comprise the upper strata. It in assumed that as much as five percent of the entire population does not meet the acceptance criterla. Asumtinq an equal probability of theoe observations in each otrata (0.05), the actual proportion, P1, arrived at by simply counting the randomly simulated defective units in both strata la, P1 - lb) 0.04833. The sample of the simulation in accomplished by randomly observing 15 units in the first stratum and 4S from the second stratum of a total of 60 observations, representing a one percent sample of available units. The measured characteristics are recorded as 1 if the unit does not mset the thickness criterion and as 0 otherwioo. The estimated proportion pl, for sampling without replacement, in 0.047, a slight underestimate.

The simulation shown that the sampling plan is very promising. Figure lb uses the same assumptions and proportion as for the first section distribution l (0.05). The only difference is that a different random selection of 60 observations was made. The bottom line, however, changed. The overall estimated strata proportion, pl has declined to 0.02. The simulation of the sampling plan no longer accurately reflects the reference proportions. A sampling plan is judged on satisfying this criteria. Repeated sampling using different grids each time will resolve this problem. The simulation studies show that the estimated proportions are more or lose accurate depending on random selection of observations only. Based on the simulations it would be incorrect to conclude, using a single sample, that the overall risk assumpticn is not violated or that it in violated because of random selection. A number of selections of different samples will consistently provide a good estimate 012/079.10

TDR 1027 Rev. I Page 9 of 38 of th- actual number of defects in the population on average. A good, experimental design uses a different sample euch time an estLmate is .mde. 1:t is proposed for this program that a different sample, each of the same size, be umed each time an estimate of the defective proportion needs to be made 8t) that the conclusion in not based on chance alone.

Finding no unacceptable occurrences after a number of repotitions of the sampling plan, using different samples, ia evidence that the assumed risk is not exceeded. A single finding of no unacceptable occurrences is consistent with the assumed risk.

Simulations of larger populations with the sample assumed risk at the same probability for error show the same good overall performance, but with like sensitivity to random variation.

MORE CO1pLICATED SIMULA=IONS AND ]RCOMMENDED SAMPLING PLANM A five part stratified random sampling plan ls proposed in order to make the moot of 60 grids. The five strata represent five zones of the drywell (Figure 2). Stratification divides a heterogeneous population into oubpopulation, each of which is internally homogeneous. Each strata ls sampled at the same portion, considering plates, as for the total population of plates. Better precision should be obtained than by ignoring the differences in the population. Plates in each zone will be randomly selectecl with one grld selected randomly per plate. The simulation of this scheme Ls 012/079.11

TOR 1027 Rev. 1 Page 10 of 38 included in Attachment 1, Part A. The stratification Lo based on relative proportions using existing qualitative knowledg- of both material lost due to corrosion and rate of material lost. The sampling plan ls summarized as follows:

NUMBER oF PLATES SAMPIXD Q 1 GRID PER PIATIh FROM TOTAL NUMBER OF DESCgIPTrON PLATES PR STRATA (ESTIMATEDI I intersection of 3 14) sand bed plates and drip zones I1 Drip zone 12 III Sand bed plates 9 IV All elso 32 V Cylinder 4 The sampling plan simulation shown satisfactory accuracy over 25 trials. No single estimate exceeding 5 is reason to reject the assumed level of risk. A l.

single sample may be unrepresented due to chance alone. A different random sample is used *ach time this assessment in made. , Part Be is an additional simulation of the same five part stratified sampling plan whore 100 repeated random samplings of size 60 are considered. In this simulation the performance of sampling process is characterized by forming a distribution of the estimation results. At the 901l confidence limit, the estimate of defect proportion falls between 0.096 and 0.0037. This shows the risk, due to chance, that the structure is concluded to be unsatisfactory where, in fact, it is.

012/079.12

, I TDR 1027 Rev. 1 Page 11 of 38 Using a one-aided t-scor*, an appropriate measure of the distribution of the estimates about the true mean, at - O.OS, the performance of the sampling process does not exceed 0.05, 95% of the time. Thil verifies the utility of the stratified sampling plan.

The confidence interval can be narrowed by increasing the proportion of the surface area that in scanned by UT. Using the grid location as a center, use of the A-scan on a best effort basis, will provide this process improvement.

The A-Scan device need only be set to the local minimum thickness as a threshold.

The sand bed condition with respect to material lost due to corrosion has already been characterized. About 67% of the sand bed zone perimeter has been.

surveyed by UT. By thin mean*, the most severely corroded zones have been iden-tified throughout the sand bed, including that portion below the drywell floor.

Attachment 2 is an additional simulation of the name five part stratified sampling plan, except that sand bed zone grids are excluded, if they are randomly selected. The saving of inspection time and exposure, the amount depending on chance for each sample, is justified by comparing mean estimates and standard deviations for 100 trials. Assuming 5 defective, the simulation including the cand bed zone grids as they are selected, shown a mean estimate of 0.046 with a standard deviation of 0.024 while the simulation excluding thc sand t*4 zone grids as they are selected shows a mean estimate of 0.044 and standard deviation equal to 0.026 (using proportion P1 for comparison).

012/O09.13

TDR 1027 Rev. 1 Page 12 of 38 Also, using the t-Dcore, as described above, this sampling process does not exceel 0.048, 95% of the time. By comparison, this is slightly lear accurate.

simulation of non-otratified sampling in shown in Attachment 3. This sampling plan does not use the accumulated corrosion information. Thlo simulation shows that by ignoring what in already known about the degree of corrosion, the sampling process accuracy is reduced because of the increased standard deviation. The mean estimate is 0.047, but the standard deviation has increased to 0.030.

Also, using the t-scoro as above, the upper 95% confidence limit, U 9 5 , in 0.052. This is slightly inaccurate, but in a nonconservatlv, direction.

Table 2 ouimmarizes the results of the simulation..

Simulktion also show. that the random sampling plans are not only acceptably accurste but acceptably sensitive, as well. Simulation shows that'finding no unacceptable observations occurs less than 5s of the time, as intended.

ChangLng the simulation in Attachment lb to reflect the actual number of plates per strata resolte in U9 5 - 0.055. The change is insignificant so that the estimate. used In the above simulations are representative of the performance of the random sampling process.

012/079.14

TDR 1027 Rev. 1 Page 13 of 38

[indl rcone or Mori U3nacceotabl- poervationa:

in the simulations, finding one or more of the 60 obsorvations to be leso than the minPimum thickness predominated. Finding one or more using thin sample doesn't prove anything unique and conclusive about the level of structural asourarnce. For example, one or more unacceptable observations can occur at a 5S probability with 99.9% of the drywell free of unacceptable observations. A concluuion about drywell, structural adequacy with one such observation li not approprlate because a better condition can result in an unacceptable observation. Finding none does confirm the orlginal hypothesis.

The prcbabilities of fLnding none (ec ) or flndlng one or more unacceptable observationh using a sample of 60 observations for a number of populations containing different portions of unacceptable observations arm shown In Figure 3. The probability of finding ond or more, I, ir t tl -O)

Uoe of Celig Within GrLds:

Minimuni required mean plato thickness and minimum required local plate thicknese each must satisfy deuign basis stress criteria. In addition, minimum required mean plate thickness must satisfy ASMt design basis stability criteria to prevent buckling. Minimum required mean plate thickness pertain.

to a shell course and minimum required local plate thickness pertains to a single local area or the sum of local areas within reference distances, if there axe more than one local area.

012/07SI.15

1' TDR 1027 Rev. 1 Page 14 of 38 TABLE 2 RESULTS OP MTMULATIONf 5% DEFECTIVE Pl P2 MEAN STANDARD MEAN STAND3JR ESTIMATE DEVIATION u95 ESTIMATE DEVITI'ON 9 I Five patt stratification 0.046 0.024 0.050 0.052 0.022 including sand bed Flve part stratification 0.044 0.026 0.048 0.043 0.0 6 not including sand bed No stratification, not 0.047 0 030 0.052 including sand bed

______________________________________ I___________________ £ 1 .. 9 _________________ I ___________

N0T5s By simulation it can b- shown that the mean estimate is ls. accurate for an assured 10% dofective population using a sample size of - 30.

012/0C19 16

1.0 -_ - - - - - - -i -- -_ s ^

4

• -* zero bad A-A at least one bad 0.8

-i A A

4t! 0.6 I -

0-

- ~At 0 Al

.rtl N - 60,000 CQ 0.4 n = 60

%A1

• 1 1 0.2 IL . 1 . 1

-A f% Ft U.I I A

_ * *

• He _

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 -k20 0.20 o -J F1t. 3 Fraction of BAD Grids w w

TDR 1027 Rev. 1 Page 16 of 38 A grict of individual moasurements will be the basis for estimating the mean plate thickness. There is no code requirement for either the minimum or maximtm grid size necessary to determine mean plate thickness. However, the grid siize should be large enough to capture the local, minimum thickness in a 2.5" diameter or smaller circle and no larger than 2.5iRt, which is the distance that uniform shell thickness must extend around an unreinforced opening. Local minimum thickness must satisfy both local membrane stress ctiteria and code rules for unreinforced openings.

The grid size should be large enough to contain enough single observations to miniml.ze the impact otfa pit on the mean thickness while minimizing radiation exposure of personnel taking the measurements. A 60 X 6" grid of 49 data pointti on two inch centers fulfills these criteria. It conservatively captures a 2" diameter circle and is more conservative than a 2.SVRt radius circle since there In less benefit from averaging. The 6" X 6" grids will also be used to establish that not more than 0.1% of the surface area satisfying the required mean thickness criteria contains locally low areas. That is, no more than ons locally low area per reference circle. Therefore, equate the requirement that 99% ol! the area in freo of holes to a 99% probability of finding no locally low area.

AnalynAis of variance of 20 X 2" cells contained within a single 6" X 6" grid will ohow whether the difference between the required mean and local thickness is significantly more than the lower 99.9% tolerance limit one-sided, times the standard deviation for the 2" X 2" Cells. The one percent probability li consristent with the one percent local reduction permitted by the code.

012/0'?9.18

TDR 1027

.ov. I Page 17 of 38 Statiastical inference regarding the variance of the observed grid means about the ti.-ue grid moan of the population is not important. The concern here in variance of reference 2" X 2" call measuremonts about an assumed mean equaL t3 the acceptance thickness for a particular plate.

As developed by Mesers. J. P. Moore and H. A. Oroki of GPUN* with review and concurrence by Dr. J. Orsini, Professor of Hanageomant and System Design, Fordham University, the pooled variance of 49 call measuraentx per grid, the average of four points per 2" X 2" cell, taken over 60 grid*, totalling 540 observations, in the basi8 to establish the lower, single-aided tolerance limit for a single cell thickness.

The dutinition of X2 , the parameter characterizing a normal distribution, relatue sample variance, S2, and population variance, C 2:

x2 , S2 (n - EQUATION I Where n - sample size - 540 and

2. (ni - l) 2

'S2.M 1 , rcor j v 540 and nL - 4 for all i

- 1) jul Where

_ X)2 2S L -(x ) where j - 4 (3 --l) 012/0'19.19

TOR 1027 Rev. I Page 18 of 38 Since n in large, C 2 can be computed accurately using X2 at a significance equal to CA1.

Hare the mean plate thickness io assumed and a tolerance limit in necessary to predict an individual observation. Yor a normal distribution of a large number of individual observations, the difference between the population mean, ,A , and an individual observation, x, is given by the Z parameter, Z a EQUATION 2 C is obtained from Equation 1, above. The difference - is the diffeence, t, between the aosumed population mean and a local thickness of

/ I

_01 7H4AIU b _._. j ,3~lCA14.

_4- _

an individual cell. it in highly unlikely for a local cell thickness to be less than:

Ix .. /A& - 99 *'C XQUATION 3 The distribution of results should ohow that the probability of an unacceptable local low area Ls vary small.

012/079.20

TDR 1027 Rev. 1 Page 19 of 38 uming pooled variance, an individual coll thickness is estimated at the lower 99.9% confideAnC limit. Based on the distribution of local thicknesses, there in a high confidence that no repairable local areas will be found, i.e., that the critical differences are more than that shown by the measurements, (A crit. C A 99 9) as shown in rigure 4.

ScOPE OF APLICATIOMI Since no portion of the drywall is purposely excluded on theoretical grounds, the inspection plan applies to the entire structure except welds, those areas over which a 6" X 6" simply won't fit, and penetrations.

Grids drawn at random falling In the sand bed tegion of the sphere will be disregarded because this zone is characterized in an ongoing manner by numercus grids and strip measurements. Previous measurements below the drywell floor in excavated trenches, showed that material loas due to corrosion was no worse than above the floor. This result. in ALRA savings without sacrifice in sampling accuracy.

ACCE ANCE CRITERUA:

A repairable grid is one that does not satisfy the local low spot minimum thickness. The 6" X 60 grid is a conservative gauge that could have been larger. its utility is for corrosion rate assessment. Larger grids tend to drive the mean thickness upward. The use of pooled variance of grids with the 012/O0'9.21

TDR 1027 Rev. 1 Page 20 of 38 refrtance mean thickness ensure* that the local minimum thickness is obtained conoeovatively. Finding no repairable areas within grids provides a level of asuurance of better than 99% that the drywell is free of such arose.

The corrosion allowance can be based on the estimated corrosion rate because nothing can be inferred about rate by this assessment. It is not appropriate to uno a 95% confidence interval rate estimate based on other, routinely revlsi.ted grids.

Smgjl.nq Scheme Contingency Plan:

shouldc a randomly selected grid turn out to be inaccessible, consistont rules will tie provided, in the Inspection specification, to locate an alternate withou.t introducing any biases.

D1soo2ition of Results:

Findin.g an unacceptable mean thickness is reason to better characteri.e the area in order to show that the region is, in general, in much better condition. If a mean thickness, established uoing a 6" x 6" grid, does not meet atinimum requirements, enlarge the inspection grid to an area one and a half feet oa a side and obtain additional readings. use the enlarged grid to compute a new mean thickness. Thin will improve accuracy, as well.

012/0-9.22

TDR 1027 Rev. I Page 2. of 38

1. Peraonal, cormunication entitled 3"ampling Plans for the Oyater Creek DI-ywolll 0. G. Harlow to S. D. Leshnoff, 5/22/90.

012/079.23

TDR 1027 Rov. I Page 22 of 38 TIX number n, 0 SICT:ON5. I.O. stra. 1S 2.

WNr11 74 numb.er -2!PANELS !I stra t,,

!N71? 7.-7 -. Tr ?;,;I;S 'IN 3trtum

-'£*:E

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1 2 .34i34 PIOPOMON Pi 0.04833333333 PROPORTION P2 0.049 PROPORTION P3 0.050'3333333 KNUR1 THE MUMME ni Of SAMPLIS DIRSIRID FOR stratum i INT1R THE NUMBIR n2 Of SAMPLIS DEStIED !ai stratum 2 45

-HT11 Tl total number .* Of UNITS TO SAMPLED.

as, 60.

sampling without replacement ISTl1ATt STRATA PRPORTZONS pi a 0,08666666667 0.04444444444 ISTIMATEI STRATA PROPORTIONS p2 a 0.06666666667 0.04444744444 ESTIMATID STRATA PROPORTIONS p3 z 0.1333333333 0.02252222222 PSTIO0ATlD PROPORTION pi z 0.04466666667 ISTIMAT[D PROPORTION P2 a 0..04666666667 ISTIMATID PROPORTION P3 x 0.033i333333 LSTIMATID VARIAMCE 01 p1 A 7.9872644S51'4 ISTIMATID VARIAMCE Of1pa 7.9872644931R4 ISTIMATED VARIANCE Of PI a 4.63016O4911 F(6.HI& Sl~UL~4nO'N OFPRANDO"'l SAM4PLl146i n)l'4i ?VWC SratAO a 012/079.24

TDR 1027 Rev. 1 Page 23 of 38

.wt mymber ni :Of SIM" ^"S. :.#. j'raia. '-1 2.

!MT!? tu "nmber 'IT  : 5 t.,m1.

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M4 WlMltR n2 Ot SAMPLIS DESIRED FOR stratum 2 ZN'!

INT11 asn 45 0:

M1total nuabr Of UNITS TO I1 SAMPLID.

60 sawlinng Vitbut replacement ISMATED STATA PRlOPORTIONS p1

• 0 0.02222222222 tStIIATE STIATA PROPORTIONS p2

• 0.4666666667 0 ESUMATED STIATA IIOPORTIONS F3 a 0.4i66666667 0 ESTIMATED FOPOITION P1 a 0.02 STfMATID PROPORTION P2 m0.04666666667 tSI!'ftD PIOPORtIOW p3

• 0.04666666667 15TISMTO V*WlIAS Of P1 a 3.$7923696r14 IThMAW VARIANC O OFfI a 1.630475751r4 ISTIMAT!3 VADIANCt 0o r3 1. 6w4?5575t4 FIg. ./b SfMWLArvAt of R4#vboA 012/C079 .2s SA PLJj& ust(At rvo s MM -.

I TOR 1027 Rea. 1 Page 24 of 38 DRYWELL

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012/079.26

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3Its ArT?AM'-e4T' £3.

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• 1 *:tii~ :I2:

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i"Si£ D:iT!:3'j0N no. 21 0.3924646792 0.019/S9293564 0.03924646792

• .01'565i18713 7.849293364t-3 PRCPdPl~tN iS : 0.0%1Z5 flaPcRTloN P2 1 0.0501 TNT NU?191 Of PANILS TO It SAMlFLID tOl sublets I - S

• 3,12,9,32,4.

sampling without replacement HTIMATU STICA'a PIOPOITIOS p1 a 0 0.l66666666? 0.11Ati11S 0 0 ISTISATD STIATA PROPORTIONS P2

• 0 0 Q.AII1titil 0 0 IS'TIMATD PIMtItION pi a 0.05 ISTIMATID PRUFtiltON pt

• O.0t666666667 IStIIAID VAlRINCZ 0 pi a 7.092326223'4 ISTIMATEM 'JARIC of Pr

• 2.46694077t14

,it t1UMI1R 0 IPANIS TO it SAMP[TD 101 subsets £ - 5 a 3,12,9.32,4.

sampling without replauement tISIMATID STRATA PIOORTIONS pt

• 0 0,00333333333 0 0.03125 0 1STIMATD STRAMAA IoPVMON PI . 0 0.00333333333 0 0 0 ISTIMAMD PRON1l1TION * '003291(%667 ISTISATID ?ROPIRTION pt2-.9.01I64466467 IST1IMAtUD U4IAIRNCE OfPtI a.09952 6771M tSTItATtO VAIIANCK 0f P

• 2.54396199714 Tnt MIWUU1 01 1'AMKLS TO It S9APLIID 10 subsets I - 5 3,L2,9,32,4.

sampling without replacement tSTtIMA'f S¶A^,A 1100I31ONS Pi a 0.3333333333 0.08333333333 0.1111t11111 0 0 ISTt1A1Tg MTAIM POPORTIONS p2

• 0.6646666667 0 0.111111 0.03123 0 ISUMUD 3PRlAtTflO$" pi a 0.05 S:1MA"M PIvM;'ON !2 & 0*.'06615 012/079.27

A*4ad~D  % I.s uV P *.U J13*31 TDR 1027 Rev. I THt. NMUill Of PANt[L TO 3t SAPLZ tOZ sutsvol -- 2 3,12,9,32.4. Page 6 of 38 s5&pJlDP  ; witteut replamnt I

13SrVIATID ST1At4 P1aPaOTMONS pi

• 0.333i333333W 0i oiiio? 2.,03L23 0 I3t:eA.i 3TIATA ?R0P0171NS p2 x 0 0 0 0 ;

t:.~~~'-;.P Pt).o8w 0 .4i625

!' .:~7z~P 0PP70N p1 a

-.. :^.-;@!^HAYKI Ct Pi m l.03V'6i00l£'4 THZ NHMll1J1T PANILi tO St SA¶PLID JOI subsets I - I a 3.12.9,32,4.

II i

ampling without roplacement I I

fSTIMATUD STRATA PIOPOITIONS pI 0 0.25 0.11t11iiitt 0 0 i tSTIMATID STRATA PROPOITIONS P2 3 0.3333333333 0 Q 0.03125 0 II II ISTIMMATA PIOPORTION p1 a 0.06666666667 I 1STI.%TID PNOPORTION p2 a 0.03291666667 I I

ISTIMATID VANIANCI 0 p1 a S.7112LI127t1 I ISTIMATID VAlIANCE O p3 a 4.4061905521-4 I

I TH14NUMStZ Of PANtLS TO 11 SAMPLED oU subsets I - 5 3'3. 12,9,32,4.

I sampling without replaceoent Ii IMTMATP STRATA PROPORTIONS pt

• 0.3333333333 0.666666667 0.3333333333 0 0 I ISTIIATIP STRATA FlOPODTION1 i2

• 0.3331333333 0 0 0.03125 0 i I

ISTHATsD P10?03ORt0 p

• 0.1 I ISTIMATID PROPORTION P2

• 0.0329166666? I I

ISTIMATID V4114NCE O pi

• 1.2021461S903 I ISTIMATED VJAIANCI of p3 a 4.406130552-4 II TMI HUM1EI Of PANELS VII SMP 34O1 subsets I - 5

• 3,12.9,32,4.

i saapling Wittout zatlmamst I

ISTIMATIS STRATA PROPMt Oiw pi

• 0 0.1666666667 0 0 0 II II ISTIIATID STIATA PIOPORTIONS 13 a 0.6666666667 0.08333333333 0.1111111111 0.0312:; 0 ISTIMAT11 PIlCOlTION pi a 0.03333333333 Ii ISTIMATl PItCIPORTWI p2

• 0.01291I66667 RS?lIATtD VMlIAUCM 0 pi

• 4.623854491'4 ISIMAID VAIIIANCI Of PI a 9.417003321'4 Ii llt NU1IV2 Of PANEL3 TO SeSAMILI fOU sibsets L - 5 a 3.,2,t,34s*.

• , TDR 1027

• H,,  :.h PI 4 TN'Q 0).03333'137 3 Rov. 1 r:I:!M ?JCIORt;I1 s

• Page 27 of 38 tj::.7i; i:A.'M.3 10 Pt m * .345119W21-4

• ~ .~22a.I

. * ~rr I.

-*..5 *.-3[i :1 PZ:.g' 3L it I9LZo iFP subsis 1 -I 3,;2. '. 32.4.

3j..¶t. S ,iO'J0:  ?,pe e,ftnt

,,j- S--IATA PRC?0c.uNs tl

• 0 d ).2222222A2z *o Ii;T'-7) ;r3ATA PROPORTVONS P2 a 0A.ioc6 i7 .7 eC.) ).,5 ESihiTT ?2QPOIIONI T i 0.)66666666679 Itrrn ?C.R;TN ptZ *0)0i;ii IST:PATID VIIANCI of P1

• S.942331"999-4 KSTIMATED VARIANCE 01 p2 s 9.474i26931'4 THE NUM9e9 of PANELS TO I SAtPLED TOP subsets I - 5 v 3.12,9.3234.

sampling without replacent ESTIMATED SnATA PIOPORTIONS3t

• 0 0.1646666667 0 0 0 ESTIMATED STRATA PROPO2TIONS V2

• 0.3333333333 0 0 0 0 ESTIMATED PROPORTION p1 a 0.03333333333 ISTIMAlID PROPOSTION p2 a 0.0166666666?

ESTIMATED VARtANC1 Of Pt a 4,625335449r-4 ESTtMATtD VARIANCI 01 P2 1.8506165721-4 THE NUM11R O PANELS TO St SAMPLuP ?O0 sublets I - 5 a3,12.,32.4.

sampling without replacement tSTIMATED STIATA POPORTIONS pi x 0 0.03393333333 0 0 0 ISTIMATMD snATA PIOPORTIONS v2 a 0.6666646667 0.166666666? 0 0 0 ESTIMATED PIOPOETION *1 a O.Ol66444U7 ISTIMATD PIOPOITION S

• 0.0666"466C7 ESTIMATED VlIANC1 orPt a 2.54m199714 1SIMnATED VAlIANCI O?01 a 6.4760023at*4 THE NUtIK 01' 1AMILS TO it SAMPLES 1OU ubutst - I 3,i2,5,33,4.

saapling wittout replacesint STIMATES S?1VATA PiOPOStIONS pi a 0.3333233333 0.1666666667 0.22222222 0 0 tSTIMATED STIATA flOFOlTIINS I2 a 0.6666666667 0.00333333333 0 0.03125 0 ESTIMATED FRCIPOUIION It a 0.06333333333 ISTIMAMTE P(IONATION P2

• O.O62s3 ISTIMMT D V*RIANC1 OOi t t.U71MIMn3

SDR 1027 I

ISTMATHD S1RATA PROPORTIONS p1

• 0 0 0.11W11111+/- 0 0 Rev. 1 tS?'.tt.TI: !1"ATA H!MITIOS P2

• 0.6666566i7 0 0 0.031?1 0 Page 28 of 38 ISTIMAPTU !P0W!PTlOM Pi u 0.O1666466667 ISTIMATED PIOPORTION p3 a 0.0495033333)

ISTIMAMD VARIANCE Of Pt a 2.46694H07171'4  !

?StlIATID VARIANCE OF P2

• 4.40618055294 THl NUM81R 01 PANLS TO 31 SAMPL1D 101 xUbSots I - 5 ' 3.12.9,32,4.

sampling without roplacesent tSTIMATID STRATA PROPORTIONS tI a 0.6666666667 0.1666666667 0 0 0 UTIMATnD STRATA PMOIOtlIONS P2

• 0.6666666667 0.08333333333 0.11111111+/-

0.09375 0 ISTIMATID PROPORTION p1 a 0.06666666667 ISTIMATED PROPORTION p3

• 0.1154166667 ISTIMATID VAlIANCt 01 p1

• 6.476002321154 tSTIMATED VAl[AtNC Of P2

• i.4033515452'3 THt NUMBIR Of PANELS TO 11 SAMPLUD J01 subsets i - 5 3,12,9,32.4.

sampling without teplacowent ISTIMATID SIRATA PROPOSTIONS pi

• 0.3333333333 0,08333333333 0.2222222222 0 0 ISTIMATID ST1ATA PROPOITIONS t2

• 0 0.08333333333 0.1111i1t11 0.03125 0 tSTIMATtPDOPORTION p1

• 0.06666646667 ISTIMATED PI0PORTION p2

• 0.04S59333333 STIMATUD VARIANCI 0 Pi a .711725219E'4 MSIMATED VARIANCE Of PZ

• 1.566464481'4 ThE NUMER) Of PANELS TO It SAtLED 101 subsets I - 5

• 3,12,9.32.4.

sampling without replacement tSTtMATtD S12A!A PIOOZTIOWS pi a 0.3333333333 0.03333333333 0 9 C IS'IMA'E3 STRATA IROMfT10S pi

• 0 0.166666666'io.1 0 0 ISTIMATID PIIOPOITIO" pW-0,003233333333 iSImATID PIlOPORriON i3Pa.0.05 ESTIMATED VIRIAMr 01 p1

• 4*.394?89869E4 ESTIMATED V11i1ANCI OF p2 a 7.092326221'4 THI NMUMIU 0P ?ANILS TO 3 SAPLID Nt subsets 1

• s a 3.:2,9,32,4.

sampling Without roylacle nt ISTIMATED S';rlaA PROPOITIONS pi

• 0.1333i33333 C.1666666667 0.1111111 0 0 ISTiMATE STRATA PIROPORTION$S t2 0.3333333333 0.16666667 0 0 0 vTiMAltO v' icarrmN *4 . A ttc&4cc4

- - .. r -V ,wVI -. W Fv Y K s- ,, -x J w"J,.;AM J-t p, *(P. 4760023 C4 Il TDR 1027 Rev. 3.

-'* N

j?t.S IM It SAMM - r a . 4,.1. 4. Page 29 of 38 7 .: ?ROr's 4 Pza :3i: 33 32 3 AM ia

~ :.~.~Z .r p~ 3 Z i i ~7ii

-';Ino31 70 H 3! APLID FOR subsets L' I 3,11Z.5,212.4.

aIMP 1I;

ji.hut. replacen.nt vS6A'M

--  ?

iMTA 0PO'T:ONS pi 0 0.08333333233 '3 0 0 ISTIMATID STRVTA P1OPVROMOS pa x 0 0.25 0 0 0 ISTIM1ATIO P1001lT"014 pt

• 0.01~666666667 ISTIMAUt ?ROPORTIN ,: a* 0.0

• STIM 'A*IANC ; Of i 2 3.439619927'4 IST:,4ATtD VARLANCt Of p2 a 6.2442703361-4 THI HUMID Of PANILS TO It SAMPLID FIO subsets I - 5

• 34;12,9,.4.

sampling without relpacmofnt ISTIMATM STRATA PROPOTIONS Pt x 0 0.08333333333 0 0 0 ISTIIATID STRATA PROPOTITONS p2 a I 0 0 0 0 ISTIMATID PROPORTIN pi

• 0.01666666667 IStIrAUM PIOPOTtION pa a 0.05 ISTIMATfD VAIIANCI 0 p1 a 3,4396t971'4 fSTIlATID VARJANCZ Of p2

• 0 ti41 HUtilti 01 PAHtLS tOlT SU LD 101 subsets I - 5

• 3.12,9,32,4.

saAl ing wiithout ISTIMTAD STIATA MIOCOITtOUS pr* 0 0.0333333333 0 0 0 ISTIMATID STIATA POPOITIONS iI v 0 0.25 0 0.03125 0 9STtIAYD PICIPOITION tl a 0.0166666667 ISTSNTA PICIPOITIOtN P a 0.06A25 1STIIIATD VARIANCI 01 It

• 2.44396t0sM4 ISTIATIS VARIANCZ Of i2 8 O.799U34036t4 741 NUMI! 011 PANELS TO It SAt@ID f0a suhbsts I - 5 37,11,132,4.

sapxirs wvitout replacam nt

. I SDR 1027 Rev. 1 Pago 30 of 3B 2 0.0466666fil?

iSflP~T!D P!t2!nQH P

• A Tr^ Id.

gSTI.M.1m 9:IARACI Ofp

• a2.466940??14 ESTIMATIE VA1IUANC 0 P3

• 2.54396199794 Tlt HUMitl oIP PANELS TO it S4AL 7101 subsets I - 3

• 3,12,9.32,4.

shpling without replacement ISTIATKD STRATA PROPORTIONS it

• 0 0.25 0.2222222222 0 0 ESTIMATED STYATA PROPORTIONS p2 a 0.6666666667 0.08333333333 0 0.0623 0 ISTIMATtO ROPRC TION Pt 0.08333333333 ISTIATI PROIPORTlON II 0.0tZS ESTIMIATE VAlIANCE Of it a 1.05614167it3' ISTIMAM *AIJANCI O I2 a 9.340831153t14 THE MUM8IR 01' PANILS TO St SAMQLfl f01 subsets 1 - 5 a 3,12.9,32,4.

sampling without replacemnt ISTIMATID STIRATA 11OPORTIONS p1 a 0.4G666666?7 0.25 00 0 ISTIMATED STIATA PItOPOTIONS pi a 0.666i666667 0 O.1111111111 0 0 ESTIMATED PROPORTION pt

• 0.00333333333 19STIMA9AH PRlOYTION II a 0.05 ISTIMATID VAJlANCZ Of1

• 0.048072231'4 ISTIMATtD IVAlIANCE 0 2

• 4.3175576431'4 THE MUMR1 ofr PANELS TO it SAMPLIE fO subsets i - 5

• 3,t2,9,32,4.

samling without replacement ISTIATID STRATA PROPO3TIONS P1

• 0.3333333333 0.0B333333333 0.ltt1illti 0 0 ISTlt1AT RtATA ?IOO1IIONS P22 0.3333333333 0.1666666667 0 0 0 ISTl'ATlV PItOlT10%

• 0.05 ISTIMATED PROPORTION PI a 0.05 ISTIMATED VARIANCE Of p1

• S.115L944 ISTIMATED JARIANC[ of p3 a647T00131tt-4 012/079.32

O.'~

,e

..hE 1cuJ18 OF SJSE.S r,-e I~SETdrip zone and sandbed: ;OIST 1 TDR 1027 SUSSIT 2 = irip Zone only: VERY BAD Rev. I SUBSIT 3 :and bed' BAD Page 31 of 38 SUBSET 4 - :*est of the shere: QOOD SUBRST 5 - yloinder: DIST THE number 07 PANILS IN SUS6ETS 1,2,3,4,5 IS 5 20 i5 52 8 THE tot.l number 0T PANELS a too A rTA - HEN r 1II ASSUmt5 TOTAL NUMBIR 0 6X6 SAMPLE UNITS IS identical trl EACH ?ANSL. S PAF PAT THE pIUM1R1 10F jNIITS P° ?PANEL nu 600. 'IMtutr 0,000. FI~ c,~~"ArI C. 'vIJ THE tot3l number Of UNITS THE number ';IF UNITS 1t1SUBSETS l,2,3,4,5 IS 300 12000 90(60 3+/-200 4800 ENTE! R :ibar nv')? A SHACaCTRl2ATI^2H OF E14K7TIR! ?PDPLATION.

0:

0.05 SUBSET DIST11IBUTI=0N no. 1:

0. 224487529 0.1cc2243765 0.OE 31+/-21982 O.0C'OU489751

0. OC0504S975 SUBSET DISTitBUTION no. 2:

0,.324646732 0.-0 S492 3`6 O.03- 92464678 0.01 696597+/-

0.00C249M936 FPO?09TION P1 : 0.04735 PROPORTION r2 a 0.0515 Sampling without replacement THIt MUBUl -F PAtIELS TO BI SAMPLUD FOR gubsets i - 5 = 3,i2s9,32,4.

MAXIMUM OF SHK !STIMAT!S: 0.1i66666667 0.03726921082 1 1 0.1325 0.03469665474 1 i MINIMUM 0? SHI £STIMATISS 0 0 0 0 0 0 0 0 AVERA6 Of 1THE ISTIMaTES: 0.045925 0.02282403069 0.91 0.99 0.05165 0.022477759t? 0.88 0.98 STO DEY OF 1Ht ESTIMATES: 0.02409039543 7.30501659il-3 0.2876234913 0.1 0.029C0819482 9.3318281161r3 0.3265986324 0.1407052941 UPPEU TUO-S1IDt ;A01MAL 0.90 AHb 0.95 CONtI?)NCI LIMIT 0.09628466044 0.1051476805 LOWER TIJO-SIDED flORMAL 0.90 AND 0.95 COMFIDINCE LIMIT 3.7153395641'3 5.W14768009t-3 W1(hat) si(hat) TtST90 TEST95 72(hat) s2(hat) TtST90 TEST95 0.0333333 0.0209633 1 1 0.0829t67 0.0300526 1 1 0.0500000 0.0261837 I +/- 0.0162500 0.015996i I 1 0.0658333 0,0305628 1 1 0.0333333 0.0209633 1I 0.0333333 0.02+/-5067 1 l 0.0333333 0.0209633 1 1 0.0500000 0.0261945 1 I a.o9129W7 0.0306873 1 1 0.0000000 0.0000000 0 l 0.0662500 0.0300S26 1 I 0.0333333 0.0209633 1 1 0.0500000 0.0207797 1 1 0.0829167 0.0339088 1 1 0.1162500 0.0296645 0 0 0.0495833 0.0463631 1 1 0.0829167 0.0306873 1 1 0.1000000 0.0324990 0 1 0.0333333 0.0209633 1 1 0.0666667 0.0284515 1 1 0.1000000 0.0266314 0 1 0.0333333 0,0223S50 1 1 0.0662500 0.0300526 1 1 0.0166667 0.0:59498 1 1 0.0333333 0.0207787 l 1 0.40004n 5 0 1 0.0%00000 0.0281937 1 1 0.0G166667 0.0126037 1 1 0.0662500 0.026363+/- 1 '

eZ Z * * ::.-

. ::~ O37

c. :co 0.0;27222 I a TDR 1027 S.0254480  ! , . 0,S. 7. 0.0 1i3037 !1 Rev. 1 M0'0+/-548 1 0.022S921 1 Page 32 of 38

• 0.04159333 ' *:::

0.01i666 0.0i594973 I J. .. '*.0000 0.0209633  ! 4

0. 0500000 . 0261945 I i 0.049.5833 0.0^2.29909 1 :

II :i.0666667b 2,0225821 1 1 C. 024490 1 A 0.2233:333 ,0.C-@.0773? 1 0.013$037 ATT. ib,.

r, ,^,_c534 I 1_ 0.45.3333

.;,A S,,,';, t.2.0000000 0 1 1..26.1 1.

0.0324990 0 1 0.022t33504 0.0306873 1 1 O. v .1l 3 S 0.02.3 333 0.02+/-5067 0.1:254480 +/- I 0.0)33333 0.02077S7 1 0.0.829!67 0.0300526 i 1

.O. 03333::33 O.0136037 1 I.M263S31 1 1 0.0.363.33:

0.C.?'3 333 O. '2!5O67 +/- I0.0662500 O.0C300526  : I 0.0662!00 *).0J__>3C672 1 C-.0254460 1 0.0159961 1 1 0.MOM253 03.02636>31 1 0.03+/-061+/- 1 1 O.3CA 526 1 0 .06E66667

-0.0166667 0.i0o!4 58.31C.20 909 1 0.0159961  :  :

').0372622 0 0.027368.3 i 0.0+/-59499 : a 0.0495833 M.026363 1 0.0241885 1 Oa 223_50 . 2.

0d.0166667

),. 05C!C100C, I.026+/-937 *e 0.0262631 1 +/-

O. O ' S 656 0 0.0833333 0.0324990 +/- 1.

O.* 500000 1 0.01562500Q 0.02077e? 1 O.00C00o0 o a 0.01060(7 A.0254480 +/- 0.0272272 1 1 0.050000t 0207787 1 0.0i59861 A

• 0.0249825 1 0.0271895 1 1 0.A2 54480 I J .08S 000 0.0337969 1 1 I1 0.0+/-62500 0.00(00000 o.C.c.c.0000 0 O.Os19861 +/- 1.

a1 0.07290000 zO.O)66667O

0. M166667 0.02342i3i8 0 o 0.0i33333 0.0207777 i i 0.0254480 1 1. 1 0.0333500 0.0207787 1 1 0.0i62500 0.06i66.67 0.0299041 1 0.03429833 0.0224109 1 1 0.0166667 v0.01v5498 1 0.0000000 0 I 0.01i66617 0.0+/-36037 1 0.0159861 1 1 0..03":333 0.0209633 1 0.0223850 1 1 tO. vt~tZN; 33 O 0.0207787 1 2. 0.03000000 1 0.0333333 0.0207787 1 1

(). 0254480 1 1. 4 0.03333533 0.08333333 0.0263631 1 £ O.M66667 0.0295156 4 0.0261945 1 1 0.03:133333 0.020?633 1 41 0.0833333 0.0829167 0.0299048 1 1 0.0209633 1 4. 'MM16" 0.0209633 1 a

?.*0500000 0. 0254480 1 I 0.0 00000 0.0000000 0 I

0. 03(:O 0.025J4480 +/- i 0.0325000 0.0346967 0 0

'2.02+/-5067 I O.M159498 1 1 0.0Ci323333 0.0+/-36037 1 0 0.0833333 0.0136037 +/- 1 C. 0+/-i666i7 O.Q-!36037 1 1 0.0333333 0.0209633 ; 1 I,. .0166 6 i 67 0.0136037 1 0.03068173 i 1 0,0295!48 1 i 0.0500000 0.0254480 1 1 11 0.0333333 0.0626666 0 i.>@;V)Oo 0.0157r35  : 0.0304365 +/- 1

0. 0313333 0.0215067 1 1i 0O.0000000 0.0833333 0.0222402 1 1

03. 05('OC00 0.0207?77 0.0833333 1 1 0.0495833 0.0272272 a I OOMU5s a 1 0.0500000 0.0254480 1 1 0.0000000 0.0000000 O 0.0159498 a 1 0.016Co67 0.0157065 a 0.0159498 1 +/-

0.0$3'333 0.0324990 1 1 0.0833333 0.0209633 1 1

• .0500000 0.0261945 .1 0.0299048 1 1 0.026+/-945 1 0.0275072 1 1 0.0295333 1 0.0000000 0 1 A'XC'650000 0.015,065 1 0.0215067 ' 1 0.02!4480 1 0.03356G68 1 1 0.03:13333 0.0136037 1 +/- O.0166667 0.0157065 1 I

.%1i si355 .^ . I4 WA.7 4 Av v33333 A 01" A A

A I

TOR 1027 Rev. 1 Page 33 of 38

.ii3333i0 I I v.uAvIOJa 1 1 0.0^S§4 0.02,9949 1 I 0.4 1 . 16 i i 0.0662500 0.0300526 1 I 0.0000000 0.0000ooo 0 1 0.0333o332 ^.t9£33 ' +/- 0.0°99'S' 0.02133?? 0 +/-

0.066i667 0.0293156 1 1 0.0166667 0.0136037 1 1 a, 4'4 A 4Ot 4O8 2 I 0.0500000 0.020778? 4. +/-

0.5,00000 0.0266314 1 1 0.0929167 0.0335660 1 i 0.0500000 0.0209633 1 1 0.0638333 0.0260708 1 1 0.0495833 0.0262166 1 1 0.0495333 0.0209909 1 1 0.0995832 0.0362171 0 1 0.0662500 0.0300526 1 1 0,0666667 0.026453S t 1 0.0666667 0.015949S +/- 1 0.0333333 0.0223850 I 1 0.0658333 0.0260708 1 1 0.0500000 0.0266314 1 1 0.0325000 0.0222402 I 1 0.0500000 0.0207787 1 1 0.0495833 0.0267973 1 1 0.0333333 0.0207787 1 1 0.0333333 0.02078?7 1 t 0.0662500 0.0306873 1 1 0.062916? 0.0300526 1 1 0.0500000 0.0254400 1 1 0.0166667 0.0159490 1 1 0.0129167 0.0335660 1 1 0.0166667 0.0136037 1 1 0.0500000 0.0266314 1 1 0.0000000 0.0000000 0 1 01V2079.35

SU8SHT4S1IH THE HUH1IR 0? SUBSETS ns w 5.

%i8tVT l , drip Zone and findbedt WOOST TDR 1027

UDSIT 2

• drip iont onItI VINY BAD Rev. 1 SUIStS 3 sand dtl BAD Page 34 of 38 SUBSET 4 rest Of the spherel GOOD SUISIT 5

• c)linderI 038t THE number OF PANIL$ IN SUBSETS 1,2,3,4,5 IS 3 20 15 52 I ANTT 9 Mt total number Of PANILS a 100 48SUMthJ tOTAL NUME Of 6IRS SSAMPLE UNITS IS identical FOR IACH PANEL. SAND SCr) tXCLUCC!

14t HUHII DI UtilTS P11 YA~tL nu u 600.

nM # I YI UCtng1b l ,t3,4,S is 30 12000 90(X0 31200 4800 INTER q x Pr(bad unit'I A CHARACTtRIZATION C0T$N ENTIRI POPULATION.

GI 0.05 SUISCT DSTR13UTl0H no. It 0.2 24487529 0.1162243765 0.0 31O21982 o*01)05046973i 0.0)05048973 SUHSET DI8TRIUTION no. 21 0.3134646702 0.0 ?84929356 0.0:192464678 0.0156905871 0.0078492136 PIOPORTION J1

• 0.05015 11OPORTION 1i2

• 0.05103333333 sampling Vhtout reiplarsmnt THENHUIISER Of PANELS TO BE SAMPLED 101 subsets I 3,12,9,32,4.

THI BOTTOM HALT Of Tt PANELS IN subsets I AND 5 Alt KXCLUDID, IJ AND OIILY It THIY AEt RANDOMLY SILEFED.

CONDITIONAL PIOPOITION Pt

• 0.o4312962963

.COONITIONAL PROFORTlON r3 w 0.04191481481 MAXIMUN 0 THE ISTIMAT9B1 0.120313704 1 1 58 0.1226851853 1 1 MINIMLM 01 THE ESTIMATES1 0 0 0.49 0 0 0 AVU1AQ O '7IK UITIA71Ths 0.04425562L69 0.94 0.97 53.9 0,0434497354S 0.14 0.95 3?) D&V Of 'Ht HSTIMATE1 0.03582932443 0.2386132566 0.171446600 1.702642035

.O261563100893 0.2386832566 0.2190429136 MIPER TWO-831 NORMAL 0.90 AND 0.95 CONVIDENCE LIMIT fOl CASI i -

0.016172068?4 0.09453338650 LOUZE ThO-I0DI) NORMAL 0.90 AND 0.95 COHNIDENCt LIMIT 101 CASi I *

'1. 2809482931 '5 .3741276111'3 UPPER TNO-SIDtE NORMAL 0.90 AND 0.95 CONtIDtHeC LIMIT FOR CAS9 2 -

0.084)2373904 0.09246374318 LOUWK TWO-SIDID NORMAL 0.90 AND 0.95 CONFIDINCt LIMIT 100 CASt 2a

'.941072061'4 '.S9341t3551'3 11040t) TEST1 T129S no. sampled p2chat) IEST9O T1s959 0.0689815 1 1 54 0.0685105 I I 0.0365741 1 1 54 0.0185105 1 1 0,0365?41 1 i 35 0.0370370 1 1 0.0000000 I I 51 0,0180556 t 1 0.,043511 1 1 53 0.1,26853 0 0 0,0759251 1 1 53 0.0185185 1 1

0.0351852 l S 55 0.0685 85 .L

• I ,.0a77778 I TDR 1027 0.6995370

• 0 53 0.0462963 1 Rev. I l1 54 0.0921296 0 Page 35 of 38 0.0638809 1 1 St 0.0128704 1 0.0370370 I 156 M.0S777 I 0.0629630 $5)I 0.0277778 1 ATT, 2 0.0856481 L 52 0.077778 I 0.0000000 1 I 52 0.0736111 1 0.0736M1 1 1 50 0.0643519 1 0.0185185 .L 1 54 0.0370370 1 0.0324074 I. I 55 0.049074t 1 0.0509259 I1 55 0.0458333 1 040462963 1. I 54 0.0185185 I 0,0324074 1. 1 55 0.0361111 1 0.03935i9 1. I 53 0.03611il IL 0.0555556 1.. 1 55 0.0550926 1 0.01L5185 1. 1 54 0.0555536 1 0.0370370 2. 1 53 0.0643519 1 0.0370370 1. S 55 0.046a963 I 0.0138969 IL 1 56 0.0365741 1 0.0550921 " 1 54 0.0365741 1 0.0277776 'L 1 49 0.1009259 0 0.0648t8B .L 1 54 0.0377778 1 0.0416667 :L 1 52 0.0462963 1 0.0393519 'L 1 53 0.0638999 1 0.0000000 f1 54 0.0689815 1 0.031S9444 1 Il 55 0.055556 1 0.0319444 fL 1 56 0.0324074 I 0.0935926 11 52 0.0370370 1 0.0462963 1L1 54 0.1189911 0 0.0463963 f 1 53 0.0646140 1 0.0165185 i1 53 0.0324074 1 0.0324074 2. 1 55 0.016510 1 0.0370320 1 S.5T 0.066,815 1 0.0571704 i, 1 54 0.0324014 1 0.0643519 1. 1 54 0.0462963 1 0.0925$26 0 1 54 0.04513S3 1 0.0717393 IL 1 54 0.0504630 1 0.0740741 IL 1 54 0.02777 1 0,0370370 IL 1 53' 0.0731481 1 0.05$5536 IL 1 57 0.0185135 I 0.044148 IL 537 0.0601852 1 0.0092593 IL 1 54 0 .0 37777 I 0.0165165 IL I 51oo 3 1L 0.0324074 , LL .s rooil44lh22 I 0.0646146 0.0532407 I iI '. 1 Mu 0.0092593 0.0000000 0.067i29% :1 1 53 0.01LS519 I 0.0370370 1 1 53 0.013M 9 I 0.0555556 L 1 54 0.027771 1 0.0277778 I 1 55 0.0000000 1 0.0370370 1 1 56 0.0599206 Il 0.0740741 t 1 56 0.027777 1 0.0186185 1 1 55 0.0130009 1 0.02?7778 1 J 32 0.0133333 1 0.0555156 1 IL 54 0.0165165 I 0.0165165 I 1 54 0. 055556 I 0.0185165 1 1 54 0.0133333 1 0.0067176 IL I 55 0.0458333 1 0.0347222 1 1 S4 0.0)194 1 A 04 *9. 7 * . g' < A * . A A. \ ^ e. i

4 6

. 4 6*

TOR 1027 Rev. 1 Page 36 of 38

• I ¶4 1 'E.'

. Z+44

?:-444 0.0165185 1 1 53 O.O00000 ATh Z 0.0787037 1 55 0.1040296 0.0578704 1 1 54 0.031944 0.0370370 1 1 55 0.009a293 0.032407? 1 1 5? 0.041666?

0. 00630 1 3 56 0.0685185 0.016666? 1 1 54 0.0000000 0.0195185 1 1 53 0.0195165 0.0740741 1 1 5t 0.0435333 0.0165185 11 54 0.0000000 0.0462963 1 1 49 0.02777t 0.0537037 1 1 55 0.0370370 0.0509259 1 1 55 0.04027?8 0.0310370 1 1 52 0.0105105 0,0000000 1 1 55 0.0928704 0.0324074 1I 54 0.0324074 0.0000000 I 55 0.0000000 0.0555556 53 0.0615741 0.0310370 1I 34 0.0833333 0.0925926 52 0.0699015 0.0209352 I I St 0.0319444 0.0389889 55 0.0183195 0.0456333 01 54 0.0462S63 0.1203704 51 0. 016511!

0.0722221 1 1 34 0.045133) 0.0000000 53 0.0939801 0.0324074 54 0.0324074 0.00000000 I i 51 0.0462136 0.0555356 53 0.018911!

0.0509251 la 0.0000000 012/C179.38

TDR 102 7 Suwsbt Rov. 1 Assurnt TOTAL NUWIE9 Of 61: SAMLI UNITS IS identical J0O EACH PANEL. Page 37 of 38 7Tmmurmti 01 UhIS P1t PANtL nu a 600.

THE totul nultlbr o0 UNITS 60,000.

mrl q

• Prfb4d unit)$ A CHARACTflIZATIOM of THt WiTll 1OPULATI ON.

of A?7. 3 0.05 FIOPORTION Fl e 0.05061666667 NtM- S7AmAK' sampling Wittout replacement T~t IUMIRI Of PANELS, TO It SAMPLID IS 60.

THt BOTTOM HOLY 0 'T1 PANELS IN THt SAND 3LE(20 PANIL) Alt txCLUDLD. If AND ONLY IF THtY All RANDOMLY SILICT1D.

COtDITIO?4AL 1ROPOTION ?I a 0.05096296296 MAXIMUM OF Ti"? ISTIMATHSI 0.1346152346 t I 53 MINIMUM Cy TVI ISTIMTI81 0 0 0 44 AVtEAGt O0 't ISTIMATES: 0.0470419326 0.83 0.95 49.77 STn b1y Of 'WI ISTIMAISt 0.C03059222541 0.3773251631 0.2190429136 2.407291113 UPR TWO-Sill NORMAL 0.90 AND 0.93 CONVIDINCZ LIMIT 1`0 CAStI S 0.09675751304 0.1066109375 LOU1U TWO-SIll) NORMAL 0.90 AND 0.95 CONFIDENCE LIMIT FO CASE i w 4.256412883363 '4.6930115371t3 1l(hat) t18190 ?TS775 no. *aled 0.0000000 0 1 51 0.0196073 1 1 51 0.0576923 1 1 52 0.0212766 1 1 47 0.0000000 > 1 49 0.019607t 1 1 51 0.039215? L I 5I 0.0106379 1 1 53 0.0377352 1 I, 53 0.0000000 0 1 48 0.0196078 1 1 51 0.0200000 1 1 50 0.061224! L 1 49 0.0566031 1 £ 53 0.0408t13 1 1 49.

0,Q9S0^C92 " I 51 OIOcrOO l I 50.

0.0833331 L. 44*

0.34i154 .) 0 52g:

0.04091i3 L ' 49 0.0000000 0 1 32 0.042%532 1 1 47 0.06OO 1i 5C.

0.0425532 1 1 47 0.0334615 S S :2 0.0200333 1 48 0.0380235  :: 5L 0.01943i4 1 51 0.603W29  : ' 093 0.-10957 o 0 46 0.039461 -1 1 52 0.0392+/-57 L 1 54.

).703623 l 1 !2

- .. ' T4..'r@-w m-

, ';.0377359 i £ 53 TDR 1027 0.05761j3 : I 5* Rev. 1 0.0833333 +/- 1 48 Page 38 of 38

. 0800000 s. I 50

'2. 3400000 II +/- 0

• .*:3oo 11 47 i ^s390t l 47

• :il245 I ' 49 5.:4i" .; 48 4fl t

?.'-7'  :  : !1

+/- 3

.`34000.)06225I* 43

4.)3':4 I 1 4?

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'833333 I 40 0.0196070 I1 31 0.0566030 1i +/-

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0.0638296 I 1 47 0.C'42500Q 0I1 44

• .0566038 I 1 53 0.0764314 I.I St O.0t91632? I 1 49 0.1224490 0 0 49 0.02?273 0.0000000 I t12 £ '445 I'(000000 0.019473L 01 t-S 54t 41 O.C1600000 t * *0

@).COOOOOO O t: U 'K 0.C'O00000 01 4? . .

0.C'76923t1 1 52 0.-0196073 IS 51 0.0I222*2 1i1 45 0.-0434231 1 44 0.0201333 1 1 46 0.0400000 1 1 50 0.('118161 1 1 55

^.72:66 .

• 47

'?.+/-+/-II0 0 41 0.0316323 1 1 49 A A. i!904 41 47

. it.

.w.

.'I. 4__ _

-i %I IJ Nuclear SPECIFICATION IS-402950-o00_

NovciM& SWcrsy RCeLr"p INSTALLATION SPECIFICATION FOR OYSTER CREEK FUNCTIONAL REQUIREMENTS FOR AUGMKNTED DRYWELL INSPECTION PREPAIRAT W.^1 alwayp PatQr Tanlburro wAiv -

a DATE - i/3 /u ENGINIEERING APPROVAL ff-880Iqjal SAJ P HAL4L ATE j/'/eTb I GA CONCURRENCE- & 4 ,

DATE 6_

/____

a 0

REV. _

c Q.I -'__

A0000023 7-84

IS-402950-o01 Rev. 0 PA" 2 Of 23 nor CORTiNTs S1ETI<! WE 1.0 scotP 3

2.0 REFERENCES

3 3.0 REQUIREMENTS 5 4.0 QUALITY ASSURhXCE 13 5.0 NORKATION TO at SUBMITTED 13 6.0 EXHIBITS 1 AND 2 13 004/0040.2

IS-402950-001 Rev. O Page 3 of 23 1.0 8 This specification establishe. the minimum requirements for the augmentad ultrasonic tenting (examination) program of the Oyster Creek drywell containment vessel.

This specification requires UT examination of 57, 6" by 6" areas (grLds) randomly chosen from all drywell plates above the sandbed elevation.

Each 6" by 60 grid will be segmented into 9, 20 by 2" areas (cells).

Acceptance criteria for each grid will be dependent upon the average thickness of each 2' by 20 cell and the average of the 9 cell thicknesses.

it may be necessary to expand an inspection location to an 18" by 16" area which will be segmented into 81, 2" by 20 cells. Figure #1 presents a schematic of the inspection logic for each of the 57 inspection&

locations.

1.1 Ultrasonic teeting (UT) required by this specification is to be performed during refueling outage only.

1.2 All data shall be forwarded to Technical Functions for evaluation.

1.3 The inspections required by this specification are in addition to the inspections required by Reference 2.6. ROC shall coordinate all activities in the drywoll associated with this specification and reference 2.6.

2.0 RBEZRSM 2.1 ASME BtPv Code Section V, 1977 Edition through Addenda Summer, 1978.

2.2 AS)H Section V, 1986 diLtLon.

2.3 AS5E BSPV code Section XI, 1977 Edition through Addenda Summer, 1978.

2.4 SNT-TC-IA, 1980 Fdltion, NAmerLean Society of Non-destructive Testing, Racomewnded Practice."

2.5 TDR 1027, "Design of a UT Inspection Plan for the Drywell Containment Using Statistical Inference Methods."

2.6 GPUN Specification 1$-328227-004 "FunctLonal Drywall Requirements for Drywoll Containment Vessel Thickness Examination" (most recent revision).

004/0040.3

IS-40295 0 -001 Rev. 0 Page 4 cf 23 SPEC 402950-001 INSPECTION LOGIC Figure 1

SS-402950-001 Rev. 0 Page 5 of 23 2.7 CS! Company Drawings 9-0971, Sheets 1 through 92.

2.8 CPUN Sketches 33-SKK-339, Sheets 1 through 20.

2.9 OPUN Memo 5360-90-396, P. Tamburro to A. Baig 3.0 RZQUIRZK=S 3.1 Non-Destructive Examination.

3.1.1 Personnel Qualification 3.1.1.1 Ultrasonic personnel shall be qualified and certified as a level 2 MD2 Inspector in accordance with Reference 2.4.

3.1.2 Examination Equipment 3.1.2.1 Ultrasonic examination pulse-echo equipment cap-able of thickness measurement by the digital and/or A-scan on a CRT screen shall be utilized.

Digital readout equipment shall have printout capabilities and memory storage traceable to sequential readings.

3.1.2.2 Ultrasonic examination by use of robotic equipment may be performed; however, the performance of ultrasonic examination devices shall be in accordance with Sections 3.1.1.1 and 3.1.2.1. UT thickness examination through paint shall be performed per qualified techniques and procedures.

Qualification shall be performed to the satisfaction of the OPUN Manager of NWZ/5I1.

This qualification shall be documented.

3.1.3 Plate Number Scheme and Inspection Designation 3.1.3.1 To locate each insp ction location, a series of drywell plate drawings have been developed (Reference 2.8).

004/0040.5

, ' S-402950-001 Rev. 0 Page 6 of 23 Each inspection location will be numbered in tho following formats E - PM - GN whoreo:

N - Plate Elovation (6, 23, 50, and 71)

PM - Plate Number (par xhibit 11)

ON - Grid Number 3.1.3.2 Inspection locations have been randomly chosen and are listed in Section 3.1.5 and are shown in Reference 2.8.

3.1.4 Inspections shall consist of the following for each inspection point.

3.1.4.1 The random locations have been chosen based on Reference 2.5. The inspection point shall be located by measuring first from the horizontal weld and then from the vertical welds as shown on the sketches in Reference 2.8.

Due to ALARA considerations and the random nature of those inspection* it is not necessary to precisely verify the location of each inspection point. However, the robotic equipment operator or NDz Inspector shall ensure (the to best of their abilities) that each inspection point iL properly located per Section 3.1.5 and Reference 2.8.

It in recognized that not All the randomly chosen locations may be accesuible for inspection, or surface conditions may not allow for proper UT scan. In those instances, an alternate inspection location shall be chosen (as shown in Exhibit #2) with concurrence of Technical Functions.

3.1.4.2 6" by 6" Insiection 3.1.4.2.1 The UT Inspection shall be performed over a 6h :oy 6" area centered on each inspection point. Each 6" by 6* area (referred to as a "grid") shall bm divided into 9, 2" by 2" areas (referred to as "cells"). As shown in Figure 2A.

004/0040.6

'. S-402950-001 Rev. 0 Page 7 of 23 UT examination shall be performed in a manner which will result in a nominal thickness value for each 2" by 2" cell (for a total of 9 values).

3.2.4.2.2 Xf one or mcre cell thickness values are Laos than LTC (Section 3.1.4.4), then this grid shall be marked and results reported to Technical Functions as soon as reasonable (approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />). Additional inspections shall be determined following data evaluation.

If all 9 cell thickness values are greater than or equal to LTC then evaluate the data per Section 3.1.4.2.3.

Ficure 2A

_ - 2" 6" l cInspection Point 2" x 2" cells Grid 004/0040.7

IS-402950-001 Rev. 0 Page 8 of 23 rlcure 28 180 x 180 Orid I(- 18' a-1 1i eC- - Inspection I Point I < 2" x2*

4 _=_ _cal 3.1.4.2.3 If all 9 cell thickness values are greater than or equal to the MTC (Section 3.1.4.4), then no further inspections are required for this inspection point. Thickness values for all 9 cells shall be transmitted to Technical Functions (per Section 3.1.6.1).

If one or more of the 9 cell thicknesu values are less than the NTC, then data evaluation per Section 3.1.4.2.4 shall be performed.

3. 1. 4.2.4 The average of all 9 call thickness values shalL be calculated. If the average is greater than cor equal to thu HTC An the thickness value of all 9 calls is greater than or equal to the LTC, then no further inspections are required for this inspection point. Thickness data for the 9 cells shall be transmitted to Technical Functions (per section 3.1.61) 004/00(40 .8

IS-402950-001 Rev. 0 Page 9 of 23 If the average in less than MTC then an expanded inspection shall be perforued par Section 3.1.4.3.

3.1.4.3 18" by 18" Expanded Insoection 3.1.4.3.1 An 18" by 18" expanded inspection shall be performed on all inspection points which do not meet the criteria in Section 3.1.4.2. Technical Functions shall be notified (as soon an reasonable) of all inpection points which require an 18" by 18" expanded inspection.

3.1.4.3.2 The 18" by 18" area shall be centered about the original inspection point and the 6" by 6" grid (Section 3.1.4.2). If the 18" by 18" area cannot be properly centered due to penetrations, welds, or surface conditionu, the 18" by 18" area shall be placed and oriented in a manner in which the entire 18" by 18" area is located on the original vessel plate and overlaps the original 6" by 6" grid.

3.1.4.3 .3 The IS" by 18" area shall be divided into 81, 2" by 2- cells, as shown in Figure 2B.

UT examination shall be performed in a manner which will result in a nominal thickness value for each 2" by 2" eall (total of 81 values).

3. 1.4 3.4 If all 81 cell thickness values are greater than or equal to LTC Agd the average of the 81 cell thickness values Is greater than or equal to MTC then no further inspections are required for thisi inspection point. Thickness data for all 81 cells shallbe transmitted to Tech Functions.

If one or more cell thickness value(s) are less than LTC, then this expanded inspection area shall be marked, and results reported to Tech Functions as soon as reasonable (approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />).

004/0040.9

IS-402950-001 Rev. 0 Page 10 of 23 If the average of all 81 call thickness values ii less than mrC then results shall be reported to Technical Functions as soon as reasonable (approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />).

Thickness data for all 81 cells shall be transmitted to Technical Functions (par section 3.1.6.1).

3.1.4.4 Thicknes Critgria 3.1.4.4.1 (Reference 2.9)

The following Mean Thickness Criteria (MTC) shall be applied In Section 3.1.4.2 and 3.1.4.3s Noinal Doelivered Plate Evaluation Thb.kn=pg 211-3" to 23'-6" 1.154" .780*

23'-6" to 51' .77" *735u 51' to 65' .722" .695" 65' to 71'-6" 2.625" TBD 710-6" to 95' 0.64" 0.605*

3.1.4.4.2 (Roforence 2.9)

The following Local Thickness Criteria (LTC) shall be applied in Sections 341.4.2 and 3.1.4.3.

Nominal Delivered Plato Evaluation Thickness Lkm 11'-3w to 23'-6" 1.154" 5" 23'-6" to 51' .77' .5w Si' to 65' .722" .470" 65' to 71'-6" 2.625" TBD 71'-6" to 95' 0.64" 435" 3.1.4.5 UT thickness examination. through paint shall be performed per qualified techniques and procedures. Qualification shall be performed to the satisfaction of the OPUN Manager of NDE/ISS.

3.1.5 13R Xnsoections Locations For the 13R Outage, 57 inspection locations shall be examined (per Section 3.1.4). Theme locations shall be examined as follows:

004/0040.10

,. IS-402950-001 Rev. 0 Page 11 of 23 Distance Prom Distance From Center Line of Center Line of

'?late Plate Grid Vertical Weld Horizontal Weld Elevati1o aMM Numbe (Right/>fta -(Top/Bottom) 6' -10' to 23'-6' 6-7 99 Left 4'- 4' Top 2'- 10O 6'.-10' to 23' 6-10 42 Left 1'- Top 1'- 5" 6'-10w to 23'-60 6-12 149 Right 1'- 7W Top 5I- 5' 6'-10" to 23'-6' 6-13 185 Left O'- 5. Top 6'- 10" 6'-10" to 23'-6" 6-14 31 Right 5'- 2' TOp O'- 11' to 23'-6" 6-16 64 Left 2'- Top 1'- 11" 6'-10" to 23'-6" 6-18 155 Left O'- 5W TOp 5'- 11" 6-~10*1 88 Rlght 1'- 4" Top 2'- 2" 6'-10" to 23'-60 6-19 6'-10" to 23'-6" 6-20 196 Left O'- 10' Top 8'- 11I 23'-6" to 50'-11" 23-8 118 Left 3'- 1' Top 4'- 0' 23'-6' to 50'-11" 23-11 629 Left 6'- 8a Bottom 7'- Om 23'-6" to 50'-11" 23-15 726 Right 0'- 6" Bottom 1'- 6' 23'-6" to 50'-11" 23-17 368 Left 0'- 9' Top 12'- 0" 23'-6" to S0O-11i 23-19 494 Right 0' Bottom 12'- 0" 23'-6" to 50'-11" 23-20 190 Right 2'- 2' Top 11'- 6*

23'-6" to 50'-11" 23-21 256 Left 4'- 3" Top 11'- 6" 23'-6" to 50'-11" 23-22 311 Right 4'- 3' Top 12'- 6" 23'-6" to 50,-11l 23-23 22 Left 2'-11" Top 1'- 0" 23'-6` to 50'-110 23-24 216 Right 3'- 1i Top 6'- 6" Distance From Distance From center Line of Center Line of Plate Plate Grid Vertical Weld Horizontal Weld EUDvation Numbr Number , Maht/>~ftl (TD/Bott ml SI' -11" to 66'-2" 50-1 116 Loft 1'- 3' Bottom 8' - 110 50'-11" to 65'-2" 50-3 277 Left 3'- 7" Bottom 1' - 11 to 651-21 50-4 2 Left 1 '- 11" Top 7' - 11' sID -11, to 65'-2" 50-5 277 Right 2' Bottom - 11 50,I-il"1 50'-11" to 65'-2" 50-7 292 Left 3'- 8" BOttom 1' - 59 503'-119 to 65'-20 50-8 597 Left 3'-11" Bottom 2' - 5" 50'-11 ' to 65'-2" 50-10 442 Left 2'- 5s Bottom 6' - 5' S') ' -11" to 65'-2' 50-11 235 Left 3'- 3' Bottom 3' - S" to 6S'-2" 50-12 114 Right O'- 50 Top 2' - 11' to 65'-2" 50-13 85 Left 0'- 6' Top 7' - 11' 5DZ'-ll" to 65'-20 50-14 492 Left 1'- 5' Bottom 3' - 5" to 65'-2" 50-17 219 Left 1- 8" Bottom 3' - 11" 50 '-11" to 65'-2" 50-18 359 Left 1'- 5' Bottom 7' - 5" to 654-2" 50-1g 147 Right 1'- a" Bottom 7' - 5" to 65'-2" S0-21 190 Right 1'- 1 Bottom 4' - 5' 50'-11" to 65'-2' 50-22 236 Left 3'- 11' Top 6'- S" 004/0040.11

I

'. I

• IS-402950-001 Rev. 0 Paqg 12 of 23 Distance From Distance From Center Line of Center Line of Plate Plate Orid Vertical Weld Horizontal Weld Xlevation Number NUMbr (Left/Riohtl (Too/Bottoml 65'- 2" to 71'-6' 65-2 35 Right 0'- 6" Top 2' - 5" 65'- 2" to 71'-6" 65-S 49 Right 0'- 7" Top 3' - 5" 65'- 2" to 71'-6" 65-6 22 Left 0O- 6" Top 1' -11" 65'- 2" to 71'-6" 65-8 124 Right 0'- 6" BOttom 0" - 5" 65'- 2" to 71'-6" 65-10 124 Right 0'- 6" Bottom 0' - 5" 65'- 2" to 71'-6" 65-11 18 Right 2'- 0" Top 1' - 5" 65'- 2" to 71'-6" 65-13 95 Right 1'- 4" Bottom 1' -11" 65'- 2" to 71'-6' 65-14 112 Right 1 '-11" Bottom 0" -11" 65'- 2" to 71f-6" 65-16 8S Right 1'- 9" Bottom 2' - 5" 65'- 20 to 71'-6" 65-17 113 Right 1'- SW Bottom 0" -11" 65'- 2" tO 11#-6" 65-18 122 Right 1'- 5" Bottom 0" - 5" 65'- 2w to 71'-6" 65-20 99 Left 0"- 10" Bottom 1' - 5" 65'- 2" to 71'-6" 65-21 122 Right 1'- 5" Bottom 0" - 5" 65'- 2" to 71'-6' 65-22 27 Left 1'- 0" Top 1' -11" 65'- 2" 65-23 45 Right 2'- 1 a TOP 3' - 5" 65'- 2" 65-24 82 Left 1'- 3" Top 1' - 3" 65'- 2" 65-25 119 Left 1'- 11" Bottom 2' - 11" 65'- 2" 65-26 32 Right 2'- 0" Top 2' - 5" 71'- 6" to 83' 71-1 461 Left 4'- 6" Bottom 5' - 1W 71' -6" to 83' 71-4 920 Right 3'- 0" Bottom 0' - 7" 83' to 94' 83-1 482 Left 11'- 5" bottom 4' - 0" 83' to 94' 83-4 401 Left 1'- 11" Top 4' - 0" All Specific locations are ihown on Reference 2.8.

3.1.6 REcords 3.1,6.1 A1l data shall be rOcorded on data sheets which identify the Inspection location number (per Section 3.1.5.1) an shown in Reference 2.8. Data sheet format shall be consistent with Figures 2A

& 2B. Copies shall be transmitted to Technical Functions as noon an practical. Also, data shall be sont to Technical Function. on a floppy disk in an ASCII format.

004/C0040.12

' 1S-4029S0-001 Rev. 0 Page 13 of 23 3 *2 Euo2:prt Work 3.2.1 Work to be performed by the Refueling Outage Contractor (referred to as the ROC).

3.2.1.1 The ROC shall schedule and coordinate all activities necessary to perform the inspections.

3.2.1.2 When required, the ROC shall recet scaffolding.

4.0 QUALITY AS8URANCC 41.1 All work shall be performed in accordance with GPUN Operational QA Program. Thi. work is clawuifled Important to Safety/Nuelear Safety Related.

5.0 ;ENPfMMATUo To BS 3U3ITTED 53.1 UT data shoots and calibration sheets in accordance with Reference 2.4.

6.0 jkTTACEa=8

'5.1 Zxhibit 1 - Plate Numbering scheme shown on CBI drawing 9-0971, Sheet 2.

'5.2 Bxhibit 2 - Alternate Inspection Location Selection Scheme.

004/DC40.13

. ,IS-402950-001 Rev. 0 Page 14 of 23 EXHIT lt Plate Numbering Ube" S8@U0 or CBI Drawing 9-0971 Sheet 12 004/0C40. 14

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1-402950-001 Rev. 0 Page 23 of 23 Alternate inspection Xocation Selection Scheme 9

7 8 1 10 6 original 2 11 5 4 3 12 5 _ 13 Figure #3 illustrates the selection scheme in which an alternate inopection point shall be determined. The original inspection point, which is unaccessibl-, or cannot be scanned due to surface conditioan, shall be located on the applicable sketch (Reference 2.8). If the original randomly chosen point in unacces-ible, or cannot be scanned due to surface conditions, then per Figure #2 Grid #1 shall be the alternate location.

if Grid #1 Ls also unaccesuLble, or cannot be scanned due to surface conditions, then Grid 2, 3, 4, etc, shall be selected until a location is accessible.

If the original randomly chosen location borders a wold or penetration, and is unaccessible,then the grid which ia accessible in the clockwise direction por Figure #3 shall be selected as the alternate inspection location. In all cases, the alternate inspection location shall be located on the original vessel plate.

004i/0040.23