ML20086R498
| ML20086R498 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 07/21/1995 |
| From: | Saccomando D COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20086R500 | List: |
| References | |
| NUDOCS 9507310160 | |
| Download: ML20086R498 (27) | |
Text
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1 WD Opta1%cc Downer
- Gnne, II. NK15 July 21,1995 Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission War,hington, D.C. 20555 Attn: Document Control Desk
Subject:
AdditionalInformation Pertaining to the to Application for Amendment to Facility Operating Licenses:
Byron Nuclear Power Station, Units 1 and 2 NPF-37/66: NRC Docket Nos. 50-454/455 Braidwood Nuclear Power Station, Units 1 and 2 NPF-72/77: NRC Docket Nos. 50-456/457
Reference:
- 1) D. Saccomando letter to Nuclear Regulatory Commission dated February 13,1995, transmitting Proposed Technical Specification Amendment Regarding increase in the IPC Criteria
- 2) Denise M. Saccomando letter to Nuclear Regulatory Commission dated June 20,1995, transmitting preliminary leak rate test results or Indications Restricted from Burst
- 3) Harold D. Pontious, Jr. letter to Nuclear Regulatory Commission dated July 7,1995, transmitting a revised proposed Technical Specification Amendment Regarding increase in the Alternate Plugging Criteria Reference 1 transmitted Commonwealth Edison Company's (Comed's) proposal to amend Appendix A, Technical Specifications of Facility Operating Licenses NPF-37, NPF-66, NPF-72 and NPF-77. The proposed amendment request addresses Technical Specification changes necessary to increase the Interim Plugging Criteria (IPC) value for Braidwood and Byron Station Unit 1 Steam Generators from 1.0 volt to 3.0 volts.
Subsequent to that submittal, Comed and the Nuclear Regulatory Commission (NRC) met on February 23,1995, to discuss the submittal. During that meeting Comed presented a model which addressed leakage from indications restricted from burst (IRBs). After discussions, Comed pursued the development of an alternate leak rate model along with a test program to support the alternate leak rate model.
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NRC Document Control Desk June 21,1995 in Reference 2 Comed provided the Staff with additional technical justification supporting the 3 voit Alternate Plugging Criteria (APC) request. This document supersedes that which was transmitted in Reference 2.
Attachment 1 outlines the development and description of a Comed /EPRI sponsored test program which determined the bounding leak rate value of an IRB l by the presence of the tube support plate. Specifically Attachment 1 contains: l l
Section 1: History and Test Program Objective Section ll: Total Test Program Development and Evaluation of Test Variables Section lil: Test Program Section IV: Bounding Test Program Differences since April 3,1995 Submittal Attachment 2 "lRB Summary Leak Test Report" contains the over611 test l
conclusions, raw data in tabular form, and graphical representation of the data.
Specifically Attachment 2 contains:
Section 1.0 Overall Test Conclusions Section 2.0 Test Data and Reduction Methods Section 3.0 Data Evaluation Methods Section 4.0 Test Evaluations Section 5.0 Trend Analyses Section 6.0 Leak Rate Uncertainty Assessment Comed has reviewed the results of the bounding IRB test program proposed to the NRC on April 3,1995. Based upon Commonwealth Edison's review of this new information, the following conclusions have been reached:
The data provided in Attachment 2 are the latest final results and clearly demonstrate that large leakages should not be anticipated even with substantial offset of the crack outside of the tube support plate.
The bounding leak rate for the 3/4" diameter tubing determined by the latest final results of this test program is 5.5 gpm, for a 0.74" long crack extending outside the support plate 0.10". As discussed in meetings with the NRC on February 23, April 11, May 9, June 27, June 29 and July 19, Comed believes that it has succeeded in producing a test specimen with crack length equal to the thickness of the support plate and tested its leak rate; thereby defining a " bounding IRB teak rate."
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NRC Document Control Desk June 21,1995 !
Experimentalinconsistencies as the result of deviation from the test specification for 5 of the specimens were discovered during final report '
review. The results and conclusions for all 10 tests conducted are reported and, we believe, lead to the conclusion that the test program objective. of l developing a bounding IRB leak rate has been achieved. However, Comed is having as many tests, as there are new specimens available, re-run to assure that the original test specification is met. These new tests, will be reported i in a Summary Leak Rate Test Report supplement to be submitted on or before August 4,1995. Additionally, this supplement will contain the :
results of Comed's orifice testing. These results are not to be included in Attachment 2 because of the delay in completion of the orifice testing due to equipment problems. The results of the re-run of the test specimens along with the orifice test results may have a slight impact on the bounding leak rate of 5.5 gpm. Any impact on the leak rate will be reflected in the upcoming supplement.
Comed would like to reiterate that the pending amendment request and the leak rate test program were designed to incorporate many conservatisms, which we believe establishes a firm " defense in depth" approach which justifies the approval of a 3.0 volt APC. These conservatisms are as fo!!ows:
Comed will stabilize appropriate tube support plates to restrict the support plate displacement to less than 0.1" thus reducing the calculated probability of tube burst to < 10~5 and increasing our operating safety margin.
In the pending request Byron and Braidwood have reduced their Unit 1 reactor coolant system Dose Equivalent lodine-131 from 1.0 microCuries/ gram to 0.35 microCuries/ gram until the steam generators are replaced.
Comed will use the conservative Generic Letter POD value of 0.6, for all voltage amplitude ranges,in projected leak rate and probability of burst calculations.
Byron and Braidwood will repair all ODSCC indications greater than 3.0 volts and has eliminated the request to implement a 10 volt upper voltage repair i limit.
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NRC Document Control Desk June 21,1995 A factor of 2 conservatism has been incorporated into the TRANFLO model which is used to determine the amount of tube support plate movement under accident conditions. To further ensure that the postulated deflection of the tube support plates is correct, Comed used RELAP5 to confirm the loads developed by Westinghouse using TRANFLO.
The bounding IRB leak rate for the 3/4" tubing was based upon a 0.74" long crack extending outside of the support plate 0.10". Comed believes that this bounding leak rate is truely conservative and would correspond to voltages far in excess of the pending 3 volt request. Additionally,it is important to recall that historically the largest indications observed by Byron and Braidwood have been <0.3" in length, as measured in tube pulls.
The bounding IRB leak rate was determined with specimens tested under clean conditions and maximum tube to tube support plate gap. Previous visualinspection of the Byron and Braidwood steam generators have identified deposits in the crevices of the tube support plate which realistically would reduce crack opening and further restrict leakage under accident conditions.
To the best of my knowledge and belief, the statements contained in this document are true and correct. In some respects these statements are not based on my personal knowledge, but on information furnished by other Comed employees, contractor employees, and/or consultants. Such information has been reviewed in accordance with company practice, and I believe it to be reliable.
Sincerely, L/ ., ~(J Denise M. Saccomando Nuclear Licensing Administrator cc: D. Lynch, Senior Project Manager-NRR R. Assa, Braidwood Project Manager-NRR G. Dick, Byron Project Manager-NRR S. Ray, Senior Resident inspector-Braidwood H. Peterson, Senior Resident inspector-Byron Office of Nuclear Safety-IDNS K:als Dybwd sigen/FCTuT;4
Attachment 1 Indications Restricted From Burst Test Program This attachment outlines the development and results of a Comed / EPRI sponsored test program to determine the bounding leak rate value of an indication which has been restricted from burst (IRB) by the presence of the tube support plate (TSP).
Specifically this attachment contains:
- Section i History and Test Program Objective
- Section il Total Test Program Development and Evaluation of Test Variables
- Section ill Test Program
- Section IV Bounding Test Program Differences Since 4/3/95 Submittal :
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l l Section i History and Test Program Objective i
On February 23,1995, Comed and the NRC met to discuss the potentialincrease of the interim plugging criteria for 3/4" tubes from 1.0 volt to 3.0 volts until steam generator replacement at Braidwood 1 and Byron 1. During that meeting Comed i presented a model which quantified the low probability which exists for indications I that may potentially " leak" within the confines of the TSP at pressures equal to ,
main steam line break (MSLB) pressure.
At the Staff's request, Comed provided the Staff with data which would quantify the potential benefit from using this analytical leakage model. Additionally, Comed also pursued the use of an alternate leak rate model which did not rely on a bobbin voltage correlation with crack length. A description of this model and results quantifying the potential benefits were provided to the Staff in Reference 2.
To fully support the alternate leak rate model, it is necessary to define a fixed leak rate for a single indication restricted from burst (IRB) by the presence of the TSP.
One approach is to define an IRB bounding leak rate and apply that leak rate to each IRB independent of size. In an effort to obtain a bounding leak rate for IRB, Comed submitted a proposed laboratory test program to the Staff in Reference 3. f This proposed laboratory test program used 7/8" diameter tubing specimens with throughwall outside diameter stress corrosion cracking (ODSCC) crack lengths of 0.34",0.40" and 0.50". These specimens would be pressurized to approximately 15% above calculated burst pressure while contained within a simulated support i plate. Leak rate measurements would then be performed at both room and operating temperature.
The development of this phase of the test program was based upon samples ,
immediately available for testing. Specifically, our decision to use 7/8" diameter ,
specimens with 0.34", 0.40" and 0.50" ODSCC crack lengths, rather than the :
Byron and Braidwood size 3/4" diameter tubing was because of specimen availability. Laboratory induced ODSCC specimens take several weeks to generate.
Furthermore, it is Comed's position that the leak rate is a geometrical function that is not dependent on the tube diameter. To demonstrate this, testing includes both ;
3/4" and 7/8" diameter tubing.
t in early April the plan and the preliminary results from this test program were reviewed by the EPRI SGDSM Ad-Hoc committee. Modifications to the test plan, !
as well as the leak rate calculation, were made based upon suggestions from the committee.
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On March 22,1995, the Staff and Comed participated in a teleconference to discuss this test program. During that teleconference, Comed recognized that the proposed test program needed to be enhanced to address new concerns.
Based upon these concerns Comed proceeded with the following actions:
- 1. Redefine objectives of a new and expanded laboratory leak rate test program.
- 2. Develop a list of required test variables to meet the leak rate test program objectives.
- 3. Develop a parametric sensitivity study test matrix based upon the list of variables.
- 4. Develop a detailed prioritized test program to bound variables of the parametric sensitivity study.
- 5. Define a final test plan to meet test objectives.
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Section 11 TOTAL TEST PROGRAM DEVELOPMENT AND EVALUATION OF TEST VARIABLES l Test Plan Objective Develop a bounding MSLB leak rate for large (>0.6") indications which have been restricted from burst (IRB) by the presence of the tube support plate (TSP). This bounding leak rate value will be used in a leak rate calculation which takes into account both freespan and IRB leakage.
Comed does not have an objective to create or test a low voltage (1 volt or less) 3/4" long crack. However, long cracks (>0.6") will be created and tested.
Variables Considered in total test oroaram As part of Comed's development of a total laboratory test program from which a l
bounding test program was derived, the following variables were taken into consideration.
Leak rate sensitivity to:
e Tube size e Crack length i e Test temperature l e Crevice condition 1 o TSP gap e Crack exposure outside TSP e Tube pressurization at pressures up to freespan burst i e Freespan to IRB leak rate comparison l l
Tables 11-1 and ll-2 define the elements of a total parametric study which would be required if all these variables were tested for each possible combination. '
Comed's Evaluation of Test Variables Comed performed an evaluation of all the possible test variables and determined which are important to the bounding test program. The following is a description of how we addressed each variable in the test program.
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i Sensitivity to tube size:
l Byron and Braidwood Unit 1 tubing is 3/4" diameter. Due to the immediate ,
availability of 7/8" tubing corrosion test specimens, the test program was begun '
using 7/8" tubing. These test results were used to define additional testing requirements and test modifications. Subsequent testing included 3/4" diameter tubing.
A review of the geometry of the hypothetical crack is contained within WCAP-14273. It is important to note that for an IRB, the equations provided to define the crack opening area depend upon the length of the crack, and the gap between the outside diameter of the tube and the inside diameter of the tube support hole.
In addition, the WCAP describes the basis upon which the maximum clearances between hole and tube were assembled. This leads to the fact that the calculation of the crack opening area is based on geometric equations. Review of these equations indicates that there is no dependency of the crack opening on tube diameter.
To demonstrate that the leak rate is a geometrical function of crack opening and is not dependent on tubing diameter, Comed performed testing on both 7/8" and 3/4" diameter tubing. Based upon the similar test results it is not necessary to do duplicate testing with both 7/8" and 3/4" similar tubing.
Sensitivity to crack length:
Specimens were prepared for 3/4" diameter tubing with a goal of achieving throughwall crack lengths in the following ranges: 0.25"- 0.45" 0.45"- 0.60" and 0.60" - 0.75". Use of these ranges will develop a conservative upper bound leak rate based on the following facts:
e Braidwood 1 and Byron 1 largest indicatiunc of 10.3 and 10.9 volts had throughwall crack lengths of 0.20" and 0.27", respectively, with burst pressures > 4000 psi at operating temperature. This is well within the experience of the EPRI pulled tt.be database.
e The critical throughwall crack length for a burst at MSLB pressure of 2560 psid for a 3/4" diameter tube at lower tolerance level (95% / 95%) material properties is 0.75". Such an indication would have a bobbin voltage of > 40 volts.
e The EPRI pulled tube data database demonstrates that no indication of < 10 volts has had a throughuall crack > 0.37". Therefore, it is unrealistic to I assume that a 0.75" axial throughwall crack would develop in a plant where a l 3.0 voit APC is applied.
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The crack length test variable, with > 0.6" long ODSCC specimens, is expected to bound by a factor of 1.5 the largest indications seen in the EPRI pulled tube data base for indications below 10 volts. In order to obtain indications with throughwall crack lengths >0.6", Comed used fatigue to lengthen certain laboratory induced ODSCC specimens.
Sensitivity to test temoerature:
Westinghouse has modified a test facility to accommodate high leak rates at l operating temperature test conditions. The test facility has the capability to measure the leak rates up to at least 10 gpm at 615 F. Testing at elevated temperatures is extrernely time consuming; therefore, to expedite testing the test
} plan included development of a temperature correlation factor. A correlation of operating and room temperature conditions was to be developed from test data ,
obtained in this program. The existing leak rate adjustment procedures indicate that !
I operating temperature leak rates are about a factor of 0.5 to 0.6 :oom temperature leak rates. This correlation was confirmed for indications confined within the TSP.
Sensitivity to crevice condition:
If the test program is expanded beyond the initial bounding test program described in Section lil, some tests may be conducted with " packed" TSP crevice conditions and
" clean" TSP crevices. Crevice packing will be performed by packing the crevice with magnetite and a binder followed by baking of the specimen. This is typical of the deposits seen on pulled tubes. This test is representative of actual steam generator crevice conditions believed to be present at Byron and Braidwood. If the leak rates are considerably different, test results will be evaluated to determine appropriate I
application of the data in leakrate calculations. The initial bounding test program will be performed using unpacked crevices. This will provide a conservative leak rate value.
.Samitivity to_ TSP oao:
The range of possible maximum TSP clearances for drilled hole TSP steam generators is 0.025". The 0.025" value was obtained by applying a 95% confidence level to the upper diameter limit of a drilled support plate hole and the 95% confidence level of the minimum diameter of the tubing for a bounding 7/8" tube. This test at 0.025"
( clearance will provide a bounding leak rate value for maximum gap.
Sensitivity to crack exoosure outside TSP:
The maximum TSP deflection with tube support plate stabilization is shown in WCAP-l 14273 to be 0.10" for model D-4 units with 3/4" tubing. This value is extremely conservative with a factor of 2 applied to the TRANFLO loads. A review of inspection data for Byron 1 and Braidwood 1 has not found any axial ODSCC indications t
extending beyond the edges of the TSP. Therefore, based upon a comparison of the reallocation of indications within the tube support plates and a review of the conservatisms within the calculation of tube support plate maximum deflection, K:ala Dybwd Stgen/IMTesT:10 L_____-_-_-___-________-_ . .
' Comed's ess:ssm:nt is that testing with TSP offstit of 0.10" for 3/4" tubing is extremely conservative. For 7/8" diameter tubing, offset values of 0.15" will be used to simulate the expected TSP maximum deflection value for Model 51 units.
Leakrate vs. Tube Pressurization:
Indications contained within the TSP will be pressurized and leak rates measured: ;
e at MSLB pressure e between MSLB pressure and calculated burst l e above calculated burst pressure j e 1000 psi increments up to approximately 10,000 psi. t Testing may be repeated with crack offset of 0.1" and 0.15" outside TSP. t The objective of these pressurization steps is to determine the maximum leak rate vs crack opening configuration which is postulated to occur. 4 Comparison of freesoan to IRB leak rate:
Certain specimens will be pressurized to values below MSLB conditions while in freespan so that the freespan leak rate can be measured and extrapolated to MSLB conditions using the EPRI leak rate procedure. This value will then be compared to the ;
IRB leak rate obtained from these specimens while they are confined within the TSP.
These data will be used to show a correlation between the freespan and IRB leak rate. The result may be that the freespan leak rate is higher than the IRB leak rate for certain size indications. ,
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l Section lil TEST PROGRAM Test Plan Objective Develop a bounding MSLB leak rate for large (>0.6") indications which have been restricted from burst (IRB) by the presence of the tube support plate (TSP). This bounding leak rate value will be used in a leak rate calculation which takes into I account both freespan and IRB leakage. r Comed does not have an objective to create or test a low voltage (1 volt or less) 3/4" I long crack. However, long cracks (>0.6") will be created and tested.
i Total Test Proaram Based on Comed's evaluation of the critical variables required to meet the programs objective, a total test program was developed and is provided in Table 111-1. The notes for Table ill-1 outline the general testing sequence and prioritization criteria which determine the order in which specimens are tested. The specific testing parameters and specimen characteristics for completed tests are given in Section IV. >
This total test program was developed to address sensitivity to:
Differences in leak rates between 3/4" and 7/8" diameter tubing Sensitivity of crack length inside the support Differences in leak rate data between room temperature and operating condition tests (validate room temperature to operating condition correlation)
Differences between leak rates in packed versus clean crevices Differences in TSP crevice clearances ;
Length of crack extending outside the TSP l Differences in pressurization levels ,
Differences between freespan and IRB leak rates i Boundina Test Plan L
Using Table 111-1, the bounding test program is defined as tests 1 - 1, 1 -2, 1 -6, 1 - 7, 2-1, 2-4, 2-7, 2-10 and 4-1. This testing will provide a conservative bounding leak rate value for IRBs at MSLB.
It is Comed's position that the only testing required to bound the MSLB leak rate are tests 2-1, 2-4, 2-7 and 1-7. Other tests are only planned to improve the industries I understanding of leakage from IRB's. '
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TABLE III-1 Test Matrix for Indications Restricted from Burst (IRBs)
Crevice Crack Length Gap Free Crack to TSP Bladder Test Test Pri. Tube Teamp Span ONeet No.
Pres. Test Seq. ority Dia. Leak Open Pack .25- .45 .6 .6- .02 .025 AP" Time Test 0.F 0.1" .15" og,,g pay.
.45 .75 (inch) 1-1 la 1 7/8 615* x x x x x x 0.0 12 1-2 la 1 7/8 615' x x x x x x 0.15 12 1-3 la 2 7/8 615' x x x x x x 0.15 12 1-4 lb 4 7/8 615* x x x x x 7 1-5 lb 5 7/8 615* x x x x x 12 1-6 la 1 3/4 615' x x x x x x 0.0 12 1-7 la 1 3/4 615' x x x x x x 0.1 12 1-8 la 2 3/4 615' x x x x x x 0.1 12 1-9 lb 4 3/4 615' x x x x x 7 1-10 lb 5 3/4 615' x x x x x 12 1-11 la 3 7Al 615' x x x x x x 0.15 12 1-12 la 3 3/4 615' x x x x x x 0.1 12 2-1 2 1 7/8 615' x x x x x x 0.15 12 2-2 2 2 7/8 615' x x x x x x 0.15 12
' 2-3 2 3 7/8 615' x x x x x x 0.15 12 2-4 2 1 7/8 615* x x x x x x 0.15 12 2-5 2 2 7/8 615* x x x x x x 0.15 12
TABLE III.1 Crevice Crack Length Gap Free Crack to TSP Bladder Test Test Pri. Tube Temp Span Offset Pres. Test
- o. Seq. ority Dia. Leak AP" Time Open Pack .25 .45.8 .8- .02 .025 Test 0.0P' O.1" .15" Offset Days
.45 .75 (inch) 2-6 2 3 7/8 615' x x x x x x 0.15 12 2-7 2 1 3/4 RT,T x x x x x x 0.1 12 2-8 2 2 3/4 615' x x x x x x 0.1 12 2-9 2 3 3/4 615' x x x x x x 0.1 12 2-10 2 1 3/4 RT,T x x x x x x 0.1 12 2-11 2 2 3/4 615* x x x x x x 0.1 12 2-12 2 3 3/4 615* x x x x x x 0.1 12 l
3-1 3 3 7/8 T,RT x x x x x 0.15 10 3-2 3 3 7/8 T,RT x x x x x 0.15 10 3-3 3 4 7/8 T,RT x x x x x 0.15 10 4-1 4 1 7/8 RT x x x x x 0.15 10 4-2 4 2 3/4 RT x x x x x 0.1 10 t
l N:tes:
- 1. Test sequence includes pressurizing with a bladder typically to above the free span burst pressure. Some specimens include incremental increases in bladder pressure beyond that equivalent to a free span burst. For test sequences 1 and 2, the bladder pressurization and subsequent leak tests follow leak tests that apply primary side pressure and flow to obtain the APs. Thus, for these tests, the bladder pressurization is perfonned to open the crack beyond that obtained within the pressure capability of the facility.
l
r NOTES FOR TABLE lil-1 Test Plan for Indications with Restrained Burst (IRBs)
Test Sequences Test Sequence 1:- 615*F, Crack Lengths > 0.6" Seauence la A. Free span leak test at 1500,1700 and 2000 psi AP B. Leak test with crack centered (0.0 offset) in TSP at 2000, 2335 and 2560 psi AP C. Measure crack opening diameter and area D. Leak test with crack 0.1" offset outside TSP at 2560, 2700, 2900 psi AP (up to facility lirnit)
E. Measure crack opening diameter, area and evaluate crack extension F. With crack centered or 0.1" (test matrix specification) offset outside TSP, pressurize to above calculated burst pressure with bladder e Note: Test sequence 1 is applied to the longest cracks which are expected to open up and contact the ID of the TSP hole within the pressure / flow limits of the facility. The bladder pressurization step is applied to assure crack flank to TSP contact for comparisons with the leak rates from step D.
G. Leak test with crack centered or 0.1" offset outside TSP at 2335 and 2560 psi AP H. Measure crack opening diameter, area and evaluate crack extension
- 1. With the same crack position as step F, pressurize with a bladder (with foil if necessary) to about 1000 psi above the prior pressurization step J. Repeat leak test of step G K. Repeat steps I and J with increases in bladder pressure in 1000 psi increments until bladder / foil pressurization increase cannot be achieved (approximately burst pressure inside TSP on order of 8000 psi) e Note: If it is demonstrated on one sample in this test seque' ice, that the leak rates do not significantly increase by the pressurization of stops I to K, steps I to K may not be repeated on additional specimens and this test sequence will be terminated at step H for the later specimens L. Measure crack opening diameter, area and evaluate crack extension Saguence 1b Perform test with Sequence la steps A to E (i.e., no bladder pressurization steps)
K:ala Ilybwd Sigen/IK' rest:13
i NOTES FOR TABLE lil-1 '
Test Seouence 2: 615*F and Room Temoerature. Crack Lenaths < 0.6" A. Free span leak test at 1500,1700 and 2000 psi AP B. Leak test with crack tip centered at 2000,2335,2560 psi AP up to facility limit C. Leak test with crack tip 0.1" offset from the edge of the TSP at 2560, 2700 psi AP up to facility limit '
D. Measure crack opening diameter, area and evaluate crack extension E. With crack tip 0.1" offset, pressurize to above calculated burst with bladder e Note: Test sequence 2 is applied for shorter cracks which may not open to significantly contact the ID of the TSP hole within the pressure / flow limits of the facility. Thus, steps A and B may result in comparable leak rates. The bladder pressurization step is applied to assure that crack flank to TSP contact is achieved to assess the influence on leak rates.
F. Leak test at 2335,2560 psi AP at both room and operating temperature for at least one specimen.
G. Measure crack opening diameter, area and evaluate crack extension H. With the 0.1" crack position, pressurize with a bladder (and foil if necessary) to about 1000 psi above the prior pressurization step !
- l. Repeat leak test of step F J. Repeat steps H and I with increases in bladder pressure of 1000 psi increments until bladder / foil pressurization increase cannot be achieved (approximately burst pressure inside TSP on order of 8000 psi) e Note: If it is demonstrated on one sample in this test sequence or by the equivalent pressurization of Sequence la tests, that the leak rates do not significantly increase by the pressurization of steps H to J, steps H to J may not be repeated on additional specimens and this test sequence will be terminated at step G for the later specimens K. Measure crack opening diameter, area and evaluate crack extension i
Test Seouence 3: 615*F and Room Temoerature Leak Rate Comoarisons A. Pressurize to above calculated burst pressure with bladder B. Room temperature test at 2000, 2335, 2560 psi AP C. Operating temperature test at same pressure differentials D. Measure crack opening diameter, area and evaluate crack extension E. Move crack to 0.1" outside TSP, pressurize to same pressure with bladder ;
F. Room temperature test at same pressure differentials G. Operating temperature test at same pressure differentials H. Measure crack opening diameter, area and evaluate crack extension K:nts Dybwd Segen/IMic:T:14
i NOTES FOR TABLE 111-1 Test Seouence 4: Room Temoerature. Bladder Pressurization to Establish IRB Leak Rate Maonitude and Effects of Hiah " Burst" Pressures on Leak Rates l
A. Pressurize to above calculated burst pressure with bladder l B. Room temperature test at 2335, 2560 psi AP l C. Measure crack opening diameter, area and evaluate crack extension l D. Move crack to 0.1" outside TSP and pressurize to the same pressure l E. Room temperature repeat of step B leak rate tests i F. Measure crack opening diameter and area l G. With the 0.1" crack position, pressurize with a bladder (and foil if necessary) to i about 1000 psi above the prior pressurization step l H. Repeat leak test of step B i
- 1. Repeat steps F and G with increases in bladder pressure of 1000 psiincrements l until bladder / foil pressurization increase cannot be achieved (approximately burst pressure inside TSP on order of 8000 psi) e Note: If it is demonstrated on one sample in this test sequence or by the equivalent pressurization of Sequences la or_2 tests, that the leak rates do not significantly increase by the pressurization of steps G to I, steps G to i may not be repeated.
J. Measure crack opening diameter, area and evaluate crack extension Packed Crevice Simulation ,
e Pack crevice with magnetite and a binder followed by baking of the specimen to obtain a fairly hard deposit typical of that found on pulled tubes at TSP crevices 1
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K:nta:Dybod Stgen/DCe T:15
i NOTES FOR TABLE lil-1 l
l Test Plan for Indications with Restrained Burst (IRBs) )
Test Priorities !
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l Priority 1 I
o Recommended test matrix to establish bounding leak rate for large cracks (test I sequence 1) and the leak rate dependence for more realistic crack lengths (test '
sequence 2) e An initial test (sequence 4) of an indication pressurized by a bladder to obtain an early estimate of the magnitude of leak rates to be expected l l
Priority 2 1
- Repeat of priority 1 tests. Tests performed upon completion of priority 1 tests j only if bad test data are obtained or the initial test results in unacceptable l uncertainties on the leak rates relative to adequately defining a leak rate model for IRBs Priority 3 e Tests performed to compare room temperature leak rates with operating temperature leak rates. These tests would be performed only if the leak rates of
,, priority 1 tests exceed the facility capability at operating temperatures and some of the priority 1 tests must be run at room temperature.
e Tests with packed crevices. Tests to be performed if in situ leak rates are to be l used for reference SLB leak rates rather than free span plus IRB leak rates. These i tests would provide physicalinsight into expectations to be obtained with in situ leak rate measurements.
Priority 4 e Tests of additional variables not considered to be necessary to adequately define IRB leak rates, j l
I Priority 5 e Test variables that are judged not worthy of consideration for testing K;n1LDyt=d.Sgen/Ut' rest:16 i
3
'S:ction IV L
Bounding Test Program Differences Since 4/3/95 Submittal f
in order to facilitate testing and apply lessons learned during the early phases of the test program, minor changes were made to the test program as submitted to the NRC on April 3,1995 Reference 6. These changes do not significantly effect the test results or conclusions.
The following is a detailed listing of differences between the test program submitted in Reference 6 on April 3,1995 and the actual testing that either has been or will be conducted. The corresponding notes to describe numbered changes follow the specimen listed below.
Test 1-1 e ODSCC throughwall crack length of 0.62" was obtained by lengthening an existing-ODSCC specimen with fatigue, eSpecimen was improperly positioned radially within the TSP hole which reduced to tube to TSP gap below that specified in the test sequence. This may have caused the crack opening to contact the TSP sooner than with proper gap. New test i specimens are in the process of being re-runned to demonstrate results with proper gap.
NOTES: 1, 2, 3, 4, 5 Test 1-2 e ODSCC throughwall crack length of 0.62" was obtained by lengthening an existing ODSCC specimen with fatigue.
eSpecimen was improperly positioned radially within the TSP hole which reduced to tube to TSP gap below that specified in the test sequence. This may have caused the crack opening to contact the TSP sooner than with' proper gap. New test specimens are in the process of being re-runned to demonstrate results with proper )
gap.
NOTES: 1, 2, 3, 4, 5 i I
Test 1-6 l L e Test plan calls for a 0.025" TSP gap, test was inadvertently run with a 0.026" gap. This adds an unnecessary conservatism to the test results.
1 NOTES: 2, 3, 4, 5 k'
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Test 1-7 e ODSCC throughwall crack length of 0.60" was obtained by lengthening an existing ODSCC specimen with fatigue, e Freespan leak rate testing was not performed on this specimen. Testing was not performed due to an oversight at the test facility. Upon discovery testing had already been completed beyond bladder pressurization, making freespan testing at that point of no value.
The freespan tests were originally planned to aid identification of crack interaction with the TSP based on differences between freespan and with TSP leak rates. I However, freespan testing might plastically open the crack face more than the tube to TSP gap and then require deformation of the crack face to perform offset leak tests. It was then decided to perform a freespan leak test after the offset only as a demonstration of the magnitude change in leak rates and without the presence of the TSP.
Test 1-7 freespan data is not a significant loss of data since TSP interaction above about 2200 psi is apparent in the slope of the leak rate verses AP curve. The free span data point for Test 1-6 adequately demonstrates the large difference in leak rate I
between freespan and within the TSP for large cracks.
eSpecimen was improperly positioned radially within the TSP hole which reduced to tube to TSP gap below that specified in the test sequence. This may have caused )
the crack opening to contact the TSP sooner than with proper gap. New test specimens are in the process of being re-runned to demonstrate results with proper gap NOTES: 2, 3, 5 Test 2 e ODSCC throughwall crack length of 0.515" was obtained by lengthening an existing ODSCC specimen with fatigue.
eSpecimen was improperly positioned radially within the TSP hole which reduced to tube to TSP gap below that specified in the test sequence. This may have caused the crack opening to contact the TSP sooner than with proper gap. New test specimens are in the process of being re-runned to demonstrate results with proper gap.
NOTES: 1, 2, 3, 5, G K:nta:D>t=J Stgen/IIVresT:18 I
_ . - - _ _ __ _ _ _ _ . - - _ - . - - . _ _ - - . - _ _ . - - _ _ -__----_-n__- - - _ _ _ . _ - _ - - - _-___.___ _
Test 2-4 e Testing originally called for crack to be axially centered in TSP. After initial flow testing was completed, and prior to bladder pressurization, program was revised to call for the crack tip to be placed at the edge of the TSP prior to leak rate testing.
This provides a more conservative leak rate value. The results for this test show leskage is essentially freespan with or without the TSP and thus the change in crack alignment had no influence on the Test 2-4 results.
This change is consistent with the May 25,1995 clarification letter reference 7, and the leak rate test program.
NOTES: 1, 3, 5, 6, 7 Test 2-7 e ODSCC throughwall crack length of 0.577" was obtained by lengthening an existing ODSCC specimen with fatigue.
e Testing originally called for freespan and 0.0" offset to be conducted at operating temperature conditions. " Low pressure" testing was performed for these test steps at room temperature up to 2335 AP. This was to expedite testing program by 4 to 6 days. This does not limit the applicability of the test results since the most limiting 0.10" offset condition was tested hot, and the cold to hot adjustment procedure is well supported by the test results. Due to the deviation in the test plan, test specimen 2-8 (laser slot; wac r%d to support data for test 2-7.
This change is as describes in the May 25,1995 test program reference 7.
eSpecimen was improperly positioned radially within the TSP hole which reduced to tube to TSP gap below that specified in the test sequence. This may have caused the crack opening to contact the TSP sooner than with proper gap. New test specimens are in the process of being re-runned to demonstrate results with proper gap.
NOTES: 2, 3, 5, 6
. Test 2-8 eTest was conducted on a specimen with a 0.55" throughwalllaser cut slot instead of a corrosion induced crack.
eNo bladder pressurization tests were performed.
eThe sequence for Test 2-7 was followed since data from Test 2-8 was used to support test 2-7 results.
K nin Dybwd Sycaf!MicaT 19
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' Test 2-10 )
- NOTES: 2, 3, 5, 6, 7 1
Test 4-1 ]
i e Added operating temperature test condition leak rate test after bladder i pressurization up to 8900 psi. This provides additional data to strengthen j temperature correlation. j i
NOTE: 1 '
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i K: ale Dybwd.Seca/IM' Test;20 ,
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NOTES FOR DESCRIPTION OF CHANGES t
- 1. Testing for 7/8" diameter tubing was conducted with a 0.15" TSP offset rather than the originally specified value of 0.10". This is the maximum calculated TSP displacement value with the anticipated tube expansion, for a Model 51 steam ;
generator which has 7/8" diameter tubing.
- 2. Testing originally called for crack to be centered in TSP. Program was revised to f call for the crack tip to be placed at the edge of the TSP prior to leak rate testing. ;
This provides a more conservative leak rate value.
- 3. Testing originally called for TSP to be offset 0.10", it was not specifically stated that the crack should extend 0.10" (or 0.15" for 7/8" tubing) outside TSP. l Program was revised to state that the crack tip should extend 0.10" (0.15") !
outside TSP.
i
- 4. Original test sequence called for free span leak rate up to 2000 psid to be l conducted prior to 0.0" offset testing. Test sequence was changed to require ,
freespan leak rates after 0.0" and 0.10" (0.15" for 7/8" tubing) offset at the [
highest pressure achieved. This allows freespan leak rates to be conducted at }
pressures higher than the original 2000 psid without concern of opening the crack :
face beyond the TSP gap for later testing within the TSP. !
- 5. Original test program called for 0.0" offset at pressures up to 2560 psid followed I by 0.10" offset starting at 2560 p::id. Program was changed to perform 0.0" offset testing up to 2335 psid followed by 0.10" (0.15" for 7/8" tubing) offset starting at 2335 psid. This change was made to obtain more leak rate data for the l limiting 0.10" offset conditions. j
- 6. Original test sequence called for freespan leak rate up to 2000 psid to be i conducted prior to 0.0" offset testing. Test sequence was changed to require freespan testing after the 0.0" offset and before the 0.10" offset. This change for ,
moderate length cracks was made to permit easier comparison of freespan and ;
offset 0.10" leak rates (more limiting than 0.0" offset) to aid assessment of l potential interaction with the TSP. In addition, the start of 0.10" offset testing ;
was lowered from 2560 psid to 2335 psid to obtain more leak rate data for the l limiting 0.10" offset condition. j 1
- 7. Original test program called for initial bladder pressurization above calculated burst, step was added to pressurize approximately 1000 psi below calculated l burst. This provides another data point to determine where max leak rate occurs.
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Raftrancas l l
l I
- 1. M. Lynch letter to D. Farrar dated March 24,1995, transmitting the Nuclear Regulatory Commission comments on Commonwealth Edison's Company )
Proposed Test Program for Steam Generator Tube Indications Restricted from l Burst. j i
- 2. D. Saccomando letter to NRC dated March 20,1995, transmitting information l Regarding Questions Pertaining to increased Interim Plugging Criteria. !
- 3. D. Saccomando letter to the Nuclear Regulatory Commission dated March 15, j 1995, transmitting Commonwealth Edison's response to the Nuclear Regulatory j Commission Concerns as Documented in Meeting Summary dated March 14, ;
1995.
- 4. M. Lynch letter to D. Farrar dated Mcrch 14,1995, transmitting a Meeting Summary from the February 23,1995, NRC/ Comed Meeting. ;
- 5. WCAP-14273 (Proprietary), " Technical Support for Alternate Plugging Criteria with Tube Expansion at Tube Support Plate Intersections for Braidwood-1 and !
Byron-1 Model D-4 Steam Generators, " Westinghouse Electric Corporation, l February 1995. !
- 6. D. Saccomando letter to NRC dated April 3,1995, transmitting Comed's !
proposed test program for IRB testing. }
i
- 7. D. Saccomando letter to NRC dated May 25,1995, transmitting information f regarding leak rate test program.
- 8. D. Saccomando letter to the NRC dated June 20,1995, transmitting preliminary ,
data and results from the leak rate testing program. l t
- 9. H. Pontious, Jr. letter to the NRC dated July 7,1995, transmitting a revised l proposed Technical Specification amendment regarding an increase in Alternate l Plugging Criteria (APC) l i
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K:als pyted Steen/IPCTesT:22 i
Att chm:nt 2 indications Restricted from Burst (IRBs) Summary Leak Test Report K:ula Dybwd.Sigen!!!CTesT.23