ML17199T459
| ML17199T459 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 11/30/1987 |
| From: | Silady J COMMONWEALTH EDISON CO. |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8712070439 | |
| Download: ML17199T459 (16) | |
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Address Reply to: Post Office Box 767 Chicago, Illinois 60690 - 0767 November 30, 1987 Mr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation
- u. s. Nuclear Re.guiatory Commission Washington, DC;,.' 20555
~ubject: Dresden station Unit 2 Hydrogen Uptake Data on General Electric Fuel
~c Docket No. 50-237 Reference (a):.. Letter from D. M.*Crutchfield to D.. L. Farrar dated April 7, 1983.
(b):
NEDC-31324 (Class I), "Hydrogen Water Chemistry Fuel Materials surveillance Program, Post Irradiation Examination of Fuel components After*one Cycle of Hydrogen Water Chemistry in Dresden-2, EPRI Research Project 1930-10, July 1986.
Dear Mr. Murley:
The referenced letter transmitted Amendment 75 to Provisional Operating License DPR-19 in support of Dresden 2 cycle 9 operation.
In addition to reload fuel licensing, the amendment authorized operation with hydrogen addition to the primary coolant. Section 2.1.6 of the safety Evaluation Report transmitted with the reference requested we supply the results of hydrogen uptake measurements taken on General Electric test assemblies exposed to the hydrogen enriched environment.
The results of these measurements after one cycle of hydrogen addition are provided in Attachment 1, which contains excerpts from the Reference (b) non-proprietary report prepared by General Electric for EPRI.
The data indicate there is no deleterious ~ffect on hydrogen uptake in Zircaloy cladding following one cycle.
Preliminary evaluations after the second cycle of hydrogen addition show similar results.
When a non-proprietary report is available, CECo will provide the results of the second inspection.
If you have any questions regarding this matter, please contact this office.
Very truly yours, C}a cP;.&JL~
J. A. S~~v ~~
Nuclear Licensing Administrator Attachments cc:
M. Grotenhuis - NRR NRC Resident ~nspector l
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NEDC-31324 Class I July 1986 HYDROGEN WATER CHEMISTRY-FUEL MATERIALS SURVEILL\\NCE PROGRAM POSTIRRADIATION EXAMINATION OF FUEL COMPONENTS AFTER ONE CYCLE OF HYDROGEN WATER CHEMISTRY IN DRESDEN-2 EPRI RESEARCH PROJECT 1930-10 Prepared by GENERAL ELECTRIC COMPANY 175 Curtner Avenue San Jose, California 95125 Authors B.
Cheng R. E. Blood (APPENDIX:
DRESDEN-2 FUEL ROD OXIDE THICKNESS DETERMINATION BY THE EDDY-CURRENT LIFT OFF TECHNIQUE by J. A. Kervinen)
APPROVED:
Reviewed By:CX.@ ~~
R. P. Tucker, Program Manager IDJC-Fuel Materials Surveillance kg;~Uf~P?J-6~
R. B. Adiillson, Manager Fuel Material Technology Prepared for
. E. Wood, Manager Core & Fuel Technology ELECTRIC POWER RESEARCH INSTITUTE 3412 Hillview Avenue Palo Alto, California 94303 EPRI Project Manager A. J. Machiels Nuclear Power Division NUCLEAR ENERGY BUSINESS OPERATIONS* GENERAL ELECTRIC COMPANY SAN JOSE. CALIFORNIA 95125 GENERAL. ELECTRIC
I I L~J NEDC-31324 LEGAL NOTICE This report was prepared by General Electric as an account of work sponsored by the Electric Power Research Institute, Inc.,
("EPRI").
Neither EPRI, members of EPRI, nor General Electric, nor any person acting on behalf of either:
a)
Makes any warranty or representation, express or implied with respect to the use of any information contained in this report, or that the use of ~ny information~ apparatus, method or process disclosed in this report may not infringe privately owned rights, or B.
Assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method or process disclosed in this report.
ii
NEDC-31324 ABSTRACT Postirradiation examinations of Dresden-2 fuel components were performed to investigate the effect of hydrogen addition to the reactor feedwater on the corrosion and hydriding performance of the Zircaloy components.
Included were fuel rods from three fuel bundles having different exposures to hydrogen water chemistry, as well as fuel rod spacers and water rods after one hydrogen water chemistry cycle.
The results indicate that the uniform and nodular/sheet oxide formed on the Zircaloy components are within the normal experience range of fuel components operated only under normal Boiling Water Reactor (BWR) water chemistry conditions.
The hydrogen uptake of the Zircaloy components is associated with the degree of corrosion, but not with the exposure history to hydrogen water chemistry.
Overall, the corrosion and hydriding behaviors of the Zircaloy fuel components were not influenced by exposure to one cycle of hydrogen water chemistry at Dresden-2.
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NEDC-31324 The hydride contents in both E4 and DS rods lures 41 and 42, both estimated me~ically to be less than
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The uniform oxide form~on the fuel rods (Zirc loy-2), spacers (Zt~aloy-4),
and water rods (Zircaloy.:'2~ nearly the same hickness, namely, 1.5~.0 µm with an average value of 2.0-2.5-...pm.
The nodular oxide found on the sp~~s had about the same thickness as t~~ed on the fuel rods.
However, in ~
comparing spacers with water rods, it can' e seen the Zircaloy-4 spacers ~
had thicker nodular oxide than the rods.
3.3 Hydrogen Content Analysis The hydrogen content in the nine fuel rods was measured using a LECO analyzer on samples taken at various axial elevations as shown in Table 1.
Duplicate samples were taken at some elevations to confirm the accuracy of the measure-ment.
Unirradiated archive samples were also analyzed' to provide a base line comparison. The hydrogen analysis on spacer and water rod samples was performed using either vacuum hot extraction or inert gas fusion (LECO) techniques.
The hydrogen gas content data are shown in Table 8 for the fuel rods and Table 9 for the spacers and water rods. It can be seen that the 0/1 cycle rods had a maximum hydrogen content of 34 ppm with the majority of the samples containing less than 23 ppm.
The 2/1 cycle rods had the highest hydrogen content of up to 125 ppm at the 40-in. location of the Al rod, which had the thickest corrosion oxide of the nine rods examined.
The majority of the hydrogen values are below -80 ppm.
The 3/0 cycle rods had hydrogen contents of 33-70 ppm.
These quantitative data were within the range estimated metallo-graphically, as described in Section 3.2.1.
Figure 43 shows the axial distribution of the hydrogen content in the fuel rods.
In this figure, the hydrogen content at each elevation is the average of the three rods from each bundle.
It can be seen that the 2/1 cycle rods had higher hydrogen contents than the 3/0 cycle rods.
However, only the Al rod in the 2/1 bundle had significantly higher hydrogen content, and this skewes the averages.
The other two rods, HS and G7, had hydrogen content within the same range as the 3/0 cycle rods.
The higher hydrogen content in the Al rod can be attributed to 3-49
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NEDC-31324 TABLE 8.
Hydrogen Content in Irradiated Dresden Fuel Cladding and Unirradiated Archive Cladding Samples. ppm Bundle Number Rod Number Axial Position (inches from bottom end plug) lSS {plenum) 127 120 97 62 40 20 s
(Bottom End Plug)
LYS4S7 {0/1)
LJGS32 {2/1)
F7 G6 G3 Al HS C7 61 27 72 89 23 28 10 SB 39 SB 17 18 16 63 39 73 16 67 20 18 11 87 34 S9 34 18 22 12S 33 46 23 13 lS 80 40 82 89 SB 26 74 Unirradiated Archive {ppm)
Tube A Tube B 14 lS 10 18 9
18 Total Ave. - 14 ppm 3-SO L.17366 (3/0)
AS 07 G7 63 42 48 43 70 so 38 38 40 33 67 37 44 42 3S SS l
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NEOC-31324 TABLE 9.
Hydrogen Content in Spacers and Water Rods. ppm Vacuum Hot Number Location Extraction LECO 1
Sideband El 22 Sideband OS 19 Corner AS 20 Corner Hl 42 2
Sideband El 22 Sideband OS 20 Corner AS 27 Corner Hl 22 5
Sideband El 24 Sideband OS 29. ~
Corner AS 33 Corner Hl 17 6
Sideband El 25 Sideband OS 3S
2S 40-in.
30 SO-in.
17 120-in.
14 Water Rod 05 20-in.
29 40-in.
44 SO-in.
19 120-in.
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0/1 Pretrraddla Uon Hydrogen 20 NEDC-31324 2/1 40 60 HYDROGEN, PPM 80 100 Figure 43.
Axial Variation of the Average Hydrogen Content in the 0/1, 2/1 and 3/0 Cycle Rods.
3-52
NEDC-31324 significantly higher nodular oxide coverage (Table 2) and thicker oxide (Table 4).
Thus, the one cycle exposure to hydrogen water chemistry following two cycles of exposure to typical B'WR water chemistry did riot affect the hydrogen uptake behavior of the fuel cladding.
The results indicate that the most severe scenario for hydrogen addition, as proposed by Cox, (S) whereby the fuel cladding would experience B'WR-type nodular corrosion and P'WR-type (higher) hydrogen pickup fraction, did not occur in the rods included in this surveillance program.
Accurate calculation of the hydrogen pickup fraction is not possible due to the presence of nodular oxide:
An alternate approach is to conservatively calcu-late the maximum hydrogen pickup fraction, by assuming that the nodular oxide does not contribute to the hydrogen uptake.
Only the uniform oxide thickness is used for the oxygen weight gain.
This is a reasonable approach since the hydrogen content values show little axial variation, particularly in the 0/1 and 3/0 rods.
In other words, the local hydrogen content at areas having low nodular corrosion is nearly the same as those locations having substantially higher nodular corrosion.
Moreover, the hydrogen content values in Table 8 indicate that the F7 rod had the highest values among the three 0/1 cycle rods, whereas the visual appearances and oxide thickness data, discussed above, show higher nodular corrosion on the G6 rod.
It thus appears that the contribution of nodular corrosion to hydrogen uptake is low when the total hydrogen content is low.
The contribution becomes significant when a sheet oxide (100% nodular oxide surface area coverage) rather than discrete nodular oxide is formed,
~s evidenced by the results for rod Al in Table 8.
The uniform oxide thickness on the 0/1 and 3/0 cycle rods is 2.0 and 10 µm, respectively.
The hydrogen contents in the fuel rods show only small varia-tions along the rod length or from rod to rod in each bundle.
Therefore, the overall average hydrogen content values are used to increase statistical significance.
The average hydrogen content in the 0/1 and 3/0 cycle rods is calculated to be 19 and 47 ppm, respectively.
After subtracting the average base concentration of 14 ppm in the archive sample, the maximum hydrogen pickup fraction is calculated to be 7.0 and 8.9% for the 0/1 and 3/0 cycle rods, respectively.
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.1 NEDC-31324 If the contribution of nodular corrosion to the hydrogen pickup in the 0/1 and 3/0 cycle rods is considered and if the hydrogen pickup fraction of the nodular oxide is assumed to be the same as that of the uniform oxide, the hydrogen pickup fraction of the 0/1 and 3/0 cycle rods show a large variability.
To use the 0/1 cycle rods as an example, the average nodular oxide coverages are calculated as S, 17, and 15% for the F7, G6, and G3 rods, respectively.
The nodules are, on average, ten times thicker than the uniform oxide.
Using a geometric factor of roughly 1/2 for the lens-shaped nodular oxide, the average oxide thickness of the nodular oxide is about 5 times higher than that of the uniform oxide.
The hydrogen pickup fractions are calculated to be S.7, 3.S and 1.2% for the F7, G6, and G3 rods, respectively.
Similar variation~ can be calculated for* the 3/0 cycle rods.
Such a large variation in hydrogen uptake for Zircaloy cladding in the same fuel bundle is considered to be unlikely.
It is thus more likely that the contribution of discrete nodular oxide to the hydrogen uptake of Zircaloy is indeed small.
Calculation of hydrogen pickup fraction for the 2/1 cycle rods requires con-sideration of individual rods, because of larger variations from rod to rod.
The data* in Table S indicate that rod HS had about the same hydrogen content as the 3/0 cycle rods and had only small axial variation.
Since the uniform oxide on the 2/1 and 3/0 cycle rods is nearly the same and the nodular oxide on the HS rod is.not heavy, the hydrogen pickup fraction of the HS rod is estimated to be the same as the 3/0 cycle rods.
The Al rod shows a significantly higher axial variation in the hydrogen content and nodular oxide coverage.
The hydrogen contents at the 40 and 97 inch locations are 125 and 65 ppm,. and the average oxide thicknesses are 37 and 17 µm, respectively.
The local pickup fractions are calculated to be S.l and S.2%, respectively.
The result showing that the 0/1, 2/1, and 3/0 cycle rods have nearly the same hydrogen pickup fraction suggests that the effect of hydrogen addition in the B"WR feedwater does not have a measurable effect on the hydrogen uptake of the fuel cladding.
The hydrogen content in the 0/1 cycle spacers and water rods averaged 26 and 24 ppm, respectively.
After subtracting the average baseline concentration of 14 3-54
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NEDC-31324 ppm, the average hydrogen uptake was 12 and 10 ppm for the spacers and the water rods, respectively, which were approximately double the average value for the 0/1 cycle fuel rods (5 ppm).
This is consistent with the fact that corro-sion occurs on both surfaces of the water rods and spacers, while only the outer surface of the fuel rods is subjected to waterside corrosion.
Therefore, the hydrogen pickup.fraction (per corroding surface) is nearly the same for the 0/1 cycle fuel rods, spacers, and water rods, again suggesting that the hydrogen addition to the feedwater does not have a measurable effect on the hydrogen uptake of the spacers and water rods.
The data further indicate that the hydrogen pickup fraction in B'WR.s is controlled by the degree of corrosion much more than by a minor alloy chemistry variation* in Zircaloy-2 and Zircaloy-4.
A comparison of the hydrogen content in the 0/1 cycle fuel rods, spacears, and water rods is given in Figure 44.
It can be seen again that the hydrogen content was very low (<41 ppm) in all cases.
Slightly higher hydrogen contents were seen at the 40 in. location, which can be attributed to slightly higher degrees of corrosion at that location.
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NEDC-31324 BUNDLE LY5457 ( 0/1)
FUEL ROD, F7 140 FUEL ROD, G6 FUEL ROD, *G3 120.
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Hydrogen Content as a Function of the Axial Location for the 0/1 Bundle Fuel Rods, Spacers, and Water Rods.
3-56
NEDE-31324 Section 4 CONCLUSIONS (1)
The uniform oxide and nodular/sheet oxide formed on the fuel rods exposed to one 18-month cycle of hydrogen water chemistry (0/1 bundle) or to one cycle of hydrogen water chemistry following two cycles of normal water chemistry (2/1 bundle) are within the normal experience range of BWR fuels operated under only normal water chemistry,conditions.
(2)
The uptakes of hydrogen by the rods exposed to one cycle of HWC (0/1 and 2/1 bundles) are low and fall w~thin the experience of General Electric fuels operated under only normal water *chemistry conditions.
(3)
Overall, the corrosion and hydriding performances of fuel components were not influenced by the addition of hydrogen into the feedwater during Cycle 9 operation at Dresden 2.
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 Docket Nos. 50-237 50-249 November 25, 1987 Mr. Cordell Reed, Senior Vice President Nuclear Operations Commonwealth Edison Company Post Office Box 767 Chicago, Illinois 60690
Dear Mr. Reed:
SUBJECT:
DIAGNOSTIC EVALUATION AT THE DRESDEN NUCLEAR POWER STATION ON AUGUST 17-28, 1987 This letter forwards the report of the Diagnostic Evaluation performed by a U.S. Nuclear Regulatory Commission (NRC) evaluation team over the period August 17 to August 28, 1987, involving activities authorized by NRC Operating License Numbers DPR-19 and DPR-25, for the Dresden Nuclear Power Station.
This evaluation was conducted by a team of NRC headquarters and regional inspectors, and team leadership and support was provided by the Office for Analysis and Evaluation of Operational Data (AEOD).
As you are aware, this is a new NRC assessment tool that is intended to provide an independent assessment of licensee performance, and as such, its principal focus is on safety performance and not compliance with regulatory requirements.
Following the conclusion of the onsite evaluation, the findings were discussed at an exit meeting with you and members of your staff on September 23, 1987.
Additionally, you and other Commonwealth Edison Company officials met with me and members of my staff on October 28, 1987 to describe your overall plans for improving the safety performance at Dresden.
The NRC effort involved an assessment of Dresden's performance including personnel attitudes toward safety, management involvement in station operations, and the effect of recent improvement initiatives on station performance and personnel attitudes; and to determine, to the degree possible, the fundamental or probable causes that may underlie performance problems.
Particular attention was directed on the conduct of operations and the interfaces between operations and the functional areas of maintenance, surveillance ~esting, operator training, quality programs, and radiological controls.
Additionally, the programs for assuring quality in these areas were reviewed to determine their effectiveness.
Despite past and present improvement programs, a number of major weaknesses were identified.
These included maintenance (particularly of motor-operated valves), inservice testing (IST), communication, and operator training.
Because of a history of poor maintenance and testing practices, the team concluded that wear, aging, and the resultant accumulation of equipment deficiencies could cause system/component unreliability.
Further, the team found that communication was poor across the organization and that the operator requalification program remains unsatisfactory.
In addition, an immediate
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Mr. Cordell Reed safety concern associated with excessive operator overtime was identified by the team, and corrective actions were promptly taken by station management.
Based upon the extensive team assessment, both onsite and through subsequent analysis, it was concluded that the fundamental or root causes of Dresden's frequently low and fluctuating performance history were:
(a) Dresden had not received strong and indepth corporate attention in the past, (b) an attitude and approach existed that had not been directed at achieving or maintaining a high standard of safety performance, and (c) past improvement initiatives had been largely a reaction to fin9ings by INPO and the NRC, and had not been developed in a specific and complete way to overcome Dresden deficiencies.
In addition, major weaknesses in maintenance, inservice testing, communications and training were significant contributors.
The evaluation results which include: (1) major findings and conclusions, (2) specific findings and conclusions, and (3) root cause determinations are included in Section 2 of the enclosed report.
Section 3 of the report provides the detailed evaluation findings.
Some of these items may be potential enforcement findings.
Any enforcement actions will be identified by our Region III Office.
In summary, Dresden's performance is currently judged to be on the low side of average with a slowly improving trend.
However, confidence is not high that, without additional major corporate involvement, Dresden's performance will show significant and sustained improvement.
This view is due to Dresden's fluctuating past performance history, the weaknesses in the present improvement initiatives, a lack of improvement initiatives in several critical areas, and limited financial and human resources.
During the week of November 16, 1987, I met with senior NRC managers and discussed the results of this Diagnostic Evaluation as well as other current information concerning the regulatory and operational performance of Dresden.
During our discussions it became apparent that the overall results of this
-Diagnostic Evaluation substantiated NRC senior management concerns that the Commonwealth Edison Company needs to make a substantial commitment to additional improvement initiatives. These initiatives are necessary in order to assure significant and sustained improvements in Dresden's safety performance.
I request that you evaluate the enclosed report and, that within 60 days of the date of this letter, you provide my office with an integrated improvement program with schedules, goals, objectives, action plans with milestones, and tracking and assessment methods.
This program should not only address the major weaknesses and root causes identified by the Diagnostic Evaluation, but should also include provisions for identifying and correcting other probable causes that may underlie performance problems.
Given the numerous weaknesses identified with your current and past performance programs, your response should specifically describe your plans and methods for providing greater assurance that this program will result in a sustained overall improvement in the safety performance at Dresden.
Mr. Corde 11 Reed
- In accordance with 10 CFR 2.790(a), a copy of this letter and the enclosure will be placed in the NRC Public Document Room.
Should you have any questions concerning this evaluation, we would be pleased to discuss them with you.
Enclosure:
Diagnostic Evaluation Team Report for Dresden Nuclear Power Station
~ibution (w/encl)
AEOD R/F Distribution (w/o encl)
ELJordan CJ He ltemes DOA R/F RLSpessard DEIIB R/F SDRubin HBailey RPerch RFreeman RLloyd AHowell DAllison
. JTaylor JJohnson WMTroskoski OSP TEMurley ABDavis, RIII RMartin, RIV JMartin, RV NGrace, RII WRusse 11, RI
~SEE PREVIOUS CONCURRENCE Sincerely, Original s.ign&d by Victor Ste:lLO!
Victor Stello, Jr.
Executive Director for Operations OFC
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- ELJordan DATE :11/5/87
- 11/5/87
- 11/ /87
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- 11/ /87
- 11/5/87 OFFICIAL RECORD COPY
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