ML20196K612
| ML20196K612 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 06/30/1988 |
| From: | Robert Williams PUBLIC SERVICE CO. OF COLORADO |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| P-88144, NUDOCS 8807070050 | |
| Download: ML20196K612 (7) | |
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O Public Service ~
- =t h P.o. Box 840 D"', co so20m June 30, 1988 Fort St. Vrain Unit No. 1 R.O. WILLIAMS, JR.
P-88144 7UYEA ADONS U. S. Nuclear Regulatory Commission Attn:
Document Control Desk Washington, D.C. 20555 Docket No. 50-267 SUBJ ECT: Actions to Mitigate Moisture Ingress Into the Primary Coolant System
REFERENCE:
- 1) PSC Letter, Williams to Document Control Desk, dated April 16, 1987 (P-87136)
Gentlemen:
On April 16, 1987, Public Service Company of Colorado (PSC) submitted a letter to the NRC describing the actions taken by PSC to mitigate moisture ingress into the primary coolant system during the calendar year of 1986.
That letter (Reference 1) described the Fort St. Vrain Improvement Comittee, the actions taken by PSC to mitigate moisture ingress into the primary coolant system and the actions pending to mitigate moisture ingress into the primary coolant system.
This letter and its attachments provide the NRC with the 1987 annual report.
The 1987 report consists of the following attachments: - Fort St. Vrain Improvement Committee Organization and 1987 Activities - January 1, 1987 to May 31, 1988 PCRV MoistJre Levels related to Plant Outages and Upsets Due to the evaluation of Fort St. Vrain's future operation currently in process, most of the possible future actions described in the 1986 annual report (Reference 1) remain on a temporary "hold".
While the "hold" on these actions represents a temporary delay, the results of the actions already taken by the Comittee, as shown in Attachments 1 and 2, demonstrate PSC's commitment to the dependable operation of Fort St. Vrain.
The Committee believes that its actions have continued to result in significantly lower levels of moisture during the 1987 circulator and fire outages as well as 1987 and 1988 transients due to plant upsets. This has continued to result in a shorter non-nuclear dryout period and a shorter time for the 0\\
resumption of nuclear operations.
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'o P-88144 June 30,'1988 If you.have any questions please contact Mr. M.H. Holmes at (303) 480-6960.
Very truly yours, R. O. Williams, Jr.
Vice President Nuclear Operations R0W/AHW:dvd Attachments cc: Regional. Administrator, Region IV Attention: Mr. T. F. Westerman, Chief Projects Section B Mr. R.E. Farrell Senior Resident inspector Fort St. Vrain l
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P-88144 Page 1-FORT ST. VRAIN IMPROVEMENT COMMITTEE ORGANIZATION AND 1987 ACTIVITIES
.The' Fort St. Vrain Improvement Comittee consists of the following nembers:
Mr. R.F. Walker, Chairman and CEO, PSC and Improvement Comittee Chairman Mr. R.0. Williams, Vice President Nuclear Operations Mr. H.L. Brey, Manager, Nuclear Licensing and Resource Management Division Mr. D.W. Warembourg, Manager, Nuclear Engineering Division
- Mr. P.F. Tomlinson, Manager, Quality Assurance Division The purpose of the Fort St. Vrain. Improvement Comittee is to fonslate and review proposed technical improvements to enhance the operation and reliability of Fort St. Vrain.
The previous actions promulgated by this comittee have significantly contributed to the reduction in the number and severity of moisture ingress events.
Of note are the 1987 outages for environmental qualification of electrical equipment important to safety, helium circulator replacement and fire recovery during which time unprecedented low levels of moisture were maintained such that upon the start of the.non-nuclear dry-out period, the moisture level was less than 100 ppm.
Previous experience normally involved starting non-nuclear dry-out with a level of moisture an order of magnitude higher.
PSC actions to mitigate moisture ingress have helped improve plant availability as exemplified by achievement in March 1988 of a FSV record'for the highest monthly electrical generation.
During the past reporting period, PSC has concentrated its efforts on actions to reduce moisture ingress and to improve the reliability and performance of the helium circulators.
These actions were:
Reduced moisture ingress into the PCRV during plant 1.
Training outages and transient conditions was effected by enhanced training:
A.
Lesson plans were developed and implemented to provide enhanced training for the licensed ope,ators.
Specific automatic circulator trips and loop shutdowns which are related to moisture ingress were emphasized during classroom training.
Examples of these trips included buffer-mid-buffer circulator trip, hot reheat steam activity high l
P-88144 Page 2 alarm, reactor pressure high and high moisture trips. Task performances'for circulator trips and loop shutdown events were performed by the licensed operators.
B.
Lesson plans were developed and -tmplemented to provide enhanced training of the equipment and reactor operators on moisture ingress mechanisms and the design and operation of the dew point moisture monitors and their system.
This training includes information on sampling points, moisture ingress points, dewpoint measurement and-response to moisture monitor trips.
2.
Helium Circulator Improvement In July 1987, as a result of excessive shaft wobble indications and a helium interspace leak, helium circulator S/N C-2101 was removed from the PCRV.
Inspection of this machine at General Atomics in San Diego showed l
l damage to internal parts that may have been the cause of the wobble indications. The damage resulted from the failure of some fasteners in the steam turbine end of the helium circulators as reported to the NRC in PSC letter, Williams to Calvo, dated January 22, 1988, P-88019.
Failure of the fasteners has been l-attributed to Caustic Stress Corrosion Cracking (CSCC) due to high levels of sodium in the reheat steam system during previous operation of FSV.
As a result of this event, PSC is improving the future reliability of the helium circulators through the following actions:
To improve performance of the helium A.
Material Change l
circulators, most of the fasteners in the steam end of the four installed helium circulators wi ! '. be replaced with fasteners of CSCC resistant materials during the circulator refurbishment outage which is scheduled to start in July 1988.
To reduce the possibility of CSCC effects on the steam I
turbine end of the helium circulators and on other components in the secondary coolant system, the water chemistry program for the condensate /feedwater systems has been revised to significantly reduce the allowable sodium limits during operation above 30% reactor power.
Water chemistry restrictions have also been placed on auxiliary boiler steam.
Based upon a review of past B.
Additional Inspection operating history and experience, most of the fasteners in
P-88144 Page 3 the steam' turbine of the' helium circulators will be replaced after 40,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of circulator operation.
_ This requirement has been added to the current 10 year disas',embly and inspection program for the helium circulators.
C.
Monitoring for Degradation - Until an improved monitoring system can be developed to monitor the wobble of the shaft-in each helium circulator, daily monitoring of the existing shaft wobble system has been scheduled to assure early detection of circulator degradation and/or performance.
3.
Future Circulator Enhancaments The Improvement Committee is continuirg to investigate long term future improvements to the helium circuletors.
Of primary concern is the present high pressure bearing water system which is used to lubricate the FSV circulator bearings.
Since this water system is still the source of moisture _ ingress into the PCRV resulting from plant transients, replacement with a non-water device, such as a magnetic bearing, is a possible solution.
Proceeding in this direction, PSC has:
A.
Co-funded with EPRI - The design, procurement and testing of a catcher bearing test rig. A catcher bearing is required to hold the circulator shaft and to allow coastdown of the circulator's turbine and compressor following failure of the power supply associated with the magnetic bearings. This type of bearing has been proposed for use in the MHTGR circulators and for adaptation to the FSV helium circulators by the James Howden Company of Scotland.
B.
Co-funded with EPRI - The preparation of the specification for electronic equipment qualification of control cables associated with the magnetic bearings.
C.
A small effort for evaluating a journal bearing associated with the proposed magnetic thrust bearing is also underway. to this letter summarizes the plant upsets and outages from January 1,1987 to May 31, 1988 and their related primary coolant moisture levels.
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P-88144 Page 1 JANUARY 1, 1987 to MAY 31, 1988 PCRV M0ISTURE LEVELS RELATED TO PLANT OUTAGES AND UPSETS (From FSV Monthly Power History Reports and FSV Daily Status Sheets)
PLANT OUTAGES Following PCRV T-G Plant Outage Moisture Level On-Line Date Startup on '04/17/87 after 100 PPM Max and 04/30/87 11 months shutdown 1 PPM by 05/05/87 for EQ work Startup on 09/30/87 after 40 PPM Max Aborted by Hydraulic 2 months shutdown for.
- 011 Fire on 10/02/87 replacement of Helium Circulator Startup on 12/11/87 40 PPM Max and 12/15/87 after-2 months shutdown 15 PPM by 12/15/87 for-recovery from Hyd.
fire Startup on 04/22/88 24 PPM 04/23/88 after 2 weeks shutdown (0 PPM, 04/27/88) for replacement of CW expansion joints l
Startup on 05/18/88 200 PPM 05/26/88 after 2 weeks shutdown (0 PPM, 05/31/88) for repairs 6
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PLANT UPSETS PCRV T-G Plant Upsets-Moisture Level On-Line Date
'D' Helium Circulator 225 PPM Max and 12/21/87 Trip on 12/15/87 0 PPM by 12/23/87
'C' Helium Circulator 26 PPM Max and Stayed on-line Trip ' on 03/29/88 0 PPM by 03/31/88
'C' Helium Circulator 217-PPM Stayed on-line trip on 04/23/88 0 PPM, 04/27/88
'B' Helium Circulator 5-7 gallons up 05/26/88 Trip on 05/06/88
'A' Circulator followed by Hi HRH Scram Shaft Five' random Helium No moisture ingress Not Applicable Circulator Trips Loop I Shutdown on 6 PPM Max and 02/13/88 02/10/88 O_ PPM by 02/16/88 Loop II Shutdown on No moisture Ingress Not Applicable High Radiation on 05/04/87 200 MW Frequency 3 PPM 04/06/88 Swings followed by (1 PPM,04/06/88)
Manual Scram on 04/04/88 Three Reactor Scrams No moisture Ingress Not Applicable Two T-G Trips No moisture Ingress Not Applicable i
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