IR 05000327/1986014
| ML20138C218 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/19/1986 |
| From: | Ross W, Stoddart P NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20138C197 | List: |
| References | |
| 50-327-86-14, 50-328-86-14, NUDOCS 8604020401 | |
| Download: ML20138C218 (7) | |
Text
I
,
UNITED STATES -
[QUG
.
'
o NUCLEAR REGULATORY COMMISSION
<
[
",
REGION ll y
j 101 MARIETTA STREET,N.W.
'c ATLANTA, GEORGI A 30323 t,
b..... #g N4R 2 4 lS86 Report Nos.: 50-327/86-14 and 50-328/86-14 Licensee: Tennessee Valley Authority 6N38 A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Docket Nos.:
50-327 and 50-328 License Nos.: DPR-77 and DPR-79 Facility Name:
Sequoyah 1 and 2 Inspection.Cenducte February 12-14, 1986 Inspector:
-
N W. J. Rofs'
.
Da'te Signed N#
-Approved by:
,
P. G.'itoddart, Acting Section Chief Date Signed Division of Radiation Safe.ty and Safeguards SUMMARY Scope: This routine, unannounced inspection entailed 16 inspector-hours onsite in the area of plant chemistry.
Results: No violations or deviations were identified.
8604020401 860324 PDR ADOCK 05000327 G
,
e-
>
.
.
-REPORT DETAILS 1.
Persons Contacted Licensee Employees
- P. R. Wallace, Plant Manager
- L. M. Nobles, Superintendent of Operations and Engineering T. Hughes, Scheduling / Engineering R. Mayfield, Water Treatment / Operations J. A. McPherson, Inservice Testing Supervisor / Engineering J. D. Pierce, Chemistry Lab Supervisor / Chemistry J. W. Profitt, Engineer / Chemistry
- W. L. Williams, Chemistry Unit Supervisor Other licensee employees contacted included chemistry technicians.
NRC Resident Inspectors K. Jenison L. Watson
- Attended exit interview 2.
Exit Interview The inspection scope and findings were summarized on February 14, 1986, with those persons indicated in paragraph 1 above. No dissenting comments were received from the licensee. The licensee did not identify as proprietary any of the materials provided to or reviewed by the inspector during this inspection.
3.
Licensee Action on Previous Enforcement Matters This subject was not addressed in the inspection.
4.
Unresolved Items Unresolved items were not identified during the inspection.
5.
Plant Chemi'stry This inspection was performed to assess the layup protection against degradation of the secondary water system, especially the steam generator, that had been provided to the two Sequoyah units since they were shut down in August 1985. Additionally, the inspector evaluated the progress that had been made to upgrade the secondary water system and the licensee's water chemistry control program.
.
_
-
.
.
a.
Layup of Units 1 and 2 Both Sequoyah units were shut down the latter part of August 1985; Unit-1 had completed its third fuel cycle that had begun in April 1984 and Unit 2 was in the middle of its Cycle 3 that had started in December 1984.
The licensee had tentative plans to restart both units within the next-three to four months.
During the six months since the plant was shut down, major modifications were made on the steam generators in both units.
Feedwater heaters numbers 1 and 2 were replaced.in both units, the tube bundles in the Unit 1 moisture separator reheaters were replaced, and heat exchangers were added to the steam generator blowdown recovery system of Unit 1.
In addition, the usual activities related to a refueling outage were performed on Unit 1, including sludge lancing the steam generators and inspecting the steam generator tubes.
In order for the above activities to be performed, there was little opportunity for the secondary systems of either unit to be protected against air, and accompanying oxidation of carbon steel components, by employing wet layup with chemically controlled, deaerated water..
During most of the past six months, both the low pressure (condensate /
feedwater) and high pressure (extraction steam and drain) lines were drained and open to air. The steam generators in Unit I were exposed to the following sequence of environments:
drained and open to air while being inspected and sludge lanced; filled with deionized water to the. top of the tube bundles as radiation protection while modifications were made to the "J" tubes on the feedwater rings; filled and treated
.with hydrazine and ammonia ( AVT control chemistry) and placed in a recirculating _ mode for several weeks; drained below the feedwater ring again so that work could be performed on the feedwater regulating valves; refilled with AVT chemicals; and recirculation started again approximately February 1, 1986.
The licensee planned to drain the water below the feed rings once more to perform additional valve repairs before startup of this unit.
After Unit 2 was shut down, the steam generators were rinsed (by bleed and feed p'ocedures using deionized water), filled with deionized water until again drained below the feedwater rings so that modifications could be made to the feedwater regulating valves.
Subsequently, the steam generators were filled with chemically treated water and placed in the recirculating mode. (In the recirculating mode, water is cycled by a recirculating pump from a tap on the feedwater inlet to another tap on the blowdown line, so that the water inventory of the steam generator is continually in motion.)
During -all of the steam generator repair work, the licensee could not maintain an inert (nitrogen) atmosphere to minimize oxidation of the internal components because workers had to enter the vessel.
.
The inspector reviewed three of the licensee's. procedures that provide guidance and criteria for implementing wet, chemistry-controlled, layup whenever possible.
Procedure TI-19, Chemical Feed Controls, Revision 16 - (December 23, 1985) specified the method of injecting ammonia and hydrazine into the condensate /feedwater train and into the steam generator so as to control pH (pH of 8.8 - 9.2 in the condensate and pH of 10 in the steam generators) and to eliminate dissolved oxygen.
Procedure TI-37, Chemical Laboratory Log System, Rev. 23 (August 30, 1985), specified the limits on chemistry variables that must be controlled to prevent corrosion by water in (1) the Condensate Storage Tanks (CST) that are used for condensate makeup as well as for refilling the secondary water system whenever it is draired, (2) in the hotwell, (3) in the feedwater, and (4) in the steam generator blowdown during plant startup.
Finally, Procedure SQE-22, Sequoyah Nuclear Plant Chemistry Program, Revision 2 (August 1985) *was also reviewed.
This procedure was an upper-tier document that defined the licensee's overall secondary water chemistry program.
As mentioned earlier, the licensee was not able to implement the portions of-the water chemistry program that related to layup except for relatively brief periods when the steam generators could be closed up. Consequently, neither the licensee nor the inspector could predict the txtent of corrosion that occurred in the secondary system during the past six months.
One indication would be the amount of iron and copper oxides collected on the condensate polishers during the pre-startup and startup cleanup phases and the amount of sludge found during the next sludge lancing of the steam generators of both units.
Since the original copper alloy tubes remained in four of the six feedwater heaters in both units, some copper could be included ir. the sludge in the future.
The inspector was informed that the startup schedule for the first unit to restart (Unit 2)
allowed for long-cycle cleanup of the hotwell/ condensate /feedwater for four days before reactor heatup and for approximately two weeks between the time the secondary system was evacuated and when the Unit entered Mode 4 (Tavg > 200 F).
The licensee planned to use this time to achieve the level of purity of condensate and feedwater required by the secondary water chemistry program.
The licensee continued to place " chemistry holds" on power ascension at the 5% and 30% power levels to ensure that the feedwater was not out of specifications as the result of impuritier in the low pressure and high pressure systems.
These precauticns were considered to be adequate for protecting the steam generatcrs against additional corrosion after startup.
Summary Although the licensee had procedures to protect the secondary water system against degradation through corrosion during an extended outage, these procedures could not be implemented fully during the scheduled outages for either unit. The inspector considered this situation to
r
..
.
.
reflect a deficiency in the licensee's water chemistry program that should be addressed. (Tne inspector was aware that a similar study was already underway at the licensee' Browns Ferry plant.)
b.
Changes in Plant Design The 1icensee used this outage period to-implement several major changes to the plant as discussed below.
(1) Water Treatment Plant As was noted previously (Inspection Report 50-327,328/85-18),the demand for deionized water for both units exceeded the capacity of the plant's original water treatment plant, so that temporary facilities had to be installed onsite to augment the production of water for such large-scale uses as condensate makeup and regeneration of the deep-bcd condensate polishers.
Neither of these sources was designed to produce the very high quality water (~0.1 umho/cm conductivity) needed to maintain corrosion-free environments in the secondary water system.
Consequently, the licensee constructed a dual-train water treatment plant during t.he last year to replace the two plants that were used before the plant shutdown.
The new plant was operating, but was not completely automated as planned. The capacity of the new plant (a total of ~350 gpm for both. trains) was considered by the licensee to be adequate for all ' anticipated needs. The new plant had two other advantages over the ones previously used.
Higher purity product was produced because the cleanup components were expanded beyond those that were in the original plant. Also, the down-time needed to regenerate the ion-exchange demineralizers was reduced by a factor of ten.
The inspector was informed that additional work was needed to
,
maximize the usefulness of the Demineralized Water Storage Tank l
(DWST) for storage of the product of the new water treatment
plant.
During this inspection, the DWST was bypassed; i.e., the product of the water treatment plant was pumped directly to the condensate storage tank (CST) and to other storage tanks and headers in the primary and secondary water systems. This abnormal mode of operation was to be terminated before plant restart. The.
,
licensee also had plans for a longer-term modification whereby the water in the DWST would be recycled back to the clearwell of the water treatment plant and then treated again.
Continual circulation would reduce buildup of solids in the DWST and enhance the purity of this water.
The inspector established that a training. program had been initiated to qualify Auxiliary Unit Operators (AV0s) on the operation of the new water treatment plant.
Four AU0s participated in startup of this plant and were considered to be well qualified.
.
.-
._
,
.-
.,,,.
7,.r
-. _ _.. _ _ -,,., _.,. _.,
,., _,,.,,,.. _,,., -, -
,.., _ _,, _,,. ~,,, _., _ _. <. - ~ _
.
_
-
.
. ~
(2) Retubing Feedwater Heaters During the first two fuel cycles for both Sequoyah units several hundreds of ~ pounds of iron oxide and copper oxide sludge were transported into the steam generators, and indications of denting of steam generator _ tubes were observed.
Studies have shown that-the presence of copper aggravates the denting phenomenon, as well as causing other corrosion mechanisms. Consequently, the licensee began a program to replace the copper alloy tubes in the feedwater heaters to minimize transport of copper. (The main condenser _also had copper alloy tubes; however, the condensate polishers should remove any soluble or solid copper species that may be corroded or er6ded from the condenser tubes).
This program was begun during this outage 'when two of the original heaters were replaced with
-
304 stainless steel heater tubes ' that were originally fabricated for the licensee's Hartsville plant. The remaining copper alloy heater tubes in both Sequoyah units were scheduled to be replaced during the next refueling outages.
(3) Steam Generator Blowdown Recovery System As discussed in an earlier report (Inspection Report 50-327/84-16, 50-328/84-16 dated August 7, 1984) the blowdown systems of the two Sequoyah units differed in that the blowdown. from Unit I was pumped through a heat exchanger to the condensate line upstream of the condensate polishers, while blowdown from Unit 2 was. cooled by means of a flash tank.
The licensee found that ~50% of the chemical impurities in the Unit 2 blowaown was transferred with the steam from the flash tank so that they were cycled back to the feedwater drain tanks without being cleaned by the condensate polishers.
Consequently, the Unit 2 blowdown system was remodeled; i.e., a three-stage heat exchanger was added during this outage to replace the flash tank,- and a blowdown demineralizer was to be added during the next refueling outage.
(4) Retubing of the Unit 1 Moisture Separator Reheater During this outage the stainless steel tubes in the Unit 1 MSRs were replaced with more corrosion-resistant stainless steel to reduce the degradation rate. The inspector was informed that the new tube bundles were precleaned by flushing with deionized water until the concentration' levels of fluoride and chloride' ions were reduced to acceptable (~20 ppb) levels.
It was likely that additional amounts of these corrosive species would be detected when this unit becomes operational and the MSRs are subjected to steam.
c.
Results of Unit 1 Steam Generator Inspections During this refueling outage for Unit 1 the licensee removed approximately 1200 pounds of iron oxide / copper oxide sludge from the h
..
.-
.
four steam generators. Subsequently, the steam generator tubes were eddy current tested, and one leak was identified. CThe leak was caused by failure of the tube in the transition region of the 'U-bend' and was not attributed directly to chemistry control). All of the tubes in
~ Row 1 of each steam generator were plugged as a preventive measure against additional leaks in the 'U-bend' region.
d.
Quality Control of Non-Radiological Analyses The inspector reviewed the elements of the licensee's quality control program as defined in Procedures SQE-22 and TI-20 for non-radiological analyses. This program included tracking the quality and shelf-life of reagents, calibrations and functional checks of laboratory equipment, and control of analytical results.
The inspector established that several overlapping and cross checking methods were used to control the precision and accuracy of analytical results. Within the Chemistry Unit these activities were the responsibility of the Engineering Section Supervisor and the Instrument Engineer, e.
Staffing and Training One of the licensee's goals in its upgrading program was to train the staff'of the Chemistry Unit so that it attained a higher level of performance.
The inspector was informed that the Chemist Unit was fully staffed with 10 Engineers, a Laboratory Supervisor and 30 Laboratory Analysts. The Laboratory Analysts were divided into six crews, one of which, on a
~ rotating basis, performed the duties of specialists (e.g.,
QC, 1nstrumentation, post-accident sampling).
Many of the Laboratory Analysts were hired during the last year; consequently, the licensee was required to bring these people through the entire training program both at the TVA Training Center and on-the-job. This training was not expected to be completed before the units restart.
There was to be continuing emphasis on system training through seminars as well as formal lectures.
The Chemistry Unit Supervisor and his immediate supervisor were both qualified as Shift lechnical Advisors.
f.
Summary No violations or deviations were identified during this inspection.
The inspector believed that the Chemistry Unit was capable of performing the responsibilities defined in its water chemistry program; however, increased attention should be give to expediting the training of the newer Laboratory Analysts.
i