IR 05000309/1987003
| ML20214J501 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 05/14/1987 |
| From: | Lester Tripp NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML20214J482 | List: |
| References | |
| 50-309-87-03, 50-309-87-3, NUDOCS 8705280074 | |
| Download: ML20214J501 (8) | |
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U.S. NUCLEAR REGULATORY COMMISSION
REGION I
Docket / Report: 50-309/87-03 License:
DPR-36 Licensee:
Maine Yankee Atomic Power Inspection At: Wiscasset, Maine Dates:
March 17, 1987 to April 27, 1987 Inspectors:
Cornelius F. Holden, Senior Resident Inspector Ri rd Freudenberger, Resident Inspector Approved:
N d. /V 87 pL.Tripp(Chief,ReactorProjectsSection3A Date Summary:
Inspection on March 17 to April 27, 1987 (Report No. 50-309/87-03)
Areas Inspected:
Routine resident inspection (242 hours0.0028 days <br />0.0672 hours <br />4.001323e-4 weeks <br />9.2081e-5 months <br />) of the control room, accessible parts of plant structures, plant operations, radiation protection, physical security, fire protection, refueling operations, maintenance and surveil-lance.
Results:
No violation were noted. Two problems during the refueling outage are discussed in section 4.f (inadvertant recirculation actuation) and section 9 (re-fueling machine contact with the light ring).
8705280074 870519 PDR ADOCK 05000309 G
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DETAILS 1.
Persons Contacted Within this report period, interviews and discussions were conducted with various licensee personnel, including plant operators, maintenance technicians and the licensee's management staff.
2.
Summary of Facility Activities At the beginning of the report period the plant was operating at 75 percent power in cold leg temperature (Tc) coastdown.
Tc coastdown operation con-tinued until March 28, when the reactor was shut down for a refueling outage.
The plant was in a refueling outage until the end of the report period.
3.
Follow up on Previous Inspection Findings a.
(Closed) Unresolved Item (309/82-04-05) Location of high range radiation monitor inside containment.
The licensee relocated the high range radi-ation monitor inside containment to address the concern that the high range system need to view a large portion of containment.
The inspector reviewed the engineering design change package that relocated the sensor and observed that the relocation was completed.
b.
(Closed) Inspector Follow Item (309/85-32-01) Licensee actions regarding increased radiation levels from failed fuel.
The inspector reviewed the actions taken during the refueling outage to identify and replace the failed fuel pins. This inspection is documented in section 4.f below.
c.
(Closed) Inspector Follow Item (309/86-16-01) Pressure Values on Emer-gency Action Level chart are not specified as to gage or absolute. The licensee corrected the confusion over the pressure indication to make all values correspond to control room indication.
All charts were changed to indicate pressure is in absolute units.
4.
Routine Periodic Inspections a.
Daily Inspection During routine facility tours, the following were checked: manning, ac-cess control, adherence to procedures and LCO's, instrumentation, recor-der traces, protective systems, control room annunciators, radiation monitors, emergency power source operability, control room logs, shift supervisor logs, and operating orders, b.
System Alignment Inspection Operating confirmation was made of the service water and primary compon-ent cooling systems.
Operational status was verified with regard to the system's capability to perform their support functions to the residual
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- heat removal (RHR) system while maintenance activities were performed on portions of the systems.
Accessible valve positions and status were examined.
Power supply and breaker alignment were checked.
Visual in-spection of major components was. performed. Operability of instruments essential to system performance was assessed.
No discrepancies were identified.
c.
Biweekly Inspections During plant tours, the inspector observed shift turnovers, chemistry sample results and the use of radiation work permits and Health Physics procedures.
Area radiation and air monitor use and operational status were reviewed.
Plant housekeeping and cleanliness were evaluated.
d.
Plant Maintenance The inspector observed and reviewed maintenance and problem investigation activities tn verify compliance with regulations, administrative and maintenance procedures, codes and standards, proper QA/QC involvement, safety tag use, equipment alignment, jumper use, personnel qualifications, radiological controls for worker protection, fire protection, retest requirements, and reportability per Technical Specifications.
The inspector reviewed maintenance procedure 5.7.1 Appendix A, "Prepara-tion of Reactor Vessel Closure Studs, Nuts, Washers and Internal Threads for Closure Studs in the Reactor Vessel" Rev. 17, 3-18-87 and observed maintenance activities associated with the preparation of the reactor vessel closure studs, nuts and washers for reactor vessel head installa-tion.
The inspector determined that the procedure was adequate to control the work being performed.
The work was performed in accordance with the procedure and the tools and materials used were as specified.
The lic-ensee maintains three sets of 27 reactor vessel closure studs, nuts and washers.
During any operating cycle two sets are in use and the third set is cleaned, inspected (using non destructive testing techniques),
and prepared for its next use.
The cleaning involves the removal of a phosphate coating (Parkerizing) that is put on the components to prevent corrosion.
The coating is reapplied prior to reinstallation.
During the outage, the set that was in use during the previous cycle and will be used again this cycle is cleaned, visually inspected, and pre-pared for reinsta11ation. One point of the visual inspection is to en-sure that the Parkerizing is still intact.
There was no involvement by the Quality Assurance Department (QAD) in the inspections that were per-formed on this set of studs, nuts and washers.
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The inspector questioned this lack of QAD involvement in the inspection of the studs, nuts and washers.
The licensee responded by performing an inspection of the components that had been prepared for installation and the initiation of a procedure change request (PCR) to maintenance procedure 5.7.1, Appendix A, which established a QC hold point to allow a visual inspection of the components after cleaning.
The inspector had no further questions.
e.
Surveillance Testing The inspector observed parts of tests to assess performance in accordance with approved procedures and LCO's, test results, removal and restoration of equipment, and deficiency review and resolution.
Reactor trip breaker timing tests were performed to gather "as found"-
data for maintenance to be performed on the breakers during the outage.
Portions of the tests were witnessed and the results reviewed.
All re-sults were within specification.
Post maintenance testing will be re-viewed when completed.
f.
Recirculation Actuation Signal Initiation The licensee inadvertently initiated a "B" train recirculation actuation signal (RAS) on April 14.
RAS is the recirculation mode of the emergency core cooling system when the suction for core cooling is shifted from the Refueling Water Storage Tank to the containment sump.
For an RAS initiation to occur the level in the refueling water storage tank (RWST)
has to be less than 100,000 gallons and the RAS block enable signal has to be de energized.
Since the plant was in a refueling shutdown with the reactor cavity flooded, the level in the RWST was less than 100,000 gallons.
To allow work to be performed on a "B" train letdown-system valve, the power supply to "B" safety injection actuation system cir-cuitry was de-energized.
This de-energized the RAS block enable signal resulting in a "B" train RAS actuation.
The control room operator quickly reset the condition and repositioned the required valves.
The impact on the plant was minimal because of the large number of systems tagged out for the outage.
The cause of the RAS initiation was a breakdown in communications and inadequate research into the tagging request by the cognizant engineer.
Although a Functional Test Coordinator had identified a potential con-flict in a tagging request, the Functional Test Coordinator who approved the tagging request did not receive that input. As a result, the tagging order which de-energized the block enable was approved.
The Functional Test Coordinator is a temporary position assigned to the Operations De-partment during the outage.
The duties of the Functional Test Coordina-tor are to assist the on shift crew with removal and return of plant-systems to service.
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The inspector reviewed the licensee's corrective action which included a thorough review with the Functional Test Coordinators, a reemphasis on the turnover practices that the Functional Test Coordinators use, and a temporary test procedure to test the RAS function in a condition as close as possible to the actual conditions to resolve confusion over observed indications.
The inspector will review the temporary test pro-cedure results.
5.
Observations of Physical Security Checks were made to determine whether security conditions met regulatory re-quirements, the physical security plan, and approved procedures.
Those checks included security staffing, protected and vital area barriers, vehicle searches and personnel identification, access control, badging, and compensatory meas-ures when required.
Additional resources have been hired to handle the outage workload.
The inspector had no questions.
6.
Radiological Controls Radiological controls were observed on a routine basis during the reporting period.
Standard industry radiological work practices, conformance to radio-logical control procedures and 10 CFR Part 20 requirements were observed.
Independent surveys of radiological boundaries and random surveys of nonradio-logical points throughout the facility were taken by the inspector.
No sig-nificant problems were noted.
7.
Steam Generator Cleaning and Testing The licensee conducted an extensive program of chemical cleaning and testing of the steam generators during this refueling outage.
The purpose of this program was to remove the copper ions contained in the steam generators.
Copper components were used during the initial construction of certain second-ary systems.
Copper is known to contribute to degradation of the steam generator tubes.
The licensee has had an ongoing program to replace the cop-per components in the secondary systems.
Approximately 80 percent of those components have been replaced to date.
During the last refueling outage the licensee determined through eddy current inspections that copper was plating out on the steam generator tubes.
The growth of defects in the steam genera-tor tubes observed during the last outage was attributed to copper plate-out on the tubes.
The chemical cleaning process was used to remove the copper.
At the beginning of the outage the plant conducted a hydro lancing of the sludge pile in #2 steam generator.
The purpose of this lancing was to remove as much of the soft sludge from the steam generator as possible. The licensee
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also conducted a preliminary eddy current inspection of 250 tubes within #2 steam generator.
Number 2 steam generator is used as a barometer for the other steam generators.
The preliminary eddy current inspection was conducted
to determine if copper had led to a degradation of the tubes and it provided a base line for post cleaning comparison of eddy current results.
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The licensee then conducted the chemical cleaning of the #2 steam generator.
The cleaning process involved soaking the steam generator in a solution that dissolved copper ions into solution from the plate out region. When the rate of removal of copper ions decreased to a predetermined level, a different solution was used to remove iron ions.
By removing the iron ions, subsequent copper removal solutions were more effective.
The process continued until alternate copper and iron removal steps reached a predetermined acceptability limit. The generator was then flushed and returned to its normal outage condition.
A representative sample of 514 tubes was selected for eddy current inspection.
This sample size fulfilled the Technical Specification requirements for eddy current inspection.
This sample resulted in the classification of the genera-tor as C-1 in accordance with Technical Specifications.
Eight tubes were identified as degraded, four tubes that showed new defects between 20 and 40 i
percent and four tubes that showed an increase in a known defect of greater than 10 percent.
In addition to these tubes the licensee decided to plug two tubes as a result of inability to pass a probe through one of the tubes and a defective plug in another tube.
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In addition to the above testing, the licensee selected an additional sample of 507 tubes in #2 steam generator.
These additional tubes were selected for informational purposes only, in order to trend the condition of the generator.
The results of this inspection revealed two degraded tubes and one tube that exceeded plugging criteria.
This tube was plugged.
By reviewing the tapes made during the previous outage the licensee determined that the defect in this tube had existed from the previous outage. No growth in the defect was observed.
Since the chemical cleaning had removed the copper ion interference from the eddy current results, the defect indication became apparent.
The licensee concluded that the eddy current testing program showed that the defect growth mechanism identified during the last outage had been arrested.
With the steam generators classified as C-1 per Technical Specifications, the licensee determined that no further eddy current inspections were warranted.
The inspector had no further questions.
8.
Outage Outage preparation and planning has been well developed.
All major activities are thoroughly scoped and planned.
Major activities are coordinated during the planning phase to identify support functions and resolve conflicts.
A computerized management system has been custom tailored to the licensee's needs which allows management to review a variety of options before making scheduler commitment.
Over 3700 different tasks are tracked to assist in control of outage activities.
The overall effect is a well run outage or-ganization.
As routine inspections reveal problem areas requiring corrective maintenance, scheduler conflicts are resolved to minimize the impact on the outage.
The licensee limits the number of contractors allowed onsite and staggers work shifts to allow greater control of contractor activities and to minimize the impact upon site facilities.
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9.
Refueling Operations The inspector witnessed portions of the refueling activities and determined that the activities were within the Technical Specification limits.
During this refueling the licensee removed and sampled the fuel that was placed in the core during the last refueling.
Chemical analysis showed that this fuel was suspected of leaking causing higher than normal radiation levels in the.
primary and related systems.
The licensee unloaded the latest cycle fuel assemblies in order to identify pins suspected of leaking.
The technique used to identify leaking pins was an ultrasonic technique which detects the presences of water in each pin.
Water in a fuel pin is an indication that the pin has leaked during normal operation.
A total of four pins in three different assemblies were identified as containing water.
The leaking pins were removed from their respective bundles and replaced with dummy pins.
During the removal of one leaking pin, the pin broke.
Samples were taken to ensure that there was no radiological impact from the broken pin in the spent fuel pool.
The fuel assembly was reconstituted in a new rack.
While reloading the core on April 24, 1987 the refueling machine made contact with the light ring, causing some binding on the hoist box.
The condition went unnoticed until the hoist box, which was thought to be on its lower stop, dropped several inches and seated on the stops.
A fuel assembly was being lowered from the refueling machine at the time.
The fuel assembly contacted the side of the hoist box, probably in the area of the spreader and sheared off one side of a spacer grid. All refueling operations were ceased and an investigation into the event was conducted.
The licensee concluded that two known deficiencies contributed to the event.
The first deficiency was the setting of the underload lockout.
The function of the underload lockout is to stop all refueling machine movement when an underload condition is detected.
The underload function has two settings.
The first includes the weight of a full assembly and the hoist box.
This setting applies when the fuel and hoist box move together below the refueling mast.
The second setting is the weight of the fuel assembly alone.
This setting applies when the fuel assembly is lowered below the hoist box. During the transition zone between the two settings the refueling machine automatic-ally bypasses the underload setting.
The setpoint for the assembly plus hoist box was set at 2400 pounds.
However, some fuel assemblies (plus hoist box)
were just under this weight limit (approximately 2395 pounds).
Operators would bypass the underload lockout, as allowed by procedure, in order to lower these assemblies into position.
The operators would monitor cable tension during fuel movement as required by procedure during bypass operation.
The second deficiency was the interference of the light ring.
During refuel-ing a light ring is installed around the vessel.
The lights provide illu-
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mination in the reactor vessel.
During refueling operations the hoist box was known to occasionally contact the light ring.
The corrective action by the refueling crews was to move the refueling machine, partially lower the
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hoist box, index the refueling machine to the proper core location and then lower the fuel assembly into the core.
This maneuver cleared the interference between the lighting and hoist box. This problem was only apparent while mov-ing fuel elements on the periphery of the core.
On April 24, the refueling crew did not identify the interference problem between the hoist box and the light fixture.
On April 24, the refueling crew inserted an assembly into a peripheral loca-tion in the core.
Since the assembly did not contain a control element as-sembly (CEA) the combined weight of the hoist box and fuel was less than the underload setpoint of 2400 pounds.
The operators bypassed the unloader lock-out while monitoring cable tension.
Initially the weight was low, as is usually the case, because of friction between the hoist box and the refueling mast. However, in this case the weight was low because of contact with the light ring.
With the underload bypassed, the operators monitored the inser-tion activity and all parameters appeared normal. When the assembly reached the transition zone the underload setpoint was automatically changed to fuel weight only.
At this point the hoist box was believed to be on the lower stops when in fact it was probably slightly above the lower stops.
The fuel assembly was lowered until it reached a height of 90 inches above the lower support plate.
Vibrations were felt on the refueling machine, all refueling movement was stopped.
The licensee conducted a thorough review of the event including a Special Plant Operations Review Committee (PORC) meeting which the inspector attended.
Possible causes were discussed, interviews with the operators were conducted and a technical representative from the manufacturer of the refueling machine provided input. As a result of this review a thorough check out of the re-fueling machine was conducted including operations with a dummy fuel assembly.
All hardware associated with the damaged light ring was inspected and inven-toried.
Glass from the damaged light was primarily contained by the metal shield on the light fixture, however, some small pieces of glass fell into the core. All accessible pieces of glass were removed.
The licensee deter-mined that any slivers of glass remaining in the core were not a hazard.
Fuel movement and refueling recommenced on April 26.
The fuel assembly with the damaged spacer grid was replaced with an assembly of compatible burnout.
The unloader setpoint was adjusted to 2380 lbs. in order to preclude excessive use of the bypass function.
All operators were reinstructed on the use of the refueling machine.
The inspector had no further questions.
10.
Exit Interview Meetings were periodically held with senior facility management to discuss the inspection scope and findings.
A summary of findings for the report period was also discussed at the conclusion of the inspection.
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