IR 05000312/1981025
| ML20031A496 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 09/14/1981 |
| From: | Canter H, Obrien J, Thomas Young NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML20031A494 | List: |
| References | |
| 50-312-81-25, NUDOCS 8109230572 | |
| Download: ML20031A496 (11) | |
Text
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U. S. NUCLEAR REGULATORY COMMISSION
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0FFICE OF INSPECTION AFD ENFORCEMENT
REGION V
Report No.5 0-312 / 81-2 5 Decket No. 50-312 License No.
DPR-54 Safeguards Group Licensee:
Sacramento Municipal Utility District P. O.
Box 15830 Sacramento, California 95813 Facility Name: Rancho Seco Unit 1 Inspection at: Herald. California (Pancho Rnen Rito)
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Inspection conducted: Aucun t 3-91. 190 Inspectors:
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H rvey L. Cad [r, S{ ii[Flesic[e Inspector Date Signed a WM \\A T.
. V N-h - 7ohn O 'Brien,(Jnit ReQdMt Ir[spector ' Date Signed / Date S:gned Approved by: N/M , N.
~ ~ T. Young, Chie1 React M M'ojects Section 2 Date Signed ReactorOperati(onsProjectsBranch Date Signed Summary: Inspection between August 3-31. 1981, (Report 50-312/81-25) Areas Inspected: Operaticnal Safety Verification; Long Term Shutdown Activities; Monthly Maintenance Observations; Monthly Surveillance Observations; Review of Plant Operations; Plant Trips; Significant Event Followup; and, Independent Inspection Effort.
The inspection activities involved 170 inspector hours performed by the resident inspectors.
Results: Of the eight areas inspected, no items of noncompliance "or de Eations were identified.
8109230572 810974~ RV Form 219 (2) PDP ADOCK 05000312 G PDR - -
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. ~ . < . ,.* ~ .s , ' DETAILS 1.
Persons Contactd 1,2R. Rodriquez, Manager, Nuclear Operations P. Oubre', Plant Superintendent 1,2D. Blachly, Operating Supervisor N. Brock, Electrical /ISC Maintenance Supervisor D. Cass, Mechanical Maintenance Supervisor 1,2Q. Coleman, Quality Assuwance Engineering Technician 1,2R. Colombo, Technical Assistant
G. Coward, Maintenance Supervisor B. Daniels, Supervising Electrical Engineer D. Elliott, Quality Assurance Engineer
D. Gardiner, Senior Chemical 6 Radiation Assistant
B. Gore, NRC License Examiner 2R. Laurence, Senior Mechanical Engineer 2R. Meyers, Nuclear Engineer 1,2R. Miller, Chemistry / Radiological Supervisor R. Moore, SMUD Special Agent 1,2T. Perry, On-site Quality Assurance Supervisor D. Raasch, Manager of Generation Engineering Department
L. Schwieger, Quality Assurance Director 2T. Tucker, Outage Coordinator 1,2D. Whitney, Engineering and Quality Control Supervisor B. Wichert, Mechanical Engineer W. Wilson, Senior Chemical & Radiation Assistant The inspectors also talked with and interviewed several other licensee employees, including members of the engineering, maintenance, operations, and quality assurance (QA) organizations.
Denotes those attending the Exit Interview on August 19, 1981.
Denotes those attending the Exit Interview on August 31, 1981.
2.
Operational Safety Verification The Reactoe Plant was critical between August 1st and 13th, 1981.
The plant was shutdown on August 13, 1981, due to Main Turbine-Generator failure.
In addition to the items mentioned in Para-graph.2, the inspector verified'the operability of the following safety features systems or subsystems: auxiliary feedwater and the "B" diesel generator.
No items of noncompliance or deviations were identified.
3.
Inspection During Long Term Shutdown During the report period the inspector obsbrved control room operations, revicred applicable logs and conducted discussions . - ?
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, _2 . with control room operators.
The inspector verified surveillance tests required during the shutdown were accomplished, reviewed tagout records, and verified applicability of containment integrity.
Tours of Auxiliary Building and Reactor Building accessible areas, including exterior areas were made to assess equipment conditions, plant conditions, radiological controls, safety, and adherence to regulatory requirements and to verify that maintenance requests had been initiated for equipment in need of maintenance.
The inspector observed plant housekeeping / cleanliness conditions, including potential fire hazards, and verified implementations of radiation protection controls.
The inspector by observation and direct interview verified that the physical security plan was being implemented in accordance with the station security plan.
The inspector reviewed the licensee's jumper / bypass controls to verify there were no conflicts with technical specifications and verified the implementation of radioactive waste system controls.
The inspector witnessed portions of the radioactive waste systems controls associated with radwaste shipments.
No items of noncompliance or deviations were identified.
4.
Maintenance Observations The inspectors observed portions of the maintenance activities listed below and verified that. work was accomplished in accordance with approved procedures; that work'was accomplished by qualified personnel; that provisions for stationing a fire watch to oversee activities involving welding and open flame were complied with; and, that LCO requirements were met during repair.
(a) "A" Diesel Gen. high temp.' alarm (ISC) WR58889 (b) Auxiliary Feed Pump flow transmitter (ISC) WR59224 (c) "A" Diesel Generator governor (Elect) WR56903 _(Mech). NR59583 (o) Boric Acid Pump (Mech) WR59680 (e) "A" Inverter to Vital Power Bus lA (Elect) WR59716 No items of noncompliance or deviations were identified.
5.
Surveillance Observations The inspectors observed portions of the below listed surveillance testing to verify that the tests were covered by properly approved procedures; that the procedures used were consistent with technical specification requirements; that a minimum crew requirements were inet ; that test prerequisites were completed; that special test equipment was calibrated and in service; and, that the test results were adequate.
(a) 8/21/81 - (SP.201.03B) - Diesel Driven Fire pump (P996.)
(b) 8/22/81 - (SP 206.03B) - Diesel Generator "B" monthly tes _ _ _ _ _ _ _ _ _ _ _ _ _ _ . . -3- . No items of noncompliance or deviations were identified.
6.
Review of Plant Operations A.
Procurement The inspector examined procurement and storage activities to ascertain whether the purchase of components, materials, and supplies used for. safety related functions is in conformance with the licensee's approved QA program and implementing pro-cedures.
The inspector witnessed a-receipt inspection, and verified nonconforming items are segregated ar.d marked accordingly; housekeeping and environmental requirements for storage of QA Class I components are being met; and, limited shelf-life items are contro]1ed.
In addition to the above the inspector selected three QA Class I components (one mechanical, one electrical, and one instrument,and control) and verified their traceability.
The inspector' examined records that include, (1) Purchase orders; (2). Rec'eipt' records;.(3) Storage locations; (4) Issue' records; and (5) QA certification records.
- , , No items of noncompliance or deviations were identified.
B.
Onsite Re' view Committee, .. , , The inspector examined'the onsitsfreview functions and attended a Plant Review Committee (PRC) meeting on August 12, 1981.
He performed this activity to' verify conformance with technical specifications and"other regulatory requirements.
This review included: changes since the previous inspection in the charter and administrative proceduren governing the PRC membership and qual'ifications; PRC meeting frequency and quorun requirements; activities reviewed including pro- ' posed technical specifications changes, proposed facility and procedure changes, proposed tests and experiments con-ducted per 10CFR 50.59, and others required by technical specifications.
No itema of noncompliance or deviations were identified.
7.
Plant Trips following the plant trip on August 7, 1981, the inspector ascer-tained the status of the reactor and safety systems by observation - - - - - - .-
i . -4- . of control room indicators and discussions with licensee personnel concerning plant parameters, emergency system status and reactor coolant chemistry.
The inspector verified the establishment of proper communications and reviewed the corrective actions caken by the licensee.
Most systems responded as expected, and the plant was returned to operation on August 8, 1981.
The circumstances behind the trip are as follows: The plant was operating on' August 7, 1981 (153'5) at about 52% power, while maintenance was be.ing nerformed on the Electro-Hydraulic Control (EHC) System for the main turbine.
The operators were asked to go to " manual".from'"dperate ICS" on the EHC panel by the technicians who 'were working on 'the EHC problem.
In doing so, the EHC system;went td." operate-auto" and received a signal to ramp close all throttle valves and governor valves.
The operators could not.get the turbine out of the " operate auto" position.
It was found a short time later-that uring the follow-ing transient, a couple of pins'were bent in a'_-atrol card in the EHC control cabinet which caused this event.
The operators, seeing that the turbine plant and the reactor plant were running back due to ICS responses, decided to trip the generator output breakers to prevent the generator from motoring.
This dropped switchyard voltage to a.value believed to be well below the 214KV that requires the diesel generators to be started and loaded to accept the 4180 V safety related buses. It's postulated, that due to low grid voltage, the buses that were supplied by the auxiliary transformers did not shift quick enough to the startup transformer supply and the 6.9KV Reactor Coolant Pump buses there-by lost power.
All four reactor coolant pumps were lost.
No seal damage occurred because the auto-close interlock in the RCP seal retur:, isolation valve control circuit was removed approximately two years ago.
This left the seals supplied with cooling flow.
At this point, a reactor trip ensued probably due to not havirg the proper pump combination for the givea reactor power.
(Power to pump trip.)
Within 1.5 to 3 minutes, an operator had first Reactor Coolant Pump back on line.
Along with the reactor trip and loss of Reactor Coolant Pumps, the Auxiliary Feed Pumps started aim controlled steam generator level to about 30 inches on the OTSG startup level range.
(This is normal operation.)
Another operator started the diesels and picked up safety re-lated loads as a precaution because of the degraded grid voltage condition which occurred due to high system loads and the plant trip.
(With a station blackout in this condition, without the diesels handling safety related loads, these loads may not have functioned properly if called upon.)
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_ _ - _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ . -5- . buring this event, subcooling remained greater than 90 F, Reactor Cnolant Pressure ranged between 1881 and 2236 psi and the Reactor Coolant System hot leg temperatures ranged between 542 and 5990F.
These figures are not of safety concern.
Three NRC license examiners were in and around the control room at the time of this event.
The NRC was notified officially on the Emergency Notification System fifty-five minutes after the event began.
NRC inspectors were on site until after grid voltage rose from a degraded condition (214KV) to above 218KV and until after the reactor was brought critical.
During the start of this event besides losing the RCP's ar.d other loads,.the operating Main Feed Pump ("A") tripped.
Preliminary information obtained by the inspector indicates that the Lovejoy feed Pump controller to the "A" Peed Pump lost power which sent a minimum demand signal to the system and the Feed Pump respondeu accordingly.
When power was regained (a short time later) the Feed Pump responded to a high demand signal as it was designed to.
At the same time that the slow transfer of the bus occurred, the lube oil pump associated with the "A" Feed Pump apparently a.c.
lost power and the d.c. pump did not keep adequate pressure on the system.
This may have caused.the "A" Main Feed Pump to trip.
Since the events that took. place with regard to the Main Feed Pump trip are: not solidfied es 'of. this - writing, the inspector asked to be informed of the final, resolution of the sequence of events.
Until that~ resolution is~ examined, this item will remain open.
(81-25-01) - Due to the similarity of~this' event'to one that occurred at Arkansas Nuclear One, Unit 1, (ANO-1) on August 21, 1981, the inspector asked the licensee if plant operations personnel would be informed on.the ANO-1. event.
The licensee stated that operations personnel would.befinformed of the ANO-1 event, and the plant staff will look'into the generic aspects as they relate to Rancho Seco.
8.
Significant Events , l Three significant events other than the plant trip discussed in ! paragraph 7 occurred during the August inspection report period, a.
Auxiliary Feed Pump " Phantom" Start At 2:00 am on August 6, 1981, an auxiliary operator noted conditions to be normal in the Auxiliary Feed Pump cubicle.
At approximately 4:40 am he found Auxiliary feed Pump P319 running.
The Control Room Operators secured the pump after verifying it was recirculating to the Condensate Storage Tank.
A licensee representative stated that restart of the . .
f . -6- . pump gave all the proper control room annunciators, but when the pump was found running at 4:40 am the Control Room master annunciator, which states when P319 is running or in manual, was not lit.
The inspector asked for an explanation for this event.
The licensee will perform a test on P319 which will entail a 1ccal start, to see if they can repeat the problem.
As of this writing there is no explanation available as to the cause of the " phantom" start of P319.
Also, the licensee has no reason for the pump start going undectected in the control room nor is the duration of the pump"s run known.
This item will remian open pending further investigation and testing by the liccensee. (81-25-02) b.
Main Turbine Damage During the early morning on August 13, 1981, while operating at 100% power, the control operators heard and felt massive main turbine vibration.
A control room recorder chart point for the number 4 main turbine bearing'on the number 1 low pressure (LP) rotor'went off scale high.
The operators commenced a 50MW per minute shut down rather than a rapid turbine trip at this point which would have caused a secondary and pri. nary system ' transient similar to the one that occurred an August 7, 1981, and would have caused major damage to the rest of the main trubine.
As it turned out, major damage occurred to the #1 LP turbine and condenser, but minor damage occurred to the rest of the turbine.
The shutdown was a controlled event with no major problems.
The damage reported immediately after the event consisted of a vibration induced EH line separation at a union, plus a small diameter component cooling water radiatian sensor line failure.
Subsequent system walkdowns showed evider.ce of high vibration.
Lagging repairs and other minor repairs in various heaters were found to be necessary.
The major damage, Powever occurred to the #1 LP and the associated condenser tubes.
The licensee supplied the inspector with the following sunmary of damage to the Westinghouse turbine: 1.
LP-1 Governor End a) The fifth stage blade ring haa lost three blades.
The pieces remaining of two of the blades showed corrosion.
The third blade which was in the blade ring when the cylinder was removed, showed cracking and a heavy-oxide fil _. _ _ _ _ _ -. -. -7- , . b) There was evidence of rubbing on the center portion of the fifth stage blade ring and fracture of the blade metal.
c) There was damage to the blades of the sixth, seventh and eighth stage blade rings, but it was not ex-tensive, d) The rotating stages showed some damage, but it was not extensive.
One blade on the fifth stage had a cracked root.
2.
LP-1 Generator Err' a) Probably 30-40% of the blades in the fifth stage blade ring'were., missing. -(Will be found in the condenser,probab]v.)
b) There was extensive damage;to~the fis.h rotating stage including: missing blades and shroud band.
c) The sixth, seventh, and eighth rotating stages showed shrapnel damage.
d) The sixth, seventh, and eighth stationary blades showed shrapne. damage.
e) Pieces of blade roots remalaing in the fifth rotating stage showed evidence of oxidation.
3.
General a) Numerous pieces of metal were visible in the extraction steam ports.
b) There were substantial amounts of metal filings and granules.
c) Cylinder inspection port covers showed evidence of sharpnel damage.
Based on the above observations, it was SMUD's preliminary _' opinion that the failure mode was fatigue caused by flow vibration in the fifth stationary stage, generator end.
There are marks cn1 several of the portions of blades still attached to the fifth stage bald ring, and there is no apparent oxidations which would indicate stress, governor end, indicate a condition that has existed for some time and may.have caused a failure in the future.
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,- -, - - - - -, - ' -8- . This event was apparently handled in such a manner as to not endanger the healt? and safety of the public.
c.
Decay Heat Removal System Disabled On August 26, 1981, while t' a plant was in cold shutdown for. main turbine repairs, tne 120 volt AC Vital Power Bus lA was deenergized, which resulted in the loss of decay heat removal cooling of the reactor core for approximately ten minutes.
Electrical maintenance was being performed on the "A" inverter that supplies the 120 volt AC Vital Power Bus lA.
The "A" train of the Decay Heat Removal System was in operation.
At approximately 8:22 am (PDT), a technician caused a:short and a trip of the "A" in-verter.
The resulting power loss caused the pressure instrument in the Decay Heat Removal System cuction line to fail high.
The Overpressure Protective Circuitry for -the Decay' Heat System sensing this high preseure, shut decay heat suction valve HV-20001.
Anocher feature of.the protective circuitry consists of securing the "A" Decay Heat" pump automatically when-ever HV-20001 is not in the, full'open position.
When HV-20001 cahefoff its fu'll op'on seeing this, the control en seat, the "A" decay heat pump. 'did. net - s'ecure. ' Up room operat'or' secured the "A" decay heat pump.
At 8:33 am (PDT) HV-20001.was reopened, and the "A" train of the Decay Hest' Removal System was restored while the 120 volt AC Vital; Power Bus AA was provided wfth tem-porary power-from a maintenance (power supply.
~ . - . .. Incore thermocouples'a'nd RCS t'emperatures were monitored ~ while the_ Decay Heat Removal' System was secured.
No increase in any~of the monitored' temperatures was observed.
Letdown and Makeup systems were in operation during this event.
. Repairs of the "A" inverter were completed, and the normal lineup of 120 volt AC Vital Power Bus lA was restored on August 31, 1981.
Licensee investigation into the cause of the "A" Decay Heat pump not securing automatically will be followed up by the Resident Inspectors.
(81-25-03) The licensee is scheduled to report this item to the NRC in a written report by about September 25, 1981.
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_9 . 9.
Independent Inspection Effort Discussions were held between the Resident Inspectors and operations, security and maintenance personnel in an attempt to better under-stand prob] ems they may have which are related to nuclear safety.
These discussions will continue as a standard practice.
On numerous occasions, during the month of August, the Resident Inspectors attended operations status meetings and shutdown status meetings.
These meetings are held by the Operations Supervisor and Scheduler to provide all disciplines onsite with a update on the plant status and ongoing maintenance and outage work.
In addition to the above, independent inspection effort was performed on the following items: IAEA Inspection on August 17-18, 1981- ? The inspectors participated in discussions with the licensee on this, the second IAEA~ inspection at Rancho Seco.
They also pro-vided escort service'through the plant and witnessed the installa-tion of cameras in the. Spent Fuel Building.
' License Examiner Familiarization The inspectors provided space for three employees o.
Battelle Pacific Northwest Lacoratories wt,are under contract te provide assistance to the Operator Licensing Branch.
The inspectors supplied the contract employees with assistance in obtaining training in the day-to-day operations at Rancho Seco, plant tours and made arrangements for security training and vital area access.
" Cold" Chemistry Lab Procedures The inspectors witnessed the chemical analysis of secondary plant water samples.
The only comment the inspector had from his observa-tions was that some of the lab equipment such as plastic graduated cylinders, flasks, and pipettes were degraded to the point that new ones appeared necessary to eliminate cross-contamination problems.
This comment was given to a Chemistry supervisor who stated that action will be taken.
Possible OTSG Tube Leaks The licensee had indications after the Tur'oine shutdown on August 13, 1981 of another cet of OTSG tube lee's possible in the "\\" OTS r _
-10- . . (OTSG tubes were plugged earlier this year.)
At first, the licensee pursued the source of Xenon in the OTSG sampler as being from-leaks in the Waste Gas System.
That source has 1.cc been.
verified.
On about August 25, 1981, during the evaluation of the possible primary to secondary leak, it was determined that the nitrogen system inside the Reactor Building was contaminated with the same 'adionuclides being detected in the OTSG's.
The licensee is continuing a sampling program to verify that a primary to secondary leak does exist.
The licensee will monitor the situation on start-up, also.
Until that program is complete and the results examined by the inspector, this item will remain open.
(81-25-04) No items of noncompliance'or deviations were disclosed.
10.
Exit Interview , .. The inspector met with licensee-representatives (denoted in Paragraph 1) throughout the month and at the nonclusion of the inspection on August.31, 1981 and summarized the scope and find-ings of the inspection.activ,ities.
The licen~see acknowledged the findings.
' . No items of noncompliance or' deviations were identified.
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