ML20214S345
| ML20214S345 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 09/18/1986 |
| From: | Heider L YANKEE ATOMIC ELECTRIC CO. |
| To: | Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| DCC-86-138, FYR-86-088, FYR-86-88, NUDOCS 8609290468 | |
| Download: ML20214S345 (13) | |
Text
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YANKEE ATOMIC ELECTRIC COMPANY Te'ephone(6 ")8'2-8'oo TH0( 710-380-7619 1671 Worcester Road. Framingham, Massachusetts 01701 DCC 86-138 21 2.C2.11
. va v September 18, 1986 FYR 86-088 United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406 Attention:
Dr. Thomas E. Murley Regional Administrator
References:
(a) License No. DPR-3 (Docket No. 50-29)
(b) YAEC Letter to USNRC Region I, dated July 16, 1986, Licensee Event Report 50-29/86-09 (c) I&E Letter to YAEC dated July 11, 1986; I&E Inspection 50-29/86-09 (d)
I&E Letter to YAEC dated August 19, 1986; Notice of Violation (NRC Inspection Report No. 50-29/86-09)
Subject:
Response to Inspection 50-29/86-09
Dear Sir:
Reference is made to I&E Inspection No. 50-29/86-09 conducted by your Mr. H. Eichenholz during the period June 26-July 2, 1986, at the Yankee Nuclear Power Station, Rowe, Massachusetts.
The report made subsequent to that inspection identified items which apparently were not conducted in full ccmpliance with NRC requirements.
In accordance with Section 2.201 of the NRC's " Rules and Practices," Part 2, Title 10, Code of Federal Regulations, we hereby submit the following information:
Aoparent Violation A.
Technical Specification Limiting Condition for Operation (LCO) 3.4.11 requires that in Modes 1, 2, 3, and 4, at least one main coolant system vent path must be operable at both th reactor vessel head and the pressurizer steam space. Technical Specification LC0 Action Statement 3.4.11.b requires, in part, that whenever both main coolant system vent paths are inoperable, at least one of the vent paths must be made operable within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, or the reactor must be placed in hot standby within six hours and in cold shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
8609290468 860918 PDR ADOCK 05000029 O
. FYR 86-088 Contrary to the above, between December 2,1985 and June 20, 1986, while in Mode 4 (hot shutdown) or higher for the vast majority of this period, both the reactor vessel head vent and the pressurizer steam space vent were inoperable, and the reactor was not placed in hot standby and then cold shutdown.
The vent paths were inoperable in that undersized trip coils were placed in the respective circuit breakers for motor operated valve VD-MOV-559 in the reactor vessel head vent path, and motor operated valves PR-MOV-558 and PR-M0V-560 in the pressurizer steam space, which would result in loss of power to the valve motors during operation of the valves under design basis conditions.
B.
Technical Specification LC0 3.7.1.2 requires that in Modes 1, 2, and 3, at least two independent emergency feedwater pumps and associated flow paths shall be operable.
Technical Specification LC0 Action Statement 3.7.1.2 requires that with one inoperable emergency feedwater pump, at least two feedwater pumps must be made operable within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the plant must be placed in hot shutdown within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
Contrary to the above, between December 3, 1985 and June 19, 1986, while in Mode 3 (hot standby) or higher for the vast majority of this period, a flow path (to the steam generator blowdown lines) for emergency feedwater was inoperable, which would have resulted in the inability of the emergency feedwater pumps to perform their intended function under certain conditions, and the reactor was not placed in hot shutdown. The flow path was inoperable in that an undersized trip coil was placed in the circuit breaker for motor operated valve, EBF-MOV-557, which would result in loss of power to the valve motor during operation of the valve under design conditions.
These violations have been categorized in the aggregate as a Severity Level III problem (Supplement I).
Response
We concur with the Notice of Violation as described above and in reference (d). We also concur with the description of the incident as described in reference (c). This event was discussed in detail at a Region I Enforcement Conference held July 22, 1986. Most of the information described below was discussed at that meeting.
I.
INTRODUCTION On June 26, 1986, at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br />, while the plant was in cold shutdown, Mode 5, it was discovered that the overload trip coils on breakers supplying four motor operated valves (MOVs), were not of sufficient capacity for the in-rush current of the MOV motors. This discovery was made during an ISI surveillance test and subsequent corrective maintenance.
The motor operated valves effected by this incident are, pressurizer vent valves PR-MOV-558 and PR-MOV-560, reactor head vent valve VD-M0V-559, and emergency boiler feed valve EBF-MOV-557. These valves
. FYR 86-088 were surveillance tested by cycling the valves prior to plant start-up from refueling in December 1985. At that time these valves were declared operable.
EBF-MOV-557 was cycled monthly since the 1985 refueling with no problems discovered.
Despite this, the discovery of the smaller rated overload trip coils casts doubt as to whether these valves would have operated for all potential operational challenges, and these valves must be considered inoperable for the time period in question.
EBF-MOV-557 is required to be operable per Tech. Spec.
3.7.1.2.
The other three valves are required to be operable per Tech.
Spec. 3.4.11.
The overload trip coils were replaced with suitably sized coils during the outage.
After discovery of the event, management ordered that the Yankee Plant remain in cold shutdown, Mode 5, until the cause of the problem was determined and appropriate corrective actions were initiated.
Management directed that a task force be formed to investigate this incident and that a final report with recommendations be forwarded to the Manager of Operations. The plant returned to power operation on July 3,1986.
II. TASK FORCE - CONCLUSIONS AND RECOMMENDATIONS The task force concluded that the root cause of this event was the ambiguous description of requested equipment on the purchase order, concurrent with an inadequate receipt inspection and insufficient post installation testing of this equipment.
The task force had the following recommendations. These recommendations are applicable to both the Yankee plant and Yankee Nuclear Services Division (YNSD) engineering.
A.
Purchase Order Clarity A purchase order should be clear and unambiguous when specifying equipment characteristics.
1)
Specific catalog numbers with a clear description of the equipment should be specified whenever possible.
2)
Amendments to a purchase order should clearly define the requirements of the original purchase order that still apply and identify requirements that have changed.
3)
It should be clearly stated in the purchase order that i
vendor questions or requests for clarification should be forwarded to YAEC cognizant individual for resolution.
The statement "No substitutions without purchaser approval" should be added to all purchase orders.
B.
Receipt Inspection Adequacy The receipt inspection process should be strengthened.
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. FYR 86-088 1)
The receipt inspection procedure should have specific guidelines for inspection of routinely received safety related equipment.
t 2)
The design engineer should have input in specifying requirements in the receipt inspection of unique or critical items.
In some instances the presence of the design engineer during the receipt inspection process may be i
appropriate.
3)
Receipt inspection training for technical and non-technical individuals should be formalized.
4)
A Material Discrepancy form should be instituted to resolve and document discrepancies in catalog numbers, etc., so that resolution can be made without the issuance of a non-conformance report. When resolution of the discrepancy cannot be made, a non conformance report will be generated.
5)
On an interim basis, a second qualified individual will perform a confirmatory, technical receipt inspection of safety related equipment. Management should consider the need and practicality of continuing this confirmatory receipt inspection after items 1 through 4 are addressed.
C.
Installation and Test Procedure Adequacy Installation and test procedures should specify the testing requirements of safety related equipment in accordance with the following recommendations.
1)
The installation and test procedure should test where practical, all components and subcomponents that perform a
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function that affects the operation of the system (i.e.,
trip setpoints, alarm setpoints, reset functions, etc.).
2)
The installation and test procedure should specify in advance, or specify by means of testing, the required setpoints or range of settings that could affect equipment j
operation.
3)
Adjustments of equipment settings during testing should be l
documented on the installation and test procedure and i
approved by supervision.
I 4)
Personnel (including the PORC Committee) involved with the development and review of installation and test procedures should be more diligent in assuring that adequate testing is performed. -Input to and/or review of the adequacy of the test procedure by the design engineer should be considered.
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. FYR 86-088 i
D.
Manpower Adequacy Management should review the adequacy of existing manpower resources for implementation of design change modifications.
1)
Time and work load demands of plant cognizant engineers should be reviewed.
2)
The training and familiarity of plant engineers and plant craft labor with newly acquired equipment should be strengthened.
Management should review manpower and time constraints.to accomplish this recommendation.
E.
Design Control Adequacy The design document should clearly state the equipment performance assumptions used in the design process for reference during installation and future maintenance.
1)
The design engineer should clearly specify in the design document the expected performance characteristics and critical adjustment settings of equipment. This information l
will facilitate the development of installation and test a
procedures.
l 2)
The requirement for documenting the resolution of minor j
changes / discrepancies between the plant cognizant engineer and the NSD engineer should be re-emphasized.
3)
Critical adjustments and settings on safety related equipment should be recorded and maintained.
III. TASK FORCE MEMBERSHIP AND METHODOLOGY The task force performed three basic functions. The three functions were:
(1) the investigation into the root causes of the event, (2) evaluation of contributing causes, and a review of the consequences of the event; and (3) recommendations for improvement and/or corrective actions in the short and long term.
The task force was comprised of seven (7) members, the majority of whom reported to off-site organizations. Three (3) individuals were in the QA/QC organization. The NSARC chairman and three (3) NSARC members / alternates were on the task force. Three members of the task force were also Yankee Plant PORC members / alternates. One individual on the task force, the Director of Quality Assurance, reports directly to the president of the Company.
The task force was formed at the direction of the Vice President /
Manager of Operations and the Plant Superintendent.
Requirements of the Task Force charter were the following:
I
. FYn 86-088
- Determine the underlying factors leading to the incident.
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- Recommend to the plant PORC Committee as well as management short term corrective actions to assure the operability of safety-related electrical equipment.
- Recommend long term corrective actions to preclude recurrence of incidents of a similar nature.
- Resources of the company available to the task force.
- The task force membership open and candid with NRC.
- Full cooperation by plant personnel.
- Investigation conducted in an expeditious and aggressive manner.
- A final report with recommendations to be forwarded to the Manager of Operations.
The task force developed short term action items to implement the investigation. These action items were as follows:
- Review the events associated with design, procurement, receipt inspection, installation and testing of EDCR 84-312.
- Discuss input from the Plant Cognizant Engineer / Maintenance Support Supervisor of EDCR 84-312.
- Review the actions completed to date to correct the discovered defects.
- Review the inspection / verification of all Gould ITE switchgear equipment within the plant.
- Review all EDCRs and PDCRs involving electrical equipment since the 1984 refueling outage (inclusive) to determine if a similar event could have occurred in other installed safety related equipment.
- Propose any other short term corrective actions deemed necessary to assure the operability of safety related electrical equipment at the Yankee plant.
- Report to PORC and Plant and Corporate management the results of the short term corrective actions.
In the course of reviewing all EDCRs and PDCRs since the 1984 refueling outage, small relatively minor discrepancies were found.
One discrepancy was found to be of a more significant nature. This discrepancy involved improper size trip coils installed in two safety injection building fan breakers. These breakers were supplied by Gould, Inc. None of the discrepancies had an impact on equipment operability.
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. FYR 86-088 Due to the nature of the discrepancy on the fan breakers, the task force increased the scope of their evaluation as follows:
- Review all design changes involving 480 volt breakers, contactor/
starters, and their associated subcomponents implemented since i
January 1,1981.
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- Review a sampling of I&C and mechanical design changes.
- Implement a verification of procurement documentation pertinent to safety related spare parts in the stockroom, received since August, 1985.
- Test available Gould breakers on site.
l The increase in review scope was.necessary to determine if a generic breakdown in our procurement and testing programs was occurring.
It was felt that the review of electrical design changes since January 1, 1981 gave reasonable assurance that any discrepancies that could impact operability of a system would be found.
Since the time period involved five years and three refueling outages, it was felt that any discrepancies that could effect operability of a system, which was implemented prior to that time period, would have been discovered 1
i during surveillance testing.
I A review of spare parts in the stockroom received from August 1985 was j
initiated to evaluate the effectiveness of the receipt inspection
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program.
It was felt that the spare parts in the stockroom would reflect installed parts in the plant received during that same time period.
In the course of the expanded scope review, discrepancies in catalog r
numbers, etc., were found. These discrepancies by their nature were not significant in themselves but did show a lack of proper documentation of minor discrepancies. Discrepancies were also found in installed overload heater ratings. No discrepancies were found i
that would impact on equipment operability.
i As a result of the task force's investigation, no generic breakdown in j
the receipt inspection program or design control program were found.
i The task force reported the results of its review to the Vice President / Manager of Operations and the Plant Superintendent. The task force chairman reported to the PORC Committee the results of the l
task force's investigation. Based on discussions with Plant and Corporate management and PORC Committee discussion, plant startup from j
cold shutdown was initiated.
IV. DETAILS OF THE EVALUATION During the 1985 refueling outage the power supplies for VD-MOV-559, PR-MOV-560, PR-MOV-558 and EBF-MOV-557 were relocated from existing
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plant busses to the plant emergency busses. This modification was accomplished via Engineering Design Change Request EDCR 84-312, J.0.84-419. The installation and test procedure for this modification was OP-5000.181, "MOV Power Supply Changes."
. NR 86-088 The original scope of this modification only included MOV-558 and 557.
An early purchase request specified that two, class 1E 480 volt combination starter circuit breaker, type 50 AF,.97 AT, size 1, with T8 overload relays be purchased from Gould, Inc. The ".97 AT" refers to a overload trip coil with a.97 amp continuous rating.
Purchase order No. 104980 was issued on January 29, 1985. This purchase order was changed to specify a "2.75 AT" overload trip coil. The purchase order was further amended to require functional testing of all breakers and for their trip curves to be certified.
A Supplement to the purchase order was issued to increase the quantity of combination starter breakers to four (4), as well as other changes.
The "2.75 AT" overload trip coils were specified in this purchase order which was issued on April 4,1985.
One final amendment to the purchase order was issued November 6,1985, and requested quantities of four different size overload heaters.
The four combination starter, circuit breakers in question were received and receipt inspected in late August 1985.
These breakers were sent by the supplier with.57 AT overload trip coils. The receipt inspection did not discover this discrepancy.
The purchase order specified 2.75 AT overload trip coils. There devices have a tripping range of 15 to 28 amps with a 2.75 amp maximum continuous rating and has the catalog designation A80D10. The received trip coils have a tripping range of 2.41 to 4.34 amps eith a
.57 amp maximum continuous rating and has a catalog designation A80A10.
The trip coils have sufficient identification on them for a knowledgeable individual to verify their rating, range and-catalog number. These trip coils are subcomponents of the combination breaker starter assembly. The cognizant engineer who performed the receipt inspection was inexperienced in these particular combination breaker starters. The vendor provided a test report as required by the purchase order. This test report clearly showed that the overload trip coils, specified by catalog number on the test report, were tested in the appropriate ranges for the trip coils sent.
If the engineer was knowledgeable as to the required range of operation for the trip coils specified on the purchase order, then it would have been clear that the test report related to trip coils that were not those specified on the purchase order.
The cognizant engineer did not have adequate information in hand, i.e., catalog information, etc., to determine the expected ranges of these trip coils.
It was unclear as to what the "2.75 AT" designation really meant.
The designation could be interpreted as 2.75 amps maximum continuous rating or it could be interpreted as a 2.75 amp trip setting on a trip coil.
The NSD engineer used the former interpretation when specifying the order while it is believed that the Gould personnel used the latter interpretation when assembling and testing the breaker starters.
The "AT" designation has been used in the past by Yankee NSD engineering.
. FYR 86-088 A vendor surveillance was performed at Telemechanique, Inc. (formally Gould,Inc.). This surveillance found that the Telemechanique's engineer had problems understanding the "AT' terminology.
He misinterpreted the "AT" to mean a trip setting, as opposed to a maximum continuous current rating. The Telemechanique's engineer did not contact the Yankee NSD design engineer for clarification.
This interpretation discrepancy of combination starter nomenclature would lead to the conclusion that poor communication and poor definition of the requirements were used during the original specification of equipment by the design engineer. The "AT" designation is not used in the catalog information. The events also lead to the conclusion that the plant cognizant engineer did not have sufficient knowledge or information to verify whether the received equipment was in fact what the design engineer attempted to specify on the purchase order.
The combination breaker starters were installed during the 1985 refueling outage per approved installation and test procedure OP-5000.181. This procedure was reviewed by the Plant Operations Review Committee (PORC) prior to implementation. The procedure did not specifically require a test of the breakers and overload trip coils in question.
The procedure did require testing of the thermal 3
overload devices.
It is the thermal overload devices that are sized closest to the normal running current of the motor, to provide motor protection in the event of a locked rotor incident.
It would seem that the testing of the thermal overload devices overshadowed testing of the breaker itself with its overload trip coil and relay.
Since there are a series of overload settings on the breaker, testing of the 4
breaker with the intended overload setting should have been performed.
The overload setting should have been clearly specified in the design document. The belief that stroking the valves as the final test is the best assurance of operability, proved to be incorrect in this instance. All components that perform a function that effects operation (i.e. trip setpoints, etc.) should have been thoroughly tested.
The majority of the 480 volt electrical equipment on the plant site have separate breakers and starters.
The Gould combination breaker /
starter is relatively new to plant personnel.
Both the plant Cognizant Engineer and the Technicians performing this design change, were relatively unfamiliar with the Gould combination breaker / starter. This unfamiliarity with the equipment contributed to 3
the incomplete receipt inspection and installation and testing procedure.
V.
Assessment of Consequences - Head Vent / Pressurizer Vent Valves I
The head vent and pressurizer vent motor operated valves are required to be operable per Technical Specification 3 4.11.
The Technical Specification requires at least one main coolant system vent path be operable. Due to improperly sized trip coils installed in three of the four vent valves with the possibility of premature tripping, both vent paths would be considered inoperable between December 2,1985 and i
June 26, 1986.
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. FYR 86-088 The pressurizer and head vent valves were installed in 1981 as a result of a TMI action item. These valves, although installed in 1981, remained de-energized and officially inoperable for over one year awaiting the issuance of a safety evaluation by the Nuclear Regulatory Commission. These valves would be used, in the longer term, after an accident to vent the reactor head and pressurizer of non-condensible gases, such as hydrogen.
If the electrical breakers had malfunctioned due to premature tripping, the breakers could have been physically jumpered to allow opening of the valves. Although j
this action is not specified in any emergency procedures, this type of emergency corrective maintenance activity is considered and simulated during plant emergency drills.
If necessary the trip coils on the Gould combination starters could be i
jumpered. The Emergency Motor Control Centers for these valves are accessible in a post-accident environment. Operation of these valves is not assumed in the accident analysis. A proposed Technical
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Specification change was submitted October 15, 1985 to make these valves normally de-energized during normal plant operation for Appendix R considerations.
Plant procedure OP-3053, " Inadequate Ccre Cooling" describes other methods that could be used to mitigate a hydrogen bubble, besides the use of the vent valves.
These methods are as follows:
- Hydrogen can be stripped from the reactor coolant to the pressurizer vapor space by pressurizer spray operation if a main coolant pump is operating.
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- Hydrogen in the pressurizer vapor space can be vented by the power operated relief valve, PR-50V-90.
- Hydrogen can be removed from the coolant system by the letdown line and stripped in the LPST tank where it can be routed to the waste gas system.
- In the event of a LOCA, hydrogen would vent with the steam to the containment.
There would be ample time in a post accident situation to effect corrective actions on the vent valve breakers, or, if necessary, the use of alternate means of venting could be initiated.
I VI. Assessment of Consequences - Emergency Boiler Feed Valve EBF-MOV-557 was successfully surveillance tested monthly during the time period in question. This valve provides an alternate flow path i
for emergency boiler feed water via the steam generator blowdown
. lines.
The normal emergency boiler feed flow path was still operable l
as were other diverse flow paths and pumps available to feed the steam l
generators. These diverse capabilities to supply emergency boiler l
feed water to the steam generators are specified in Plant procedure OP-3203, " Loss of Feedwater." The flow paths are as follows:
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. FYR 86-088 A.
No. I or No. 2 EFWP via the normal flow path.
l B.
No. 2 EFWP via the blowdown cross connection.
C.
No. 1 EFWP via the blowdown cross connection.
D.
Steam driven emergency feedwater pump (ST-EFWP) via the normal flow path.
E.
ST-EFWP via the blowdown cross connection.
l F.
Charging pumps via the emergency feedline spool piece to the j
normal feedwater flow path.
j G.
Charging pumps via the blowdown cross connection.
H.
Safety injection pumps via the blowdown cross connection (use this as a last resort since this pumps SI water into steam i
generators),
i EBF-MOV-557 would be utilized in option B, C and E.
It should be j
noted that these optional flow paths would only be used if the normal j
emergency feedwater flowpath A was unavailable.
The Yankee Plant's steam generators are conservatively designed with a i
heat sink capability of close to one hour after a scram with no feedwater flow.
EBF-MOV-557 could be manually opened by the Primary Auxiliary Operator, if necessary.
There vould be ample time to either manually open EBF-MOV-557 or use an altrrnate means of feeding the steam generators.
l VII. CONCLUSIONS The results of the task force investigation found no generic breakdown j
in the receipt inspection program or design change program.
It is the conclusion of the task force that the root cause of this event was the ambiguous description of requested equipment on the particular purchase order, concurrent with an inadequate receipt inspection and insufficient post installation testing of this equipment.
1 VIII. CORRECTIVE STEPS WHICH HAVE BEEN TAKEN AND RESULTS ACHIEVED The undersized overload trip coils were replaced with suitably sized trip coils and the MOV's were tested and released for service on June 27, 1986. The plant cognizant engineer involved in this incident was reinstructed on June 30, 1986.
This incident was discussed at PORC meeting No. 86-42 on July 1, 1986. The PORC members were reminded of the need for vigilance when reviewing installation and test procedures.
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! FYR 86-088 An extensive review was conducted of Guild Switchgear, Electrical Design Changes initiated since 1981 as well as a sampling of I&C and Mechanical Design Changes. A verification of a sampling of spare parts in the stock room was also conducted.
The above actions are described in more detail in Part III of this response.
IX. CORRECTIVE STEPS WHICH WILL BE TAKEN TO AVOID FURTHER VIOLATIONS
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The recommendations specified in Section II of this response are scheduled to be implemented as soon as practical, and in no event 1
later than February 28, 1987.
In addition, final resolution of discrepancies that did not effect operability of equipment will be completed during the next refueling outage currently scheduled for May 1
-1987.
X.
THE DATE WHEN FULL COMPLIANCE WITH BE ACHIEVED Full compliance was achieved on June 27, 1986, with the replacement of the undersized trip coils and the testing and release for service of the MOV's.
l If you have any questions or desire additional information, please contact us.
Sincerely,
. H. Heider Vice President and Manager of Operations BLD/nm i
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