ML20082B884
| ML20082B884 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 07/10/1991 |
| From: | Horn G NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20082B887 | List: |
| References | |
| NLS9100446, NUDOCS 9107170112 | |
| Download: ML20082B884 (8) | |
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GENERAL OFFICE
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P.O BOX 499. COLUMBUS 1NEDRASKA 686024499 h:41 Nebraska Public Power Dictrict
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NLS91044f July 10, 1991 U. S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Subj ec t:
Emergency Technical Specification Change Proposed Change No. 98 "EmerLency Buses Loss of Voltage Relays Setting Limit" Cooper Nuclear Station NRC Docket No. 50 298, DPR-46
References:
1)
Telecon between J. M. Meacham (NPPD) and John Zwolinski (NRC) on July 9,1991 Request for Waiver of Compliance 2)
Letter from C, Lear (NRC) to J. M. Pilant (NPPD) dated April 11, 1978, CNS Amendment No. 43 3)
Letter from J, M. Pflant (NPPD) to D.
K.
Davis (NRC) dated July 18,
- 1977,
" Electrical Under Voltage Protection" t)
Letter from NRC to J. M.
Pilant June 3, 1977, " Safety Evaluation and Statement of Staff Position Relative to the Emergency Power Systems" Centlemen:
The pwpose of this letter is to document information provided to NRC personnel regarding the Nebraska Public Power District's (the District's) request for a Waiver of Compliance concerning Technical Specification action statements reBarding the inoperabiliry of the Emergency Bus Loss of Voltage Relays. In addition, a request for an emergency license amendment to change the voltage setting of the Loss of Voltage Relays is attached.
During the course of the District's Design Basis Review of the Standby AC Power System, the design settings of Loss of Voltage Relays were determined to be outside of the settings limits specified in the CNS Technical Specifications.
The relays at issue are listed in CNS Technical Specifications Table 3.2.B, Page 55; they are identified as follows:
27/1FA 1 27/1CB-1 27/1F-1 27/10 1 27/ET-1 27/ET-2 The Technical Specifications setting lim ; for these relays is listed as ?900 V five percent, five seconds one se::ond time delay.
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4 NLS9100446 i
Page 2 July 10, 1991 The Station Operations Review Committee (SORC) was notified that these relay settings were not in compliance with the CNS Technical Specifications.
SORC formally reviewed and approved an Operability Evaluation and a Justification for Contis.ned Operation for this condition, prior to the District contacting the NRC J
(Reference 1) requesting the Vaiver of compliance.
During the telecon (Reference 1), the District verbally provided information to be-used by NRC personnel in deciding the appropriateness of granting a Vaiver of Compliance. _The information provided by the District during the Telecon'is documented below as responses to indicated subjects.
The subjects addressed below are in accordance with the February 22, 1990 T.
E.
Murley memorandum addressing the administration and content of waivers of compliance.
1.
Discussion of the Requirements for Vbich a Vaiver is Requested I
Renconse Ccoper Nuclear Station Technical Specification 3.2.B.
" Core and Containment Cooling Systems Initiation and Centrol" states that instrumentation given in Table 3.2.B must be operable when ' the 6
system (s) it hitiates or controls are required to be operable as specified elsewhere in the Technical Specifications, Included in Table 3.2,B on page 55 are the Emergency Buses Loss of Voltage Relays identified above with a specified set *ing limit of 2900 Volt.;
five percent, five seconds 1 second time delay. The actual voltage settings and time delay for these relays are not in conformance with the Technical Specification requirements.
Table 3.2.B.
(RHR system Low Pressure Coolant Injection Mode),
specifies _ that when component operability is not assured, the syst.em l
or component is to be declared inoperable. Present plant operating conditions require _ these systems to_be operable; therefore, the subject relays are also required to be operable.
Technical Specification 3,9.A.1.C.1 also requires that the loss of j
voltage' relays and their auxiliary relays are to be operable when the 4160 Volt Critical Bures IP and 1C are energized.
Technical Specification ' 1. 0,J (Definition) states that, "In the event a LCO cannot be satisfied because of circumstances in excess of those addressed in the specification, the facility shall be placed in HOT SHUTDOWN 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 /> unless corrective _ measures are completed that permit L
operatic.n under the LCO for the specified time interval as measured from initial discovery.
Exception to these requirements shall be stated 'in the individual specifications."
None of the-specifications given above (3.2.B and 3.9.A.1,C 1) have stated exceptions to this shutdown requiremant, Corrective measures to adjust the relay voltage setting limit to the given Technical Specification value are not prudent since evaluation concludes that
A NLS9100446 Page 3 July 10,1991 with the present relay se t t1.ng.
the plant remains within its analyzed licensing basis.
2.
Discussion of Circumstances Surrounding the Situation Inc.luding the Need for Prompt Act ad a Description of Why the Situation Could Not be Avoided
Response
The situation was discovered luring the perfm mance of a design basis review of various electrical distribution equipment conducted as part of the District's ongoing Design Basis Program. At the timo of discovery, plant conditions required the Loss of Voltage Relays to be operable, and as discussed above, necessitated entering a six hour action statement to place the pir.nt in hot shutdown.
The inconsistency between the Technical Specification voltage and time delay setting and the actual relay voltage and time delay setting has existed since che Loss of Voltage Relays were incorporated into Technical Specifications by Reference 2.
The original relays, as loss cf voltage relays, were set to operate on a decreasing (to zero) loss of voltage.
At less than 2900 volts decreasing, the relays were set to clear the bustes and start the Emargency Dierel Cer.entors within about five seconds. The actual response of the relaya is dependent upon the speed at which bus voltage collapses.
For a rapidly decreasing voltage, a more rapid relay responst is desired. In the case of a prompt drop to zero bus volts, the telays will respond in about 1.4 seconds.
This is the desired effect and is how the plant was designed, constructed and s urve il'.e d.
In response to an NRC S*aff request (Reference 4), the District ptoposed changes to
. te Cooper Nuclear Station Technical Specifications. The existing design had been previously described and the request was for the addition of the setting limit, reflective of actual plant configuration.
The Staff guidance requested a voltage setpoint and time delay with tolerances. In the proposed change, the District submitted 2900 volts and five seconds, with tolerances. These values wen intended to be upper bounds for the actuation of the loss of voltage relays. Restated, the relays should respond at about 2900 volts decreasing and complete their safety fanction within about five (5) seconds.
It was never the District's intention that the relays should respond to a ntatic voltage (i.e.,
degraded) within four to six seconds.
That is a function of the second level or degraded voltage relays.
As the Technical Specifications were proposed for modification and approved by the NRC, a different intent of the function and response of the relays is implied. The attached Proposed Change will clarify the purpose and correct response of the relays in question.
1 NLS9100446 Page 4 July 10,1991 3.
Discussion of Compensatory Actions
Response
No compensatory actions are needed during the processing of this request.
Evaluation has shown that the plant will respond in the manner and within specified time limits as given by current accident analyses.
4.
Safety Significance and Potential Consequences
Response
The District performed a Preliminary Evaluation of the sa fe ty significance and potential consequences of maintaining the existing loss of voltage relay. settings and obtaining a Waiver of Compliance from the listed relay settings in Technical Specifications.
The existing relay settings, although not in conformance with the settings -in Technical Specifications, are consistent with the original Design Basis settings.
The District has reaffirmed that the existing setting is valid. This setting, which uniquely defines an inverse time-voltage characteristic operating curve for the relay, results in-the relay performing all required safety related actions upon loss of bus voltage.
This allows the Emergency AC Electrical Distribution System to operate as described in the USAR and Technical Specifications bases.
Additionallyr the District has determined that the Loss of Voltage settings listed in Technical Specifications are misstated.
The listed Technical Specifications 1.oss of Voltage settings, which were proposed by the District in a subt.ittal associated with Amendment Number 43, resulted from a misstating of the settin5 which would define the existing inverse Time-Voltage characteristic operating curve of the ' Loss of Voltage Relays.
Since the existing relay settings are within the Plant Design Basis, and ate consistent with the Operational Transient. and Accident Analysis of the USAR, the District has determined that there is no safety significance resulting from the Waiver of Compliance and the maintenance of the existing relay settings.
As the emergency electrical distribution system will continue to operate within the Design Basis - assumed in the Operational Transient and Accident Analysis, the District has also determined that there would be no adverse consequences resulting from a Waiver of Compliance from the Loss of Voltage Relay settings listed on Technical Specifications Table 3.2.B.
5.
Justification of Requist. Duration
Response
l The' condition requiring the Waiver of Comp 1: ance is a permanent condition. To correct the condition, an Amendment to CNS Technical I
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NLS9100446 page 5 July 10, 1991 Specifications is required. The duration of the requested Waiver of Compliance is until July 18, 1991, which provides twenty four hours for the District to prepare a request for an Emergency License Amendment Request and five working dayr for the NRC's review and
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evaluation, This schedule was discussed with the NRC during the July 9, 1991 telecon and determined to be acceptable.
6 Basis for the Conclusion that the Request Does Not Involve a Si nificant Hazards Consideration Response 6
Resoonse The existing relay -setting, which doncribes a unique relay time-voltage characteristic curve, is the same setting determined during the original design, and is documented in the original design basts, _ Threfore, the axisting relay setting is the value assumed in the Operational Tr ansient and Accident Analysis, and maintaining this setting will - not involve a significant increase in the p.obability or consequences of an accident previously evaluated in the_ Updated Safety Analysis Report (USAR).
Since-the maintenance of the existing setting does not inttoduce a
, change to the Design Basis, it does not create the possibility of a new or different kind of accident from any accident previously evaluated in the USAR.
The District's evaluation of the existing 4
setting of tho-Loss of Voltage Relays determined that the relays woul d - perform their safety related functions -as designed.
i g
Maintenance of' the existing relay setting woeld not result in a l_
significant reduction in the margin of safety.
From this, the District has concluded that the maintenance of the existing setting of the Loss of Voltage Relays does not involve a significant hazards
-consideration.
This evaluation is addressed in further-detail in the attached proposed change.
7.
Basis for the Conclusion that the Request Does Not Involve Irreversible Environmental Consequences-H, Resnonne The current settings of the Lots of Voltage Rolays are consistent with the - Design Basis assumed in the Operational _ Transient and j'
Accident Analysis. Radiological releases for Transient or Accident Events will be maintained within analyzed limits. Maintaining this setting will not result in any irreversible environmental consequences.
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' A-verbal-Waiver of Compliance was granted by the NRC during Reference 1 based o.
this verbal-information and the District's commitment to provide a writtet.
request for.a waiver of compliance containing this information (this letter).
The granted _Vaiver of Compliance allowed the District te waive the action l
requirements of Technical Specification 1.0,J.
while an Emergency Technical Specification change request was being submitted and evaluated.
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m NLS9100446 Page 6-July 10,_1991 4
Accordingly, < the District hereby requests an emergency change to the Cooper
- Nuclear Station-Technical Specifications to revise the setting limits for the Loss'of_ Voltage Relays,
-Attachment I con:ains a detailed description of the proposed change and the
-- results of the evaluation of the proposed change with respect to 10 CFR 50,92.
Also, enchsed is revised Technical Specification Page 55, the page affected by the proposed change.
This proposed chango is considered an Fmergency Technical Specification Change because, witaout the expedited approval of the revised Loss of Voltage Relay -
Setting Limits, CNS will be in vic,lation of the Loss of Voltage Relay Technical Specification Setting Limits as revised by Amendment 43 (Reference 2),
A discussion of the pertinent events leading up to the issuance of this submittal is as follows: The-relays,-less 27/ET 2 (added by Amendment 75), were included in the CNS Technical-Specifications as Amendment 43, dated April 11, 1978, (Reference 2),
The proposed addition of the relays as Technical Specification items (Reference._ ?) was in response to an NRC request dated June 3,
- 1977, (Reference 4)._ This request addressed the susceptibility of the onsito emergency power system to sustained degraded grid voltage conditions at the offsite power
- source and the interactions between the offsite and on-site emergency power Lsystems.
It also requested that, if necessary, modifica.; ions be made and that Technical Specification changes be submitted to comply with the Staff's position.
Reference 3 detailed the operation of the Loss of Voltage Relays and included them in the Technical Specifications s'ue to their initiation of diesel generator starting and load shedding logic, Additionally, the submittal proposed the addition of - pdervoltage_ relays to provide second level protection for the on site power. system.
The existing Loss of Voltage Relays'were described as
- operating "on decreasing' voltage at 2900 V."
The District's proposed change to the Technical Specification listed the relay setting as 2900 V i five percent, five. seconds 1 one second delay.
With the addition of the second level undervoltage protection, the-first 1cvel l
relays need only detect _a loss of voltage and not degraded votrage conditions.
l.
- The actual setpoint is somewhat arbitrary, provided the setpoint does not create spurioustransfers, or diesel starts, and does initiate load shedding in the required time,
_1t should be noted that tne second level unc'i. voltage relays i
- independently trip the tie breaker. The trip of the tie brem will create a L
complete -loss of voltage, when this loss of voltage occurs, the loss of voltage relays, as currently set in the plant, will respond as designed and quickly clear -
the buses.
T4.e Emergency AC System will respond as described in the Updated Safety - Analysis Report (USAR) and the CNS Technical Specification Section 3.9 BASES,.bec.use there i
.io loi,s of function over the entire range of voltage l
f(normal.to zord.
Although there was extensive communicatMn with the NRC concerning the operation of these relays, the basis for the published setting is unclear. It is believed to be the result of an incorrect translation of the original Burns and Roe (CNS 1
architect en6 ncer) calculation.
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1 NLS9100446
- Page - 7 July 10, 1991 Therefore, as described _in Attachment 1, _. the first. level undervoltage relays (Loss of Voltage Relays) are not adjusted or calibrated to the published setpoint described;in CNS_ Technical Specification Table 3.2.B. however, they continue to perform'their safety functions as designed. These safety functions are described in-the BASES of Section 3.9 of the CNS Technical Specifications and in the USAR.
Mr. H. R. Borchert, Nebraska Department of Health, has been notified by telephone of the circumstances at Cooper Nuclear Station, and=is being copied on this letter in accordance with 10 CFR 50.91(b)(1). This proposed change incorporates all Amendments to' the Cooper Nuclear Station Facility Operating License through Amendment 142 issued May 22, 1991. This proposed change nas been reviewed by the necessary_ Safety Review: Committees and copies are being sent to the NRC Region IV Office and the CNS Senior Resident inspector in accordance with 10 CFR 50.4(b) (2). In addition to the original, 37 copies are also submitted for
-your use.
- This proposed _ license amendment involves a change to a setting limit as defined in Table 3.2.B of the CNS Technical Specifications. The District has determined that this amendment involves no significant increase in the - amounts, and no significant change in the type, of any effluent that may be released off site, and that there is no significant increase in individual or cumulative occupational radiation exposure.
Accordingly, the District is of the opinion that this amendment would meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental
-impact statement or environmental assessment need be prepared in connection with-this amendment.
Should you have any questions or require additional information, please contact this office.
' Sin.rel,
J' Gw O. R. Horn Nuclear Power Croup Manager CRH/tj a:chng98
' Attachment ec:
H. R.'Borchert Department of Health State of Nebraska NRC Regional Administrator Region IV - Arlington,-TX NRC Senior Resident Inspector 4
Cooper Nuclear Station
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t NLS9100446 Page 8 July 10, 1991 STATE OF NEBRASKA )
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PlATTE COUNTY
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. C. R. Ilorn, being first duly sworn, deposes and says that he is an authorized l
representative of the Nebraska Public Power District, a public corporation and political subdivision of the State of Nebraska; that he is duly authorized to subtait this request on behalf of Nebraska Public Power District; and that the i
statements contained herein are true to the best of his-knowledge and belief.
Y W._.
. R. Ilorn Subscribed in my presence d sworn to before me this I O 4-h day of
._. R f.o _
1991.
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