ML20080F867
| ML20080F867 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 02/18/1994 |
| From: | Berg S COMMONWEALTH EDISON CO. |
| To: | Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 9501310327 | |
| Download: ML20080F867 (11) | |
Text
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Mr. J.
B. Martin
,- p Regional Administrator U.
S.
Nuclear Regulatory Commission Region III 801 Warrenville-Road Lisle, Illinois 60532-4351
Subject:
Braidwood Station Units 1 and 2 Request for Issuance of Notice of Enforcement Discretion to Technical Specifications 3.0.3.
NRC Docket Numbers 50-456 and 50-457
Dear Mr. Martin:
The purpose of this letter is to document the results of a teleconference between Commonwealth Edison Company (CECO) and the Nuclear Regulatory Commission (NRC) staff on February 18, 1994, in which Ceco requested issuance of a Notice of Enforcement Discretion (NOED) from Technical Specification 3.0.3 for Braidwood Station Units 1 and 2.
At the time of the teleconference Unit I was in Mode 1 and Unit 2 was in Mode 1.
On February 18, 1994, at 14 05 (CDT), Braidwood Units 1 and-2 entered Technical Specification 3.0.3 due to the inoperable status of both trains of the Control Room Ventilation system.
CECO requested that the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> allowed outage time be extended an additional 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in order to allow time to restore one train a-of the control room ventilation system to an operable status.
With tha vertoration of operability to one train, the action i
statement ;or Technical Specification 3.7.6 will apply until the i
remaining train is declared operable.
A Notice of Enforcement Discretion was verbally approved by Region III at 1600 (QDT) on February 18, 1994.
i The basis of the request is provided in Attachment 1 and includes:
The Technical Specification that will be violated; The circumstances surrounding the condition, including the need for prompt action; i
The safety basis for the request that enforcement
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discretion be exercised, including an evaluation of the safety significance and potential consequences of the i
proposed course of action; Any proposed compensatory measure (s);
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The justification for the duration of the request;
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9501310327 940218 d
PDR ADOCR O5000456 G
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Mr. Martin February 18, 1994 i
The basis for the conclusion that the request will not have a potential adverse impact on the public' health and safety and that a significant safety hazard is not involved; and i
The_ basis for the conclusion that the request will not involve adverse consequences to the environment.
I
' (a list of affected dampers) and Attachment 3 (a simplified drawing of the control room ventilation system) are provided for your review.
f If at least one train of the control room ventilation system is 4
not restored to operable status by 1505 (CDT) on February 21, I
1994, the units will be placed in hot standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, hot shutdown within e next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and cold shutdown within the following 24 h cs, per Technical Specification 3.0.3.
This request for Enforcement Discretion has been reviewed and approved by Braidwood On-Site Review Committee, in accordance with Braidwood Station procedures.
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Ceco sincerely appreciates the NRC staff's effort and participation in the review of this request.
Please direct any
_ questions or comments to Allan Haeger at (815)458-2801 extension 2702.
4 Very Truly Yours, 9
{
.c Ann nS gval M.
erg Jr.
Site Vice President Braidwood Station
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Attachments f
cc:
S.
DuPont, Resident Inspector-Braidwood i
R. Assa, Project Manager-NRR B.
Clayton, Branch Chief-RIII NRC Document Control f
a t
f ATTACEMENT 1.
REQUEST FOR ENFORCEMENT DISCRETION BRAIDWOOD STATION UNITS 1 & 2 February 18, 1994 1.
TECHNICAL SPECIFICATION OR LICENSING CONDITION THAT WILL BE VIOLATED At 1405 hours0.0163 days <br />0.39 hours <br />0.00232 weeks <br />5.346025e-4 months <br /> on February 18, 1994 P~-'dwood declared Train A and Train B of Main Control Room venti]
) inoperable and entered Technical Specification Action Stat.e 3.0J for Units 1 & 2.
Technical Specification 3.7.6 requi that the two main control a
room ventilation systems be operable in all MODES.
With two trains of main control room ventilation inoperable while in MODES 1-4, Technical Specification 3.0.3 must be entered.
Braidwood Units 1 & 2 are currently in MODE 1.
Technical Specification 3.0.3 requires action within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to place the unit in a MODE where-the specification (3.7.6) does not apply.
The affected unit (Units 1 & 2 in this case) must be placed in HOT STANDBY within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, HOT SHUTDOWN within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and COLD SHUTDOWN within the next 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Braidwood is requesting enforcement discretion to allow continued operations for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> with both trains of control ventilation inoperable.
This requested period will permit restoration of at least one train of control room ventilation to operable status.
2.
CIRCUMSTANCES SURROUNDING THE SITUATION on Feb. 17, 1994 Braidwood System Engineering became aware that backup batteries supplying certain dampers in Trains A & B of main control room ventilation had not received preventative maintenance for an extended period of time.
The affected dampers, termed " bubble tight dampers", are designed to isolate unfiltered air paths to control room ventilation and allow the makeup filter unit to maintain positive control room envelope pressure during a accident conditions (Attachment 2 contains a listing of the affected dampers in both trains; is a simplified drawing of Train A Control Room Ventilation).
Four hydraulically operated dampers in each train receive power from individual backup batteries in the event of a loss of safety related AC power, which would include the Emergency Diesel Generators, to the damper in order to close the dampers and to maintain them in a closed position.
The hydraulic pumps for the affected dampers are normally powered from safety related ESF power supplies.
An investigation was undertaken to determine the condition of these batteries.
Subsequently, on February 18, 1994 voltage measurement testing was completed.
All Train A batteries were determined to have less than the minimum acceptable voltage, thus rendering four Train A dampers inoperable. Three of four dampers in Train B were also determined to be inopercble.
The affected daspers are currently in the closed position.
Train A is currently in emergency makeup mode.
Train B is shutdown and available.
The control room ventilation system is. currently maintaining positive pressure, as designed, with respect to its surroundings.
3.
EVALUATION OF SAFETY SIGNIFICANCE AND CONSEQUENCES The control room ventilation system is common to both Units 1 and 2 and serves the control room, auxiliary electric equipment rooms, upper cable spreading rooms, ventilation equipment room, security control center, record room and miscellaneous locker i
room, toilets, kitchen, and storage rooms.
It is a Safety Category I system designed to provide environmental conditions i
conducive to habitability and long component life in the control room under normal and abnormal station conditions.
The system conforms to NRC General Design Criteria 19 (GDC 19) and is designed with redundancy to meet the single failure criteria.
On receipt of an ESF actuation to the control room ventilation system, the operating train will realign to the emergency makeup mode.
The affected dampers in both ventilation trains close to isolate unfiltered air paths and allow the makeup filter unit to maintain positive control room envelope pressure.
In addition to ensuring habitability during accident conditions, the ventilation system also may be realigned upon notification of an offsite chlorine event near Braidwood.
The control room outside air intakes would be manually isolated by the control room operators and the main control room ventilation system would be operated in 100% recirculation mode.
Braidwood believes the safety significance of granting this enforcement is low for the following reasons:
If a loss of safety related power (AC) to one train of centrol room ventilation were to occur, Braidwood Station's engineering judgement is that the remaining train is capable of maintaining positive pressure in the control room envelope with respect its surroundings.
This judgement is based on the fact that the remaining dampera in the ventilation system.will fail closed.
These remaining dampers, while not leak tight, are downstream of the affected dampers and will provide isolation to the affected dampers.
This will minimize unfiltered in-leakage to the control room envelope.
Any in-leakage which does occur will be filtered.
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The iodine source ters assumed in accident analysis has been found to be extremely conservative.
The actual source term is expected to be significently less than the assumed value.
A more detailed discussion of the the' source term is located in Section 6, Significant Hazards Considerations.
The probability of Loss of Coolant Accident (LOCA) and a L
Loss of Off-Site Power (LOOP)4 event for the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> requested is less than the 10 acceptance criteria.
Braidwood PRA data was used to estimate the frequency of these events for the requested enforcement discretion period.
The probability of a chlorine release event has been shown to be less the 104 acceptance criteria.
Braidwood has submitted a Technical Specification amendment containing the evaluation of the probability of a chlorine event.
The probability of this event has been reduced based upon the removal of nearby railroad tracks which once potentially transported chlorine.
Granting of this enforcement discretion would allow for repairs to at least one train of main control room ventilation without shutting down Braidwood Unit 1 & 2.
4.
COMPENSATORY ACTIONS The following compensatory measures will be in place for the duration of the waiver period:
No ESF electrical distribution equipment, either normal, standby, or reserve, will be taken Out-of-Service on Unit 1 or Unit 2.
The Southern Division Load Dispatcher will be notified to maximize the availcbility.of the offsite power lines l
servicing Braidwood.
The Southern Division Load Dispatcher will be notified to i
refrain from work activities in the Braidwood switchyard.
Availability of all Unit 1 and 2 safety related equipment will be maximized by prohibiting planned maintenance on safety related equipment.
The Shif t Management will review all surveillences and out-of-Services for impact before authorizing the initiation of the activity.
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The operating train of VC.will remain in the emergency makeup mode.
Dampers for the non-operating train will remain aligned to ensure a positive pressure in the control i
room envelope.
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Self contained breathing apparatus (SCBA) will be provided for all assigned main control room personnel.
t All shift operating personnel will be notified of these compensatory action via Daily Orders.
5.
JUSTIFICATION FOR THE DURATION OF THE REQUEST:
The requested allowed outage time extension is 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
This time is requested to restore a single train of control room ventilation to operable status.
There are two engineering methods being considered to restore the ventilation trains to operable status.
The longer of these methods could take up to the requested 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
If at least one trein of control room ventilation is not restored at the end of 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> requested extension, Braidwood will comply with the actions of Technical Specification 3.0.3 to place both Unit 1 & 2 in HOT STANDBY within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, HOT SHUTDOWN within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and COLD SHUTDOWN within the i
following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
When'a single train of control room ventilation is restored to operable status, Braidwood will terminate the Enforcement Discretion and enter into the Technical I
Specification 3.7.6 Action Statement for MODES 1-4.
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Technical Specification 3.7.6 Action Statement for MO:.)ES 1-4 which allows 7 days to restore a single inoperable train of control-room ventilation, will run concurrently with the requested enforcement discretion.
Thus, the remaining train of control room ventilation will be restored to operable status by 1405 hours0.0163 days <br />0.39 hours <br />0.00232 weeks <br />5.346025e-4 months <br /> on February 25, 1994, or Braidwood will comply with the remainder of Specification 3.7.6 requiring both Units be in HOT STANDBY in the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the next 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
Commonwealth Edison believes that one train of control room ventilation will be restored within the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> requested.
The safety significance associated with the duration of this request is minimal.
The operating VC train will be maintained in the emergency makeup (accident) mode and the non-operating train will remain aligned to ensure positive pressure in the control i
envelope.
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6.
EVALUATION OF SIGNIFICANT EAEARD CONSIDERATION:
Commonwealth Edison has evaluated the proposed enforcement discretion and. determined that it involves no significant hazards considerations.
According to 10 CFR 50.92(c), a proposed amendment to an operating license involves no significant hazards considerations if operation of the facility in accordance with the proposed amendment would not:
1.
Involve a significant increase in the probability or consequences of an accident previously evaluated; or I
2.
Create the possibility of a new or different kind of accident from any accident previously evaluated; or 3.
Involve a significant reduction in a margin of safety.
a.
The propcsed enforcement discretion does not involve a significant increase in the probability or consequences of an accident previously evaluated.
The probability of an accident occurring will not be af fected by granting this enforcement discretion.
This request deals only with the allowed outage of equipment assumed to be operated for the mitigation of an accident.
The availability of this equipment is unrelated to the sequence of events leading to the initiation of a transient, and is therefore unrelated to the probability of occurrence for a transient initiating event.
However, the frequency of coincident occurrences of a Loss of Coolant Accident and a Loss of Offsite Power during the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period has been calculated as 1.1 x 10*.
The consequences of an accident, in terms of offsite dose, will remain unchanged provided the mitigative actions credited in the UFSAR Chapter 15 Accident Analyses are accomplished in accordance with the analyses assumptions.
The operating train of VC will remain in the emergency makeup (accident) mode and non-operating train dampers will remain aligned to ensure positive pressure in the control room envelope.
Furthermore, the iodine source term assumed in accident analysis has been found to be overly conservative.
The source term, for which the need for bubble-tight damper integrity evolved included iodine as an elemental, vaporous constituent. Current source term understanding is not in accord with this earlier model. Work done since TMI, by the NRC and industry has shown that the iodine will be released as Cesium Iodide (CsI) and will form aerosols very rapidly. The mobility of the CsI is much reduced over vaporous, elemental iodine.
Therefore, leakage rates and infiltration rates are only a small fraction of that assumed in the UFSAR analyses.
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Therefore, the requested enforcement discretion does not significantly increase the probability cnr consequences of an accident previously evaluated.
b.
The proposed enforcement discretion does not create the possibility of a new or different kind of accident from any accident previously evaluated.
The operating control room ventilation system will remain in the emergency makeup (accident) mode.
This is the mode of operation assumed in the UFSAR to maintain control habitability during an accident.
The non-operating train will remain aligned to maintain a positive pressure in the control room envelope.
No new system configurations are introduced, and no equipment is being operated in a new or different manner than has been previously analyzed.
Accordingly, no new or different failure modes are being created.
The proposed enforcement discretion does not involve a c.
significant reduction in a margin of safety.
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The extension of the allowed outage time is in a non-conservative direction.
However, there is minimal reduction in the design margin of safety.
Engineering judgement is that the remaining train is capable of maintaining positive pressure in the control room envelope with respect to its surroundings.
In addition, sufficient compensatory measures, including maintaining an operating train in emergency makeup mode, will ensure the ventilation system will perform its design function during the unlikely event of an accident.
Based on the review above, Braidwood concludes that this request i
i for enforcement discretion does not involve a significant hazards consideration.
7.
ENVIRONMENTAL ASSESSMENT:
I Braidwood has evaluated the proposed enforcement discretion against the criteria for the identification of licensing and regulatory actions requiring environmental assessment in accordance with 10 CFR 51.21.
It has been determined that the proposed change meets the criteria for a categorical exclusion as provided for under 10 CFR 51.22 (c) (9).
This determination is based on the fact that this change is being proposed as enforcement discretion to a license issued pursuant to 10 CFR 50, and that the changed requested involves extension of the Allowed Outage Time of a component located within the restricted area, and the change involves no significant hazards.
There is no change in effluents that may be released offsite.
There is no significant increase in individual or cumulative occupational radiation exposure.
4.
APPROVAL BY ON SITE REVIEW'.
This request has been reviewed and approved by the Braidwood On-site Review Committee, in accordance with the Braidwood Station procedures.
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ATTACID(ENT 2 Affected VC Dampers Valve Description Train A Train B Purge Exhaust Damper OVC18Y OVCO2Y Outside Air Purge Intake Damper OVC20Y OVC04Y Control Room HVAC Outside Air OVC281Y OVC16Y Makeup Damper Alternate Emergency Makeup OVC312Y OVC313Y Intake from Outside i
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