CNL-15-225, Application to Revise Technical Specifications for Ice Condenser Door Surveillances (TS-WBN2-15-19): Difference between revisions
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DESCRIPTION | DESCRIPTION | ||
2.0 DETAILED DESCRIPTION | |||
DESCRIPTION | |||
==3.0 TECHNICAL EVALUATION== | ==3.0 TECHNICAL EVALUATION== | ||
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DESCRIPTION Pursuant to Title 10 of the Code of Federal Regulations (CFR) §50.90, Tennessee Valley Authority (TVA) is submitting a request for an amendment to Facility Operating License No. NPF-96 for Watts Bar Nuclear Plant (WBN) Unit 2. The proposed amendment will modify Technical Specification (TS) 3.6.12, "Ice Condenser Doors," Surveillance Requirements (SRs) 3.6.12.3 through 3.6.12.5 for the ice condenser lower inlet doors during the first cycle after the receipt of the Operating License. | DESCRIPTION Pursuant to Title 10 of the Code of Federal Regulations (CFR) §50.90, Tennessee Valley Authority (TVA) is submitting a request for an amendment to Facility Operating License No. NPF-96 for Watts Bar Nuclear Plant (WBN) Unit 2. The proposed amendment will modify Technical Specification (TS) 3.6.12, "Ice Condenser Doors," Surveillance Requirements (SRs) 3.6.12.3 through 3.6.12.5 for the ice condenser lower inlet doors during the first cycle after the receipt of the Operating License. | ||
The proposed amendment is required to allow continued operation of WBN Unit 2 during the summer of 2016 and preclude a shutdown of the unit. | The proposed amendment is required to allow continued operation of WBN Unit 2 during the summer of 2016 and preclude a shutdown of the unit. | ||
2.0 DETAILED DESCRIPTION Proposed Amendment Surveillance Requirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 have a performance frequency of 18 months except for the first year of operation. In the first year of plant operation, these surveillances are to be performed every three months. TVA is proposing to perform the surveillance within 90 days of entering MODE 4 for the first time and then 180 days thereafter for the first operating cycle. The proposed revision to the SRs was discussed in a November 19, 2015 public meeting between the Nuclear Regulatory Commission and TVA. | |||
DESCRIPTION Proposed Amendment Surveillance Requirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 have a performance frequency of 18 months except for the first year of operation. In the first year of plant operation, these surveillances are to be performed every three months. TVA is proposing to perform the surveillance within 90 days of entering MODE 4 for the first time and then 180 days thereafter for the first operating cycle. The proposed revision to the SRs was discussed in a November 19, 2015 public meeting between the Nuclear Regulatory Commission and TVA. | |||
==3.0 TECHNICAL EVALUATION== | ==3.0 TECHNICAL EVALUATION== | ||
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The frequent surveillance testing intervals initially required were reasonable given that there was no operating experience, testing done at Westinghouse Electric Corporation Waltz Mill Facility could not replicate containment environmental conditions with respect to lower inlet door performance during normal operation, and the safety importance of the ice condenser in assuring containment integrity in the event of a Loss of Coolant Accident (LOCA) or other DBA. The current surveillance frequency, typically 18 months, is supported by many years of ice condenser operating experience with few failures of the doors to meet the acceptance criteria. None of the failures that have occurred were found to be safety significant. | The frequent surveillance testing intervals initially required were reasonable given that there was no operating experience, testing done at Westinghouse Electric Corporation Waltz Mill Facility could not replicate containment environmental conditions with respect to lower inlet door performance during normal operation, and the safety importance of the ice condenser in assuring containment integrity in the event of a Loss of Coolant Accident (LOCA) or other DBA. The current surveillance frequency, typically 18 months, is supported by many years of ice condenser operating experience with few failures of the doors to meet the acceptance criteria. None of the failures that have occurred were found to be safety significant. | ||
The following discussion provides the basis for revising the surveillance frequency for each of the SRs. | The following discussion provides the basis for revising the surveillance frequency for each of the SRs. | ||
3.2.1 Surveillance Requirement 3.6.12.3 | |||
Requirement 3.6.12.3 | |||
This SR requires inspection of the ice condenser lower inlet doors to identify ice, frost or debris which may restrict their opening in a design basis event. Data from WBN Unit 1 performances of the SR going back to issuance of the Low Power License in November 1995, indicates that ice, frost or debris have not been a problem. There was one instance identified in February 1999 where frost build-up was sufficient to increase the opening torque for some doors beyond the value allowed in SR 3.6.12.4. | This SR requires inspection of the ice condenser lower inlet doors to identify ice, frost or debris which may restrict their opening in a design basis event. Data from WBN Unit 1 performances of the SR going back to issuance of the Low Power License in November 1995, indicates that ice, frost or debris have not been a problem. There was one instance identified in February 1999 where frost build-up was sufficient to increase the opening torque for some doors beyond the value allowed in SR 3.6.12.4. | ||
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not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extend beyond the currently planned end of cycle date. | not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extend beyond the currently planned end of cycle date. | ||
Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public. | Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public. | ||
3.2.2 Surveillance Requirement 3.6.12.4 This SR requires verification that the torque required to open the lower inlet doors is less than or equal to 675 inch-lbs. This verification provides assurance that no doors become stuck in the closed position during a design basis event such as a large break LOCA. Testing of the doors on WBN Unit 1 show the values obtained were within the acceptance criteria and ranged from 160.5 inch-lbs to 601.9 inch-lbs. As was discussed in Section 3.2.1, it was generally the performance of this surveillance that identified some level of ice build-up on one or more lower inlet doors. WBN Unit 1 has not experienced a failure of this surveillance other than the one described earlier that occurred in 1999. The industry information shows that the identification of ice build-up is associated with the performance of this surveillance. | |||
Requirement 3.6.12.4 This SR requires verification that the torque required to open the lower inlet doors is less than or equal to 675 inch-lbs. This verification provides assurance that no doors become stuck in the closed position during a design basis event such as a large break LOCA. Testing of the doors on WBN Unit 1 show the values obtained were within the acceptance criteria and ranged from 160.5 inch-lbs to 601.9 inch-lbs. As was discussed in Section 3.2.1, it was generally the performance of this surveillance that identified some level of ice build-up on one or more lower inlet doors. WBN Unit 1 has not experienced a failure of this surveillance other than the one described earlier that occurred in 1999. The industry information shows that the identification of ice build-up is associated with the performance of this surveillance. | |||
There were three cases where high torque values were identified that did not involve ice build-up on the lower inlet doors. One instance occurred at the Sequoyah Nuclear Plant in 1992. The lower inlet doors on both Sequoyah units were made inoperable because the concrete floor of the ice condenser had expanded upwards due to water intrusion in insulating material within the floor and the subsequent expansion due to freezing. This event caused a number of the lower inlet doors to experience binding. A very similar event occurred at one non-TVA ice condenser plant. The third event occurred at a non-TVA plant when door blocks that are installed during refueling outages to prevent inadvertent opening of the lower inlet doors were left in place. An initial test on the lower inlet doors at WBN Unit 2 performed in May 2015 was successful without issue. This test will be performed again prior to WBN Unit 2 initial entry into Mode 4. | There were three cases where high torque values were identified that did not involve ice build-up on the lower inlet doors. One instance occurred at the Sequoyah Nuclear Plant in 1992. The lower inlet doors on both Sequoyah units were made inoperable because the concrete floor of the ice condenser had expanded upwards due to water intrusion in insulating material within the floor and the subsequent expansion due to freezing. This event caused a number of the lower inlet doors to experience binding. A very similar event occurred at one non-TVA ice condenser plant. The third event occurred at a non-TVA plant when door blocks that are installed during refueling outages to prevent inadvertent opening of the lower inlet doors were left in place. An initial test on the lower inlet doors at WBN Unit 2 performed in May 2015 was successful without issue. This test will be performed again prior to WBN Unit 2 initial entry into Mode 4. | ||
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not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-8 currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extends beyond the currently planned end of cycle date. | not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-8 currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extends beyond the currently planned end of cycle date. | ||
Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public. | Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public. | ||
3.2.3 Surveillance Requirement 3.6.12.5 This SR verifies that the lower inlet doors have not developed excessive friction and that the return springs are producing a door return torque within required limits. To obtain these values, a measurement is taken for the opening and closing torque (door at 40 degrees open position) and a calculation performed using these values to arrive at the frictional value. | |||
Requirement 3.6.12.5 This SR verifies that the lower inlet doors have not developed excessive friction and that the return springs are producing a door return torque within required limits. To obtain these values, a measurement is taken for the opening and closing torque (door at 40 degrees open position) and a calculation performed using these values to arrive at the frictional value. | |||
Each of these values is verified against the acceptance criteria. This verification ensures that, in the event of a small break LOCA or Steam Line Break, the 24-door pairs open uniformly. Opening uniformly assures that during the initial blowdown phase, the steam and water mixture entering the lower compartment does not pass through only part of the ice condenser, depleting the ice in one bay or group of bays, while bypassing the ice in other bays. | Each of these values is verified against the acceptance criteria. This verification ensures that, in the event of a small break LOCA or Steam Line Break, the 24-door pairs open uniformly. Opening uniformly assures that during the initial blowdown phase, the steam and water mixture entering the lower compartment does not pass through only part of the ice condenser, depleting the ice in one bay or group of bays, while bypassing the ice in other bays. | ||
Since WBN Unit 1 was issued a license on November 9, 1995, this surveillance has been successfully performed numerous times. In one test that was performed in 1996, 15 of the lower inlet doors exhibited a higher torque value than the acceptance criteria. | Since WBN Unit 1 was issued a license on November 9, 1995, this surveillance has been successfully performed numerous times. In one test that was performed in 1996, 15 of the lower inlet doors exhibited a higher torque value than the acceptance criteria. | ||
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==4.0 REGULATORY EVALUATION== | ==4.0 REGULATORY EVALUATION== | ||
4.1 Applicable Regulatory Requirements and Criteria | |||
Regulatory Requirements and Criteria | |||
The proposed amendment to Surveillance Requir ement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 do not reduce or change Watts Bar Nuclear Plant Unit 2's level of compliance with the following applicable regulations and requirements: | The proposed amendment to Surveillance Requir ement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 do not reduce or change Watts Bar Nuclear Plant Unit 2's level of compliance with the following applicable regulations and requirements: | ||
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acceptably low levels. | acceptably low levels. | ||
* 10 CFR 50, Appendix A, GDC 50, "Containment design basis," specifies that the containment structure and the containment heat removal systems be designed, with sufficient margin, such that the pressure and temperature resulting from a loss of coolant accident can be accommodated without exceeding the design leakage rate. | * 10 CFR 50, Appendix A, GDC 50, "Containment design basis," specifies that the containment structure and the containment heat removal systems be designed, with sufficient margin, such that the pressure and temperature resulting from a loss of coolant accident can be accommodated without exceeding the design leakage rate. | ||
4.2 Precedent Watts Bar Nuclear Plant Unit 1 was granted a one time extension to the surveillance testing frequency for the lower inlet doors during the first year of operation in September 1996 [ADAMS Accession No. ML020780182]. In October 1984, the McGuire Nuclear Station was granted permanent extensions to the ice condenser surveillance frequencies [ADAMS Accession No. ML013180209]. | |||
Watts Bar Nuclear Plant Unit 1 was granted a one time extension to the surveillance testing frequency for the lower inlet doors during the first year of operation in September 1996 [ADAMS Accession No. ML020780182]. In October 1984, the McGuire Nuclear Station was granted permanent extensions to the ice condenser surveillance frequencies [ADAMS Accession No. ML013180209]. | |||
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-10 4.3 Significant Hazards Consideration The Tennessee Valley Authority (TVA) proposes to amend Facility Operating License No. NPF-96 for the Watts Bar Nuclear Plant (WBN) Unit 2 by requesting a change to Technical Specifications (TS) Surveillance R equirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 in the first cycle after receipt of the Operating License. This proposed amendment will modify the three SRs by deleting the frequency condition: | ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-10 4.3 Significant Hazards Consideration The Tennessee Valley Authority (TVA) proposes to amend Facility Operating License No. NPF-96 for the Watts Bar Nuclear Plant (WBN) Unit 2 by requesting a change to Technical Specifications (TS) Surveillance R equirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 in the first cycle after receipt of the Operating License. This proposed amendment will modify the three SRs by deleting the frequency condition: | ||
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Therefore, since there is no adverse impact of this amendment on the WBN Unit 2 safety analysis, there is no significant reduction in the margin of safety of the plant. | Therefore, since there is no adverse impact of this amendment on the WBN Unit 2 safety analysis, there is no significant reduction in the margin of safety of the plant. | ||
4.4 Conclusions Tennessee Valley Authority evaluated the proposed change to WBN Unit 2 TS SR 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 to perform the surveillance tests within 90 days of initial entry into MODE 4 and every 180 day thereafter, for the first operating cycle of operation for Watts Bar Nuclear Plant Unit 2. The evaluation determined that there is substantial operating experience associated with surveillance testing performed at the nine operating nuclear units in the United States with ice condenser containments that establishes that the lower inlet doors are highly reliable and have a very low failure frequency. The evaluation also determined that the observed failures to meet the surveillance requirements would not prevent the doors, much less the ice condenser as a whole, from performing its primary safety function of limiting the peak containment pressure and temperature after a design basis event. The evaluation establishes that the proposed amendment does not constitute a substantial safety hazard. The proposed amendment prevents an otherwise unnecessary shutdown of the WBN Unit 2. | |||
Tennessee Valley Authority evaluated the proposed change to WBN Unit 2 TS SR 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 to perform the surveillance tests within 90 days of initial entry into MODE 4 and every 180 day thereafter, for the first operating cycle of operation for Watts Bar Nuclear Plant Unit 2. The evaluation determined that there is substantial operating experience associated with surveillance testing performed at the nine operating nuclear units in the United States with ice condenser containments that establishes that the lower inlet doors are highly reliable and have a very low failure frequency. The evaluation also determined that the observed failures to meet the surveillance requirements would not prevent the doors, much less the ice condenser as a whole, from performing its primary safety function of limiting the peak containment pressure and temperature after a design basis event. The evaluation establishes that the proposed amendment does not constitute a substantial safety hazard. The proposed amendment prevents an otherwise unnecessary shutdown of the WBN Unit 2. | |||
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-12 | ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-12 | ||
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DESCRIPTION | DESCRIPTION | ||
2.0 DETAILED DESCRIPTION | |||
DESCRIPTION | |||
==3.0 TECHNICAL EVALUATION== | ==3.0 TECHNICAL EVALUATION== | ||
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DESCRIPTION Pursuant to Title 10 of the Code of Federal Regulations (CFR) §50.90, Tennessee Valley Authority (TVA) is submitting a request for an amendment to Facility Operating License No. NPF-96 for Watts Bar Nuclear Plant (WBN) Unit 2. The proposed amendment will modify Technical Specification (TS) 3.6.12, "Ice Condenser Doors," Surveillance Requirements (SRs) 3.6.12.3 through 3.6.12.5 for the ice condenser lower inlet doors during the first cycle after the receipt of the Operating License. | DESCRIPTION Pursuant to Title 10 of the Code of Federal Regulations (CFR) §50.90, Tennessee Valley Authority (TVA) is submitting a request for an amendment to Facility Operating License No. NPF-96 for Watts Bar Nuclear Plant (WBN) Unit 2. The proposed amendment will modify Technical Specification (TS) 3.6.12, "Ice Condenser Doors," Surveillance Requirements (SRs) 3.6.12.3 through 3.6.12.5 for the ice condenser lower inlet doors during the first cycle after the receipt of the Operating License. | ||
The proposed amendment is required to allow continued operation of WBN Unit 2 during the summer of 2016 and preclude a shutdown of the unit. | The proposed amendment is required to allow continued operation of WBN Unit 2 during the summer of 2016 and preclude a shutdown of the unit. | ||
2.0 DETAILED DESCRIPTION Proposed Amendment Surveillance Requirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 have a performance frequency of 18 months except for the first year of operation. In the first year of plant operation, these surveillances are to be performed every three months. TVA is proposing to perform the surveillance within 90 days of entering MODE 4 for the first time and then 180 days thereafter for the first operating cycle. The proposed revision to the SRs was discussed in a November 19, 2015 public meeting between the Nuclear Regulatory Commission and TVA. | |||
DESCRIPTION Proposed Amendment Surveillance Requirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 have a performance frequency of 18 months except for the first year of operation. In the first year of plant operation, these surveillances are to be performed every three months. TVA is proposing to perform the surveillance within 90 days of entering MODE 4 for the first time and then 180 days thereafter for the first operating cycle. The proposed revision to the SRs was discussed in a November 19, 2015 public meeting between the Nuclear Regulatory Commission and TVA. | |||
==3.0 TECHNICAL EVALUATION== | ==3.0 TECHNICAL EVALUATION== | ||
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The frequent surveillance testing intervals initially required were reasonable given that there was no operating experience, testing done at Westinghouse Electric Corporation Waltz Mill Facility could not replicate containment environmental conditions with respect to lower inlet door performance during normal operation, and the safety importance of the ice condenser in assuring containment integrity in the event of a Loss of Coolant Accident (LOCA) or other DBA. The current surveillance frequency, typically 18 months, is supported by many years of ice condenser operating experience with few failures of the doors to meet the acceptance criteria. None of the failures that have occurred were found to be safety significant. | The frequent surveillance testing intervals initially required were reasonable given that there was no operating experience, testing done at Westinghouse Electric Corporation Waltz Mill Facility could not replicate containment environmental conditions with respect to lower inlet door performance during normal operation, and the safety importance of the ice condenser in assuring containment integrity in the event of a Loss of Coolant Accident (LOCA) or other DBA. The current surveillance frequency, typically 18 months, is supported by many years of ice condenser operating experience with few failures of the doors to meet the acceptance criteria. None of the failures that have occurred were found to be safety significant. | ||
The following discussion provides the basis for revising the surveillance frequency for each of the SRs. | The following discussion provides the basis for revising the surveillance frequency for each of the SRs. | ||
3.2.1 Surveillance Requirement 3.6.12.3 | |||
Requirement 3.6.12.3 | |||
This SR requires inspection of the ice condenser lower inlet doors to identify ice, frost or debris which may restrict their opening in a design basis event. Data from WBN Unit 1 performances of the SR going back to issuance of the Low Power License in November 1995, indicates that ice, frost or debris have not been a problem. There was one instance identified in February 1999 where frost build-up was sufficient to increase the opening torque for some doors beyond the value allowed in SR 3.6.12.4. | This SR requires inspection of the ice condenser lower inlet doors to identify ice, frost or debris which may restrict their opening in a design basis event. Data from WBN Unit 1 performances of the SR going back to issuance of the Low Power License in November 1995, indicates that ice, frost or debris have not been a problem. There was one instance identified in February 1999 where frost build-up was sufficient to increase the opening torque for some doors beyond the value allowed in SR 3.6.12.4. | ||
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not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extend beyond the currently planned end of cycle date. | not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extend beyond the currently planned end of cycle date. | ||
Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public. | Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public. | ||
3.2.2 Surveillance Requirement 3.6.12.4 This SR requires verification that the torque required to open the lower inlet doors is less than or equal to 675 inch-lbs. This verification provides assurance that no doors become stuck in the closed position during a design basis event such as a large break LOCA. Testing of the doors on WBN Unit 1 show the values obtained were within the acceptance criteria and ranged from 160.5 inch-lbs to 601.9 inch-lbs. As was discussed in Section 3.2.1, it was generally the performance of this surveillance that identified some level of ice build-up on one or more lower inlet doors. WBN Unit 1 has not experienced a failure of this surveillance other than the one described earlier that occurred in 1999. The industry information shows that the identification of ice build-up is associated with the performance of this surveillance. | |||
Requirement 3.6.12.4 This SR requires verification that the torque required to open the lower inlet doors is less than or equal to 675 inch-lbs. This verification provides assurance that no doors become stuck in the closed position during a design basis event such as a large break LOCA. Testing of the doors on WBN Unit 1 show the values obtained were within the acceptance criteria and ranged from 160.5 inch-lbs to 601.9 inch-lbs. As was discussed in Section 3.2.1, it was generally the performance of this surveillance that identified some level of ice build-up on one or more lower inlet doors. WBN Unit 1 has not experienced a failure of this surveillance other than the one described earlier that occurred in 1999. The industry information shows that the identification of ice build-up is associated with the performance of this surveillance. | |||
There were three cases where high torque values were identified that did not involve ice build-up on the lower inlet doors. One instance occurred at the Sequoyah Nuclear Plant in 1992. The lower inlet doors on both Sequoyah units were made inoperable because the concrete floor of the ice condenser had expanded upwards due to water intrusion in insulating material within the floor and the subsequent expansion due to freezing. This event caused a number of the lower inlet doors to experience binding. A very similar event occurred at one non-TVA ice condenser plant. The third event occurred at a non-TVA plant when door blocks that are installed during refueling outages to prevent inadvertent opening of the lower inlet doors were left in place. An initial test on the lower inlet doors at WBN Unit 2 performed in May 2015 was successful without issue. This test will be performed again prior to WBN Unit 2 initial entry into Mode 4. | There were three cases where high torque values were identified that did not involve ice build-up on the lower inlet doors. One instance occurred at the Sequoyah Nuclear Plant in 1992. The lower inlet doors on both Sequoyah units were made inoperable because the concrete floor of the ice condenser had expanded upwards due to water intrusion in insulating material within the floor and the subsequent expansion due to freezing. This event caused a number of the lower inlet doors to experience binding. A very similar event occurred at one non-TVA ice condenser plant. The third event occurred at a non-TVA plant when door blocks that are installed during refueling outages to prevent inadvertent opening of the lower inlet doors were left in place. An initial test on the lower inlet doors at WBN Unit 2 performed in May 2015 was successful without issue. This test will be performed again prior to WBN Unit 2 initial entry into Mode 4. | ||
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not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-8 currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extends beyond the currently planned end of cycle date. | not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-8 currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extends beyond the currently planned end of cycle date. | ||
Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public. | Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public. | ||
3.2.3 Surveillance Requirement 3.6.12.5 This SR verifies that the lower inlet doors have not developed excessive friction and that the return springs are producing a door return torque within required limits. To obtain these values, a measurement is taken for the opening and closing torque (door at 40 degrees open position) and a calculation performed using these values to arrive at the frictional value. | |||
Requirement 3.6.12.5 This SR verifies that the lower inlet doors have not developed excessive friction and that the return springs are producing a door return torque within required limits. To obtain these values, a measurement is taken for the opening and closing torque (door at 40 degrees open position) and a calculation performed using these values to arrive at the frictional value. | |||
Each of these values is verified against the acceptance criteria. This verification ensures that, in the event of a small break LOCA or Steam Line Break, the 24-door pairs open uniformly. Opening uniformly assures that during the initial blowdown phase, the steam and water mixture entering the lower compartment does not pass through only part of the ice condenser, depleting the ice in one bay or group of bays, while bypassing the ice in other bays. | Each of these values is verified against the acceptance criteria. This verification ensures that, in the event of a small break LOCA or Steam Line Break, the 24-door pairs open uniformly. Opening uniformly assures that during the initial blowdown phase, the steam and water mixture entering the lower compartment does not pass through only part of the ice condenser, depleting the ice in one bay or group of bays, while bypassing the ice in other bays. | ||
Since WBN Unit 1 was issued a license on November 9, 1995, this surveillance has been successfully performed numerous times. In one test that was performed in 1996, 15 of the lower inlet doors exhibited a higher torque value than the acceptance criteria. | Since WBN Unit 1 was issued a license on November 9, 1995, this surveillance has been successfully performed numerous times. In one test that was performed in 1996, 15 of the lower inlet doors exhibited a higher torque value than the acceptance criteria. | ||
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==4.0 REGULATORY EVALUATION== | ==4.0 REGULATORY EVALUATION== | ||
4.1 Applicable Regulatory Requirements and Criteria | |||
Regulatory Requirements and Criteria | |||
The proposed amendment to Surveillance Requir ement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 do not reduce or change Watts Bar Nuclear Plant Unit 2's level of compliance with the following applicable regulations and requirements: | The proposed amendment to Surveillance Requir ement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 do not reduce or change Watts Bar Nuclear Plant Unit 2's level of compliance with the following applicable regulations and requirements: | ||
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acceptably low levels. | acceptably low levels. | ||
* 10 CFR 50, Appendix A, GDC 50, "Containment design basis," specifies that the containment structure and the containment heat removal systems be designed, with sufficient margin, such that the pressure and temperature resulting from a loss of coolant accident can be accommodated without exceeding the design leakage rate. | * 10 CFR 50, Appendix A, GDC 50, "Containment design basis," specifies that the containment structure and the containment heat removal systems be designed, with sufficient margin, such that the pressure and temperature resulting from a loss of coolant accident can be accommodated without exceeding the design leakage rate. | ||
4.2 Precedent Watts Bar Nuclear Plant Unit 1 was granted a one time extension to the surveillance testing frequency for the lower inlet doors during the first year of operation in September 1996 [ADAMS Accession No. ML020780182]. In October 1984, the McGuire Nuclear Station was granted permanent extensions to the ice condenser surveillance frequencies [ADAMS Accession No. ML013180209]. | |||
Watts Bar Nuclear Plant Unit 1 was granted a one time extension to the surveillance testing frequency for the lower inlet doors during the first year of operation in September 1996 [ADAMS Accession No. ML020780182]. In October 1984, the McGuire Nuclear Station was granted permanent extensions to the ice condenser surveillance frequencies [ADAMS Accession No. ML013180209]. | |||
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-10 4.3 Significant Hazards Consideration The Tennessee Valley Authority (TVA) proposes to amend Facility Operating License No. NPF-96 for the Watts Bar Nuclear Plant (WBN) Unit 2 by requesting a change to Technical Specifications (TS) Surveillance R equirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 in the first cycle after receipt of the Operating License. This proposed amendment will modify the three SRs by deleting the frequency condition: | ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-10 4.3 Significant Hazards Consideration The Tennessee Valley Authority (TVA) proposes to amend Facility Operating License No. NPF-96 for the Watts Bar Nuclear Plant (WBN) Unit 2 by requesting a change to Technical Specifications (TS) Surveillance R equirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 in the first cycle after receipt of the Operating License. This proposed amendment will modify the three SRs by deleting the frequency condition: | ||
Line 376: | Line 348: | ||
Therefore, since there is no adverse impact of this amendment on the WBN Unit 2 safety analysis, there is no significant reduction in the margin of safety of the plant. | Therefore, since there is no adverse impact of this amendment on the WBN Unit 2 safety analysis, there is no significant reduction in the margin of safety of the plant. | ||
4.4 Conclusions Tennessee Valley Authority evaluated the proposed change to WBN Unit 2 TS SR 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 to perform the surveillance tests within 90 days of initial entry into MODE 4 and every 180 day thereafter, for the first operating cycle of operation for Watts Bar Nuclear Plant Unit 2. The evaluation determined that there is substantial operating experience associated with surveillance testing performed at the nine operating nuclear units in the United States with ice condenser containments that establishes that the lower inlet doors are highly reliable and have a very low failure frequency. The evaluation also determined that the observed failures to meet the surveillance requirements would not prevent the doors, much less the ice condenser as a whole, from performing its primary safety function of limiting the peak containment pressure and temperature after a design basis event. The evaluation establishes that the proposed amendment does not constitute a substantial safety hazard. The proposed amendment prevents an otherwise unnecessary shutdown of the WBN Unit 2. | |||
Tennessee Valley Authority evaluated the proposed change to WBN Unit 2 TS SR 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 to perform the surveillance tests within 90 days of initial entry into MODE 4 and every 180 day thereafter, for the first operating cycle of operation for Watts Bar Nuclear Plant Unit 2. The evaluation determined that there is substantial operating experience associated with surveillance testing performed at the nine operating nuclear units in the United States with ice condenser containments that establishes that the lower inlet doors are highly reliable and have a very low failure frequency. The evaluation also determined that the observed failures to meet the surveillance requirements would not prevent the doors, much less the ice condenser as a whole, from performing its primary safety function of limiting the peak containment pressure and temperature after a design basis event. The evaluation establishes that the proposed amendment does not constitute a substantial safety hazard. The proposed amendment prevents an otherwise unnecessary shutdown of the WBN Unit 2. | |||
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-12 | ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-12 |
Revision as of 07:13, 7 May 2019
ML15350A250 | |
Person / Time | |
---|---|
Site: | Watts Bar ![]() |
Issue date: | 12/15/2015 |
From: | Shea J W Tennessee Valley Authority |
To: | Document Control Desk, Office of Nuclear Reactor Regulation |
References | |
CNL-15-225, TS-WBN2-15-19 | |
Download: ML15350A250 (22) | |
Text
Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402
CNL-15-225
December 15, 2015 10 CFR 50.90 U.S. Nuclear Regulatory Commission
ATTN: Document Control Desk Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391
Subject:
Watts Bar Nuclear Plant Unit 2 - Application to Revise Technical Specifications for Ice Condenser Door Surveillances (TS-WBN2-15-19)
In accordance with the provisions of Title 10 of the Code of Federal Regulations (CFR) §50.90, "Application for amendment of license, construction permit, or early site permit," Tennessee Valley Authority (TVA) is submitting a request for an amendment to Facility Operating License No. NPF-96 for the Watts Bar Nuclear Plant (WBN) Unit 2. The proposed amendment would revise Technical Specifications (TS) 3.6.12, "Ice Condenser Doors," Surveillance Requirements (SRs) for the WBN U2 ice condenser lower inlet doors. The proposed amendment will revise the surveillance frequency of three SRs that perform visual inspection and torque testing on the ice condenser lower inlet doors during the first cycle after receipt of the Operating License. The proposed amendment is required to preclude a plant shutdown for the purpose of performing lower inlet door surveillance testing.
The enclosure provides a description and technical evaluation of the proposed amendment, a regulatory evaluation, and a discussion of environmental considerations. Attachment 1 to the enclosure provides marked-up copies of SRs 3.6.12.3 through 3.6.12.5, to identify the proposed changes. Attachment 2 to the enclosure provides clean-typed copies of SRs 3.6.12.3 through 3.6.12.5 with the proposed changes incorporated.
TVA requests approval of the proposed License Amendment by February 19, 2016 to
support summer operation of WBN Unit 2. The License Amendment will be implemented within 30 days of approval.
U.S. Nuclear Regulatory Commission CNL-15-225 Page 2 December15 , 2015 TVA has determined that there are no significant hazards considerations associated with the proposed amendment and that the amendment qualifies for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c)(9). The WBN Plant Operations Review Committee and the TVA Nuclear Safety Review Board have reviewed this proposed amendment and determined that operation of WBN Unit 2 in accordance with the proposed amendment will not endanger the health and safety of the public. Additionally , in accordance with 10 CFR 50.91 (b)(1 ), TVA is sending a copy of this letter and the enclosure to the Tennessee Department of Environment and Conservation. There are no new regulatory commitments contained in this letter. Please address any questions regarding this request to Gordon Arent at 423-365-2004. I declare under penalty of perjury that the foregoing is true and correct. Executed on the 15 1 h day of December , 2015. 7 Respe/f lly , L 6'L-. hea President , Nuclear Licensing
Enclosure:
Evaluation of Proposed Amendment cc (Enclosure): U.S. Nuclear Regulatory Commiss i on , Region II NRC Senior Resident Insp e cto r, Watts Bar Nuclea r P l ant NRC Project Manager -Watts Bar Nuclear Plant Director -Division of Radiological Health -Tennessee State Department of Environment and Conservat i on ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-1
Subject:
Application to Revise Technical Specification for Ice Condenser Lower Inlet Door Surveillances (TS-WBN2-15-19) 1.0
SUMMARY
DESCRIPTION
2.0 DETAILED DESCRIPTION
3.0 TECHNICAL EVALUATION
4.0 REGULATORY EVALUATION
5.0 ENVIRONMENTAL CONSIDERATION
ATTACHMENTS
- WBN Unit 2 TS 3.6.12 Ice Condenser Doors Marked-up Pages to Show Changes
- WBN Unit 2 TS 3.6.12 Ice Condenser Doors Clean Typed Pages with Changes Incorporated
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-2 1.0
SUMMARY
DESCRIPTION Pursuant to Title 10 of the Code of Federal Regulations (CFR) §50.90, Tennessee Valley Authority (TVA) is submitting a request for an amendment to Facility Operating License No. NPF-96 for Watts Bar Nuclear Plant (WBN) Unit 2. The proposed amendment will modify Technical Specification (TS) 3.6.12, "Ice Condenser Doors," Surveillance Requirements (SRs) 3.6.12.3 through 3.6.12.5 for the ice condenser lower inlet doors during the first cycle after the receipt of the Operating License.
The proposed amendment is required to allow continued operation of WBN Unit 2 during the summer of 2016 and preclude a shutdown of the unit.
2.0 DETAILED DESCRIPTION Proposed Amendment Surveillance Requirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 have a performance frequency of 18 months except for the first year of operation. In the first year of plant operation, these surveillances are to be performed every three months. TVA is proposing to perform the surveillance within 90 days of entering MODE 4 for the first time and then 180 days thereafter for the first operating cycle. The proposed revision to the SRs was discussed in a November 19, 2015 public meeting between the Nuclear Regulatory Commission and TVA.
3.0 TECHNICAL EVALUATION
3.1 Ice Condenser System Description
The ice condenser is a large passive heat sink to absorb energy from a high energy line break within the primary containment to limit the peak containment pressure and temperature after a Design Basis Accident (DBA). The ice condenser is an annular compartment enclosing approximately 300 degrees of the perimeter of the upper containment compartment. It also penetrates the operating deck so that a portion of the ice condenser extends into the lower containment compartment (Figures 1 and 2). The lower portion of the ice condenser has a series of vertically hinged lower inlet doors exposed to the atmosphere of the lower containment compartment, which, for normal plant operation, are designed to remain closed. At the top of the ice condenser is another set of doors exposed to the atmosphere of the upper compartment, which also remain closed during normal plant operation. Intermediate deck doors, located below the top deck doors, form the floor of a plenum at the upper part of the ice condenser.
These doors also remain closed during normal plant operation. The upper plenum area is used to facilitate surveillance and maintenance of the ice bed.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-3 ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-4 ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-5 The ice bed area consists of the total volume from the floor of the ice condenser to the intermediate deck doors. There are 1944 ice baskets that are located within the ice bed containing approximately 2,750,700 pounds of ice. The ice baskets are designed and positioned within the ice bed in an arrangement to promote heat transfer from steam to ice. This arrangement enhances the ice condenser's primary function of condensing steam and absorbing heat energy released to the containment during a DBA. This limits the containment pressure and temperature response to a DBA and also reduces the release of fission product radioactivity from containment to the environment in the event of a DBA.
In the event of a DBA, the ice condenser lower inlet doors (located below the operating deck) open due to the pressure rise in the lower compartment. This allows air and steam to flow from the lower compartment into the ice condenser. The resulting pressure increase within the ice condenser causes the intermediate deck doors and the top deck doors to open, which allows the air to flow out of the ice condenser into the upper compartment. Steam condensation within the ice condenser limits the pressure and temperature buildup in containment. A divider barrier separates the upper and lower compartments and ensures that the steam is directed into the ice condenser.
The ice is adequate to absorb the initial blowdown energy from steam and water released during a DBA and the additional heat loads that would enter containment early in the event following the initial blowdown. The additional heat loads would come from the residual heat in the reactor core, the hot piping and components, and the secondary system, including the steam generators. As the ice bed melts out, the containment spray system becomes the primary means of energy removal from the containment atmosphere. During the post blowdown period, the Air Return System (ARS) returns upper compartment air through the divider barrier to the lower compartment. This serves to equalize pressures in containment and to continue circulating heated air and steam from the lower compartment thr ough the ice condenser where the heat is removed by the remaining ice.
It is important for the ice to be uniformly distributed around the 24 ice condenser bays and for open flow paths to exist around the ice baskets. This is especially important during the initial blowdown so that the steam and water mixture entering the lower compartment does not pass through only part of the ice condenser, depleting the ice there while bypassing the ice in other bays.
The ice condenser doors ensure that the ice stored in the ice bed is preserved during normal operation (doors closed) and that the ice condenser functions as designed if called upon to act as a passive heat sink following a DBA.
Surveillance Requirement 3.6.12.3, SR 3.6.12.4 and SR 3.6.12.5, require entry into the lower compartment of the primary containment at WBN Unit 2. This is a high radiation area when the plant is in operation and permanent access to the lower inlet doors is not available. These three surveillances may only be performed when the unit is in Mode 3 or lower. Thus, performance of one or more of these surveillance in the first year will require an otherwise unscheduled shutdown of WBN Unit 2.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-6 3.2 Basis for Proposed License Amendment The requirements of SRs 3.6.12.3, 3.6.12.4, and 3.6.12.5 provide inspections and tests to ensure the operability of the ice condenser lower inlet doors. Specifically, SR 3.6.12.3 requires inspections of the doors to identify ice, frost, or debris which may restrict their opening in a design basis event. SRs 3.6.12.4 and 3.6.12.5 require torque tests for opening and modulating to ensure proper door function.
The SRs for operability of the ice condenser lower inlet doors are essentially the same for all ten ice condenser units in the United States. The requirement to check operability of the doors every 3 months for the first year of operation was a common feature of the TS for the ice condenser plants. The subsequent surveillance frequency was every six months and the frequency for each of these SRs was then extended to the current value of 18 months as operating experience was gained.
The frequent surveillance testing intervals initially required were reasonable given that there was no operating experience, testing done at Westinghouse Electric Corporation Waltz Mill Facility could not replicate containment environmental conditions with respect to lower inlet door performance during normal operation, and the safety importance of the ice condenser in assuring containment integrity in the event of a Loss of Coolant Accident (LOCA) or other DBA. The current surveillance frequency, typically 18 months, is supported by many years of ice condenser operating experience with few failures of the doors to meet the acceptance criteria. None of the failures that have occurred were found to be safety significant.
The following discussion provides the basis for revising the surveillance frequency for each of the SRs.
3.2.1 Surveillance Requirement 3.6.12.3
This SR requires inspection of the ice condenser lower inlet doors to identify ice, frost or debris which may restrict their opening in a design basis event. Data from WBN Unit 1 performances of the SR going back to issuance of the Low Power License in November 1995, indicates that ice, frost or debris have not been a problem. There was one instance identified in February 1999 where frost build-up was sufficient to increase the opening torque for some doors beyond the value allowed in SR 3.6.12.4.
The cause of the ice build-up was a known steam leak in a steam generator man-way cover. Based on the WBN Unit 1 performances of this test since fuel load, it is expected that inspection results for WBN Unit 2 at the proposed frequency would show highly reliable performance of the ice condenser lower inlet doors. A review of licensee event reports from the other ice condenser plants was conducted. The information showed that the WBN Unit 1 experience was typical. An initial test on the lower inlet doors at WBN Unit 2 performed in May 2015 was successful without issue. This test will be performed again prior to WBN Unit 2 initial entry into Mode 4. The lower inlet doors are very reliable and are not prone to ice buildup or blockage. If an issue was found with the doors, it was determined not to be safety significant.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-7 This is normally an 18-month surveillance as supported by the operational data, thus, performing the surveillance at least twice in the first cycle of WBN Unit 2 operation would
not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extend beyond the currently planned end of cycle date.
Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public.
3.2.2 Surveillance Requirement 3.6.12.4 This SR requires verification that the torque required to open the lower inlet doors is less than or equal to 675 inch-lbs. This verification provides assurance that no doors become stuck in the closed position during a design basis event such as a large break LOCA. Testing of the doors on WBN Unit 1 show the values obtained were within the acceptance criteria and ranged from 160.5 inch-lbs to 601.9 inch-lbs. As was discussed in Section 3.2.1, it was generally the performance of this surveillance that identified some level of ice build-up on one or more lower inlet doors. WBN Unit 1 has not experienced a failure of this surveillance other than the one described earlier that occurred in 1999. The industry information shows that the identification of ice build-up is associated with the performance of this surveillance.
There were three cases where high torque values were identified that did not involve ice build-up on the lower inlet doors. One instance occurred at the Sequoyah Nuclear Plant in 1992. The lower inlet doors on both Sequoyah units were made inoperable because the concrete floor of the ice condenser had expanded upwards due to water intrusion in insulating material within the floor and the subsequent expansion due to freezing. This event caused a number of the lower inlet doors to experience binding. A very similar event occurred at one non-TVA ice condenser plant. The third event occurred at a non-TVA plant when door blocks that are installed during refueling outages to prevent inadvertent opening of the lower inlet doors were left in place. An initial test on the lower inlet doors at WBN Unit 2 performed in May 2015 was successful without issue. This test will be performed again prior to WBN Unit 2 initial entry into Mode 4.
This is normally an 18-month surveillance as supported by the operational data, thus, performing the surveillance at least twice in the first cycle of WBN Unit 2 operation would
not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-8 currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extends beyond the currently planned end of cycle date.
Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public.
3.2.3 Surveillance Requirement 3.6.12.5 This SR verifies that the lower inlet doors have not developed excessive friction and that the return springs are producing a door return torque within required limits. To obtain these values, a measurement is taken for the opening and closing torque (door at 40 degrees open position) and a calculation performed using these values to arrive at the frictional value.
Each of these values is verified against the acceptance criteria. This verification ensures that, in the event of a small break LOCA or Steam Line Break, the 24-door pairs open uniformly. Opening uniformly assures that during the initial blowdown phase, the steam and water mixture entering the lower compartment does not pass through only part of the ice condenser, depleting the ice in one bay or group of bays, while bypassing the ice in other bays.
Since WBN Unit 1 was issued a license on November 9, 1995, this surveillance has been successfully performed numerous times. In one test that was performed in 1996, 15 of the lower inlet doors exhibited a higher torque value than the acceptance criteria.
Two doors had torque values that were moderately higher than the acceptance criteria (23 and 13 percent respectively). The remaining thirteen doors had torque values that were 2.8 percent or 9.5 inch-lbs higher than the acceptance criteria. The doors were exercised in place and the tests were performed again successfully. The doors still modulated back towards the closed position. A review of industry data shows few failures of this surveillance criteria. Thus, as was the case for SR 3.6.12.3 and SR 3.6.12.4, the lower inlet doors are highly reliable. An initial test on the lower inlet doors at WBN Unit 2 performed in May 2015 was successful without issue. This test will be performed again prior to WBN Unit 2 initial entry into Mode 4.
This is normally an 18-month surveillance as supported by the operational data, thus, performing the surveillance at least twice in the first cycle of WBN Unit 2 operation would
not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extends beyond the currently planned end of cycle date.
Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-9
4.0 REGULATORY EVALUATION
4.1 Applicable Regulatory Requirements and Criteria
The proposed amendment to Surveillance Requir ement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 do not reduce or change Watts Bar Nuclear Plant Unit 2's level of compliance with the following applicable regulations and requirements:
- 10 CFR 20, "Standards For Protection Against Radiation," provides guidance and criteria for assuring, among other requirements, that occupational dose rates are kept as low as reasonably achievable.
- 10 CFR 50, Appendix A, GDC 16, "Containment design," specifies that the containment is an essentially leak-tight barrier to prevent the uncontrolled release of radioactivity to the environment and that containment design conditions important to safety are maintained.
- 10 CFR 50, Appendix A, GDC 38, "Containment heat removal," specifies that the containment pressure and temperature are rapidly reduced consistent with the functioning of other associated systems following a LOCA and maintains them at
acceptably low levels.
- 10 CFR 50, Appendix A, GDC 50, "Containment design basis," specifies that the containment structure and the containment heat removal systems be designed, with sufficient margin, such that the pressure and temperature resulting from a loss of coolant accident can be accommodated without exceeding the design leakage rate.
4.2 Precedent Watts Bar Nuclear Plant Unit 1 was granted a one time extension to the surveillance testing frequency for the lower inlet doors during the first year of operation in September 1996 [ADAMS Accession No. ML020780182]. In October 1984, the McGuire Nuclear Station was granted permanent extensions to the ice condenser surveillance frequencies [ADAMS Accession No. ML013180209].
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-10 4.3 Significant Hazards Consideration The Tennessee Valley Authority (TVA) proposes to amend Facility Operating License No. NPF-96 for the Watts Bar Nuclear Plant (WBN) Unit 2 by requesting a change to Technical Specifications (TS) Surveillance R equirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 in the first cycle after receipt of the Operating License. This proposed amendment will modify the three SRs by deleting the frequency condition:
3 month during the first year after receipt of license
And adding the following condition:
Once with 90 days of initial entry into MODE 4 and 180 days thereafter, for the first operating cycle.
TVA has concluded that the amendment to WBN Unit 2 TS 3.6.12 does not involve a significant hazards consideration. TVA's conclusion is based on its evaluation in accordance with 10 CFR 50.91(a)(1) of the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below:
- 1. Does the proposed amendment involve a significant increase in the probability or consequence of an accident previously evaluated?
Response: No.
The ice condenser is a passive heat removal plant feature. The proposed amendment to the TS 3.6.12 does not change the design, physical features or the function of the ice condenser or the ice condenser doors. The ice condenser is not an accident initiator, thus the proposed amendment does not increase the probability of an accident previously evaluated.
The ice condenser is credited in mitigating the consequences of postulated Design Basis Accidents (DBAs) and remains capable of performing its design basis functions. The proposed amendment to the SRs during the first cycle of WBN Unit 2 operation does not change the ice condenser configuration or how it behaves in the event of a DBA. Thus it is concluded that a significant increase in the consequences of an accident previously evaluated will not occur as a result of the proposed amendment.
Therefore, the proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-11 2. Does the proposed amendment create the possibility of a new or different kind of accident from any accident previously evaluated?
Response: No. The proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated. The proposed amendment does not introduce any new modes of plant operation, change the design function of the ice condenser or any other Structure System or Component (SSC), or change the mode of operation of the ice condenser or any other SSC. There are no new equipment failure modes or malfunctions created as the ice condenser and ice condenser lower inlet doors continue to operate in the same manner assumed in the accident analysis. The ice condenser is a passive post-accident heat removal feature that is not an accident initiator.
Therefore, the proposed amendment does not creat e the possibility of a new or different kind of accident from any previously evaluated.
- 3. Does the proposed amendment involve a significant reduction in a margin of safety?
Response: No. Ice condensers have been in-service at nine nuclear units in the United States for many years. Operating experience has shown that an 18-month surveillance frequency for evaluating operability is appropriate for the lower inlet doors. The proposed amendment to perform a revised schedule of lower inlet door surveillances in the first cycle before transitioning to the standard 18-month surveillance frequency does not result in a significant reduction in the margin of safety.
Therefore, since there is no adverse impact of this amendment on the WBN Unit 2 safety analysis, there is no significant reduction in the margin of safety of the plant.
4.4 Conclusions Tennessee Valley Authority evaluated the proposed change to WBN Unit 2 TS SR 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 to perform the surveillance tests within 90 days of initial entry into MODE 4 and every 180 day thereafter, for the first operating cycle of operation for Watts Bar Nuclear Plant Unit 2. The evaluation determined that there is substantial operating experience associated with surveillance testing performed at the nine operating nuclear units in the United States with ice condenser containments that establishes that the lower inlet doors are highly reliable and have a very low failure frequency. The evaluation also determined that the observed failures to meet the surveillance requirements would not prevent the doors, much less the ice condenser as a whole, from performing its primary safety function of limiting the peak containment pressure and temperature after a design basis event. The evaluation establishes that the proposed amendment does not constitute a substantial safety hazard. The proposed amendment prevents an otherwise unnecessary shutdown of the WBN Unit 2.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-12
5.0 ENVIRONMENTAL CONSIDERATION
The proposed amendment revises the surveillance frequency for three SRs associated with TS 3.6.12 for the ice condenser lower inlet doors to perform the surveillance tests within 90 days of initial entry into MODE 4 and every 180 day thereafter, for the first operating cycle of operation for Watts Bar Nuclear Plant Unit 2. The proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-13 ATTACHMENTS Attachment 1 - WBN Unit 2 TS 3.6.12 Ice Condenser Doors Marked-up Pages to Show Changes - WBN Unit 2 TS 3.6.12 Ice Condenser Doors Clean Typed Pages with Changes Incorporated
ENCLOSURE ATTACHMENT 1
WBN Unit 2 TS 3.6.12 Ice Condenser Doors Marked-up Pages to Show Changes
Ice Condenser Doors 3.6.12 Watts Bar - Unit 2 3.6-29 ACTIONS (continued) CONDITION REQUIRED ACTION COMPLETION TIME A. Required Action and associated Completion Time of Condition A or C not met. D.1 Be in MODE 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> AND D.2 Be in MODE 5. 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />
SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.6.12.1 Verify all inlet doors indicate closed by the Inlet Door Position Monitoring System.
12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> SR 3.6.12.2 Verify, by visual inspection, each intermediate deck door is closed and not impaired by ice, frost, or debris. 7 days SR 3.6.12.3 Verify, by visual inspection, each inlet door is not impaired by ice, frost, or debris.
3 months during first year after receipt of license Once within 90 days of initial entry into MODE 4 and 180
days thereafter, for the first operating cycle. AND 18 months Ice Condenser Doors 3.6.12 Watts Bar - Unit 2 3.6-30 SR 3.6.12.4 Verify torque required to cause each inlet door to begin to open is 675 in-lb.
3 months during first year after receipt of license Once within 90 days of initial entry into MODE 4 and 180
days thereafter, for the first operating cycle. AND 18 months SR 3.6.12.5 Perform a torque test on a sampling of 50% of the inlet doors.
3 months during first year after receipt of license Once within 90 days of initial entry into MODE 4 and 180
days thereafter, for the first operating cycle. AND 18 months (continued)
Ice Condenser Doors 3.6.12 Watts Bar - Unit 2 3.6-31 SURVEILLANCE REQUIREMENTS (continued) SURVEILLANCE FREQUENCY SR 3.6.12.6 Verify for each intermediate deck door: a. No visual evidence of structural deterioration; b. Free movement of the vent assemblies; and c. Free movement of the door.
3 months during first year after receipt of license AND 18 months SR 3.6.12.7 Verify, by visual inspection, each top deck door: a. Is in place;
- b. Free movement of top deck vent assembly; and
- c. Has no condensation, frost, or ice formed on the door that would restrict its opening.
92 days Enclosure Attachment 2
WBN Unit 2 TS 3.6.12 Ice Condenser Doors Clean Typed Pages with Changes Incorporated
Ice Condenser Doors 3.6.12 Watts Bar - Unit 2 3.6-29 ACTIONS (continued) CONDITION REQUIRED ACTION COMPLETION TIME B. Required Action and associated Completion Time of Condition A or C
not met. D.1 Be in MODE 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> AND D.2 Be in MODE 5. 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />
SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.6.12.1 Verify all inlet doors indicate closed by the Inlet Door Position Monitoring System.
12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> SR 3.6.12.2 Verify, by visual inspection, each intermediate deck door is closed and not impaired by ice, frost, or debris. 7 days SR 3.6.12.3 Verify, by visual inspection, each inlet door is not impaired by ice, frost, or debris.
Once within 90 days of initial entry into MODE 4 and 180 days thereafter, for the first operating cycle.
AND 18 months Ice Condenser Doors 3.6.12 Watts Bar - Unit 2 3.6-30 SR 3.6.12.4 Verify torque required to cause each inlet door to begin to open is 675 in-lb.
Once within 90 days of initial entry into MODE 4 and 180
days thereafter, for the first operating cycle.
AND 18 months SR 3.6.12.5 Perform a torque test on a sampling of 50% of the inlet doors.
Once within 90 days of initial entry into MODE 4 and 180
days thereafter, for the first operating cycle.
AND 18 months SR 3.6.12.6 Verify for each intermediate deck door: d. No visual evidence of structural deterioration;
- e. Free movement of the vent assemblies; and
- f. Free movement of the door.
3 months during first year after receipt of license AND 18 months SR 3.6.12.7 Verify, by visual inspection, each top deck door: d. Is in place;
- e. Free movement of top deck vent assembly; and f. Has no condensation, frost, or ice formed on the door that would restrict its opening.
92 days Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402
CNL-15-225
December 15, 2015 10 CFR 50.90 U.S. Nuclear Regulatory Commission
ATTN: Document Control Desk Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391
Subject:
Watts Bar Nuclear Plant Unit 2 - Application to Revise Technical Specifications for Ice Condenser Door Surveillances (TS-WBN2-15-19)
In accordance with the provisions of Title 10 of the Code of Federal Regulations (CFR) §50.90, "Application for amendment of license, construction permit, or early site permit," Tennessee Valley Authority (TVA) is submitting a request for an amendment to Facility Operating License No. NPF-96 for the Watts Bar Nuclear Plant (WBN) Unit 2. The proposed amendment would revise Technical Specifications (TS) 3.6.12, "Ice Condenser Doors," Surveillance Requirements (SRs) for the WBN U2 ice condenser lower inlet doors. The proposed amendment will revise the surveillance frequency of three SRs that perform visual inspection and torque testing on the ice condenser lower inlet doors during the first cycle after receipt of the Operating License. The proposed amendment is required to preclude a plant shutdown for the purpose of performing lower inlet door surveillance testing.
The enclosure provides a description and technical evaluation of the proposed amendment, a regulatory evaluation, and a discussion of environmental considerations. Attachment 1 to the enclosure provides marked-up copies of SRs 3.6.12.3 through 3.6.12.5, to identify the proposed changes. Attachment 2 to the enclosure provides clean-typed copies of SRs 3.6.12.3 through 3.6.12.5 with the proposed changes incorporated.
TVA requests approval of the proposed License Amendment by February 19, 2016 to
support summer operation of WBN Unit 2. The License Amendment will be implemented within 30 days of approval.
U.S. Nuclear Regulatory Commission CNL-15-225 Page 2 December15 , 2015 TVA has determined that there are no significant hazards considerations associated with the proposed amendment and that the amendment qualifies for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c)(9). The WBN Plant Operations Review Committee and the TVA Nuclear Safety Review Board have reviewed this proposed amendment and determined that operation of WBN Unit 2 in accordance with the proposed amendment will not endanger the health and safety of the public. Additionally , in accordance with 10 CFR 50.91 (b)(1 ), TVA is sending a copy of this letter and the enclosure to the Tennessee Department of Environment and Conservation. There are no new regulatory commitments contained in this letter. Please address any questions regarding this request to Gordon Arent at 423-365-2004. I declare under penalty of perjury that the foregoing is true and correct. Executed on the 15 1 h day of December , 2015. 7 Respe/f lly , L 6'L-. hea President , Nuclear Licensing
Enclosure:
Evaluation of Proposed Amendment cc (Enclosure): U.S. Nuclear Regulatory Commiss i on , Region II NRC Senior Resident Insp e cto r, Watts Bar Nuclea r P l ant NRC Project Manager -Watts Bar Nuclear Plant Director -Division of Radiological Health -Tennessee State Department of Environment and Conservat i on ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-1
Subject:
Application to Revise Technical Specification for Ice Condenser Lower Inlet Door Surveillances (TS-WBN2-15-19) 1.0
SUMMARY
DESCRIPTION
2.0 DETAILED DESCRIPTION
3.0 TECHNICAL EVALUATION
4.0 REGULATORY EVALUATION
5.0 ENVIRONMENTAL CONSIDERATION
ATTACHMENTS
- WBN Unit 2 TS 3.6.12 Ice Condenser Doors Marked-up Pages to Show Changes
- WBN Unit 2 TS 3.6.12 Ice Condenser Doors Clean Typed Pages with Changes Incorporated
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-2 1.0
SUMMARY
DESCRIPTION Pursuant to Title 10 of the Code of Federal Regulations (CFR) §50.90, Tennessee Valley Authority (TVA) is submitting a request for an amendment to Facility Operating License No. NPF-96 for Watts Bar Nuclear Plant (WBN) Unit 2. The proposed amendment will modify Technical Specification (TS) 3.6.12, "Ice Condenser Doors," Surveillance Requirements (SRs) 3.6.12.3 through 3.6.12.5 for the ice condenser lower inlet doors during the first cycle after the receipt of the Operating License.
The proposed amendment is required to allow continued operation of WBN Unit 2 during the summer of 2016 and preclude a shutdown of the unit.
2.0 DETAILED DESCRIPTION Proposed Amendment Surveillance Requirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 have a performance frequency of 18 months except for the first year of operation. In the first year of plant operation, these surveillances are to be performed every three months. TVA is proposing to perform the surveillance within 90 days of entering MODE 4 for the first time and then 180 days thereafter for the first operating cycle. The proposed revision to the SRs was discussed in a November 19, 2015 public meeting between the Nuclear Regulatory Commission and TVA.
3.0 TECHNICAL EVALUATION
3.1 Ice Condenser System Description
The ice condenser is a large passive heat sink to absorb energy from a high energy line break within the primary containment to limit the peak containment pressure and temperature after a Design Basis Accident (DBA). The ice condenser is an annular compartment enclosing approximately 300 degrees of the perimeter of the upper containment compartment. It also penetrates the operating deck so that a portion of the ice condenser extends into the lower containment compartment (Figures 1 and 2). The lower portion of the ice condenser has a series of vertically hinged lower inlet doors exposed to the atmosphere of the lower containment compartment, which, for normal plant operation, are designed to remain closed. At the top of the ice condenser is another set of doors exposed to the atmosphere of the upper compartment, which also remain closed during normal plant operation. Intermediate deck doors, located below the top deck doors, form the floor of a plenum at the upper part of the ice condenser.
These doors also remain closed during normal plant operation. The upper plenum area is used to facilitate surveillance and maintenance of the ice bed.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-3 ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-4 ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-5 The ice bed area consists of the total volume from the floor of the ice condenser to the intermediate deck doors. There are 1944 ice baskets that are located within the ice bed containing approximately 2,750,700 pounds of ice. The ice baskets are designed and positioned within the ice bed in an arrangement to promote heat transfer from steam to ice. This arrangement enhances the ice condenser's primary function of condensing steam and absorbing heat energy released to the containment during a DBA. This limits the containment pressure and temperature response to a DBA and also reduces the release of fission product radioactivity from containment to the environment in the event of a DBA.
In the event of a DBA, the ice condenser lower inlet doors (located below the operating deck) open due to the pressure rise in the lower compartment. This allows air and steam to flow from the lower compartment into the ice condenser. The resulting pressure increase within the ice condenser causes the intermediate deck doors and the top deck doors to open, which allows the air to flow out of the ice condenser into the upper compartment. Steam condensation within the ice condenser limits the pressure and temperature buildup in containment. A divider barrier separates the upper and lower compartments and ensures that the steam is directed into the ice condenser.
The ice is adequate to absorb the initial blowdown energy from steam and water released during a DBA and the additional heat loads that would enter containment early in the event following the initial blowdown. The additional heat loads would come from the residual heat in the reactor core, the hot piping and components, and the secondary system, including the steam generators. As the ice bed melts out, the containment spray system becomes the primary means of energy removal from the containment atmosphere. During the post blowdown period, the Air Return System (ARS) returns upper compartment air through the divider barrier to the lower compartment. This serves to equalize pressures in containment and to continue circulating heated air and steam from the lower compartment thr ough the ice condenser where the heat is removed by the remaining ice.
It is important for the ice to be uniformly distributed around the 24 ice condenser bays and for open flow paths to exist around the ice baskets. This is especially important during the initial blowdown so that the steam and water mixture entering the lower compartment does not pass through only part of the ice condenser, depleting the ice there while bypassing the ice in other bays.
The ice condenser doors ensure that the ice stored in the ice bed is preserved during normal operation (doors closed) and that the ice condenser functions as designed if called upon to act as a passive heat sink following a DBA.
Surveillance Requirement 3.6.12.3, SR 3.6.12.4 and SR 3.6.12.5, require entry into the lower compartment of the primary containment at WBN Unit 2. This is a high radiation area when the plant is in operation and permanent access to the lower inlet doors is not available. These three surveillances may only be performed when the unit is in Mode 3 or lower. Thus, performance of one or more of these surveillance in the first year will require an otherwise unscheduled shutdown of WBN Unit 2.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-6 3.2 Basis for Proposed License Amendment The requirements of SRs 3.6.12.3, 3.6.12.4, and 3.6.12.5 provide inspections and tests to ensure the operability of the ice condenser lower inlet doors. Specifically, SR 3.6.12.3 requires inspections of the doors to identify ice, frost, or debris which may restrict their opening in a design basis event. SRs 3.6.12.4 and 3.6.12.5 require torque tests for opening and modulating to ensure proper door function.
The SRs for operability of the ice condenser lower inlet doors are essentially the same for all ten ice condenser units in the United States. The requirement to check operability of the doors every 3 months for the first year of operation was a common feature of the TS for the ice condenser plants. The subsequent surveillance frequency was every six months and the frequency for each of these SRs was then extended to the current value of 18 months as operating experience was gained.
The frequent surveillance testing intervals initially required were reasonable given that there was no operating experience, testing done at Westinghouse Electric Corporation Waltz Mill Facility could not replicate containment environmental conditions with respect to lower inlet door performance during normal operation, and the safety importance of the ice condenser in assuring containment integrity in the event of a Loss of Coolant Accident (LOCA) or other DBA. The current surveillance frequency, typically 18 months, is supported by many years of ice condenser operating experience with few failures of the doors to meet the acceptance criteria. None of the failures that have occurred were found to be safety significant.
The following discussion provides the basis for revising the surveillance frequency for each of the SRs.
3.2.1 Surveillance Requirement 3.6.12.3
This SR requires inspection of the ice condenser lower inlet doors to identify ice, frost or debris which may restrict their opening in a design basis event. Data from WBN Unit 1 performances of the SR going back to issuance of the Low Power License in November 1995, indicates that ice, frost or debris have not been a problem. There was one instance identified in February 1999 where frost build-up was sufficient to increase the opening torque for some doors beyond the value allowed in SR 3.6.12.4.
The cause of the ice build-up was a known steam leak in a steam generator man-way cover. Based on the WBN Unit 1 performances of this test since fuel load, it is expected that inspection results for WBN Unit 2 at the proposed frequency would show highly reliable performance of the ice condenser lower inlet doors. A review of licensee event reports from the other ice condenser plants was conducted. The information showed that the WBN Unit 1 experience was typical. An initial test on the lower inlet doors at WBN Unit 2 performed in May 2015 was successful without issue. This test will be performed again prior to WBN Unit 2 initial entry into Mode 4. The lower inlet doors are very reliable and are not prone to ice buildup or blockage. If an issue was found with the doors, it was determined not to be safety significant.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-7 This is normally an 18-month surveillance as supported by the operational data, thus, performing the surveillance at least twice in the first cycle of WBN Unit 2 operation would
not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extend beyond the currently planned end of cycle date.
Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public.
3.2.2 Surveillance Requirement 3.6.12.4 This SR requires verification that the torque required to open the lower inlet doors is less than or equal to 675 inch-lbs. This verification provides assurance that no doors become stuck in the closed position during a design basis event such as a large break LOCA. Testing of the doors on WBN Unit 1 show the values obtained were within the acceptance criteria and ranged from 160.5 inch-lbs to 601.9 inch-lbs. As was discussed in Section 3.2.1, it was generally the performance of this surveillance that identified some level of ice build-up on one or more lower inlet doors. WBN Unit 1 has not experienced a failure of this surveillance other than the one described earlier that occurred in 1999. The industry information shows that the identification of ice build-up is associated with the performance of this surveillance.
There were three cases where high torque values were identified that did not involve ice build-up on the lower inlet doors. One instance occurred at the Sequoyah Nuclear Plant in 1992. The lower inlet doors on both Sequoyah units were made inoperable because the concrete floor of the ice condenser had expanded upwards due to water intrusion in insulating material within the floor and the subsequent expansion due to freezing. This event caused a number of the lower inlet doors to experience binding. A very similar event occurred at one non-TVA ice condenser plant. The third event occurred at a non-TVA plant when door blocks that are installed during refueling outages to prevent inadvertent opening of the lower inlet doors were left in place. An initial test on the lower inlet doors at WBN Unit 2 performed in May 2015 was successful without issue. This test will be performed again prior to WBN Unit 2 initial entry into Mode 4.
This is normally an 18-month surveillance as supported by the operational data, thus, performing the surveillance at least twice in the first cycle of WBN Unit 2 operation would
not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-8 currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extends beyond the currently planned end of cycle date.
Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public.
3.2.3 Surveillance Requirement 3.6.12.5 This SR verifies that the lower inlet doors have not developed excessive friction and that the return springs are producing a door return torque within required limits. To obtain these values, a measurement is taken for the opening and closing torque (door at 40 degrees open position) and a calculation performed using these values to arrive at the frictional value.
Each of these values is verified against the acceptance criteria. This verification ensures that, in the event of a small break LOCA or Steam Line Break, the 24-door pairs open uniformly. Opening uniformly assures that during the initial blowdown phase, the steam and water mixture entering the lower compartment does not pass through only part of the ice condenser, depleting the ice in one bay or group of bays, while bypassing the ice in other bays.
Since WBN Unit 1 was issued a license on November 9, 1995, this surveillance has been successfully performed numerous times. In one test that was performed in 1996, 15 of the lower inlet doors exhibited a higher torque value than the acceptance criteria.
Two doors had torque values that were moderately higher than the acceptance criteria (23 and 13 percent respectively). The remaining thirteen doors had torque values that were 2.8 percent or 9.5 inch-lbs higher than the acceptance criteria. The doors were exercised in place and the tests were performed again successfully. The doors still modulated back towards the closed position. A review of industry data shows few failures of this surveillance criteria. Thus, as was the case for SR 3.6.12.3 and SR 3.6.12.4, the lower inlet doors are highly reliable. An initial test on the lower inlet doors at WBN Unit 2 performed in May 2015 was successful without issue. This test will be performed again prior to WBN Unit 2 initial entry into Mode 4.
This is normally an 18-month surveillance as supported by the operational data, thus, performing the surveillance at least twice in the first cycle of WBN Unit 2 operation would
not impact the capability of the doors to perform their safety function. The proposed surveillance frequency of within 90 days of entry into MODE 4 and every 180 days thereafter provides for at least two surveillances during the first operating cycle. If the operating cycle is extended beyond the currently scheduled end date, additional surveillances are required every 180 days. The inclusion of a requirement for an initial surveillance within 90 days of entering MODE 4 allows the identification of potential, but currently unforeseen, problems that might affect the lower inlet doors. The inclusion of the 180 day requirement thereafter for the first cycle provides for additional testing during the first cycle should it extends beyond the currently planned end of cycle date.
Therefore, there is reasonable assurance that the proposed surveillance interval extension would have no impact on the health and safety of the public.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-9
4.0 REGULATORY EVALUATION
4.1 Applicable Regulatory Requirements and Criteria
The proposed amendment to Surveillance Requir ement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 do not reduce or change Watts Bar Nuclear Plant Unit 2's level of compliance with the following applicable regulations and requirements:
- 10 CFR 20, "Standards For Protection Against Radiation," provides guidance and criteria for assuring, among other requirements, that occupational dose rates are kept as low as reasonably achievable.
- 10 CFR 50, Appendix A, GDC 16, "Containment design," specifies that the containment is an essentially leak-tight barrier to prevent the uncontrolled release of radioactivity to the environment and that containment design conditions important to safety are maintained.
- 10 CFR 50, Appendix A, GDC 38, "Containment heat removal," specifies that the containment pressure and temperature are rapidly reduced consistent with the functioning of other associated systems following a LOCA and maintains them at
acceptably low levels.
- 10 CFR 50, Appendix A, GDC 50, "Containment design basis," specifies that the containment structure and the containment heat removal systems be designed, with sufficient margin, such that the pressure and temperature resulting from a loss of coolant accident can be accommodated without exceeding the design leakage rate.
4.2 Precedent Watts Bar Nuclear Plant Unit 1 was granted a one time extension to the surveillance testing frequency for the lower inlet doors during the first year of operation in September 1996 [ADAMS Accession No. ML020780182]. In October 1984, the McGuire Nuclear Station was granted permanent extensions to the ice condenser surveillance frequencies [ADAMS Accession No. ML013180209].
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-10 4.3 Significant Hazards Consideration The Tennessee Valley Authority (TVA) proposes to amend Facility Operating License No. NPF-96 for the Watts Bar Nuclear Plant (WBN) Unit 2 by requesting a change to Technical Specifications (TS) Surveillance R equirement (SR) 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 in the first cycle after receipt of the Operating License. This proposed amendment will modify the three SRs by deleting the frequency condition:
3 month during the first year after receipt of license
And adding the following condition:
Once with 90 days of initial entry into MODE 4 and 180 days thereafter, for the first operating cycle.
TVA has concluded that the amendment to WBN Unit 2 TS 3.6.12 does not involve a significant hazards consideration. TVA's conclusion is based on its evaluation in accordance with 10 CFR 50.91(a)(1) of the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below:
- 1. Does the proposed amendment involve a significant increase in the probability or consequence of an accident previously evaluated?
Response: No.
The ice condenser is a passive heat removal plant feature. The proposed amendment to the TS 3.6.12 does not change the design, physical features or the function of the ice condenser or the ice condenser doors. The ice condenser is not an accident initiator, thus the proposed amendment does not increase the probability of an accident previously evaluated.
The ice condenser is credited in mitigating the consequences of postulated Design Basis Accidents (DBAs) and remains capable of performing its design basis functions. The proposed amendment to the SRs during the first cycle of WBN Unit 2 operation does not change the ice condenser configuration or how it behaves in the event of a DBA. Thus it is concluded that a significant increase in the consequences of an accident previously evaluated will not occur as a result of the proposed amendment.
Therefore, the proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-11 2. Does the proposed amendment create the possibility of a new or different kind of accident from any accident previously evaluated?
Response: No. The proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated. The proposed amendment does not introduce any new modes of plant operation, change the design function of the ice condenser or any other Structure System or Component (SSC), or change the mode of operation of the ice condenser or any other SSC. There are no new equipment failure modes or malfunctions created as the ice condenser and ice condenser lower inlet doors continue to operate in the same manner assumed in the accident analysis. The ice condenser is a passive post-accident heat removal feature that is not an accident initiator.
Therefore, the proposed amendment does not creat e the possibility of a new or different kind of accident from any previously evaluated.
- 3. Does the proposed amendment involve a significant reduction in a margin of safety?
Response: No. Ice condensers have been in-service at nine nuclear units in the United States for many years. Operating experience has shown that an 18-month surveillance frequency for evaluating operability is appropriate for the lower inlet doors. The proposed amendment to perform a revised schedule of lower inlet door surveillances in the first cycle before transitioning to the standard 18-month surveillance frequency does not result in a significant reduction in the margin of safety.
Therefore, since there is no adverse impact of this amendment on the WBN Unit 2 safety analysis, there is no significant reduction in the margin of safety of the plant.
4.4 Conclusions Tennessee Valley Authority evaluated the proposed change to WBN Unit 2 TS SR 3.6.12.3, SR 3.6.12.4, and SR 3.6.12.5 to perform the surveillance tests within 90 days of initial entry into MODE 4 and every 180 day thereafter, for the first operating cycle of operation for Watts Bar Nuclear Plant Unit 2. The evaluation determined that there is substantial operating experience associated with surveillance testing performed at the nine operating nuclear units in the United States with ice condenser containments that establishes that the lower inlet doors are highly reliable and have a very low failure frequency. The evaluation also determined that the observed failures to meet the surveillance requirements would not prevent the doors, much less the ice condenser as a whole, from performing its primary safety function of limiting the peak containment pressure and temperature after a design basis event. The evaluation establishes that the proposed amendment does not constitute a substantial safety hazard. The proposed amendment prevents an otherwise unnecessary shutdown of the WBN Unit 2.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-12
5.0 ENVIRONMENTAL CONSIDERATION
The proposed amendment revises the surveillance frequency for three SRs associated with TS 3.6.12 for the ice condenser lower inlet doors to perform the surveillance tests within 90 days of initial entry into MODE 4 and every 180 day thereafter, for the first operating cycle of operation for Watts Bar Nuclear Plant Unit 2. The proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.
ENCLOSURE EVALUATION OF PROPOSED AMENDMENT E-13 ATTACHMENTS Attachment 1 - WBN Unit 2 TS 3.6.12 Ice Condenser Doors Marked-up Pages to Show Changes - WBN Unit 2 TS 3.6.12 Ice Condenser Doors Clean Typed Pages with Changes Incorporated
ENCLOSURE ATTACHMENT 1
WBN Unit 2 TS 3.6.12 Ice Condenser Doors Marked-up Pages to Show Changes
Ice Condenser Doors 3.6.12 Watts Bar - Unit 2 3.6-29 ACTIONS (continued) CONDITION REQUIRED ACTION COMPLETION TIME A. Required Action and associated Completion Time of Condition A or C not met. D.1 Be in MODE 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> AND D.2 Be in MODE 5. 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />
SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.6.12.1 Verify all inlet doors indicate closed by the Inlet Door Position Monitoring System.
12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> SR 3.6.12.2 Verify, by visual inspection, each intermediate deck door is closed and not impaired by ice, frost, or debris. 7 days SR 3.6.12.3 Verify, by visual inspection, each inlet door is not impaired by ice, frost, or debris.
3 months during first year after receipt of license Once within 90 days of initial entry into MODE 4 and 180
days thereafter, for the first operating cycle. AND 18 months Ice Condenser Doors 3.6.12 Watts Bar - Unit 2 3.6-30 SR 3.6.12.4 Verify torque required to cause each inlet door to begin to open is 675 in-lb.
3 months during first year after receipt of license Once within 90 days of initial entry into MODE 4 and 180
days thereafter, for the first operating cycle. AND 18 months SR 3.6.12.5 Perform a torque test on a sampling of 50% of the inlet doors.
3 months during first year after receipt of license Once within 90 days of initial entry into MODE 4 and 180
days thereafter, for the first operating cycle. AND 18 months (continued)
Ice Condenser Doors 3.6.12 Watts Bar - Unit 2 3.6-31 SURVEILLANCE REQUIREMENTS (continued) SURVEILLANCE FREQUENCY SR 3.6.12.6 Verify for each intermediate deck door: a. No visual evidence of structural deterioration; b. Free movement of the vent assemblies; and c. Free movement of the door.
3 months during first year after receipt of license AND 18 months SR 3.6.12.7 Verify, by visual inspection, each top deck door: a. Is in place;
- b. Free movement of top deck vent assembly; and
- c. Has no condensation, frost, or ice formed on the door that would restrict its opening.
92 days Enclosure Attachment 2
WBN Unit 2 TS 3.6.12 Ice Condenser Doors Clean Typed Pages with Changes Incorporated
Ice Condenser Doors 3.6.12 Watts Bar - Unit 2 3.6-29 ACTIONS (continued) CONDITION REQUIRED ACTION COMPLETION TIME B. Required Action and associated Completion Time of Condition A or C
not met. D.1 Be in MODE 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> AND D.2 Be in MODE 5. 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />
SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.6.12.1 Verify all inlet doors indicate closed by the Inlet Door Position Monitoring System.
12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> SR 3.6.12.2 Verify, by visual inspection, each intermediate deck door is closed and not impaired by ice, frost, or debris. 7 days SR 3.6.12.3 Verify, by visual inspection, each inlet door is not impaired by ice, frost, or debris.
Once within 90 days of initial entry into MODE 4 and 180 days thereafter, for the first operating cycle.
AND 18 months Ice Condenser Doors 3.6.12 Watts Bar - Unit 2 3.6-30 SR 3.6.12.4 Verify torque required to cause each inlet door to begin to open is 675 in-lb.
Once within 90 days of initial entry into MODE 4 and 180
days thereafter, for the first operating cycle.
AND 18 months SR 3.6.12.5 Perform a torque test on a sampling of 50% of the inlet doors.
Once within 90 days of initial entry into MODE 4 and 180
days thereafter, for the first operating cycle.
AND 18 months SR 3.6.12.6 Verify for each intermediate deck door: d. No visual evidence of structural deterioration;
- e. Free movement of the vent assemblies; and
- f. Free movement of the door.
3 months during first year after receipt of license AND 18 months SR 3.6.12.7 Verify, by visual inspection, each top deck door: d. Is in place;
- e. Free movement of top deck vent assembly; and f. Has no condensation, frost, or ice formed on the door that would restrict its opening.
92 days