ML20140C818

Proposed Tech Specs Changing Isolation Logic for Containment Isolation Valves FCV-90-107 & FCV-90-117. Justification Encl

ML20140C818
Person / Time
Site:	Sequoyah
Issue date:	06/13/1984
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML20140C810	List: ML20140C807 ML20140C818
References
NUDOCS 8406190476
Download: ML20140C818 (7)

Text

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25. ICV-b7-296 ERCW - tip ('mpt Clrs 60 60

26. ICV-6/-297 ERCW - tip Cmpt Cirs 60 2/. FCV-6/-298 ERCW - tip Cmpt Cirs 60

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29. I CV- /0-li9 CCS from RCP Oil Coolers w 60

30. ICV-70-90 RCP Ihermal llarrier Ret D 60

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34. FCV-90-107 Cntnt Bldg Lwr Compt Air Mon

35. FCV-90-108 59 Cntnt Bldg. Lwr Compt Air Mon 5

36. FCV-90-109 Cntnt Bldg Lwr Compt Air Mon

37. 5 FCV-90-110 Cntnt Bldg Lwr Compt Air Mon

38. 5 FCV-90-111 Cntnt Bldg Lwr Compt Air Mon

39. FCV-90-113 5 40.

Cntnt Bldg Lwr Compt Air Mon 5 -Note 1 FCV-90-114 Cntnt Bldg Lwr Compt Air Mon

41. FCV-90-ll5 5 Cntnt Bldg Lwr Compt Air Mon 5

42. FCV-90-116 Cntnt Bldg Lwr Compt Air Mon

43. FCV-90-111 5

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C. PilASE "A" CONIAltlMENI VENT IS0lAll0N

1. FCV-30-7 Upper Compt Purge Air Supply 4

' 2. FCV-10-8 'llpper Compt Purge Air Supply 4

3. FCV-30-9 Upper Compt Purge Air Supply 4

4. (CV-30-lO Upper Compt Purge Air Supply 4

5. ICV-30-14 1.ower Compt Purge Air Supply 4

6. ICV-30-IS l.ower Compt Purge Air Supply 4

7. ICV-30-16 l ower Compt Purge Air Supply 4

8. ICV-30-l/ Lower Compt Purge Air Supply 4

9. ICV-30-19 lust Room Purge Air Supply 4

10. ICV-30-20 Inst Room Purge Air Supply , ,4

11. ICV-10-37 -Iouer Compt Pren ure Relief 4 i 12. ICVm!O-40 tower Compt Pressure Relief 4

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13. FCV-30-50 Upper Compt Pur9e Air Exh 4

14. ICV-30-61. Upper Compt Purue Air Exh 4

15. ICV-30-52 upper Compt Purge Air Exb 4

16. ICV-3u-53 lipper Compt Purge Air Exh 4

17. ICV-30-S6 1ower Compt Purge Air Exh 4

18. ICV-30-57 Lower Compt Purge Air Exh 4

19. ICV-30-S8 Inst Room Purge Air Exh 4

20. ICV-30-$9 Inst I!oom Purge Air Exh 4 a

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Note 1 This change will become effective upon completion of the modifications s#1 , associated with this change.

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13. FCV-30-50 Upper Compt Purge Air Exh 4

14. ICV-30-S) Upper Compt Purge Air Exh 4

15. FCV-3u-52 Upper Compt Purge Air Exh 4

16. ICV-30-53 Upper Cosopt Purge Air Exh 4

17. ICV-30-56 Lower Compt Purge Air Exh 4

18. . ICV-30-57 Lower Compt Purge Air Exh 4

19. ICV-30-Sfi Inst Room Purge Air Exh 4

20. ICV-30-59 Inst Room l' urge Air Exh 4 1

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1. FCV-30-46 Vacuum Relief Isolation Valve 25

2. FCV-30-47 Vacuum Relief Isolation Valve 25

3. FCV-30-48 Vacuum Relief Isolation Valve 25 i

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associated with this change.

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21. ICV-67-139 ERCW - Up Cmpt Cirs 60

22. ICV-67-141 ERCW - Up Cmpt Clrs 60

23. ICV-67-142 ERCW - lip Cmpt Cirs 60

24. ICV-61-295 ERCW - tip Cmpt Clrs 60

25. ICV-b/-296 ERCW - Up Cmpt Cirs 60

26. I CV-6 /-29/ LRCW - lip Cmpt Cirs 60

27. tCV-6/-298 ERCW - tip Cmpt Cirs 60

28. ICV-/O-8/ RCP Iliermal llarrier Ret 60

29. ICV-/O-89 CCS from RCP Oil Coolers 60 a 30. FCV-70-90 RCP Ihermal Barrier Ret 60 D 31. I CV- /0-92 -

CCS trom RCP Oil Coolers 60 n' 32. ICV-/O-134 lu HCP liiermal Barriers 60 ib 33. ICV-70-140 CCS to RCP Oil Coolers 60

34. FCV-90-107 Cntnt Bldg Lwr Compt Air Mon 59

35. FCV-90-108 Cntnt Bldg Lwr Compt Air Mon 5

36. FCV-90-109 Cntnt Bldg Lwr Compt Air Mon 5

37. FCV-90-110 Cntnt Bldg Lwr Compt Air Mon 5

38. FCV-90-111 Cntnt Bldg Lwr Compt Air Mon 5

39. FCV-90-113 Cntnt Bldg Lwr Compt Air Mon 5 -Note 1

40. FCV-90-114 Cntnt Bldg Lwr Compt Air Mon 5

41. FCV-90-115 Cntnt Bldg Lwr Compt Air Mon 5

3. 42. FCV-90-116 Cntnt Bldg Lwr Compt Air Mon 5

43. FCV-90-117 ' Cntnt Bldg Lwr Compt Air Mon 5 -

'C. PHASE "A" CutilAINMENT VENT ISOLAl' ION

1. FCV-30-7 Upper Compt Purge Air Supply 4

2. FCV-30-8 - Upper Compt Purge Air Supply 4

3. FCV-30-9 Upper Compt Purge Air Supply 4

4. ICV-30-10 Upper Compt Purge Air Supply 4

5. ICV-30-14 Lower Compt Purge Air Supply 4

6. fCV-30-15 Lower Compt. Purge Air Supply 4

7. ICV-30-16 l ower Compt. Purue Air Supply 4 ~

8. ICV-30-l/ Iower Compt Purge Air Supply 4

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9. ICV-30-19 Inst Room Purge Air Supply 4

10. ICV-30-20 Inst Room Purge Air Supply 4

11. ICV-30-37 Lower Compt Pressure Relief 4 l 12. FCV-30-40 Lower Compt Pressure Relief 4 4 -

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ENCLOSURE 2 SEQUOYAH NUCLEAR PLANT JUSTIFICATION FOR PROPOSED TECHNICAL SPECIFICATION CHANGE This change is needed to alleviate conflicting technical specification requirements when a containment ventilation isolation occurs. This change will also improve the monitoring capabilities during several accident scenarios (i.e., steam generator tube ruptures and steam line breaks and loss-of-coolant accidents outside containment).

One containment gas and one containment particulate radiation monitor are required to be operable during power operation by Technical Specifica-tion 3.4.6.1. When a containment ventilation isolation occurs, these radiation monitors are isolated. The action statement in Technical Speci-fication 3.4.6.2 requires that the monitors be returned to service within six hours. Plant shutdown is required if the monitors are not restored to service within this time. The containment ventilation isolation signal (a subset of phase A) must be reset using HS-30-65A in order to open the radiation monitor isolation valves if the ventilation isolation signal persists. Containment ventilation isolation is automatically initiated by high gas or particulate radioactivity inside containment, high purge exhaust radioactivity, or a safety injection signal. Reset of the isola-tion signal with a high radiation condition present makes the containment ventilation isolation system inoperable. The radiation monitor isolation valves cannot be open when the ventilation isolation system is inoperable without violating action 19 for Technical Specification 3.3.2. Violation of action 19 invokes Technical Specification 3.0.3 which requires that the abnormal situation be corrected within one hour or complete a plant shut-down within the next six hours. In short, a high radiation signal inside containment can cause a noncompliance with one limiting condition for operation which can only be rectified by not complying with another limiting condition for operation. The only solution presently is a plant shutdown. This is unreasonable because radiation levels below that allowed by 10 CFR Part 20 can lead to containment ventilation isolation. Changing the isolation signal for the radiation monitor isolation valves from containment ventilation isolation to either phase A or phase B isolation would eliminate the operation problems associated with the current design and technical specifications. TVA has chosen to change them to phase B.

Changing the isolation signal to the phase B signal rather than phase A improves the capability of the reactor operator to monitor radioactivity inside the containment for accident scenarios that do not release energy to the reacter containment without reducing the margin of safety built into the plant. Specifically, the operator could monitor the radioactivity levels inside containment during steam generator tube ruptures, loss-of-coolant accidents involving piping outside of containment, and steam line break accidents involving piping downstream of the main steam isolation valves. These accidents do not initiate a phase B isolation signal. The additional radioactivity information would enable the operator to better monitor normal reactor coolant leakage. The expected radiation levels would be within the normal operational range. In addition, this change would allow the operator the opportunity to investigate radiation anomalies that lead to ventilation isolations without reliance on any technical specification action statements.

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l l SEQUOYAH NUCLEAR PLANT l

SIGNIFICANT HAZARDS CONSIDERATIONS FOR PROPOSED TECHNICAL SPECIFICATION CHANGES i

i 1. Is the probability of an occurrence or the consequences of an accident evaluated in the safety analysis report significantly increased?

p No. Changing the radiation monitor isolation valves from containment l ventilation isolation to phase B isolation does not reduce the

isolation capability of the containment system. The radiation monitors l are sealed systems which draw air from and return air to the containment. Having the monitors remain unisolated for high-energy line breaks outside of containment improves the capability of the reactor operator to monitor conditions inside containment. For large high-energy line breaks inside containment,the phase A (ventilation isolation is a subset of phase A) and phase B setpoints are very close together. Both signals would be generated at essentially the same time. The containment isolation response time for these valves would remain unchanged.

2. Is the possibility for an accident of a new or different type than previously evaluated in the safety analysis report created?

No. This change only affects the initiating isolation signal for these valves. The capability of the valves to close and the capability of the various isolation signals to be generated have already been analyzed in the safety analysis report.

3 Is the margin of safety significantly reduced?

No. The radiation monitor systems are sealed systems used to measure containment radioactivities within normal ranges. The isolation capability remains for high-energy line breaks inside containment (those that generate a phase B isolation signal) while improved (normal range) monitoring capability is provided for those events outside containment that lead to containment (phase A) isolation. The margin .

of safety may actually be increased because of improved monitoring capabilities for events that do not challenge the containment boundary while providing the same containment isolation capability for events that do challenge the containment boundary.

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-2 The capability of the containment isolation system would not be signifi-cantly changed for large energy release accidents inside the containment.

The phase A setpoint is 1.54 psig and the phase B setpoint is 2.81 psig.

Both . signals, phase A and phase B, are generated at essentially the same time during large loss-of-coolant and steam line break accidents. The containment isolation response time for the valves would be essentially unchanged. In addition, these containment radiation monitors consist of an enclosed system that draws air from the containment and returns it there.

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