TXX-6126, Forwards Addl Info,Per 860227 Request,Re 850517 Request to Allow Use of Manual Operators on MSIV Bypass Valves, Including Comments on Proposed Tech Spec Rev & FSAR Amend 56
| ML20211M041 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 12/08/1986 |
| From: | Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | Noonan V NRC - COMANCHE PEAK PROJECT (TECHNICAL REVIEW TEAM) |
| References | |
| TXX-6126, NUDOCS 8612160223 | |
| Download: ML20211M041 (24) | |
Text
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Log # TXX-6126 File # 10010 7
H, 910.3 916 TEXAS UTILITIES GENERATING COMPANY SKYWAY TOWER. 403 980RTH OLIVE WFREET. I.R St. DALt.AS. TEXAS TSSDS December 8, 1986 l
l IIcN ve Ice S Int Director of Nuclear Reactor Regulation Attn: Mr. Vince S. Noonan, Director Comanche Peak Project Division of Licensing U. S. Nuclear Regulatory Commission Washington, D. C.
20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 and 50-446 NRC REQUEST FOR ADDITIONAL INFORMATION CONCERNING MSIV BYPASS VALVES
Dear Mr. Noonan:
By letter dated February 27, 1986, the NRC staff requested additional information concerning the TUGCo request of May 17, 1985, to allow the use of i
manual operators on the main steam isolation valve (MSIV) bypass valves.
In I
addition, the NRC staff provided comments on the proposed technical specification revision and on the related FSAR changes provided by Amendment
- 56. provides responses to the NRC staff request for additional information. responds to the NRC staff comments on the TUGCo proposed technical specification revision and includes marked up pages from the CPSES draft technical specifications. responds to the NRC staff comments on FSAR Amendment 56 and includes an advance copy of FSAR revisions which will be included in a future FSAR amendment.
Very truly yours,
$W W. G. Counsil BSD/amb Attachments c - NRC (0 + 40 copies)
C. Trammell
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TXX-6126 December 8, 1986 i
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TXX-6126 December 8, 1986 Page 1 of 4 RESPONSES TO NRC REQUEST FOR ADDITIONAL INFORMATION OVESTION 1 Address the operation of the MSIV bypass valve by " handwheel" manual actuation and provide information on operator radiation exposure based on its location, dose rate in the area that must be accessed and occupied for its actuation, the time spent in the area, and the frequency of need to actuate, maintain, service, etc., the valve under normal and emergency plant conditions.
RESPONSE
Question 1 is a general statement of concerns. The concerns are addressed in the specific responses to Questions 2, 3, and 4.
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TXX-6126 December 8, 1986 Page 2 of 4 OVESTION 2 Describe the occupational radiation exposure in terms of man-rem that will be received as compared to that which would have been received under the previously installed automatic operating conditions.
RESPONSE
The main steam lines are the only potential radiation sources in the area during normal operation. The expected average radioactivity concentration in the steam leaving the steam generators has been calculated using the data and methodology in ANSI N237-1976. With this source in the main steam line an the bypass line, the calculated dose rate near the bypass valve is 5.8x10 g mrem /hr. The time required to enter the area, open or close the valve, and leave the area is expected to be 5 minutes or less. Since the valves are required to be locked closed during power operation, they will only be operated during plant startup. Only one bypass valve is required per startup, however, each bypass valve may be utilized (only one bypass valve opened at a time) to provide more even steam line heatup and valve usage during the startup. Assuming that each bypass valve is opened and later locked closed during each startup, the total time required in the area will be no more than 40minutesperstargup. The predicted occupational radiation exposure is approximately 4x10- man-rem per plant startup. Thus the calculated occupational radiation exposure per startup, and the maximum accumulated annual exposure for any reasonable anticipated startup frequency would be negligible.
Maintenance on the valves will be performed with the plant shutdown, so the expected radiation levels will be even lower. Also, the manually operated valves are expected to require less maintenance than remote operated valves.
Thus, if radiation levels in the area were significant, the radiation exposure encountered during maintenance would be comparatively less with the manual valves.
TXX-6126 December 8, 1986 Page 3 of 4 OVESTION 3 During Mode 2, if a Steam Generator Tube Rupture event were to occur, would the environment, e.g., radiation level / temperature, permit an operator to manually close the valve without exceeding part 10CFR20 guidelines?
RESPONSE
The radiation level near the valve has been calculated assuming that a steam generator tube rupture occurs during startup, and that the bypass valve is open in the line associated with that steam generator.
Primary coolant activities are based on 1% defective fuel and include iodine spiking.
Furthermore, the conservative assumption is made that the radioactivity concentration per unit mass in the secondary steam is the same as that in the primary coolant. With this postulated accident condition, the calculated dose rate is 4.6 rem /hr. Then, assuming that 5 minutes are required to enter the area and close the valve, the calculated radiation exposure is approximately 0.39 rem. This is lower than the quarterly occupational exposure limit of 1.25 rem.
During normal operation, the maximum predicted temperature in the area is 1040F. Although the steam temperature would increase slightly during a tube rupture accident, the increase in room temperature would not be significant, and access would be permissible.
TXX-6126 Decemb5r 8, 1986 Page 4 of 4 OUESTION 4 Assuming fuel failure before or during the tube rupture described in 3 above, what is the maximum timo available to complete valve closure before radiation exposure becomes excessive per 10CFR part 20 and/or offsite doses become excessive per 10CFR part 100.
RESPONSE
I The 1% defective fuel postulated in the response to question 3 was assumed both before and during the tube rupture accident. The resulting primary coolant activity levels exceed the proposed Technical Specification limits for operation. Thus, startup would not be permitted with these or higher reactor coolant activities. With this conservative assumption the maximum dose rate at the valve is 4.6 rem /hr,'so an individual could spend approximately 16 minutes in the vicinity of the valve at any time during the accident without exceeding the 1.25 rem limit.
The dose at the Exclusion Area Boundary has been calculated using the assumptions that were used to obtain the results for the conservative case with iodine spiking that were reported in FSAR Section 15.6.3, and with the following additional assumptions. The bypass valve is assumed to remain open during the entire 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> period that is required to depressurize the plant following a steam generator tube rupture accident.
Flow through the ruptured tube is assumed to contine for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> at the initial break flow rate. All of the flow through the break is assumed to flow through the bypass valve and to the steam dump system.
3 With these conservative postulated conditions, the calculated whole body gamma dose at the EAB is 1.3 rem, and the thyroid dose is 183 rem. These values are below the 10CFR part 100 limits of 25 rem whole body and 300 rem to the thyroid. Thus, even if the bypass valve remained open, the offsite dose limits would not exceed for more than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
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TXX-6126 December 8, 1986
TXX-6126 December 8, 1986 Page 1 of 4 RESPONSES TO COMMENTS ON TECHNICAL SPECIFICATIONS 1.
Comment Refer to Table 3.6-1; Containment Isolation Valves; 4. Manual Valves; Insert A.
Valve numbers marked 1HV imply power operated,1HV should be changed to IMS.
Response The HV designation is retained in the design even though the operator has been changed (Reference CPSES drawing 2323-M1-0202, Rev. CP-8). This minimizes the number of documents requiring revision and the potential for discrepancies.
2 Comment Refer to Table 3.6-1; Containment Isolation Valves; 7. Steam Line Isolation Signal; Valve 1HV-2323 A; under Line or Service.
Currently this reads " Main Steam From Generator #1. This should read, " Main Steam From Steam Generator #1".
Resoonse See revised Table 3.6-1, page 3/4 6-26.
3.
Comment Refer to Table 3.6-1; Containment Isolation Valves; 7. Steam Line Isolation Signal (Continued); Valve 1HV-2411; under Line or Service. Currently this reads " Main Steam From Steam Generator
- 3. This should read, " Drain From Main Steam Line #3".
Resoonse See revised Table 3.6-1, page 3/4 6-27.
4.
Comment Refer to Table 3.6-1; Table Notations, Note 11. Should read, "All four MSIV Bypass Valves are locked closed in Mode 1.
During Modes 2, 3 and 4 one MSIV Bypass Valve may be opened provided the other three MSIV Bypass Valves are locked closed and their associated MSIVs are closed."
Response See revised Table 3.6-1, page 3/4 6-30.
TXX-6126 December 8, 1986
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P11' M 1 CONTAINMENT ISOLATION VALVES g
ISOLATICN TYPE FSAR TABLE TIME..
LEVEL VALVE NO.
REFERENCE NO."
LINE OR SERVICE (Secondsj TESTIN(
6.
Check Valves (Continued) i 1-88418 63 RHR to Hot leg Loops N.A.
Note
- 2 and #3 15I-3968 104 N
Supply to N.A.
C 2
Accumulators 1CA-016 113 Service Air to N.A.
C Containment 1C6-629 117 CC Return From RCP's N.A.
C Motors ICC-713 118 CC Supply to RCP's N.A.
C Motors ICC-B31 119 CC Return From RCP's
- N.A.
C Thermal Barrier 1CH-024 120 Chilled Water Supply to N.A.
C Containment Coolers i
7.
Steam Line Ir.olation Signal Main St:aam From M 5
Note 1HV-2333A 1
Generator #1 Note
~I 1HV-2333B 2
Main Steam From 5
Note Generator #1 y
1HV-2409 3
Drain From Main Steam 5
Note Line #1 1HV-2334A 6
Main Steam From Steam 5
Nota l
Generator #2 Note 1HV-23348 7
Main Steam From Steam 5
Note
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Generator #2 IliV-2410 8
Drain From Main Steam 5
Note Line #2
,(
1HV-2335A 10 Main Steam From Steam 5
Note Generator #3 Note 44 6-26
TXX-6126 E'h M
December 8, 1986 TABLE 3.6-1 (Continued) gy Page 3 of 4 CONTAINMENT ISOLATION VALVES ISOLATION TYPE TIME' LEVEL FSAR TA8LE VALVE No.
REFERENCE NO.*
LINE OR SERVICE (Seconds)
TESTING 7.
Steam Line Isolation Signal (Continued) 1HV-2335B 12J Main Steam From Steam 5
Note 1 Generator #3 Note I k
5 Note 1 1HV-2411 12 FiainSteamFromSteas lD A rw h > h $3 Generntor nr 1HV-2336A 14 Main Steam From Steam 5
Note 2 Generator #4 Note :
1HV-2336B 15 Main Steam From Steam 5
Note Generator #4 t
1HV-2412-16 Drain from Main Steam 5
Note ~
Line #4 8.
Feedwater Line Isolation Signal 1HV-2134 19 Feedwater to Steam 5
Note Generator #1 1FV-2193 20d Feedwater Tempering
~5 Note Note Line 1HV-2185 20e Feedwater Bypass Line 5
Note 1HV-2135 21 Feedwater to Steam 5
Note Generator #2 1FV-2194 22d Feedwater Tempering 5
Note Note Line 1HV-2186 22e Feedwater Bypass Line 5
Nota 1]iV-2136 23 Feedwater to Steam 5
Note Generator 93 IFV-2195 24d Feedwater Tempering 5
Note'
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Nota Line 1HV-2187 24e Feedwater Bypass Line 5
Note IlYj 1HV-2137 25 Feedwater to Steam 5
Nots Generator #4 J4 ei,- 27
TXX-6126 December 8,1986 Page 4 of'4 TABLE 3.6-1 (Continued) 271. 2 TABLE NOTATIONS Note 8:
These valves located outside containment are normally closed and see a pressure in excess of containment pressure in post-accident conditions.
A valve stem leakage check will be performed on a quarterly basis to assure no significant stem leakage would occur in post-accident conditions.
Note 9:
These valves are classified as " passive" in accordance with Specifi-cation 4.0.5 and are stroke time-tested only following maintenance
- which could effect the stroke time of the valve.
Note 10:
These valves require steam to be tested and are thus not required to be tested until the plant is in MODE 3.
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TXX-6126 December 8, 1986 e
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r-TXX-6126 December 8,- 1986 Page 1 of 12 RESPONSES TO COMMENTS ON FSAR AMENDMENT 56 FSAR Section 3.9B Mechanical Systems and Components 1.
[omment Refer to Table 3.9B-8; Sheet 5; ASME Code Class 2 and Class 3.
Active and Inactive Pumps and Valves; Main Steam Reheat and Steam Dump System. Are b and e the same now? Should b be deleted?
Response See revised Table 3.98-8, sheet 5.
2.
Comment There is a conflict between Table 3.98-8; sheet 5, and Table 3.9B-10 sheet 1 of 12. HV-2333B, HV-23348, HV-23358, HV-23360 should be deleted from the Active Valve list.
Resoonse See revised Table 3.98-10, sheet 1.
FSAR Section 6.2 Containment Systems 3.
Comment Assuming Table 6.2.4-2 Sheet 1 of 10 is for both Active and Inactive valves, the "HV" designator should be changed on the MSIV bypasses and the primary method of actuation should be
" Local Manual" to clearly differentiate from the remote manual actuators.
Response The HV designation is retained in the design even though the operator has been changed (Reference CPSES drawing 2323-M1-0202, Rev. CP-8). This minimizes the number of documents requiring revision and the potential for discrepancies. Also see revised Table 6.2.4-2, sheet 1.
4.
Comment On Table 6.2.4-3 Sheets 1 and 2 of 14, the containment isolation signal for items 2, 7,11, and 15 should be deleted since they no longer receive a containment isolation signal.
Response See revised Table 6.2.4-3, sheets 1 and 2.
i 5.
Comment Figure 6.2.4-1; Sheet 5 of 10; Valve arrangement 17; Outside Containment; should indicate locked closed.
Response See revised Figure 6.2.4-1, sheet 5 of 10.
l 6.
Comment In Section 10.3.2.3.1, justify the elimination of the need for main steam isolation valves to stop flow from either direction within 10 seconds after a steam line break to prevent uncontrolled steam releases from more than one steam generator (Page 10.3-7 and 10.3-9 Amendment 56).
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TXX-6'126 December 8, 1986 Page 2 of 12 RESPONSES TO COMMENTS ON FSAR AMENDMENT 56 Resoonse The 10 second requirement was based on large steam line break analyses. The 10 second limit was deleted so that the statement would also be applicable to small steam line breaks.
4 7.
Comment The words "an integral" should be removed and replaced with "a manual" (Page 10.3-7 Amendment 56).
Response See revised page 10.3-7.
8.
Comment Should the bypass valve be locked closed during." power operation" or when " containment integrity" is required (Page 10.3-7 Amendment 56)?
Response The bypass valves should be locked closed during power operation as stated in Amendment 56 (References CPSES drawings 2323-M1-0202, Rev. CP-8, and 2323-M1-2202-10, Rev. CP-1).. Technical Specification Table 3.6-1, Note 11, covers the requirement for containment integrity.
9.
Comment The following sentence should be deleted; "Each MSIV bypass valve also has a two train module, open, close and auto switch on the control board." (Page 10.3-8 Amendment 56).
l Response See revised page 10.3-8.
- 10. Comment The following sentence should be deleted; "There is no provision for testing the bypass valves." (Page 10.3-9 Amendment 56).
Resoonse See revised page 10.3-9.
- 11. Comment Refer to Section 10.3.2.4; Main Steam Isolation Bypass Valves.
1 This paragraph should clearly explain that all four MSIV bypass valves are locked closed in Mode 1.
During Modes 2, 3, and 4 one MSIV bypass valve may be opened provided the other three MSIV bypass valves are locked closed and their associated MSIVs are closed.
I Resoonse See revised section 10.3.2.4.
- 12. Comment Refer to Figure 10.3-1; Sheet 1.
Designation HV should be replaced with MS for the subject valves.
Response See the response to question 3, above.
TXX-6126 Dec;;ber 8, 1986 Page 3 of 12 CPSES/FSAR TABLE 3.9B-8 (Sheet 5)
ASME CODE CLASS 2 AND CLASS 3 ACTIVE AND INACTIVE PUMPS AND VALVES Comoonent Class Operation
- System Valves Including and Downstream From Containment Isolation Valves a.
A b.
Manually operated valves 2
I c.
Instrument root valves 2
I d.
Test connection valves 2
I e.
Vent and drain valves 2
I Auxiliary Feedwater System Auxiliary feedwater pumps 3
A Main Steam Reheat and Steam Dumo 55 System Main Steam System Valves a.
A b.
Main steam safety and relief 2
A valves c.
Pneumatically operated valves 2/3 A/I d.
Locked-closed manual valves 2
I Rev.
e.
Instrument root valves 2/3 I
f.
Test connection valves 2
I g.
Instrum>nt drain and vent 2/3 I
valves h.
Manual valves 2/3 I
- A = Active I = Inactive
TXX-6126 December 8,1986 Page 4 of 12 CPSES/FSAR TABLE 3.98-10 (Sheet I of 11)
ACTIVE VALVES Valve Identification Valve Type ANS Method or Location And Sire Safety of Isormal N_o._ _ _
System Actuator In.
Class Actuation Position
- Function, I 55 HV-2333A M5 Globe Hydraulic 32 2
Auto Trip Open Steam Line Isolation HV-2409 M5 Globe / Air 2
2 Auto Trip Open Steari Line Isolation HV-2452-1 M5 Globe / Air 4
2 Auto Trip Closed Turbine Drive AFW P g 55 Steam Suoply PV-2325 M5 Glot e/ Air 8
2 Remote Manual Closed Containment Isolation HV-2334A M5 Globe Hydraulic 32 2
Auto Trip Open Steam Line Isolation lRev.
HV-2410 M5 Globe / Air 2
2 Auto Trip Open Steam Line Isolation PV-2326 M5 Glone/ Air 8
2 Remote Manual Closed Containment Isolation HV-2335A M5 Globe Hydractic 32 2
Auto Trip Open Steam Line Isolation lN l Rev.
HV-2411 M5 Globe / Air 2
2 Auto Trip Open Steam Line Isolation PV-2321 M5 Globe / Air 8
2 Remote Manual Closed Containment Isolation HV-2336A M5 Globe Hydraulle 32 2
Auto Trip Oper.
Steam Line Isolation lI Rev.
HV-2412 M5 Globe / Air 2
2 Auto Trip Open Steam Line Isolation HV-2452-2 M5 Globe /Afr 4
2 Auto Trip Closed Turbine Driven AFW Pune Steam Supply 55 PV-2328 M5 Globe / Air 8
2 Remote Manual Closed Containment Isolation HV-2391 M5 Globe /Alr 3
2 Auto Trip Open Austliary Feedwater System Actuation HV-2398 M5 Globe / Air 3
2 Auto Trip Open Auxillary Feedwater 55 Systeen Actuation HV-2399 M5 Globe / Air 3
2 Auto Trip Open Austliary Feeduater System Actuation
TXX-6126 December 8,.1986 Page 5 o f 12 CPSES/FSAR T ABLE 6.2.4-2 (5heet I of 10)
CONTAINNENT ISOLAll0N V4LVING APPQCAil,0N Length of Pipe to Location in Type of Outermost Isolation Relation to Leakage isolation Valve Method of Actuation item Valve No.
Containment Rate fest Valve (ft)
Type /gerator Primary Secondary,
I HV-23334 Outside Note 1 40' Y - Globe / Hydr.
Auto close Remote Manual 42 N2 Actuator Rev.
2 HV-23338 Outside Note 1 Globe Manual Local N/A Manual 3
HV-2409 Outsi je 8 tote 1 Globe / Air Auto close Remote Manual 4
HV-2452-1 Outside Note 1 Globe / Air Auto open Remote Manual 5
PV-2325 Outside Note I Globe /Afr Remote Manual N/A 6
HV-2334A Outside Note 1 38' Y - Globe / Hydr.
Auto close Remote Manual N2 Actuator Globe Manual Local N/A pgy*
7 HV-23349 Outside Note 1 Manual 8
HV-2410 Outside Note 1 Glooe/ Air Auto close Remote Manual 9
PV-2326 Outside Note 1 Globe / Air Remote Manual N/A 42 10 HV-2335A Outside Note 1 40' Y - Globe / Hydr.
Auto close Remote Manual N2 Actuator 11 HV -2335B Outside Note 1 Globe Manual Local N/A Rev*
Manual 12 HV-2411 Outside Note 1 Globe / Air Auto close Remote Manual 13 PV-2321 Outside Note 1 Globe / Air Remote Manual N/A 42 14 HV-23364 Outside Note 1 38' Y - Globe / Hydr.
Auto close Remote Manual N2 Actuator l
15 HV-23368 Outside Note 1 Globe Manual Local N/A
!!anual 16 HV-2412 Outside Note 1 Globe / Air Auto close Remote Manuel 42 a
TXX-6126 December 8,1986 Page 6 of 12 CPSES/FSAR TABLE 6.2.4-3 (Sheet 1 of 14) 42 l
CONTAINfENT ISOLATION VALVING APPLICATION (Note 1)
Valve Position 34 Containment Valve Valve Isolation Post-Power Closure Power Item Signal Normal Shutdown Accident Failure Time (Sec.)
Source Remarks 1
Steam Line Opened Closed Closed Closed 5
Isolation Main Steam Isolation Bypass
- pey, 2
Closed Closed Closed Closed N/A Valve 3
Steam Line Opened Closed Closed Closed 5
t Isolation l
4 Closed Opened Opened Opened N/A l
5 Closed Closed Opened /
Closed N/A 1
Modulation
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6 Steam Line Opened closed Closed Closed 5
Isolation i
Main Steam Isolation Bypass Rev.
I 7
Closed Closed Closed Closed N/A j
Valve I
8 Steam Line Opened Closed Closed Closed 5
)'
Isolation i
9 Closed Closed Opened /
Closed N/A Modulation
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l 10 Steam Line Opened Closed Closed Closed 5
Isolation i
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CPSES/FSAR TXX-6126 TA8tE 6.2.4-3 December 8, 1986 (Sheet 2 cf 14) 42 Page 7 of 12 CONTAINENT ISOLATION VALVING APPLICATION (Note 1)
Valve Position 34 Containment Valve Valve Isolation Post-Power Closure Power i tem Signal Normal Shutdown Accident Failure Time (Sec.)
Source Remarks Main Steam Isolation Bypass 11 Closed Closed Closed Closed N/A Valve Rev.
12 Steam Line Opened Closed Closed Closed 5
Isolation 13 Closed Closed Opened /
Closed N/A Modulation 14 Steam Line Opened Closed Closed Closed 5
Isolation Main Steam Isolation Bypass 15 Closed Closed Closed Closed N/A Valve Rev.
16 Steam Line Opened Closed Closed Closed 5
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38 Isolation 17 Closed Opened Opened Closed
'N/A 18 Closed Closed Opened /
Closed N/A Modulation 19 Feedwater Opened Closed Closed Closed 5
Isolation 20 Phase A Opened Closed Closed Closed 5
l Opened Opened Opened Opened N/A 20a 42 Opened Opened Opened Opened N/A Closed Opened Closed Closed N/A 20b P
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TXX-6126 Decwber 8, 1986 Page 9 of 12 CPSES/FSAR The valves fall closed on loss of air or electric signal. Valve positions, i
i open or closed, are indicated with control board lights. Failure of the relief valves to open causes the system pressure to rise to the set point of the first safety valve, which would then open, preventing further pressurization of the system. The power-operated relief valves do not provide main steam supply system overpressure protection. This overpressure protection is l
provided entirely by the safety valve system described previously. Valves are designed to pass a total flow of 10 percent of the plant design flow at the i
pressure corresponding to steam generator no-load conditions. The maximum i
capacity of any one valve does not exceed the flow rate (specified by the steam generator manufacturer) at the design pressure of the main steam supply system in order to limit reactivity insertion caused by the negative
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temperature coefficient of the core.
The valves discharge to the atmosphere and are designed to operate over the steam pressure range of 125 to 1300 psia.
Each valve inlet pipe is provided with one manual isolation valve for maintenance.
Table 10.3-3 shows the design bases of the power-operated relief valves.
10.3.2.3 Main Steam Isolation Valves i
10.3.2.3.1 General Each main steam line is provided with a quick-acting isolation valve, and is 56 designed to stop flow from either direction after a steam line break (five sec after receiving the closing signal) to prevent uncontrolled steam release from i
more than one steam generator. The valves are installed outside the l
Containment, downstream of the safety valves, and are provided with a manual i
l 4-in. bypass valve for warming the system and equalizing the pressure across Rev.
the isolation valve. The bypass valve is locked closed during power operation. The MSIVs can be opened manually by the operator in the Control 56 f
Room without opening the bypass valve.
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TXX-6126 Dec:mber 8,1986 Page 10 of 12 CPSES/FSAR Each MSIV is provided with a two-train module, three-position control switch mounted on the main control board. The switch has an electrical two-train module so that valves can be closed even if one train fails. The three switch positions are close, auto, and open, with spring return to auto position.
Each MSIV also has a two-train module test switch to enable a valve to be closed to a 10 percent-closed position when tested.
In addition to these control board mounted switches, there is a two-train module trip switch which can be used to trip all four MSIVs simultaneously. Trip switch positions are trip and auto, with spring return to auto.
56 l The MSIV's are automatically closed on high-high containment pressure or steamline break protection logic (as indicated by high stean pressure rate or 13 QO32.79 low steamline pressure). High steam pressure rate is only effective whea steamline SI is manually blocked during startup and cooldown, and low steamline pressure is only effective when the block is removed (see Figure 7.2-1 sheet 7). The MSIV's are closed by operation of the MSIV valve actuators. The actuator is, in effect, a hydraulic cylinder coupled directly to a nitrogen-accumulator. The accumulator is designed as a chamber 20 concentric to the hydraulic cylinder, and it stores the energy required for Q212.139 closing the MSIV in the form of compressed nitrogen gas.
Because the accumulator is integral part of the cylinder, the loss of any external manifolding or system elements will not prevent the actuator from closing the valve. A hydraulic control system which maintains hydraulic fluid bolow the valve actuator piston is utilized to regulate valve closure velocity.
Extension of the actuator to close the MSIV is accomplished by an electric signal which operates two solenoid valves in the hydraulic control system portion of the actuator. These valves permit the hydraulic fluid below the actuator piston to flow into a hydraulic reservoir at a controlled rate as the compressed nitrogen extends the actuator to close the MSIV.
10.3-8
TXX-6126 D;cember 8,1986 Page 11 of 12 CPSES/FSAR Each MSIV can be tested with its own control board switch (two-train module,
- 4 two-position test, or normal with position maintained).
If the valve switch QO32.43 QO32.M is in the test position and the valve does not reach 10-percent closure after a time delay, an alarm is actuated in the Control Room. When the valve is tested, it closes slowly by energizing a test solenoid in the hydraulic circuit as well as energizing the trip-close solenoid. An automatic MSIV trip-close signal overrides the test signal and closes the yhlve quickly.
Rev.
Alarms are actuated when MSIVs have low hydraulic oil pressure or low actuator gas pressure.
Each valve has position-indication lights on the main control board for open, closed, and test positions. There are monitor lights which light on valve-closed position.
The automatically operated MSIVs serve only a safety function and are not required for power operation. They are required to limit uncontrolled flow of stea:n from the steam generators in the event of a break in the piping system.
These valves operate under the following situations:
1.
Break in the Steam Line from One Steam Generator Inside the Containment Building If the break is within the Containment, steam is discharged into the Containment. The other steam generators act to feed steam through the interconnecting header into the broken line and then into the Containment.
A steam line break results in a significant pressure rise in the l
Containment so that reverse flow protection is necessary to prevent discharge of more than one steam generator. According to calculations, reverse flow must be interrupted to limit the Containment pressure rise to 56 an amount below design pressure. To achieve this, the automatic isolating i
10.3-9
TXX-6126 December 8, 1986 Page 12 of 12 CPSES/FSAR d.
Closing Rate Test The complete valve assembly is tested to ensure that the closing time is less than five sec.
3.
Leakage The valve disc and seat materials are such that valve wear does not increase the leakage rate after a minimum of 500 cycles under normal operating conditions.
4.
Design Bases Table 10.3-4 shows the design bases of the MSIVs.
10.3.2.4 Main Steam Isolation Bvoass Valves 4
The MSIVs are provided with 4-in. bypass valves which are normally closed.
If 56 the bypass valves were open they would tend to negate the protection provided by the MSIVs. Therefore, all four bypass valves are locked closed during power operation. During startup, hot standby and hot shutdown one MSIV bypass valve may be opened provided the other three bypass valves are locked closed Rev.
and their associated MSIV's are closed.
Table 10.3-5 shows the design bases 1
for the main steam isolation bypass valves.
56 10.3.2.5 Flow Restrictors Each steam generator is provided with flow restrictors which are located inside the steam generator outlet nozzle. These restrictors (several venturis arranged in a bundle) limit the steam flow rate in the event of a steam line rupture. These restrictors also minimize the thrust force effects on the steam generator and piping system.
The design basis, description, and test and inspections are included in 13 10.3-15
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