ML20212F313
| ML20212F313 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 02/21/1987 |
| From: | Mcnutt G, Russell J, Stewart D TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20212F190 | List: |
| References | |
| 229.5(B), 229.5(B)-R01, 229.5(B)-R1, NUDOCS 8703050063 | |
| Download: ML20212F313 (13) | |
Text
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i *i TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PR03 RAM REPORT TYPE: SEQUOYAH ELEMENT REVISION NUMBER: 1 TITLE: INSTRUMENTATION AND CONTROL DESIGN Control Air System Adequacy Following Pipe Break PAGE 1 0F 12 REASON FOR REVISION:
- 1. Revised to incorporate TAS and SRP connents; and to add Section 10, Corrective Action PREPARATION PREPARED BY:
(. 0. 01&/hSIGNATURE' 5tl6l87 DATE REVIEWS 4tE -
REVIE iM E:
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// SIGNATURE s' CONCURRENCES m 9 CEG-H: . h )ffh 2- 7-fr7 SRP: 9,e N. 2 - l ~l - 87 DATE ', SIGNATURE
- DATE SIGNATURE APPROVED B -
MOsend +zi-e7 ain DATE ECSP HANAGER DATE' W AGER OF NUCLEAR POWER CONCURRENCE (FINAL REPORT ONLY)
8703050063 870226 PDR ADOCK 05000327 P PDR
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~ REPORT NUMBER:. 229.5(B)-
h~! TVA EMPLOYEE CONCERNS SPECIAL PROGRAM REVISION NUMBER: 1 f.
~PAGE 2 0F 12
- 1. CHARACTERIZATION OF ISSUES:-
, . Concern: Issue:-
IN-85-348-002 .
- a. . Volume of air receivers in control air system is insufficient to
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!~ " Control air system does not appear to have sufficient ensure that control systems will.
volume-to assure functionality function in the event of a if the system should experience guillotine air.line break.
- a guillotine air line break.
Individual specifically J
requested a description of
the maximum system volume
.available and of~ appropriate backup systems."
9 NO i 2. HAVE ISSUES BEEN IDENTIFIED IN ANOTHER SYSTEMATIC ANALYSIS? YES
-l- o . Identified by TVA SQN Review Team ,
-Date 02/11/86-s TVA memo D. C. Craven to H. L. Abercrombie, " Review of Aur111ary Control Air System," (LO4 860224'945) o ' Identified by TVA SQN Generic Concerns Task Force (GCTF)
Date 04/24/86 TVA SQN GCTF report, " Employee Concern IN-85-348-002, Design Volume of the Control Air. System in Insufficient," Rev. 1 I o Identified by TVA Division of Nuclear Engineerin t Date 12/15/86 i TVA SCR SQHMEB86121, R0, T. M. Lafferty
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- 3. DOCUMENT NOS., TAG NOS., LOCATIONS OR OTHER SPECIFIC DESCRIPTIVE IDENTIFICATIONS STATED IN ELEMENT:
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! j;. Control air system piping.
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- 1 TVA EMPLOYEE. CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PROGRAM REVISION NUMBER: 1 l
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- PAGE 3 0F 12
- 4. INTERVIEW FILES REVIEWED:
File IN-85-348 was reviewed on 11/02/86, and only the employee concern was found.
- 5. DOCLMENTS REVIEWED RELATED TO THE ELEMENT:
See Appendix A.
- 6. WHAT REGULATIONS, LICENSING COMMITMFNTS, DESIGN REQUIREMENTS OR OTHER APPLY OR CONTROL IN THIS AREA 7 j See Appendix A.
-7. LIST REQUESTS FOR INFORMATION, MEETINGS, TELEPHONE CALLS, AND OTHER DISCUSSIONS RELATED TO ELEMENT.
See f.ppendix A.
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4 t 8. EVALUATION PROCESS:
- a. Reviewed compressed air systems flow diagrams and related text in SQN Final Safety Analysis Report to determine system l
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- - functional requirements and design parameters. .
- b. Reviewed SQN design criteria documents for control air systems and for pipe break criteria.
- d. Reviewed the SQN report, identified in Section 2, relative to the issue raised in the employee concern.
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- e. Evaluated the validity of the employee concern, relative to SQN, on the basis of the review described above.
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TVA EMPLOYEE CONCERNS REPORT NUMBER:. 229.5(B) 1b7 SPECIAL PROGRAM REVISION NUMBER: 1 i'
PAGE 4 0F 12 o I
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- 9. DISCUSSION.-FINDINGS; AND CONCLUSIONS:
]i :1i- Chronology:
.I I- 06/85: TVA Nuclear Safety Review Staff. receives WBN concern 11-12/85: TVA special review team reviews.SQN control air h systems, based on the WBN concern i
I 02-05/86i TVA SQN GCTF evaluates the results of the above review and issues reports 04-05/86: Bechtel evaluates employee concern for WBN 12/15/86: TVA Significant Condition Report _SQNMEB86121 identifies.
jj omission in earlier safety analysis (NEB 810811 274) pp J4
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Discussion:
- a. - Generic Applicability WBN concern IN-85-348-002 was investigated and found to be not valid for.WBN, which has a compressed air system design similar to that for SQN. However, it was decided to
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investigate the concern for applicability to SQN. The concern does not specify a location for the " guillotine pipe
'g break" in question, so this evaluation was based on its
.I potential-occurrence in either the Station Control and l Service Air (SCSA) or the Auxiliary Control Air (ACA), inside f or outside containment. The concern also does not clearly E :
indicate whether this pipe break was considered to be an
! initiating event or to be subsequent to some other initiating event. Therefore, this evaluation considered both cases.
1 ii System Description O:
li l 4 b.
I): 'l The term " control air system" has no formal status for SQN.
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As indicated in the SQN FSAR, the overall system is referred 1
to as the Compressed Air System, which consists of two
]! subsystems, SCSA and ACA. The term " control air" may apply either to that portion of the SCSA not dedicated to service 1 '
air, or to the ACA.
The SCSA includes four motor-driven air compressors, any two i i !
of which can handle all control air requirements under normal j
plant operating conditions. The ACA consists of two
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229.5(B)
. REPORT NUMBER: !
- i ; 1 TVA EMPLOYEE CONCERNS. N t SPECIAL PROGRAM REVISION NIMBER
- - 1 !
1".
PAGE 5 0F 12 e
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0 y completely redundant sets of compressed air supply equipment 3
and associated supply piping. 'ACA' serves all safety-related 1 plant components whose active functions require control air. ,
SCSA serves certain safety-related components whose active 4 functions are not. safety-related. Therefore, the SCSA is nonsafety-related and the ACA is safety-related.
The ACA air compressors are in a standby condition during normal plant operation. The ACA receivers are normally
.y charged from the cross-connected SCSA. On indication of low '
pressure in the SCSA, the ACA compressors are automatically started, and, on further decrease in system pressure, both trains of the ACA are automatically isolated from the SCSA by control valves.
- c. Design Criteria.
Criteria applicable to pipe breaks outside containment as initiating events are defined in Design Criteria SQN-DC-V-1.1.ll (App. A, 5.e). Pipe breaks inside containment are covered in Design Criteria SQN-DC-V-2.13
( App. A, 5.d) . These documents define "high energy" piping as that which normally operates at pressure and temperature above 275 psig and 200 F. '" Low energy" piping is that which operates at either a pressure or temperature below these-i- values. These documents require that both " guillotine breaks" and " critical cracks" be assumed (separately) in high energy piping but that only " critical cracks" be assumed in low energy piping. The opening size of-a critical crack is stated to be one-half the inside pipe diameter in length and one-half the pipe wall thickness in width.
f Another criteria subject possibly related to the concern is the distinction between failures which are directly caused by the-initial break and " single failures" which must be assumed in evaluating the plant safe shutdown capability in response r
to the initial break. The criteria define the initiating L ' event as including those secondary effects which are likely to occur as a direct consequence of the initial pipe break.
'. These may include various failure modes of piping in the vicinity of the initiating pipe break location. A9 additional component failure referred to as the " single failure" must be assumed in those systems utilized in accomplishing safe shutdown in response to the initiating
, -j, event.
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TVA EMPLOYEE CONCERNS REPORT NUMBER: -229.5(8).
-SPECIAL PROGRAM REVISION NUMBER: 1 PAGE 6 0F 12 m
All of the' foregoing criteria are consistent with NRC requirements applicable to plants contemporaneous with-SQN
.^
(App. A, 5.j)
.i d. Analysis L
As indicated in paragraph 9.a,. pipe breaks can be either
)!' initiating or subsequent events. Also, as indicated in i
paragraph 9.c, there is a subset of initiating events which 1 '
includes those events likely to occur as a direct result of' the initiating events, such as an additional failure of a nearby pipe. _These variations are covered in the following paragraphs.
(1) Pipe break as an initiating event For the majority of the SCSA and ACA piping the design pressure is 105 psig and the design temperature.is 100*F.
The only exception to these values is in the air compressor 3 discharge lines up to their air coolers,lfor which the I-maximum design temperature is 260'F. The ACA compressor discharge lines are not pressurized during normal plant operation, and they fall into a category that the criteria documents exempt from the "high energy" definition and classifies as " low energy." Therefore, the only control air piping falling under the "high energy" definition, and thus
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requiring guillotine pipe break assumptions, is the SCSA compressor discharge line up to the aftercoolers. No guillotine breaks need be assumed in the safety-related ACA.
A guillotine break in a SCSA compressor discharge line will not cause loss of system function as each of the compressors are separated from the main system headers by check valves.
The occurrence of a critical crack anywhere in the normally pressurized portions of SCSA and ACA would be unlikely to cause a loss of system function because of the size and quantity of SCSA compressors. The FSAR (App. A, 5.c) in
_ Table 9.3.1-1 lists the SCSA capacity as 2440 scfm. The
-criteria do not require an assumption of loss of offsite power for such events (with subsequent loss of all SCSA compressors) as this assumption is required only if the
/ initiating event is likely to be the direct cause of the loss
/ of offsite power. If the critical crack were to occur in one of the ACA. trains and all SCSA compressors were to be lost, the redundant, sep'a7ated ACA train would be available to
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' :TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)-
t 1I SPECIAL PROGRAM
' REVISION NUMBER: 1 PAGE 7 0F.12.
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- . support plant shutdown. Still further, as stated in'the SQN
' FSAR, paragraph 9.3.1.3.2, " plant design is such that even.
total loss of all air.will not prevent safe shutdown of both units - assuming no primary or secondary side pipe' breaks."
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! (2)' Pipe break as a subsequent event j Another possible interpretation of the employee concern is that it relates to a control air failure subsequent to some i
other~ initiating event. This type of failure would i
constitute.a " single failure" as defined by the NRC in 4
i 10CFR50, Appendix A (App. A, 5.g). Design Criteria No.
i SQN-DC-V-2.16 (App. A, 5.f) covers the same subject in j greater detail. A pipe break wou k constitute a." passive"
- failure. Passive failures are not. defined in the SQN design j
criteria, but current industry practice, as documented in the l -
Single' Failure Criteria' standard ANSI /ANS-58.9 (App. A, 5.1),
is to consider only credible failures such as seal or gasket l
leakage.in piping systems. Furthermore, SQN criteria do not
- ; require consideration of passive failures within the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following an accident. After this period, active function of components served by ACA should not be required.
' However, even if it were required, component functionality is l
assured through use of the redundant ACA train.
I (3) Pipe break caused by the initiating event t
! As indicated previously, the direct consequences of a pipe break event must be considered a part of the initiating event. In 1981 TVA reviewed the likely direct consequences of pipe breaks inside containment from such effects as pipe whip and jet impingement. This review indicated that E ! portions of the ACA piping inside containment were routed too i
close to high energy piping. A review of these potential
- interactions was documented in calculation number NEB
' f 810811274 ( App. A, 5.k). The review concluded that the
' interactions were acceptable, based on the fact that the ACA l ' services lost within containment were not required to l
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accomplish safe shutdown following those particular pipe breaks. However, this analysis did not account for the overall effects of the ACA piping failure on the availability 4
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i of ACA when considering a single failure in the unaffected train of ACA. These effects were not identified until late i
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REPORT NUMBER: ' 229.5(B)
TVA EMPLOYEE. CONCERNS SPECIAL PROGRAM REVISION NUMBER: 1 PAGE 8 0F 12 in.1986,' documented in SCR SQNMEB86121 ('A)p. A, 5.1). A
.recent calculation (App. A, 5.m) showed t1at the affected ACA train cannot be isolated prior to the occurrence of unacceptable' pressure loss in the system. A single failure in the unaffected train would then result in loss of system function, possibly preventing safe shutdown.
e . .. TVA System Review for SQN TVA reviewed the SQN ACA subsystem, as-indicated-in Section 2 of this report, during the period from November 27 to
' December 20,-1985. Seven Discrepancy Reports
,(SQ-DR-86-02-017R through -022R and -032R) were issued as a l result of this review'and dealt with such subjects as maintenance and testing records._ None of these related to the subject matter of the. concern.- The review report.
concluded that "the ACA System has been designed, maintained, and tested such that it can perform its~ fntended safety function; that is to supply air to vital equipment under all conditions."~ This conclusion remains valid with the exception of the finding of-the SCR identified in paragraph d.(3).
Findings:
- a. - There is sufficient capacity, redundancy and isolation l provision in the SQN control air systems to support systems required for safe shutdown for all design basis events originating within the ACA. No guillotine' break assumptions
' are required in the safety-related ACA subsystem. However, TVA's review of high energy pipe breaks has identified a F number of unacceptable interactions which could cause loss of ACA function in the event of a single failure in the
- i. unaffected ACA train.
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Conclusions:
IN-85-348-002 is not valid since a guillotine break in the ACA l subsystem is not a design basis event. However, the physical separation of ACA piping from high energy piping within containment is inadequate to assure safe shutdown capability if breaks occur in certain locations.
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t TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PROGRAM REVISION NUMBER: 1 PAGE 9 0F 12
- 10. CORRECTIVE ACTION:
-Problem:
Portions of the Auxiliary Control Air (ACA) subsystem piping within containment are-not adequately separated from high energy piping.
Certain breaks would be likely to result in failure of ACA piping, which, in combination with a single failure in the unaffected ACA train, could result in loss of ACA function. This function is required for safe shutdown following these pipe breaks. The specific cause of loss of ACA function in the affected train would be excessive pressure loss in the train prior to automatic isolation of the portion of ACA piping inside containment.
Corrective Action Plan:
The planned corrective action, forwarded by TCAB-069 (App. A, 5.n),
consists of the following items:
- a. installationofaflowlimitingorificeineachACAheader between the containment isolation valve and the containment penetration,
- b. Incriasing the setpoint for the pressure switch which detects
" low header pressure," which provides for containment isolation valve closure.
- c. If required in addition to the above, decreasing the allowable containment isolation valve closure time.
The source of the specific revised design details, including orifice diameter, pressure switch setting and isolation valve closure time will be revised calculation 844 861208 011 (App. A, 5.m).
Concurrence:
The evaluation team concurs that satisfactory implementation of the corrective action will resolve the problems.
0708D (02/06/87)
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' TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL. PROGRAM REVISION NUMBER: 1 PAGE 10 0F 12 APPENDIX A
- 5. DOCUMENTS REVIEWED RELATED TO THE ELEMENT:
- a. WBN Element Review Sheets, Element No. 229.5, Rev. O, (05/02/86)
- b. SQN GCTF Investigation Report GOR-ll-ll, on EC IN-85-348-002,
" Design Volume of the Control Air Is Insufficient," (05/07/86)
- d. SQN Design Criteria SQN-DC-V-2.13, " Evaluating the Effects of Pipe Failure Inside Containment," R4, (ESB840913205),
(09/04/84)
- e. SQN Design Criteria SQN-DC-V-1.1.ll, " Evaluating the Effects of Pipe Failure Outside Containment," R4, (ESB 840913 202),
(09/12/84)
- f. SQN Design Criteria SQN-DC-V-2.16, " Single Failure Criteria for Fluid and Electrical Safety Related Systems," R0, (805 860721 500),- (07/14/86)
- g. 10 CFR 50, " Licensing Production and Utilization Facilities,"
Appendix A, " General Design Criteria for Nuclear Power Plants"
- h. SQN Design Criteria SQN-DC-V-32.0, " Auxiliary Control Air System," (B05 860721 522), (07/11/86)
- 1. ANSI /ANS Standard 58.9-1981, " Single Failure Criteria for Light Water Reactor Safety-Related Fluid Systems"
- j. AEC generic letter to applicants et al, from J. F. O' Leary, concerning postulated piping failures outside containment, (07/12/73)
- k. TVA Calculation " Safety Evaluation on Inadequate Separation of High Energy Lines and Essential Air Headers Inside Containment," (NEB 810811274), R1, (08/11/81)
- n. G. R. McNutt to G. L. Parkinson, CAP for Element Report 229.05, TCAB-069, (01/26/87), R1, TCAB-071 (02/06/87) 07080 (02/06/87)
r i-TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PROGRAM
- REVISION NUMBER
- ~ l PAGE 11 0F 12
- 6. WHAT REGULATIONS, LICENSING COMMITMENTS, DESIGN REQUIREMENTS OR OTHER APPLY OR CONTROL IN THIS AREA 7
- c. SQN Design Criteria SQN-DC-V-1.1.11 (5.e above)
- d. SQN Design Criteria SQN-DC-V-2.16 (5.f above)
- e. SQN Design Criteria SQN-DC-V-32.0 (5.h above)
- 7. LIST REQUESTS FOR INFORMATION, MEETINGS, TELEPHONE CALLS, AND OTHER DISCUSSIDMS RELATED TO ELEMENT.
- a. RFI SQN-724 (11/18/86) i i
0708D (02/06/87)
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TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PROGRAM !
REVISION NUMBER: 1 PAGE 12 0F 12 CATD LIST The following CATD identifies and provides corrective action for the findings included in this report:
229 05 SQN 01 (01/23/87; CAP revised 02/06/87) 07080 (02/06/87)
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REFEREllCE - ECPS120J-ECPS121C TEllNESSEE VALLEY AUTHORITY PAGE' -
115 FREQUENCY - REQUEST OFFICE CF HUCLEAR PDHER RUN TIME -. 12:57:19
) ONP - ISSS - RHM EMPLOYEE C0tICERN PROGRAM SYSTEM (ECPS) RUN DATE - 12/02/86 O-LIST OF EMPLOYEE CONCERN It4 FORMATION CATEGORY EN DES PROCESS & OUTPUT SUBCATEGORY: 22905 CONTROL AIR SYSTEM ADEQUACY FOLLOHING PIPE BREAK I S H
GE!!ERIC APPL QTC/NSRS P KEYHORD'A )
KEYWORD B CONCERN SUB R PLT BBSH INVESTIGATION S CONCERN KEYHORD C HUMBER CAT CAT D LOC FLQB REPORT R DESCRIPTION KEYNORD D ..
SN 348-002 EN 22905 N HBN NNYY SR CONTROL AIR SYSTEM DOES NOT APPEAR T -DESIGN PROCESS T50023 K-FORM 0 HAVE SUFFICIEtiT VOLUME TO ASSURE F- SPECIFICATIONS UNCTIONALITY IF THE SYSTEM SHOULD EX HVAC
) PERIENCE A GUILLOTINE AIR LINE BREAK EQUIPMENT- C; '
. INDIVIDUAL SPECIFICALLY REQUESTED A DESCRIPTION OF THE MAXIMUM SYSTEM VOLUME AVAILABLE AND OF APPROPRIATE 3 BACKUP SYSTEMS, CONCERN APPLIES TO O UNITS 1&2 g 1 CONCERNS FOR CATEGORY EN SUBCATEGORY 22905
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