ML20234E895
| ML20234E895 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 09/16/1987 |
| From: | Brown W, Huff G TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20234E875 | List: |
| References | |
| 229.5(B), 229.5(B)-R02, 229.5(B)-R2, NUDOCS 8709220556 | |
| Download: ML20234E895 (12) | |
Text
' i
{;, .
TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PROGRAM 2 I REPORT TYPE: SEQUOYAH ELEMENT REVISION NUMBER:
l 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 coments; and to add Section 10, Corrective Action
- 2. Revised to incorporate TAS comments and revise Section 10, Corrective Action.
PREPARATION PREPARED BY:
644 d 6td( SIGNATURE W4'r 7 DATE REVIEWS 0 N'O i 00
~DATE
@Gt(ATURE~ " ~
~4 LAN -
g ~ SIGNATURE (M/
w Arr
/ DATE CONCURRENCE 5 Y $ $
n // , CEG-H: A NWD ~ 9-7J7 k l'\ l{} SRP:$' ,//0rfs VWK?
DATE' v v 5.[GNATURE ,
} ' 'DATE f " ~SIGNAlu f [ ~
APPROVED BY n l\tA
~ ECSP Mf4AGER" " E alt MANAGER OF NUCLEAR POWER DATE CONCURRENCE (FINAL REPORT ONLY)
8709220556 870917 PDR ADOCK 05000327 P PDR
1 n -',;..
V '.*
TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B) 1 SPECIAL PROGRAM REVISION NUMBER: 2 4 PAGE 2 0F'12
.)
w
- 1. CHARACTERIZATION OF ISSUES:
Concern: Issue: _)
i' IN-85-348-002 a. -Volume of air receivers in control
" Control air system does'not air system is insufficient to '
appear to have sufficient. ensure that control systems will volume to as.sure functionality function in the. event of a if the system should' experience guillotine air line break.
a guillotine air line break.
Individual specifically requested.a description of ;
the maximum system volume ;
available and of appropriate backup systems." l
- 2. HAVE ISSUES BEEN IDENTIFIED IN ANOTHER SYSTEMATIC ANALYSIS? YES X N0 o Identified by TVA SQN Review Tea _m
.Date~ 02/11/86 TVA memo D. C. Craven to H. L. Abercrombie, " Review of
. Auxiliary Control Air System," (LO4 860224 945) o Identified by TVA SQN Ceneric 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 is Insufficient," Rev. 1 o Identified by TVA Division of Nuclear Engineering Date 12/15/86 TVA SCR SQNMEB86121, R0, T. M. Lafferty
- 3. DOCUMENT N05., TAG NOS., LOCATIONS OR OTHER SPECIFIC DESCRIPTIVE IDENTIFICATIONS STATED IN ELEMENT:
Control air system piping.
i 0708D-1 (09/01/87)
C_-___-_--------__ , __ __ _ , . , _ , _ _ .,_ mm ,,
, 1 j',. ':. . j REPORT NUMBER: ' --229.5(B)
TVA EMPLOYEE' CONCERNS SPECIAL PROGRAM >
s REVISION NUMBER: 2 l PAGE 3 0F 12 t !
4 INTERVIEW FILES REVIEWED:
File IN-85-348 was reviewed on 11/02/86, and only the employee concern was found.
- 5. DOCUMENTS REVIEWED RELATED TO THE ELEMENT: 1 e
See Appendix A.
- 6. WHAT REGULATIONS, LICENSING COMMITMENTS, DESIGN REQUIREMENTS OR OTHER' APPLY OR CONTROL IN THIS AREA? j See Appendix A. l
- 7. LIST REQUESTS FOR INFORMATION, MEETINGS, TELEP00 ( CALLS, AND OTHER DISCUSSIONS RELATED TO ELEMENT.
See Appendix A, i
- 8. EVALUATION PROCESS:
- a. Reviewed compressed air systems flow diagrams and related.
text in-SQN Final Safety Analysis Report to determine system functional requirements and design parameters. l
- b. Reviewed SQN design criteria documents for control air systems and_for pipe break criteria.
l
- d. Reviewed the SQN report, identified.in Section 2, relative to the issue raised in the employee concern. j
- e. Evaluated the validity of the employee concern, relative to SQN, on the basis of the review described above.
i l
l 07080-1 <
(09/01/87) l l
_ _ _ _ _ _ _ _ _ _ . . . .e , , .- , . , wa. ,. t #. :w in. s - e
TVA EMPLOYEE CONCERNS REPORT NUMBERt 229.5(B)
SPECIAL PROGRAM REVISION NUMBER: 2-PAGE 4 0F 12
. c
- 9. DISCUSSION, FINDINGS, AND CONCLUSIONS:
Chronology:
06/85: TVA Nuclear Safety Review. Staff receives WBN concern 11-12/85: TVA special review team reviews SQN control air systems, based on the WBN concern 02-05/86: 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 Repnrt SQNMEB86121 identifies omission in earlier safety analysis (NEB 810811 274)
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 investigate the concern for applicability to SQN. The concern does .10t specify a location for the " guillotine pipe break" in question, so this evaluation was based on its potential occurrence in either the Station Control and Service Air (SCSA) or the Auxiliary Control Air (ACA), inside or outside containment. The concern also does not clearly 1 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,
- b. System Description The term " control air system" has no formal status for SQN.
As indicated in the SQN F3AR, the overall system is referred 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 air, or to the ACA.
07080-1 (09/01/87) p
_------_ - _ . .- s . .. m ._ . m .
c- ,
h-TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PROGRAM '
REVISION NUMBER: 2 l PAGE 5 0F 12 l
l l~
The SCSA includes five motor-driven air compressors, any two of which can handle all control air requirements under normal plant operating conditions. The ACA consists of two completely redundant sets of compressed air supply equipment and associated supply piping. ACA serves all safety-related plant components whose active functions require control air.
SCSA serves certain safety-related components whose active j functions are not safety-related. Therefore, the SCSA is nnnsafety-related and the ACA is safety-related.
The ACA air compressors are in a standby condition during l normal plant operation. The ACA receivers are normally 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-1.1.11 (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 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 i' stated to be one-half the inside pipe diameter in length and one-half the pipe wall thickness in width.
Another criteria subject possibly related to the concern is the distinction between f ailures which are directly caused by the initial break and " single f ailures" which must be assumed in evaluating the plant safe shutdown capability in response to the initial break. The criteria define the initiating event as including those secondary effects which are likely to occur as a direct consequence of the initial pipe break.
These may include various f ailure modes of pioing in the vicinity of the initiating pipe break location. An 07080-2 (09/01/87)
- - - - _ - - _ - _ _ _ _ . _ . _ - -- _ x. .m, s .c ,
TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PROGRAM REVISION NUMBER: 2 PAGE 6 0F 12 I
e 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 event.
All of the foregoing criteria are consistent with NRC requirements applicable to plants contemporaneous with SQN (App. A, 5.j)
- d. Analysis As indicated in paragraph 9.a pipe breaks can be either initiating or subsequent events. Also, as indicated in paragraph 9.c, there is a subset of initiating events which includes those events likely to occur as a direct result of the initiating events, such as an additional f ailure of a nearby pipe. These variations are covered in the following i
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 discharge lines t;p to their air coolers, for which the maximum design temperature is 260 F. The ACA compressor discharge lines are not pressurized during normal plant operation, and they f all into a category that the criteria documents exempt from the "high energy" definition and classifies as " low energy." Therefore, the only control air l
piping falling under the "high energy" definition, and thus 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, F;.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
( -
f 07080-1 (09/01/87)
= . , . , . .
TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PROGRAM REVISION NUMBER: 2 PAGE 7 0F 12 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, separated ACA train would be available to 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."
(2) Pipe break as a subsequent event Another possible interpretation of the employee concern is that it relates to a control air f ailure subsequent to some other initiating event. This type of failure would constitute a " single f ailure" as defined by the NRC in 10CFR50, Appendix A (App. A, 5.g). Design Criteria No.
SQN-DC-V-2.16 (App. A, 5.f) covers the same subject in greater detail. A pipe break would constitute a " passive" failure. Passive failures are not defined in the SQN design criteria, but current industry practice, as documented in the Single Failure Criteria standard ANSI /ANS-58.9 ( App. A, 5.1),
a i is to consider only credible failures such as seal or gasket
'- 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 assured through use of the redundant ACA train.
(3) Pipe break caused by the initiating event As indicated previously, the direct consequences of a pipe break event must be considered a part of the initiating event. As a result of field evaluations to assess compliance with separation criteria, six nonconformance reports (NCRs) were issued in 1981 identifying inadequate separation of high energy lines and the essential (ACA) headers both inside and outside containment. Interactions noted in locations outside containment were subsequently found to be acceptable. A review of these potential interactions was documented in calculation number NEB 810811274, R1 (App. A, 5.k). The review concluded that the interactions were acceptable, based on the fact that the ACA services lost within containment were not required to accomplish safe shutdown following those 3
07080-1 (09/01/87)
_ _ ~~ ^ L- _
g
f.'.
TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PROGRAM REVISION NUMBER: 2 PAGE 8 0F 12 particular pipe breaks. However, this analysis did not account for the overall effects of the ACA piping failure on the availability of ACA when considering a single failure in the unaffected train of ACA. These effects were not identified until late in 1986, and documented in SCR SQNMEB86121 (App. A, 5.1) uhich, during preparation of essential calculations (App. A, 5.m), showed that 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.
In 07/87, additional unacceptable ACA system /high energy pipe break interactions, outside primary containment, were identified as a result of an NRC inspection. TVA, in the corrective action plan closure for this element report ,
(App. A, 5.p), has committed to keep the SCR listed in the preceding paragraph open to address this issue,
- e. TVA System Review for SQN TVA reviewed the SQN ACA subsystem, as indicated in Section 2 of this report, during the period from 11/27/85 to 12/20/85.
Seven discrepancy reports (SQ-0R-86-02-017R through -022R and
-032R) were issued as a result of this review and dealt with such subjects as maintenance and testing records. None of these related to the subject of the concern. The review report concluded that "the ACA System has been designed, maintained, and tested such that it can perform its intended 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 paragraphd.(3).
Findings:
- a. There is sufficient capacity, redundancy, and isolation 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 and NRC's reviews of high energy pipe breaks have identified a number of unacceptable interactions which could cause loss of ACA function in the event of a single failure in the unaffected ACA train.
s 07080-2 (09/01/87)
L*? TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)'
SPECIAL PROGRAM REVISION NUMBER: 2
.PAGE 9 0F 12
Conclusions:
IN-85-348-002, as expressed, is not technically valid since a guillotine break in the ACA subsystem is not a design basis event.
However,'as a peripheral issue, the evaluation team found that the physical separation of ACA piping from high energy. piping within containment is inadequate tu assure safe shutdown capability if
- i. breaks occur in certain locetions. Similar problems that have been raised recently concerning piping outside containment will be addressed by TVA's normal procedures for handling conditions adverse to quality. Resolution of these additional problems !
transcends the scope of this evaluation and is, therefore, not included in the corrective action plan of this report.
- 10. CORRECTIVE ACTION:
Problem:
Portions of the ACA subsystem piping within containment are not adequately' separated from high energy piping. Certain breaks would' be likely to result in.f ailure of ACA piping, which, in combination with a single failure in the unaffected ACA train, could result in s'
loss of ACA function. This function is required for safe shutdown following these pipe breaks. However, only one unacceptable interaction between high energy piping and ACA piping was found through recent TVA systems analyses. This interaction involved the 4-inch pressurizer spray line.
Corrective Action Plan:
The corrective action plan, forwarded by TCAB-101 (App. A, 5.n),
consists of analysis which limits physical changes to the installation of an isolation plate on the train A 1-inch ACA line just upstream of the potential interactions with the 4-inch pressurizer spray line.
Concurrence:
The evaluation team concurred that satisfactory implementation of the corrective action would resolve the specific problem outlined within the scope of this evaluation. This corrective action for the problem described in CATD 229 05 SQN 01 has been completed, per the CAP closure (App. A, 5.p).
07080-2 (09/01/87) x w..x v wm-o y , g
$$.; q
- - TVA EMPLOYEE CONCERNS- REPORT NUMBER: 229.5(B) .
SPECIAL PROGRAM REVISION NUMBER:' 2-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-11-11, 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-1.1.11, " 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 l
t- i- for Fluid and Electrical Safety Related Systems," R0, L (805 860721 500), (07/14/86) 9 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," (805 860721 522), (07/11/86)
- 1. ANSI /ANS Standard 58.9-1981, " Single Failure Criteria for 1 Light Water Reactor Safety-Related Fluid Systems" l
l j. AEC generic letter to applicants et al, from J. F. O' Leary, concerning postulated piping f ailures outside containment, (07/12/73) q l k. TVA Calculation " Safety Evaluation on Inadequate Separation !
Lines and Essential Air Headers Inside of High Energy (NEB 810811274), R1, (08/11/81)
Containment,"
- m. TVACalculation"ACAHeaderPressure,"(844861208011),R0, (12/08/86) f 07080-1 (09/01/87)
4
- b. .
ir
^
TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PROGRAM REVISION NUMBER:' 2 PAGE 11 0F 12 APPENDIX A (cont'd) )
- 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), and l R3, TCAB-101 (08/27/87)
- o. G. R. McNutt to G. L. Parkinson, Completion of Corrective Action for Element Report 229.05, TCCA-028, (08/21/87)
- 6. . WHAT REGULATIONS, LICENSING COMMITMENTS, DESIGN REQUIREMENTS OR OTHER APPLY OR CONTROL IN THIS AREA? ,
4
- c. SQN Design Criteria SQN-DC-V-1.1.ll (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 DISCUSSIONS RELATED TO ELEMENT.
- a. RFI SQN-724 (11/18/86) 1 07080-1 (09/01/87)
,s,., . ...
' TVA EMPLOYEE CONCERNS REPORT NUMBER: 229.5(B)
SPECIAL PROGRAM REVISION NUMBER:. 2 I
PAGE 12 0F 12 l
CATD LIST _
The following CATO identifies and provides corrective action for the findings included in this report:
229 05 SQN 01 (01/23/87; CAP revised 02/06/87 and 07/27/87) f f
l j
l I
07080-1 (09/01/87) )
. - _ _ _ _ _ .-_ .