ML20082G546
| ML20082G546 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 11/28/1983 |
| From: | Schroeder C COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0578, RTR-NUREG-0737, RTR-NUREG-578, RTR-NUREG-737, TASK-2.E.4.2, TASK-TM 7676N, IEB-80-06, IEB-80-6, NUDOCS 8311300239 | |
| Download: ML20082G546 (8) | |
Text
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- D Commonwealth Edison
" ~
_ ( O )} Address Reply to: Post Othee Box 767 One First Nationit Plara. Chictgo. Ilhnors
,(j Chicago, Illinois 60690 November 28, 1983 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
LaSalle County Station Units 1 and 2 Primary Containment Isolation Following Reset of Isolation Signal NRC Docket Nos. 50-373 and 50-374 References (a):
July 25, 1979 letter from D. B. Vassallo to Cordell Reed, "TMI Lessons Learned Task Force Report", NUREG-0578, includes Item 2.1.4.
(b):
September 27, 1979 letter from D. B. Vassallo to All Applicants for pending OL's.
(c):
October 31, 1979 letter from D. G. Eisenhut to All Plants, distributing NUREG-0737 which includes Item II.E.4.2 formerly Item 2.1.4
-(0578).
(d):
November 9, 1979 letter _from D.
B. Vassallo to All Applicants for pending OL's.
(e):
March 13, 1980 IE Bulletin 80-06, Effect of Resetting ESF Actuation Signals on Primary Containment Integrity.
(f):
April 15, 1980 letter from D.
L. Peoples to D. G. Eisenhut, submitting LaSalle-NT0L Action Plan for Response to NUREG-0578 Positions.
(g):
December 9, 1980 NRC Issued Question 031.285 on the Initiation, Overriding, Bypassing and/or Resetting of Circuits for Primary Containment Ventilation Systems.
(h):
January 29, 1981 Edison submitted FSAR Amendment 54 Which Included Response to QO31.285.
(Later Revision In December 1981 adds information on Exceptions.)
(1):
May 19, 1981 Edison submitted FSAR Amendment 56 with Appendix L that documents the TMI responses to NUREG-0737, including L.29 addressed to Item
.II.E.4.2.
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MODI 8311300239 831128 l O PDR ADOCK 05000373 P
H. R.-Denton November 28, 1383 (j):
November 8, 1983 NRR informal request for Additional information related to Region III Inspection Report 50-373/83-46(DE).
(k):
November 15, 1983 letter f rom C. W. Sch roeder to H. R._Denton provided justification for not modifying certain valves that could be repositioned upon reset of containment isolation logic.
(1):
November 22, 1983 Edison-Region III Management Meeting to discuss Unresolved Item 374/83-29-02(DE)
No. 8 related to References (a) through (j) above.
Daar Mr. Denton:
NRC guidance in References (a), (b), and (d) was followed in Edison's submittal of the LaSalle. NT0L Action Plan via Reference (f) which addressed the four positions:
1.
diverse containment isolation signals, 2.
identification of essential and non-essential systems with a tabulation of valves on containment penetration lines which were under evaluation per the guidance; and a statement of the general basis for an essential system as pertains to containment isolation, 3.
use of automatic isolation signals (electrical) or check valves and locked-normally-closed manual valves (mechanical) on non-essential containment isolation lines, and 4.
that resetting of containment isolation logic does not result in loss of primary containment isolation through automatic reopening of non-essential lines.
Although not required to respond directly to IE Bulletin 80-06, Reference (e) for LaSalle which at that time was a pending NT0L plant, Edison performed the requested review (for LaSalle) of the potential for compromising primary containment integrity whenever ESF actuation signals were reset.
As a result of that evaluation, engineering modifications were designed for control circuitry for the following systems:
Reactor Building Equipment Drains and Floor Drains (RE and RF),
Standby Gas Treatment System (VG)
Primary Containment Monitoring System (CM)
Reactor Building HVAC System (VR)
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-H.?R. Denton November 28, 1983
- Other valves were. determined to not be affected by ESF signal i
reset, to not have ESF actuated isolation signals, or to have roles and
--features that exempted them f rom Containment integrity considerations as
. unique and trivial cases.
In no instance did ESF signal. reset invalidate the' emergency. safety function being ' performed by the safety-related ESF system.
By Reference-(g), NRR requested additional information via
- QO31.285 on the isolation.of containment ventilation / purge valves based upon positions derived from observations at Millstone 2, Salem 1, and North Anna 1 'which were described in the question consisting of five a
specificEsubparts on containment ventilation isclation.
A sixth subpart idealt with the overriding,or resetting' of the ESF actuation signal and the possibility of any equipment to change position.
Edison's initial response was submitted as part of FSAR Amendment 54, dated January 29, 1981. f That response addressed the specific subparts related to containment ventilation isolations and provided a list of forty-seven
. ventilation dampers and six containment monitoring i nstruments, and two i
feedwater check valves that changed position with ESF reset, hence needed modification to ensure an integral containment barrier as well as an 4
' effective ESF configuration.
This response was defined concurrently with l
+
the evaluation review of =IE Bulletin 80-06 which had identified systems, other than containment ventilation systems, that also required i-modification for these-same reasons.
These design efforts for. the containment signal modification i
packages were underway whether focused f rom the NT0L Action Plan (Reference f), the ~ IE Bulletin 80-06 (Reference e), NRR Question 031.285 1
.(Reference g), or for compliance _to Item II.F.4.2 of NUREG 0737 (Reference c).'
Edison's response to NUREG 0737 (Reference c) was docketed as Appendix L to the LaSalle FSAR via Amendment 56 on May 19, i
1981.
.It provided the general response to Item II.E.4.2 according to -the L
q seven (7) NRC criteria:
1.-
Diversity in parameters sensed for initiation of containment 4
i isolation to comply with SRP 6.2.4.
LaSalle conforms, primary containment isolation signals are given in FSAR Table 6.2-21.
2.
Definition of essential and non-essential systems for
- purposes of isolation.are identified in FSAR Table 6.2-21, with the basis
- for essential systems being those that may be needed within 10 minutes of j
a LOCA,~a normal. reactor scram, or a reactor scrim system failure.
3.
Non-essential systems that provide a possible open path out of primary. containment are either isolated by isolation signale, by check valves that prevent outflow or by locked, normally closed manual valves.
2 Instrument lines have closed piping systems.
Containment penetrating instrument lines of small diameter use excess-flow check valves (Reg.
s
- Guide 1.11) for non-essential equipment.
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R~. Denton' November 28, 1983 v
4.
Initial response on resetting of containment isolation-signals =do not result in automatic loss of containment isolation cited j
-those needing modification.
Subsequent FSAR updates to Table 6.2-21 have refined and augmented the list of design changes to containment isolation afaatures as a' result of reviews:and evaluations and enumerated at the beginning of this paragraph, and from pre-operational test.results.
FSAR updates were made via Amendments 54 and 56 previously cited and Amendments 57'(July, 1981), 59 (December, 1981), 60 (March, 1982), 61 1.
- (December, 1982) and 63 (July, 1983) to-record the corrective actions resulting from design modifications to conform to NUREG 0737 Item
-II.E.4.2 requirements.
5.
From historical experience with similar BWR and Quad Cities) the minimum drywell pressure set point (plants (Dresden1.69 psig), with i
an allowable value of 1.89 psig, is compatible with expected normal operating conditions.
{
6.
The containment vent and purge valves are physically constrained to a 500 maximum opening.
This issue is addressed i
specifically in SER, SSER and remains a requirement for LaSalle.
Operation of these valves during power modes for the purpose of inerting-O and deinerting the containment is limited by Technical Specifications.
-7.
Vent and purge valves downstream of the SGTS are closed manually upon receipt of high radiation signals from the station vent stack.
Several diverse methods for the detection of primary coolant boundary leakage inside containment already exist:
drain sump level for liquid effluent monitoring and plant' atmosphere radiation monitoring to augment the automatic isolation capability already provided tur diverse signals for line breaks, namely containment pressure and local temperature monitors.
The NUREG 0737 summary review included the previously completed efforts on containment isolation integrity following-reset of signal i
logic.
Specifically-covered were those valves identified in the LSCS-NT0L Action Plan (Ref. f), those dampers and valves reported in the response to Q.031.285 (Ref. h), and those valves (linas) included in the systems inodifications identified via the IE Bulletin 80-06 exercise.
Certain testable check valves, warming valves, and RCIC steam supply valves were included in this review on lines which penetrate primary contaiment, however, the NUREG 0737 write-up did not require
. justification for these exceptions.
Subsequent to the Appendix L submittal for NUREG 0737, FSAR Table 6.2-21 was revised to acknowledge the revisions to logics where the design was changed to preclude automatic valve opening upon signal reset.
Affected systems were as follows:
4 i
~ _. _ -. _ _ _.. _. _ -. _,.. -., _. _ -.. _ _ _.. -, _ -. _ _ _ _. _ _ _ _ _,. - - _.. _ _ _.
1F. : R. Denton
-.5-November 28, 1983 Reactor. Building Equipment Drains (RE)
Reactor.3uilding Floor Drains (RF)
Containment Monitoring Instrument Lines (CM)
Reactor Building Ventilation System (VR)
Control Room Ventilation System (VC) 4 Standby-Gas' Treatment System (VG).
Also, acknowledged was the addition of valves on the hydraulic lines for control of the reactor recirculation system.
The FSAR provided the affirmative write-up for the containment isolation valves, however, the negative, inapplicable or exceptional situations were not conventionally included in the FSAR, nor are they required to be included.
Inasmuch. as Item 6 of Q.031.285 requested justification of
" design departures for which not corrective action is planned," a revision to this response'was submitted via Amendment 59 (December, 1981) to include the reason for not modifying the Feedwater Inlet Check Valves, B21-F032A,B.
(Note that footnote 17 to FSAR Table 6.2-21 had previously covered this point).
t As part of the ESF systems preoperational tests, the LSCS staff I
authenticated th at necessary isolation valve line ups were automatically
. accomplished to validate propsr operation of the ESF loops / systems.
Additionally, containment leakage testing corroborated the proper positions for certain pressure equalization valves used only during leak
-rate testing.
These valves are also exceptions to the "no repositioning on~ containment isolation reset" because of their unique function.
None requires modification for the reasons listed below:
1.
Test Equalization Valves:
E21-F333, E22-F354, E51-F354, E51-F355.
These valves are closed during normal plant operation and a.
function only when manually initiated to equalize pressure across the testable check valve during leakage tests; their position is indicated in the control room.
b.
These valves are on 3/4 inch lines and are employed during a trivial-time fraction of a year ( 10-6); an instrument line break of this size has acceptable results
. (FSAR Chapter 15) per 10CFR100 guidance.
c.
These valves each have an upstream isolation valve that must be in a closed position (mandatory) to establist reactor coolant pressure boundary integrity during leak tests when they are opened.
d.
A containment isolation signal to prevent opening in event of a LOCA or to close them should a LOCA occur while open during leak testing is provided for each of these valves.
H. R. Denton November 28, 1983 e.
None of these valves is required to operate during ESF injection.
f.
None can contribute to an offsite radiation exposure unless a LOCA is accompanied with two additional failures of ESF components.
2.
Warming Valves:
Ele-F099A and B for the RHR Shutdown Cooling Line.
Each RHR shutdowr6 cooling line is prewarmed to prevent thermal shock to the piping system upon initiation of the shutdown cooling mode.
a.
These valves are manually operated to initiate shutdown cooling af ter the reactor pressure vessel has been depressurized to 135 psig or less following neutronic shutdown so that only decay heat is involved.
b.
The RHR shutdown cooling loops are designed to ASME III and Seismic Class I requirements (capable to 500 psig).
c.
Typically, the warming of the shutdown cooling lines takes place for two to four hours each time that shutdown cooling is initiated, i.e.,
roughly two to five times a year.
d.
The motor-operated isolation valves E12-F053A or B, which are upstream of these warming valves, are normally closed until manually opened following receipt of " < 135 psig" pressure permissive signal to enable a shutdown cooling line-up.
l e.
An off site radiation exposure f rom these lines requires a l
LOCA with two coincident failures or a LOCA outside primary containment coupled with several forms of leak detection / isolation alarms.
The credibility of LOCA l
outside containment during shutdown cooling at 135 psig maximum pressure is extremely remote with ASME Section III Seismic Class I piping.
3.
RCIC Steam Supply Isolation Valves E51-F008 and E51-F063.
The RCIC steam supply line delivers steam to the RCIC turbine inlet where the throttle and turbine trip valve is located.
When called upon to recover water. level, the turbine trip throttle valve will open to cause the RCIC turbine to drive the RCIC pump.
Because the RCIC turbine is on-call at any time, it is necessary to provide pre-warming steam to the inlet lines up to the trip and throttle valve.
Valves E51-F008 and i
E51-F063 must, therefore, allow steam passage by being normally open essential valves.
r H. R. Denton November 28, 1983 a.
.These _ valves do not receive containment isolation signals, but
'instead receive system isolation signals to close in event of excess leakage to the RCIC steam chaise or equipment cubicle.
b.
Distinct reset-buttons are provided for this system isolation that is not combined with primary containment isolation signals nor ESF action signals (RCIC at LaSalle is not an ESF system).
c.
Separate system isolation signal reset buttons are provided for the inboard valves and for the outboard valve.
d.
Portions of the RCIC system isolation logic for these valves are derived f rom the leak detection system which is designed to identify leakages of 25 gpm to isolate the RCIC.
Th e corresponding offsite dose consequence is bounded by the small steam line break of Chapter 15 (FSAR).
e.
There is no off-site radiological contribution resulting from a LOCA occurring while these valves are open with an assumed failure of the redundant valves.
Based upon the f acts that these valves (F008 and F063) do not perform a containment isolation function, and because they are required to functionally mitigate the consequences (water inventory loss) of a LOCA, and since each of these valves is provided its own isolation signal reset (manual push button), it was concluded that no modifications to circuit logic was required per Item II.E.4.2 of NUREG-0737.
A subsequent modification for operator convenience has improved the system reset switch for Unit 2 and is pending for Unit 1.
Reference (j) inquiry sought additional information to clarify the position made on a Region III inspection report that justification had not been provided for all valves which remain open after containment isolation reset.
The above information responds to that need and is consistent with the verbal presentation made during the Management Maeting (Reference (k)) which was not continued to completion for all valves enumerated above.
One other item of information stated there, which merits repeating here, is that equalization valves E12F327 A, B, and C do not open upon reset of isolation signals.
They were considered during the above represented review processes also.
To the best of my knowledge and belief the statements contained herein are true and correct.
In some respects these statements are not based on my personal knowledge but upon information furnished by other Commonwealth Edison employees and consultants.
Such information has been reviewed in accordance with Company practice and I believe it to be reliable.
r-D p
8 H.'R. Denton November 28, 1983 If there are any further questions regarding this matter, please contact this office.
Very truly yours, tolzg}B5 C. W. Sch roeder Nuclear Licensing Administrator cc:
NRC Resident Inspector.- LSCS CWS/Im l
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