ML20078R630
| ML20078R630 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 11/12/1983 |
| From: | Schroeder C COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 7604N, NUDOCS 8311150236 | |
| Download: ML20078R630 (10) | |
Text
-_
[h Commonwealth Edison g
- ) oris First N;tional Plaza. Chicago. Illinois (C ~ Addrass R ply to: Post Office Box 767 Chicago. Illinois 60690 November 12, 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 Response to HELB and MELB Commitments Review Cited in Management Readiness Review for License Issuance for Unit 2 NRC Docket Nos. 50-373 and 50-374 Reference (a):
October 24, 1983 letter from A. Bournia to Applicant; Subject, Summary of Meeting Held at CECO (October 7, 1983) on NRC Management Review....For Unit 2 License.
Dear Mr. Denton:
At the conclusion of the referenced readiness for license meeting, Edison promised to review the FSAR on the subject of high and moderate energy lines to assure that all commitments have been satisfied.
This review has been completed with the results indicated below.
As discussed in the readiness meeting, the LaSalle approach utilized an Effects Analysis with initial assumptions that were conservatively defined, then as piping analyses and stress reports became available the original Effects Analysis was reworked and
. protective options refined for jet impingement and pipe whip restraints.
-A correlation review of pipe whip restraints with the
" Pipe Rupture Reports" for Units 1 and 2 and with the As-Built Gap and L2 Report" for both Units provided the justification for retention of the restraints that are currently in the plant, and, likewise justification for deletion from the design of those not now in the plant.
To address the adequacy of the HELB and the MELB designs, a chr.onological review was pursued as follows:
i
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8311150236 831112 DR ADOCK 05000373 pp/
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H. R. Denton November 12, 1983 High Energy Line' Breaks (HELB)
Background
The original HELB analysis was divided into two parts.
Breaks inside containment were covered in FSAR Section 3.6.
Breaks outside containment were covered in FSAR Appendix C.
These were both part of the original submittal to the FSAR in April, 1977.
These sections were written to show compliance with requirements of the Giambusso Criteria and the Branch Technical Position MEB 3-1.
Because the piping design and installation were not complete at that time, the exact method of protection to be used had not been defined.
Therefore, these sections were written to include all envisioned means of protection allowed by the guidance and criteria documents.
These options included pipe whip restraints, separation, equipment shields, pipe whip impact shields and jet impingement shields.
In addition, because of piping design, an alternate method was needed for selecting breaks.
Sargent &
Lundy conservatively assumed a break at each fitting.
The first round of questions, Q111.1-Q111.15, was answered in September, 1977.
This included the response to question Q111.13 dealing with jet impingement, which was answered on the basis of the initial assumption for breaks located at each fitting.
In mid 1978, questions Q111.44-Q111.46 and Qll1.50-Qll1.53 were addressed using the same assumption on break location.
The final questions received on the HEL8 analysis, Qll1.72 and Q111.81, were answered in early 1979.
These dealt with the pipe break exclusion area, not with the effects of the HELB.
Stress Reports Used to Reduce Restraints and Impingement Cases Class 1 piping stress reports were completed between February and June of 1981.
At that time the piping stress and fatigue factors could finally be used to identify potential HELBs in accordance with the appropriate guidelines.
This precluded the need to postulate certain breaks beyond the minimum required by the A.
Giambusso letter.
Use of the pipe stress results reduced the number of required whip restraints and also eliminated 19 of the original 22 " hits" on cable pan previously identified in response to earlier question Qll1.13, which was answered origin-ally without reference to pipe stresses.
In the three remaining
" hits" the cable pans are partially shielded by intervening piping or structural steel.
The total force on the cable pans is not expected to be high enough to cause failure.
H. R. Denton November 12, 1983
' Jet Impingement Shields (Effects Analysis)
With this reduced number of pipe breaks, combined with the results of 'the Safe Shutdown Analysis ( Appendix H and Response
.Qll1.74) and the System Safety Evaluation (Tab K of the Ninety-Day Report on EQ) and based on physical separation, it was concluded that neither jet impingement shields nor equipment shields were required either.
At the time this effects assessment was finalized, it was not engineering practice to document negative conclusions on design options; therefore, no formal documentation exists to record these particular aspects.
Pipe Whip Restraints (Effects Analysis)
Inasmuch as pipe whip restraints are required by the BTP MEB 3-1 and the Giambusso guidance, extensive documentation exists for them.
This documentation-includes the original study for all fitting breaks, the revised study based on the stress criteria and the as-built cold gap program.
A restraint by restraint review showed that 35 restraints per unit were no longer required based on stress criteria.
The required restraints for each unit are included in the as-built plant.
Conclusion for HELB The architect-engineer is confident that LaSalle is adequately designed for the HELB effects by use of physical separation and by the installed pipe whip restraints.
The conclusion-for not needing jet impingement shields, equipment shields or pipe whip
-impact shields remains valid on the basis of physical indepen-dence of alternate safety systems designed for safe reactor shutdown and removal of decay heat from the shutdown reactor system.
Medium Energy Line Break (MELB)
===.
Background===
Sargent & Lundy defined Commonwealth Edison Company's original position that no MELB analysis was required.
That is reflected in responses to questions QO10.1, QO10.14 and QO10.15.
- However, during the reviews the NRC did'not accept that position, as indicated in question Q010.26; therefore, an MELB analysis was performed and is presented in FSAR Appendix J.
It should be noted that because many of the moderate energy lines are Class D piping no stress analysis was required for them.
Also, the required Class 2 and 3 stress analysis were not available early enough in the design period to use the stress criteria to identify potential MELBs.
For these reasons, Edison decided to provide an assortment of spray shields (approximately ten per unit) that could not be eliminated on other than stress criteria.
o H. R.-Denton November 12, 1983 MELB Spray Shields These spray shields have been added to the piping in zones where the MELB cracks could splay electrical safety-related equipment.
The documentation for the MELB work is included in the A-E's design files.
The drawings in FSAR Appendix J indicate that the spray shields are mounted on the protected equipment.
This proved to not be the preferred mounting technique because of the need for extensive support structures.
The spray shields are installed on the piping itself as hemispheric deflectors to protect the indicated safety related electrical equipment.
Conclusion The MELB analysis required by the NRC is presented in Appendix J and it addresses all the applicable NRC requirements.
Enclosed for your information is a summary table extracted from the special review performed for meeting the commitment made at the referenced meeting.
To the best of my knowledge and belief the statements contained herein are true and correct.
In some respects these state-ments are not based on my personal knowledge but upon information furnished by other Commonwealth Edison employees and contractor employees.
Such information has been reviewed in accordance with Company practice and I believe it to be reliable.
We trust that-this information is responsive to the Edison commitment made at the October 7, 1983, management review for the LaSalle 2. license.
If you have any further questions, please contact this office.
Very truly yours, cal M =hla3 C.
W.
Schroeder Nuclear Licensing Administrator GRC/Im cc:
NRC Resident Inspector - LSCS 7604N
.u Pcgs 1 of 6 Paga Paragraph FSAR Statement Backup / Basis 3.6-1 3
Specifically, protection includes:
See FSAR Section 6.3
'i
.an ECCS 3.6-1 3
Specifically, pro,tec' tion _ includes:
See FSAR Sec' tion 6.2 a containment system
^
3.6-1 3
Specifically, protection includes:
See attached Pipe Whip Restraint a system of piping restraints Documentation Table.
3.6-1 3
Specifically, protection includes:
See FSAR Appendix H and the System Safety physical separation of equipment and Evaluation (Tab K of the Ninety-Day Report piping on EQ)
~
3.6-1 3
Specifically, protection includes:
Protective shields were not found to be protective shields necessary since there is very little I
safety-related equipment inside the i
drywell or steam tunitel and what there is divisional and physically separated.
See FSAR Appendix H and Tab K of the Ninety-Day Report on EQ for verification.
3.6-1 3
Specifically, protection includes:
The pipe whip restraints were the only physical constraints physical constraints found necessary.
This was verified in the Reviews of Pipe Tip Deflection and Restraint Deflection."
3.6-2 1
All large whipping pipes are restrained..
See attached Pipe Whip Restraint Documentation Table.
3'.6-2 3
.No systems.
required for safe The Reviews of Pipe Tip Deflection and shutdown are susceptible to HELB or Restraint Deflection verified this for
.MELB.
the HELB.
MELBs do not have to be postulated in the containinent.
See Appendix A to J.
F. O' Leary's letter of July 12, 1972, Section B.2 3.6-2 4
. the CRD withdrawal lines are See the Reviews of Pipe Tip Deflection protected.
so that.no more than one and Restraint Deflection.
is allowed to be completely crimped.
Pcga 2 of 6 Pcga Paragraph FSAR Statement Backup / Basis 3.6-2 6
By limiting the total area, all broken See the Reviews of Pipe Tip Deflection pipes involving recirculation loops to and Restraint Deflection.
an area less than or equal to that of the design-basis accident.
- 3. 6-2a/
1/1 the total break area shall not See the Reviews of Pipe Tip Deflection 3.6-3 exceed the sum of one feedwater header and Restraint Deflection.
pipe area, one steam line (upstream of l
flow limiter)' pipe area, and one core spray pipe area.
3.6-3 2
. breaks involving one recirculation See the Reviews of Pipe Tip Deflection loop shall not result in loss of function and Restraint Deflection.
to the other recirculation loop or loss of coolant from the other loop in excess l
of that.
l 3.6-3 4
For breaks not involving recirculation See the Pipe Tip Deflection and Restraint piping, at least two LPCI pumps or one Deflection Reviews.
core spray system shall be available for core cooling.
3.6-3 5
For breaks involving recirbulation See the Pipe Tip Deflection and Restraint piping, at least one core spray line and Deflection Reviews.
i two LPCI pumps, or two core spray lines, shall be available for core cooling.
1 3.6-3 6
For a LOCA with a total effective break See the. Pipe Tip Deflection and Restraint 2
area less than 0.7 ft, either the HPCS Deflection Reviews.
or ADS shall be available for reactor depressurization.
\\
3.6-3
'7 For liquid breaks such as cleanup See the Pipe Tip Deflection and_ Restraint suction or combination of liquid and Deflection Reviews.
1 steam breaks whose total break' area is less than 0.7 ft2, in which the ADS system is required for depressurization, at least (n-1) ADS valves must be available '(n = total number of ADS valves).
I
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+
Paga 3 of 6 Pagn Paragraph FSAR Statement Backup / Basis
'3.6-3 8
For breaks less than the equivalent f. low See the Pipe Tip Deflection and Restraint area of one open ADS valve, at least Deflection Reviews.
- j
.(n-1) ADS valves must be available.
However, the required number of ADS valves will be one less for each additional steam break. area equivalent to the area of one open ADS valve.
3.6-3 10 Leaktightness of the containment fission See.various compartment pressurization. '
product barrier shall be assured studies filed in the Structural Dept.
throughout any LOCA.
,i e
3.6-4 1
For those lines which penetrate the-See the system single line drawings for containment and are normally closeda verification.
Examples are ECCS during operation, the inboard isolation injection lines.
valve is located as close as practical to the reactor pressure vessel.
This arrangement reduces the length of pipe subject to a pipe break.
]
3.6-4 2
For those lines which penetrate the See the system single line drawings for i
containment and are open during normal verification.
Examples are MS lines.
l operation, the outboard is~olation valve i
is located as close as practical to the containment, with surrounding equipment located so as to preclude the possibility J.
that a single event can cause rupture of the reactor coolant pressure boundary pipi'ng anywhere from the. containment to and including this isolation valve.
3.6-5 3
The analysis of postulated line breaks See the Pipe Tip Deflection and the and the resulting addition of restraint Restraint Deflection Reviews.
features into the design have ensured that failure in any single high energy line in the plant, will not result in unacceptable damage to any other. system or component.
Page 4 of 6 Paga Paragraph FSAR Statement Backup / Basis 3.6-24 6
Barriers are provided to preserve the They are located such that no pipe independence of the LPCS and LPCI systens failure can prevent the low-pressure when they are so located that a pipe water injection from occurring.
See failure could prevent the low-pressure ~
the Pipe Tip Deflection and the Restraint 6
water injection from occurring.
Deflection Reviews.
3.6-24 7
Dynamic effects associated with the LOCA In all but one case pipe whip restraints do not compromise the integrity of the are used, however, for a 2" break on containment and drywell.
In most cases, Subsystem RH-27 a restraint could not be restraint of the potentially hazardous designed.
Instead, a calc. was done pipes will be utilized.
showing the containment liner are not affected.
3.6-26 1
Equipment shields are provided in order See Response No. 5 to isolate the portion of the equipment in an accident and prevent it from causing a further chain accident.
These shields are designed to ' withstand the rupture forces from piping, jets, and equipment, and will segregate the redundant systems.
3.6-26 2
Pipe whip and impact shiel*ds are designed to withstand the impact forces As above, none were found to be required i
for the same reason.
Also see arising from the shipping action.
Response No.
6.*
3.6-26 4
Jet impingement shields are provided to "See-Response No. 5.
limit the consequence of rupture of the piping and are designed to withstand the resultant jet forces, using the codes specified in Section 3.8.
beflection utilized to redirect a jet 3.6-26 8
See Response No. 5.
spray from an essential component.
3.6-28 2
All safety-related systems and components Safety-related is clarified to mean safe have been protected from the dynamic shutdown.
See Appendix' C for confirmabLcn effects of pipe whip and are assumed to function under ncrmal operating conditions'.
_ = _ _
Page 5 of 6 Paga
~ Paragraph FSAR Statenent Backup / Basis 6.1 4
The postulation of circumferential and Some breaks were deleted after stress and longitudinal breaks on high-energy reports were available, based on the lines of 4-inch diameter or more is stress criteria.
based on the A. Giambusso letter of December 15, 1972, which recommends l
that the breaks be considered at points
{
where stresses exceed 0.8 (S3+Sh) -
However, the more restrictive method of
~
postulating breaks at pipe fittings j
such as elbows,.was used.
6.2 2
The effects of pipe rupture in all of See Response No. 5.
the above systems on essential components and structures were determined for the case of both pipe whip and jet impingement.
J.3-1 1
The location of these spray shields is The' final design locates all spray shown by blue lines in Figures J.2-1~
shields on the pipe rather than some through J.2-ll.
shown at the equipment in the figures.
However, the same piaces of equipment are protected from the same MELB lines.
See Transco drawings for final location of shields.
Q10.15-1 3
Pipe breaks outside containment were postulated at cach fitting location.
A'fter the stress analysis was completed some breaks were eliminated, based on the stress criteria.
Olu. 134 8
Following is a list of cable pans that After the stress' analysis was performed are affected by jet impingement.
the following breaks no longer had to be Affected cable pans that cannot with-postulated:
stand these forces will be reropted or C-77 C-201 C-210 C-237 shielded from the jet.
C-202 C-114 C-235 C-125 C-82 C-217 C-211' C-237 In addition, the stress criteria in
___ C _77 C-218 C-203 C-207B conjunction with Rev. 1 of MEB 3-1 C-200, C-228 C-230 C-125 issued in' July 1981 allows the deletion C-201 C-210 C-226 C-122 of the longitudinal break when the stress h_~ff h~_h$
h25 riteria are met.
This eliminated the
,l Page 6 of 6 7,
t Pcga Paragraph FSAR Statement B'ackup/ Basis i.
2H1.1}-1 8
(Qint'd) following breaks:
i C-82 C-218
' C-203 C-232 1
C-200 C-222 C-230 C-207 C-217 C-211.
C-226 This leaves only three breaks; C-228, i
C-229 and C-122.
Inspection of the L
composite drawings show that for each j
break there is substantial intervening structural steel and/or piping which will II
~
reduce the area of the cable pan that can be sprayed.
For this reason the cable pan is ' not expected to experience failure.
Ilowever, even if a failure would occur, i
there would be no effect on' the redundant cable pan from the other electrical division so a safe shutdown still would not be impaired.
I 2131.1& 1 3
The criteria used for postulating break Af ter the stress analyses were available l
locations is ' stated in the Introduction the breaks were reduced per the guidance to Appendix C:
breaks wer criteria.
In addition, after MEB 3-1, at pipe fitting locations.g postulated Longitudinal Rev. 1 (July 1981) was issued, breaks were oriented at locations 360' longitudinal breaks were reorientated to around the axis of the pipe and its requirements.
protection was' designed for any angle that' affected safety-related systems, components, or structures.
2]l1J4-1 4
Since only' two intermediate breaks are Af ter the stress-analys.es were available, required, the practice of locating the number of breaks was reduced, but breaks at pipe fittings far exceeds this the requirements are still met.
requirement.
e
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