ML20206J692
| ML20206J692 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 05/05/1999 |
| From: | Jamie Benjamin COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9905120302 | |
| Download: ML20206J692 (73) | |
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l Lonunonu c.iltii I dison ( ompany Ias alle Generating station 2001 North list Road Marseilles II. 614 iIars' l 'I rl 814 45'b'61 l
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May 5,1999 l United States Nuclear Regulatory Commission Attention: Document Control Desk l Washington, D.C. 20555 l
LaSalle County Station, Units 1 and 2 Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374
Subject:
Request for a License Amendment to reyise the basis for evaluation of VR Exhaust Plenum Masonry Walls for LaSalle Units 1 and 2.
Reference:
Letter dated April 20,1998 from F. Dacimo to the U.S.
NRC, Submittal of License Event Report #98-007-00,
> Docket #050-373 Pursuant to 10 CFR 50.90, Commonwealth Edison Company (Comed) proposes to amend Facility Operating Licenses NPF-11 and NPF-18, LaSalle County Station Units 1 and 2, respectively, to revise the basis for evaluation of VR Exhaust Plenum Masonry Walls for LaSalle Units 1 and 2.
The proposed amendment requests approval of the use of different methodology and acceptance criteria than originally accepted for LaSalle Cdunty Station (LaSalle) for the reassessment of certain masonry walls subjected to transient HELB pressurization loads resulting from a High Energy Line Break (HELB). J
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f 9905120302 990505 PDR ADOCK 05000373 P PDR A l nionn (,ompan) t___________ -
i l May 7,1999 U.S. Nuclear Regulatory Commission Page 2 l
Comed requests approval of this license amendment request prior to the next Unit 1 refuel outage, L1R08, scheduled to begin October 23,1999.
The amendment should be made effective upon issuance. Comed will l implement the Unit 1 amendment prior to startup of LaSalle, Unit 1, from l L1R08. Comed will implement the Unit 2 amendment within 60 days after i
issuance of the amendment for LaSalle Unit 2. In a manner similar to Unit 1 startup from L1F35, Unit 2 started up from its outage, L2R07 on April 9, i 1999 under an assessment of the Operability of the walls using the l provisions of Generic Letter 91-18, Revision 1, with all design changes associated with this proposed amendment completed.
l This proposed amendment request is subdivided as follows:
- 1. Attachment A gives a description and safety analysis of the proposed changes in this amendment.
- 2. Attachment B describes Comed's evaluation performed in accordance with 10 CFR 50.92 (c), which provides evidence to j determine that no significant hazards consideration is involved.
- 3. Attachment C provides an Environmental Assessment Statement Applicability Review per 10 CFR 51.21.
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- 4. Attachment D is the sketch of the air return risers & plenum.
- 5. Attachment E is a design / construction description of the masonry walls.
- 6. Attachment F is the Summary of the Masonry Wall Reassessment Calculation.
- 7. Attachment G is the Summary of Calculations / Analyses for the transient pressurization.
- 8. Attachment H is the ' Qualitative Summary of Environmental Impacts Following a Postulated HELB in the Upper Main Steam Tunnel.
- 9. Attachment I is the Single Failure Analysis for Pressure Relief Dampers and Excess Flow Check Dampers.
This proposed amendment has been reviewed and approved by Comed On-Site and Off-Site Review in accordance with Comed procedures.
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l May 7,1999 U.S. Nuclear Regulatory Commission Page 3 i
Comed is notifying the State of Illinois of this application for amendment by {
transmitting a copy of this letter and its attachments to the designated state '
official.
I affirm that the content of this transmittal is true and correct to the best of my knowledge, information and belief.
If there are any questions or comments concerning this letter, please refer l them to Frank Spangenberg Ill, Regulatory Assurance Manager, at (815) 357-6761, extension 2383.
j Respe ully '
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ffrey enjamin Site Vi resident LaSal e County Station j Subscribed and swom to before mj, a Notary Public in and for the Stgtp of Illinois, this 5- day of W/m q
, /999 .
_ OFFICIAL SEAL DEBRA J. FEENEY NOTARY PUBUC, STATE OFILLINDIS MY COMMISSION EXPIRES 1012000 C. M e m Nota 6Public Attachment cc: Regional Administrator- NRC Region lli NRC Senior Resident inspector - LaSalle County Station Office of Nuclear Facility Safety - IDNS l
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ATTACHMENT A,(Page 1 of 9)
DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES A.
SUMMARY
OF THE PROPOSED CHANGES Commonwealth Edison Company (Comed) proposes to amend Facility Operating Licenses NPF-11 and NPF-18, LaSalle County Station Units 1 and 2, respectively, to revise the basis for evaluation of the Reactor Building Ventilation System (VR) Exhaust Plenum Masonry Walls for LaSalle Units 1 and 2. The proposed amendment requests approval of the use of different methodology and acceptance criteria than originally accepted for LaSalle County Station (LaSalle) for the reassessment of certain masonry walls subjected to transient pressurization loads resulting from a High Energy Line Break (HELB).
This change involves reassessment of LaSalle Reactor Building Ventilation (VR) exhaust plenum masoruy walls for a transient pressurization effect downstream from the VR exhaust over-pressurization protection dampers. Attachment D provides a sketch showing the general arrangement VR air return risers and the exhaust plenum masonry walls. Attachment E provides a general design / construction description of the exhaust plenum masonry walls and includes more detailed sketches.
The original analyses for concrete masonry walls did not analyze for effects of HELB pressurization loads based on the assumption that dampers in the ventilation system would close instantaneously, and thus were protected from pressurization loads associated with a HELB. However, this assumption was proven to be invalid and was documented in LER 98-007. Additional protection dampers were added as a result of the LER to help reduce the pressurization effects of HELB on the walls. It was ,
determined that even with the additional protection campers, the VR exhaust plenum '
masonry walls would still be subjected to a transient pressurization force. This transient l pressurization force would have significantly reduced safety margin for rupture of the walls using the analysis techniques presented in the LaSalle curr. 8t hensing basis with an assumed instantaneous pipe break and a non-instantaneous w.nper closu.e.
Attachment G summarizes the transient pressurization calculation. For completeness of the analysis, the masomy walls will be reassessed for this transient pressurization.
The change defines the transient HELB pressurization load analysis, use of load combinations, and acceptance criteria for the masomy walls (masoruy and support steel) for this reassessment. The change suppons analyses involving a localized population of Concrete Masonry walls, which are subject to transient HELB pressurization loads, in the respective Unit reactor building ventilation (VR) system exhaust equipment room plenum (VR exhaust plenum) on the Auxiliary Building elevation 786' 6". The walls must withstand loading as a result of a HELB outside of the primary containment,in the main steam tunnel.
l ATTACHMENT A,(Page 2 of 9)
DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES B. DESCRIPTION OF THE CURRENT REQUIREMENTS The design of masonry components is discussed in Attachment 3.C of the UFSAR.
The safety design function of the block walls is to remain standing. The design methodology is discussed in Comed's response to the NRC for IEB 80-11. Specifically, in Comed's response to the NRC for IEB 80-11 (Report of 11/19/82, transmitted under letter dated 12/9/82) it is stated:
"lix hds ed hd amlinationsfor dx safety niatalamtre immrymdis are in agmrrmt 1 tith dx LaSalle Caatty Units 1 ard 2 FSAR, andan>also in agartmtzdd> SEB Interim Criteria, Rev.1,Jzdy 1981."
However, in this same response,it is also stated:
"It has lun zenfialdut no safety-nlatalanntemasonryzadis associatalwid> dx operatim ofIASalle Gmty Units 1 & 2 an udpa to impwt orpnsacrizatim hds ormissiles due to pip >zdip, pipe break, jet impngrimt, wd/or tom.da "
l Therefore, although the SEB Interim Criteria for Safety-Related Masonry Wall Evaluation, Appendix A to SRP Section 3.8.4, addresses pressurization loads due to ;
HELB (P ), the VR exhaust plenum masonry walls were not originally analyzed or designed for HELB pressureloads.
i Unit 1 is currently operating in accordance with an assessment of the Operability of the j walls, using the provisions of Generic Letter 91-18, Revision 1, in response to LER 98 007 (Operability Evaluation # OE98025). The Unit 1 VR exhaust plenurn masonry walls will be evaluated and modified in accordance with the proposed changes prior to start-up after planned outage L1R08. The Unit 2 VR exhaust plenum masonry walls have been evaluated and modified in accordance with the proposed changes during L2R07 and will operate under an assessment of the Operability of the walls, using the provisions of Generic Letter 91-18, Revision 1, until approval of the amendment request.
I C. BASES FOR THE CURRENT REQUIREMENTS UFSAR Section 3.C addresses Category I Concrete Masonry Walls at LaSalle. This section was added to document the evaluation of these walls as required by NRC 4 l
Bulletin 80-11, "Masoruy Wall Design", dated May 8,1980, and was tracked by LaSalle Unit 1 Facility Operating License NPF 11, License Condition C.8. Per NRC Safety Evaluation Report, NUREG-0519, Supplement 5, the design and construction of masonry walls at LaSalle was acceptable. The NRC approved an exception concerning 6 masonry walls, which had a safety factor greater than or equal to 2.5 against the average modulus of rupture of the masonry obtained from tests at Clinton Power Station.
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ATTACHMENT Ac (Page 3 of 9)
DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES In regards to the masonry acceptance criteria, the original acceptance criteria used are the National Concrete Masonry Associations (NCMA) " Specification for the Design and Construction of Load Bearing Masonry - 1979" allowable stresses times a 1.67 factor.
These allowable stresses correspond to stress equal to the modulus of rupture (fr) of the masonry divided by a factor of safety of 3.35. (See References I.3 and I.8)
In the original design effort at LaSalle, the areas adjacent to the Main Steam Tunnel were considered protected from over-pressurization due to a Main Steam Line Break (MSLB) by the use of check dampers and isolation dampers. Closure times of these dampers were assumed to be " instantaneous" since they were closing in a fraction of a second.
The practice of airflow dampers to control the pressurization effect is stated in Section 9.4.2.3(i) of the LaSalle UFSAR. This is consistent with the masonry wall design practice, as illustrated in the calculations attached to the July 8,1980 letter from D.L Peoples -
Comed to D.G. Eisenhut - NRC. (Reference I.2)
The adequacy of the assumption made in relation to the rapidly closing dampers was appropriate analytical practice at that time. Consequently, transient analysis was not considered necessary. Section 9.4.2.3(i) of the LaSalle UFSAR captures this evaluation by stating:
"Airflavdxck dan;m arepaddin dxmain staanpipe nurd to dxck the statmfacin dx mictorluildingfolloaing dxpipeimuk in dxmain staanpp aard 71x swan is niaisalthmg6 dx blauntpirds to dx twbine luilding. "
Accordingly, the design of the VR plenum masonry walls did not account for a transient pressurization due to HELB.
D. NEED FOR REVISION OF THE REQUIREMENTS When the question of non-instantaneous closure of VR exhaust dampers was identified in 1997, the decision was made to evaluate the finite closure time of the protection dampers associated with the pressure excursion caused by the HELB. The conclusion of this analysis is that the calculated closure time results in a nommal pressurization effect. Therefore, the original assumption of " instantaneous" closure is no longer justifiable.
To reduce the effects of HELB transient pressurization on the masoruy walls, additional dampers to vent and check flow are being added to the VR system. To verify the adequacy of the dampers, it is necessary to address the transient pressurization effects accounting ta the damper opening / closure duration. However, since the original design of the VR exhaust plenum masonry walls did not account for HELB pressure loads at LaSalle, a reassessment criteria is required to evaluate these walls. The proposed reassessment criteria is applicable to the VR exhaust plenum masonry walls subjected to a short term differential HELB pressurization load, defined herein as Paus, due to the non-instantaneous response of the protection dampers.
ATTACHMENT A,(Page 4 of 9)
DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES Comed concludes that the SEB Interim Cdteria for masomy walls with regard to load combinations including P. is not appropriate for the LaSalle VR exhaust plenum masonry walls because the Paus loading is transient; is a result of a detailed pressurization analysis; and is primarily mitigated by the dampers. Accordingly, the load combinations using PA are overly conservative. The proposed changes take into consideration that the protection dampers will mitigate Paas, such that a sustained i loading does not occur. Additionally, the acceptance criteria for the masonry walls subjected to PnEtB loads recognize that the critical parameter for the walls during this event is their continued integrity. In essence, the criteria need only ensure that the walls do not collapse. A License Amendment Request was determined to be needed due to l the finding of an Unreviewed Safety Question when .LaSalle performed a 10CFR50.59 j Safety Evaluation. l l
E. DESCRIPTION OF THE PROPOSED CHANGES The change provides criteria to reassess the affected VR plenum masoruy walls. The specific changes from the onginal analyses involve the following:
- 1. Load Combination:
- a. Define PnEta as the transient HELB pressurization load on the VR plenum masoruy walls resulting from non-instantaneous opening / closure of the protection dampers.
- b. Specify that the Load Factor on Paas due to HELB is 1.0 for all cases.
- c. The Loading Combination of Paus and seismic is the Square Root of the Sum of Squares (SRSS).
- 2. The Masoruy Wall Acceptance Criteria The Masonry Wall stresses shall be limited to the modulus of rupture of the masomy (as determined by Clinton Power Station testing) divided by a safety factor of 2.5. This is discussed in more detailin Attachment E
- 3. Support Steel Acceptance Criteria The Masonry Wall Support Steel stresses shall be limited to AISC allowable stresses increased by a 1.6 factor. In cases where this allowable can not be met, and the section in question can fully develop its plastic moment, these members will be qualified using a maximum ductility ratio of 10. This is discussed in detailin Attachment F.
ATTACHMENT A,(Page 5 of 9)
DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES The HELB analysis considered the addition of two dampers:
- 1(2)VR90Y, VR Exhaust Pressure Relief Damper.
- 1(2)VR91Y, VR Exhaust Excess Flow Check Damper.
Per the analysis for the MSLB, the pressure relief damper opens and the excess flow check damper closes to limit the pressurization for the VR exhaust plenum.
F. SAFETY ANALYSIS OF THE PROPOSED CHANGES The following sections discuss the different components of the proposed changes in more detail.
- 1. Load Combinations LaSalle has selected the proposed load combinations in consideration of the following:
- Isolation, check, and relief dampers protect the walls; therefore the pressurization effects are not sustained, but are transient in nature.
- The transient pressurization effect (Pnas) is derived from a conservative detailed amlysis of an instantaneous HELB combined with non instantaneous damper opening / closure. Due to the precise nature and conservatism of this HELB analysis, there is little uncenaintyin Paas. Therefore a load factor of 1.0 is used for all abnormalload combinations.
- Paus is a shon duration, dynamic load. Accordingly, the seismic and transient HELB pressurization loads are combined using the Square Root of Sum of the Squares (SRSS) method because the peak effects of these dynamic loads are unlikely to occur simultaneously. This combination method is used in the analysis of other components such as component supports.
The proposed load combinations accordingly provide an adequate basis for reassessment of the VR exhaust plenum masonry wall systems.
- 2. Masoruy Acceptance Criteria The critical parameter for the masonry walls is for their continued integrity. The integrity of masonry walls was previously tested at Clinton Power Station during the IEB 80-11 program. That testing, accepted by the NRC for LaSalle station per Supplement 5 of the SER (August,1983), revealed the ultimate capacity of the walls, as denoted in terms of the modulus of rupture of the masonry unit.
The results of this testing was previously used to qualify six other walls at LaSalle Station, as reported in LaSalle County's SER, Supplement #5 with a safety factor against rupture of at least 2.5. See Attachment E for more information.
ATTACHMENT A,(Page 6 of 9)
I DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES j The construction of the VR exhaust plenum masoruy walls is the same as the original six walls that were accepted based on the Clinton Power Station !
I masoruy walls that were tested. The VR exhaust plenum masonry walls are describedin Attachment E.
The proposed acceptance cnterion provided a reasonable factor of safety against ,
failure of the masonry,thus ensuring the walls' integrity. As stated above, this )
acceptance criterion proposed for evaluating these walls has been previously J used at LaSalle and accepted by the NRC.
- 3. Support Steel Acceptance Cnteria The masonry walls are supported by steel posts that are typically wide-flange shapes. To reassess these elements, it is appropriate to consider them similar to high-energy line break systems (i.e. pipe whip restraints) that will maintain their integrity as they absorb the energy of the transient pressurization due to HELB.
High-energyline breaks are discussed in Section 3.6 of the UFSAR. The discussion in this section focuses on the design of pipe whip restraints, and in Table 3.6-6 acceptance criteria are provided. This table shows that the energy absorbing portions of the pipe whip restraint are allowed to go plastic, thereby absorbing energy. While Table 3.6-6 of the UFSAR deals with energy absorbing portions of the pipe whip restraints, wide-flange shapes are not addressed.
Wide-flange shapes absorb energy through flexural deformations.
Guidance on appropriate acceptance criteria for flexural members is prosided in Appendix A to SRP 3.5.3, " Barrier Design Procedures." This appendix indicates that for tension due to flexure in structural steel members, a ductility ratio value not to exceed 10.0 is acceptable. See Attachment F for additionalinformation.
SRP 3.8.4, paragraph III.5 also notes that at some localized points on the structure, the allowable stresses specified for " structural steel" may be exceeded, provided that integrity of the structure is not affected.
As additional guidance, ANSI /AISC Specification N690-1994, " Specification for the Design, Fabrication, and Erection of Steel Safety Related Stmetures for Nuclear Facilities" was reviewed. Table Q1.5.8.1 of this document indicates that a ductility of 12.5 is acceptable.
In conclusion, both of the two aforementioned documents present reasonable values of ductility factors for flexural members. Accordingly, a ductility factor ,
of 10.0, as stated in SRP 3.5.3.shall be used for the steel posts since the SRP ductility ratio value is more conservative than the 12.5 value proposed by the ANSI /AISC specification.
ATTACHMENT A,(Page 7 of 9)
DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES
- 1(2)VR90Y, VR Exhaust Pressure Relief Damper.
- 1(2)VR91Y, VR Exhaust Excess Flow Check Damper.
- a. These dampers were installed on Unit 2 per the design change process to reduce the pressurization loads on the block walls. The 1VR90Y damper has been installed on Unit 1 and the IVR91Y damper will be installed in L1R08.
Per the analysis for the MSLB, the pressure relief damper opens and the ;
excess flow check damper closes to limit the pressurization of the VR exhaust plenum. ,
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- b. When the relief damper opens, it opens into the Upper Ventilation Equipment Room in the Auxiliary Building. The affect of the release of the air / steam mixture through the relief damper as a result of the MSLB has been evaluated and determined to be small. See Attachment H for more detailed information.
- c. The new pressure relief damper and excess-flow check damper are safety-related and are analyzed to function under the conditions created by the MSLB. In addition, the dampers and the duct they are installed in have been analyzed to assure no failure will occur during an Operating Basis Earthquake (OBE) or Safe Shutdown Earthquake (SSE).
Based on an analysis of potential failure modes (See Attachment I) in accordance with ANSI /ANS-58.9-1981, " Single Failure Criteria for Light Water Reactor Safety-Related Fluid Systems", Paragraph 4.1, the active function of the pressure relief damper and excess flow check damper are considered exempted from consideration of single failure. 3 The principles governing operation of the dampers are simple and direct and not subject to change or deterioration with time, similar to the function of a code safety relief valve and a swing check valve. With periodic testing of the dampers, continued reliable performance is assured.
Administrative controls will be in place prior to implementation of this change to assure the testing and maintenance is penodically performed in accordance with vendor recommendations. These dampers will be included as equipment required to be monitored / maintained per 10 CFR 50.65.
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ATTACHMENT A,(Page 8 of 9)
DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES G. IMPACT ON PREVIOUS SUBMITTALS The proposed license amendment does not impact any previous submittals currently under review by the NRC for LaSalle.
H. SCHEDULE REQUIREMENTS Comed requests approval of this license amendment request prior to the next Unit i refuel outage, L1R08, scheduled to begin October 23,1999. The amendment should be made effective upon issuance. Comed will implement the Unit 1 amendment prior to startup of LaSalle, Unit 1, from L1R08. Comed willimplement the Unit 2 amendment within 60 days after issuance of the amendment for LaSalle Unit 2. In a manner similar to Unit 1 startup from LIF35, Unit 2 started up from its outage, L2R07 on April 9,1999 under an assessment of the Operability of the walls, using the provisions of Generic Letter 91-18, Revision 1, with all design changes associated with this proposed amendment completed.
I. REFERENCES
- 1. S. A. Varga, NRC, to All Constmetion Pennit and Operating License Applicants; Information Request on Category I Masony Walls Employed by Plants under CP and OL review, dated Apnl 21,1980.
- 2. L. Peoples letter to D. G. Eisenhut, dated July 8,1980 in response to Information Request on Categoy I Masonry Walls Employed by Plants under CP and OL review, dated April 21,1980.
- 3. R. L Tedesco, NRC, to J. S. Abel, Request for Additional Information on Category I Masonry Wall Design, dated January 19,1981.
- 4. L O. DelGeorge letter to B. J. Youngblood dated Febmary 4,1981, in response to the Request for Additional Information on Categoy I Masonry Wall Design, datedJanuary 19,1981.
- 5. R. L Tedesco, NRC, to J. S. Abel, dated March 2,1981, requesting additional information in the design of concrete masonry walls for LaSalle County Station, Units 1 and 2.
- 6. L. O. DelGeorge letter to A. Schwencer, dated April 24,1981, providing response to R. L. Tedesco letter to J. S. Abel, dated March 2,1981, requesting additional information in the design of concrete masonry walls for LaSalle County Station, Units 1 and 2.
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ATTACHMENT A,(Page 9 of 9)
DESCRIPTION AND SAFETY ANALYSIS FOR PROPOSED CHANGES
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- 7. C W. Schroeder letter to R. D. Walker dated February 24,1982, providing j
" Final Report in Response to NRC IE Bulletin 80-11, Masonry Wall Design for )
LaSalle County Station."
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- 8. C W. Schroeder letter to A. Schwencer dated December 9,1982, providing t
"LaSalle County Station Units 1 and 2 Reevaluation of Safety-Related Concrete Masomy Walls."
- 9. C W. Schroeder letter to Director of Nuclear Reactor Regulation, Attn. A. 3 Schwencer, dated April 19,1983, providing "LaSalle County Station Units 1 and 2, Masoruy Walls - Supplemental Information."
- 10. NUREG-0519, Safety Evaluation Report related to the operation of LaSalle County Station Units 1 and 2, Docket Nos. 50-373 and 50-374, dated March 1981, Section 3.8.3.
- a. NUREG4519, Supplement 2, dated February 1982.
- b. NUREG-0519, Supplement 5, dated August 1983 l
ATTACHMENT B (Page 1 of 7)
SIGNIFICANT HAZARDS CONSIDERATION !
Commonwealth Edison (Comed) Company has evaluated this proposed amendment and has 1 provided the evidence below for a determination that it involves no significant hazards l consideration. According to 10 CFR 50.92(c), a proposed amendment to an operating hcense I involves no significant hazards consideration if operation of facility in accordance with the proposed amendment will not:
Involve a significant increase in the probability or consequences of an accident I previously evaluated; Create the possibility of a new or different kind of accident from any previously analyzed; or Involve a significant reduction in a margin of safety.
Commonwealth Edison Company (Comed) proposes to amend Facility Operating Licenses NPF-11 and NPF-18, LaSalle County Station Units 1 and 2, respectively, to revise the basis for evaluation of the Reactor Building Ventilation System (VR) Exhaust Plenum MasonryWalls for LaSalle Units 1 and 2. The proposed amendment requests approval of an the use of different methodology and acceptance criteria than originally accepted for LaSalle County Station (LaSalle) for the reassessment of certain masonry walls subjected to transient pressurization ;
loads resulting from a High Energy Line Break (HELB).
This change involves reassessment of LaSalle VR exhaust plenum masonry walls for a transient pressurization effect downstream from the VR exhaust over-pressurization protection d.unpers.
The original analyses for concrete masonry walls did not analyze for effects of HELB pressurization loads based on the assumption that dampers in the ventilation system would close instantaneously, and thus the walls were protected from HELB. However, this assumption was proven to be invalid and was documented in LER 98-007. Additional protection dampers were added as a result of the LER to help reduce the effects of HELB on the walls. It was determined that even with the additional protection dampers, the VR exhaust plenum masonry walls would still be subjected to a transient pressurization force. This transient pressurization force would have significantly reduced safety margin for rupture of the walls using the analysis techniques presented in the LaSalle current licensing basis with an assumed instantaneous pipe break and a non-instantaneous damper closure. For completeness of the analysis, the Unit 1 masoruy walls will be reassessed prior to startup from L1R08 for this transient pressurization.
Unit 2 masoruy walls were reassessed for this transient pressurization during L2R07.
The change defines the transient HELE pressurization load, use of load combinations, and acceptance criteria for the masoruy walls (masonry and support steel) for this reassessment. The change supports analyses involving a localized population of Concrete Masonry walls, which are subject to transient HELB pressurization loads, in the respective Unit VR system exhaust 1
equipment room plenum (VR exhaust plenum) on the Auxiliary Building elevation 786' 6". The walls must withstand loading as a result of a HELB outside of the primary containment,in the main steam tunnel, such that the walls do not adversely impact adjacent safety-related components.
ATTACHMENT B (Page 2 of 7)
SIGNIFICANT HAZARDS CONSIDERATION The evaluation that the criteria set forth in 10 CFR 50.92 are met for this amendment request is indicated below:
Does the change involve a significant increase in the probability or consequences of an accident previously evaluated?
The change involves reassessment of the VR exhaust plenum due to a transient pressurization during a Main Steam Line Break (MSLB). Since the transient pressurization is a result of the MSLB, and the block walls and the dampers are not initiators of any accident, the probability of an accident previously evaluated is not ;
affected. q This analysis does not affect the total amount of radioactive release due to the MSLB Outside of the Primary Containment, so the total offsite dose consequences does not change. A small portion of the release, which passes the dampers prior to closure, will now be an elevated release via the plant ventilation stackinstead of a ground level release. The original analysis assumed the entire release was a ground level release, and thus remains bounding for the MSLB accident.
The Control Room and Auxiliary Electric Equipment Room (AEER) dose consequences are impacted only slightly due to the small amount of steam / air nuxture released from the new pressure relief damper. The steam / air mixture becomes mixed with the air volume in that area of the Auxiliary Building but was all assumed to be available for inleakage to the Control Room and AEER. The dose increase for the Control Room and AEER is less than or equal to 0.05 Rem thyroid and negligible change to the whole body dose, such that the dose due to the MSLB accident remains much less than the DBA LOCA dose and General Design Criteria 19. The MSLB accident dose consequences remain bounded by the Design Basis Loss of Coolant Accident.
The effects of the steam released by the pressure relief damper into the Auxiliary Building has been evaluated for environmental qualification impact on systems, structures and components (SSCs) in the area of the Auxiliary Building affected for both radiation and steam / temperature affects. The effect on area temperature is about 4 F and is above initial temperature for not more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The change in humidity is negligible, and radiation dose impact is small and bounded by previous calculations.
These consequences assume that the VR exhaust plenum masonry walls do not mpture based on the design changes being made in conjunction with the masonry wall reevaluation for each LaSalle Unit that will prevent the failure of the VR exhaust plenum masonry walls.
Therefore this proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated.
l A'ITACHMENT B (Page 3 of 7)
SIGNIFICANT HAZARDS CONSIDERATION Does the change create the possibility of a new or different kind of accident from any accident previously evaluated?
The MSLB accident is previously analyzed but considered only instantaneous closure of installed dampers. The reevaluation and design changes extend the previous accident analysis to assure that structures previously considered unaffected by the MSLB will maintain their structural integrity. The block walls are static and the dampers function in response to an accident, thus the analysis method and design changes are not accident initiators. Therefore the change does not create the possibility of a new of different kind of accident from any accident previously evaluated.
The design changes being made in conjunction with the masomy wall reevaluation for each LaSalle Unit that will prevent the failure of the VR exhaust plenum masonry walls are as follows:
- 1) Installation of a pressure relief damper,
- 2) An excess-flow check damper, and
- 3) Required masonry wall support improvements in the reactor building ventilation exhaust plenum for each Unit.
The reevaluation of the masomy walls uses different load factors and load combinations as well as reduced acceptance criteria than previously used for these walls. The change in the evaluation does not cause the rupture or failure of the effected masonry walls, since the evaluation shows the walls remain intact.
The installation of the above design changes, in conjunction with masomy wall analysis assure that the subject masonry walls will not rupture or fail. Therefore, SSCs that would be affected by wall mpture can fulfill their intended function, maintaining the consequences of previously evaluated accident the same.
The new pressure relief damper and excess-flow check damper are safety-related and are l analyzed to function under the conditions created by the MSLB. In addition, the l dampers and the duct they are installed in have been analyzed to assure no failure will occur during an Operating Basis Earthquake (OBE) or Safe Shutdown Eanhquake (SSE).
Based on an analysis of potential failure modes in accordance with ANSI /ANS-58.9-1981, " Single Failure Criteria for Light Water Reactor Safety-Related Fluid Systems",
Paragraph 4.1, the active function of the pressure relief damper and excess flow check damper are considered exempted from consideration of single failure. The principles governing operation of the dampers are simple and direct and not subject to change or deterioration with time, similar to the function of a code safety relief valve and a swing check valve. With periodic testing of the dampers, continued reliable performance is assured.
ATTACHMENT B (Page 4 of 7)
SIGNIFICANT HAZARDS CONSIDERATION The dampers are designed and set so that the pressures created by normal ventilation flow changes do not cycle the dampers, and thus the new dampers do not create the possibility of a new or different kind of accident from any accident previously evaluated.
Adrninistrative controls will be in place prior to implementation of this change to assure the testing and maintenance is periodically performed in accordance with vendor I
reconunendations. These dampers will be included as equipment required to be monitored / maintained, because the function performed by the dampers is within the scope of the Maintenance Rule,10 CFR 50.65.
Therefore, the proposed changes do not create the possibility of a new or different kind l of accident from any accident previously evaluated. I 1
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ATTACHMENT B (Page 5 of 7)
SIGNIFICANT HAZARDS CONSIDERATION Does the change involve a significant reduction in a margin of safety?
Originally, no masonry walls were evaluated for HELB pressurization effects, because the walls were considered protected by the isolation dampers. However, the original design methodology for masonry did include load combinations including P :
i Abnormal 1.0D + 1.0L +1.5P, Abnormal / Severe Environment 1.0D + 1.0L + 1.25P, + 1.25Eo Abnonnal/ Extreme Environment 1.0D + 1.0L + 1.0P, + 1.0E,,,
Where D is Dead Load; L is Live Load; P is pressurization due to HELB; Eo is !
Loads generated by the Operating Basis Earthquake (OBE); an E , is Loads generated by the Safe Shutdown Earthquake (SSE).
The current reevaluation was required due to determination that some block walls in the LaSalle Auxiliary Building are affected by a transient pressurization due to a MSLB. The specific changes from the original analyses involve the following for loads and load combinations:
- 1. Abnormal:
1.0D + 1.0L + 1.0 PnELB
- 2. Abnormal / severe environmental:
1.0D + 1.0L + [(1.1 Eo) 2 + 1.0 Putts2]i/2
- 3. Abnormal / extreme er vironmental:
1.0D + 1.0L + [1.0 Ess2 + 1.0 Pasta2 ]i/2 Where:
- 1) Pnets is the short-term differential pressurization load on the VR plenum masomy walls resulting from non-instantaneous opening / closure of the protection dampers.
- 2) The Load Factor on pressure due to HELB is 1.0 for all cases.
- 3) The Ioading Combination of pressure and seismic is the Square Root of the Sum of Squares (S.RSS).
l ATTACHMENT B (Page 6 of 7)
SIGNIFICANT HAZARDS CONSIDERATION
)
LaSalle has relected the proposed load combinations in consideration of the followmg: ;
i e Isolation, check, and relief dampers protect the walls; therefore the (
pressurization effects are not sustained, but are transient in nature. l
. The transient pressurization effect (Pans) is derived from a conservative detailed analysis of an instantaneous HELB combined with non-instantaneous damper opening / closure. Due to the precise nature and conservatism of this HELB analysis, there is little uncertaintyin Paus. Therefore a load factor of 1.0 l is used for all abnormal load combinations. )
Puus is a short duration, dynamic load. Accordingly, the seismic and transient l HELB pressurization loads are combined using the Square Root of Sum of the l Squares (SRSS) method because the peak effects of these dynamic loads are l unlikely to occur simultaneously. This combination method is used in the analysis of other components such as component supports.
The proposed load combinations accordingly provide a conservative basis for i reassessment of the VR exhaust plenum masonry wall systems. I In regards to the masonry acceptance criteria, the original acceptance criteria used for this condition are the National Concrete Masonry Associations (NCMA) " Specification l for the Design and Constmetion of Load Bearing Masonry- 1979' allowable stresses l times a 1.67 factor. These allowable stresses correspond to stress equal to the modulus of rupture (fr) of the masonry divided by a factor of safety of 3.35. During resiews to address masonry wall issues per NRC IE Bulleting 80-11, six walls did not meet this acceptance criteria. The acceptance criteria used for these walls was for fr values determined from testing at Clinton Power Station divided by a factor of safety of 2.5.
This acceptance criteria was accepted by the NRC for LaSalle in Supplement 5 of NUREG 0519, Safety Evaluation Report related to the Operation of LaSalle County Station, Units 1 and 2. The VR exhaust plenum walls will use the same acceptance criteria for the transient HELB pressurization cases.
The minimum masonry safety factor for the LaSalle Unit 2 walls affected by the HELB loads range from 2.6 to 3.1 with one wall having a safety factor of 4.9.
Masonry wall steel support . members were originally designed for this condition elastically to the American Institute of Steel Construction's (AISC) " Steel Construction Manual- Seventh Edition" allowable stresses times a 1.6 factor. In the reassessment of these members due to the transient HELB pressurization, elasto-plastic behavioris allowed (with a ductility ratio limit of 10). It is appropriate to consider them similar to high-energy line break systems that will maintain their integrity as they absorb the energy of the incidental pressure excursion.
High-energy line breaks are discussed in Section 3.6 of the UFSAR. The discussion in this section focuses on the design of pipe whip restraints, and in Table 3.6-6 acceptance criteria are provided. This table shows that the energy absorbing portions of the pipe whip restraint are allowed to go plastic, thereby absorbing energy. While Table 3.6-6 of
1 ATTACHMENT B (Page 7 of 7)
SIGNIFICANT HAZARDS CONSIDERATION the UFSAR deals with energy absorbing portions of the pipe whip restraints, wide-flange shapes are not addressed. Wide-flange shapes absorb energy through flexural deformations.
Guidance on appropriate acceptance criteria for flexural members is provided in l Appendix A to SRP 3.5.3, " Barrier Design Procedures." This appendix indicates that for tension due to flexure in structural steel members, a ductility ratio value not to exceed 10.0 is acceptable. SRP 3.8.4, paragraph III.5 also notes that at some localized points on the structure, the allowable stresses specified for " structural steel" may be exceeded, t provided that integrity of the structure is not affected.
Note that only one of the Unit 2 walls affected by these HELB loads required the use of j the elasto-plastic acceptance criteria for two structural steel members.
)
In summary, these alternate criteria for reassessment of the integrity of the LaSalle Reactor Building Ventilation Exhaust Plenum masonry walls in conjunction with the J design changes adding a pressure relief damper, an excess flow check damper and masonry wall support steel changes, assures that the walls will maintain their integrity ,
during a MSLB. The safety factor is reduced; however, the walls have sufficient strength and safety margin to maintain structural integrity and thus perform their intended safety function during the pressurization transier*. due to a MSLB accident.
l Therefore, these changes do not involve a significant reduction in the margin of safety. j i
Therefore, based upon the above evaluation, Comed has provided evidence that can be used to I determine that these changes involve no significant hazards consideration. )
I
ATTACHMENT C ENVIRONMENTAL ASSESSMENT l
Commonwealth Edison (Comed) Company has evaluated this proposed operating license amendment request against the criteria for identification of licensing and regulatory actions requiring environmental assessment in accordance with 10 CFR 51.21. Comed has determined that the proposed license amendment request meets the criteria for a categorical exclusion set forth in 10 CFR 51.22(c)(9) and as such, has determined that no irreversible consequences exist in accordance with 10 CFR 50.92(b). This determination is based on the fact that this change is being proposed as an amendment to a license issued pursuant to 10 CFR 50 that changes a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, or that change an inspection or a surveillance requirement, and the amendment meets the following specific criteria:
(i) The amendment involves no significant hazards consideration.
As demonstrated in Attachment B, this proposed amendment does not involve any significant hazards consideration.
(ii) There is no significant change in the types or significant increase in the amounts of any effluent that may be released offsite.
As documented in Attachment A, there will be no change in the types or significant increase in the amounts of any effluents released offsite.
(iii) There is no significant increase in individual or cumulative occupational radiation exposure.
The proposed changes will not result in changes in the operation or configuration of the facility.
There will be no change in the level of controls or methodology used for processing of radioactive effluents or handling of solid radioactive waste, nor will the proposal result in any change in the normal radiation levels within the plant. Therefore, there will be no significant increase in individual or cumulative occupational radiation exposure resulting from this change.
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ATTACHMENT D SKETCH OF TURBINE BUILDING (VT) and MAIN STEAM TUNNEL (VR) AIR RETURN RISERS (The attached sketch provides a physical representation of the node volumes I shown in the Nodal Diagram shown in Attaciunent G. This sketch is of LaSalle Unit 1. LaSalle Unit 2 is a mirror image of Unit 1, with the Vent {
l Stack area common between Units 1 and 2.)
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OVERSIZE DOCUMENT PAGE(S) PULLED SEE APERTURE CARD FILES '
1 APERTURE CARD / PAPER COPY AVAILABLE THROUGH
. . . . . . . . . . .NRC FILE CENTE NUMBER OF OVERSIZE PAGES FILMED ON APERTURE CARD (S)
ACCESSION NUMBERS OF OVERSIZE PAGES:
910512030boI e
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ATTACHMENT E '
MASONRY WALL DESIGN / CONSTRUCTION DESCRIPTION
I Attachment E (Page 1 of 3) I Masonry Wall Design / Construction Description !
LOCATION The block walls that comprise the boundaries of the VR Exhaust Fan and Filter Rooms in Units 1 and 2 are shown on drawings A-192, A-193 and A-198. These walls are identified by the following Equipment Pan Numbers (EPNs):
EPN in EWCS (Current Comed No.) (Original S&L No.)
1WAA786-008 Al-786-8 1WAA786-009 A1-786-9 1WAA786-011 Al-786-11 2WAA786-012 A2-786-12 ~
2WAA786-013 A2-786-13 ' i 2WAA786-020 A2-786-20 I IWAA796-001 Al-796-1 l 1WAA796-002 Al-796-2 j 2WAA796-001 A2-796-1 l 2WAA796-002 A2-796-2 l Plan views and typical wall elevations for these walls are shown in attached Figures 1 through 7.
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FUNCTION The walls affected by this HELB pressurization are passive components that form an enclosure that houses the VR exhaust fans, filters, and heat recoverf coils. None of the VR components located in the plenum are safety-related. The walls themselves are designated safety-related only because their failure could impact adjacent safety-related components (these components include VC ductwork and several safety-related conduits). Therefore, the wall's safety-related function is to remain in place and not impact / affect any adjacent plant components. The reassessment is to evaluate the ability of the walls to withstand pressurization effects without losing their integrity.
l Attachment E (Page 2 of 3)
Masonry Wall Design / Construction Description ,
I CONSTRUCTION i
All of these walls are 12-inch nominal width, single wythe, running bond, of hollow concrete masomy block with continuous truss type horizontal joint reinforcement at every other course.
All of the walls have a gap with flexible joint filler at the top to isolate them from the floor !
above. There is no venical reinforcement in these walls, and the cells are not grouted. These l walls were built under specificationJ-2598, Division 4, which specifies the following materials:
Hollow concrete block:
Type I, Grade N-I per ASTM C90 with a minimum face shell thickness of 1%"
Monar:
Type M per ASTM C270 Horizontal Reinforcement: l Galvanized heavy duty truss type with 3/16" diameter side rods and number 9 cross rods per ASTM A82 The walls are constructed with 3/8" thick, fully bedded mortar joints on all webs and faces (horizontal joint) and 3/8" shoved joints of fully buttered venical surfaces of face shells (vertical joint).
Vertical steel members (interior to the walls or at the wall's face) have been provided to suppon i the walls for out-of-plane forces. The masoruy typically spans horizontally between these steel members. The suppon members (often called block wall columns) span vertically between the floor and ceiling carrying the horizontal reactions from the masonry. The support members are typically attached to the floor with concrete expansion anchor assemblies, and to steel beams at its top with vertically slotted connections (such that no venicalload from the floor above is transmitted through these members). All steel members added to provide support to the block walls were installed under the same specification (J-2598, Division 5, Section 5-1 " Miscellaneous Metalwork and embedded Work"). This section states that all material shall be carbon steel per ASTM A36.
Attachment E (Page 3 of 3)
Masonry Wall Design / Construction Description APPLICATION OF CLINTON'S STATION MASONRY WALL TEST DATA TO LASALLE COUNTY STATION MASONRY WALLS The NRC approved Comed's additional analyses to assess the conservatism of the wall design and the applicability of the results from test data obtained at the Clinton Power Station (50-461 and 50-462) for the 6 walls per Unit that were not meeting the NCMA acceptance criteria.
Comed concluded that the Clinton test data are applicable to LaSalle masonry walls because of the similarity of the following parameters:
The masonry walls at LaSalle County Station have been built with:
a) Full mortar bedding of the units, l b) Runmng bond construction, c) Continuous truss-type joint reinforcement every second course, d) Masonry block units conforming to ASTM C-90 for hollow units and ASTM C140 for solid l units, )
e) Type M monar conforming to ASTM C270, and l f) 3/8" thick monar joints.
1 Comed further supported the above conclusion by attesting that the masonry wall construction l at LaSalle and that at the Clinton tests are essentially identical.
The masonry walls for which this acceptance criteria was previously accepted are the same as all of the masonry walls at LaSalle County Station with respect to design and construction.
Therefore, the tests conducted at Clinton apply to the VR exhaust plenum masonry walls.
REFERENCES SpecificationJ-2598, Divisions 4 and 5 and Form 1727 Drawings: A-1, A-64, A-65, A-176, A-192, A-193, A-198 w -
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ATTACHMENT F
SUMMARY
OF REASSESSMENT CALCULATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WALLS l
l
ATTACHMENT F (Page 1 of11)
SUMMARY
OF REASSESSMENT CALCULATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WALLS INTRODUCTION:
Calculation L-002254 provides the design basis evaluations for the following 5 Auxiliary Building Unit 2 VR Exhaust Room block walls for reshting the accident differential pressures due to Main Steam Line Break (MSLB):
- 1. Block Wali No. A2-786-12
- 2. Block Wall No. A2-786-13 {
- 3. Block Wall No. A2-786-20
- 4. Block Wall No. A2-796-1
- 5. Block Wall No. A2-796-2 These walls are made of hollow units conforming to ASTM C90 with full monar bedding for the units and running bond construction. The monar joints are 3/8" thick type M mortar conforming to ASTM C270. In addition, every seccnd course is provided with continuous truss-type joint reinforcement. The construction of the walls is discussed in Attachment E.
Original analyses and design of these walls considered the loads, load combinations, and allowable stresses shown in Table 3.C-1 of Attachment 3.C of the LaSalle 'UFSAR. The allowable stresses in this Table are based on the NCMA allowables. However, differential pressures resulting from a MSLB were not postulated for these walls and thus, the original analyses of these walls did not consider differential pressures due to MSLB.
Pressure loadings are obtained from Calculation L-001441, which is the supporting transient pressurization calculation for the VR exhaust ductwork and equipment rooms. Calculation L-001441 is summarized in Attachment G, but the resulting differential pressure graphs are included in this calculation summary. This calculation is prepared based on the Unit 1 design parameters. The Unit 2 VR exhaust plenum is essentially a mirror image of the VR exhaust plenum for Unit 1. Based on the comparison of the Units 1 & 2 considering the stmeture geometry, ductwork, flow areas, initial conditions, volumes for various nodes, and the similarity of the new pressure relief and excess flow check dampers of Units 1 & 2, the pressurization results of Unit 1 are equally applicable to the Unit 2. This comparison is documented in Appendix P of calculation L-001441.
The applicable differential pressures for the Unit 2 walls are based on the calculated differential pressures for the corresponding Unit I walls.
Calculation L-002254 is specifically for the Unit 2 walls. The Unit 1 calculation has not been completed, but it will be done using the same assumptions, methodology, and acceptance criteria.
Provided below is a description of the loads, load comb: nations, methodology, and the acceptance criteria that were used in these design basis evaluations. Also included is a summary of the results.
1 l
ATTACHMENT F (Page 2 of11) l
SUMMARY
OF REASSESSMENT CALCUIATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WALLS A. METHODOLOGY:
The masonry wall design basis evaluations consists of the following:
- Evaluation of masonry blocks ;
- Evaluation of supponing structural steel including their connections j l
Reactions from the suppon steel for masonry walls are resisted by the structural steel beams, i concrete slabs, or concrete walls. These supporting members are also evaluated for these reactions. This evaluation is documented in Calculation L-002354. Evaluationof these members is in accordance with LaSalle UFSAR design requirements.
A.1 Evaluation of Masonry Blocks A.1.1 Out-of plane analysis Masonry blocks are in general considered to span horizontally between the support steel and are evaluated considering simply supponed spans. However, in some local areas around doors or penetrations through the masoruy wall, masonry blocks are considered to behave as simply supponed vertically spanning walls, venical cantilevers, or horizontal cantilevers. l l
The differential pressure loads on these walls are dynamic loads. Therefore, for an equivalent i static analysis, the peak differential pressures are multiplied by appropriate Dynamic Load I
Factors (DLF).
When calculating loads, in addition to wall self-weight and pressure loads, based on the available wall surveys, appropriate attaciunent loads are selected. The selected attachment loads are conservatively positioned at the most critical locations within a given span to produce maximum moments and shears. Stresses due to the maximum moment and maximum shear within the masonry block are calculated. ,
i I
Due to connectivity between some of these walls, pressure and seismic loading on a given wall may induce in-plane loads within an abutting wall. Therefore, when calculating maximum masonry stresses additional stresses due to these in-plane loads are added to the calculated 1 stresses due to out-of-plane loads. l Maximum total masonry block stresses are determined by summation of maximum stresses due to out-of-plane and in-plane loads and are checked against the allowable stresses.
Calculated reactions from the out-of-plane analyses of the masonry block are used for evaluation of supporting steel and their connections.
ATTACHMENT F (Page 3 of11) 1
SUMMARY
OF REASSESSMENT CALCULATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WALLS A.1.2 In-plane Analysis:
In-plane analysis is required to ensure that the masonry walls are not sliding and/or overturning. ;
If the masonry wall is found to be subject to sliding and/or ovenurning, the supporting masonry (
structural steel is utilized to provide the resistance required to prevent sliding and/or overturning j of thewall.
j l
Similar to the out-of-plane analysis, in addition to wall self-weight, appropriate attachment loads based on the available wall surveys are selected. Both wall and attachment loads are excited in the in-plane direction of the wall and combined with the loads due to pressure and seismic from i i
abutting walls. Furthermore, the walls are considered to be subjected to vertical upward excitation. Combination of horizontal and vertical seismic excitations is based on 100%,40%
mle (i.e.100% vertical and 40% horizontal excitations, or 40% vertical and 100% horizontal excitations).
B. Evaluation of supporting structural steel including their connections l
l The supponing masonry structural steel members and their connections are evaluated for the j loads transmitted by the masonry block for the three Abnormal, Abnormal / Severe i Environmental, and Abnormal / Extreme Environmental load combinations. The loading on l these members and their connections are obtained considering the results from both the out-of-plane and in-plane analyses of the walls.
I In general, conservatively, the members are evaluated for the loadings resulting from the maximum a'osolute peak differential pressures (i.e. greater of the positive or negative peak pressures) using the allowables based on the maximum unbraced compression flange lengths.
However, where needed, this conservatism is removed.
l Maximum total stresses are determined by summation of maximum stresses due to loads from )
out-of-plane and in-plane analyses of the walls and are checked against the allowable stresses.
Where the stresses are found to ex:eed the allowable stresses, appropriate modifications are designed and issued for construction to lower the stresses below the allowable stresses.
ATTACHMENT F (Page 4 of11)
SUMMARY
OF REASSESSMENT CALCULATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WALLS C. DIFFERENTIAL PRESSURES DUE TO MSLB:
The following plots show the differential pressures due to Main Steam Line Break (MSLB) for these walls. For all these walls, the induced differential pressures are transient and the peak positive or negative differential pressures occur within the first 0.5 seconds and the pressures diminish to a relatively negligible pressures within a second or two.
Differential Pressure Due to MSLB Block Wall A2-786-13 1.0 -- (Max. = 0.9436 psi, Min. = -0.4100 psi)
I 0.8 T 0 6 ,. i S ]
l 0.4 0.2
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l 0.0
-0.2 ,
5 1.5 0 2.5 30 3.5 4.0 4.5 50 g
Q
-0 4 .
)
-06 Time (Seconds) f i
I
ATTACHMENT F (Page 5 of 11)
SUMMARY
OF REASSESSMENT CALCULATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WALLS Differential Pressure Due to MSLB Block Wall A2 786-20 1.2 . (Max. = 0.9995 pai, Min. = -0.3922 psi) 1.0 ,
{ 0.8 ,
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, E 04. f o.
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g 0.0 , - _-
gi 0.0 0 1. .
0 .5 0 3.5 40 4.5 5.0
-0.2 .
-0.4 -
Time (Seconds)
.+-~,%- ....,%.- ..s _ .--
Differential Pressure Due to MSLB Block Wall A2-786-20 1.0 . (Max. = 0.9727 psi, Min. = -0.4078 psi)
- 08. l
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@ 0.0 0 1. 0 .5 .0 3.5 40 4.5 5.0 l 0.2 .
Q 04
-06 Time (Seconds)
I I
1
ATTACHMENT F (Page 6 of11)
SUMMARY
OF REASSESSMENT CALCUIATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WALIS Differential Pressure Due to MSLB Block Walls A2 786-20 and A2 796-1 (ouside stack room) 1.0 (Max. = 0.9564 psi, Min. = -0.4364 psi) 0.8 .. '
t 1 0.6 l f
l 0.4 i
$ 0.2 1
< 0.0 - , -
-0.2 .
O
-0.4 .
-0.6 .
Time (Seconds)
--.i---------u -4m-- .-4--%.,-++eem- me .h.- - - - - . - - - . , . - . . . . - . . . - - . _. -e.., - -
Differential Pressure Due to MSLB Block Wall A2-796-1 (Inside the stack room) 0.10 (Max. = 0.0795 psi, Min. = -0.2127 psi) 0.05
=
$ 0.00 _ - . - _ . - _ . . - _-_ h- . . _ _
2 0.0 0.5 1.0 1. 2.0 2. 0 5 4.0 4 5.0 E -0 05 !
$ -0.10 .
3
$ -0.15 .
5 -0.20
-0.25 Time (Seconds)
ATTACHMENT F (Page 7 of 11)
SUMMARY
OF REASSESSMENT CALCULATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WALLS
! Differential Pressure Due to MSLB Block Wall A2-796-2 1.2 - (Max. = 1.0012 psi, Min. = -0.2710 psi) l l 1.04 T 0.8 i
S l
0.6 4 l i l 0.44 c.
] 0.2 i i
$ 0.0 e -
! 00 .5 1.5 20 2.5 3.0 35 40 4.5 5.0
-0.4 _
s Time (Seconds) 1 i
Differential Pressure Due to MSLB Block Wall A2-786-12 1.0 . (Max. = 0.9582 pai, Min. = -0.3783 psi)
]
i j 0.8 f i
=
$ 0.6 .
2 E 0.4 .
E E 0.2 .. ' i 3 )
$ 0.0 .
$ 0.0 05 0 .5 .0 3.5 4.0 45 5.0 0 -0.2
-0.4 -
Time (Seconds)
The above differential pressure loads are dynamic (impulsive) loads. In order to account for the l dynamic nature of these differential pressure loads, the peak differential pressures are amplified using appropriate Dynamic Load Factors (DLF).
1 I
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ATTACHMENT F (Page 8 of11)
SUMMARY
OF REASSESSMENT CALCULATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WALLS DLF is dependent upon the differential pressure time history and the natural out-of-plane frequency of the block wall. To determine the DLF, when considering elastic behavior, the pressure time histories for the above differential pressures are normalized (i.e. all pressure values are divided by the peak pressure) and the response spectra corresponding to the normalized
! differential pressures are generated. These response spectra in fact represent the variation of DLF with respect to the natural out-of-plane frequency of the wall. Thus, the applicable DLF for each wall is determined by reading the spectra values for the corresp'onding wall natural out-of-plane frequency.
All masonry block qualification is performed considenng elastic behavior. However, for the supporting structural steel, if needed, plastic hinge formation is allowed for those steel members j that can develop their full plastic moment capacities. For such members, consideration of elastic >
behavior is no longer applicable and the DLF is recalculated using Figure 2.26, Maximum l l response of elasto-plastic one-degree systems (undamped) due to equilateral triangular load l pulses, provided in Introduction to Structural Dynamics byJohn M. Biggs. 1 The elasto-plastic DLFs have been calculated considering a single-degree undamped system, I which is assumed to have a bilinear resistance function (see Figure 1). The DLFs for the LaSalle ,
case have been computed such that the ratio of the maximum response (ym) to the elastic 1 response (ya) does not exceed 10 (i.e. a maximum ductility ratio of 10). j i
l l
l i
Resistance n i
)
l l r l
l l l l l !
I I m l l
4 Ym Response Yel 4F(t) l
' c) Model b) Bilineer Resistance Function ,
l FIGURE 1-ELASTO-PLASTIC SYSTEM USED TO COMPUTE DLF !
l l
[
ATTACHMENT F (Page 9 of11)
SUMMARY
OF REASSESSMENT CALCULATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WAL.LS D. LOAD COMBINATIONS:
D.1. MasonryWall Evaluation The differential pressures due to MSLB only affect the Abnormal, Abnormal / Severe Environmental, and Abnormal / Extreme Environmentalload combinations. Based on the existing analyses for these walls, these walls are adequate for all other load combinations stipulated in Table 3.C-1 of Attachment 3.C of the LaSalle UFSAR. Thus, the design basis evaluations contained in calculation L-002254 are limited to the three load combinations noted above. The loads, load factors, and method of combination ofloads within these three load combinations are shown below:
- 1. Abnormal:
D + L + 1.0 Pana
- 2. Abnormal / Severe Environmental:
D + L + [ (1.10Eo)2 + (1.0Psas)2 ] 1/2
- 3. Abnormal / Extreme Environmental:
D + L + [ (1.0E,,)2 + (1.0Psas)2 ] i/2 Where; D- Deadload L- Live load Paas - Differential pressure due to HELB in Main Steam Tunnel (Including an appropriate DLF)
Eo - Loads due to operating basis eanhquake (OBE)
(Due to seismic excitation of self-weight and wall attachments) i Es, - Loads due to safe shutdown earthquake (SSE)
(Due to seismic excitation of self-weight and wall attachments) i D.2. Supporting Structural Steel Evaluation Evaluation of the supponing stmetural steel is based on the same loads and load combinations noted above for the masomy block evaluation, except that the load factor for Eo in the Abnormal / Severe Environmental load combination is 1.0. This is consistent with the load combinations in Table 3.8-9 of LaSalle UFSAR.
ATTACHMENT F (Page 10 of11)
SUMMARY
OF REASSESSMENT CALCUIATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WALLS E. ACCEPTANCE CRITERIA (ALLOWABLE STRESSES) FOR MASOh%Y BLOCK:
With the exception of tensile flexural stresses, all allowable stresses are limited to 1.67 times the NCMA allowable stresses as stipulated in Table 3.C-1 of Attachment 3.C of the LaSalle UFSAR for the three load combinations under consideration.
For flexural tensile stresses, allowable stresses are calculated as follows:
Allowable flexural tensile stress - fr / 2.5 Where; fr - Modulus of Rupture based on Clinton Station test data Since the allowables based on 1.67 times the NCMA allowables provide safety margins in excess of 2.5,it can be concluded that using the above allowable stresses, a minimum safetymargin of 2.5 against block failure is available.
i F. ACCEPTANCE CRITERIA (ALLOWABLE STRESSES) FOR SUPPORTING STRUCTURAL STEEL:
Since pressure loading due to MSLB is an impulsive load, for low grade steel (i.e. steel with a yield strength not exceeding 40 ksi), allowable flexural, compressive, and tensile stresses that are !
a function of material yield strength are allowed to be increased by a Dynamic Increas4. Factor (DIF) of 1.20. Note, no DIF is allowed for bolt or weld allowable stresses.
F.1. Members:
i F.1.1 Equivalent static pressure load is based on clastic DLF As long as no plastic hinge is fonned within the member, the member behavior is considered l elastic and the equivalent static pressure loading is calculated considering elastic behavior as l described earlier.
i F.1.1.1 Member can not develop its full plastic moment capacity The allowable stresses are limited to SSE allowables using elastic section modulus.
F.1.1.2 Member can develop its full plastic moment capacity For those members where full plastic moment capacity can be developed, allowable stresses based on plastic section modulus are limited to DIF*0.95Fy (where; DIF - 1.20 for low-grade steel, Fy - Yield strength). If the calculated stresses exceed the above limit, elasto-plastic behavior consideration is allowed (see Section F.1.2 below).
ATTACHMENT F (Page 11 of11)
SUMMARY
OF REASSESSMENT CALCULATION of the UNIT 2 VR EXHAUST PLENUM MASONRY WALLS F.1.2 Equivalent static pressure load is based on elasto-plastic DLF When stresses due to consideration of equivalent static pressure load cause formation of a plastic hinge within the member (Provided that the member can develop its full plastic moment capacity), the member behavior is no longer elastic and the equivalent static pressure load is recalculated considering elasto-plastic DLF. Elasto-plastic DLF is calculated considering a maximum allowable ductility ratio of 10 (See section C above for additional discussion). In such cases, the calculated stress based on elasto-plastic behavior and using plastic section modulus is limited to DIF*0.95Fy.
When, elasto-plastic behavior is used, the connections of that member are evaluated for 1.10 times the loading which produces full plastic moment of DIF*Fy *Z.
l F.2. Connections: l Allowable stresses for connections of the masonry support steel are the SSE allowables.
F.3. CEA Plates:
Allowables for concrete expansion anchors are the SSE allowables.
G.
SUMMARY
OF RESULTS: i The following table provides a summary of the design basis evaluation results:
WallNo. I l
A2-786-12 A2-786-13 A2-786-20 A2-796-1 A2-796-2 Minimum Masonry 4.9 2.8 2.6 2.9 3.1 Safety Factor Required use of No Yes No No No Elasto-Plastic Behasior (2 members)
Note: The required modifications for the masoruy and supporting structural steel are issued for construction in DCN 001636S and DCN 001637S.
l l
4 I
i 4
l l
ATTACHMENT G l l
l
SUMMARY
OF TRANSIENT PRESSURIZATION CALCULATION OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS i
I 1
I i
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1 i
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ATTACHMENT G (Page 1 of 13) j
SUMMARY
OF TRANSIENT PRESSURIZATION CALCULATION OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS BACKGROUND Various HVAC ducts of the VR systems interface with the Main Steam Tunnel (MST) at the LaSalle County Station. These ducts also directly interface with other locations within the plant including Reactor Building general areas and HVAC exhaust equipment rooms (filters, heat recovery coils, and exhaust fans). In the event of a postulated Main Steam Line Break (MSLB) in the MST and subsequent steam release, the tunnel will pressurize and drive steam into the interfacing HVAC ducts. All such ducts are equipped with check dampers, which will close either on reverse flow (for ducts supplying air to the MST), or on excess flow (for ducts with airflow leaving the MST). The closure time of these check dampers determines the amount of I steam released past the dampers and subsequent response (pressurization, increased temperatures and humidity, etc.) of the ducts and interfacing areas. Calculations were performed to model the MSLB transient and to determine the very short (0.1 to 03 second) but finite closing times of the check dampers and to provide design input for follow-on calculations (e.g.,
wall pressurization for structural analysis).
The analysis assumes an excess flow check damper (1(2)VR91Y) and a pressure relief damper (1(2)VR90Y) were installed in the VR exhaust ductwork leading from the MST to the VR Exhaust Equipment room downstream of the secondary containment isolation dampers (1(2)VR05YA/B). The pressurization analysis modeled the closing of check dampers and the opening of the relief dampers.
The IVR90Y pressure relief damper was installed during Unit 1 forced outage L1F35. The IVR91Y excess flow damper will be installed prior to startup from L1R08. The Unit 2 dampers (2VR90Y and 2VR91Y) were installed prior to startup from L2R07. l The Unit 1 COMPARE model for the VR transient analysis was assessed to determine whether !
the results for this Unit 1 model are applicable for Unit 2. The basis of the assessment was node i by node and junction by junction comparisons between Unit 1 and Unit 2. These comparisons were made by examining the applicable Unit 1 and Unit 2 drawings. ;
i It was determined that the Unit 1 COMPARE model for the VR transient analysis is representative of Unit 2. Therefore, the transient analysis results based on the Unit 1 model are applicable to Unit 2.
SCOPE ,
A calculation of the pressurization of the VR exhaust ductwork and equipment rooms following postulated full guillotine rupture of one Main Steam line in the MST was included as a part of )
station calculation L-001441, Rev. 8. Through dynamic modeling of the pressure relief damper (1(2)VR90Y), the excess flow check damper (1(2)VR91Y), and other components (e.g., blowout ;
panels, hinged panels) the computer model included features to examine the downstream pressurization of the ductwork and walls as well as the steam release and emironmental response of the general areas of the auxiliary building.
i
)
ATTACHMENT G (Page 2 of 13)
SUMMARY
OF TRANSIENT PRESSURIZATION CALCULATION OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS METHODOLOGY The pipe break transient following a postulated MSLB in the MST is modeled using industry standard approaches and computer codes. The plant areas of interest (MST, exhaust ductwork, auxiliary building general areas, VR exhaust equipment room, etc.) are modeled as nodes with connecting junctions or paths, creating a node-path model. Each node is described by a net free volume and initial conditions of pressure, temperature, and humidity. Each path is described as connecting two nodes with an associated flow area, entrance and exit loss coefficients, and inertia term. Given the node-path model, the industry standard code COMPARE is used in modeling the transient.
The transient is driven by the mass and energy release of the postulated pipe break. The limiting transient is taken as the design basis transient for MST pressurization. This transient results in ,
the maximum pressurization of the tunnel and any interfacing ductwork.
Guidelines for the node-path and mass and energy release modeling are taken from industry standard documents such as SRP 6.2.1.2 and ANSI /ANS-56.10-1982.
The COMPARE code allows for time dependent modeling of junction areas. A check damper l that closes during the transient (or a relief damper that opens) requires such modeling.
However, the time dependent area is user input and not dynamically computed.
Time dependent damper areas are directly dependent on the transient. The transient flow and differential pressure across the check damper (/ relief damper) determine the closing force l
(/ opening force) which in turn accelerates the damper closed (/ opened). Resisting the ;
accelerating forces is the moment ofinenia of the moving pans of the damper. l l
Since the COMPARE code does not include the capability to dynamically compute the damper closing (/ opening), this closing (/ opening) is computed separately based on COMPARE results.
Thus an iterative approach was required to complete the analysis.
J l
1 ATTACHMENT G (Page 3 of 13) '
SUMMARY
OF TRANSIENT PRESSURIZATION CALCULATION OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS l
1 The steps are as follows:
. Select an area versus time for flow past the excess flow check damper (1(2)VR91Y) and i relief damper (1(2)VR90Y).
. Using this area compute the junction flow and flow density versus time using the COMPARE code (this analysis also provides pressurization and other parameters of l interest). i 1
. Using COMPARE Results for junction flow velocity and density, separately determine the area versus time curve for the check damper (/ relief damper), considering damper moment i of inenia, latching force, closing angle, and drag forces due to time dependent flow past the damper. This step is performed by spreadsheet integration of the laws of angular motion (Newtonian mechanics).
. Using this newly computed area versus time curve for the check damper (/ relief damper),
recompute the COMPARE transient to obtain a new set of flow and flow density data for use in computing time dependent damper area.
. Repeat the process until the area versus time assumed as input to the COMPARE analysis is ,
converged to the area versus time result of the dynamic damper closing (/ opening) l calculation.
Once converged, COMPARE results for transient pressure, temperature, humidity, and radioactive steam release are provided as input to various follow-on analyses.
DESIGN INPUT Design input is based on controlled station drawing and documents.
Mass and energy release for the limiting MST HELB is based on the design analysis for tunnel pressurization. In this analysis, one MSLB is assumed to be added to one FWLB caused as a direct consequence of pipe whip from the initial MSLB. Note dut sine dxfiukaner nicasefam dx posadatal FWLB is saneratalliquid, dx c)Jat on MSTpnsswizztias in dx dat tems (q to 0.3 sa) is niinal.
Node and junction parameters are based on station layout drawings.
Damper parameters are based either on vendor drawings or,in the case of the new dampers (1(2)VR90Y,1(2)VR91Y), are based on specified values from the purchase specifications.
The node path model is provided in the following diagram.
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ATTACHMENT G (Page 5 of 13)
SUMMARY
OF TRANSIENT PRESSURIZATION CALCULATION OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS ]
I l
Node parameters are listed in Table 04.1 and 04.2 below.
Table 04.1: Volume Node Initial Conditions Volume Node Pressure Temperature Relative humidity (psia) (F) 1 14.7 212.0 C.545 2 14.7 212.0 0.545 3 14.7 212.0 0.545 4 14.7 212.0 0.545 l l
5 14.7 122.0 0.23 6 14.7 122.0 3.23 7 14.7 122.0 0.23 14.7 l 8 1.22.0 0.23 9 14.7 122.0 0.23 10 14.7 122.0 0.23 11 14.7 122.0 0.23 12 14.7 122.0 0.23 13 14.7 122.0 0.23 l 14 14.7 122.0 0.23 15 14.7 122.0 0.23 16 14.7 106.0 0.34 17 14.7 106.0 0.34 18 14.7 122.0 0.23 19 14.7 122.0 0.23 20 14.7 122.0 0.23 21 14.7 106.0 ^ 's 22 14.687 122.0 _ 0.23 23 14.7 122.0 ,
0.23
ATTACHMENT G (Page 6 of 13)
SUMMARY
OF TRANSIENT PRESSURIZATION CALCULATION OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS Table 04.2: Volume Description and Geometry Volume _ _ _
Description Volume (ft3) Elevation (ft) 1 Upper MST, El. 763'-4" to 703-6", col.11-13, row J-L 48746 703.5 2 First Part of Lower MST, El. 687', col.1C-13, row J-R 64764 687 3 Second Part of Lower M's'l', EL. 687', downstream of 46623 687 blowout panel 4 Condenser Cavity 1230000 663 5 Reactor Building Vent Return Air Riser, 2280 789 EL. 773'- 805'-4" 6 __
Atmosphere 1.0E10 663 7 72" Duct Upstream of the center line of 1(2)VR05YA 125 791 8 72" Duct between the center lines of 1(2)VR05YA & 295 791 1(2)VR05YB 9 72" Duct between the center line ofi(i)VR05YB and the 130 791 centerline of the 72" excess flow damper 10 Duct Transition ~
480 791 11 Volume between damper 1(f)VR07Y a&fFilter 5alk 2200 804 12 Volume between Filter Bank & Heat Recovery Coil 2050 806 13 Fan Room 6400 800 14 Vent Stack 26900 810 15 Vent Stack 78350 960 16 Volume surrounding the 72" Duct, El. 786'-6" col.12-13, 17000 800 row L-!
17 Volume bounded by col.10-13.2, row L-N, and col.10-12, 83900 800 row J-L, El. 786'-6" 18 Reactor Building Vent Return Air Riser, 890 807 EL. 805'-4" - 810'-4" 19 Reactor Building Vent Retum Air Riser, 1328 796 EL. 786'-6" - 805'-4" 20 Reactor Building Vent Retum Air Riser, 1190 833 EL. 810-4" - 850' 21 Lower Ventilation Equipment Area, Unit 1 & Unit 2, EL. 209000 800 786'-6", excludingthe area of nodes 16,17 22 Area Upstream of Check dampers .
1.0E10 663 23 72" Duct between the center line of the 72" excess flow 110 791 damper 1(2)VR91Y and the flow monitor I
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ATTACHMENT G (Page 7 of 13)
SUMMARY
OF TRANSIENT PRESSURIZATION CALCULATION OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS Junction parameters are provided in Table 04.3 and 04.4 below.
Table 04.3: Junction Description Junction Connecting Description Nodes 1 1-2 ,From Upper MST to First Part of Lower MST 2 2-3 From First Pan of Lower MST to Second Pan of Lower MST 3 2-3 4 1-5 from Upper MST to Return Air Riser at EL. 773'- 805'-4" 5 2-22 from First Part of MST to upstream area of Damper 1(2)VR11Y-14Y 6 1-22 from Uyper MST to upstream area of Damper 1(2)VR10Y 7 5-22 From Retum Air Riser, EL. 7'/3'- 805'-4" to upstream area of damper 1(2)VR09Y 8 3-4 from Second Part of Lower MST to Condenser Cavity 9 20-6 [ rom Retum Air Riser, EL. 810'-4" - 850'to Atmosphere, through a Elowout Panel 10 4-6 from Condenser Cavityto Atmosphere 11 19-7 from Retum Air Riser, EL. 786'-6" - 805-4" to 72" Duct 12 7-8 flow through the Damper 1(2)VR05YA 13 8-9 Plow through the Damper 1(2)VR05YB 14 23-10 pow through the Flow Monitor 1/2FE-VR002 15 10-11 flow through the Damper 1(2)VR07YA-D 16 11 12 Flow through the Filter Bank 1(2)VR02F 17 11 12 (not used) 18 12-13 flow through_the Heat Recovery Coil 1(2]VR04A 19 13-14 from the Fan Room to Vent Stack, through the Fans 1(2)VR02CA-C 20 14-15 Junction between the stack nodes Node-14 and Node-15 21 15-6 from Stack to Atmosphere .
22 10-16 Flow through Pressure Relief Damper on the Transition Section 23 11-21 Door (not used) 24 12-21 Door (not_used) _
25 16-17 from Volume surrounding the 72" Duct, El. 786'-6" col.12-13, row L J i o Volume bounded by col.10-14, row L-N and Col.10-12, row J-L t
26 5-18 feactor Building Vent Return Air Riser, EL. 773'- 805'-4" to EL. 805'-4" -
E 10'-4" 27 18-19 Reactor Building Vent Return Air Riser, EL 805'-4" 810'-4" to EL. 786'-6" - 805'-4" 28 18-22 actor Building Vent Return Air Riser, EL. 805'-4"- 810'-4" to upstream
, area of damper 1(2)VR08Y 29 18-20 ! Reactor Building Vent Return Air Riser, EL. 805'-4"- 810'-4" to kL. 786'-6" - 805'-4" to EL. 810'-4" - 850'
__30 17-21 ;From volume bounded by col.10-14, row L-N and col.10-12, hwJ-L to Lower Ventilation Equipment AreajJnits 1 & 2). _
31 9-23 Flow through the proposed 72" excess flow damper 1(2)VR91Y
ATTACHMENT G (Page 8 of 13)
SUMMARY
OF TRANSIENT PRESSURIZATION CALCULATION OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS Table 04.4: Junction Parameters Junction Connecting FlowArea L/A K Elevation Nodes (ft2) (1/ft) (ft) 1 1-2 432.00 0.180 2.840 704 2 2-3 310.00 0.240 2.260 696 3 2-3 22.75 0.900 2.730 696 4 1-5 30.00 0.720 1.5 773 5 2-22 37.12 0.555 2.527 697 6 1-22 15.46 1.795 2.316 761 7 5-22 4.66 1.905 2.545 802 8 3-4 241.00 0.340 2.700 696 9 20-6 30.00 0.661 1.048 849 10 4-6 975.20 0.050 2.650 768 11 19-7 28.27 0.252 0.303 791 12 7-8 27.68 0.318 0.368 791 13 8-9 27.68 0.323 0.369 791 14 23-10 28.27 0.157 0.250 791 15 10-11 69.00 0.105 1.379 804 16 11-12 252.00 0.012 27.012 806 17 11-12 0 (not used) 0.012 0.509 806 18 12-13 429.60 0.031 323.745 800 19 13-14 8.74 3.591 3.484 800 20 14-15 452.39 0.227 0.163 810 21 15-6 268.80 0.588 1.288 960 22 10-16 48.00 0.247 1.500 791 23 11-17 21.36 (not used) 0.185 1.500 797 24 12-17_ 21.36 (not used) 0.211 1.500 797 25 16-17 804.34 0.016 1.100 800 26 5-18 70.57 0.352 0.390 805 27 18-19 70.57 0.179 0.316 805 28 18-22 4.66 0.896 1.467 809 29 18-20 30.00 0.813 0.464 815 30 17-21 757.55 0.100 0.028 800 31 9-23 25.78 0.218 0.433 791 l
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l ATTACHMENT G (Page 9 of 13)
SUMMARY
OF TRANSIENT PRESSURIZATION CALCULATION '
OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS Mass and energy release for the postulated failures is provided in the following table.
Table 04.6 Mass and Energy Release Time Description Mass rate Energy Rate (sec) (Ibm /sec) (Btu /sec) 0.0 Forward Steam 6635.73 7.9E6 l
0.11 Fonvard Steam 6635.73 7.9E6 {
1.11 Fonvard Steam 1858.5 2.2E6 4.21 Fonvard Steam 433.65 516.48E3 5.61 Forward Steam 0 0 1000 Forward Steam 0 0 0.0 Reverse Steam 6635.91 7.9E6 )
1.33 Reverse Steam 6635.91 7.9E6 1.33(0 Reverse Steam 5575.5 6.64E6 2.33 Reverse Steam 5575.5 6.64E6 2.33(2) Reverse Steam 1300.95 1.55E6 5.43 Reverse Steam 1300.95 1.55E6 )
6.83 Reverse Steam 0 0 )
1000 Reverse Steam 0 0 0.0 Liquid 0 0 1.11 Liquid 0 0 1 1.110) Liquid 5751.35 3.2E6 i 4.21 Liquid 5761.35 3.2E6 5.61 Liquid 0 0 1000 Liquid 0 0 0.0 Reverse Liquid 0 0 2.21 Reverse Liquid 0 0 2.21(4) Reverse Liquid 17284.1 9.5E6 5.21 Reverse Liquid 17284.1 9.5E6 6.71 Reverse Liquid 0 0
_ 1000 Reverse Liquid 0 0 0.0 Feedwater 20523.72 8.2E6 1.2 Feedwater 20523.72 8.2E6 l 1.2(3) Feedwater 10261.86 4.1E6 1000 Feedwater 10261.86 4.1E6 Notes: (1) Reverse dry steam in 100 feet of steam line has depleted, dry steam based on three times restrictor flow area follows.
(2) 7% steam begins.
(3) Forward liquid flow begins.
(4) Reverse liquid flow begins.
(5) Reverse feedwater flow stops.
ATTACHMENT G (Page 10 of 13)
SUMMARY
OF TRANSIENT PRESSURIZATION CALCUIATION OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS i i
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ASSUMPTIONS l In computing the closing force on the check damper due to air-steam flow past the damper, flow at this point is assumed to be isentropic. This provides a conservative lower bound for the dynamic drag force on the damper. Assuming friction flow at this location would result in a lower pressure on the backside of the damper, resulting in a greater differential pressure and greater closing force.
l RESULTS Results of the converged analysis are used as input to follow-on analyses. Transient pressure results are provided for structural analysis of walls and roof and floor slabs. Transient pressure, temperature, and humidity profiles are provided for analysis of limiting environmental profiles.
Radioactive steam release is provided as input to analysis of radiological releases within the Auxiliary and Reactor buildings.
Specific transient results for analysis of the VR exhaust ductwork are summarized in the following tables.
Table 07.1: Maximum Differential Pressures on the Walls of the Exhaust Equipment l Room and the Fan Room )
1 Between Nodes Description Max. Positive Max. Negative Differential Pressure Differential Pressure (Psid) (Psid) 11-16 Exhaust Equipment Room 0.9436 -0.4100 South Wall (Unit 1),
11-21 Exhaust Equipment Room 0.9995 -0.3922 l 12-21 West Wall (Unit 1) 0.9727 -0.4078 13-21 Fan Room West Wall (Unit 1 ) 0.9564 -0.4364 13 14 Fan Room Nonh Wall (Unit 1) 1.0012 -0.2710 14-21 Vent Stack 0.0795 -0.2127 West Wall (Unit 1) 13-6 Panial Wallin the Fan Room (Unit 1) 0.9582 -0.3783
f ATTACHMENT G (Page 11 of 13)
SUMMARY
OF TRANSIENT PRESSURIZATION CALCULATION I OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS j i
I Table 07.2: Total Steam Water Air Flow through Dampers Junction Description Integrated Flow (Ibm) 5 Damper 1(2)VR11Y/12Y/13Y/14Y 87.6 total four dampers) 6 Damper 1(2)VR10Y 42.0 7 or 28 Damper 1(2)VR09Y/08Y (one damper) 10.1 31 Proposed 72" Excess Flow Damper 1(2)VR91Y 46.5 )
Table 07.3: Maximum Pressure, Temperature, and Relative Humidity l
Volume Description Pressure Temperature Relative l Node (psia) humidity
(*F) 1 Upper MST 41.62 264.62 1.0 2 Lower MST 41.51 269.50 1.0 3 Lower MST 39.35 266.25 1.0 4 CondenserCavity 20.72 218.96 1.0 5 Reactor Building. Vent Retum Air Riser, EL. 773'-805'4" 37.24 257.99 1.0 7 72" Duct Upstream of 1(2)VR05YA 36.86 209.45 1.0 8 72" Duct between 1(2)VR05YA & 1(2)VR05YB 38.86* 214.02 1.0 9 72" Duct Downstream of 1(2)VR05YB 36.86* 262.74 1.0 10 72" Duct Transition 15.71 147.36 0.30 11 Volume between damper 1(2)VR07Y and Filter Bank 15.71 134.73 0.26 j 12 Volume between Filter Bank & Heat Recovery Coil 15.68 133.38 0.24 13 Fan Room 15.66 133.10 0.24 14 Vent Stack 14.78 123.40 0.23 15 Vent Stack 14.70 122.51 0.23 l 16 Volume surrounding the 72" Duct, El. 786'-6" col.12-13, 14.89 109.84 0.34 row L-J 17 Volume bounded by col.10-14, row L-N, and col.10-12, 14.85 108.09 0.34 row J-L, El. 786'-6" 18 Reactor Building. Vent Retum Air Riser, EL. 805'4"-815' 36.83 257.26 1.0 19 Reactor Building. Vent Retum Air Riser, EL. 786'-6"- 36.85 224.60 1.0 805'4" 20 Reactor Building. Vent Retum Air Riser, EL. 815'-850' 33.74 252.18 1.0 21 Lower Ventilation Equipment Area, Unit 1 & Unit 2, EL. 14.80 107.49 0.34 786'-6", excluding the area of nodes 16,17 23 72" duct between proposed 72" excess flow damper 16.06 201.35 0.23 1(2)VR91Y and flow monitor
- Retum Spring force is not modeled for the isolation damper 1(2)VR05YA, the isolation damper stays open. The return spring is expected to pull the isolation damper closed in less than 1 second, then the maximum pressures would be approximately 30 psi.
ATTACHMENT G (Page 12 of 13)
SUMMARY
OF TRANSIENT PRESSURIZATION CALCUIATION OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS Diagrams showing the computed mass flow rate past damper 1(2)VR91Y and the converged area versus time for the COMPARE and Newtonian mechanics calculation are provided below.
350 g 300 - -- . _ _-.-- __ - . . . - - _ . _ - . - -- - .-_
5 i g 250 - :-.-.--.---.--- _ _ . - - - - . - - .
]
.E 200 -
I a: a$ 150 _ _ - - . . - _ - - - - - - - - . _ _ - - - - -
3-o ,
E 100 -- -
E
- 50 -. --
- _ . - ~ _ _ _
0 l 0 0.05 0.1 0.15 0.2 0.25 0.3 Time into Transient (sec) l Mass Flow Rate Through Damper- Single Disc 14 13 I - - - - - - - - - - - - -- . --- -- - _ . - -
12 - . - - - - -
p 11 .-. __ _ -_ _ ._ _ -..
I 10 -- - . . - . . - - - - - . _ -- _. . -- - - - . .
[t 9
8 ----
- -. . - - - n --- -
g 7 -- - - _ . - . - - _- .-
f 6 -- . - - - - . - . - -
5 5 . - - . - - --- -- -
f 4 , - ..- -- - - - -
.5 3 + Juac"aa ^'" "*as "aaa ""h'ak' . - - - - - . - - . -
' ~
-.o.=Juncuan Aru Mput k COMPARE l
0 - -----
O.000 0.100 0.200 0.300 0.400 Time into Translent (sec)
Figure O-4: Area Profile For the Proposed Excess Flow Damper 1VR91Y
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ATTACHMENT G (Page 13 of 13)
SUMMARY
OF TRANSIENT PRESSURIZATION CALCULATION OF THE VR EXHAUST DUCTWORK & EQUIPMENT ROOMS The pressure relief damper (1(2)VR90Y) is constmeted of parallel blades that rotate about a fixed horizontal shafts. The schematic below illustrates typical blades. The design and .
l constmetion is such that once the threshold opening pressure is reached the counter weight will I swing above top dead center and rotate to a lower position holding the relief damper fully opened until manually reset. The flow area versus time is shown below the diagram.
I Counter Weight and Linkage Lumped Mass
- E#'^"
Vertical Axis %- ,.-
l N 9 w
OW
..j.~
P.i. -
- Damper Blades E Amy,n A '" '-
0 I~'I
- U ICII "
Pressure Relief Damper Blade Schematic ,
I 50 m
40 _
=e-Damper Flow Area for COM PARE enput ; _ _ _ _ _ , _
$ _o_caicui.e.4 ch.cn o.mp.c rio. Ar..
.~
~
E 30 _ . _ _'__-_--.-------
t E 20 l
E i E .
I 10 -
.- J- _ 1 !
O---------------------------- l 0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400 Time into Transient (sec)
Figure O-6 Area Profile for the Pressure Relief Damper 1VR90Y !
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ATTACHMENT H QUALITATIVE
SUMMARY
OF ENVIRONMENTAL IMPACTS FOLLOWING A POSTULATED HELB IN THE UPPER MAIN STEAM TUNNEL I
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l ATTACHMENT H (Page 1 of 3)
QUALITATIVE
SUMMARY
OF ENVIRONMENTAL IMPACTS FOLLOWING A )
POSTULATED HELB IN THE UPPER MAIN STEAM TUNNEL !
INTRODUCTION: i l
Refined analysis has shown a flowpath of steam following a postulated HELB through the VR Exhaust ventilation system. This transient pressurization analysis is summanzed in Attachment G. The transient pressurization analysis has shown that the release of steam will be a short duration event (< 1 second) as a result of adding a pressure relief damper and an excess flow check damper for each Unit. The resulting impacts of this analysis on the surrounding structural components are summarized in Attachment F. The transient pressurization causes a release of j steam into the general areas of the Auxilia2y Building. The release of steam into the auxiliary I l
building is through the relief damper 1(2)VR90Y. In addition, the steam is released through the main vent stack and the main steam riser blowout panel to the atmosphere. The intent here is to cover the impacts of the release to the environs caused by the postulated transient l pressurization. The temperature, humidity, equipment dose, and thyroid dose impacts will all be I discussed to show that the release does not challenge the existing design or licensing basis for effects on equipment qualification and on personnel dose or offsite dose. The evaluation of the l impact of the release into the auxiliary building was performed prior to the addition of the !
1(2)VR91Y excess flow check damper, which reduces the length of time that the steam is released. Thus the discussions below are bounding for the actual configuration.
DISCUSSION:
Temperature:
Dunng the postulated event, steam is released into the Auxiliary Building at elevation 786'-6" from the pressure relief damper 1(2)VR90Y. The resulting temperature of the area immediately surrounding the duct was calculated to be 109.84 F. This is a minimalincrease (less than 4 F) from the maximum temperature for this area. The temperature increase in the other affected j Auxiliary Building areas is smaller (see Attachment G). The increase above the maximum !
temperature is a short duration event. Once the release of the steam has been isolated by the l secondary containment isolation dampers,1(2)VR05YA(B), the temperature will begin to dissipate. The temperature is not expected to remain above 106 for more than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Humidity:
Dunng the postulated event, steam is released into the Auxiliary Building at elevation 786'-6" from the pressure relief damper 1(2)VR90Y. As a result, the area immediately surrounding the pressure relief damper has an increase in humidity to 100% This increase has a minimal effect on the surrounding components due to the short duration of the postulated event. The humidity also quickly dissipates into the volume of the 786'-6" elevation.
ATTACHMENT H (Page 2 of 3)
QUALITATIVE
SUMMARY
OF ENVIRONMENTAL IMPACTS FOLLOWING A POSTULATED HELB IN THE UPPER MAIN STEAM TUNNEL EQ Dose:
The radiation dose increase seen by the components in the Auxiliary Building at Elevation 786'6" is nunimal. This shon duration event has been shown not to challenge the existing equipment qualification radiological values. Another issue with a release of radioactivity into the 786'6" elevation is the dose to personnel retrieving WGRM samples. Any additional dose has been shown to remain well within the GDC 19 limit of 5 rem.
CR and AEER Dose:
The radiological consequences of steam from a main steam line break (MSLB) flowing into the lower ventilation equipment room (LVER) (Area 21 of Attachment G) have been evaluated. It has been determined that:
(a) The design basis LOCA remains the bounding accident for the control room and auxilia:y electric equipment room (AEER) doses; (b) The MSLB accident doses remain below the limits of 10CFR50, GDC19; and (c) The estimated incremental doses from steam flowing into the LVER due to the MSLB are negligible (<0.05 rem to the thyroid).
The estimated thyroid doses from the MSLB are 8.1 rem in the control room and 7.2 rem in the AEER [per calculation L-001166, Section 7.3]. The thymid dose increments (from the MSLB steam that is diverted to the LVER) are 0.036 rem in the control room and 0.050 rem in the AEER, so the total estimated MSLB thyroid doses are now; control room - 8.14 rem, and AEER - 7.25 rem. These doses are much less than the design basis LOCA thyroid doses, which are; control room - 19.92 rem, and AEER - 28.97 rem [Ref.1, Section 7.2]. Therefore the increase in MSLB thyroid doses from MSLB steam divened to the AEER are insignificant compared to the previously estimated MSLB dose and the design basis LOCA doses.
These conclusions are valid for conditions up to and including the bounding scenario, which assumes that:
(a) The control room recirculation charcoal filter is not used until 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after the start of the MSLB, (b) Radioiodine in the reactor water is at the technical specification limit (4 Ci/gm), and (c) There is no iodine plateout (or other removal mechanism) inside the LVER.
Offsite Dose:
The radioactivity released from the MSL.B is unchanged whether or not some of the steam flows into the LVER. Therefore, the offsite doses remain unchanged because no credit is taken for iodine filtration for the offsite doses, and noble gas transport is unaffected. The only change to i the control room and AEER doses is due to the fact that a small fraction of the radioiodine can enter these areas via an unfiltered inleakage pathway.
ATTACHMENT H (Page 3 of 3) i QUALITATIVE
SUMMARY
OF ENVIRONMENTAL IMPACTS FOLLOWING A POSTULATED HELB IN THE UPPER MAIN STEAM TUNNEL CONCLUSIONS: j The flowpath through the pressure relief damper 1(2)VR90Y has been shown to have little impact on equipment or personnel. The release of the steam / water / air has little impact on I design allowables and does not challenge standing licensing limits. The minor impacts shown by l the current calculations can even be funher reduced when the new HELB excess flow check l dampers are installed. The new damper 1(2)VR91Y closes to isolate the pressurization. The I resulting release has been shown to be less than what was considered during the original i environmentalinvestigations. The final as built condition of the VR exhaust system will be 1 consistent with the original design through the isolation of the HELB pressurization and ,
reduction of the impacts to the equipment, personnel, and environment.
]
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r ATTACHMENT I SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOW CHECK DAMPERS
ATTACHMENT I (Page 1 of 10)
SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOW CHECK DAMPERS PURPOSE /OBIECTIVE The purpose of the evaluations provided here is to determine whether pressure relief dampers EPN 1(2)VR90Y and excess flow check dampers EPN 1(2)VR91Y may be considered to be exempt from consideration of single active failure by virtue of their design and function following a postulated HELB in the Main Steam tunnel outside containment.
SAFETY FUNCTION OF THE DAMPERS VR system exhaust ductwork interfaces with the Main Steam Tunnel (MST). This ductwork also directly interfaces with the VR system exhaust equipment rooms (flow balancing exhaust damper, filters, heat recovery coils, and exhaust fans). In the event of a postulated Main Steam / l Feedwater HELB in the MST and subsequent steam release, the MST will pressurize and drive steam into interfacing HVAC ducts. The VR exhaust duct is equipped with (i) an excess flow check damper which will rapidly close on excess flow, and (ii) a pressure relief damper which will rapidly open on increased pressure within the duct. The closure time of the check damper determines the amount of steam released past the dampers and the subsequent response 1 (pressurization, increased temperatures and humidity, etc.) of the downstream duct and interfacing areas. The opening time of the relief damper determines, in part, the pressurization of the adjacent ductwork and downstream areas.
The safety function of the excess flow check damper (EPN 1(2)VR91Y) is to close rapidly and stop flow on increased (HELB) flow within the duct.
The safety function of the pressure relief damper (EPN 1(2)VR90Y),in the duct downstream of the excess flow check damper, is to open rapidly and relieve pressure on increased pressure within the transition area of the duct.
The effect of the excess flow check damper is to isolate mass and energy release in the MST from surrounding areas of the plant and to limit downstream pressurization of block walls in HVAC equipment rooms which irterface with the VR exhaust ductwork by isolating a normally opened flow path from the MST. Unisolated mass and energy release from the MST to general j plant areas through the VR exhaust ductwork could potentially cause the environmental envelope for accident pressure, temperature, and humidity to be exceeded. In addition, failure of VR equipment room block walls could potentially impact adjacent safety-related equipment.
The effect of the pressure relief damper is to limit downstream pressurization of block walls in i HVAC equipment rooms, which interface with the VR exhaust ductwork by allowing the j venting of some of the duct flow to adjacent areas. Failure of VR equipment room block walls l by transient HELB pressure could potentially impact adjacent safety-related eqmpment. l l
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ATTACHMENT I (Page 2 of 10)
SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOW CHECK DAMPERS PART A - Sinele Failure Analysis of Pressure Relief Dampers EPN 1(2WR90Y Followine a Postulated Main Steam or Feedwater High Enerev Line Break .
(HELB) i 1
A1) PURPOSE / OBJECTIVE The purpose of this evaluation is to determine whether pressure relief dampers EPN 1(2)VR90Y may be considered to be exempt from consideration of single active failure by virtue of their design and function following a postulated HELB in the Main Steam l tunnel outside containment.
The Safety Evaluation for DCP9800112 addressed this issue for Unit 1 ano UFSAR changes were included in the DCP to document the failure modes and effects analysis for the pressure relief damper. The discussion here provides additional support for the conclusions documented in that Safety Evaluation.
A2) RELIEF DAMPER DESIGN, FAILURE MODES, AND CONSIDERATIONS A2.1 Damper Design The pressure relief dampers are manufactured as safety-related components under a quality assurance program by Preferred Metal Technologies, Inc. The damper blades are alllinked into a single assembly which is free to rotate open against the force of grasity on the blades and (initially) on the counterweight. When the counterweight has rotated past top-dead-center along its arc of travel, the weight assists in opening of the damper.
There are no latches or other mechanisms used to hold the damper blades closed.
The pressure relief damper is housed in a rectangular steel frame (~90-inch wide x 115-inch high) which is mounted in the VR exhaust ductwork. The frame consists of 1/4-inch thick steel channels ~ 8-inch wide around the perimeter. This rectangular frame is divided by a steel mullion and cross piece into four quadrants of similar strength to the i perimeter frame. !
Each quadrant contains four counterweighted rectangular damper blades, making sixteen blades in all. Each blade, constructed of 1/8-inch aluminum sheet,is hinged at the top and measures ~38.5-inch wide by 13-inch high. Each blade is attached by compression fit and fixing screws to a 1-inch diameter stainless steel shaft, and is free to rotate (absent the counterweights). This shaft protrudes beyond the blade window,into the outer frame channel on one side and into the enclosed mullion in the center. The shafts for the two blades at any given height are joined together within the mullion by a fixed mechanical coupling, thus causing the two blades to rotate together. Beyond this, all blades are linked together along the outer edge of the frame by a linkage. Thus all blades on both sides move together as one. The linkages are equipped with rod end bearings (Morse Spherco #TF-8N) to minmuze torsional friction in resistance to rapid opening of the relief damper.
ATTACHMENT I (Page 3 of 10)
SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOWCHECK DAMPERS The bottom of each blade is provided with sealing gasket that is attached using silicone adhesive. This gasket seals the damper assembly against the portion of the blade below, which protmdes above the rotating shaft. Each rotating shaft is supported on each end by Graphalloy flange bearing. This type of bearing is especially suited for good senice life under aging and severe environmental conditions with no maintenance.
The outer edge of each blade support shaft is fitted with an outrigger shaft and counterweight. The counterweights are normally positioned just beyond top-dead- :
center to hold the damper blades closed and to minimize leakage. On small rotations of ;
the damper blades, and with minimal, or calibrated force, the counterweights rotate !
beyond top-dead-center. At this point, the gravity force on the counterweights works
{
together with the hydrodynamic drag forces to open the assembly, all blades moving at '
once. Once opened, the counterweights hold the damper blades in position (against a limit stop) even in the absence of hydrodynamic drag forces on the blades. Closing of the blades, once opened, requires manual resetting. )
A simplified schematic of the pressure relief damper is provided below.
1 Counter Weight and J
Linkage Lumped Mass Vertical Axis g, g Damper Axis
\
,/
q l j
w _
l l
Aw P.,. - Damper Rlades P4 .,, I A ""a gl
- Flow Direction I
1 Figure A1: Pressure Relief Damper Blade Schematic.
The schematic shown above illustrates three typical blades. The actual damper consists of sixteen damper blades in four sets of four each, stacked two sets high and two sets wide.
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ATTACHMENT I (Page 4 of 10)
SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOW CHECK DAMPERS l l l
Damper response time was specified in the damper procurement specification and tested under simulated HELB transient response. Response time for opening was shown to be conservative relative to analytically assumed times. The damper construction was shown under test to be sufficiently sturdy to respond to accident conditions without damage or malfunction.
The installed damper is testable by periodic rotation of the damper blade assembly.
Periodic testing assures that blade rotation is free and unencumbered by friction or binding.
A2.2 Potential Failure Modes Opening of the damper blades is by simple and direct acting physical principles.
Differential pressure across the blades (i.e., a pressure within the duct that exceeds the pressure in the area surrounding the duct) results in an opening force on the blades. This is initially resisted by the counterweight, and after initial rotation, by the weight of the ,
blades. Once the counterweight has rotated beyond top-dead-center, the gravity force of l the weights on the blade assembly is directed to open the assembly, and to hold the !
assembly in the opened position, even in the absence of differential pressure forces due i to duct pressurization.
These primary forces (differential pressure and gravity) which affect the opening of the damper are not subject to change due either to aging mechanisms or alterations or ;
maintenance to the damper. Differential pressure is a simple physical principle, the i opening force being simply pressure multiplied by the area. This force is simple, direct, and immediate. If there is no differential pressure in the duct, there is no need for the ,
relief damper to open. l The gravity force exerted by the damper blades, and by the counterweights (first resisting, and then assisting opening) is not subject to change. Gravity of course is fixed, and the counterweights are not adjustable, except by deliberate modification of the damper assembly. Such modifications would only be permitted under controlled plant procedures (e.g.,10CFR50.59 review) which assure operability of the component.
There are minor forces that also affect the opening of the damper. These include friction within the bearings and binding between the damper blades and the frame of the damper assembly. The range of magnitudes for these forces is small relative to the opening force due to duct pressurization. The pressure required for initial opening of the damper is
~0.2 psi, while the pressure during damper opening quickly rises to the typical peak duct pressure of ~ 1 psi. Thus applied to the damper blade area, this results in a force of j [~0.2 to ~ 1 psi x 16 blades x 13-inch high x 38.5-inch wide] or ~1600 to ~ 8000 lbr.
! Understanding that only a part of this force is useful in opening the blades, it still l
represents a large force relative to resistive forces due to bearing friction and binding.
The damper is testable and is carefully designed to minimize such forces through use of specially selected bearings and through use of a mgged Seismic Category I steel frame that is highly resistant to misalignment that could cause binding.
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ATTACHMENT I (Page 5 of 10)
SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOW CHECK DAMPERS I
Since the damper assembly is completely cross-linked, all blades move as one. Failure of j individual components will not prevent the damper assembly from moving with the very i large opening forces present during a design basis HELB.
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i In summary, the damper assembly operates under simple, direct acting physical i principles. The main forces controlling damper opening are not subject to deterioration with age or testing. Minor forces resisting opening are carefully controlled and mmimized through design which includes design for the life of the plant. The assembly is testable in place and periodic testing will ensure operability.
A2.3 Relevant Considerations l
ANSI /ANS-58.9-1981 [Ref.1] provides design considerations for single failure in the I design of nuclear power plants. The guidelines identify that the plant shall be designed )
for initiating events (e.g., design basis HELB) in conjunction with an assumed, or the !
most limiting single failure. This single failure is a term that refers to a random failure and its consequential effects assumed in addition to an initiating event and its consequential effects. In the short term such as following a HELB, an active failure is considered. The active failure is a malfunction of a component that relies on mechanical movement to complete its intended function upon demand. The pressure relief damper falls within this category.
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However, the ANS standard also permits exemptions. Per Paragraph 4.1:
"4.1 Wlxw dx acthe)axtias <fa wrpmt can le darxnstranidspite any cndiHe wditias, dxn tkt wrpmt oruy le wuidmriexenptfnm aahefailum Exarnples qf sid wrputfaxtiais nuy irdide opming gfmie safety udm ard wtain swing dxtk udm. %e sid exanptiat is takm, t]x lusisfor tlx exenptim skllledwormtalin dx sirglefailweanalysis."
The active function of the pressure relief damper is considered exempted per the analysis and discussion presented here. The function of the damper is very similar to the function of both a code safety valve and a swing check valve. The principles governing operation are simple and direct, as is the case for the two components cited as examples in the exemption section of the ANS standard. Under the careful design, construction, and periodic testing of the damper, continued reliable performance is assured.
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1 ATTACHMENT I (Page 6 of 10)
SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOW CHECK DAMPERS A3) CONCLUSION Based on the analysis and discussion presented above, the active function of the pressure l relief damper is considered exempted from consideration of single failure. The l principles governing operation of the damper are simple and direct and not subject to change or deterioration with time. Under the careful design, construction, and periodic testing of the damper, continued reliable performance is assured. j l
A4) REFERENCES A-1. ANSI /ANS-58.9-1981/R1987, " Single Failure Criteria for Light Water Reactor Safety-related Fluid Systems."
1 A-2. Preferred Metal Technologies Fabrication Drawings )
Drawing No. 9038-PROD 1, Rev. O, Sheet 1 of 2, " Fabrication Drawing for 76x114 Pressure Relief Damper for Comed, LaSalle Station, ANSI /ASME j N509-76, Class 1." l l
Drawing No. 9038-PROD-1, Rev. O, Sheet 2 of 2, " Fabrication Drawing for {
76x114 Pressure Relief Damper for Comed, LaSalle Station, ANSI /ASME N509-76, Class 1." .
I' A-3. NDIT No. LAS-ENDIT-0827, Upgrade 4, " Technical Requirements for Procurement of Relief Damper 1(2)VR90Y and Duct Sections," June 19,1998.
A-4. Attachment O, pg. 28 to documentation for Design Change No. 9800113, I outlining requirements for periodic testing of damper torque opening setpoint.
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l ATTACHMENT I (Page 7 of 10)
SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOWCHECK DAMPERS PART B Single Failure Analysis of Excess Flow Check Dampers EPN 1(2WR91Y Follgwing a Postulated Main Steam or Feedwater High Enerev Line Break (HELB)
B1) PURPOSE / OBJECTIVE The purpose of this evaluation is to determine whether excess flow check dampers EPN 3 1(2)VR91Y may be considered to be exempt from consideration'of single active failure I by virtue of their design and function following a postulated HELB in the Main Steam tunnel outside containment.
B2) CHECK DAMPER DESIGN, FAILURE MODES, AND CONSIDERATIONS B2.1 Damper Design )
The excess flow check dampers are manufactured as nuclear safety-related components under a quality assurance program by Preferred Metal Technologies, Inc. Each damper is designedin accordance with the requirements of Article DA-4000 of ASME AG-1.
The dampers themselves are circular,in-line devices,72-inch in diameter. Similar in construction to a split disk check valve, the materials of construction conform to the requirements of Article DA-3000 of ASME AG-1 and are compatible with normal and accident environmental conditions as seen by the damper. The damper assembly and subcomponents are designed for a forty-year life.
The damper blades face into the air stream and are held in the open position with an adjustable load sensitive release mechanism. The damper blades are designed to automatically close due to any airflow increase above a predet ermined amount. Blrde stops are permanently attached to the damper body.
The blades are mounted on a continuous vertically oriented shaft which extends beyond the damper body to bearings mounted external to the airflow path.
The damper housing is a cylinder, ~38-inch long by ~72-inch in diameter, with end flanges. The two blades housed within the frame are elliptical aluminum plates,5/16-inch thick, and hinged about a central vertical axis. Each blade is held open against the drag forces created by normal airflow by a latching mechanism. This mechanism consists of a set of spring loaded jaws, fixed on one end, and machined on the other to accept and hold a Camrol bearing (mounted to the blade) which acts as a locking pin.
On increased hydrodynamic drag forces on the blades, the spring force holding the locking jaws together is overcome and the blade is released from the locking mechanism.
At this point, the blade is free to rotate and will be forced closed by a combination of the forces due to hydrodynamic drag.
ATTACHMENT I (Page 8 of 10)
SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOW CHECK DAMPERS The latching mechanism release setpoint is independently adjusted for each blade by changing the spring force exerted on the jaws. This setting was established by calculations and confirmed by factory and field testing and verified after field installation by periodic surveillance testing.
B2.2 Potential Failure Modes
. Closing of the damper blades is by simple and direct acting physical principles. I Differential pressure across the blades (i.e., hydrodynamic drag forces) directly translates into unlatching forces on the latching mechanism. At a predetermined setting, the damper blade is released from the mechanism and is free to swing closed under the combined effects of the drag force.
l This primary force (differential pressure) which effects the closing of the damper is not subject to change due either to aging mechanisms or alterations or maintenance to the damper. Differential pressure is a simple physical principle, the closing force being l simply pressure multiplied by the area. Differential pressure depends only on flow past the damper. The area of the damper blades is fixed and not subject to change. This closing force is simple, direct, and immediate. If there is no high flow condition in the duct, there is no need for the excess flow check damper to close.
There are minor forces that also affect the closing of the damper. These include friction within the bearings and potential binding between the damper blades and the frame of the damper assembly. The range of magnitudes for these forces is small relative to the closing force due to high airflow past the damper. The bearings are selected for forty-year life and periodically tested for free swinging rotation. Binding is not a particular j concern since clearances between the damper blades and housing is not critical and clearances are large. Once assembled in the factory, blade clearances are fixed and not subject to change. The housing is mgged and designed for seismic loading.
Extreme corrosion of the latching mechanism may result in unlatching forces, which are higher than design. This condition however,is not considered to be a part of the licensing design basis for these dampers based on the following:
. The latching mechanism is not in a particularly corrosive environment. Normal ,
airflow past the mechanism is hot and dry, coming from the MST l I
. The materials of the mechanism are coated to minimize corrosion
. The mechanism is periodically tested to ensure operability
. A similar latching mechanism is used on EPN 1/2VT79A/B/C (six check dampers in all) and has been installed for more than fifteen years in an en ironment similar to that expected for 1(2)VR91Y. The mechanisms on these dampers show no unusual level of corrosion or deterioration
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ATTACHMENT I (Page 10 of 10)
SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOWCHECK DAMPERS -
I B4) REFERENCES B 1. ANSI /ANS-58.9-1981/R1987, " Single Failure Criteria for Light Water Reactor Safety-related Fluid Systems."
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B-2. Preferred Metal Technologies Fabrication Drawings Drawing No. 9084-SCHP-72, Rev. 3, Sheet 1 of 3, " Spring Closed, High Pressure.HELB/ Check Damper 72" Diameter," 12/15/98.
Drawing No. 9084-SCHP-72, Rev. 3, Sheet 2 of 3, " Spring Closed, High Pressure HELB/ Check Damper 72" Diameter," 12/15/98.
Drawing No. 9084-SCHP-72, Rev. 3, Sheet 3 of 3, " Spring Closed, High !
Pressure HELB/ Check Damper 72" Diameter," 12/15/98.
1 Drawing No. 9084-LM-1, Rev.1, Sheet 1 of 2, " Locking Mechanism - Spring Closed, High Pressure HELB/ Check Damper 72" Diameter," 12/29/98.
Drawing No. 9084-LM 1, Rev.1, Sheet 2 of 2, " Locking Mechanism - Spring Closed, High Pressure HELB/ Check D.unper 72" Diameter," 12/29/98.
B-3. NDIT No. LAS-ENDIT-1060, Upgrade 2, " Technical Requirements for j Procurement of HELB Check Dampers IVR91Y and 2VR91Y," Decembe- {
23,1998.
B-4. Attachment O, pg. 27 to documentation for Design Change No. 9800113, outlining requirements for periodic testing of damper torque setting.
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A'ITACHMENT I (Page 9 of 10)
SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOW CHECK DAMPERS In summary, the damper assembly operates under simple, direct acting physical principles. The main force that is controlling damper closing is not subject to deterioration with age or testing. Minor forces resisting closing are carefully controlled and minimized through design which includes design for the life of the plant. The assembly is testable in place and periodic testing will ensure operability.
, B2.3 Relevant Considerations ANSI /ANS-58.9-1981 [Ref.1] provides design considerations for single failure in the design of nuclear power plants. The guidelines identify that the plant shall be designed for initiating events (e.g., design basis HELB) in conjunction with an assumed, or the most limiting single failure. This single failure is a term, which refers to a random failure, and its consequential effects assumed in addition to an initiating event and its consequential effects. In the short term such as following a HELB, an active failure is considered. The active failure is a malfunction of a component that relies on mechanical movement to complete its intended function upon demand. The excess flow check damper falls within this category.
However, the ANS standard also pennits exemptions. Per Paragraph 4.1:
"4.1 Where dxacti ejextxn cfa wpaw can ledermstrawldespueany cmidle ardtun, tim that angnnt truyle ansr'demlexenptfran aaixfailme Exarnples cf wth angnntfunams may irdde opnkg ofcafe safety udus and certain swing duk udas. Wlxte mch exenpticn is takm, dx lusisfor tlx exenpticn shallle daarneedin dx singlefailmeanalysis."
The active function of the excess flow check damper is considered exempted per the analysis and discussion presented here. The principles governing operation are simple and direct. Under the careful design, construction, and periodic testing of the damper, continued reliable performance is assured.
B3) CONCLUSION Based on the analysis ar.d discussion presented above, the active function of the excess I flow check damper is considered exempted from consideration of single failure. The principles governing operation of the damper are simple and direct and not subject to change or deterioration with time. The required force for unlatching is variable as !
established by the manual setting of the spring force. This setting is however, to be j controlled by procedure and test, assuring reliable operation under accident conditions. ;
Under the careful design, construction, and periodic testing of the damper, continued l operabilityis assured. i l
ATTACHMENT I (Page 10 of 10)
SINGLE FAILURE ANALYSIS FOR PRESSURE RELIEF DAMPERS AND EXCESS FLOW CHECK DAMPERS B4) REFERENCES B 1. ANSI /ANS 58.91981/R1987, " Single Failure Criteria for Light Water Reactor Safety-related Fluid Systems."
B-2. Preferred Metal Technologies Fabrication Drawings Drawing No. 9084-SCHP-72, Rev. 3, Sheet 1 of 3, " Spring Cosed, High 4 Pressure HELB/ Check Damper 72* Diameter," 12/15/98.
Drawing No. 9084-SCHP-72, Rev. 3, Sheet 2 of 3, " Spring Closed, High Pressure HELB/ Check Damper 72" Diameter," 12/15/98. l l
Drawing No. 9084-SCHP-72, Rev. 3, Sheet 3 of 3, " Spring Cosed, High Pressure HELB/ Check Damper 72" Diameter," 12/15/98. I Drawing No. 9084-LM 1, Rev.1, Sheet 1 of 2, " Locking Mechanism - Spring Cosed, High Pressure HELB/ Check Damper 72" Diameter," 12/29/98.
Drawing No. 9084-LM-1, Rev.1, Sheet 2 of 2, " Locking Mechanism - Spring Cosed, High Pressure HELB/ Check Damper 72" Diameter," 12/29/98. I B-3. lWJIT No. LAS-ENDIT 1060, Upgrade 2, " Technical Requirements for Procurement of HELB Check Dampers IVR91Y and 2VR91Y," December 23,1998.
B-4. Attachment O, pg. 27 to documentation for Design Change No. 9800113, outlining requirements for periodic testing of damper torque setting.
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