ML20077G995
| ML20077G995 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 06/28/1991 |
| From: | Stols R COMMONWEALTH EDISON CO. |
| To: | Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19302E721 | List: |
| References | |
| NUDOCS 9107030312 | |
| Download: ML20077G995 (9) | |
Text
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N Ccmmsnw:alth Edison
"' / 1400 Opus Place Downers Grove, tilinois 60515 June 28,1991 Dr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 Attn: Document Control Desk
Subject:
Quad Cities Nuclear Power Station Unit 2 Application for Amendment to Facility Operating Licenses DPR-30, Appendix A, Technical Specifications NRC RocketBosm50:265__
Dear Dr. Murley:
Pursuant to 10 CFR 50.90, Commonwealth Edison Compani (CECO) pro 30ses to amend Appendix A, Technical Specifications of Facility Operating Licenses DP 3 30. The proposed amendment reflects a proposed modification to the High Pressure Coolant Injection (HPCI) turbine steam exhaust line. The proposed amendment adds the requirements for the new containment isolation valves which are part of the modification.
The proposed amendment request is provided as follows:
- 1. provides the Safety Evaluation and Environmental Assessment for the amendment request;
- 2. provides a summary of the changes;
- 3. 3rovides the proposed Technical Specification pages which reflect t1e requested changes; and,
- 4. descrines CECO's evaluation pursuant to 10 CFR 50.92(c).
The information contained in Enclosure 1 is considered to be oroorietarv information to General Electric, and is supported by an affidavit signed by General Electric, the owners of the information. Enclosure 2 contains the affidavit that sets forth the basis on which the information may be withheld from public disclosure by the NRC and addresses the r.onsiderations listed in paragraph (b)(4) of 10 CFR 2.790 of the NRC regulations. Accordingly, CECO requests that the information contained in be withheld from public disclosure in accordance with 10 CFR 2.790.
This modification is scheduled to be implemented during the eleventh Refueling Outage for Unit 2 which is scheduled to begin on December 28,1991.
(
CECO, therefore, respectfully requests NRC's approval of this proposed amendment prior to the start of the Refueling Outage. CECO will ensure that the Project Manager is appraised of any schedule changes to the stat of the Refueling Outage.
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/9,64 8 9107o30312 91062e Y'1 i
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Dr. Thomas E. Murley June 28,1991 This proposed amendment has been reviewed and approved by CECO's onsite and off site review in accordance with Company procedures.
To the best of my knowledge and belief, the statements contained are true and correct. In some respect, these statements are not based on my personal knowled e. but obtained :nformation furnished by other CECO employees, contract 0
employees and consultants. Such information has been re elewed in accordance with company practice, and I believe it to be reliable.
CECO is notifying the State of Illinois of this application for amendment by transmitting a copy of this letter and its attachment to the designated State Official.
Please direct any questions concerning this submittal to Rita Stols at (708) 515 7283.
Very truly yours, h0 f
Rita Stols Nuclear Licensing Administrator Attachments: 1 Safety Evaluation and Environmental Assessment 2 Summary of the Proposed Changes 3 Proposed Technical Specification Pages 4 Evaluation of Significant Hazards Consideration
Enclosures:
- 1) General Electric Setpoint Calculations, GE-NE-901-013-0491, Revision 1 dated 6/06/91
- 2) General Electric Company Affidavit
- 3) General Electric Company Service Information Letter SIL 30 Figures:
1 HPCI Turbine Exhaust Line 2 HPCI Sparger Conceptual Design 3 Isolation Logic for Vacuum Breaker Line cc: A. Bert Davis, Regional Administrator-Rill F. A. Maura, inspector-Rill L.N. Olshan, Project Manager-NRR T.E. Taylor, Senior Resident inspector-QC State of d County of Signed before me on th%
day _
of
/f./,1991 Notary P
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ATTACHMENT 1 SAFETY EVALUATION AND ENVIRONMENTAL ASSESSMENT OFTHE PROPOSED AMENDMENT Back fW0d O
On June 15,1990, Region lli issued Inspection Report 50 254 (265)/89024 which summarized the results of their inspection of the Quad Cities 10 CFR 50 Appendix J Test Program. A Notice of Violation which cited ineffective corrective actions to repetitive valve failures was issued. One of the valves which was cited as a concern was the High Pressure Coolant injection (HPCI) steam exhaust check valve (2301-45).
The HPCI steam exhaust valve has experienced repeated Local Leak Rate Test (LLRT) failures. It is believed that the 2301-45 valve condition deteriorates due to unstable steam condensation during HPCI turbine low steam flow conditions. Previous attempts to improve valve performance consisted of redesigning the 2301-45 valve and/or changing the seating materials. In response to the Notice of Violation, Commonwealth Edison comr11tted to accelerate the test interval for the 2301-45 valve to enst,e that its containniciit function remains effective. In addition, surveillance procedures were revised to minimize potential damage to the valve during low speed turbine operation.
in September,1990 Commonwealth Edison conceptualized a modification to enhance the current design of the HPCI exhaust system and to create a new containment boundary such that the 2301-45 valve can be removed from the 10 CFR 50 Appendix J Program. This proposed modification provides the following benefits:
1.
Adds the ability to isolate the vacuum breaker line through the use of motor-operated valves thereby avoiding the poteat%I for a containment atmosphere leakage path through the HPCl turbine exhaust; 2.
Improves the reliability of the vacuum breaker with a "one-out-of-two tw.' 3" check valve configuration; 3.
Provides imprnved access for maintenance, since the vacuum breaker are located external to the torus; and, 4.
Improves the steam condensation stability through the use of a sparger which is designed to provide for more stable condensation over a wide range of steam flows, thereby minimizing the cyclical" chugging" load on the 2301-45 valve.
/064:10
, (continued) l Existing Configuration The existing configuration and proposed modification to the HPCI steam exhaust line is providedln Figure 1. The HPCI turbine exhaust line runs from the exhaust of the i
HPCI turbine through the Residual Heat Removal (RHR) comer room, penetrates the I
torus and discharges below the torus water level. The line contains two large turbine I
exhaust check vafves (2301-45 and 2301-74) which are designed to prevent water from backing up into the turbine. Inside the torus, a vacuum breaker line, which is equi 3 ped with two small check valves, ties into the HPCI turbine exhaust line downstream o' the I
turbine exhaust check valves. During normal HPCI operation, this vacuum breaker relieves the vacuum which is created by steam condensing in the exhaust line downstream of the turbine exhaust check valves.
The vacuum breaker line i%iae the torus provides a path for communication between the inside mi uutside containment atmospheres. The turbine exhaust check valves are therefwe required to prevent post accident containment atmosphere from escaping.10 CFR 50 Appendix J, Section ll.H requires localleak rate testing (Type C) testing of ine containment isolation valves.
The PPCI 2301-4 and 2301-5 valves (HPCI steam supply) isolate on a Group IV isolate sanal. These signals are high HPCI steam flow, high HPCI room temperatucA or low reactor pressure. The basis for HPCIisolation during high steam flow m ngh rocm temperature is to assure system isolation in the event of a line break. High pressure steam is recuired for the operation of the HPCI system. The steam supply valves isolate when HPCI is no longer capable of performing its design function.
Eroposed Modification The proposed modification (Figure 1) eliminates the existing air leakage path between the inside and outside containment atmospheres and addresses the cause of the 2301-45 valve deterioration.
The existing vacuum breaker line which is located inside the torus will be removed. The HPCI exhaust line terminates below the minimum water level of the suppression pool; therefore, the 4ne will not communicate directly with the containment atmosphere. The suppressior poolinventory provides an effec;lve water seal for the exhaust line during the post accident period.
Removal of the existing cir leakage pathway betwcon the torus atmosphere and the HPCI exhaust line eliminates the vacuum breaker protecihn. A new vacuum breaker configuration and exhaust line saarger is proposed for the following reasons:
(1) to protect the HPCI turbine exhaust ine from unstable steam condensation (chugging) and water hammer damage; (2) to provide a vacuum relief function; and, (3) to create a new containment boundary which provides for more reliable containment isolation. The new 4-inch vacuum breaker line will be an isolatable air leakage pathway between the containment air space and the HPCI exhaust line, and is located externci to the torus (Reference Figure 1). The line will contain two, motor-operated gate valves; four,4-inch check valves in a one-out of-two twice arrangement; two, 4-inch blocking gate valves for testing; and local leak rate test (LLRT) tap lines with 3/4-inch globe sockolet valves. The outboard valves will be powered from the 250 VDC Division li power source. The inboard valve will be fed from the 480 VAC Divis'on ll power source. The valves will be procured to safety-related and environmental qualification standards.
/E ' 4:11
Attachmont 1 (continued)
Proposed Modification (continued)
The sparger will be installed on the end of the HPCI turbine exhaust line inside of the torus and is designed to promote more stable steam condensation. The first row of i
holes on the sparger will be located at or below the current HPCI exhaust line
)
submergence (Peforence Figure 2). The valves and piping will be qualified for all applicable loads, including seismic and Mark I containment considerations.
The logic for the vacuum breaker isolation valves has been developed in i
accordance with the recommendations contained in Gener.J Electric Service Information Letter 30 (Reference (a)) and is consistent with the desl n of later 0
operating plants (e.g., LaSalle RCIC system). The vacuum line isolation valves will be normally o wn to assure the operational readiness of HPCI. As such, the system will be isolatec during conditions indicative of a large break inside of the drywell concurrent with low reactor pressure conditions such that HPCI can no lon0er perform its design function. The logic for the closure of each valvo is one-out of two taken twice arrangement (Reference Figure 3). The isolation signalis featured with a slanal seal in such that the signal must be reset and manual action must be implemented to open the valves following isolation. The isolation signal to each valve is provided from a separate control division such that no single physical f ailure could prevent isolation.
The new vacu"m breaker isolation valves will be required to have no greater than a 50 second clorure time. The most severe radiological conditions result from fuel damage due to a loss of reactor level which is accompanied by a loss of reactor pressure. Since the HPCI vacuum breater Isolation valves would close under low reactor pressure conditions (concurrent with high drywell pressure), the vacuum breaker isolation valves would be closed prior to fuel damage. As such, the closure time was determined based on the ability of the valve to close and assures that any potential radiological release is below regulatory and Technical Specification limits.
Evaluation of the Proposed Technical Spocrfications Table 3.o 1 Technical Specification Table 4.21, ' Min < mum Test and Calibration Frequency for Core and Containment Cooling System inatrumentation, Rod Blocks, and Isolations"
.equires that the HPCI isolation instruments be periodically calibrated and tested.
Technical Spec 3ication Table 3.21, " Instrumentation that Initiates Primary Containment Isolation Functions" does not, however, contain any requirements for the HPCI low teactor pressure isolation setpoint. To correct the omission, the requirements for t1e HPCI low reactor pressure isolation is proposed.
The basis for the HPCI turbine steam line low pressure isolation is to assure that steam and radioactive gases will not escape from the HPCI turbine shaft seals into the reactor building after steam pressure has decreased to such a low value that the turbine cannot be operated.
The instruments are currently set such that the isolation does not occur prior to reactor pressure decreasing to 90 psig. Prior to the approval of Technical Specifications amendment 130 (DPR 29) and 124 (DPR 30), HPCI was required to be operable at a reactor pressure greater than 90 psig. As such, the isolation should not occur (under decreasing reactor pressure) prior to 90 psig.
/964:12 I
Attachmont 1 (continuod)
Table 3.2-1 (contintnxf)
The current SAFER /GESTR Analysis for Quad Citios Station credits HPCI operation during decreasing reactor pressuro up to 150 psig. As sud, Commonwealth Edison contracted General Electric to calculato a now isolation sotpoint based on the current SAFER /GESTR Analysis innts.
The calculation was performed utilizing methodolo0y contained in NEDC 31336, "Gonoral Electric Instrument Sotpoint Methodology" dated Octobor,1986. Tho upper boundin0 ilmit for the isolation sl nal was 150 ps 0 which is based on tho 0
SAFER /GESTR Analysis inputs. A lower bound of 95 psig was chosen based on GE exporlonce to assure equipment protection. The lower bound is conservativo in that the anticipated stall pressure for the HPCI turbino is well below a reactor pressure of 95 psig. The recommended value for the nominalisolation setpoint (Licensin0)is 100 psl. The calculation is provided in Enclosure 1.
0 Tablo 3.7-1 Table 3. proposed Technical Specification adds the vacuum breaker isolation valvos to Tho
< 1,
- Primary Containment Isolation". As discussed previously, theso valves will be part of the Group IV lsolation which affects the HPCI system. Tho vacuum breaker isolation valves will automatically closo during high drywoll pressure conditions concurrent with low reactor pressure. This isolation logic is consistent with Gonoral Electric recommendations contained in SIL 30 and also with later designs for the system. This isolation scheme assures that the system will be maintained in operational roadiness except under conditions where HPCI can no lonDor operato, concurrent with Indication of a broak insido of the drywell. As previously discussed, the HPCI steam supply valves isolato during conditions which are indicativo of a steam lino break or under pressure condit'ons when HPCl can no longer perform its design function.
The most severo radiological roloaso results from fuel damago due to a loss of reactor water level which is accompanied by a loss of reactor pressure. Since the HPCI vacuum breaker lines would be isolated at low roactor pressure, the vacuum breaker isolation valves would be closed 3rior to fuel damage. A valvo closura time of 50 seconds has been datormined to be o' sufficient lon0th to ensure that any potential radiological releaso is below regulatory and licenso limits.
The proposed design providos a more rollaulo comainment isolation function. A more offective means of containment isolation is provided throu0 the use of small, h
l motor-operated valvos in place of the turbino exhaust check valves. The vacuum l
breaker isolation valves can be closed through remoto or local operation in the unlikely i
event of a failure of the automatic isolation.
l Environmental Assessment The proposed amendment adds sotpoint requirements for the HPCl isolation to Technical Specification Table 3.21. The amendment request also adds now primary j
containment isolation valves to Table 3.71 to reflect the proposed modification to the i
HPCI steam exhaust system. The modified system will be featured with an automatic isolation feature to ensure that the HPCI steam exhaust vacuum breaker is isolated during a accident conditions.
/964:13
Att:chment 1 (continued)
Environmental Assessment (continued)
Commonwealth Edison has evaluated the proposed amendment in accordance with the requirements of 10 CFR 51.21 and has determined that the amendment meets the rec ulroments for categorial exclusion as specified by 10 CFR 51.22 (c)(9).
Commonwea th Edison has determined that the amendment involves no significant hazards consideration (evaluation is contained in Attachment 4), there are no significant change in the types or significant increase in the amounts of any effluent that may be released off site, and there is no significant increase in individual or cumulative occupational radiation exposure.
Tha proposed amendment does not change the types of effluents or increase the amount of effluents that may be released offsite. The proposed design for the new containment isolation valves rec u!res that the valves be testod in accordance with 10 CFR 50 Appendix J requiremenus. Th9 testing will ensure that the containment leakage remains within Technical Specificate. requirements and as such will ensure any resulting dose will remain within 10 Ch'R Part 100 limits. The isolation lo0 c ensures l
that the leakage path willisolate durir g conditions which are indicative of a break inside l
of the drywell and HPCI can no lor,pr provide its design functions.
The proposed amendment does not significantly increase the individual or cumulative occupational radiation exposure. As discussed in the Background section of Attachment 1, Commonwealth Edison is currently testing the HPCI steam exhaust check valve on an accelerated schedule due to poor performance. As a result, occupational radiation exposure associated with this valve is higher than normally expected for the maintenance of a containment Isolation valve. The installation of the modification and the maintenance of the valves following installation is not expected to result in any significant increase in occupational exposures. The Installation of the modification will therefore minimize exposures when compared to the existing configuration.
In conclusion, the proposed amendment will not result in any increase in environmental consequences beyono those already accepted by the NRC in the Final Environmental Statement.
References I
(a)
General Electric Service Information Letter No. 30 entitled "HPCl/RCIC Turbine Exhaust Line Vacuum Breakers" dated October 31,1973 (b)
General Electric Document, GE-NE 901013-0491, 'Ouad Cities HPCI Turbine Steam Supply Pressure Low Sotpoint Calculation", revision 1 dated June 6,1991
/964:14
ATTACllMENT 2
SUMMARY
OF THE PROPOSED CHANGES TO APPENDIX A, TECHNICAL SPECIFICATIONS QUAD CITIES UNIT 2, DPR-30 Page 3.2/4.2 6a 1.
Revise the first paragraph of the bases to read:
"A trl3 of this instrumentation results in closure of the RCIC or HPCI steam supp y isolation valves. The t ip logic for this function is similar to that for the main steam isolation valves, 2,
Add the following to the first paragraph:
"In addition, the steam supply valves for each system are closed on low steamline pressure to provido primary containment isolation when the reactor pressure, as sensed in the system steamlines,is below the required pressure for turbine operations."
3.
Add the following to create a new second paragraph:
Operation of the HPCI turbine will continue as long as reactor pressure is above 150 psig. When the reactor presture falls below 150 psig., the speed of the tubine-pump unit will decrease and would gradually be slowed due to stop friction and windage losses at low reactor pressures. The low reactor pressure isolation setpoint was developed in accoraance with NEDC 31330, General Electric Instrument Setpoint Methodology" dated October,1986.
The trip setpoint of greater than or equal to 100 psig wcs calculated such that the isolation will occur on decreasing reactor pressure to provide primary containment isolation when the reactor pressure, as sensed in the system steamlines,is below the required aressure for turbine operation. The external vacuum breaker line for tie HPCI turbine willisolate on simultaneous low steamline pressure and high drywell pressure signals. The instrumentation and controls ensure the pro 3er HPCI and primary containment response to a HPCI steamline areak (Isolation of the steamline supply valves only), a large break inside the containment (closure of the steam su 3 ply and vacuum relief Isolation valves) and a small or intermediate size brea < inside of containment (steam supply and vacuum breaker isolation valves remain open for HPCI operation)."
Eage_3.2L4,2-LandeB 1.
Repaginate to accomodate changes to page 3.2/4.2 6a
/964:15
. (continuud)
Pago 324.211 1.
Add the HPCI steam lino pressuro low isolation requirements to Table 3.2-1.
The minimum number of operable or trippod instrument channels as "4" and a trip lovel sotting of greater than or equal to 100 psig.
2.
Ropaginate Tablo 3.21.
Rago_3,71.4.7221 Add the vacuum breaker isolation valvos to Table 3.71 to include the following Information: Group 4 Isolation: Vacuum breaker isolation MO-2399-40, MO 2399-41; Number of Power Operated Valves Outboard: 1; Maximum Oporating Timo: < 50; Normal Operat ng Position: 0; Action on Initiating Signal: GC.
2000 3.714 1 22 1.
Chango the description of Group 4, as follows:
"The steam supply isolation valvos in the high...."
2.
Add the following to the description of the Group 4 isolation:
The turbino exhaust vacuum breaker isolation valves closo when both of the followinD Sl nals are present (simultaneously):
0 1.
High drywell pressure 2.
Low roactor pressuro" 3.
Revise Group 5 isolation description as follows:
" Isolation valvos in the roactor coro isolation cooling system (RCIC) are closed upon any one of the following signals:
1.
RCIC steam line high flow 2.
High Temperature in the vicinity of the RCIC steamline 3.
Low reactor pressure" l
l
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