ML20205T662
| ML20205T662 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 06/11/1986 |
| From: | Allen C COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 1768K, NUDOCS 8606160131 | |
| Download: ML20205T662 (5) | |
Text
Commonwealth Edison 4 -) 72 Wet Ad.:ms Street, Chictgo, Illinois N'
Address R ply to: Post Offics Box 767 Chicago. llhnois 60690-0767 June 11, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
LaSalle County Station Unit 2 Fine Motion Control Rod Drive Demonstration Test Supplemental Information - License NPF-18 NRC Docket No. 50-374
Reference:
C. M. Allen letter to H. R. Denton dated February 25, 1986, transmitting FMCRD Topical Report, GE-NEDO 31130.
Dear Mr. Denton:
Enclosed are copies of General Electric (GE) responses to questions and concerns expressed by Mr. D. Katze of your staff in a conference call held on May 30, 1986.
Mr. Katze was completing his review of reference (a).
The conference call addressed five concerns for which Mr. Katze requested a written response in addition the verbal response given. The concerns expressed were:
(1) failure of purge (cooling) line restricting orifice (2) failure of line upstream of the " excess flow check valve".
l (3) description of the FMCRD In-plant Tests (4) compliance with General Design Criteria 23 (5) compliance with General Design criteria 26 Each of these are addressed in the attachment to this letter.
One signed original and ten (10) copies of this transmittal and its l
attachment are provided for your use. please address any questions you may have concerning this matter to this office.
e truly yours, i
P l
C. M. Allen Nuclear Licensing Administrator 1m Attachment cc:
J. G. Keppler - Region III Resident Inspector - LSCS G. Wright - IDNS l
G 'J DeNeh$h-h!CS
~
D. Katze - NRR g
1768K IfI
NRC QUESTIONS AND GE RESPN;SES ON THE FMCRD IN-PLAITT TEST PROGRAM NRC Question No. 1 GE to address failure of purge (cooling) line restricting orifice, purge line pipe crack or break on undercooling of remaining 184 Control Rod Drives.
GE Response No. 1 The " purge" water for the Fine Motion CRD (FMCRD) utilizes the existing
" cooling" water piping for the locking piston CRD (LPCRD). No additional piping is introduced requiring consideration of a pipe crack or break. The only modification required for the FMCRD application is the creation of a restricting orifice by drilling a 0.065 inch diameter hole into the wedge of the existing cooling water isolation valve (V104). A small pressure drop across the orifice (aP=20 psi), low flow rate (0.3 gpm) through the orifice, and substantial thickness (about 0.5 inch) of the wedge assure that disintegration of the orifice or wedge is highly unlikely. However, failure of this orifice or its pipeline could result in under-cooling of the drives adjacent to the FMCRD.
Persistent under-cooling of an LPCRD will be annunciated by a high temperature alarm in the control rom if the drive temperature exceed 250 F.
Once the high temperature alarm has annunciated, the LPHCU at location 02-43 could be isolated from the remainder of the CRD hydraulic system by manually closing HCU manual isolation valves V101 and V102. Proper cooling would then be restored to the remaining CRD's.
Operating a drive at temperature in excess of 250*F will not compromise the capability of rod insertion or scram performance.
It is preferable to operate below 250*F so as to assure an extended operating life and minimize maintenance.
Reduction of cooling flow into the LPCRD may result in entry of some additional minute contaminants into the LPCRD seals. 'Ihe LPCRD is designed to accommodate normal crud ingestion with its internal filters. Increased contamination could result in additional CRD seal wear over the long-term, but the safety function of the LPCRD relative to scram would not be affected..
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NRC Question No. 2 GE to address failure by pipe break or crack upstream of " excess flow check" in suction to booster pump on remaining 184 CRD's and other equipment.
GE Response No. 2 Each CRD is hydraulically " operated" by independent hydraulic control units (HCU).
In the event of the postulated piping rupture upstream of the " excess flow check valve", significant charging water leakage could occur.
The excess charging water discharge would result in decreased charging water header pressure, which would annunciate an alarm in the control room.
It should be noted that a charging water check valve would maintain the scram pressure and readiness of all HCU's. Furthermore, these HCU's are provided with low pressure switches that would annunciate the "HCU Trouble" alarms in the control room if l
the accumulator pressure decreases below the set point. Also, the charging water riser pipe for the HCU utilized to charge the FMCRD HCU is equipped with two valves (V107, Vll3) which could be used to isolate the postulated leakage.
Since each HCU operates independently, rod insertion or scram performance of the remaining rods would not be compromised.
NRC Ouestion No. 3 GE to clarify the FMCRD tests to be performed during preoperation and operating conditions.
GE Response No. 3 i
The testing of the FMCRD In-plant Test Program at the LaSalle Unit 2 Station will be conducted in two phases. During phase one, after installation of the equipnent and FMCRD, the post-installation electrical system check and the FMCRD system preoperation test will be performed. During phase two, after the power reaches 25% during the startup, the FMCRD operational tests will be performed.
'Ihere is no specific FMCRD test required after the startup tests, and the FMCRD will perform the identical function required of the replaced LPCRD at core location 02-43 during the entire second fuel cycle.
1 i -
'Ihe specific check / tests activities during these two phases are sumarized as follows:
Phase 1 FMCRD Post-Installation Verification a.
Electrical System Check - after the FMCRD system installation is completed, an electrical system check will be performed to verify proper cable / conduit routing, point-to-point electrical connection, step motor insulation resistance and running, local panel voltage level and ripple voltage and local panel interface, etc.
l b.
FMCRD System Pre-operational Test - The FMCRD system test consists of FMCRD/ control rod separation system verification, FMCRD/driveline friction test and FMCRD performance confirmation.
In the FMCRD performance confirmation tests, the FMCRD will be exercised five (5) full-strokes of continuous insert / withdrawal cycles, six (6) " step select" insert / withdrawal cycles and five (5) scram cycles. The performance of the Fine Motion Hydraulic Control Unit high/ low pressure alarm will also be verified prior to the restartup of the LaSalle Unit 2.
Phase 2 FMCRD Operational Demonstration When the power has reached 25% or above, a similar FMCRD performance confirmation test, as conducted in phase Ib above, will be performed.
That is, the FMCRD will be exercised five (5) full-strokes of continuous insert / withdrawal cycles, six (6) " step select" insert / withdrawal cycles, and five (5) scram cycles.
NRC Question No. 4 GE to address General Design Criterion 23, Protection System Failure Modes, as noted in SRP 4-6.
GE Response No. 4 Replacement of the locking piston control rod drive (LPCRD) at the peripheral core location 02-43 with a Fine Motion Control Rod Drive does not affect, in any -
J way, the fail-safe feature of the reactor protection system in regard to the scram safety function of the FMCRD or any other drive in t.be system. Upon the loss of external electrical power, the scram pilot valve on the new FMCRD Hydraulic Control Unit (HCU) will automatically actuate and open scram valve V126A and a scram will result. Similarly, the scram pilot valves of each of the other LPCRD HCU's will automatically open the scram inlet valve (V126) and the scram outlet valve (V127) leading to scram of the LPCRD's.
In the event of loss of scram air header pressure, the FMCRD-HCU scram valve (V126A) and the LPCRD-HCU inlet and outlet scram valves (V126 and V127) will open automatically resulting in a plant scram. Each HCU is a separate and independent unit, designed to maintain the fail-safe feature of the reactor protection systs.
NRC Question No. 5 GE to address General Design Criterion 26, Reactivity Control System Redundancy and Capability, as noted in SRP 4.6.
GE Response No. 5 Two independent reactivity control systems utilizing different principles are not altered with the introduction of the FMCRD. 'Ihe normal method of reactivity control employs control rod assemblies. A standby liquid control system (SICS) containing neutron absorbing sodium pentaborate solution is another method of independent backup system. As explained in Section 6 of the Licensing Topical Report NEDO-31130, the introduction of the FMCRD at the peripheral core location 02-43 does not affect the CRD system's ability to control reactivity changes under normal operation and anticipated operational occurrences with the appropriate margin for malfunction (such as rod withdrawal error and stuck rod).
Under such conditions, no fuel design limits will be exceeded and the reactor can be maintained subcritical under cold conditions. The independent SLC system has the capability to shut the reactor down from full power and maintain it in a subcritical condition at any time during the core life. Failures in or those affecting the CRD system will have no effect on the SIC system and both systems are not vulnerable to cmmon mode failures. Introduction of the FMCRD does not affect, in any way, this redundancy and capabilities of the two reactivity j
control systems., =
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