ML20029D421
| ML20029D421 | |
| Person / Time | |
|---|---|
| Site: | 05200001 |
| Issue date: | 04/29/1994 |
| From: | Fox J GENERAL ELECTRIC CO. |
| To: | Poslusny C Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9405050360 | |
| Download: ML20029D421 (12) | |
Text
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> GE Nuclear Energy
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s {\.1% kvw % e CA 9I April 29,1994 Docket No.52-001 Chet Poslusny, Senior Project Manager Standardization Project Directorate Associate Directorate for Advanced Reactors and License Renewal Office of the Nuclear Reactor Regulation
Subject:
Submittal Supporting Accelerated ABWR Schedule -
Detailed Design of FMCRD
Dear Chet:
Enclosed are revised SSAR markups responding to the GE commitments made at the April 15,1994 GE/NRC meeting in Rockville, Maryland. Included are (1) additional information reflecting the locking mechanisms of the subassemblies and European ex 3erience, and (2) fmalized Technical Specifications for multiple control rod drive subassembly removal - refueling.
The color version of a drawing of the complete FMCRD was transmitted to Dave Diec last week.
Sincerely,
(. Ye/o ck Fox Advanced Reactor Programs cc: Alan Beard GE)
Alan Ehrke GE)
Norman Fletcher DOE)
Dick Ose Joe Quirk Cal Tang 0
030102 f'0 mwes I
(
9405050360 940429 (
, 23A6w0 Rev. 4 ABWR st:ndredstrity An:tysis asp:rt piece flange and the middle flange of the drive to the housing flange, the anti-rotation device will be engaged when the spool piece falls and the middle flange / outer tube /CRD blowout support will be restrained by the control rod guide tube base bayonet coupling, thus preventing rod ejection.
4.6.2.3.3.2 Control Rod Drop Prevention Control rod drop is prevented by the following features:
(1) Two redundant Class IE switches in the BfCRD sense separation of the .
hollow piston, which positions the control rod, from the ball-nut. These l switches sense either separation of the piston from the nut or separation of the l control rod from the piston, and block further lowering of the nut, thereby preventing drop of either the control rod or the control rod and hollow piston as an assembly (See Subsection 4.6.1.2.2.6 for further details).
(2) Two redundant spring-loaded latches on the hollow piston open to engage in openings in the guide tube within the BfCRD to catch the hollow piston if separation from the ball-nut were to occur. These latches open to support the hollow piston (and control rod) following every scram until the ball-nut is run- -
in to provide the normal support for the hollow piston (and control rod). 1 (3) The control-rod to hollow-piston coupling is a bayonet type coupling.
Coupling is verified by pull test for the control rod upon initial coupling at refueling and again each time an attempt is made to drive beyond the " full out" position during reactor operation. The control rod can only be uncoupled from the Bf CRD by relative rotation, which is not possible during operation. The control rod cannot rotate, since it is always constrained between four fuel assemblies, and the hollow piston /CRD bayonet coupling cannot rotate, since the hollow piston has rollers which operate in a track within the BfCRD. Only structural failure would permit or result in control rod to FMCRD uncoupling, which,in turn, could only resultin rod drop if the redundant switches failed to sense separation. In such failure scenarios, the rate of rod drop may exceed acceptable reactivity addition rates; however, the number of failures involved in the scenario are so numerous that the probability of occurrence for the event is low enough to be categorized as incredible.
4.6.2.3.4 CRD Maintenance The procedure for removal of the Bf CRD for maintenance or replacement is similar to previous BWR product lines. The control rod is first withdrawn until it backseats onto the control rod guide tube. This metal-to-metal contact provides the seal that prevents draining of reactor water when the BfCRD is subsequently lowered out of the CRD housing. The control rod normally remains in this backseated condition at all times with 4.6-22 Functional Design of Reactivity Control System - Amendment 34 l
. 23A3100 Rev. 4 ABWR standard saretyAnalysis Report the BICRD out; however, in the unlikely event it also has to be removed. a temporary blind flange is first installed on the end of the CRD housing to prevent draining of reactor water.
If the operator inadvertently removes the control rod after BICRD is out without first installing the temporary blind flange, or conversely, inadvertently removes the BICRD after first removirig the control rod, an unisolable opening in the bottom of the reactor wili be created, resulting in drainage of reactor water. The possibility ofinadvertent reactor draindown by this means is considered remote for the following reasons:
(1) Procedural controls similar to those of current BWRs will provide the pdmary means for prevention. Current BWR operating experience demonstrates this to be an acceptable approach. There has been no instance of an inadvertent draindown of reactor water due to simultaneous CRD and control rod removal.
(2) During drive removal operations, personnel will be required to monitor under the RPV for water leakage out of the CRD housing. Abnormal or excessive leakage occurring after only a partial lowering of the RfCRD within its housing willindicate the absence of the full metal--to-metal seal between the control rod and control rod guide tube required for full drive removal. In this event, the BICRD can then be raised back into its installed position to stop the leakage and allow corrective action.
See Subsection 4.6.6.1 for COL applicant license information.
4 IMSERT WW TEXT HERE' 4.6.3 Testing and Verification of the CRDs 4.6.3.1 Development Tests The initial development of the BICRD involved testing of a prototype based on a European drive design. Testing of this prototype included more than 600 scrams and 67,000 motor-driven cycles. A subsequent prototype was developed for installation in an operating BWR for the purpose of demonstrating niCRD performance under actual BWR operating conditions. This in-plant BICRD prototype was tested extensively prior to installation at the operating plant, including over 500 scrams and 63,000 step cycles.
The inplant BiCRD was installed at LaSalle Unit 2, where it was tested for one complete operating cycle.
A reference RfCRD prototype design, based on refinements ofinitial development prototypes described above, has been developed and tested. To date, testing of this reference prototype has included over 1,000 scrams and 150,000 step cycles. These tests have demonstrated the following: 1 (1) The drive easily withstands the forces, pressures and temperatures imposed.
Functional Design of Reactivity Control System - Amendment 34 4.6-23
New Text for SSAR Paragranh 4.6.2.3.4 l
The FMCRD design also allows for separate removal of the stepping motor, position indicator probe (PIP) and spool piece for maintenance during plant outages without disturbing the upper assembly of the drive. While these l FMCRD components are removed for servicing, the associated control rod is maintained in the fully inserted position by one of two mechanical locking devices that prevent rotation of the ball spindle and drive shaft.
The first anti-rotation device (Detail A in Figure 4.6-8) is engaged when the motor assembly consisting of the stepping motor, brake and synchro is removed. It is a horizontally acting spring-actuated sliding pin located on the bottom of the spool piece. When the motor assembly is lowered away from the spool piece, the sliding pin is released from its normally retracted position and engaged by spring force with gear teeth on the spool piece drive shaft, thereby locking the shaft in place. This design is similar to that of an anti-rotation device that has been used successfully for many years in the same application by a European FMCRD design.
With the motor assembly removed, the sliding pin can be visually checked from below the drive to verify that it is properly engaged. When the vessel head is removed, another means of verification of proper locking is for the operator to view the top of the control rod from over the reactor vessel. If the top of the control rod is visible at its normal full-in position, it provides both direct indication that the control rod remains fully inserted and additional assurance that the ball spindle is restrained from reverse rotation. The drive shaft remains locked in this manner until the motor assembly is reattached to the spool piece. During motor installation, a pin-and-roller device on the top of the motor engages with a lever attached to the sliding pin as the motor is raised into contact with the spool piece. The pin-and-roller forces the lever and sliding pin away from the drive shaft and into the normally retracted, unlocked position.
The second anti-rotation device (Detail B in Figure 4.6-8) is engaged when the spool piece is removed from the FMCRD. As described in Section 4.6.2.3.3.1.3, this device is a spline arrangement between the ball spindle lower portion and the middle flange backseat. When removing and lowering the spool piece, the weight of the ball spindle, hollow piston and control rod provides a vertical force in the downward direction that brings the two splines together. This locks the ball spindle into the backseat and prevents reverse rotation. As with the first anti-rotation device, proper engagement of this device can be visnally checked from below the drive. If the splines did not completely lock together, there will be indication of this because the hall spindle will not seat against the backseat and there will be a small gap for leakage of water. If this should occur, removal of the spool piece can be discontinued and corrective action taken. If there is no leakage, it confirms that the splines are properly locked together. Also as in the case of the first anti-rotation device, visual observation of the top of the control rod from over the reactor vessel provides another
mears for verifying proper locking of the ball spindle. The ball spindle remains locked in this position until the spool piece is reattached to the FMCRD. During spool piece installation, the end of the drive shaft fits into a seat on the end of the ball spindle. As the spool piece is raised into contact i with the drive middle flange, the ball spindle is raised off the middle flange backseat, the anti-rotation splines disengage and the weight of the ball spindle, hollow piston and control rod is transferred to the spool piece assembly.
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Functional Design of Reactivity Control System - Amendment 34 4.6-29
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Multiple Control Rod Drive Subassembly Removal- Refueling 3.10.12 3.10 SPECIAL OPERATIONS 3.10.12 Multiple Control Rod Drive Subassembly Removal-Refueling i
LC0 .3.10.12 The requirements of LC0 3.9.3, " Control Rod Position";
l LC0 3.9.4, " Control Rod Position Indication"; and LC0 3.9.5,
- " Control Rod OPERABILITY-Refueling," may be suspended, and the " full in" position indicators may be bypassed for any number of control rods in MODE 5, to allow removal of control rod drive subassemblies with the control rods maintained fully inserted by their anti-rotation devices, provided the following requirements are met
- a. No two adjacent (fa?sMyiihdisl) control rod drives are to have their subassemblies removed concurrently unless one of the two adjacent control rods has its four fuel assemblies removed from its associated core cell, and
- b. All other control rods in core cells containing one or more fuel assemblies are fully inserted.
l APPLICABILITY: MODE 5 with LCO 3.9.3, LC0 3.9.4, or LC0 3.9.5 not met. i ACTIONS l CONDITION REQUIRED ACTION COMPLETION TIME A. One or more of the A.1 Suspend removal of Immediately above requirements not associated CRD l met. subassemblies.
AND (continued) i ABWR TS 3.10-28 Amendnent i
l
Multiple Control Rod Drive Subassembly Removal- Refueling 3.10.12 ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME l
A. (continued) A.2.1 Initiate action to Immediately fully insert all control rods in core cells containing one or more fuel assemblies.
OR l
A.2.2 Initiate action to Immediately l satisfy the
, requirements of this l LCO.
SURVEILLANCE REQUIREMENTS
! SURVEILLANCE FREQUENCY SR 3.10.12.1 Verify the anti-rotation devices associated 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> with each CRD subassembly removed are in i the correct position to mainta'n the
! control rod fully inserted.
i SR 3.10.12.2 For each control rod with its associated 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> CRD subassembly removed, verify from over the reactor vessel that the top of the control rod is visible at its fully inserted position.
SR 3.10.12.3 Verify all other control rods in core cells 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> containing one or more fuel assemblies are fully inserted.
i l
I i
ABWR TS 3.10-29 ownsent
l '. .
Multiple Control Rod Drive Subassembly Removal-Refueling i- B 3.10.12 B.3.10' SPECIAL OPERAT10NS B 3.10.12 Multiple Control Rod Drive Subassembly Removal-Refueling BASES 6fd N ROUND The purpose of this MODE 5 Special Operations LC0 is to permit multiple control rod drive subassembly removal during refueling by imposing certain administrative c .,' ls. For the purposes of this LCO, CRD subassembly rem < t' is the removal of the CRD motor assembly, which incli es the motor, brake and synchro, the position indicator prol PIP) and the spool piece assembly, with the associated cont) .1 rod maintained in the fully inserted position by mechanical anti-rotational locking devices. With the CRD: subassembly ,
removed, control rod position indication is not available in the control room. Reference 2 contains a description of the CRD subassembly removal.
Refueling interlocks restrict the movement of control rods and the operation of the refueling equipment to reinforce operational procedures that prevent the reactor from becoming critical during refueling operations. During ,
refueling operations, no more than one control rod, or ;
control rod pair, is permitted to be withdrawn from a core cell containing one or more fuel assemblies.
5 The refueling interlocks use the " full in" position indicators to determine the position of all control rods.
If the " full in" position signal is not present for every control rod, then the all rods in permissive for the refueling equipment interlocks is not present and fuel loading is prevented. Also, the refuel position rod-out interlock will not allow the withdrawal of additional control rod (s).
This Special Operations LC0 establishes the necessary administrative coritrols to allow bypass of the " full in" position indicators for CRDs with subassemblies removed for maintenance and the associated rods maintained fully '
inserted by their mechanical anti-rotation locking devices.
LC0 3.10.6 establishes administrative controls for complete removal of multiple CRDs where the control rods are fully withdrawn.
I i
(continued)
ABWR TS B 3.10-49 Amendment
- f. .
1
! Multiple Control Rod Drive Subassembly Removal-Refueling y B 3.10.12 l
~
BASES
, APPLICABLE Explicit safety analyses in the SSAR (Ref. 1) demonstrate
! SAFETY ANALYSES that the functioning of the refueling interlocks and
! adequate SDM will prevent unacceptable reactivity excursions during refueling. To allow multiple control rod drive '
subassembly removal, the " full in" position indication is l allowed to be bypassed for each control rod drive with its subassembly removed and the associated control rod maintained fully inserted by its mechanical anti-rotation locking devices.
. As described in LC0 3.0.7, compliance with Special Operations LCOs is optional, and therefore, no criteria of the NRC Policy Statement apply. Special Operations LCOs provide flexibility to perform certain operations by appropriately modifying requirements of other LCOs. A discussion of the criteria satisfied for the other LCOs is provided in their respective Bases.
l LC0 As described in LC0 3.0.7, compliance with this Special j Operations LC0 is optional. Operation in MODE 5 with l LCO 3.9.3, " Control Rod Position," LC0 3.9.4, " Control Rod Position Indication," or LCO 3.9.5, " Control Rod OPERABILITY-Refueling," not met, can be performed in accordance with the Required Actions of these LCOs without meeting this Special Operations LCO or its ACTIONS. If multiple control rod drive subassembly removal is desired, only non-adjacent (faceWdiagonal) CRD subassembly removal is allowed to minimize ths possibility of an inadvertent
~
criticality. Prior to entering this LCO, any fuel remaining in a Cell ~ I.v.,C COT.tr0l r0d '.;T.", i,7CV'iOusly a cnuoved utider' ihe provisions of another LC0 must be removed.
l i
APPLICABILITY Operation in MODE 5 is controlled by existing LCOs. The exceptions from other LC0 requirements (e.g., the ACTIONS of LC0 3.9.3, LC0 3.9.4 or LC0 3.9.5) allowed by this Special Operations LC0 are appropriately controlled by allowing only the removal of non-adjacent control rod drive subassemblies whose " full in" indicators are allowed to be bypassed and associated control rods maintained fully inserted by their anti-rotation devices.
(continued)
ABWR TS B 3.10-50 Amendment i
i
1 1
- e .
Multiple Control Rod Drive Subassembly Removal-Refueling j o B 3.10.12 l B,ASES'(continued)
ACTIONS A.I. A.2.1. and A.2.2 If one or more of the requirements of this Special Operations LC0 are not met, the immediate implementation of these Required Actions restores operation consistent with the normal requirements for refuelin (i.e., all control rods insrted in core cells contair a one or more fuel assemblie:,) or with the exceptions panted by this Special Operations LC0. The Completion Times for Required Action A.1, Required Action A.2.1, and Required Action A.2.2 are intended to require that these Required Actions be implemented in a very short time and carried through in an expeditious manner to either initiate action to restore the affected CRDs and insert their control rods, or initiate action to restore compliance with this Special Operations LC0.
SURVEILLANCE SR 3.10.12.1. SR 3.10.12.2 and SR 3.10.12.3 REQUIREMENTS Periodic verification of the administrative controls established by this Special Operations LC0 is prudent to preclude the possibility of an inadvertent criticality. The ,
24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Frequency is acceptable, given the administrative controls on control rod drive subassembly removal, and takes into account the reliability of the mechanical anti-rotation I locking devices to maintain the control rods in their fully inserted position.
REFERENCES 1. ABWR SSAR, Section 15.4.1.
ABWR TS B 3.10-51 Amendment I
l l