ML20238F568
| ML20238F568 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 09/14/1987 |
| From: | Tiernan J BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| GL-87-12, NUDOCS 8709160226 | |
| Download: ML20238F568 (15) | |
Text
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i B ALTIMORE '
GAS AND ELECTRIC
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CHAR' ES CENTEH P. O.BC)'1475 - BALTIMORE. MARYLAND I R03 >
.osrP4 A T lLRNAN Veit Pntsir f v7 N uc.6t AR E w' Ar. i September 14, 1987
. U. S. Nuclear Regutttory Com nission ~
Was'dngton, DC 20M5
- ffTENTION: Documer t Contro1DesL-SU1MECT: Calvert Cliffs Nuclear ! N et Plant Unit Nos.1 & 2: Docket Nas. 50-347 4 50-318 Responu to G'./ e' .h Letter 87-l?., "Lc;s of Residual lleat denwal While the Retar_{f olant Sv? tem is Partially Fi[4f .
i REFERENCE (a) Generic Le?.tec 87- f 2, Loss of Pesidual, . Ileat Removal While the React;r Co): ant Syd m is Parti 41iy Filfed," dated Jc'.y 9, 1987
('c} Telephone c., nversation between Mr. S. A. McNeil (N"1C), and Mr. L. S. Lar:.noite (BG&E), August 31, 1987, conurpin; response to Generic Letter 87-12 Gentlemen:
la Generic Letter 8i-12 (Reference a), you requested that we describe . our plant cr,cr atiori during the approach to, and with, a partially filled Reactor Coolant System (RCS). Ou msponse is prevMed as Enclosure (1).
As disc us.t.ed 6th sour staff (lieference b), we ' ire wor king th ro y,h the Combustion Eng n xring (CL) Owners Groep to review the potential unanalyzed ccndition prescrited in the Jencric .,e t te r. Specific.G y, the concern is a lus of.. residual ne at removal, leading to RCS pr<.ssuritation and toten'lal e.;ection of coolant via a colo leg opening (e.g., maintenance on a RCP seal w,embb). W- expect to provide our response to thir concern by October 15, 1987.
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- Septernber 14. 1987 Page 2 c
She ttd you hauts any questicns regarding this matter, we will be pleased to discuss them vei;h you.
Very truly yours, W
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1 STATE 01" MARYLAND :
- TO WIT:
CUUNTYOFCALVERT :
Joseph A. Tiernan, being duly sworn states that he is Vice President of the Baltimore Gr.s and EJectric Company, a corporation of the State of Maryland; that he provides the foregoing response for the purposes therein set forth; that the statements made are triis and correct to the best of his knowledge, information, and belief; and that he was s
' autharina" to provide the response on behalf of said Corporation, l
WITIfESS my Hand and Notarial Seal: d++ - $J-( (4., -. .
Notary Public My Commission Expires: 7 90 9[sN 7
/ Date l
JhT/LSL/ dim Attachments cc: D, A. Brune, Esquire J. E. Silberg, Esquire R. A.Capra, NRC S. A. McNeil, NRC W. T. Russell, NRC T. Foley/D. C. Trimble, NRC
ENCLOSURE m
- CALVERTCLIFFS RESPONSE TO GENERIC LETTER 87-12 i
The following responds to your request for information regarding our plant operation with a partially filled Reactor Coolant System (RCS). You also asked that we provide information regarding our approach to a partially filled RCS. Your specific questions and our response to each are provided below. Unless otherwise specified, the responses are applicable to both Units 1 and 2,
- 1. A detailed description of the circumstances and conditions under which your plant would be entered into and brought through a draindown process and operated with the RCS partially filled, including any interlocks that could cause a disturbance to the system. Examples of the type of information required are:
o The time between full-power operation and reaching a partially filled condition (used to determine decay heat loads);
o The requirements for minimum steam generator (SG) levels, changes in the status of equipment for maintenance and testing, and coordination of such operations while the RCS is partially filled; o The ' restrictions regarding testing, operations, and maintenance that could perturb the nuclear steam supply system (NSSS);
o The ability of the RCS to withstand pressurization if the reactor vessel head and SG manway are in place; o The requirements pertaining to isolation of containment; o The time required to replace the equipment hatch should replacement be necessary; and o The requirements pertinent to reestablishing the integrity of the RCS pressure boundary.
R ESPONSJi The most likely reasons for draining the RCS below the top of the hot leg are either maintenance on a reactor coolant pump (RCP) seal assembly, or inspection /
maintenance on the primary side of the SG. The latter requires the installation of SG nozzle dams. While maintenance on a RCP seal assembly does not require draining the RCS lower than the mid-plane of the hot leg, installation cf SG nozzle dams does. However, once the SG nozzle dams are installed, RCS level can then be restored to above the mid-plane.
The time to reach a partially filled condition from full power is a function of the methcd of shutdown (normal controlled shutdown versus reactor trip), and the hydrogen concentration of the RCS (which dictates the time required for de-gassification before maintenance operations). A realistic average time from 100% power to a partially filled condition is approximately 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. This is based on a review of actual times frcm previous maintenance outages.
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. ENCLOSURE (1) e CALVERT CLIFFS RESPONSE TO GENERIC LETTER 87-12 When a SG is used as part of an OPERABLE RCS loop in COLD SHUTDOWN (MODE 5),
Technical Spc4% ion 3.4.1.3 requires ' a minimum level of ~-50 ' inches. During partially fi!M conditions, there are no minimum SG level requirements since the RCS. loop is not OPERABLE. However. in practice, . SG levels 'are maintained as follows~ for proper SG chemistry: for short-term shutdowns, SGs tu filled to the
- top of the indicating range;, for long-term shutdown, SGs are fh.d J above . the moisture separatm. If maintenance is being performed on ' the secondary side, of the SGs,; normally only one SG at a time is drained During core alterations . or movement of irradiated fuel within ' the containment, -
, Technical Specification 3.9.4 requires the containment equipment door be closed-and held in place by: a minimum of four bolts, a minimum of one closed door in each containment airlock, each containment penetration providing direct access :
from 'the . containment atmosphere to the outside atmosphere closed, and the containment purge valves cither. OPERABLE or closed. These requirements are verified by use of Surveillance Test Procedure (STP) 55- A. If- Shutdown Cooling (SDC) 'is lost, Techt aal Specification 3.9.8.1 (applicable' to MODE 6) requires . closing - all containment penetr3tions providing direct access from containment atmosphere to the ' outside atmosphere. Finally, ' Abnormal Operating Procedure (AOP)-3B, Loss of_ Shutdown Cooling, requires ' STP-0-55-A to be -
implemented ' anytime SDC is lost and cannot be restored. If necessary, it would take approximately one hour to replace the equipment hatch.
Since the condition of the RCS pressure. boundary cannot be anticipated, there are no specific procedure requirements for re-establishing the RCS pressure boundary in the event of a loss of SDC. However, AOP-3B is written to address the three conditions 'which ' pertain . to the general status of the RCS (see response to -
Question 5).
Our Outage Planning Organization functions to ensure coordination of planned maintenance activities. Key personnel are experienced in system requirements for various plant conditions, ' including a partially filled RCS. Planned maintenance is reviewed by ' an experienced Senior Reactor Operator, and all testing and maintenance must be approved by ' the Shift Supervisor. A discussion 'is provided in Question 9 regarding our review of STPs to ensure they minimize the possit5ity of a loss of SDC.
- 2. A detailed description of the instrumentation and alarms provided to the !
operators for controlling thermal and hydraulic aspects of the NSSS during opera- i tion with the RCS partially filled. You should describe temporary connections, piping, and instrumentation used for this RCS condition and the quality control process to ensure proper functioning of such connections, piping, and instrumen- I tation, including assurance that they do not contribute to loss of RCS inver, tory J or otherwise lead to perturbation of the NSSS while the RCS is partially filled.
You should also provide a description of your ability to monitor RCS pressure, temperature, and level after the RHR function is lost.
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EN_ CLOSURE (Il CALVERT CLIFFS RESPONSE TO G ENERIC LE1TER 87-12 EESPONSE:
During ,' a partially; filled . condition, RCS level indication , is provided . by the Reactor : Vessel Level Monitoring System '(RVLMS),.. Refueling Level Indication, and 6tygon; tube . level indication. The- RVLMS- uses' heated / unheated ' junction; I
thermocouple. '. Associated indicator lights in the J Control ' Room provide . eight discrete level increments in the reactor vessel . (10, 19, 29, 50, 71, 112, 153, and 185 inches above the top of the fuel support plate). Indication would be unaffected if SDC ~were . lost. This system is only available when the reactor vessel head is . installed and'the instrumentation is t electrically co'nnected.
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Refueling Level . Indicatlon . is provided by a permanently' ins'talled pressure transmitter which senses off the bottom of one hot leg (opposite the hot leg SDC takes suction on) via the - drain piping. The, transmitter is referenced to I. atmospheric pressure. Indication is provided in the Control . Room by a digital meter and recorder which is calibrated ' before ~ each use. The meter has operator
- adjustable high and low level alarms. The . setpoints are controlled by the Operating Procedure for a partially filled condition (see' response to
. Question 5.)
Refueling' Level Indication is independent of the SDC system and would not be affected if the RCS were isolated from the SDC system. In the event of a loss of SDC- and subsequent RCS pressurization, this level indication would not be accurate since this instrument is ~ referenced to atmospheric pressure. liowever, RCS pressurization could only occur 'with the. reactor pressure vessel. head on and our procedures require maintaining the RVLMS in operation whenever possible during a partially filled condition, y
Tyson' tube level indication is connected to the same tap as the Refueling Level Indicator and provides local (in containment) indication ' of RCS level. The tygon tubing is fastened to the containment stairwell and elevations are marked at
. six-inch intervals. Permanent instrument tubing is installed from the RCS to the containment stairwell. In the event of a loss of SDC and subsequent RCS pressurization, this instrument would not be accurate.
Temperature indication is provided by SDC return temperature and Core Exit Thermocouple (CETs). The SDC return temperature transmitter senses Lcw Pressure Safety injection (LPSI) pump discharge temperature, upstream of the SDC heat exchangers, and provides indication to a recorder (0-400 F range) located in the Control Room. Local indication is also available. Core Exit Thermocouple 0
(40-2300 F range) provide Control Room indication through both a direct digital readout and the plant computer. Variable alarms may be set on the plant computer. Core Exit Thermocouple indication is only available when the reactor vessel head is installed. and the instrumentation is electrically connected.
Pressure indication is provided by four independent (separate ~ taps and power supplies) sources. Two Wide Range (0-4000 psia) and two Narrow Range (0-1600 psia) Pressurizer Pressure transmitters provide Control Room indication.
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1 ENCLOSUREil) -
. CALVERT CLIFFS RESPONSE TO G ENERJC LETTER 87-12
. Co'ntrol Room' instrumentation available for monitoring' SDC system performance are LPSI pump motor current, flowrate (0-8000 gpm range), discharge pressure (0-500
. and 0-600 psig range for Unit I and Unit 2 respectively), and SDC heat exchanger
. influent and effluent temperatures (0-400 F range). In ' addition, a LPSI pump low suction pressure alarm is installed on the suction line of each LPSI pump and provides an annunciated alarm on low suction pressure.
- 3. Identification of. all pumps that can be used to control NSSS inventory, include:
(a) pumps you require be. operable or capable of operation (include information about such pumps that may be temporarily removed from . service for testing or maintenance),
(b) .other pumps not included in item (a), and j (c). an evaluation of items (a) and (b) with respect to applicable Technical -j Specification requirements.
RESPONSE
Technical - Specifications 3.1.2.1 and 3.1.2.3 require at least one charging pump or one high pressure safety injection (HPSI) pump to be. operable during MODES 5 {
and 6. Technical Specification 3.4.1.3 requires both SDC loops (and LPSI pumps) l to be operableL for SDC during MODES 4 and 5. Technical Specification 3.9.8.1 1 requires at least one SDC loop to be in operation during. MODF 6. Finally, 7
Technical Specification 3.9,8.2 requires two SDC loops to be OPERABLE in MODE 6 when water level is less than 23 feet above the top of the irradiated fuel assemblies in the reactor pressure vessel.
In addition to the required charging pump or HPSI pump, the containment spray l pumps, spent fuel cooling pumps, or safety injection tanks may be available for l filling the system. If the RCS is at or near atmospheric pressure, the system may be gravity filled from the refueling water tank.
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- 4. A description of the containment closure condition you require for the conduct of operations while the RCS is partially fille.d. Examples of areas of consideration are the equipment hatch, personnel hatches, containment purge valves, SG l secondary-side condition upstream of the isolation valves (including the valves), l piping penetrations, and electrical penetrations, j
l One of these SDC loops may be replaced by one spent fuel pool cooling i
loop when it is lined up to provide cooling flow to the irradiated fuel in the reactor !
core and the heat generation rate of the core is below the heat removal capacity of the spent fuel pool cooling loop.
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- ENCLOSURE (1)
L ' CALVERTCLIFFS RESPONSE *ID GENERIC LETTER 87-12 ,
- i. EESPONSE:
See ~ response to - Question 1.
- 5. Reference _to and a summary description of procedures in the Control Room of--your
. plant which describe operation hil 3e the RCS is partially filled. Your response' !
should . include the analytic basis you used for procedures development. We are i particularly interested in your treatment of draindown to the condition where the I RCS is ' partially filled, treatment of minor variations from expected behavior such as ' caused by air entrainment and de-entrainment, treatment of boiling in the core with and without RCS pressure boundary integrity, calculations of approxi-mate time from loss of RHR to core damage, level differences in the RCS and the effect upon instrumentation indications, treatment of air in the RCS/RHR system, including the impact of air upon NSSS and instrumentation response, and treatment of. vortexing at the connection of the RHR suction lines (s) to the RCS.
RESPONSE
The following Operating Procedure (OP), Operating Instruction (01), and Abnormal
. Operating Procedures -(AOP) are used 'when taking the plant from a HOT STANDBY condition to a partially drained condition.
OP-5 (Plant Shutdown from HOT STANDBY to COLD SHUTDOWN)
This procedure ' provides overall guidance for draining the RCS to a partially filled condition. It refers to 01-3 (discussed below) for detailed operation of the SDC system. Specific reference is . made to . applicable Technical Specifications throughout the procedure. Cautions and notes are provided where necessary to emphasize key points. This procedure has specific steps which require; 2 Explain how your analytic basis supports the following as pertaining to' your facility; (a) procedural guidance pertinent to timing of operations, required instrumentation, cautions, and critical' parameters; (b) operations control and communications requirements regarding operations that may perturb the NSSS, including restrictions upon ' testing, maintenance, and coordination of operations that could upset the condition of the NSSS; and (c) response to loss of RHR, including regaining control of RCS heat removal, operations involving the NSSS if RHR cannot be restored, control of effluent from the containment if containment was not in an isolated condition at the time of loss of RHR, and operations to provide containment isolation if containment was not -isolated at the time of loss of RHR (guidance pertinent to timing of operations, cautions and warnings, critical parameters, and notifications is to be clearly described).
ENCLOSURE (1) ,
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CALVERT CLIFFS RESPONSE TO G ENERIC LETTE R 87- 12 o Maintaining the RVLMS in service, whenever possible, as a backup indication of RCS level, o' Comparing the tygon hose to the Refueling. Level Indicator prior to draining (they are required to be within 0.75 feet),
o Comparing the tygon hose level indication to the Refueling Level Indicator when the top of the hot leg is reached (if they do not compare within 0.75 feet, draining must be secured),
o Reducing flow to approximately, but not less than,1500 gpm with one LPSI pump operating prior to draining below the mid-plane of the hot leg (to prevent vortexing),
o Requiring a minimum RCS level of no lower than six inches below the mid-plane of the hot leg, o Comparing the Refueling Level Indicator and the RVLMS while draining (five reference comparisons are required between the bottom of the pressurizer and the mid-plane of the hot leg),
o Comparing the tygon hose to the refueling level indication upon securing draining, and o Setting the refueling level alarm to a 1 0.2 ft. band of the existing water level.
01-3 (Safety iniection. Shutdown Coolint and Containment Sorav)
This OI provides specific procedures for operation of the SDC system. In order to prevent vortexing at the LPSI suctions, a reduction of SDC flow is required prior to shifting LPSI pumps when the RCS is partially drained. Specific procedures are also provided for securing and initiating SDC to perform local leak-rate testing (in accordance with 10 CFR 50 Appendix J) of the SDC header.
AOP-3B (Loss of Shutdown Coolin_g)
This AOP provides guidance for a loss of SDC under three circumstances.
o The reactor vessel head installed and the RCS capable of being pressurized, o The reactor vessel head removed, the refueling pool reactor vessel seal ring installed and RCS in a condition to allow filling of the refueling pool, and 1
o The RCS not capable of being pressurized and the refueling pool cannot be filled.
ENCLQSURE m CALVERT CLIFFS RESPONSE TO GENERIC LETTER 87-12 The procedure, within the framework of the above scenarios, provides indications of a malfunction of the SDC system, as well as actions to promptly restore SDC based on the given indications (i.e., restoring support systems which have been lost). In order to prevent a common-mode failure, specific cautions are provided to ensure the cause of a failure of an operating LPSI pump is ascertained, prior to starting a standby LPSI pump. If SDC cannot be restored, an ALERT condition is required to be declared in accordance with our Emergency Response Plan Implementation Procedures.
Guidance is provided to the operator on approximate times (as a function of time after reactor shutdown) for the RCS to reach saturation temperature and to reach the initiation of core uncovery due to boil off. These times are based on the following assumptions: an initial RCS temperature of 150 F, the RCS is drained tc!
the bottom of the hot leg, the reactor vessel head is removed, and a previous q power history of 100% power.
In addition to the above, AOP-3B provides procedures to align the containment spray pumps to' supply SDC, and to refill the RCS after loss of SDC due to low RCS level. These procedures provide guidance on venting LPSI pumps via casing vents.
Instrumentation and critical parameters are referenced in OP-5, and 01-3, as well a required by Technical Specif4ations. Table I provides a listing of these, as well as the procedures referencing their use.
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- 6. A brief description of training provided to operators and other affected personnel that is specific to the issue of operation while the RCS is partially filled. We are particularly interested in such areas as maintenance personnel training regarding avoidance of perturbing the NSSS and response to loss of decay heat removal while the RCS is partially filled.
RESPONSf; Our Initial and Continuing operator training programs cover loss of residual heat removal with the RCS in a partially filled condition. Since these training pro-grams vary with the responsibilities assigned to an operator, each case will be discussed.
Initial Plant Operator Trainine The Auxiliary Building Operator (ABO) section of the qualification manual contains independent checks of the operator's knowledge in the following areas:
3 Checkouts by at least two people - a person knowledgeable in the specific system and a senior licensed operator.
ENCLOSUR E (1)
CALVERT CLIFFS RESPONSE TO GENERIC LETTER 87- 12 o AOP-3B, Loss of Shutdown Cooling Procedure, o Operation of the Safety Injection System when in Shutdown Cooling (OI-3), and o Plant cooldown and RCS draining procedure (OP-5) including ievel indicator operability verification by the ABO in conjunction with the Control Room Operator's verification.
Initial Licensed Oncrator Traininn The Control Room Operator qualification manual contains independent checks of the operator's knowledge in the following areas: ]s o Operation of the Engineered Safety Feature panel. !
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o Operations involving SDC (OI-3),
o Draining the RCS, including verification of the operability of ;
independent level measuring instruments (OP-5), and l d
o Response to a loss of SDC (AOP-3B), including plant simulator J operation. '
- Note -
Due to present model restrictions, the RCS cannot be simulated drained below the top of the hot leg. However, discussions held during simulator training include all aspects of system operation including indication and consequences of operation with the RCS level below minimum allowable.
1 The Senior Reactor Operator (SRO) qualification manual also contains independent i checks of the operator's knowledge, however, from a supervisory capacity. These checks include:
o Directing the initiation and termination of SDC (01-3),
o Analysis of indications to determine causes of abnormal events (AOP-3B),
o Discussions with experienced SROs regarding the loss of SDC (AOP-3B) and related industry events, o Discussions of the Refueling Operation section of the Technical Specifications, and
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ENCLOSURE (1)
CALVERT CLIFFS RESPONSE TO G ENFRIC LETTER 87-12 o Operation of the plant in a partially drained condition (OP-5),
including Technical Specification requirements and instrumentation response.
The Degreed Senior Reactor Operator qualification manual contains aspects of all the previously described qualification manuals. Plant personnel in this training program become licensed Senior Reactor Operators and fill the position of Shift Technical Advisor.
In addition to the above, all licensed operators receive formal classroom training in the operation of the SDC system. This training, reinforced with the plant simulator, includes transients involving the SDC and reactor coolant systems.
Continuinn Operator Traininn Pionram The Plant Operator Continuing Training Program reinforces the above concepts in a classroom atmosphere. SDC system operation training is given biennially. This training has concentrated on system flow paths, transient response, and actions (normal and abnormal) necessary to safely operate the SDC and reactor coolant systems.
Licensed Ooerator Recualification Trainine Pronram The Licensed Operator Requalification Training Program also contains periodic reviews of SDC system operation. Case studies have been presented to raise operator awareness of potential problems. Additionally, each operating crew has been evaluated biennially, using the plant simulator, on a loss of SDC. AOP-3D, used during these sessions, specifically addresses concerns regarding low RCS level.
Maintenance Traininn Electrical and Controls Maintenance Technician's initial and Continuing Training includes all systems that may affect residual heat removal capabilities (i.e.,
Safety injection, Reactor Coolant, Shutdown Cooling, Auxiliary Feedwater, etc).
Technicians receive in-depth training on the systems, including precautions for maintenance during abnormal plant operating conditions (e.g., plant shutdown /
partial fill and commonality of sensing lines). Specific circuits emphasized are the low pressure transmitter loops and circuits that could isolate SDC. Any plant or industry events dealing with loss of residual heat removal are addressed during our systems overview training.
- 7. Identification of additional resources provided to the operators while the RCS is partially filled, such as assignment of additional personnel with specialized knowledge involving the phenomena and instrumentation.
ENCLOSURE (I)
CALVERT CLIFFS RESPONSE TO GENERIC LE' ITER 87- 12
RESPONSE
No additional personnel are assigned to a shift while the RCS is partially -
filled. However, the Shift Technical Advisor, Operators, and other affected personnel receive specific training for operation in this condition (see response -
to Question 6).
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- 8. Comparison of the requirements implemented while the RCS is partially filled and "I requirements used in other MODE 5 operations. Some requirements and procedures followed while the RCS is partially filled may not appear in the other modes. An ~
example of such differences is operation with a reduced RHR flow rate to minimize the likelihood of vortexing and air ingestion.
RESPONSE
Prior to operating with the RCS drained to below the mid-plane of the hot leg, SDC flow is required (by OP-5) to be reduced to approximately, but not less than 1500 gpm with one LPSI pump operating. An amendment to Technical Specification 4.9.8.1 was approved on April 24, 1979, and allows reduced SDC flow (between 1500 and 3000 gpm) when RCS level is below the mid-plane of the hot leg. This amendment was based on experience that a SDC flow of 3000 gpm (minimum required at the time) at levels lower than the mid-plane of the hot leg, caused reductions in SDC flow due to vortexing. A minimum flow of 1500 gpm was found to be adequate to provide sufficient core cooling as well as prevent boron stratification.
- 9. As a result of your consideration of these issues, you may have made changes to your current program related to these issues. If such changes have urengthened your ability to operate safely during a partially filled situation, describe those changes and tell when they were made or are scheduled to be made.
RESPONSE
Over the past few years, we have reviewed NRC case study AEOD/C503 (Decay Heat Removal Problems at U. S. Pressurizer Water Reactors), Nuclear Safety Analysis Center Report NSAC-52 (Residual Heat Removal Experience Review and Safety Analysis -
Pressurized Water Reactors), as well as Significant Operating . s Experience Reports generated by INPO. Additionally, a performance study of the -
SDC system was recently completed in October 1986. As a result of all of the above, procedural changes, design modifications, and administrative requirements have been, or will be, incorporated. A summary of these are provided below, A review of applicable Operating Procedures, Operating Instructions, Abnormal Operating Procedures, and Surveillance Test Procedures was performed. The purpose was to verify that these minimized the potential for loss of residual heat removal; contained specific cautions and steps where necessary to prevent
L ENCLOSUR E (1)
CALVERT CLIFFS RESPONSE TO GENERIC LETTER 87-12 vortexing and subsequent air-binding of a LPSI pump; ensured a common mode failure would not occur by providing operators guidance to ascertain the cause of '
i loss of SDC prior to starting a standby LPSI pump; and required comparison of RCS p l level indicators during the draining process as well as periodic daily checks. i'>
Several changes to these were recommended and incorporated. v A modification to remove the auto-closure interlock on the SDC isolation valves is being planned. This will allow operators (through the use of a key-operated handswitch) to bypass, during certain conditions, the control signal which shuts the SDC suction valves on high RCS pressure. In the interim, this circuitry is bypassed by lifting leads for the auto-closure signal. Both the interim bypassing of this circuitry as well as the keyed handswitch are for use only with the reactor vessel head removed (MODE 6). In addition, the following alarms have been installed to alert our . operators of system malfunctions: a LPSI pump suction low pressure alarm and a variable RCS level alarm which can be set by the operators to a level slightly below actual RCS level.
As discussed in the cover letter, we are presently working through the Combustion Engineering (CE) Owners Group to evaluate the potential unanalyzed condition discussed in the Generic Letter. Specifically, the concern is a loss of residual
. heat removal, leading to RCS pressurization and potential ejection of coolant via l
a cold leg opening (e.g., maintenance on a RCP seal assembly). We expect to provide our response to this concern by October 15, 1987.
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ENCLOSURE fI) .;
i 4
CALVERTCL1FFS RESPONSE TO GENERIC LETTER 87-12 :
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TABLE _l_
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_7, Parameter ' Indication Procedure / Technical ':
. Specification. i;
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' RCS Level RVLMS OP-5 e . NOTE (1) Tygon Tube OP-5 Refueling Level OP-5 and 01-3 Instrumentation RCS Pressure . Wide and Narrow Range OP-5 and Technical Specification 3.4.9.1
- Temperature SDC Return Temperature OP-5. 01-3 and Technical Specification 3.4.9.1 L-SDC Flow SDC Flow 01-3 and Technical Specification 3.9.8.1 NOTE (1):
' Technical Specification 3.9,8.1 (MODE 6) references RCS level in both the surveillance requirement . and the action statement.
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