ML20235C019
| ML20235C019 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 09/18/1987 |
| From: | Nauman D SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Miraglia F Office of Nuclear Reactor Regulation |
| References | |
| GL-87-12, NUDOCS 8709240321 | |
| Download: ML20235C019 (9) | |
Text
-_____-__ _ _ _ _
7 l
ro na Electric & Gas Company a
N n
Columbia, SC 29218 Nuclear Operations (803) 748-3513 SCE&G September 18,1987
\\
Mr. Frank J. Miraglia Associate Director for Projects Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. L. 20555
SUBJECT:
Virgil C. Summer Nuclear Station Docket No. 50/395 Operating License No. NPF-12 Response to Generic Letter 87-12
Dear Mr. Miraglia:
Attached is the South Carolina Electric & Gas Company (SCE&G) response to Generic Letter 87-12," Loss of Residual Heat Removal While the Reactor Coolant System is Partially Filled," which is being provided pursuant to 10 CFR 50.54(f).
1 SCE&G recognizes the seriousness of the loss of RHR events which have occurred in I
the past few years. SCE&G, while certainly supportingin principle many of the proposed corrective actions addressed in Enclosure I to the Generic Letter, also recognizes the generic aspect of many of these concerns. We recommend that the Nuclear Regulatory Commission coordinate the resolution of these generic concerns through NUMARC and the industry owner's groups as appropriate.
Meanwhile, we are proceeding with several procedural changes as identified in the answer to question nine.
A The statements and matters set forth in this submittal are true and correct to the best of my knowledge, information and belief.
Very truly yours,
$dh
-~ f D. A. Nauman MDB/ DAN:bjh Attachment pc:
O. W. Dixon, Jr.fr. C. Nichols, Jr.
C. L. Ligon E. C. Roberts R. M. Campbell O. S. Bradham K. E. Nodland D. R. Moore J. C. Snelson W. A. Williams,Jr.
G. O. Percival Group Managers R. L. Prevatte W. R. Baehr J. B. Knotts, Jr.
hk C. A. Price RTS R. B. Clary NPCF 0
W. R. Higgins File
\\
W. T. Frady
- M. D. Blue 8709240321 870918 PDR ADDCK 050003 %
P PDR
Attachment to Mr. Miraglia Letter September 18,1987 l
Eage 1 of 7-1 QUESTION 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 ofinformation required are the time between full power operation and reaching a partially filled condition (used to determine decay heatloads); 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; restrictions regarding testing, operations, and maintenance that could perturb the nuclear steam supply system (NSSS);
ability of the RCS to withstand pressurization if the reactor vessel head and steam generator manway are in place; requirements pertaining to isolation of containment; the time required to replace the equipment hatch should replacement be necessary; and requirements pertment to reestablishing the integrity of the RCS pressure boundary.
RESPONSE
The reactor plant will enter mid-loop operations (half-pipe) from MODE 5 typically in preparation for a refueling outage. The plant is required to be in half-pipe for steam generator manway removal and nozzle dam installation and for reactor coolant pump seal maintenance, in addition, the plant may require half-pipe operations under forced outage conditions for the repair of these as well as certain other RCS components.
It should be noted, however, that it is the policy of this Station to minimize the length of time spent in half-pipe operations. During refueling outages involving steam generator maintenance, nozzle dams are used so that the plant is in half-pipe only during the time it takes to install and later to remove nozzle da ms.
In terms of the vulnerability of the plant to loss ofresidual heat removal (RHR) system the most limiting condition would occur in a forced outage situation where the plant would enter half-pipe as soon after shutdown as is practical.
Operating experience suggests that the plant could realistically enter hal(-pipe approximately two days afler shutdown. If the plant had been operating for a substantialperiod of time. the decay heat rate could be significant. In contrast, entry into half-pipe during a refueling outage will typically take place approximately five days after sh utdown since half-pipe entry is usually delayed by the increased plant preparations necessary for the outage.
Prior to draindown to half-pipe. the plant is required per Technical Specifications, Section 3.4.1.4.1, " Reactor Coolant System, Cold Shutdown-Loops Filled," to have at least one RHR train in operation and either an additional RHR train opera ble or two steam generators with levels greater than 10% wide range. Once the reactor vessellevel has been drained to a level below the top of the RCS loops the giant is required per Technical Specifications, Section 3.4.1.4.2, " Reactor Coolant System, Cold Sh utdown-Loops Not Filled,"
I to have at least one RHR train in operation and the other operable.
With respect to changes in the status ofequipment, no additional requirements I
have been established for half-pipe operation. All changes in the status of the I
r--_-
. Attachment to Mr. Miraglia Letter.
. September 18,1987 Page 2 0f 7 plant are coordinated through the Shift Supervisor and are formally controlled '
by the maintenance work request, preventive maintenance or surveillance test programs.
Should a loss ofRHR result in core boiling with an intact RCS, the RCS and 1
RHR system would be able to withstand any resultingpressurization. The most limiting component would be the tygon tube reactor vessellevelindication which should withstand approximately 100 psi. The RHR suction isolation valves are interlocked to shut in ihe event that RHR pressure exceeds 700 psi. Further, the RHR suction relief valves, with a set pressure of450 psi, would be available to mitigate overpressure transients. The Shift Supervisor is required to evaluate the loss ofRHR against the criteria for emergency action levels in accordance with EPP-001, " Activation andImplementation ofEmergency Plan," and would declare an action level appropriate to the event. The establishment of containment integrity upon loss ofRHR in half-pipe is not currently required in EOP-2.4, " Total Loss of Residual Heat Removal System," nor is contain ment integrity required for half-pipe operations. Past experience has shown that the equipment and personnel hatches can be restored in less than one hour. Further, I
there are no requirements for the integrity of the RCS for half-pipe operations.
QUESTION 2:
A detailed description of the instrumentation and alarms provided to the operators for controlling thermal and hydraulic aspects of the NSSS during
- operation with the RCS aartially filled. You should describe temporary connections, piping, anc instrumentation used for this RCS condition and the quality control process to ensure proper functioning of such connections, piping, and instrumentation,includin ? assurance that they do not contribute to loss of RCS inventory or otherwise end 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 RH R function may be lost.
RESPONSE
The plant operators have instrumentation and controls available for monitoring
}
and controlling the thermal and hydraulic aspects of the RCS in normal half-
\\
pipe operation. A notable exception to the monitoring capability can occur
}
duringpreparations for refueling when the core thermocouple are disconnected.
Upon a loss ofRHR with thermocouple disconnected. the operators will have no direct means of monitoring core temperatures.
IfRHR is lost, the operators should have wide range pressure indication as well as two RCS level indications - reactor vessel level indication system (R VLIS) i upperplenum and the locally installed tygon tu be. It is possible, however, for R VLIS surveillance testing to remove the pressure indication and upper plenu m reactor vessel levelfrom service.-
The Station assures proper functioning of the locally installed tygon tube by stationing an operator to monitor level. Further, this operator maintains positive communication with the control room.
Attachment to Mr. Miraglia Letter L
September 18,1987 f
-Page3of7 i,
The following table lists the controls and indications available to the operator:
CONTROL AND INDICATION A VAILABLE TO THE OPERATOR MCB INDICATION:
INDIC T ON INCREMENTS RHR Pump Amps 0-500 amps 10 amps RHR Flow 0-5000 gpm 100 gpm RHR Heat Exchangerinlet Temperature 50-400 F 10*F RHR Heat Exchanger Outlet Temperature 50-400*F 10*F RHR Pump Discharge Pressure 0-700 psig 10 psig RCS Wide Range Pressure 0-3000 ps,ig 50 psig 0-600 psig 10psig Reactor Vessel LevelIndication System Narrow Range 0-120%
2%
Upper Plenum 64-120%
1%
MCB ALARMS (XCP-610):
ALARM CONDITION RHR Pump Trip MCB Switch l Breaker Mismatch RHR Loop Flow Low.
2200 gpm with Breaker Closed RHR Discharge Pressure High 550psig RCS Temperature Low and RHR Suction RCS Temperature <300 Fand Valves Not Open any RHR suction valve not fully open.
COMPUTER POINT ALARMS:
Para meter -
High Alarm Law Alarm RHR Flow 4500 gpm 2400 gpm RHR Pump Breaker Open RHR Heat Exchanger Outlet Temperature 345 F 55 F RHR Pump Outlet Temperature 345 F 55 F RCS Wide Range Pressure 2300 psig 325 psig Incore Thermocouple 635 F 523.2 F LOCALINDICATION:
Tygon Tube B Loop Intermediate Leg to Pressurizer Steam Sample Line.
Markings are permanently on the wall of the RB.
l i
Attachment to Mr. Miraglia Letter i
September 18,1987 j
Page 4 of 7
)
QUESTION 3:
Identification of all pumps that can be used to control NSSS inventory.
Include: (a) pumps you require to be operable or capable of oper ation (include information about such pumps that may be temporarily removed from service for testing or maintenance); (b) other pumps not included in item a (above); and (c) an evaluation ofitems a and b (above) with respect to applicable TS requirements.
RESPONSE
a)
With the RCS in half-pipe and vented, the plant has a single chargingpump and two boric acid transfer pumps available to control NSSS inventory. In addition the refueling water storage tank (R WST) can passively supply water to the RCS through the chargingpump or RHR pump suctions.
b) Two other chargingpumps are required to be " tagged out," but could be available for service if required. Technical Specifications, Section 3.1.2.4,
" Reactivity Control Systems, Charging Pumps - Operating," limits the number ofoperable charging pumps to one with the RCS less than 300 F.
QUESTION 4:
A description of the containment closure condition you require for the conduct of operations while the !1CS is partially filled. Examples of areas of consideration are the equipment hatch, personnel hatches, containment purge valves, SG secondary-side condition upstream of the isolation valves (including the valves), piping penetrations, and electrical penetrations.
RESPONSE
The Station does not impose any additional restrictions on the containment closure condition with the plant in half-pipe versus those restrictions for MODE 5 operations.
QUESTION 5:
lleference to and a summary description of procedures in the control room of your plant which describe operation while the itCS is partially filled. Your response should include the analytic basis you used for procedures i
development. We are particularly interested in your treatment of draindown to the condition where the itCS is partially filled, treatment of minor variations from expected behavior such as caused by air ent sment and de-entrainment, treatment of boiling in the core with and without itCS pressure boundary integrity, calculations of approximate time from loss ofIIHit to core damage, level differences in the itCS and the effect upon instrumentation indications, treatment of air in the ItCS/Iti-ilt system,
Attachment to Mr. Miraglia Letter September 18,1987 Page 4 of 7 l
QUESTION 3:
Identification of all pumps that can be used to control NSSS inventory.
Include: (a) pumps you require to 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 (above); and (c) an evaluation ofitems a and b (above) with respect to applicable TS requirements.
RESPONSE
a) With the RCS in half-pipe and vented, the plant has a single charging pump and two boric acid transferpumps available to controlNSSS inventory. In addition the refueling water storage tank (R WST) can passively supply water to the RCS through the charging pump or RHR pump suctions.
b) Two other chargingpumps are required to be " tagged out," but could be available for service ifrequired. Technical Specifications Section 3.1.2.4,
" Reactivity Control Systems. Charging Pumps - Operating," limits the number ofoperable charging pu mps to one with the RCS less than 300 F.
QUESTION 4:
A description s'the containment closure condition you require for the conduct of operations while the ItCS is partially filled. Examples of areas of consideration are the equipment hatch, personnel hatches, containment purge valves, SG secondary side condition upstream of the isolation valves Oncluding the valves), piping penetrations, and electrical penetrations.
RESPONSE
The Station does not impose any additional restrictions on the containment closure condition with theplant in half-pipe versus those restrictions for MODE 5 operations.
QUESTION 5:
Iteference to and a summary description of procedures in the control room of your plant which describe operation while the IICS is partially filled. Your response should include the analytic basis you used for procedures development. We are particularly interested in your treatment of draindown l
to the condition where the ItCS 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 itCS pressure l
boundary integrity, calculations of approximate time from loss of IllIII to core da mage, level differences in the itCS and the effect upon l
instrumentation indications, treatment of air in the ItCS/Itlift system, i
i I
I Attachment to Mr. Miraglia Letter b
September 18,1987 Page 5 of 7.-
including the impact of air upon NSSS and instrumentation response, and
. treatment of vortexing at the connection of the RHR suction line(s) to the RCS.
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 regainlag control of RCS heat removal, operations involving the NSSS if RHR cannot be restored, control ofeffluent from the containment if containment was not in an isolated 1
condition at the time ofloss of RHR, and operations to provide containment
' isolation if containment was not isolated at the time of J oss of RH R (guidance pertinent to timing of operations, cautions and warnings, critical parameters, and notifications is to be clearly describecl).
RESPONSE
Plant draindown to half-pipe is controlled by two procedures: General Opera ting Procedu re (GOP) 10, " Preparation For Refueling," and System Operating Procedure (SOP) 101, " Reactor Coolant System." GOP-10 governs the specific requirements toplace theplant in MODE 6. Forplant draindown, GOP-10 refers to SOP-101 for specific operations. SOP-101 establishes the valve lineup required forplant draindown and also places the local tygon tube water levelindicator in-service. Positive communications are established between the
- control room and a plant operator positioned to observe local reactor vessel level.
Emergency Operating Procedure (EOP) 2.4, " Total Loss ofResidual Hea t RemovalSystem,"specifically addresses the condition ofloss ofRHR in half-pipe, considering both cases with the RCS being intact and not intact. In the case ofa not intact RCS, EOP-2.4 requires flooding the RCS from the R WST through either the RHR or chargingpump suctions. Water from the RCS will be recirculated by using the reactor building spray pumps to pump water back to the R WST. The R H ST can be cooled by utilizing the spent fuel cooling system.
In the case with an intact RCS, EOP-2.4 requires filling the reactor vessel using the charging system and establishing 50 F subcooling by pressurizing the RCS.
Core cooling is established by employing the steam generators as a heat sink.
In regard to an analytic basis for half-pipe operations, the Westinghouse Owner's Group (WOG) is considering a program to develop specific analyses to define the limitingparameters for system operations. This program will be presented at the WOG general session meeting on September 24,1987. As a member of WOG, SCE&G willparticipate in this program. if accepted.
i l
Attachment to Mr. Miraglia Letter September 18,1987
, Page 6 of 7 QUESTION G:
A brief description of training provided to operators and other affected personnel that is specific to the issue of operation while the ItCS 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 ItCS is partially filled.
RESPONSE
The plant operators are formally trained on half pipe operations prior to each refueling outage. Training consists ofreview and discussion in a classroom setting of the relevant loss ofRHR operating experiences. Additionally EOP-2.4 is covered as a part ofLicensed Operator Requalifiation training.
The responsibility for RCS inventory management rests with theplant operators and not the maintenance technicians; therefore, this Station does not specifically train maintenance technicians on the control of maintenance activities which could perturb the RCS inventory nor are they trained on the actions required on loss ofRHR. As mentioned in ihe response to Question 1, all maintenance activities are controlled through the Shift Supervisor.
QUESTION 7:
Identification of additional resources provided to the operators while the ItCS is partially filled, such as assignment of additional personnel with specialized knowledge involving the phenomena and instrumentation.
RESPONSE
The only additionalperson assigned during half-pipe operations is the operator who monitors the standpipe level indicator. This operator is aware of the requiremen ts of maintaining the standpipe clear ofobstructions and of maintaining constant communications with the control room.
QUESTION S:
Com parison of the requirements implemented while the itCS is partially filled and requirements used in other Mode 5 oper,tions. Some requirements and procedures followed while the ItCS is partially filled may not appear in the cther modes. An exam;.le of such differences is operation with a reduced 1(1111 flow rate to minimize the likelihood of vortexing and air ingestion.
Attachment to Mr. Miraglia Letter September 18,1987
,.Page 7 of 7
RESPONSE
Procedurally, half-pipe operating requirements are the same as those implemented for Mode 5 with the exception that the reactor makeup water system is isolated from the RCS.
QUESTION 9:
As a result of your consideration of these issues, you may have made changes I
to your current program related to these issues. If such changes have l
strengthened your ability to operate safely during a partially filled situation, j
describe those changes and tell when they were made or are scheduled to be j
made.
RESPONSE
I The Station has reviewed the events as described in this Generic Letter,IEN 87-
\\
23, " Loss ofDecay Heat Removal Du ring Low Reactor Coolant Level Operation,"
and NUREG-1269, " Loss ofResidual Heat Removal System." Station procedures will be revised, by December 31,1987, to incorporate the following i
additions.
Refueling containment integrity will be restored on loss ofRHR with the a.
RCS open to the reactor building.
i b.
On loss ofRHR due to vortexing, the operators willinitially reduce flow and then align the idle train ofRHR to the R WST, instead ofstarting a second RHR pump.
i The initiating criteria for the emergency classifications for loss ofRHR will c.
be clarified.
Possibleplant modifications will be investigated to assure that RCS pressure, temperature, and level indication will be available at all times in half-pipe operation, i
1 I
I l
>