ML19309C260
| ML19309C260 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 04/03/1980 |
| From: | Parker W DUKE POWER CO. |
| To: | Baer R, Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0660, RTR-NUREG-660 NUDOCS 8004080366 | |
| Download: ML19309C260 (11) | |
Text
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DUICE POWER COSIMNY Powru Ut;st.ntxo 422 SocTn Cucucu STurr.T, CitAHIATTE, N. C. USM
..u. - a 4aaca.sa.
April 3, 1980 m,a.c.,ec~,
rc.c.-:~ c. a.c. vc 4 5 ' c a ns Paco 47.og 373-4093 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Attention:
Mr. R. L. Baer, Chief Light Water Reactors Branch No. 2
Reference:
McGuire Nuclear Station Docket Nos. 50-369, -370
Dear Mr. Denton:
As requested by your letter of January 29, 1980 concerning implementation of the recommendations of NUREG/CR-0660, " Enhancement of Onsite Emergency Diesel Generator Reliability," please find attached our response to these recommendations.
Very truly yours, f.j s William O. Parker, Jr.
LJB:scs Attachment hol5 s
/ /
8004080 3 6 6
T MCGUIRE NUCLEAR STATION EMERGENCY DlESEL GENERATOR RELIABILITY' Response to NRC's January 29, 1980 Request For Additional Information Docket Nos. 50-369/370 8.1 Provide a discussion of the measures that have been taken in the design of the standby diesel generator air starting system to preclude the fouling of the air start valve or filter with moisture and contaminants such as oil carryover and rust.
(SRP 9.5.6, Part III, Item 1).
Response
Air purifiers are provided in each diesel starting air header to prevent fouling the starting air valves. The purifiers are capable of removing moisture as well as rust or other contaminants from the starting air.
Refer to the McGuire FSAR Section 9.5.6.
t 8.2 Experience at some operating plants has shown that diesel engines have failed to start due to accumulation of dust and other deleterious material on electrical equipment associated with starting of the diesel generators (e.g., auxiliary relay contacts, control switches - etc.).
Describe the provisions that have been made in your diesel generator building design, electrical starting' system, and combustion air and ventilation air in-take design (s) to preclude this condition to assure availability of the diesel generator on demand.
Also describe under normal plant operation what procedure (s) will be used to minimize accumulation of dust in the diesel generator room; specifically address concrete dust control.
In your response also consider the condi-tion when Unit 1 is in operation and Unit 2 is under construction (abnormal generation of dust).
Response
The relay contacts, switch contacts, and other electrical devices associated with starting and operating the standby diesel generators are housed in Class IE, drip proof, bottom entry NEMA 12 control panels. These panels and all other safety related electrical equipment in the diesel room are sealed according to a detailed installation specification. Therefore, dust is not expected to degrade the reliability of the diesel generator.
The combustion air system and the ventilation air system are separate systems.
The combustion intake air for each diesel generator is taken from a location-outside the diesel building. The combustion exhaust for each diesel genera-tor is piped out of the diesel room to the outside atmosphere. The exhaust to the atmosphere is on a different side of the building from the intake air.
Section 9.5.1 of the FSAR includes the combustion intake / exhaust air system description. Due to the separation of the ventilation system from the com-bustion intake / exhaust sir system on the diesel generator we feel there is very little dust in the diesel room.
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f 1 t During normal plant operation the following measures minimize dust in the diesel generator room:
1.
Air filters in the Diesel Room Ventilation System are 36% efficient based on the NBS Atmospheric Dust Test (FSAR 9.4.6.2a).
i 2.
The floors, walls, and ceiling have been painted to inhibit concrete dust which would be generated from within the diesel rooms.
3.
The diesel rooms are a Level IV Cleanliness Area, and QC will I
periodically insure the cleanliness of the rooms through visual inspections for dust and debris.
i 4.
The Monthly Diesel Generator Halon Fire Protection Periodic Test also contains a visual inspection for debris in the diesel rooms.
5.
The Unit 1 diesels are kept in a room on the Unit I side of the plant, and the Unit 2 diesels are kept in a room on the Unit 2 side.
This separation of rooms should minimize problems with concrete dust due to Unit 2 Construction.
8.3 The diesel generators are required to start automatically on loss of all offsite power and in the event of a LOCA. The diesel generator sets should be capable of operation _at less than full load for extended periods without degradation of performance or reliability.
Should a LOCA occur j
with availability of of fsite power, discuss the design provisions and other parameters that have been considered in the selection of the diesel genera-tors to enable them to run unloaded (on standby) for extended periods with-i-
out degradation of engine performance or reliability.
Expand your FSAR to include and explicitly define the capability of your design with regard to j
this requirement.
(SRP 9.5.5, Part III, Item 7).
Response
The diesel generators have been tested for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of continuous no load running.
Immediately after the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> run a load of 1800KW (approximately 50% full load) was applied and accepted by the diesel generator. We do not recommend running the diesel at no load for extended periods of time. We feel it is detrimental to the engine's performance. There is no periodic testing of the diesel running at no load for any significant period of time.
The McGuire FSAR will be revised to define the capabilities of the diesel generators in this regard.
8.4 Section 9.5.4.1 cmergency diesel engine fuel oil storage and transfer system (EDEFSS) does not specifically reference ANSI Standard N195 " Fuel 011 Systems for Standby Diesel Generators." Indicate if you intend to comply with this standard in your design of the EDEFSS; otherwise provide justification for noncompliance.
(SRP 9.5.4, Rev. 1, Part II, Item 12).
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Response
Duke Power Company does take exceptions to certain portions ANSI Standard-l N195 " Fuel Oil Systems for Standby Diesel Generators." Note that the I
t majority of these exceptions are due to the fact that this system was designed prior to issuance of the ANSI Standard. The following sum-marizes these exceptions:
1.
The McGuire calculation of fuel oil storage requirements, as discussed 4
in Section 5.4 of ANSI N195-1976, does not allow for fuel consumption i
due to periodic testing. This was not a requirement at the time that the fuel oil tanks were originally sized.
2.
In reference to Section 6.1 of the ANS1 Standard, the day tank for the diesel has a capacity which is sufficient to maintain cpproximately 60 minutes of operation. 011'is automatically added to the day tank at approximately one-half this level.
In addition, the overflow line fron the day tank goes to the fuel oil drip tank which eventually goes to the waste oil system.
Note that tanks for the diesel were designed prior to issuance of this ANSI Standard.
Also, the diesel has been up-rated from 3500 KW to 4000 KW.
3.
In reference to Section 7.2, some of the pressure retaining components In McGuire's fuel oil system were not built to ASME Section III Code, however, materials used are generally acceptable to Code and are compat-ible with the fuel oil.
4.
In Section 7.3 of the Standard, McGuire's fuel oil system was designed with a permanent interconnection with a plant heating boiler. This boiler is automatically isolated during diesel operation.
In addition, it should be noted that a larger capacity plant heating boiler has been installed at McGuire, therefore, the plant heating boiler interconnected-with the fuel oil storage tanks will not be used on a regular basis.
5.
In reference to Section 7.4, the majority of McGuire's original fuel oil system components were not not built to applicable codes and standards, but were seismically qualified by analysis or testing prior to being installed. However, components added to the original system, such as valves, filters, and Duke supplied piping, were designed and installed to ASME Section III.
6.
In reference to Section 7.5 of the Standard, a fill-line strainer was.
not provided in the original design for the supply tank.
In addition, a flame arrestor was not provided.
It should be noted that the National i
Fire Protection Association Codes do not require a flame arrestor for the type of fuel oil being stored in this tank.
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8.5 Assume an unlikely event has occurred requiring operation of.a diesel generator for a prolonged period that would require replenishment of-fuel oil without interrupting operation of the diesel generator. What provision will be made in the design of the fuel oil storage fill system to minimize the creation of turbulence of the sediment in the bottom of the storage tank.
Stirring of this sediment during addition of new fuel ~
f has the potential of causing the overall quality of the fuel to become unacceptable and could potentially lead to the degradation or failure of i
the diesel generator.
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Response
Provisions are made in the diesel fuel oil storage systems to minimize sediment collection in the storage tanks.
Sediment will be pumped from i
I the tanks, periodically; therefore, stirring of sediment during addition of new fuel is not a potential problem.
Refer to FSAR Cection 9.5.4.
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8.6 Discuss the precautionary measures that will be taken to assure the quality and reliability of'the fuel oil supply for emergency diesel generator j
operation.
Include the type of fuel _oll, impurity and quality limitations as well as diesel index number or its equivalent, cloud point, entrained
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moisture, sulfur, particulates and other deliterious insoluble substances; i
procedure for testing newly delivered fuel, periodic sampling and testing of on-site fuel oil (including interval between tests), interval of time between periodic removal of condensate from fuel tanks and periodic system inspection.
In your discussion include reference to industry (or other) standard which will be followed to assure a reliable fuel oil supply to i
j the emergency generators (SRP 9.5.4, Part III, Items 3 and 4).
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Response
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When fuel oil is received, it is analyzed for 90% Boiling Point (to characterize the oil), viscosity, water'and sediment.
If the oil passes' these tests, then an additive to retard sediment formation is added to ' the i
tanker and the contents are transferred from the tanker to the storage. tank.
The contents of each storage tank for each unit are recirculated and sampled each month.
Prior to being placed in recirculation, oil is pumped from the bottom of the storage tank to the waste oil storage tank until a sample.
l indicates that there is visably little or no water or sediment in the oil.
i After 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> recirculation, a sample is taken and checked for water and 4
sediment, and viscosity using the following specifications.
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PARAMETER SPECIFICATION ASTM REFERENCE 90% B. P.
282 C - 338 C D86 Water & Sediment
< 0.05% V/V D-1796 Viscosity at 100 F 32.6 - 40.lSUS ASTM D-445 NOTE: Water and Sediment is an accurate measure of particulates, insolubles, and moisture content of the fuel oil.
Diesel index number, cloud point, and sulfur content numbers would be supplied by the vendor upon receipt; however, the suppliers values would be typical, not specific to a given lot of fuel.
8.7 Operating experience has shown that accumulation of water in the starting air system has been one of the most frequent causes of diesel engine f ailure to start on demand.
Condensation of entrained moisture in com-pressed air lines leading to control and starting air valves, air start motors, and condensation of moisture on the working surfaces of these components has caused rust, scale and water itself to build up and score and jam the internal working parts of these vital components thereby pre-venting starting of the diesel generators.
In the event of loss of offsite power the diesci generators must function since they are vital to the safe shutdown of the reactor (s).
Failure of the diesel engines to start from the effects of moisture condensation in air starting systems and from other causes have lowered their operational reliability to substantially less than the desired reliability of 0.99 as specified in Branch Technical Position ICSB (PSB) 2 " Diesel Generator Reliability Testing" and Regulatory Guide 1.108 " Periodic Testing of Diesel Generator Units Used as Onsite Electric Power Systems at Nuclear Power Plants."
In an effort toward improving diesel engine starting reliability NUREG-0660 indicates that compressed air starting system designs include air dryers for the removal of entrained moisture. The two air dryers most commonly used are the dessicant and refrigerant types. Of these two types, the refrigerant type is the one most suited for this application and therefore is preferred.
Starting air should be dried to a dew point of not more than 500F when installed in a normally controlled 70 F environment, otherwise the starting air dew point should be controlled to at least 100F less than the lowest expected ambient temperature.
Describe your diesel engine air starting system and indicate how your sys-tem meets the recommendation stated in SUREG-0660.
If there are any dif ferences between your design and the recommendations of NUREG-0660, pro-vide justification for your design or plans for implementation of the recommendations.
Response
The diesel generator starting air systems do not have air dryers. However, air purifiers are installed downstream of each air receiver to prevent rust, scale.and water from entering the vital components of the system. These purifiers will reduce moisture condensation in the starting air system.
. 8.8 Provide a detail discussion (or plan) of the level of training proposed for your operators, maintenance crew, quality assurance, and supervisory personnel responsible for the operation and maintenance of the emergency diesel generators.
Identify the number and type of personnel that will be dedicated to the operations and maintenance of the emergency diesel generators and the number and type that will be assigned from your general plant operations and maintenance groups to assist when needed.
In your discussion identify the amount and kind of training that will be received by each of the above categories and the type of ongoing training program planned to assure optimum availability of the emergency generators.
Also discuss the level of education and minimum experience requirements for the various categories of operations and maintenance personnel associ-ated with the emergency diesel generators.
Response
Two operators will be required to run the monthly diesel generator oper-ability test.
These operators will have been trained in operation of the diesel generator from the local control panel and will also have had train-ing on the simulator.
If any problems arise with the operability of the diesel generators, two engineers are currently responsible for overseeing repairs and insuring that operability is restored. These engineers have degrees in engineering and "llands-On" experience on the diesels.
QA inspectors that perform inspections (both mechanical or electrical) and evaluate the results of the inspection are required to be certified as a Level II inspector. The experience, level of education, amount of train-ing and type of training for an inspector required for this certification is evaluated on a case-by-case basis. The minimum requirement for certifi-cation as a Level II is a high school degree or equivalent plus two (2) years of Level I experience in testing or inspection or equivalent construc-tion, installation, or operational activities.
In addition, experience and training in the performance of required inspections and tests and in the organization and evaluation of the results of the inspection and tests is required.
The QA personnel are not assigned to inspect specific pieces of equipment.
A staff of inspectors at each nuclear station who inspect all safety related maintenance functions are maintained at each station. Whenever QC procedures are revised that would affect inspections; i.e.,
requirements, acceptance criteria, etc., training sessions are held to update inspectors.
Maintenance personnel are not assigned to a particular piece of equip-ment.
All maintenance personnel have a high school degree or equivalent.
i In addition, all maintenance personnel in responsible positions (i.e.,
l individuals who direct the activities of others, but who are not supervisors) have a minimum of three years experience in their craft.
8.9 Several fires have occurred at some operating plants in the area of the diesel engine exhaust manifold and inside the turbocharger housing which have resulted in equipment unavailability. The fires were started from
_7 lube oil leaking and accumulating on the engine exhaust manifold and accumulating and igniting inside the turbocharger housing.
Accumulation of lube oil in these areas, on some engines, is apparently caused from an excessively long prelube period, generally longer than five minutes, prior to manual starting of a diesel generator. This condition does not occur on an emergency start since the prelube period is ninimal.
When manually starting the diesel generators for any reason, to minimize the potential fire hazard and to improve equipment availability, NUREG-0660 recommends that the prelube period should be limited to a maximum of three to five minutes unless otherwise recommended by the diesel engine manufacturer.
Provide the prelube time interval your diesel engine will be exposed to prior to manual start and if this interval does not agree with the recommendations of NUREC-0660 provide justification why your interval time is acceptable.
Response
The procedure for starting the diesel generators does not specify a set time for prelube. However, prelube normally takes about one to two minutes to complete.
8.10 An emergency diesel generator unit in a nuclear power plant is normally in the ready standby mode unless there is a loss of offsite power, an accident, or the diesel generator is under test.
Long periods on standby have a tendency to drain or nearly empty the engine lube oil piping system. On an emergency start of the engine as much as 5 to 14 or more seconds may elapse from the start of cranking until full lube oil pressure is attained even though full engine speed is generally reached in about five seconds.
With an essentially dry engine, the momentary lack of lubrication at the various moving parts may damage bearing surfaces producing incipient or actual component failure with resultant equipment unavailability.
The emergency condition of readiness ccquires this equipment to attain full rated speed and enable automatic sequencing of electric load within ten seconds.
For this reason, and to improve upon the availability of this equipment on demand, it is necessary to establish as quickly as possible an oil film in the wearing parts of the diesel engine.
Lubri-cating oil is normally delivered to the engine wearing parts by one or more engine-driven pump (s).
During the starting cycle the pump (s) accelerates slowly with the engine and may not supply the required quantity of lubricating oil where needed fast enough. To remedy this condition, as a minimum, an electrically-driven lubricating oil pump, powered from a reliable DC power supply, should be installed in the lube oil system to operate in parallel with the engine-driven main lube pump. The electric-driven prelube pump should operate only during the engine cranking cycle or until satisfactory lube oil pressure is established in the engine main lube distribution header. The installation of this prelube pump should be coordinated with the respective engine manufacturer. Some diesel engines include a lube oil circulating pump as an integral part of the lube oil preheating system which is in use while the diesel engine is in the stand-by mode.
In this case an additional prelube oil pump may not be needed.
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Indicate whether your design includes an electric prelube oil pump.
If your design does not include this pump, provide justification why it is not neceasary.
Response
Each diesel engine lube oil system has a before and after lube oil pump which operates for 20 minutes every hour by means of an auto-matic timer to keep the bearings lubricated while the diesel generator unit is on standby. The before and after pump also operates during the engine cranking cycle until satisfactory lube oil pressure is established.
Refer to FSAR Section 9.5.7.
8.11 Periodic testing and test loading of an emergency diesel generator in a nuclear power plant is a necessary function to demonstrate the operability, capability and availability of the unit on demand.
Peri-odic testing coupled with good preventive maintenance practices will assure optimum equipment readiness and availability on demand. This is the desired goal.
To achieve this optimum equipment readiness status, NUREG-0660 recommends the following:
1.
The equipment should be tested with a minimum loading of 25 percent of rated load. No load or light load operation will cause incom-plete combustion of fuel resulting in the formation of gum and varnish deposits on the cylinder walls, intake and exhaust valves, pistons and piston rings, etc., and accumulation of unburned fuel in the turbocharger and exhaust system. The consequences of no load or light load operation are potential equipment failure due to the gum and varnish deposits and fire in the engine exhaust system.
2.
Periods surveillance testing should be performed in accordance with the applicable NRC guidelines (R.G. 1.108), and with the recommenda-tions of the engine manuf acturer. Conflicts between any such recommendations and the NRC guidelines, particularly with respect to test frequency, loading and duration, should be identified and justified.
3.
Preventive maintenance should go beyond the normal routine adjust-ments, servicing and repair of components when a malfunction occurs.
Preventive maintenance should encompass investigative testing of components which have a history of repeated malfunctioning and require constant attention and repair.
In such cases consideration should be given to replacement of those components with other products which have a record of demonstrated reliability, rather than repetitive repair and maintenance of the existing components. Testing of the unit after adjustments or repairs have been made only confirms that the equipment is operable and does not necessarily mean that the root cause of the problem has been eliminated or alleviated.
4.
Upon completion of repairs or maintenance and prior to an actual start, run, and load test a final equipment check should be made to assure that all electrical circuits are functional, i.e.,
fuses are in place, switches and circuit breakers are in their proper position, no
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loose _ wires, all test. leads have been removed, and all valves are in the proper position to permit a manual start of the equipment.
After the unit has been satisfactorily started and load tested, return the unit to ready automatic standby service and under the control of the control room operator.
Provide a discussion of whether the recommendations of NUREG-0660 have been implemented in the emergency diesel generator system design and how they will be considered when the plant is in commercial operation, i.e.,
i by what means will the above requirements be enforced.
Response
Monthly operability tests are conducted on the diesel generators to insure the operability and availability of the units on demand. The diesels are 3
j operated in parallel with the Duke Power grid at a 4000 KW load (>90% full load) for at least one hour. Upon completion of the test, the operators must complete the " Diesel Generator Shutdown Checklist" to insure the availability of the diesel generator on future demand..
The diesels are then returned to automatic standby under the control of the control room i
operator.
When a component has a high malfunction rate, an investigation is conducted to determine whether an inherent flaw exists in the component or whether another related component is causing the malfunction. A permanent solution to the problem which avoids repetitive repair is pursued. Moreover, QC oversees all maintenance performed on the diesel generators.
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8.12 The availability on demand of an emergency diesel generator is dependent upon, among other things, the proper functioning of its controls and monitoring instrumentation. This equipment is generally panel mounted and in some instances the panels are mounted directly on the diesel generator skid. Major diesel engine damage has occurred at some operat-i ing plants from vibration induced wear on skid mounted control and monitoring instrumentation. This sensitive instrumentation is not made to withstand and function accurately for prolonged periods under continuous vibrational stresses normally encountered with internal combustion engines.
Operation of sensitive instrumentation under this einvironment rapidly deteriorates calibration, accuracy and control signal output.
Therefore, except for sensors and other equipment that must be directly mounted on the engine or associated piping, NUREG-0660 recommends that the controls and monitoring instrumentation be installed on a free standing floor mounted panel separate from the engine skids, and' located on a vibration free floor area or equipped with vibration mounts.
Provide a description of how the controls and monitoring systems are installed and indicate how your design addresses the recommendations of NUREG-0660.
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Response
The diesel generator control panels are mounted on a skid which is secured to the diesel room floor. The diesel room floor is vibration free.
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. The control panel skid is completely separated from the engine generator skid and is not connected physically in any way.
Therefore, the control panel should not be subject to vibrations.
In addition, the only equip-ment that is mounted on the engine are sensors which provide input to the control panels. The design is in accordance with NUREG-0660 on the mounting of the diesel control panels.
8.13 Experience at operating plants has shown that a diesel engine that is provided with an engine cooling water temperature control system employing a 3-way bypass-type thermostatically controlled valve have demonstrated consistent trouble free operation over engines provided with other methods of temperature control such as shutter controls on radiators.
Does your system employ a water thermostat of the 3-way or bypass-type which splits the water flev so only as much water passes through the cooler or radiator as needed to maintain the proper outlet temperature? If your engine cooling water system does not use a 3-way valve, describe your installed system and justify its design as opposed to a design employing a 3-way valve.
Response
Each diesel engine cooling water system does employ a 3-way temperature control valve.
Refer to FSAR Section 9.5.5.
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