ML20092G771
| ML20092G771 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 06/15/1984 |
| From: | Woolever E DUQUESNE LIGHT CO. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| 2NRC-4-081, 2NRC-4-81, NUDOCS 8406250226 | |
| Download: ML20092G771 (10) | |
Text
hQ 2NRC-4-C81 (412) 787-$141 (412) 923 - 1960 Telecopy (412) 787-2629 June 15, 1984 Nuclear Construction Division Robinson Plaza, Building 2. Suite 210 Pittsburgh, PA 15205 United States Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Mr. Darrell G. Eisenhut, Director Division of Licensing Of fice of Nuclear Reactor Regulation
SUBJECT:
Beaver Valley Power Station - Unit No. 2 Docket No. 50-412 Identification of Backfit Requirement Number 4 Gentlemen:
On April 27, 1973, Duquesne Light Company (DLC) provided a descrip-tion of the Air Starting Systems for Emergency Diesel Generators in Amend-ment 4 to the Beaver Valley Power Station Unit 2 (BVPS-2) Preliminary Sa fe ty Analysis Report (PSAR).
This desc ript ion is included here as.
On November 9, 1973, the U.S. Atomic Energy Commission issued the Construct ion Permit stage Safety Evaluation Report (CP-S ER).
The CP-SER, in review of the proposed Emergency Diesel design (Att,achment 2) s t at es_,
"We have concluded that this design commitment is acceptable."
On September 19, 1983, the NRC staff issued ques tions 430.97 and 430.100 (Attachment 3).
Question 430.100 states, "... we require that compressed air starting system designs include air dryers fo r the removal of entrained moisture."
In this question, the NRC staf f directs, " Revise your design of the diesel engine air starting system accordingly...." (originally Attachment 3 to DLC letter 2NRC-4-032, dated March 28, 1984) also includes the DLC responses to questions 430.97 and 430.100.
In these responses DLC has appropriately addressed the technical aspects of the question.
A draf' copy of this response had previously been provided to the staff reviewer.
In a telephone conference with DLC (February 22, 1984), the staff reviewer indicated that his concerns were not satis fied and that air dryers would be required. He cited NUREG/CR 0660, " Enhancement of On-s it e Emergency Diesel Generator Reliability" (the Un ivers ity of Dayton study referenced in question 430.100) as his basis for requiring that DLC install air dryers.
Section 9.5.6 of the Standard Review Plan (SRP), Rev. 2, July 1981, has incorporated the recommendations of NUREG/CR 0660 as guidance in Para-graph 11.4.
However, Paragraph III of this section states:
"The procedures below are used during the construction permit (CP) review to determine that the design j
criteria and bases and the preliminary design as set 0
8406250226 840615 PDR ADOCK 05000412 E
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Unitsei States Nuclesr Regulatory Commission Mr. DIrrell G. Eisenhut, Director Page 2 forth in the preliminary safety analysis report meet the accept ance criteria given in subsection II of this SRP section.
For the review of operating license (OL) applications, the procedures are used to verify that the initial design criteria and bases have been appro-priately implemented in the final design as set forth in the final safety analysis report."
The requirement to change the system de s ign, after the initial design was approved at the issuance of the CP is a "backfit" as ident if ied in 10CFR50.109.
The change in the implementation of the SRP review proce-dure represents a new pos it ion on requirements and is identified as a "backfit" in Generic Letter 84-08 and the implementing NRC procedures.
DLC requests that the proposed requirement be submit ted to NRC management fo r approval, in accordance with the Of fice of. Nuclear Reactor Regulation (NRR) procedure for management of plant specific backfitting, prior to transmittal as a licensing requirement.
DUQUESNE LIGHT COMPANY By
-E VJ. Woolever r
Vice President RW/wjs At tachment s cc:
Mr. H. R. Denton (w/ attachments)
Mr. G. W. Knighton, Chief (w/ attachments)
Ms. M. Ley, Project Manager (w/ attachments)
Mr. M. Licitra, Project Manager (w/ attachments)
Mr. G. Walton, NRC Resident Inspector (w/ attachments) k
ATTACHMENT 1
.+-
BVPS-2 PSAR Amandasnt 4 4/27/73 Air Starting Systems for Emergency Diesel Generators
(
Design Basis j
Separate air starting systems are provided for the emergency l
diesel generators.
Each diesel generator is isolated from the I
other diesel generator.
The emergency diesel generator air starting system is shown in i
Fig. Response 8.12 (2)-1.
Each diesel engine drive is provided i
with 2
independent redundant starting systems, both capable of i
starting the engine without outside power.
Each independent
~
starting system includes an ac motor-driven air compressor, air storage tanks, air starting
- motors, all necessary valves and f itt i ngs,
and complete instrumentation and control systems.
All l
components will be missile protected, seismic Category I l
equipment.
The air storegn tanks capacity is capable of providing 5
generator engina starts without outside power.
The tanks are made of welded steel plate and will conform in all respects to the latest publi shed edition of ASME Boiler and Pressure Vessel Code,Section III, Nuclear Power Plant Components, Class 3.
i system Design and operation j
l Each diesel engine 1.5 supplied with 2 independent air starting I
sy st ems, both capable ot starting the engine.
The air startinq system is shown in Fig. Response 8.12 (2)-3.
t A
2 position preferred start selector switch is provided to determine which bank of dual air starting motors will be used for the initial start.
Position 1 will engage the starting motors on the left side of the engine (viewing from the generator end) and Position 2 engages air starting motors on the right side of the i
engine.
l Upon receiving a start signal, the solenoid valve is energized, allowing air from the tanks to pass through the solenoid valve to l
the pinion gear end of the lower starting motor.
The entry of l
air moves the pinion gear forward to engage with the engine ring t
l gear.
Movement of the pinion gear uncovers a port, allowing air j
pressure to be released to the upper starting
- motor, which, in i
l
- turn, engages its pinion gear with the engine ring gear.
With both pinion gears engaged, the air is released from the uncovered port in the upper motor.
The released air closes the air relay valve, which, in turn, opens the air starting valve and releases i
the main starting air supply.
Starting air passes through the air line lubrica tor, releasing an oil-air mist into the starting l
motors.
The multivane motors drive the pinion gears, rotatinq the ring gear, and cranking the engine.
t i
Q8.12 (2)-7
O CVPS-2 PSAR Am2ndment 4 4/27/73 The engine will start with one bank of dual air starting motors, but if the unit is placed in the standby mode of ope ra tion,
the starting system will automatically proceed through the f ollowing cranking sequence to ensure starting:
1.
One bank of dual air starting motors cranks the engine, depending on the selector switch setting.
If the engine fails to start within 3 sec, the air starting motors shut down.
2.
Following a
1/2 sec pause,
both banks of dual air starting motors crank the engine.
If the engine fails to start within 3
- sec, the air starting motors shut i
down.
3.
Following a
1/2 sec pause, the other bank of dual air starting motors (the bank not used in Step 1) cranks the engine.
If the engine fails to start within 3 sec, the air starting motors shut down.
The air compressor arrangement contains an electric motor-driven compressor on one bank and a combination electric moto r/ design engin e-driven compressor on the other bank, with separate air storage tanks provided for each bank.
The air compressors are equipped with a pressure operated control switch that automatically operates the electric motor when the air pressure in the air storage tanks drops to 175 psi and shuts of f the electric motor when the air pressure reaches 200 psi.
The diesel engine is a manual start engine with an automatic stop when the air pressure reaches 200 psi.
Prior to use, the diesel engine also requires a manual belt changeover f rom the electric moto r.
Eva luation The design incorpora tes sufficient redundancy to prevent a
malfunction or failure of an active or pa ssive component from I
impairing the ability of the system to start the diesel engine.
Specifica lly, the air starting system for each diesel is designed to remain operable under any one of the following conditions:
failure of any one starting air l
1.
Main tenance outage or compres sor.
2.
Maintenance outage or f ailure of any one bank of storage J
tanks.
l 3.
Maintenance outage or f ailure of any one set of dual air l
l starting motors.
Q8.12 (2) -8
BVPS-2 PSAR Amendment 4 4/27/73 4.
Maintenance outage or failure of any one s tarting valve I
and/or piping.
Tests and Inspections j
The air starting system will be hydrostatically tested durinq cons truction, and-all active system components a re functionally tested during
- startup, and periodically thereaf ter.
The air i
storage tanks are periodically checked for water, oil,
- sediment,
[
etc.,
to determine possible contamination or corrosion.
The frequency of the periodic tests is given in Section 16.
C o. 4,- L iv.. Aim I.. com m..d Emiouoi Sroucm. Ivs E.. y m..w r kDiesel Generators NDesignBasis I
Each e rgency diesel generator is supplied with its separate
[
air inta and exhaust system.
The system is designe to supply sufficient combustion air to operate the diesel e Ine at rated power during worst atmospheric conditions.
[
i Each diesel ge ator is isolated from the ot diesel generator
[
by a missile-proo wall.
Each independent ntake and exhaust system will be 1
ated in the cubic 1 of the diesel that it serves.
This desig incorporates su icient redundancy to i
prevent a
malf unction or failure an active or passive j
component from impairing e ability f at least one emergency diesel generator to f unctio prope y.
The intake and exhaust sys s will be missile protected and designed to seismic Category re irenents.
r System Design and ope tion
'N l
g The arrangement of e
Diesel Gener or Building is shown in Fig. 15.1-23.
Each abustion air intak and exhaust system consists of:
l 1.
Two
_or-operated inlet dampers
[
C sists of missile-protected redundant dam rs to allow ombustion air into the diesel cubicle, j
Engine air intake filter assembly Consists of 9
panel type oil bath filters that re
~
mounted on the main generator.
i f
08.17(2)-9 l
r o
AMENDMENT 4 4/27/?3
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\\ AIR DISCHARGE AIR STARTING 0025*
7
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MOTORS O
LOW AIR
- PORTr, c'-
PORT LOW AIR PRESSURE SWITCH O Y
Pac $5uat S*c" rLvWHEEL API T
l-.
3 RING GEAR (
AP2 d'
d
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-m G
g7 STR AIN ER ghB S RTING CA OR A
FLEXIBLE SOLEN 0lO CONNECTION V A LV E pp FE VALVE I
l hd AIR TANK g
Y FM
)
C
}*i h
h 4
h l
l-M
)
(
}*i l
c o-- 4 l
w-
-r
- - -- - s SHUTOFF VALVE (NORMALLY CLOSED)
REFER CHECM VALVE 4 L RELIEF
' NOTE VALVE AUTOMATIC PRESSURE OPER ATED f
CONTROL SWITCH Ql
^j " M!*0,,),5;,'"*$'-
$5UCtEO'o'EIEET$fNi ORIVEN COMPRESSOR COMPRESSOR NOTE:
To drive compre.or with gine,beit FIG. RESPONSE 8.12(2)-3 must be enenged over menvairy.
g BEAVER VALLEY POWER STATION-UNIT 2 PRELIMINARY SAFETY ANALYSIS REPORT l
f~
ATTACHMENT 2 8_4 The safety loads for Beaver Valley Unit 2 will be distributed evenly between the two distribution systems with the exception of those loads that provide extra redundancy, such as the high pressure injection pump and service water pump. Each of these loads can be powered from either distribution system through separate breakers and one isolating transfer switch which aligns the load to the b
selected distribution system bus. The selection of the power feed will be accomplished manually through key-interlocked bus-transfer switches which prevent interconnection of the power supplies.
In addition, the design will include the capability for discon-necting selected loads from the emergency buses that will not be required to operate during the containment isolation phase B of the accident which encompasses spray actuation. The applicants have stated that this capability will be provided to protect against diesel generator overloading. Since the diesel generators have not been selected, the need for this load shedding capability has not been established. Should this capability be required, we will evaluate it when the characteristics of the diesel generators are known.
However, we believe that this capability can be satisfactorily Laplemented and, thus, satisfies our present evaluation requirements.
The applicants have not selected the diesel generator units for this plant. However, to satisfy our requirements, they have agreed to obtain a diesel generator (s) that has been previously qualified l
l
f I
8-5 for use in nuclear power plant applications or to perform qualification tests on a new diesel generator (s) that will demonstrate a 0.99 reliability at 95% confidence level.
Further, each diesel generator will be selected and sized in accordance with the recommendations of AEC Regulatory Guide 1.9.
We have concluded that this. design commit-l ment is acceptable.
";;h di :;l ;;;:::::: rill 5: ;t; :tically :ts ::d :: ;; ;;d::
tage signal from its respective 4160 volt emergency bus, on a safety ection signal, or on opening.of either of the two series isolation br rs through which offsite power is being suppl to the emergency buse If offsite power is not available e 4160 volt emergency buses vi be automatically isolate from all supply sources and all outgoing feed breakers wil e tripped. The tically to their respective diesel generators will be connecte u
4160 volt emergency bus and the ety lo s will be automatically connected in a predetermine sequence to their spective diesel generator.
Our review the proposed a-c emergency onsite power stem revealed t the independence of the redundant emergency buses uld be ronised through a single bus tie breaker connecting the redun t
4160 volt load center buses. We consider this design arrangement C
ATTAQlMENT 3 Respone to FSAR Ouestions 430.97 and 430.100
(.
U Question 430.97 (Section 9.5.6)
P 'v ide a discu s s ion of the measures that h ave be e n t ake n in the des ign of the standby diesel generator air start ing sys tem to pr ec lude the fouling of the air start valve or filt er with moisture and cont am-inant s such as oil carryover and rust (SRP 9.5.6, Part III).
Response
Refer to the response to question 430.100.
Question 430.100 (Section 9.5.6) n A study by the (*nive rs ity of Dayton has shown that accumulation of water in the s t art. ing air sys tem has been one of the mos t freque nt causes of diesel engine failure to start on demand.
Condens ation of ent ra ined moisture in compressed air lines le ading to control and start ing air valves, air start moto rs, and condensation of moisture on the wo rking surfaces of these components has caused ru s t, sc ale, and water itself to build up and score and jam the internal working part s of these vit al compo nent s thereby preventing start ing of the diesel ge ne rato rs.
In the event of los s of offsite po'we r, the diesel ge ne rato rs must function since they are vital to the safe shutdown of the reactor (s).
Failure of the diesel engines to start from the ef fect s of mois ture condens ation in air s tart ing sy s tems and from other cau ses have lowe red their ope rat ional reliability to substantially less than the des ired reliability of 0.99 as speci fied in Branch Technical Pos ition ICSB (PSR) 2, " Diesel Generator Reliability Tee ting," and Regulatory Guide L.108, " Periodic Tes t ing of Dies el Generato r tinits used as Ons ite Electrical Power Systems at Nuclear Power Plant s."
l In an ef fort toward improving diesel engine s tart ing reli ab ili ty,
we require that compressed air start ing sys tem des igns include air dryers for the removal of entrained moisture.
The two air drye rs mo s t can-monly used are the de s s icant and re f r ige rant types.
Of these two t y pe s, the refrigerant ty pe is the one mos t suited to r th is ap plic a-t io n and, therefore, is preferred.
St art ing air should he dried to a dew point of not more than 50*F when ins t al led in a nonnal l y coo-t rolled 70* F environment, otherwise, the start ing air dew point shoul d l
be controlled to at le as t 10*F less than the lowes t expect ed amb i ent t empe ra tur e.
Revise your de s ign of the diesel eng i ne air s t art ing sy s t em ac c o rd-ing ly, desc ribe th is feature of your iles ign.
Also expant voor FS AR to d i sc u ss the procedures that will be fo l lowed to ensure the dr ve rs are
--g
,,/
wo rki ng properly amt the f r eq im* ne v of check i nn/ r es t ine (MRP o.5.6 part s II a nl til).
.,,-..---,,,.n
---n-
+ -, - < ~ ~ -
O hsponse The Univers ity of Dayton study which concluded that water accumulation was a le ad i ng cause of diesel st art ing failures was based upon analy-p*
s is of L ic e ns e e Eve nt Repo rt s ( LE R) issued fr om 19 64 through 1977.
Impr ov eme nt s in industry practices since that time, and the succes s of such pr ac t ic e s must al.so be cons id e red.
During the firs t ye ar of operation ( 1976-1977) at BVPS-1, two f ailures of the diesel generators to start be cau se of mois ture we re repo rt ed via LER.
To pr ev ent fur-ther occurrences, a sy s t em of pe riodic blowdown as well as blowdowns prior to testing was impleme nt ed.
No moi s tur e rel a t ed s t art f ailures h ave occur red which result ed in LE R' s in the seven ye ars since (approximately 1/6 of the expect ed plant life).
In ad di t io n, a more recent study by the Ins t itut e fo r Nuclear Power Ope rations used 450 diesel r ela t ed LE R' s issued since January 1980 to anal y ze failure that only 5% of the more recent f a ilur es we re data.
this study shows due to moisture.
Improved ope ration and maint enance pract ices applied by the industry when the moisture problem firs t became apparent on an indus tr y-wide basis in the late 1970's is undoubt ed ly pa rt of the reason for this impr ovement.
Such pract ices at BVPS-1 have proven to be highly successful.
As described in FSAR 9.5.6, the method of starting the diesels used at involves admission of air directly into the engine's cylinders.
BVPS-2 This eliminates the need for air start moto rs used on some ot he r designs which are, as s tat ed in NUREG/CR 0660, more susc ep t ib le to moisture rela t ed damage.
Another impo rt ant des ign fe ature tJt ich.
allows these diesels to be more tolerant of any starting sy s tem f ail-ure is the redundancy of the start sy s t em s.
Each diesel is provided with redundant s tart ing systen compo nent s to enh ance its s t art ing reliability as stated in FS AR 9.5.6.
In accordance with GDC 17, su f ficient inde pe nde nce and red undancy is provided to assure pe rf ormance of safety funct ions as suming a s ing le failure.
Los s of a single dies el generato r is cons ide red in the safety analyses.
As demons trated at BVPS-1, loss of a diesel due to moisture is a rarity when appropriate ope rating and maintenance pr ac-t ices are ap plied.
Coincident los s of both diesels due to moisture would be even less likely and is prev ented in pa rt by the indepe nde nce of the air starting systems.
The use of ope rat ing pr ocedur es simila r to tho se in use at BVPS-1 should provide diesel reliability similar.to that of RVPS-1.
Addi-t ional ly, pe riodic tes t ing will confirm the availahility of the diesels.
Thus, it cannot be concluded that ins tallation of the air reques eed by the NRC, would provide subseancial ad di t io nal dryees, as pr ot ect ion wh ich is requi red for the public health and safety.
Ther+
fore, this proposed backfit is not justified unde r 10C FR 50.100 O