Text

Forwards Response to NRC Re Request for Exemption from 72-h Requirement for Achieving Cold Shutdown Following Fire in Auxiliary Bldg RHR Pit Zone.Cold Shutdown Can Be Achieved & Maintained within 72-h of Plant Shutdown
	ML17256B167
Person / Time
Site:	Ginna
Issue date:	07/28/1982
From:	Maier J; ROCHESTER GAS & ELECTRIC CORP.
To:	Crutchfield D; Office of Nuclear Reactor Regulation
References
	TASK-09-06, TASK-9-6, TASK-RR NUDOCS 8208030363
	Download: ML17256B167 (21)
	v • d • e

REGULATOR NFORMATION DISTRIBUTION,'EM (RIDS)

AOCESSION NBR;82080303b3 DOC ~ DATE: 82/07/28 NOTARI'ZED:NO DOCKET FACIL:50-244 Robert Emmet Ginna Nuclear Plantg Uniit ii Rochester G

05000244 AUTH BYNAME AUTHOR AfFILIATION MAIERgJ ~ E ~

Rochester Gas 8 Electr ic Co> p ~

REC IP, NAME RECIPIENT AFFILIATION GRUTCHF IELD,D, Opera t ing Reac tor s Branch

'.5

SUBJECT:

Forwards nesponse to NRC,820507 ltr re:request forexemption from 72-h irequirement for.achieving cold shutdown following fir e in auxiliary bldg RHR pit zone.Coldishutdown can 'be achieved 8 maintained wiithin 72 h of plant shutdown.

DISTRIBUTION CODE ~

A03SS TITLE: SEP Topi cs NOTiES:NRR/DL/SEP icy'COP IE8 'REC EI VED:L'TR, l EN CL SIZE ~,

05000244 RECIP IENT ID CODE/NAME ORB uS BC 01 INTERVAL: NRR/DE/ADMQE 13 NRR/DL/ORAB 11 I

B REG 04

~COPIES LTTR -ENCL 7

i>7 1

1 1

1 REC I'P IENT ID 'CODE/NAME NRR/DE/HGEB 10 NRR/DL/SEPB 12 NRR/DS I/CSB 07 RGN1 COPIES LTiTR ENCL "2

2

~3 3

1 1

EXTiERNAL: ACRS 14 NRC PDR "02 NOTES:

10 10 1

1 1

1 LPDR NTIS 03'5 1

1 1

1 TOTAL NUMBER OF COPIES REQUIRED:

LiTTR 32 ENCL 32

f n

a ic lf Etl 3

fP

\\

li

B t

/////I///////

/////////////

Lal ~ 0I1>

///I/

/

//tt///////

ROCHESTER GAS AND ELECTRIC CORPORATION 89 EAST AVENUE, ROCHESTER, N.Y. 14649 ttAtE JOHN E. MAIER VKO PfOBlttBAt 7 EI.E P H0 N E AREA COOK 7IO 546-2700 July 28; 1982 Director of Nuclear Reactor Regulation Attention:

Mr. Dennis M. Crutchfield, Chief Operating Reactors Branch No.

5 U.S. Nuclear Regulatory Commission Washington, D.C.

20555

Subject:

Fire Protection Rule 10 CFR 50B48(C)(5)

Alternative Safe Shutdown Section III.G.3 of Appendix R to 10 CFR 50 (SEP Topic IX-6)

==Dear

Dear Mr. Crutchfield:

==

Your letter dated May 7; 1982 requested that we provide additional information for your review of our request for exemption from the 72-hour requirement for achieving cold shutdown following a fire in the Auxiliary Building Residual Heat Removal Pit zone.

Responses to your specific requests are provided in Attachment A

to this letter.

We have determined, however, that our exemption request, which was based on a preliminary evaluation of water solid steam generator heat removal capabilities,'ay no longer be required.

Our current evaluation of this mode of operation indicates that cold shutdown could be achieved in a 72 hour8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months period following plant shutdown.

The basis for this evaluation is given in Attachment A.

We wish to emphasize, as we have in the past, that although the cold shutdown capability using a water solid steam generator method of cooldown may. exist, we are neither committing to use this method, following a postulated fire which disables both residual heat removal trains, nor are we committing to achieve cold shutdown within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months following a fire.

The safest and most prudent method of plant operation will be determined at the discretion of plant management following any emergency, situation.

Very truly yours,

.E. Maier Attachment 8208030363 820728 PDR ADOCK 05000244 F

PDR

~

R R

I

~

l'

~

I' I

C

ATTACHMENT A Information Re uested The additional time needed beyond 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to effect cold shutdown.

2.

3.

Provide the result of thermal analyses for all proposed alternative cooldown methods which quantitatively 'demon-strates the ability to achieve and maintain cold shutdown following the loss of the RHR system.

For the case of solid steam generator operation, the qualifications of the main steam MSIVs, the PORVs and safety relief valves for solid water discharge must be demonstrated to ensure reliable valve operation for both water and steam discharges.

~Res ense Additional analyses have been performed since the request for exemption was submitted in order to better quantify the time to reach cold shutdown using a water solid steam generator method of cooldown.

The only fire requiring this method of operation to reach cold shutdown 'is one occurring in the Auxiliary Building Residual Heat Removal Pit Zone which disables both Residual Heat Removal (RHR) pumps.

Previous studies (References 1 and 2) have shown that the fire loading

.in this zone is very low and transient combustibles are controlled.

The probability of a fire occurring in this zone is low. If a disabling fire does occur in this zone, no equipment or auxiliary equipment required for shutdown, other than the RHR system,- will be affected.

All of the main auxiliary feedwater (AFW) system and the standby auxiliary feedwater (SAFW) system will remain operable.

Using only the 'four motor driven pumps (2

AFW and 2

SAFW),

considerable capability to pump water through the steam generators exists.

Under these circumstances cold shutdown could be reached within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months of plant. shutdown.

2.

Cooldown of the plant following a fire in the RHR pump pit would be accomplished using normal plant shutdown methods and procedures until the primary temperature is reduced to 350'F.

Heat removal would be accomplished by steam dump to the condenser and/or steam relief through the main steam power operated relief valves (PORVs).

Cooldown to 350'an easily be achieved in 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months or less employing a cooldown rate considerably less than the Technical Specification limit of 50'F/hour.

The RHR system would normally be put in service at 350'F to complete the cooldown.

With the RHR system disabled, cooldown is accomplished by the steam generators in three modes of operation;

steaming, addition of cold water to fillthe steam generators, and solid steam

~ 'I Ity" h

.'I N

It I

11 P

C N

F Q$

N IIP F

h 1

It

~

r f g I

I I

y

~

f

~

1' I

ll y IlV Jl 1

V ll h

I Il

I pg p p.

I hy

~

,rra f C.

f ltr, y lf y

~

f

~

N r

~

f Alit V'NP f

4

~ I I

1 V

P I

h>f'IN L KV ~ ~)

)

~.

)

lt,

",$ ~Pf,'LrfÃP~P

~

-.k'P FS

="

wf NP a

'.NVI I~

~

risc.i..

,r It

. ~

k P off 'e Va'1 i

~

r y

II I

v Fl I

I!

V r ",

VN I ~ g I [ It, I II

)

I y

N V'V V

V P

P I

~ V I'

IINP V4

~ I 1

P rh h

~ I

'I caw,,

I*

p y fr F

I N

N V

VN r

~

I

2

';generator operation with water-to-water heat. transfer.

The

,analysis performed to verify that cold shutdown can be achieved in 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months is 'summarized below.

'eneral Method of Anal sis r

The cooldown was calculated in 3 steps:

steaming out the main steam PORVs, filling the steam generators with auxiliary feedwater, and solid steam generator operation with water-water heat transfer.

Energy equations were written and solved for the primary and secondary systems for each.step of the cooldown.

The solution to the energy equation provided a cooldown curve.

Local conditions and heat transfer implied by the cooldown curve were calculated and compared to reasonable heat transfer coefficients calculated by other, means.

The heat transfer implied by the cooldown was reasonable and thus the cooldown curve was shown to be attainable.

The actual evaluation of the cooldown equations used a computer program written for this analysis.

For water solid steam generator operation, the plant was modeled as two interacting natural circulation loops in order to show that the heat transfer required for final cooldown could be achieved with water-water heat transfer.

Another computer program written for this analysis was used for evaluating the last step of the cooldown.

Ma or Assum tions 2.

3.

5.

6.

7.

The primary syst: em decay heat is a function of time based upon 100% of ANS 5.1 decay heat values following infinite operation.

The primary coolant has been cooled to 350'F at 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months following shutdown.

The primary system is at uniform temperature, or at, least the primary water can be modeled as one lumped heat capacity.

Makeup water added to the primary.system is added at the current temperature of the primary water.

The metal in contact, with the primary system water is at the same temperature as the primary water.

The heat capacity of the metal of the steam generator secondary may be neglected compared to the heat capacity of the water in the steam generator secondary (this assumption was verified to be true by analysis).

Steam flow out the main steam PORVs may be modeled as Moody critical flow of saturated steam until the calculated critical flow is larger than frictional flow out the PORV line.

The lower frictional,flow is then used.

~

',~p(b0'K

~ / p., ~ +

$'PKf F

4(

(

Kll tt

~

lf I

F 4

a rt

~ 4 g

P 4(,t e (III~

I 4

4 I

44

~ (

4 4

F lT I

4 4 4 P

~'

4

~ I l

Ir I

4'I I',4 I

~

4 4

p tr 4.rt'%PK"

~ I FII 4

4

/VAN

~,

~ r 4 t(

'g ~

~ Hp e

t I

~

p p,e('K.

I

-I

8.

During steaming out the main steam PORVs, the AFW system is used-only to supply enough water to maintain water level.

Variations in water level of k2 ft. do not affect the cool-down calculation.

9.

No credit is taken for any other forms of plant cooldown which might be available, such as feed and bleed through the chemical and volume control system.

10.

The primary water heat capacity may be considered constant from 350'F to 180'F.

11.

The heat transfer coefficient (UA) of the steam generator is

.approximately constant while steaming out the PORV's from 350 F to 245 F.

12.

A friction factor F = 0.012 is adequate for water flow out the PORVs, vents and drains, and blowdown system, instead of calculating F based on Reynolds number.

13.

Only 3000 out of 3260 tubes in each steam generator are capable of circulating water.

~Summar Calculating the cooldown process in 3 separate

steps, and using equations for energy transfer between components, results in a cooldown curve that requires only moderate heat transfer coefficients.

Steaming out the main steam PORVs can bring the primary temperature down to 260'F within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months after shutdown, and'o 245'F within 60 hours6.944444e-4 days 0.0167 hours 9.920635e-5 weeks 2.283e-5 months .

Filling the SG with cold water 60 hours6.944444e-4 days 0.0167 hours 9.920635e-5 weeks 2.283e-5 months after shutdown can bring the primary temperature down by more than another 60'F in under 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months .

Water-to-water

heat, transfer occurring in solid steam generator operation can maintain the primary temperature below 200'F within 60 hours6.944444e-4 days 0.0167 hours 9.920635e-5 weeks 2.283e-5 months after shutdown by employing natural circulation in the steam generator secondary and reactor coolant systems.

Descri tion of Cooldown Model Ener E

ations Figure 1 shows the general approach to calculating the cooldown using energy transfer between 5 components.

The energy flow through each component is described by a single equation, and cooldown is calculated based on the cooldown rate.

A heat transfer coefficient necessary to support the energy transfer is calculated and compared to typical heat transfer coefficients based on local conditions.

As long as the necessary heat transfer coefficient is less than the typical local heat. transfer coeffi-cient, it is possible to transfer the amount of energy necessary for the cooldown,, and the cooldown calculation based on energy transfer is valid.

The first step in the cooldown proceeds by steaming out the main steam PORVs, with water levels at. the normal steam generator

4

)f P

C l

hl JI p

II f lff erf j

I ak J-

~

P I~

J

" I P 4 f 4

h~

I J

.Jr MI I

k I

~ P(

I' I

I~

I P

M 'M II

~

I a

g, I

-Mac

~

F lf

~'

M J h

~,Ih I~

<<F p'

r

~

I Ptkkf Ii f

Et M

4 I hf

'I II I

(

Fh I

M

FIGURE 1

GINNA COOLDOVTN MODEL GENERAL METHOD FOR STEAMING CONDITIONS p THIS ENERGY RELEASE IS LIMITING ENERGY RELEASE

'PORV 6

BLOWDOWN DETA'ILED MODEL DEVELOPMENT FOR HEAT TRANSFER PRIMARY SYSTEM (HEAT CAPACITY)

HEAT SOURCE (DECAY HEAT)

AUX FW SOURCES FOR SOLID CONDITIONS FLOW SUPPLIED BY AUX FW IS LIMITING

level.

The second step is flooding the steam generators up to the main steam line with water from the AFW system.

The third step in the cooldown involves water-to-water heat. transfer with the steam generator filled water solid.

For the first step, the 5 components are modeled as:

1.

The heat. source is primary system decay heat.

This is modeled as a function of time, based upon 100% of the ANS standard.

2.

The primary system is modeled as one lumped heat capacity, at uniform temperatures.

Heat capacity is the sum of the heat capacity of the primary water plus primary metal mass.

3.

Steam flow out the PORVs is modeled as Moody critical flow of saturated steam out, of a fixed sized orifice.

The steam flow is calculated as a function of pressure.

4.

AFW flow is assumed to be controlled to supply just enough water to match the steam flow out. the PORV, maintaining the steam generator water level..

5.

The steam generator is modeled as one lumped container, with

'steady state mass flow, and energy in-flow from the primary system.

The steam generator is described by one uniform temperature.

Since the heat capacity of the metal of the primary system is small compared to the heat capacity of the primary water, and the primary has more metal in proportion to its volume than the secondary (due to piping, thicker vessel) the heat capacity of the metal of the steam generator is-neglected.,

li For calculating cooldown during the steaming step, it is assumed that the primary and secondary systems cooldown at the same rate.,

That is, the hT between the primary and secondary systems remains const'ant.

The 'hT is calculated using this assumption.

If the bT is sufficiently small, then the assumption of equal cooldown rates for the primary and secondary systems is valid.

The results of the calculations for the system cooldown are shown in Figure 2.

Sixty hours after plant shutdown the primary temperature has been reduced to 245'F by steaming from the main steam PORVs.

Calculatin Cooldown vs. Time for Fillin Steam Generator Initial conditions for this step were chosen arbitrarily at 60 hours6.944444e-4 days 0.0167 hours 9.920635e-5 weeks 2.283e-5 months after shutdown.

This step could be started earlier or later if desired.

The capabilities of the AFW pumps and standby AFW pumps are given in References 3 and 4.

The turbine driven AFW pump is not

p

~

p

~

4>>

r Pf 4

r p

I 4

I fh 1>

4 1

I I,

~

I

~ I

~

r

'I I ~ '

pp<<

II fh 4 fr ~

h

.1I r

V If 44

'4 4'I 4

rr I

~

ghr

)h 4.

<<h

~ fr I.',

I p I

I'

'<< I

">>4

, r <<4pp J 2 y ~'k rff 4

II

.'"fll< b.'P'..""PJ...

t 4

I>I

'PPl.f,

>> '31

)

f I

4

'pp 4

I, )I

'I

'hr I

<

> I 4 -I II I I >> ~ II ) If 360 normal cooldown to 350~ at 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months FIGURE 2 TEMPERATURE VS. TIME <UATER SOLID SG COOLDO[Rl 340 320 300 cooldown by steaming through 2 SG PORVs 280 260 240 220 200 cooldown by completely filling both SG water-solid 180 160 decay heat removal by SG water-to-water heat. exchanger 0 2 4 6 8 10 12 14 16 20 24 28 32 36 40 44 48. 52 56 60 TIME (HR) ~ ~ 5 considered since it is assumed that steam pressure will be too low to power the turbine. Based on steam generator volume and water level, the average temperature of the primary and secondary water after fillingthe steam generator was calculated assuming sufficiently good heat transfer exists between the primary and secondary that they can be described .by one temperature. The time to fillthe steam generator is calculated to be less than 30 minutes. The decay heat generated during this time at 60 hours6.944444e-4 days 0.0167 hours 9.920635e-5 weeks 2.283e-5 months after shutdown will only raise the temperature of the mass of water in the primary and secondary by less than 10'F. Filling both steam generators with 80'F water 60 hours6.944444e-4 days 0.0167 hours 9.920635e-5 weeks 2.283e-5 months after

shutdown, and including the decay heat generated during the fillingtime, will reduce the system temperature from 245'F to approximately 180'F as shown on Figure 2.

Deca Heat Removal With Water Solid Steam Generators Following system temperature reduction below 200'F it remains to be established that decay heat can be removed using the steam generator as a water-to-water heat exchanger. Sixty hours after

shutdown, decay heat. will impart a 100'F temperature rise to 66 lb. of water per second.

This flow rate can be produced by one AFW pump at reduced system pressures. The relief capability was calculated for several combinations of main steam drain lines and pressures. It was determined that a single 2 inch drain on each steam generator could together relieve the required 66 lb./sec. at 100 psia for decay heat removal. This drain size corresponds to the bypass lines, around the.main steam isolation valves (MSIVs). Water released from 'the. steam 'generator could be directed to the condenser or could be directed outside the turbine building. A verification of natural circulation on the steam generator secondary side was also performed for this mode of operation. l Conclusion Cold shutdown can be achieved and maintained within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months of plant shutdown by steaming from the steam generator PORVs, by fillingboth steam generators with 80'F water and by continuing an AFW flow rate of 66 lb/sec through the steam generators after they have been filled. y I 4 hd 4 I ~ LA \\ yp( 4t ( ti 4, 4 IP 4 y 4 I ,tl I k l 14 I a y I A" d') ~ I d. '4 I ~ I ~ 4 ~ ,hatt II e - ~ I H I I Id ( 4 y lt II ti 14 a 44" ". I 4 a d: I, a C eh art ~ ' 0 Ld I 4 ( nl Ihg y e ra ~I LIP I r IA ~ P hy>>y I 4 d<<% d LJ ltd I I d ~ 4<< yyf 6 3. Under the conditions detailed in 2. above neither the MSIVs, ,the PORVs nor the safety and relief valves are required to ,pass'ater 'under'he solid steam generator mode of operation. ti I' k k P k ~ A kr"lL k ~ <<,P V <<4 ~' References 1. L. D. White, Jr. letter to A. Schwencer, USNRC, dated February 24, 1977. 2. John E. Maier letter to Dennis M. Crutchfield, USNRC, dated October 16, 1981. 3. L. D. White, Jr. letter to Dennis M..Crutchfield,

USNRC, dated May 28, 1980.

4. John E. Maier letter-to Dennis M. Crutchfield, USNRC, dated January 8, 1982. . 0 t h, I -I II

ML17256B167

Contents

Text

SUBJECT:

Subject:

Dear Mr. Crutchfield:

Navigation menu

ML17256B167

Text

SUBJECT:

Subject:

Dear Mr. Crutchfield:

Navigation menu

Search