ML19093B062

From kanterella
Jump to navigation Jump to search
Request for Lowering Service Water Temperature Limit of 25oF & Maximum Containment Air Partial Pressure Limit of 10.0 Psia Assigned to Surry Due to Unusual Cold Winter & Hot Summer in 1977
ML19093B062
Person / Time
Site: Surry  
Issue date: 12/28/1977
From: Stallings C
Virginia Electric & Power Co (VEPCO)
To: Case E, Reid R
Office of Nuclear Reactor Regulation
References
Download: ML19093B062 (5)
v • d • e


Text

...

VIRGINIA ELECTRIC AND POWER COMPAN RXCHMOND, VIROXN J:A 23261 December 28, 197T

  • Mr. Edson G. Case,.Acting Director Nuclear Reactor.Regulation U.S~ Nuclear Regulatory Commission Washington, D; C.

205'55*

ATTN:

Mr

  • Rob ett W.. Reid, Chief Operating Reactors Branch 4

Dear Mr. Case:

Serial No:. 587, :

  • PO&M/ALH':wbh.

Docket. Nos.: 50..:280,

:so..:2s1, License* Nos. DPR-'32.
  • DPR..;37 *,

Yo:ur-staff has previously reviewed and approved a service water temperature range.of 35°F to :ssoF for the Surry Power Station *. These temperature. limits

.were issued in an Order. for Mo4ification of License dated October -17,* :l97T *.

. The unusually cold winter* and hot *summer*. of. this. year* have* caused* us. to.. become more aware. and. concerned about*. service. water. temperature, conditions at. Surry.

The.service water.temperature at Surry_has been* as low as :37oF iri December this

.year and we believe that a 2°F margin to* the.current approved lower limit i$

insufficient.* Since it. is. possible. for the* James* River to be less than :35°F

. (Freezing point 'v 29e>F) we had.our Architect Engineer conduct LOCTIC *NPSH analyses at :zsoli' for the :recirculation spray and low.head E,iafety injection

.pumps.

The results.of these analyses were satisfactory and are presented in the attachment to this.letter.

Containment int_egrity and deptessurization is not adversely.affected by colder.service water.temperatures.

As is shown in existing.technical specification 3.8, higher* containment air partial pressures up to *about 11. 0 psia can.be. tolerated *at lower service water. temperatures without.. exceeding containment integrity or. depressurization limits*.. during

.LOCA.

The:i;"efore no containment int_egrity or. depressurization. analyses wete conducted~

Instead,.we have assigned a maximum limit of :10.0 psia.to.coritainment air partial pressure for all service water temperatures at Surry.

This provides added conservatism and assurance. that containment int_egrity and depressurization transients. are adequate~.

. We. also reviewed the current approved 10CFR50.:46 ECCS analysis for Surry.

As a.result. the NSSS vendor was asked* to*.perform. sensitivity studies* to*

quantify. the. effect. of *2s°F service water on the ECCS analysis.*. The results

.of.this study.were satisfactory.and*are*presented*in.the.attachment.to.this

.. letter~.

e e

~

VIRGINIA ELECTRIC AND POWER COMPANY TO Mr~ Edson G.

  • Case P_age 2 We therefore.request that a lower service water temperature limit,of
  • 2s°F and a maximum containment air partial pressure limit. of :10. 0. psia. be ass_igned to Surry.

Although.we don't expect. the. service water temperature to

.decrease.below :3s°F before mid January 1978; we would appreciate your prompt atten-tion. to this request~*

Attachment

. cc:

Mr. J. P. 0 '. Reilly Very truly yours,

~

}l2r;. 01~~7°/

C. M. Stallings Vice President~ Power Supply and Production Operations

e LOCTIC NPSH ANALYSIS ANALYSES FOR 25°F SERVICE WATER LOWER LIMIT FOR SURRY POWER STAT+ON e

Attachment The lower extreme of the service water temperature operating limit can be reduced from 35 to 25F.

This small reduction has a negligible impact on the NPSHA to the recirculation spray and low head safety injection pumps.

The reduction will, however, improve the performance of the containment heat removal systems, resulting in a decreased depressurization time and subatmos-pheric peak pressure.

Table 1 *presents the evaluation input parameters used for the NPSH analysis.

Only the limiting cases were investigated i.e.,

1.

HLDER with NORM & NSMQ ESF for the recirculation spray pumps

2.

PSDER with Min ESF for the LHSI pumps.

Table 2 presents the results of the l\\1PSH analysis.

All NPSH values are referenced to the centerline of the first stage of the pl.llilp impeller.

'i'he flow and the required NPSH for the pumps are as follows:

1.

Inside recirculation spray pumps (IRS) - 10.1 ft. at 3,500 gpm

- 8.3 ft at 3,000 gpm

2.

Outside recirculation spray pumps (ORS) - 5.5 ft at 2,000 gpm

3.

Low head safety injection pump (LHSI) - 17.0 ft at 3,500 gpm-Min. ESF The required NPSH values for the RS pumps are based on the North Anna Recircula-tion Spray Pump Test conducted on August 22, 1977.

The NPSHR to avoid cavi-tation is presented as Fig. 2 of the August 24, 1977 submittal, "Adequacy of Recirculation Spray Pump - NPSH".

The required NPSH for the LHSI pumps is based on the Byron Jackson pump curve corrected to the centerline of the first stage of the pump impeller.

This curve is presented as Fig. 2 of August 29, 1977 submittal, Low Head Safety Injection Pump NPSH".

The results presented in Table 2 demonstrate that the NPSHA to all pumps is equal to or greater than that required.

Containment depressurization calculations were not performed at 25F service water temperature because maximum depressurization time and subatmospheric peak pressure occur at the maximum service water temperature.

i TABLE 1 e e

NPSH Evaluation Input Parameters

1.

Reactor Thermal Power, NWT 2490.

  • . i
2.

Initial pressure, psia

a.

Total 10.94

b.

Air Partial 9.0

3.

Initial Temperature, F

a.

Dry Bulb 120.

b.

Dewpoint 120.

4.

Service Water Temperature, F

25.
5.

RWST

a.

Temperature

45.
b.

Inventory, gals 385000.

c.

Gallons remaining at end of containment spray operation 52000.

d.

Gallons remaining at LHSI S"witchov~r to pump 25000.

6.

Containment free Volume, 106ft32

1. 753
7.

Spray Thermal Effectiveness, %

100.

8.

Condensing lieat Transfer Correlation Tagami

9.

UA BTU/hr ~F per cooler at 3500 gpm 4.19E6 3000 gpm

  • 4.00E6 2000 gpm 3.49E6
10.

Spray Start Time, secs After CIB Signal

a.

Quench-Spray

58.
b.

Inside Recirculation Spray 185.

c.

Outside Recirculation Spray 401.

11, *Type of Modification

12.

Operating Plllllps NORM Containment Spray 2

IRS 2

ORS 2

LHSI 2

HHSI 2

TABLE 2 IRS is 3500 gpm when NPSH >

11 ft and 3000 gpm when NPSH < 11 ft.

ORS orifices at 2000 gpm LHSI recirculation mode is 3500 gpm.

NSMQ MIN 1

1 2

1 2

1 2

1 2

1 LIMITING CASE NPSHA AT 25F SERVICE WATER TEMPERATURE IRS (1)

Cavitation Time Break ESF sec HLDER NORM 2(4.-710.

RLDER NSMQ 340.-820.

PSDER MIN 670.-1780.

ECCS SENSITIVITY STUDY Minimum Nl?SHA (ft)

At Time t (sec)

IRS ft (sec) 8.3 (306.)

8.3 (395.)

NPSHA at Initia-tion of CL** Recircula*

ORS tion - LHSI ft (sec) ft (sec) 7.7 (430.)

Not Limiting 7.6 (440.)

Not Limiting Not Limiting

. Not Limiting 22.1 (3200.)

I The current LOCA-ECCS analysis for Surry uses a service water temperature of 35°F.

The effect of reducing this temperature to 25°F is to increase the rate at which heat is removed from containment by the recirculation spray system.

This will result in a lower peak containment pressure during LOCA.

Our analysis shows that the decrease in peak containment pressure resulting from 25°F service water will be less than 0.5 psia.

Based on the results of pre-vious sensitivity studies conducted by our NSSS vendor, this small change in peak containment pressure results in a peak clad temperature increase of much less than 20°F.

Therefore it is concluded that the current LOCA-ECCS analysis for Surry Unit Nos, 1 and 2 remains valid.

Operation with service water as low as 25°F is acceptable.

Retrieved from "https://kanterella.com/w/index.php?title=ML19093B062&oldid=4933749"