ML19262C432

Forwards Response to NRC 791003 Generic Request for Info Re Auxiliary Feedwater Flow Requirements.Info Pertains to Design Bases for Auxiliary Feedwater Sys

ML19262C432
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	02/05/1980
From:	Goodwin C PORTLAND GENERAL ELECTRIC CO.
To:	Eisenhut D Office of Nuclear Reactor Regulation
References
NUDOCS 8002120461
Download: ML19262C432 (7)

Text

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February 5, 1980 Trojan Nuclear Plant Docket 50-344 License NPF-1 Mr. Darrell G. Eisenhut Acting Director Division of Operating Reactors Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission j9k7 2b Washington, D. C.

20555

Dear Mr. Eisenhut:

of your letter of October 3, 1979 contained a generic request for additional information regarding Auxiliary Feedwater System flow requirements. Attached is our response to this request as it pertains to the design bases for the Trojan Nuclear Plant Auxiliary Feedwater System.

Sincerely, s

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L c.. w s o %

C. Goodwin, Jr.

Assistant Vice President Thermal Plant Operation and Maintenance CG/DIH/CJP/4mg6A14 Attachment b

b c:

Lynn Frank, Director State of Oregon hg Department of Energy I

Q 8002120 NCl

ATTAC10!ENT Response to NRC Request for Information on the Basis for Auxiliary Feedwater Flow Requirements for the Trojan Nuclear Plant 1947 282

We require that you provide the following AFWS flow design basis informa-tion as applicable to the design basis transients and accident conditi>ns for your plant.

Question 1 a.

Identify the plant transient and accident conditions con-sidered in establishing Auxiliary Feedwater System flow requirements, including the following events:

1) Less of Main Feed (LMFW)

2) LMFW w/ loss of offsite ac power

3) LMFW w/ loss of onsite and offsite ac power

4) Plant cooldown

5) Turbine trip with and without bypass

6) Main steam isolation valve closure

7) Main feed line break

8) Main steam line break

9) Small break LOCA

10) Other transient or accident conditions not listed above Describe the plant protection acceptance criteria and cor-v.

responding technical bases used for each initiating event identified above. The acceptance criteria should address plant limits such as:

- Maximum RCS pressure (PORV or safety valve actuation)

- Fuel temperature or damage limits (DNB, PCT, maximum fuel central temperature)

- RCS cooling rate lir.it to avoid excessive coolant shrinkage

- Minimum steam generator level to assure sufficient steam generator heat transfer surface to remove decay heat and/ or cool down the primary system

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Response

a.

The design bases for the Trojan Auxiliary Feedwater System (A7S) flow rate are summarized in Section 6.6 of the Trojan FSAR.

Included in this section is a discussion of the use of the AFS during normal Plant cooldown.

In addition, certain of the transient analyses documented in Chapter 15

of the FSAR assumed operation of the AFS, as shown in Table I.

b.

The Plant protection acceptance criteria with respect to AFS performance are shown in Table i for each event in which the FSAR analysis assumed AFS operation. The Plant limits applicable to each of these criteria are also indicated.

Question 2 Describe the analyses and assumptions and corresponding technical justi-fication used with plant condition considered in 1.a above including:

Maximum reactor power (including instrument error allowance) a.

at the time of the initiating transient or accident.

b.

Time delay from initiating event to reactor trip.

c.

Plant parameter (s) which initiates AFS flow and time delay between initiating event and introduction of AFS flow into steam generator (s).

d.

Minimum steam generator water level when initiating event occurs.

e.

Initial steam generator water inventory and depletion rate before and after AFS flow commences - identify reactor decay heat rate used.

f.

Maximum pressure at wtich steam is released from steam gen-erator(s) and against vhich the AFS pump must develop sufficient head.

g.

Minimum number of steam generators that must receive AFS flow; e.g.,

1 out of 27, 2 out of 4?

1947 284 h.

RC flow condition - continued operation of RC pumps or natural circulation.

i. Maximum AFS inlet temperature.

j. Following a postulated steam or feed line break, time delay assumed to isolate break and direct AFS flow to intact steam generator (s).

AFS pump flow capacity allowance to acccamo-date the time delay and maintain minimum steam generator water level. Also identify credit taken for primary system heat removal.

k.

Volume and maximum temperature of water in main feed lines between steam generator (s) and AFS connection to main feed line.

1.

Operating condition of steam generator normal blowdown fol-lowing initiating event.

m.

Primary and secondary system water and metal sensible heat used for cooldown and AFS flow sizing.

n.

Time at hot standby and time to cooldown RCS to RHR system cut in temperature to size AFS water source inventory.

Response

Details of the the analyses described above are provided in the FSAR sec-tions indicated in Table I.

Specific assumptions for the three transient events described above are summarized in Table II.

The minimun AFS water source inventory (196,000 gal.) is based on main-taining the RCS at hot standby conditions fcr two hours, and then cooling it from 550*F to 350*F in 4 hr.

Question 3 Verify that the AFS pumps in your plant will supply the necessary flow to the steam generator (s) as determined by Items 1 and 2 above considering a single failure.

Identify the margin in sizing the pump flow to allow for pump recirculation flow, seal leakage and pump wear.

Response

The basic Trojan AFS performance requirement is that the system must be capable of delivering a total of 440 gpm into two of the four steam gener-ators within 60 sec. of the loss of the normal feedwater supply. To meet this requirement, the Trojan AFS is provided with two auxiliary feedwater pumps, each capable of supplying 880 gpm to four steam generators. Each pump is rated for 960 gpm, to allow an 80 gpm margin for recirculation flow, seal leakage and pump wear. The pumps are rated for a total dynamic head of 3400 ft. based on the most severe condition of pumping 880 gpm of water into the steam generators when main steam safety valves are dis-charging to the atmosphere at the maximum set pressure.

One of the full capacity AFS pumps is steam turbine-driven while the other is diesel engine-driven. This design provides the redundancy and diver-sity necessary to meet the performance objectives assuming a single failure of either pump or its associated components. An evaluation of specific single failure modes of the AFS was performed in the course of the system design and the results are summarized in FSAR Table 6.6-3.

[947 285 CJP/4mg6A16

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table I FLANT LVtNTS DuklNG WillCH AUXILIARY FttbWATLR SYSTDI (AFS) OFtkATION ASSUtttb Event Acceptance Criteria With Nespect to AFS Perf ormance Applicable Plant Limits 1.

PLin Fetdline kupture a.

No overpressurization of RCS.

a.

kcquised rellet rates are within rellet (FSAR 15.4.2.2) capacity of pressurizer saf ety valves.

b.

No core uncovery.

b.

RCS 11guld volume remains eure than adequate to fill kCS to the top of the reactor core.

c.

Sufficient AFS flow rate f or decay heat c.

Assumed AFS flow rate in capable of removal.

removing decay heat atter 2!00 sec.

2.

Loss of Hain Feedwater a.

kemove stored and decay heat to prevent 4.

kequired rellet rates are within relier with Concurrent Loss of overpressurization of reactor coulant capacity of pressurizer FOKVs.

Offsite Power system.

(FSAR 15.2.8) b.

kemove stored and decay heat to prevent lose b.

Pressurizer does not bec ome wa t e r of water from the reactor core.

solid.

c.

Sufficient flow rate such that the water c.

Water level in steam generators levels in the steam generators being f ed do receiving auxiliary icedwater du not not recede below the lowest levels at which recede beluw the tube sheets.

sufficient heat transter area is available to dissipate core residual hsat without water relief f rom the reactor coolant system relief or safety valves.

3.

Station Blackout Same as for Event 2.

Same as for Event 2.

(FSAR 15.2.9; 0.6.1) 4.

Normal Plant Cooldown Supply feedwater during Plant couldown to Not applicable.

(FSAF 6.6.2.3.3) temperature at which residual heat removal system is used for further cooldown.

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TABLE II SPECIFIC ASSUMPTIONS REGARDING AUXILIARY FEEDWATER SYSTEM (AFS)

IN TROJAN TRANSIENT ANALYSES Trans'ent Event Loss of Main Main Feedline Assumption Feedwater Rupture Station Blackout Initial reactor 3649 MWt 3649 MWt 3491 MWt power (102% ESF Power)

(102% ESF Power)

(102% Rated Power)

Time delay to 2 sec.

20.5 sec.

2 sec.

reactor trip Parameter Low-low steam Not specified Low-low steam initiating AFS generator level generator level flow Time delay for 1 min.

10 min.

1 min.

AFS flow into steam generators Minimum level in At lower narrow steam generators range level tap waen event occurs Reactor decay heat FSAR FSAR FSAR rate used Section 15.1.8 Section 15.1.8 Section 15.1.8 Maximum steam 1240 psig generator (Highest safety secondary side valve setpoint) pressure Minimum number 2 out of 4 2 out of 4 2 out of 4 of steam gener-ators that must receive AFS flow RCS flow Natural circu-Natural circu-Natural circulation condition lation lation Time avail-NA 10 min.

NA able to iso'

'e feedline bri.

}hkf 2b7 and direct AFS flow to unaf-fected steam generators CJP/4mg6A18