ML19320C238

Forwards Response to NRC 800507 Ltr Re Addl TMI-2 Requirements Per NUREG-0660.Generally Agrees W/Ge 800221 Generic BWR Responses.Questions 3 & 7 Cannot Be Answered Due to Insufficient Supporting Documentation

ML19320C238
Person / Time
Site:	Oyster Creek
Issue date:	07/08/1980
From:	Finfrock I JERSEY CENTRAL POWER & LIGHT CO.
To:	Eisenhut D Office of Nuclear Reactor Regulation
References
RTR-NUREG-0660, RTR-NUREG-660 NUDOCS 8007160500
Download: ML19320C238 (5)

Text

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Jersey Central Power & Light Company Mad; son Avenue at Punchtowl Road Morr:stown New Jersey 07960 201 539-6111 July 8, 1980 Mr. Darrell G. Eisenhut United States Nuclear Regulatory Commission Washington, D. C. 20555

SUBJECT:

Additional TMI-2 Related Requirements (NUREG 0660. II K.3.46) g Oyster Creek Nuclear Generating Station Docket No. 50-2 L

Reference:

(a) D. G. Eisenhut's (NRC) letter of May 7,1980 to all operating reactors (b) General Electric's (R. H. Buchholz) letter of February 21, 1980 to D. F. Ross, USNRC Reference (a) requested that each operating boiling water reactor assess the applicability and adequacy of General Electric's response (reference (b)) to a general list of concerns expressed by a consultant to the ACRS.

Enclosure i provides the results of the assessment as applied to Oyster Creek, a BWR-2 design.

In general we agree with General Electric's generic BWR responses. In the cases of questions 3 and.7 however, we do not have sufficient supporting documentation at this time to conclude that the concern is not a problem for Oyster Creek. We are currently investigating these concerns and will respond t; the NRC in the near future.

Very truly yours, 4291 Ivan R. Finf ek, .

Vice President-Generation IRF:E0C:dh

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t Jersey Central Power & L,gnt Company S 3 Mem0er Ct the Genera! Puccc uet es Sys:em 8007160 g

Paga 1 of 4 h.NCICSURE 1 JULY 8, 1980 OYSTER CREEK NUCIEAR GENERATING STATICN RESPONSE 'IO QUESTICtB PCSED BY C. MICHEIoON, AN ACBS CONSULTANT (NUREG 0660, II K.3.46)

1. QUESTIchi Pressurizer level is an incorrect measure of primary coolant inventory.

RESPOSE A BWR does not have a pressurizer. Primary coolant inventory is measured directly ~ sing differential pressure level sensors attacned to tne reactor vessel. 'r , tnis concern does not apply to Oyster Creek.

2. QUESTIQi The isolation of small breaks (e.g., letdown line; PORV) not addressed .or analyzed.

RESPOSE Automatic isolation only occurs for breaks outside the containment.

Sucn creaks are addressed in Section 3.1.1.1.2 of NEDO-24708. At Oyster Creek ,

tne operator must manually depressurize to allow the low pressure systems to inject and maintain vessel water level (Section 3.5.2.1, NEID 24708). Analyses subnitted for demonstration of adequate core cooling snow tnat tne operator nas sufficient information and time to perform these manual actions. The necessary manual actions have been included in the operator guidelines for =11all break accidents.

3. QUESTIChi Pressure boundary damage dua to loadings from 1) bubble collapsein subcoolec liquid and, 2) injection of EC water in steam-filled pipes.

RESPGISE The IER has no geometry equivalent to enat identified in Michelson's report on B&W reactors relative to bubble collapse (steam bubbling upward through the pressurizer surge line ard pressurizer). Thus tne first concern is not applicable to Oyster Creek.

- The injection of ECC water into tne core spray sparger and supply piping which could potentially contain steam is not felt to be a problem. However since tnis condition was not considered in tne original design of the system we intend to investigate this matter further. '

4. QUESTIQi In determining need for steam generators to remove decay heat  ;

constoer that break flow enthalpy is not core exit entnalpy.  !

l RESPOSE BWRS do not use steam generators to remove decay heat, so this concern does not apply to Cyster Creek. The 2 modelling of break flow is discussed in NEIO-20566.

5. QUESTIChi Are sources of auxiliary feedwater adequate in the event of a delay in cooldown subsequent to a small IDCA?

RESPONSE BWRs do not need feedwater to remcVe heat from the reactor following a LOCA, wnetner the subsquent cooldown is delayed or not. Therefore this concern is not applicable to Oyster Creek. ShRs have a closed cooling system in whit 1

- vessel water flows out tne postulated break to tne suppression pool. Te

Pcga 2 of 4 suppressfon pool is cooled and water is pumped back to tne vessel with ECCS pumps.

6. QtESTIai Is the recirculation mode of operation of the HPCI pumps at high pressure an established design requirement?

IES10lSE Oyster Creek, a ER 2, is not equipped with a HEI system, tnerefore tnis concern does not apply.

7. QUESTIOi Are the HEI pumps and RHR pumps run simultaneously? Do tney share common piping / suction? If so, is the system properly designed to accomodate this mode of operation (i.e., are any NPSH requirements violated, etc....?)

RESPOESE At Cyster Creek the containment spray (CS) and Iow pressure core spray (LPCS) pumps take suction through a common header frcm the suppression pool.

Altnough we feel that the suction header has been properly sized, we have been unable to locate the original design calculations. We are in the process of redoing tne analysis and will report tre results at a later date.

8. QUESTION Mechanical effects of slug flow on steam generator tuces needs to be addressed (transitionig frcm solid natural circulation to reflux boilirg and bacx to solid natural circulation may cause slug flow in tne not leg pipes.)

RESPOISE SWBS do not have steam generators so ?.his concern does not apply to Gyster Creek. NR post-ICCA cooling modes are tddressed in NEDO-24708.

9. QUESTION Is there minimum flow protection for the HPCI pumps during the reciculation mode of operation?

RESPOSE Oyster Creek does not have a high pressure injection system. The low pressure core spray system does have minimum flow protections wnile the pumps are running prior to injecting water into the core.

10. QUESTION The effect of tne accumulators dumping during small break ICCAs is l not taKen into account.

RESPONSE BWRs do not use accumulators to mitigate LCCAs. Therefore this l concern does not apply to Oyster Creek  !

11. QUESTIOi What is tne 1:: pact of cont.inued running of tne RC pu:rps during a small IOCA?

RESPQdSE The 1: pact of continued running of the recirculation pumps has been addressed in Sections 3.3.2.2, 3.3.2.3, and Section 3.5 .2.1.5 .1 of NEEO-24708.

The conclusions were tnat continued running of the recirculation pumps results in little enange in the time available for operator actions and does not signLicantly enange tne overall system response.

12. qtmsrIOi During a small break LCCA in which offsite pcwer is lost, tne possibility ard impact of pump seal damage ard leakage has not been evaluated or analyzed.

RESPO4SE 1he containment spray and low pressure core spray pumps are provided

Paga 3 of 4 with mecnanical seals. These seals are cooled by tne pump primary process wa ter . No external cooling from auxiliary support systems, such as service water or room air coolers, is required for pump seals. These types of seals have demonstrated (in nuclear and otner applications) their capability to operate for extended periods of time at temperatures in excess of those expected following a IDCA.

Should seal failure occur it can be det"cted by room sump high level alarms.

Individual containment spray & low pressure core spray pumps are arranged, and motor operated valves provided, so tnat a pump with a failed seal can be shutdown and isolated without affecting the proper operation of tne other redundant pumps / systems.

Considering tne low probability of seal failure during a IDCA, the fact that a pump with a failed seal can be isolated witnout affecting otner redundance equipment, and the substantial redundancy provided in the BWR emergency cooling systems, pump seal faiure is not considered a significant concern for Oyster Creek.

13. QUESTIN During transitioning from solid natural circulation to reflux boiling and back again, the vessel level will be un4nown to the operators, and emergency procedures and operator training may be inadequate. This needs to be addressed and evaluated.

RESPO SE There is no similar transition in tne BWR case. In addition, the BWR nas water level measurement within the vessel and the indication of the water level is incorporated into tne operator guidelines. Consequently this concern does not apply to Oyster Creek.

14. QUESTIN The effect of non-condensible gas accumulation in tne steam generators and its possible disruption of decay heat removal by natural circulation needs to be addressed.

RESR:NSE The effect of non-condensible gas accumulation is addressed in Section 3.3.1.8.2 of NEDO-24708. For a NR, vapor is present in the core during both normal operation and natural circulation conditions. Non-condensibles may cnange tne composition of the vapor but would have an insignificant effect on the natural or forced circulation itself, since tne non-condensicles would rise with the steam to the top of the vessel af ter leaving tne steam separators.

An accumulation of non-condensible gas in the isolation condenser tubes can be vented if a degradation of heat transfer is detected by tne operator. At present the vents are routed to tne main steam lines outside containment. In addition a modification is in progress whicn would permit tne isolation condensers to be vented to tne suppression pool.

15. QUESTIN Delayed cooldown following a small break LOCA could raise the containment pressure and activate the containment spray system. Impact and consequences need addressing.

RESPONSE Oyster Creek has been designed witn an automatically initiated containment spray system. Althougn some non-essential equipment in the drywell (e.g. recirculation pump motors) could be adversely affected by sprays all essential equipment has been qualified for the effects of containment sprays.

Paga 4 of 4

'Similarly tnere is no equi;; ment in tne suppression pools wnica would be affected by sprays.

16. QUESTEE This concern relates to tne possibility tnat an operator may be inclinea and perhaps event trained to isolate, where possible, a pipe break IDCA witnout realizing tnat it might be an unsafe action leading to hign pressure, and short-term core bakeout. For example, if a IER should experience a IOCA from a pressure boundary failure somewhere between the pump suction and disenarge valve for either reactor recirculation pump, it would be possible for the operator to close these valves following the reactor blowdown to low pressure ard thereby isolate the break, stop the blowdown, ard repressurize the reactor coolant system. Before such isolation should be permitted, it is first necessary to show by an appropriate analysis that the nigh pressure ECCS is adequate to reflood tne uncovered core without assistance from the low pressure ECCS wnich can no longer deliver flow because of the repressurization.

Otherwise, such isolation action snould be explicitly forbidden in tne emergency operatirg instructions.

RES30NSE If Oyster Creek snould experience a LOCA from a pressure boundary rallure smewnere between the recirulation pump suction and disenarge valves, it is possible for the operator to close these valves following the reactor blowdown to low pressure and thereby isolate thegreak. Whether the reactor repressurizes or not depends upon the minimum level to wnich the water level drops. If level gets below the low-low set point (7.2 ft. above the core), the isolation condensers will go into operation and tnereby prevent pressure from increasing. If level does not go below tne low .cw setpoint, reactor vessel pressure would increase to the 1050 psi setpoint of two electromatic relief valves which would cycle the pressure between 1050 psi and 1000 psi. Eventually this would cause level to drop below the low-les setpoint of the isolation condensers which would then reduce pressure wi3 no loss of vessel inventory.

Ultimately pressure would decrease to the point wnereby the low pressure core spray system could inject water into the reactor vessel.

This discussion does not tske into consideration the availability of the feedwater or CRD systems which are nigh pressure but non-ECCS systerrs. It also does not censider manual operator actions, eg, initiation of isolation condensers or manual ADS either of which would improve the plant's response.

'Ihis concern is enerefore not a proolem for Oyster Creek.

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