ML20215E726

Safety Evaluation Supporting Cancellation of Torus Pool Temp Indication & Thermal Mixing Mods

ML20215E726
Person / Time
Site:	Oyster Creek
Issue date:	10/01/1986
From:	Office of Nuclear Reactor Regulation
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ML20215E725	List: ML20215E722 ML20215E726
References
NUDOCS 8610150475
Download: ML20215E726 (5)

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UNITED STATES 8 o NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 r,; y

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO TORUS P0OL TEMPERATURE INDICATION AND THERMAL M:XINr. MODIFICATIONS GPU NUCLEAR CORPORATION JERSEY CENTRAL POWER AND LIGHT COMPANY OYSTER CREEK NUCLEAR GENERATING STATION DOCKET NO. 50-219

1.0 INTRODUCTION

By letter dated October 31, 1985, and supplemented by letters dated June 16, July 22 and August 4, 1986, GPU Nuclear (the licenseel proposed to cancel two modifications to provide (1) local suppression (torus) pool temperature monitoring at the electromatic relief valve quenchers, or discharge headers, in the pool and (2) thermal mixing for pool near the quenchers. The licensee considers these modifications are part of the scope of work required by the 13, 1981 Order and December Confirmatory Order, " Modification19, nf 1982.

the JanuaryThis Order is related to the Mark I 29, 1981 Order",

Containment dated' Lono Term Program January (LTP) and would require the licensee to complete these modifications before the restart from the Cycle 11 Refueling (Cycle 11R) outage. This outage commenced in April 1986 and is scheduled to end in October 1986.

2.0 BACKGROUND

The primary containment for Oyster Creek is the drywell and the torus.

This is discussed in Section 6.2 of the Oyster Creek Updated Final Safety Analysis Peport (FSAR) dated December 1984 The function of this containment is to accommodate, with a minimum of leakage, the pressures and temperatures resulting from the break of any orocess piping in the containment including reactor coolant system piping.

In its letter dateo October 31, 1985, the licensee statedreport, that the BWR

" Elimination Owner's Group (BWROG) General Electric (GE) NE00-30832 of Limit on BWR Suporession Pool Temperature on SRV (Safety Relief Valve)

Discharge with Quenchers" dated December 1984, concluded that unstable steam condensation is not a concern where quencher devices are used on SRV discharge piping. The licensee stated that quenchers have been installed The at Oyster Creek and the NEDO-30832 report is applicable to Oyster Creek.

above two modifications were for the operators to be able to monitor the local

' pool temperatures in the vicinity of the quenchers and provide additional themal mixing at the quenchers to prevent the onset of unstable steam condensation at the quenchers during SRV discharges to the torus and the resulting dynamic load

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The NED0-30832 and possible damaqe to the SRV discharge piping and torus.

report concludes that significant unstable steam condensation and dynamic loads will not occur with quenchers.

The staff has not started its detailed review of the NED0-3083? report.

3.0 EVALUATION The licensee reouested to cancel two mndifications for suppression pool thermal mixino based on BWROG's NED0-30832.

20, 1986, Progress Review Meeting The licensee explained in the Februarythat the two modifications are (1) adding (summary dated March 14,1986) temperature monitoring in the vicinity of the two Electromatic Relief Valves (EMRV) discharge headers in the torus and (P.) rercuting a containment spray dynamic test return line. They are part of the torus attached piping modifications in the licensee's letter dated June 29, 1981. The purpose of the modifications is the following:

(1) To give the control room operators indications that the temperature of the water in the vicinity of the EMRV headers is reaching the point where unstable condensation would occur and result in dynamic loads on the suppression pool shell during blowdown from a stuck coen EMRV. This would read out in the control room.

(2) The operators would know, by the local pool water In Germany, temperature, a stuck open EMRV that they had a stuck open EMRV.

with a straight open header resulted in unstable condensation of Tnere was steam 'n the pool and localized dynamic The loading.

work by General rocking of the torus and local damage.showed that unstable steam condensatio Electric in NE00-3083?

not a concern when quencher devices are used on EMRV discharge pipina as exists at Oyster Creek.

(3) The test line is used for testing the operability of Containment Spray, Presently it is routed into a torus /drywell vacuum breaker The rerouting was to and drains into the torus suppression pool.

allow means to cause some recirculation in the pool to aid in thermal mixing in the vicinity of the EPRV discharoe headers and lower local pool temperatures. There was no safety problem The new with the test line in its present design and location.

design would be used, in coniunction with the temperature monitoring and knowledge with the operators that they were at the temperature for the onset of unstable condensation, to (1) cause better thermal mixing in the vicinity of the headers and (?)

prevent unstable condensation conditions.

The temperature monitoring in itself would not prevent any unstable conditions and there are other safety grade and redundant indications to These indications are in th TS and identify when an EMRV is stuck open.There is clso torus bulk water temperature read out in the control room. The operators have Emergency Operatino indication in the control room.

Procedures (E0P) addressing a stuck open EMRV. This was verified and 21, 1986, in a tour of the discussed briefly with the operators on FebruaryThe location for and size of the control room by the NRC Pro,iect Manager.

rerouted test line does not indicate it would be effective in causing torus pool circulation in the vicinity of the headers.

These modifications were to prevent unstable steam condensation from EMRV discharges into the pool by (1) temperature monitoring to see onset of temperatures which will cause unstable steam condensation at the header and (2) discharges from the rerouted test line to causing As showncirculation of the in Figure T-1 in pool and reduced temperatures at the header.

NEDO-30837, a straight pipe discharge into the pool will cause large dynamic loads which resonate or peak with respect to the pool water tercerature.

The Figure 3-2 in NE00-3083F shows that for discharoes through quenchers, which is the situation at Oyster Creek, the dynamic loads are significantly reduced.

The above modifications are not part of the licensee's modification to monitor the torus bulk water temperature in accordance with NUREG-0661.

The latter modification for torus bulk water temperature is part of the staff's Long-tern Mark 1 Containment Review and Confirmatory Order dated January 19, 1982. The licensee reauested in its letter dated July 26, 1985, to defer this latter modification (Item 6 of its letter) from the Cycle 11R outace to Cycle 12P outaoe. This decision will be the sub.iect of a separate letter to the licensee on its July 26, 1985, request.

4.0

SUMMARY

Based on the above, the staff concludes that the two modifications presented above are of insufficient safety significance In to fact, warrant the having thereviewed steff has licensee ite de the modifications in the Cycle 11R outage.

Safety Evaluation (SE), " Mark I Containment long Term Program - Pool Dynamic Loads" dated January 13, 1984 and the January 19, 1982 Confirmatory Order and concludes that the modifications are not part of the Mark I Containment modifications required to be completed in the Cycle 11R outage.

The Mark I Containnent Confirmatory Order requires only plant modifications needed to comply with the Acceptance Criteria in Appendix TheA applicable of NUREG-0661, Mark I Containment long-term Program, dated July 1980.

Acceptance Criteria for these torus modifications is the local suppression pool temperature limit for safety relief valve discharge loads in SectionB 2.13.8, page A 41, of Appendix A.

to bulk suppression pool temperature is 43*F (i.e., the Monticello test withnut the residual heat removal system on page 125 of NUREG-0661) and the maximum allowed bulk temperature is 95*F (i.e., Technical Specification 3.5 A.1.7 for reactor operation as explained in the licensee's letter dated August 4, 1986), the maximum local temperature is less than the 200"F Acceptance Criteria

_4-in Appendix A, page A 41. It is also less than the 160 F criteria in the Bases of Section 3.5, Containment, of the Technical Specifications, for relief valve operation with sonic conditions at the discharge exit to avoid the regime ofThe potentially high suppression chamber loading.that these torus modificat Acceptance Criteria of NUREG-0661 and, therefore, are not part of the modifica-tions reauired by Confirmatory Order dated January 19, 1982.

In the meeting of April 10, 1986, the staff presented a Request for Additional Information (RAI) to the licensee on this sub,iect. The RAI had ouestions on (1) the applicability of the request to cancel these torus modifications to the Acceptance Criteria in NUREG-0661, Mark 1 Containment Long-Term Program, dated July 1980 and (2) the relationship between the initial suopression pool temperature for the design bases Loss-of-Coolant Accident (LOCA) analysis and the pool temperature limits in the Oyster Creek Technical Specifications (TSl. The RAI were sent to the licensee in the staff's letter of May 5, 1986.

The licensee responded to the staff's PAI in its letters dated June 16, In these responses, the licensee stated July 22 and August 4, 1986.that without thest tool modifications the local pool exceed the limits dictated by the Acceptance Criteria of NUREG-0661 during the most severe relief valve transients of interest and that the initial suppression pool temperature is consistent with the tempe core spray system pump which draws suction on the suppression pool during the LOCA. The resolution of the staff's concerns on the initial suppression cool temperature was addressed in the staff's letter to the licensee dated

5.0 CONCLUSION

Based on the above, the staff concludes that these modifications are not required as part of the Mark I Long-term Program Confirmatory Order to Therefore, these address safety relief valve discharge loads on the torus.

torus modifications are not required for the safe operation of Oyster Creek and the staff concludes The staff is,that the licensee therefore, does with in agreement not have to do the the licensee on modifications.

cancelling its comitment to install these modifications.

6.0 REFERENCES

1. Letter from P.R. Fiedler (GPUN) to John A. Zwolinski (NRC) with attachment, dated October 31, 1985,

2. Letter froa Dennis M. Crutchfield (NRC) to P.B. Fiedler (GPUN) with attachment, dated January 13, 1984.

3. Letter from Dennis M. Crutchfield to I. R. Finfrock, Jr. (GPUN) with attachment, dated January 19, 1982.

A. General Electric, NED0-30832, Elimination of limit on PWR Suppression Pool Temperature on SRV Discharae with Quenchers," dated December 1984.

5. February 20, 1986, Proaress Review Meetino on Licensina Actions, summary dated March la, 1986.

6. Letter from J. Zwolinski (NRC) to P.R. Fiedler (GPUN), Meetino of April 10, 1986, on Requested Cancellation of Nitrocen Purce/ Vent System, May 5, 1986.

7. Letter from R.F. Wilson (GPUN) to John A. Zwolinski (NRC), Combustible Gas Control and Supnression Pool Te-oerature Linits, dated June 16, 1986

8. Letter frem R.F. Wilson (GPUN) to John A. Zwolinski (NRC), Peouest for Additional Information Concernino Safety Relief Valve Discharges to the Suppression Pool, dated July 22, 1986.

9. Letter from R.i. Wilson (GPUNI to John A. Zwolinski (NRC), Core Spray NPSH Calculations, dated August 4, 1986.

Principal Contributor: J. Donohew Dated: October 1, 1986.

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