ML17187A868
| ML17187A868 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/21/1997 |
| From: | Stang J NRC (Affiliation Not Assigned) |
| To: | Johnson I COMMONWEALTH EDISON CO. |
| References | |
| TAC-M97983, TAC-M97984, NUDOCS 9703250140 | |
| Download: ML17187A868 (4) | |
Text
March 21, 1997 Ms. Irene*Johnson, Acting Manager Nuclear Regulatory Services Commonwealth Edison Company Executive Towers West 111 1400 Opus Place, Suite 500 Downers Grove, IL 60515
SUBJECT:
- REQUEST FOR -ADDITIONAL. INFORMATION (TAC Nos.. *: M979.83 ~ND M97984)
Dear Ms. Johnson:
By letter dated February 17,: 1997, *a~ suppl.~mented February*27, 1997, and March 12, 1997, Commohwealth tdfson Company,(ComEd) req~ested that the NRC r*eview and. approve an application for an amendment_.r~.l.ating to a Technical Specification (TS) change and an Unreviewed'Safety Question (USQ).
The TS change and the USQ involved the resolution of issues related to providing adequate net positive suction head (NPSH) for the Emergency Core Cooling Syste~ (ECCS)* pumps at the Dresden Statton.
The staff has reviewed the license amendment and supporting documentatiori and discovered additional information must be provided to allow the NRC staff to complete its review.
To expedite the NRC staff review, ComEd should provide the responses to the enclosed request for additional information (RAI) as soon as possible. The.
staff provided ComEd the content of the RAis during a phone conyersation on March 18, 1997.
The enclosed RAI provides a written record of the information requested.during the phone conversation.
. If you have any questions concerning the RAI or other issljes related to the license 'mendment, please contact ~eat (301) 415~1345.
Sincerely, Origihal si~ned by!
\\John F. Stang, Senior Project Manager.
-~--"-'-------~-,-----,......_;Project Directorate 111-2 3250140 970321
'.Division of Reactor Projects - III/IV ADOCK 05000237
- o. ff1.* ce of NLic l ear Reactor Regulation P
'.. Docket ~~s-~-- §Q:-2.3.Z.. a*nd-50-2.49 -
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Enclosure:
RAI cc w/ericl:
See next page DISTRIBUTION:
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I. Johnson Conunonwea 1th. Edi son Company cc:
Michael I. Miller, Esquire Sidley and Austin One First National Plaza Chicago, Illinois* 60603 Site Vice President Dresden Nuclear Power Station 6500 North Dresden Road Morris, Illinois 60450~9765 Station Manager Dresden Nuclear Power Station 6500 North Dresden Road Morris, Illinois 60450-9765
- u.s. Nuclear Regulatory Commission Resident Inspectors Office Dresden Station.
6500 North Dresden Road Merri s,' 111 i np1 s. 60450-9766 Reg~~~al Administrator U.S. NRC, Region III
!01 Warrenville Road Lisle, Illinois 60532-4351
- Illinois Department of Nuclear Safety Office of Nuclear Facility Safety 1035 Outer Park Drive Springfield, Illinois 62704 Chairman Grundy County Board Administration Build.ing 1320 Union Street Morris, *Illinois 60450 Document Control Desk-Licensing Commonwealth Edison Company.
1400 Opus Place, su*ite 400 *
- Downers Grove, Illinois 60515 Dresden Nuclear Power Station Untt Nos. 2 and 3
REQUEST FOR ADDITIONAL INFORMATION RELATED TO THE LICENSE AMENDMENT TO EVALUATE THE USE OF CONTAINMENT OVERPRESSURE TO COMPENSATE FOR A DEFICIT IN NET POSITIVE SUCTION HEAD FOR THE EMERGENCY CORE COOLING PUMPS DRESDEN STATION DOCKET NOS. 50-237.AND 50-249
- 1.
Has the occurrence of a stuck open relief valve discharging to the suppression p6ol been considered from a minimum.pressure perspective?
It may be possible that a relief valve could fail to shut and heat u~
- the suppression pool, but not immediately heat the containment.
If the*
emergency core cooling system (ECCS) pumps would start under such an occurrence, this may b~ the limiting case, from a minimu~ pr~ssure perspective, for net positive ~uction head (NPSH).
. 2.
In your February 17, 1997 submittal, one of the conservatisms listed-in jour containment pressure and suppression pool t~mperature analysis is:
"Feedwater.flow into the vessel is assumed to continue until. a.l l the feedwater which wi 11 increase the peak
- suppression pool temperature is injected into the v~~sel.
In.addition, a conser~ative calculation ~f the energy in the feedwater piping. is added to the RPV/contai~ment
'system.'*'
Please include details on the degree of conservatism, versus best-.
estimate, in the above assumption.* For example, addition of energy in the feedwater piping seems to be best estimate.
How is.cons~rvatism
- incorporated into this modeling?
Generally, discuss more fully the modeling -0f the feedwater addition.
In particular~ discuss.how the.individual hotwells were fuodeled and how their enthalpies were combined, and*whether any pumps that would provide a constant flow into the vessel were assumed to be running.
Again~
demonstrate how the assumption is ~onservative versus best-estimate.
- 3.
For long-term containment response analysis case 2al, a higher low-pressure coolant injection (LPCI) heat exchanger value (77.5 MBtu/hr) than the design value (71.0 MBtu/hr) was used.
71.0 MBtu/hr was also used to determine the peak suppression pool temperatµre.
ENCLOSURE
- Why was a higher heat removal rate assumed f~r the NPSH_analysis (case 2al)? How would the lower value of 71.0- MBtu/hr affect the NPSH available, relative to 77.5 MBtu/hr? Justify the use of the higher heat removal rate for the LPCl ~eat exchanger associated with the NPSH analysis.
- 4.
Per discussi6n betw~en the staff and ComEd, it seems likely that the containment sprays would be turned on and remain on under the loss-of-coolant accident (LOCA) conditions analyzed for NPSH purposes.
Is it possibl~ that the termination criteria for the sprays could be mo.re close:ly tied to t~e overpress.ure requested for the time* the sprays would be on, such that higher pressures would be present in containment and, therefore, more margin in NPSH.available would exist?