ML19317H413
| ML19317H413 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 05/05/1980 |
| From: | Crouse R TOLEDO EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-80-04, IEB-80-4, NUDOCS 8006050522 | |
| Download: ML19317H413 (4) | |
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ba In h.) Toteco Docket No.
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License No. NPF-3 RCHARo P. CAouSE vc. %.a.ns Serial No.
1-128 uw I4191259-5221 May 5, 1980 Mr. James G. Keppler Regional Director, Region III Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission 799 Roosvelt Road Glen Ellyn, Illinois 60137
Dear Mr. Keppler:
This letter is in response to IE Bulletin No. 80-04, dated February 8, 1980. The response attached addresses the analysis of PWR main steamline break with continued feedwater addition as it relates to the Davis-Besse Nuclear Power Station Unit No. 1.
Very truly yours, fff f
RPC:TJM Attachment l
cc:
l Louis Reyes, NRC Site Inspector bt c/1 I
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THE TOLEDO ED! SON COMPANY EOISON PLAZA 300 MADISON AVENUE TOLEDO. OH!O 43652 8006050 M l
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Review the contai' ment pressure response analysis to deterw.*ne if the potential ir containment overpressure for a main steam line break inside containment included the impact of runout flow from the auxiliary feedwater system and the inpact of other energy-sources, such as continuation of feedwater or condensate flow.
In your review, consider your ability to detect and isolate the damaged steam generator from these sources and the ability of the pumps to remain operable after extended operation at runout flow.
Response
The main steam line break (MSLB) analysis is presented in FSAR Section 15.4.4 and is further discussed in response to FSAR Questions 15.4.1 and 15.4.8.
Following a postulated double ended rupture of.a main steam line inside the containment vessel, low pressure switches located in the main steam line outside containment will actuate the Steam and Feedwater Rupture Control System (SFRCS).
The reactor trips on low reactor coolant system pressure.
SFRCS will trip the turbine-generator, initiate closure of the main steam isolation valves in both main steam lines, initiate main feedwater isolation for both steam generators, and will start the auxiliary feedwater system.
SFRCS will determine which is the affected steam generator.
Operation of SFRCS following a MSLB is discu sed in FSAR Section 7.4.1.3.1.
No auxiliary feedwater will be added to the affected steam generator, as SFRCS will align both auxiliary feedwater pumps to supply water only tn the unaffected steam generator.
Following main steam and main feedwater isolation of the steam generator, the unaffected steam generator will repressurize while the affected steam generator will continue to blow down and will not repressurize. The redundant SFRCS pressure switches on the main steam lines of each steam generator (set of 600 psig) are the means of detecting which is the affected generator.
These pressure switches are interlocked with the valves in the auxiliary feedwater system to prevent the addition of auxiliary feedwater to the affected steam generator. Because the auxiliary feedwater system only supplies water to the unaffected steam generator, there is no runout of the auxiliary fec'dwater pumps and their continued availak*lity is not affected.
During that period of time required to detect MSLB and close the main steam and feedwater valves, main feedwater will continue to flow to both the affected and the unaffected steam generators.
This feedwater addition has been considered in the MSLB analysis and is described in the response to FSAR Question 15.4.8 and is tabulated in FSAR Table 15.4.4.2.
We have reviewed the data used in the analysis and have found that the values used for feedwater addition following the MSLB are conservative.
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I The values used in the analysis exceed the expected feedwater addition that would result from the most adverse response of the non-safety grade portion of the main feedwater system (control valves wide open and main feed pump turbine overspeed) and the most limiting single failure in the safety grade portions of the feedwater isolation system (failure of the main feedwater stop valves to close on the affected steam generator).
Since our review has determined that the existing FSAR analysis for containment overpressure following MSLB conservatively models continued feedwater addition, no further action is required.
2.
Review your analysis of the reactivity increase which results from a main steam line break inside or outside containment. This review should consider the reactor cooldown rate and the potential for the reactor to return to power with the most reactive control rod in the fully withdrawn position.
If your previous analysis did not consider all potential water sources (such as those listed in 1 above) and if the reactivity increase is greater than previous analysis indicated the report of this review should include:
The boundary conditions for the analysis, e.g.,
the end of a.
life shutdown margin, the moderator temperature coefficient, power level and the net effect of the associated steam generator water inventory on the reactor system cooling, etc.,
b.
The most restrictive single active failure in the safety injec-tion system and the effect of that failure on delaying the delivery of high concentration boric acid solition to the reactor coolant system, c.
The effect of extended water supply to the affected steam generator on the core criticality and return to power, d.
The hot channel factors corresponding to the most reactive rod in the fully withdrawn position at the end of life, and the Minimum Departure from Nucleate Boiling Ratio (MDNBR) values for the analyzed transient.
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Response
The analysis for reactivity increase resulting from MSLB is given in FSAR Section 15.4.4 and is further discussed in the Responses to FSAR Questions 15.4.1 and 15.4.8.
As stated in the response to FSAR Question 15.4.1 (Rev. 6, Iteta e),
the rupture of a main steam line between the steam generator and the main steam isolation valve (MSIV) represents the worst condition for accident analysis. Our review of feedwater addition described in the response to Item 1 of this Bulletin has also considered a break outside the containment and upstream of the MSIV. A break in this location will result in slightly
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Since our review has determined that the existing FSAR analysis of reactivity increase following MSLB inside or outtide contain-ment considers all potential water sources, and consarvatively models those sources, no further action is required.
3.
If the potential for containment overpressure exists or the reactor-return-to-power response worsens, provide a proposed corrective action and a schedule for completion of the corrective action.
If the unit is operating, pro-ide a description of any interim action that will be taken until the proposed corrective action is completed.
No Response Required 4.
Within 90 days of the date of this Bulletin, complete the review and evaluation required by this Bulletin and provide a written response describing your reviews and actions taken in response to each item.
Refer to Items 1 through 3 above
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