ML20199F350
| ML20199F350 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 06/17/1986 |
| From: | Brey H PUBLIC SERVICE CO. OF COLORADO |
| To: | Berkow H Office of Nuclear Reactor Regulation |
| References | |
| RTR-REGGD-01.082, RTR-REGGD-1.082 GL-85-22, P-86381, NUDOCS 8606240291 | |
| Download: ML20199F350 (2) | |
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Company of Colorado 2420 W. 26th Ave. Suite 100 D Denver, CO 80211 June 17, 1986 Fort St. Vrain Unit No. 1 P-86381 Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 ATTN: Mr. H.N. Berkow, Director Standardization and Special Projects Directorate Docket No. 50-267
SUBJECT:
Generic Letter 85-22 Loss of Post-LOCA Recirculation Capability Due to Debris Blockage
REFERENCE:
1). NRC letter, Thompson to all Licensees..., dated Dec. 3, 1985 (G-85487)
Dear Mr. Berkow:
Generic Letter 85-22 (Ref. 1) discusses Regulatory Guide 1.82, Rev.
1, " Water Sources for Long Term Recirculation Cooling Following a Loss-of-Cooling Accident".
This concerned debris from a LOCA blocking ECCS sump debris interceptors and sump outlets, resulting in a loss of net positive suction head to the ECCS pumps, below that required for long term cooling recirculation. Since the regulatory analysis did not support a generic backfit action, this regulatory guidance will not be applied to any plant now licensed to operate.
However, the NRC recommended that RG 1.82, Rev. 1 be used as guidance for the conduct of 10 CFR 50.59 reviews dealing with the changeout and/or modification of thermal insulation installed on primary coolant system piping and components.
Applicability The applicability of Regulatory Guide 1.82, Rev. I to Fort St. Vrain (FSV) was investigated.
FSV does not have ECCS sumps or screens similar in purpose to those discussed in this Regulatory Guide.
FSV uses helium as its primary coolant. Heat from the Primary System is removed by water cooled steam generators and liner cooling, without direct interaction of the water and helium. The Feedwater and Condensate Systems supply closed loop cooling to these steam 0(
0 generators.
The Fire Water Systems supply once-through cooling to the steam generators in case of emergencies.
8606240291 860617 PDR ADOCK 05000267 P
P-86381 Junn 17, 1986 Recirculation of the primary coolant within the Prestressed Concrete Reactor Vessel (PCRV) - the equivalent of the LWR containment, is provided by nuclear or auxiliary steam, feedwater, condensate, service water, or fire water driving the helium circulators.
Paths thru the core, core support floor and steam generators direct the helium back into the inlet plenums of the helium circulators.
- Thus, FSV does not recirculate water from its containment floor for use in core cooling or containment pressure suppression as a LWR does following a LOCA.
The Reactor Building sump, beneath the PCRV merely collects any liquid leakage within the Reactor Building which is discharged by the sump pumps to the cooling tower blowdown for disposal.
It is possible that because of a high energy line break (HELB) or rapid primary coolant depressurization accident, Design Basis Accident No. 2 (DBA-2), insulation from the steam pipes located within the Reactor Building, but outside of the PCRV, could break loose and form debris on the Reactor Building floor, which could diminish the capacity of the sump pump to mitigate flooding in the lower level of the Reactor Building. This would not affect core cooling. Studies performed on the potential for flooding in the Reactor Building due to a feedwater line rupture have concluded that due to the large volume of holding capacity available in the Reactor Building sump / keyway, there exists no potential for flooding above elevation 4,739 feet.
Following the current outage, no equipment relied upon for safe shutdown cooling will be located in the Reactor Building sump / keyway below elevation 4,739 feet.
The Reactor Building sump pumps are not relied upon to mitigate the consequences of either of these events (i.e., DBA-2 or HELB), and therefore have not been included in the FSV environmental qualification program.
CONCLUSION This generic letter and Regulatory Guide 1.82, RCV.1 are not applicable to Fort St. Vrain.
No NRC response to this letter is required or requested.
If you have any(questions regarding this letter, please contact Mr. M. H.
Holmes at 303)480-6960.
Very truly yours, hvow k H. L. Brey, Manage Nuclear Licensing and Fuels HLB /JRJ:kb
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