ML20215F301
| ML20215F301 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 06/11/1987 |
| From: | Murphy W VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | Rooney V Office of Nuclear Reactor Regulation |
| References | |
| FVY-87-65, NUDOCS 8706220325 | |
| Download: ML20215F301 (5) | |
Text
e i
VERMONT YANKEE
- NUCLEAR POWER CORPORATION FVY 87-65 RD 5, Box 169. Ferry Road, Brattleboro, VT 05301 y,
[y' ENGINEERING OFFICE
~
1671 WORCESTER ROAD FRAMINGHAM, MASSACHUSETTS 01701 TELEPHONE 617+872 8100 June 11, 1987 U.S. Nuclear Regulatory commission Washington, D.C.
20555 Attn:
Office of Nuclear Reactor Regulation Mr. V.L. Rooney, Senior Project Manager Project Directorate I-3 Division of Reactor Projects'I/II
References:
a)
License No. DPR-28 / Docket No. 50-271) b)
Letter, VYNPC to USNRC, FVY 86-34, " Proposed Technical Specification Change for Spent and New Fuel Storage,"
dated 4/25/86
Dear Sir:
Subject:
Vermont Yankee Proposed Change No. 133, Spent Fuel Pool Expansion - Response to NRC Request for Additional Information Pursuant to recent discussions with NRC staff concerning certain issues associated with our proposed spent fuel pool expansion Technical Specification license amendment submittal [ Reference b)], Vermont Yankee herein provides the supplemental information requested.
NPSH With respect to the Net Positive Suction Head (NPSH) of the spent fuel pool cooling system, the available NPSH (conservatively assuming a pool water level equal to the pool outlet nozzle elevation) is sufficient to prevent pump cavitation and resultant loss of flow. A margin of 20' above required NPSH is calculated assuming 212'F water temperature.
Decay Heat Loads In response to your question concerning the decay heat load for a full core discharge condition which fills the spent fuel pool to its current licensed
-capacity of 2,000 assemblies, Vermont Yankee has calculated a heat load of 17.3 MBtu/hr. This heat load was calculated to be 18.26 MBtu/hr using the same assumptions for a full core discharge condition which fills the pool to the proposed 2,870 assemblies.
The assumptions were consistent with standard review plan assumptions and included the following: the heat load was calculated at ten days following reactor shutdown; a 100% cumulative capacity factor was used and full power operation was assumed at 1,665 MWT.
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VERMONT YANKEE NUCLEAR POWER CORPORATION U.S. Nuclear Regulatory Commission
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June 11, 1987
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Page 2 Alternate Shutdown i
Vermont Yankee's Alternate Shutdown procedures require the "A" RHR loop to be utilized for shutdown cooling.
The "A" RHR loop is also required for augmented fuel pool cooling.
In the past fifteen years of operation, which includes at least three (3) full core off-loads, Vermont Yankee has never required the use of augmented (RHR) fuel pool cooling to supplement the normal-fuel pool cooling system. We have, however, on several occasions, used RHR cooling while shutdown to cool the core and the fuel pool at the same time when the fuel pool /Rx cavity gates are open.
In this situation, the fuel poc1 system is running and RHR is aligned to take a suction from the reacto:' and discharge to the fuel pool. This has been done, not because of heat load concerns, but rather as a tool to maintain better water clarity and maintain a more uniform temperature distribution.
It should be noted that in order tc line up the augmented fuel pool cooling modo, specific manual actions must be taken in accordance with the RHR pro-cedure to reverse two spectacle flanges. Operating in the augmented fuel pool cooling mode is not a normal occurrence and therefore would be logged in the control room log in accordance with AP 0153.
Demineralizers Although the Vermont Yankee spent fuel pool filter /demineralizers have been analyzed as capable of continuous operation at temperatures well above 150*F, Vermont Yankee herein commits to procedurally ensure icc!ation of the spent fuel pool filter /demineralizers at 140*F inlet temperature.
Control Room Alarms Vermont Yankee presently has a multitude of alarms which would immediately identify any potential problems with the Spent Fuel Pool Cooling System.
These alarms include:
1.
Fuel pool water level low; 2.
Fuel pool cooling pump trip; 3.
RBCCW pump trip; 4
RBCCW tank Hi/ Low; 5.
SW pump trip; and 7.
In addition to these alarms, fuel pool temperature is recorded continuously in the control room and is reviewed frequently by control room operators.
This review is in addition to the surveillance performed by the auxiliary operator who reads and records spent fuel pool temperature once per eight-hour shift.
It should also be noted that current Vermont Yankee admi-nistrative procedures have a maximum fuel pool temperature of 125*F.
Given
VERMONT YANKEE NUCLEAR POWER CORPORATION U.S. Nuclear Regulatory Commission June 11, 1987 Page 3 this administrative procedural limit and a 3*F/hr temperature rise in the event of loss of all fuel pool cooling (see section on fuel pool tem-perature rise), the operators would be able to isolate the demineralizers before their inlet temperature reached 140*F.
Based on the above, and the commitments in Enclosure I to record fuel pool temperature once per four hours in the event one fuel pool subsystem is inoperable, Vermont Yankee feels there are adequate means to identify and take appropriate corrective action well before exceeding the proposed Technical Specification limit for the spent fuel pool temperature.
Reactor Buildina Ventilation i
Vermont Yankee has evaluated a fuel pool temperature transient to 200*F and subsequent return to 150*F or less. We have determined that this excursion will have a negligible effect on the reactor building environment and the reactor building ventilation systems will remain operable.
Pool Tempe"ature Rise Calculation In response to the question concerning temperature rise in the fuel pool, we have calculated a very conservative 3.2*F per hour. This reflects a decay heat input at 42 days decay, using SRP analysis assumptions, and no ambient heat losses.
If the SRP conservatisms were removed from the decay heat analysis methods and small ambient heat losses were considered, the resultant temperature rise would be less than 2*F per hour. Considering this, a nominal 3*F per hour would be an appropriate heatup rate assuming a complete loss of fuel pool cooling occurs at the end of a normal refueling outage.
License Condition Vermont Yankee has previously demonstrated the capability of each of the spent fuel pool cooling subsystems to independently maintain a bulk fuel pool temperature limit of 150*F.
In response to the NRC staff questions regarding operational controls associated with the spent fuel pool cooling system, Vermont Yankee herein commits to administrative 1y control the license conditions as specified in Enclosure 1 to this letter by startup from the 1987 refuel outage.
In addition, these proposed limiting con-ditions for operation and associated surveillance requirements will be sub-mitted to NRC for approval as a separate Technical Specification amendment request as soon as practical, but no later than July 10, 1987.
To ensure system operability at the elevated temperatures associated with the proposed limiting conditions for operation, an evaluation has been per-formed of the required spent fuel pool cooling subsystems.
This evaluation has concluded that each of the components (pumps, valves, heat exchangers, etc.) piping and supports, and structures required are capable of operation at a fluid temperature of 200*F.
VERMONT YANKEE NUCLEAR POWER CORPORATION U.S. Nuclear Regulatory Commission June 11, 1987 Page 4 Vermont Yankee currently has administrative procedures in place which docu-ment the time and duration when RHR is aligned to spent fuel pool cooling (i.e., closed loop to spent fuel pool). AP 0150 and AP 0153 clearly state "Any change in the status of Technical Specification or safety-related equipment, or equipment that can affect full power operation" must be recorded with the time as to when it is placed into or out of operation.
Therefore, Vermont Yankee concludes that no further procedural changes are required.
We trust that the information and commitments provided by this letter are satisfactory and, accordingly, completes all of the information requested of Vermont Yankee to date associated with the subject spent fuel pool amendment requested. Should you have any questions, or require further information regarding this matter, please contact us.
Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION dus--- f Warren
. Murph Vice President an
/dm Manager of Operations 1
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