ML042110013
| ML042110013 | |
| Person / Time | |
|---|---|
| Site: | Rensselaer Polytechnic Institute |
| Issue date: | 07/14/2004 |
| From: | Fahey W, Winters D Rensselaer Polytechnic Institute |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML042110013 (3) | |
Text
DEPARTMENT OF MECHANICAL, 9 tJ.119 eAEROSPACE, AND NUCLEAR ENGINEERING July 14, 2004 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 License # CX-22 Docket # 50-225
Subject:
Proposed Change to Technical Specifications
Dear Sir:
This letter requests approval of a change to the Rensselaer Polytechnic Institute (RPI) Reactor Critical Facility (RCF) Technical Specifications. Table 2 of the RCF Technical Specification lists the reactor interlocks. RPI requests approval to remove the interlock associated with the 400 cycle Synchro Power Supply.
Current Rod Position System The RCF Rod Position System consists of synchro receivers and transmitters, limit switches and related indicators, and a 400 Hz motor-generator (MG) set.
The transmitters are located on the support structure for the rod drives and are mechanically coupled to the rod drive pinon shaft. The receivers are located on the Reactor Control Panel (RCP). Limit switches in the gearing for the synchro transmitter activate ROD BOTTOM and ROD TOP incandescent lights on the RCP. The ROD TOP limit switch also halts outward control rod motion when the control rod reaches the top of its travel. The MG set provides power to the synchro receivers and transmitters. The incandescent lights are energized by 120 volt, 60 Hz power.
The MG set output breaker is part of the control rod outmotion interlock circuit.
This breaker must be shut to enable control rod outmotion. The basis for the interlock is to ensure that the operator has power to the rod position system, and, therefore, indication of control rod motion and position, before any control rod may be withdrawn.
Replacement Rod Position System A new Rod Position System uses rotary encoders to detect rod motion and digital counters to display position. The existing limit switches are unchanged and Rensselaer Polytechnic Institute AD 110 8th Street I Troy, NY 12180-3590 USA
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retain all existing functions. The MG set is unnecessary with this replacement equipment.
A Simpson SE-1 00 encoder is mechanically coupled to the rod drive pinon shaft in the same manner as the synchro transmitter. The encoder generates 100 pulses per rotation of the encoder shaft. A Simpson S660 digital counter located on the RCP detects the encoder pulse train that results whenever the rods move and calculates the rod position for both outward and inward rod motion. The counter displays rod position in inches from the bottom with 0.01 inch resolution.
This is the same resolution provided by the synchro system.
The counter operates from 120VAC and contains an excitation module that provides 12VDC to the encoder. The power for the counter will come from RCP control power. The control power is key locked such that reactor operation is not possible unless the reactor console power keylock switch is operated to the ON position. This source of power functionally replaces the MG set and is listed on Table 2 of the Technical Specifications as an interlock.
Changing the rod position system has no effect on reactor safety. The new system requires power from an interlocked source such that no rod motion can occur unless the position indicators are energized. This satisfies the basis for the interlock that the operator know rod position before and during all outward rod motion. If power is cutoff by placing the console power keylock switch OFF, thus deenergizing the rod position indicators, the reactor will scram.
The RCF Safety Analysis Report (SAR) briefly notes that rod position is by a synchro system. This statement is in the description section of the reactor components. While the statement will be incorrect when the new rod position equipment replaces the synchro system, the specific rod position equipment does not change the conclusion of the SAR. That is, the most severe reactor casualty remains unchanged and is not affected by the equipment used to determine the position of the control rods. The SAR will be corrected to reflect the new equipment when next updated.
Function Verification The planned Rod Position System was temporarily installed and operated in parallel with the existing synchro system for testing purposes, prior to permanent installation. Correct function of the new set of equipment was verified by comparing indicated positions over the full stroke of the control rods. Operation was satisfactory.
In order to verify that the new equipment was not interfering with rod scrams, the periodic rod drop time checks were performed with the encoders coupled to rods.
No change from the prior check was observed.
Safety Review The RPI Nuclear Safety Review Board (NSRB) has reviewed the proposed Technical Specification change and the planned change to the Rod Position System. The NSRB agrees that the modifications maintain the same level of safety as the original rod position equipment, and that the Technical Specification
change is appropriate. NSRB approval is recorded in the minutes of the May 10, 2004 NSRB Meeting.
Action Requested The Nuclear Regulatory Commission is requested to approve removing the 400 cycle Synchro Power Supply from Table 2 of the RPI RCF Technical Specifications.
Yours truly, J
4 Will Fahey Environmental Health & Safety Rensselaer Polytechnic Institute Glenn Winters, Director Critical Facilty Rensselaer Polytechnic Institute cc:
J.A. Tichy M.Z. Podowski L. Gerhardt G.P. Peterson USNRC Region I 475 Allendale Road King of Prussia, PA 19406-1415