ML19338G607
| ML19338G607 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 10/30/1980 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML19338G603 | List: |
| References | |
| PROC-801030, NUDOCS 8010310332 | |
| Download: ML19338G607 (4) | |
Text
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U, DOCKET NO. 50-245 ATTACHMENT MILLSTONE NUCLEAR POWER STATION, UNIT NO. 1 BWR SCRAM DISCHARCE SYSTEM OCTOB ER', 1980 8010810331
Long-Term Evaluation of Scram Discaarse System i
The utilities have reviewed General Electric's evaluation and are
'ollowing the ongoing INP0/NSAC study on f ailure of the control rods to dly insert on a scram signal at Brown's Ferry. The utilities agree that Brown's Ferry there was an undetected accumulation of water in the scram charge volume. Subsequent testing at some plants has also indicated that certain conditions the instrumentation may not give consistent level scation due to the piping configuration as it ties into the instrument
.ume.
Scope The following is a listing of design and operational criteria that shall be followed by the utilities in formulating individual design changes. The criteria has taken into consideration the original system criteria, problems experienced in the operation of the system and concerns regarding operability and reliability. Criteria which have been added or changed as a result of this evaluation are denoted by an asterisk (*).
For the purpose of this discussion, the word " system" includes all components downstream of the scram exhaust valves. The philosophy for evaluation of the design is that the safety function is of prine concern. The safety boundaries are whatever affects the scram function of the system. The evaluation must show that the safety boundaries considered meet this philosophy.
Functional Criteria 4
- The scram discharge volume shall have sufficient capacity to receive and c-atain water exhausted by a full reactor scram without adversely affecting control rod drive scram performance.
Safety Criteria 1.* No single active failure of a component, or service function shall prevent a reactor scram, under the most degraded conditions that are operationally acceptable.
2.* No single active failure shall prevent uncontrolled loss of reactor coolant.
3.* The scram discharge system instrumentation shall be designed to provide redundancy, to oper:te reliably under all conditions, and shall not be adversely affected by hydrody:iamic forces or flow characteristics.
4.
System operating conditions which are required for scram shall be continuously monitored.
5.* Repair, replacement, adjustment, or surveillance of any system component shall not require the scram function to be bypassed.
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_0perational Criteria i
1.
Level instrumentation shall be designed to be maintained, tested, j
or calibrated during plant operation without causing a scram.
l 2.
The system shall include sufficient supervisory instrumentation and alarms to permit surveillance of system operation.
3.
The system shall be designed to minimize the exposure of operating personnel to radiation.
4.* Vent paths shall be provided to assure adequate drainage in preparation for scram reset.
5.* Vent and drain functions shall not be adversely affected by other system interfaces. The otdective of this requirement is to preclude water backup in the scram instrument volume which could cause spurious scram.
Design Criteria a
1.* The scram discharge headers shall be sized in accordance with GE GER-52 and shall be hydraulically coupled to the instrumented volume (s) in a manner to permit operability of the scram level instru-mentation prior to loss of system function.
Each system shall be analyzed based on a plant-specific maximum inleakage to ensure that the system function is not lost orior to initiation of automatic scram.
Maximum inleakage is the maximum flow rate through the scram discharge line without control rod motion summed over all control rods. The analysis should show no need for vents or drains.
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2.* Level instrumentation shall be provided for automatic scram initiation while sufficient volume exists in the scram discharge volume.
j 3.* Instrumentation taps shall be provided on the vertical instrument volume and not on the connected piping.
4.* The scram instrumentation shall be capable of detecting water
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accumulation in the instrumented volume (s) assuming a single active failure in the instrumentation system or the plugging of an instrument line.
5.* Structural and component design shall consider loads and conditions including those due to fluid dynamics, thermal expansion, internal pressure, seismic considerations, and adverse environments.
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6.* The power-operated vent and drain valves shall close under loss of air and/or electric power. Valve position indication shall be provided in the control room.
7.* Any reductions in the system piping flow path shall be analyzed to assure system reliability and operability under all modes of opera-tion.
3.* System piping geometry (i.e., pitch, line size, orientation) shall be such that the system drains continuously during normal plant operation.
9.* Instrumentation shall be provided to aid the operator in the detection of water accumulation in the instrumented volume (s) prior to scram initiation.
10.* Vent and drain line valves shall be provided to contain the scram dis:harge water, with a single active failure and to minimize operational exposure.
Surveillance Criteria 1." Vent and drain valves shall be periodically tested.
2.* Verifying and level detection instrumentation shall be periodically tested in place.
3.* The operability'of the entire system as an integrated whole shall be demonstrated periodically.and during each operating cycle, by demonstrating scram instrument response and valve function at pressure and temperature at approximately 50% control rod density.
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