ML17158A562
| ML17158A562 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 11/11/1994 |
| From: | PENNSYLVANIA POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML17158A560 | List: |
| References | |
| NUDOCS 9411160283 | |
| Download: ML17158A562 (10) | |
Text
ATTACHMENT 1 Technical Specification 3/4.3.8 Turbine Overspeed Protection System Mark-up for Susquehanna Units 1 &2 I'411160283 9@iiii P.DR.
!NSTRUHENTATION 3/4. 3. 8 TURBINE OVERSPEEQ PROTECTION SYSTEM LIMITIHG COHOITIOH FOR OPERATION 3.3.8 One turbine overspeed protection system shall be OPERABLE.
APPLICABILITY:
OPERATIONAL CONOITIONS 1 and 2.
ACTION:
Wth the above required turbine overspeed protectfon systen inoperable, within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> isolate the turbine frea the steam supply.
SURVEILLANCE REOUIRB1ENTS 4.3.8.1 The provisions of Specfffcatfon 4.0.4 are not applfcabla.
4.3.8. 2 The above required turbine overspeed protection system shall be deaonstratad OPERABLE:
92 a.
At least once per %days by:
Z.
Cyclfng 'each of the following valves i'roe the runnfng position and observfng valve closure:
a) four high pressure turbine control valves, b)
Sfx low pressure turbine coabfned intermediate
- valves, and b.
c c) four hfgh pressure turbfne stop valves.
At least once per IB months by performance of a CHANNEL CALIBRATION ot the turbine overspeed protection fnstrumentatfon.
At least once per 40 months by dfsasseablfng at least one of each oi'he above valves and perforsfng a visual and surface inspection of all valve seats, dfsks and steas and verfQfng no unacceptable flaws or corrosion.
SUSQUEHANNA - UNIT 1 3/4 "3-94
INSTRUMENTATION 3/4. 3. 8 TURBINE OVERSPE:-D PROTECTION SYSTEM LIMITING CONOITIOX FOR OPERATION 3.3.8 The turbine overspeed protection system shall be OPERABLE.
APPL:CABILITY:
OPERATIONAL CONQITIONS 1 and 2.
ACTION:
With the above required turbine overspeed protection system inoperable, wi hin 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> isolate the turbine from the steam supply.
SURVEILLANCE REQUIREMENTS 4.3.8.1 The provisions of Specification 4.0.4 are not applicable.
4.3.8.2 The above required turbine overspeed protection system shall be demons rated QPERABI ~:
92 a.
At least once per grays by:
1.
Cycling each of the following valves from the running position and observing valve closure:
0 a)
Four high, pressure turbine control valves, b)
Six low pressure turbine combined intermediate
- valves, and c}
Four high pressure turbine stop valves.
b.
At least once per 18 months by performance of a CHANNEL CALIBRATION of the turbine overspeed protection instrumentation.
c.
At least once per 40 months by disassembling at least one of each of the above valves and performing a visual and surface inspection of all valve seats, disks and stems and verifying no unacceptable flaws or corrosion.
SUS/UEHANNA - UNIT 2 3/4 3-95
IHSTRUMEHTATIOH BASES 3/4.3. 8 TURBINE OVERSPEED PROTECTION SYSTEM This specification is provided to ensure that the turbine overspeed protection system instrumentation and the turbine speed control valves are OPERABLE'and will protect the turbine from excessive overspeed.
Protect. on from turbine ex'cessme.
overspeed is required since excessive overspeed of the turbine could generate potentially damaging missiles which could impact and damage safety related components, equipment or structures.
CINSERTl 3/4.3.9 FEEDMATER/MAIN TURBINE TRIP SYSTEM ACTUATION IHSTRUMEHTATION The feedwater/main turbine trip system actuation instrumentation is provided to initiate ac ion of the feedwater system/main turbine trip system in the event of failure of feedwater controller under maximum demand.
SUSQUEHANNA - UNIT 1 B 3/4 3-7
T I
I
< UNIT 1 INSERT>
Technical Specification Amendment [0TBD, Date of Approval] extended the requirement for weekly steam valve surveillance testing to an interval not to exceed 92 days.
The surveillance test involves the cycling of each of the Main Turbine Stop, Control, and Combined Intermediate Valves (MainTurbine Valves) from the running position and observing valve closure.
General Electric recommended the extended surveillance test interval for Main Turbine Valves in TIL969 Revision 1 (12/27/93).
This test interval limits the probabilityof excessive overspeed, due to a Main Turbine Valve fail-to-close event, to the level accepted for missile generation and is within the predictive capabilities ofthe overspeed analysis.
The safety significance associated with the valve surveillance testing comes from the function of the Main Turbine Valves to close based on Electro-HydraulicControl response to prevent an overspeed condition ofthe turbine. Turbine overspeed is a concern because of the potential that the overspeed condition may lead to turbine failure.
Turbine failure may in turn lead to the generation of turbine missiles, with the potential to strike-and-damage safety-related structures, systems, and components.
Susquehanna replaced its original keyway turbine rotors with monoblock turbine rotors in 1986 (Ul) and 1988 (U2) due to concerns over keyway cracking identified by the turbine vendor.
The monoblock rotors installed at Susquehanna SES have an acceptably low probability of turbine missile damage to safety-related structures, systems, and components.
The monoblock design eliminates the keyway crack initiation site, which is the area between the rotor and the turbine wheel that can failand lead to turbine missiles. The change to the MainTurbine Valve surveillance frequency was based in part on the design integrity of the monoblock rotors installed at Susquehanna.
Susquehanna maintains spare keyway designed rotors forpotential use in either the Unit 1 or Unit 2 Low Pressure Turbine.
The keyway designed rotors have been found to be susceptible to Stress Corrosion Cracking which can lead to turbine failure. Therefore, ifany of the spare keyway design rotors are reinstalled into the Low Pressure Turbine, the turbine valve surveillance interval forMain Turbine Stop, Control, and Combined Intermediate Valves must be re-evaluated or revised to comply with the recommendations of TIL969 Revision 0.
This re-evaluation willbe accomplished via the design change process associated with installing the spare rotors.
INSTRUMENTATION BASES 3/4.3.8 TURBINE OVERSPEED PROTECTION SYSTEM This specification is provided to ensure that the turbine overspeed protection system instrumentation and the turbine speed control valves are OPERABLE and will protect the turbine from excessive overspeed.
Protection from turbine excessive overspeed is required since excessive overspeed of the turbine could generate potentially damaging missiles which could impact and damage safety related components, equipment or structures.
(INSERT+~
3/4.3.9 FEEDWATER/MAIN TURBINE TRIP SYSTEM ACTUATION INSTRUMENTATION The feedwater/main turbine trip system actuation instrumentation is provided to initiate action of the feedwater system/main turbine trip system in the event of failure of feedwater controller under maximum demand.
SUSQUEHANNA - UNIT 2 B 3/4 3-7
'I t I
I
< UNIT 2 INSERT>
Technical Specification Amendment [¹TBD, Date of Approval] extended the requirement for weekly steam valve surveillance testing to an interval not to exceed 92 days.
The surveillance test involves the cycling of each of the Main Turbine Stop, Control, and Combined Intermediate Valves (MainTurbine Valves) from the running position and observing valve closure.
General Electric recommended the extended surveillance test interval for Main Turbine Valves in TIL969 Revision 1 (12/27/93).
This test interval limits the probabilityof excessive overspeed, due to a Main Turbine Valve fail-to-close event, to the level accepted for missile generation and is within the predictive capabilities ofthe overspeed analysis.
The safety significance associated with the valve surveillance testing comes from the function of the Main Turbine Valves to close based on Electro-HydraulicControl response to prevent an overspeed condition ofthe turbine. Turbine overspeed is a concern because of the potential that the overspeed condition may lead to turbine failure.
Turbine failure may in turn lead to the generation of turbine missiles, with the potential to strike-and-damage safety-related structures, systems, and components.
Susquehanna replaced its original keyway turbine rotors with monoblock turbine rotors in 1986 (Ul) and 1988 (U2) due to concerns over keyway crackingidentified by the turbinevendor.
The monoblock rotors installed at Susquehanna SES have an acceptably low probability of turbine missil'e damage to safety-related structures, systems, and components.
The monoblock design eliminates the keyway crack initiation site, which is the area between the rotor and the turbine wheel that can failand lead to turbine missiles. The change to,the MainTurbine Valve surveillance frequency was based in part on the design integrity of the monoblock rotors installed at Susquehanna.
Susquehanna maintains spare keyway designed rotors forpotential use in either the Unit 1 or Unit 2 Low Pressure Turbine.
The keyway designed rotors have been found to be susceptible to Stress Corrosion Cracking which can lead to turbine failure. Therefore, ifany of the spare keyway design rotors are reinstalled into the Low Pressure Turbine, the turbine valve surveillance interval forMain Turbine Stop, Control, and Combined Intermediate Valves must be re-evaluated or revised to comply with the recommendations of TIL969 Revision 0.
This re-evaluation willbe accomplished via the design change process associated with installing the spare
- rotors,
ATTACHMENT 2 General Electric Technical Basis for Extending GETurbine Valve Surveillance Intervals NEDO-32155, GE Letter dated 9/30/94