ML20214D582
| ML20214D582 | |
| Person / Time | |
|---|---|
| Issue date: | 11/20/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20214D573 | List: |
| References | |
| NUDOCS 8611240152 | |
| Download: ML20214D582 (9) | |
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OFFICE OF NUCLEAR REACTOR REGULATION UNITED STATES NUCLEAR REGULATORY COMMISSION ADVISORY OPINION ON COMBUSTION ENGINEERING 2825 MW(t) NUCLEAR STEAM SUPPLY SYSTEM I.
INTRODUCTION A.
Background
By letter dated October 27, 1986 (LD-86-047), Combustion Engineering (CE) submitted a proprietar Engineering 2825 MW(t)y document entitled "A Description of the Combustion System 80 Nuclear Steam Supply System" and requested an opinion from the NRC staff.
In particular, CE asked whether "there is reasonable assurance that the design, if properly implemented, could satisfy the same regulatory standards applied to the CESSAR-Final Design Approval (FDA-2)".
CE stated that the 2825 MW(t) design will consist of their standard System 80 design with major components appropriately sized. The 3817 MW(t) System 80 NSSS has been reviewed by the staff under docket number STN-50-470; the results of the review were reported in a staff Safety Evaluation Report (SER),
NUREG-0852 and its supplements. A Final Design Approval (FDA-2) was issued by the NRC in December 1983.
B.
Summary Description of 2825 MW(t) Design The 2825 MW(t) System 80 design includes the NSSS and supporting auxiliary and safety systems. The scope of the design is the same as that for the i
3817 MW(t) NSSS. The RCS arrangement and major component design is essentially the same as the 3817 MW(t) except for appropriate changes in the reactor vessel and steam generators commensurate with the power output for the 2825 MW(t) unit. The total heat transfer area of the steam generators is appropriately sized.
Relative to core thermal output, the steam generators provide approximately the same heat removal capability.
' Consistent with the power output, the 2825 MW(t) core is appropriately l
stadified. The fuel assemblies are similar to those described in CESSAR-F, except modified integral poison rods are used in the shimmed fuel assemblies.
The use of these poison rods provides a slightly lower average linear heat generation rate than that presented in CESSAR-F.
Because of the modified core, the number of control element assemblies is consistent with maintaining the same shutdown worth as described in CESSAR-F.
The incore instrumentation as described in CESSAR-F provides power distribution monitoring in the modified core.
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. All other components and systems are essentially the same as those described in CESSAR-F.
Design requirements (interfaces) for the Balance of Plant are provided to the architect-engineer in detailed interface documents which describe the design requirements necessary to assure that the 2825 MW(t) System 80 NSSS will perfom as designed. Based on the same scope of design, CE will impose the same functional interface requirements as those described in CESSAR-F.
II. DESIGN OF STRUCTURES, COMPONENTS, EQUIPMENT, AND SYSTEMS A.
General Desion Criteria The report states that the 2825 MW(t) System 80 design conforms to the General Design Criteria for Nuclear Power Plants, Appendix A to 10 CFR 50 and to the same degree and in the same manner as described in the Combustion Engineering Standard Safety Analysis Report - FSAR (CESSAR-F).
B.
Codes and Standards CE has stated that the 2825 MW(t) System 80 design conforms to the same or more recent versions of the industry accepted codes and standards as applied in CESSAR-F. The report also states that the codes and standards applied to the design confom with the requirements of 10 CFR 50.55(a),
and the NRC Regulatory Guides will be complied with to the same extent and in the same manner as described in CESSAR-F.
C.
Seismic Clarification and Design Combustion Engineering stated that they will designate structures, systems, and components which are important to safety and designed to remain functional in the event of a safe shutdown earthquake as seismic Category I.
The analysis methods and procedures used to assure that seismic Category I structures, systems, and components meet applicable criteria are the same as those described in CESSAR-F. Combustion Engineering further stated that they will supply appropriate interface data to the purchaser for structural c:esign purposes. Combustion Engineering will perfonn dynamic analyses using actual building response spectra and time histories to verify the adequacy of the design loads specified for the major components of the Reactor Coolant System (RCS).
D.
Safety Classification Individual fluid system components important to safety are classified in accordance with ANSI N18.2 and Regulatory Guide 1.26 in the same manner as t
described in CESSAR-F.
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. Fracture toughness requirements will be imposed in the same manner as described in CESSAR-F on internals for pressure retaining parts of ASME Class 2 and 3 system components. Test methods, acceptance, and exemption criteria are in confonnance with the ASME Code Section III.
E.
Missiles Combustion Engineering stated in their submittal that they will identify the potential and postulated missiles to the purchaser for design of suitable protective measures. The method for determining potential missiles is described in CESSAR-F.
F.
Protection Against Postulated Piping Failure The design and analysis of the RCS for the 2825 MW(t) System 80 with respect to pipe breaks will be in accordance with the same methodology used for the 3817 MW(t) System 80, as described in CESSAR-F.
G.
Equipment Qualification The report states that equipment qualification, both seismic and environ-mental, will be performed in the same manner as described in CESSAR-F.
III. REACTOR, FUEL AND INTERNAL STRUCTURES The 2825 MW(t) System 80 core consists of the appropriate number of fuel assemblies. The core power, height and equivalent diameter, number of fuel assemblies, and fuel rod array are the same as those of a previously-licensed CE NSSS.
A.
Fuel System Design CE states that the 2825 MW(t) System 80 fuel system design bases are the same as those for CESSAR-F. The fuel assembly design is the same as those of previously licensed CE NSSSs and CESSAR-F except that modified burnable poison rods are used in the shimmed fuel assemblies. Also, fewer burnable poison rods are used in the 2825 MW(t) System 80 core.
The modified burnable poison rods have been used in other licensed plants for some time. The use of fewer burnable poison rods in the 2825 MW(t)
System 80 core allows the use of a greater number of enriched U0 rods and thereby slightly reduces the average linear heat generation rate 2 The design of the 2825 MW(t) System 80 control element assemblies are the same as those of CESSAR-F except that part-length control element assemblies (PLCEAs) have been modified. The use of the modified PLCEAs will eliminate the potential positive reactivity additions of the unmodified PLCEAs for dropped rod events.
Based on the similarity of the 2825 MW(t) System 80 fuel system design to that of CESSAR-F and other previously-licensed plants, the staff concludes that there is reasonable assurance that the design, if properly implemented, can satisfy the same regulatory standards as those that were applied to the CESSAR-F FDA.
B.
Nuclear Desion CE states that the 2825 MW(t) System 80 nuclear design bases are the same as those for CESSAR-F. CE also states that the 2825 MW(t) System 80 control element assemblies, including the modified PLCEAS, will provide shutdown margins comparable to those of CESSAR-F. The other core physics parameters of the 2825 MW(t) System 80 design, including reactivity coefficients and kinetic parameters, are stated to be similar to those of CESSAR-F.
C.
Thermal and Hydraulic Desian CE states that the 2825 MW(t) System 80 thermal-hydraulic desian bases are the same as those for CESSAR-F. CE also states that the 2825 AW(t) System 80 is expected to have the same thermal-hydraulic characteristics as those of CESSAR-F; since the reactor vessel internals are similar to those of CESSAR-F the linear heat generation rates and minimum departure from nucleate boiling ratios are comparable to or better than those of CESSAR-F; and the flow areas and reactor coolant pumps are sized to produce local fluid velocities comparable to those of CESSAR-F.
D.
Reactor Internals Except for the size, the reactor internal structures are similar to those described in CESSAP-F.
E.
Control Element Drives CE states that the 2825 MW(t) System 80 control element drive mechanisms (CEDMs) are the same as those used for CESSAR-F. Therefore, the staff concludes that the CEDMS can satisfy the same regulatory standards as those that were applied to the CESSAR-F FDA.
IV. REACTOR COOLANT SYSTEM AND CONNECTED SYSTEMS A.
Pressure Boundary The Reactor Coolant pressure boundary materials, design bases, inservice inspection, and leakage detection are identical to thqse described in CESSAR-F.
. i B.
Reactor Yessel The 2825 MW(t) System Reactor Vessel is the same design as described in CESSAR-F, appropriately modified for the different power levels. Vessel design and fabrication are in accordance with the ASME Boiler and Pressure Vessel Code,Section III and 10 CFR 50 Appendix G.
The irradiation surveillance program for the 2825 MW(t) reactor vessel adheres to ASTM E185-73 and satisfies 10 CFR 50 Appendix H as described in CESSAR-F. Pressure and temperature limitations are determined in accordance with 10 CFR 50 Appendix G.
Projected neutron fluence is very close to that projected for the 3817 MW(t) design described in CESSAR-F.
C.
Pressurizer Overpressure Protection Overpressure protection of the 2825 MW(t) System 80 reactor coolant system is provided by spring-loaded safety valves installed in piping connected to the top of the pressurizer. The normalized relieving capacity is the same as CESSAR-F.
D.
Reactor Coolant Pumps The reactor coolant pumps (RCP) are of the same design as described in CESSAR-F. A modification of the is incorporated in the 2825 MW(t) pump hydraulics (impeller and diffuser) plant design; otherwise all other pump components are the same.
The RCP motor incorporates a flywheel to provide coastdown flow following loss of power to the pumps.
Pump flywheel integrity meets the same requirements as listed in CESSAR-F.
E.
Steam Generator The steam generators are of the same design as described in CESSAR-F with appropriate sizing consistent with the NSSS thermal design.
F.
_ Pressurizer The 2825 MW(t) System 80 employs the same pressurizer design as described in CESSAR-F.
G.
Residual Heat Removal CE states that the 2825 MW(t) System 80 systems utilized to achieve cold shutdown are the same as those used for CESSAR-F.
In the CESSAR-F design, the auxiliary pressurizer spray (APS) system is relied upon for reactor
. coolant system depressurization during natural circulation cooldown. As discussed in Section VII.B of this report, the need for the APS system and its supporting systems to be safety grade remains a subject of discussion between the staff and CE.
Notwithstanding the open issue related to the APS system, however, the -
staff concludes that the systems utilized to achieve cold shutdown can satisfy the same regulatory standards as those that were applied to the CESSAR-F FDA.
V.
ENGINEERED SAFETY FEATURES A.
Emergency Core Cooling System CEstatesthatthe2825MW(t) System 80emergencycorecoolingsystem (ECCS) design is identical to that of the CESSAR-F design. The high pressure and low pressure safety injection pumps, and the safety injection tanks are a similar size to those for CESSAR-F. Also, like the CESSAR-F design, the high pressure safety injection pumps are designed with a shutoff head sufficiently low to preclude challenges to the primary safety valves.
Use of the CESSAR-F ECCS design on the modified 2825 MW(t) System 80 reactor will result in a different injection capacity relative to that of the CESSAR-F design. While this variation in injection capacity should significantly reduce the peak cladding temperatures resulting from small-break loss-of-coolant accidents, it may increase the potential for overcooling the reactor vessel.
This aspect of the design will have to be considered in establishing the overcooling limits of the vessel.
B.
Containment Isolation System The Containment Isolation System for the 2825 MW(t) System 80 design is identical to that described in CESSAR-F.
C.
Containment Spray System The 2825 MW(t) System 80 design includes interface criteria which require the purchaser to provide a Containment Spray System which has features and capabilities identical to the system described in CESSAR-F.
D.
Mass and Energy Releases for Postulated Events Mass energy release data will be calculated for the 2825 MW(t) design using the same methods as described in CESSAR-F. Mass energy releases will vary from those described in CESSAR-F for both LOCA and MSLB's.
. VI.
INSTRUMENTATION AND CONTROLS A.
Reactor Protective System The 2825 MW(t) System 80 design utilizes a Reactor Protective System (RPS) which is identical to that described in CESSAR-F.
It employs a two-out-of-four trip logic enabling one channel to be bypassed while maintaining adequate fuel and reactor coolant system protection.
High local power density and low departure from nucleate boiling ratio trips are accomplished via the digital Core Protection Calculators (CPC).
The Core Protection Calculators are of the same design as described in CESSAR-F.
B.
Enoineered Safety Features Actuation Systems The Engineered Safety Features Actuation Systems (ESFAS) in the 2825 MW(t)
System 80 design are identical to the system used in CESSAR-F.
It operates on selective two-out-of-four logic.
C.
Nuclear Instrumentation The nuclear instrumentation utilized in the 2825 MW(t) System 80 design is as described in CESSAR-F. The number of incore monitors are consistent to core design. The fixed incore monitoring assemblies are strategically distributed about the core (in essentially the same locations as in the 3817 MW(t) System 80 design) to permit representative three dimensional flux mapping. The movable system consists of two movable detectors which Can be positioned at various Core locations.
D.
Supplementary Protection System Combustion Engineering stated that the 2825 MW(t) design will contain ATWS mitigating circuitry which will comply with 10 CFR 50.62.
E.
Control Systems The 2825 MW(t) System 80 design includes control systems identical to those l
described in CESSAR-F. These systems provide the capability to automatically i
follow limited load changes, accommodate load rejections of any magnitude, and withstand the loss of one of two operatino feedwater pumps.
F.
Inadequate Core Coolino Instrumentation CE states that the 2825 MW(t) System 80 inadequate core cooling instrumenta-tion system is the same as that of CESSAR-F. Therefore, the staff concludes that the ICCI system can satisfy the same regulatory standards as those that were applied to the CESSAR-F FDA.
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. VII. AUXILIARY SYSTEMS A.
_ Fuel Handlino The fuel handling system for the 2825 MW(t) System 80 is identical to that described in CESSAR-F.
B.
Chemical and Volume Control System CE states that the 2825 MW(t) System 80 chemical and volume control system (CVCS) is identical to that of CESSAR-F.
In the CESSAR-F design, the APS system is a subsystem of the CVCS which, with its supporting systems, is relied upon for reactor coolant system depressurization during natural circulation cooldown and in mitigating the consequences of a steam generator tube rupture accident. As a result of start-up experience on the 3817 MW(t) unit, the staff requested (letter dated October 29,1985)
CE to address the need for the APS system and its supporting systems to be safety grade. No response has been received to date so the resolution of the question remains open. However, in their October 28, 1986 submittal, CE stated that "to the extent applicable start-up experience results in changes to the design, analysis or interfaces described in CESSAR-F, the necessary changes will also be incorporated in the 2825 MW(t) design."
Notwithstanding the question related to the APS system, based on the similarity of the 2825 MW(t) System 80 CVCS to that of CESSAR-F, the staff concludes that there is reasonable assurance that the design of the CVCS, if properly implemented, can satisfy the same regulatory standards as those that were applied to the CESSAR-F FDA.
VIII. INITIAL TEST PROGRAM CE states that the 2825 MW(t) System 80 design utilizes an initial test program identical to the one described in CESSAR-F. Further, CE states that test acceptance criteria will be determined in the same manner as for the tests described in CESSAR-F.
IX. ACCIDENT ANALYSES CE states that the 2825 MW(t) System 80 design will be evaluated with the same analysis methods and against the same acceptance criteria as the CESSAR-F design. Based on the similarity of the 2825 MW(t) System 80 design to that of CESSAR-F, the staff concludes that there is reasonable assurance that the design, if properly implemented, can satisfy the same regulatory standards as those that were applied to the CESSAR-F FDA.
X.
Conclusion The staff has previously reviewed and approved the 3817 MW(t) CESSAR System 80 nuclear steam supply system reference design.
The staff issued the Final Design Approval, FDA-2, on December 21, 1983. Much of the proposed 2825 MW(t) unit is the same as the CESSAP 3817 MW(t). The l
. differences that do exist are primarily due to the appropriate modification of components, rather than in the design. Based on the information provided to the staff for review in the October 27, 1986 submittal, it appears that there is reasonable assurance that the 2825 MW(t) design, if properly implemented, could satisfy the same regulatory standards applied to the CESSAR Final Design Approval (FDA-2).
IX. REFERENCES 1.
October 27, 1986 letter, Scherer (CE) to Denton (NRC), " Request for Advisory Opinion."
2.
NUREG-0852, " Safety Evaluation Report Related to the Final Design of the Standard Nuclear Steam Supply Reference System CESSAR System 80," November 1981.
3.
NUREG-0852, " Safety Evaluation Report Related to the Final Design of the Standard Nuclear Steam Supply Reference System CESSAR System 80," Supplement No.1 March 1983.
4 NUREG-0852, " Safety Evaluation Report Related to the Final Design of the Standard Nuclear Steam Supply Reference System CESSAR System 80," Supplement No. 2, September 1983.
5.
October 29, 1985 letter, Thompson (NRC) to Scherer (CE), " Auxiliary Pressurizer Spray System for CESSAR-F."
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