ML20045F377
| ML20045F377 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/25/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20045F372 | List: |
| References | |
| NUDOCS 9307070244 | |
| Download: ML20045F377 (6) | |
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[e UNITED STATES 5 -(W I Y ' y *E NUCLEAR REGULATORY COMMISSION WASHINGTON D.C. 20655 s..m j ENCLOSURE 3 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.1fA TO FACILITY OPERATING LICENSE NO. DPR-77 AND AMENDMENT N0.158 TO FACILITY OPERATING LICENSE NO. DPR-79 TENNESSEE VALLEY AUTHORITY SE000YAH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET N05. 50-327 AND 50-328
1.0 INTRODUCTION
By letter dated August 27, 1991, the Tennessee Valley Authority (the licensee) submitted a request for changes to the Sequoyah Nuclear Plant, Units 1 and 2 Technical Specifications (TS). The requested changes would revise TS Tables 3.3-3, 3.3-4, 3.3-5, 4.3-2, 3.3-6, 4.3-3, and the Bases for Section 3.9.9 related to the Containment Gas and Particulate Radiation Monitors (also known as the upper and lower containment radiation monitoring system) and the Containment Purge Air Exhaust Radiation Monitors. As a result of the proposed changes:
(1) the isolation signal generated by the Containment Gas and Particulate Radiation Monitors and the arresponding surveillance requirements would be deleted from Tables 3.3-3, 3.3-4, 3.3-5, 4.3-2, 3.3-6, and 4.3-3; (2) the exception to TS Section 3.0.4 would be applied to the Containment Purge Air Exhaust Monitor Radioactivity-High Isolation Signals and to the Manual Containment Ventilation Signals in Table 3.3-3; (3) Table 3.3-3, Action Statement 19, would be changed to specify that the containment purge supply and exhaust valves (not the containment ventilation isolation valves) must be maintained closed whenever there are less than the minimum number of operable channels available for either the manual isolation of the containment ventilation system or automatic containment ventilation isolation on a containment purge air exhaust monitor radioactivity high signal; (4) Table 3.3-6, Action Statement 28, would be changed to clarify the plant operating modes corresponding to the operability requirements for the Containment Air Purge Radiation Monitor; and (5) Table 3.3-3 and footnotes would be clarified to indicate that two switches must be operated simultaneously to initiate a manual trip of the Containment Spray Actuation System and the Phase "B" Isolation Actuation System. A supplemental letter dated November 6, 1992, supplied clarifying information that did not change the initial proposed no significant hazards consideration determination.
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. 2.0 EVALUATION t
The Containment Gas and Particulate Radiation System indicates, records and annunciates the airborne radioactivity levels in the containment on a panel in the main control room. There are three channels that monitor the upper containment area and three that monitor the lower containment area (one channel per level measures particulate activity, one channel per level measures noble gas activity, and one channel per level measures radiciodine activity). A high radiation signal from any of the two particulate or two noble gas channels initiates isolation of the Containment Ventilation System, including the isolation valves associated with the Containment Gas and Particulate Radiation Monitoring System itself.
In the past these radiation monitors have been the source of frequent spurious isolations that were not required for plant conditions. When this occurs, the ability to monitor the particulate activity, noble gas activity, and radiciodine activity in the containment is lost until the condition can be analyzed and resolved, and the radiation monitor isolation valves reopened.
During normal plant operation, the only ventilation system isolation valves that are normally open are the Containment Gas and Particulate Radiation Monitoring System valves. The only other containment ventilation isolation valves which could be opened are the purge system valves, which are opened only infrequently to allow the purge exhaust fans to operate. A radiation monitor connected to the suction of the purge exhaust fans, monitors activity in this airstream and causes isolation of the containment ventilation purge valves if high radiation is detected.
The Updated Final Safety Analysis Report (UFSAR) Section 12.2.4.1.2, " Airborne Monitoring Channels," states that, although containment ventilation isolation is a primary safety function, its initiation on high radiation by the Containment Gas and Particulate Radiation Monitoring System is not, having been incorporated into the design of the plant prior to the purge exhaust monitors. When the purge exhaust radiation monitors were installed, the isolation function of the Containment Gas and Particulate Radiation Monitoring System was retained, even though no credit would be needed for the isolation in the accident analysis. Therefore, the associated TS requirements were not changed in order to reflect the functions that uere actually installed, rather than those that were required. The safety function of containment ventilation isolation on high radiation is performed by the centainment purge exhaust monitors. Also, a high range radiation monitoring system is designed to monitor containment radioactivity during accident conditions and is not affected by the proposed change.
For plant conditions which require containment ventilation isolation, UFSAR Section 15.4.1 describes the bounding case for offsite dose considerations to l
be a large break loss of coolant accident. The release of radioactivity through the containment ventilation lines is assumed to be unfiltered with the lines fully open for five seconds.
For the presence of high radiation, the qualified isolation signal to mitigate the consequences of the accident is t
s a
. l provided by the containment purge radiation monitors, not the containment gas 4
and particulate radiation monitors.
i Another important function served by the containment gas and particulate radiation monitors is the detection of abnormal leakage of radioactive water from equipment located within the containment, especially at low leakage rates. However, the UFSAR takes no credit for isolation of the ventilation system under this condition.
The capability of detecting leakage would be enhanced by removal of the spurious and unnecessary isolations caused by the 4
containment gas and particulate radiation monitor, since the isolation valve would be less susceptible to spurious and unnecessary isolation signals.
The other signals that cause isolation of the containment ventilation system (including the containment gas and particulate radiation monitor isolation valves) and that cause safety injection are low steam line pressure, low pressurizer pressure, high containment pressure, high containment purge exhaust radiation, and manual. The signals are diverse, and are designed to cause isolation for reactor coolant system breaks in the range from the smallest to the bounding loss of coolant accident.
These signals and the valves isolated are not affected by the proposed change.
In summary, the proposed change will delete containment ventilation isolation caused by the containment particulate and noble gas radiation monitors, a signal which provides additional but unnecessary isolation capability, and j
which has been shown from past experience to be generated frequently and unnecessarily.
The only valves normally affected by the isolation signal are the containment radiation monitor isolation valves themselves, which has resulted in reduced ability to monitor the radiological conditions in the containment and unnecessary challenges to the isolation safety system.
In j
addition, implementation of the proposed change will not affect automatic isolation of the containment ventilation system when required under the design accident conditions.
Based on this analysis, the staff finds the proposed i
change acceptable.
As a result of this change, reference to the Containment Gas Monitor i
Radioactivity High instrumentation and the Containment Particulate Activity High instrumentation will be removed from Table 3.3-3 (Engineered Safety s
Feature Actuation System Instrumentation), Table 3.3-4 (Engineered Safety i
Feature Actuation System Instrumentation Trip Setpoints), Table 3.3-5 (Engineered Safety Features Response Times), Table 4.3-2 (Engineered Safety Feature Actuation System Instrumentation Surveillance Requirements), Table 1
3.3-6 (Radiation Monitoring Instrumentation), and Table 4.3-3 (Radiation l
Monitoring Instrumentation Surveillance Requirements) and is acceptable.
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The second proposed change would apply the exception to TS Section 3.0.4 (that is presently applied to other TS instruments) to the Containment Purge Air l
Exhaust Monitor Radioactivity-High Isolation signals and to the Manual i
Containment Ventilation Signals in Table 3.3-3.
TS Section 3.0.4 prevents entry into an operational mode unless the Limiting Conditions For Operation (LCO) for the new mode are met without reliance on the Action Statements. Any
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. exceptions to these requirements must be stated in the individual Specifications.
Generic Letter (GL) 87-09, " Sections 3.0 and 4.0 of the Standard Technical Specifications (STS) on the Applicability of Limiting Conditions for Operation and Surveillance Requirement," was issued on June 4, 1987 to clarify some provisions of the STS. One provision of the GL states that when an acceptable level of safety is provided for continued operation by the Action Statement, Specification 3.0.4 unduly restricts facility operation by not allowing changes to the mode of plant operation.
For an LC0 that has Action Statements permitting continued operation for an unlimited period of time, the GL indicates that entry into-an operational mode should be permitted in accordance with those Action Statements. This is consistent with NRC's regulatory requirements for an LCO. The restrictions on a change in operational modes should apply only where the Action Requirements thamselves establish a specified time interval in which the LCO must be met, or a shutdown of the facility would be required.
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In effect, then, the change proposed by the licensee would implement the GL guidance that would allow operational mode changes when the containment purge supply and exhaust valves are closed due to a loss of the mantal containment ventilation isolation capability or the containment purge air exhaust monitor radioactivity high instrumentation.
The staff has reviewed the proposed changes and determined that they comply with the guidance given in GL 87-09. They are, therefore, acceptable.
The third proposed change would revise Table 3.3-3, Action Statement 19, to specify that the Containment Purge Supply and Exhaust Valves (not the containment ventilation isolation valves) must be shut whenever the minieum number of operable channels are not available for manual isolation or containment purge air exhaust monitor radioactivity high isolation of the containment ventilation system. The present requirement to shut the containment ventilation isolation valves if the manual or the containment air purge exhaust monitor is inoperable results in isolation of the Containment Radiation Monitoring System in addition to the purge system. Therefore, the containment radiation system cannot monitor containment radioactivity and cannot function as a reactor coolant system leakage monitor.
The purpose of maintaining the containment ventilation isolation valves shut when less than the minimum channels are operable, is to ensure that no containment release paths to the outside are open when availability of the isolation is significantly degraded.
The purge supply and exhaust lines are the only containment ventilation lines that communicate with the outside air, and are supplied with a radiation monitor that shuts the isolation valves should high radiation levels be detected when the system is operating.
The containment radiation monitor is a closed system (air is returned to the containment) whose lines only penetrate the containment from the auxiliary building where the monitors are located and are designed for pressures up to i
. the containment design pressure. The auxiliary building has its own filtered ventilation system and isolation system (including isolation on high radiation). Therefore, any leakage from the containment radiation monitor would be small and contained within the Auxiliary Building. Hence, shutting the containment radiation monitor isolation valves when the containment ventilation isolation instrumentation is degraded serves no safety function.
When open, the containment purge air isolation valves (as well as the other containment ventilation isolation valves) will shut automatically if high radiation is detected by the containment purge air exhaust radiation monitors, or from any of the other isolation signals that would indicate a loss of coolant accident has occurred (low steam line pressure, low pressurizer pressure, high containment pressure), as well as manual. Also, the purge exhaust radiation monitor is required to be operable during plant operation in Modes 1, 2, 3, 4 and 6.
Therefore, it would be available when needed.
In summary, the only containment ventilation isolation valves that would be open during plant operation are the purge supply and exhaust valves, and the containment radiation monitor isolation valves.
It is undesirable to shut the containment radiation monitor valves during plant operation except when required by component problems. Therefore, the Action Statement that specifies the action that should be taken if the number of operable manual containment isolation channels or containment purge air exhaust monitor radioactivity high channels is less than that required, should be more appropriately applied to the Containment Purge and Exhaust Valves only, not to the containment ventilation isolation valves.
Based on this analysis, the staff finds the proposed TS change acceptable.
The fourth proposed change would revise Table 3.3-6, Action Statement 28, to clarify the plant operating modes corresponding to the operability requirements for the Containment Air Purge Radiation Monitor. Table 3.3-6 (Radiation Monitoring Instrumentation), Action Statement 28, states that when the number of operable Containment Purge Air Process Radiation Monitor Instrumentation channels is less than the number required, the requirements of l
Specification 3.9.9 must be applied.
Specification 3.9.9 is an LC0 that is applicable in the Refueling Mode only.
Therefore, to clarify the plant conditions that would correspond to all amlicable operating modes (not just the Refueling Mode), the licensee has proposed wording that clearly indicates that application of Specification 3.9.9 would apply to Mode 6, and that the requirements of Specification 3.3.2.1 for Unit 1 and Specification 3.3.2.2 for Unit 2 be applied for operation in Modes 1, 2, 3 and 4.
These specifications already contain the appropriate requirements for the Containment Air Purge Radiation Monitor System when operating in Modes 1, 2, 3 and 4.
Therefore, this change is administrative in nature and is acceptable.
The fifth proposed change would clarify the footnotes and Table 3.3-3 to indicate that two switches must be operated simultaneously to initiate a
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manual trip of the Containment Spray Actuation System and the Phase "B" Isolation Actuation System. This is an administrative change that does not affect the application of the specification, nor any limits, and is consistent with other applications of the note.
It is, therefore, acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Tennessee State official was notified of the proposed issuance of the amendments. The State official had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change the Surveillance Requirements. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (56 FR 49928). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
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5.0 CONCLUSION
l The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
D. LaBarge Date: June 25, 1993 k
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