ML17332A854
| ML17332A854 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 07/12/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17332A853 | List: |
| References | |
| NUDOCS 9507180456 | |
| Download: ML17332A854 (5) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.
197 TO FACILITY OPERATING LICENSE NO.
DPR-58 AND AMENDMENT NO. 182 TO FACILITY OPERATING LICENSE NO.
DPR-74 INDIANA MICHIGAN POWER COMPANY DONALD C.
COOK NUCLEAR PLANT UNIT NOS.
1 AND 2 DOCKET NOS. 50-315 AND 50-316
- 1. 0 INTRODUCTION By letter dated March 31, 1995, the Indiana Michigan Power Company (the licensee) requested amendments to the Technical Specifications (TSs) appended to Facility Operating License Nos.
DPR-58 and DPR-74 for the Donald C.
Cook Nuclear Plant, Unit Nos.
1 and 2.
The proposed amendments would revise TS Section 3.9.4 to allow, under certain conditions, both containment personnel airlocks to be open during core alterations.
The current TSs require that a minimum of one containment personnel airlock
- door, as well as other containment penetrations, be closed during fuel movement and core alterations.
This requirement is to prevent the release of radioactive material in the event of a fuel handling accident.
The licensee stated that during refueling outages, other work in the containment continues concurrently with fuel movement and core alterations.
The licensee estimated that during the 1994 refueling outage, for the period bounding core alterations, there were 10,200 entries to and exits from containment.
The licensee indicated that assuming an average of five persons per containment personnel airlock cycle, the containment personnel airlock doors were cycled 200 times a day and the heavy use of the containment personnel airlock during refueling has led to problems in the gear and interlock alignments of the doors'ocking mechanism and handwheel failures, raising the concern that the doors may not be operable in the event of an accident.
The licensee further stated that there are large numbers of people in the containment during a
refueling outage and in the event of an accident, it would take a number of containment personnel airlock cycles to evacuate personnel from the containment, releasing more containment air with each containment personnel airlock cycle.
2.0 EVALUATION The proposed change would revise the TSs to permit both doors of a containment personnel airlock to be simultaneously open during Mode 6 operations under certain conditions.
Those conditions would be:
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One door in each airlock is
- OPERABLE, b.
Refueling cavity level is greater than 23 feet above the fuel, and c.
A designated individual is available at all times to close the airlock if required.
As previously noted, this would reduce containment personnel airlock door wear and facilitate personnel access.
The licensee proposes that a designated individual be stationed at the auxiliary building side of the containment personnel airlock to ensure that the doors are kept unblocked and to be available to close the containment personnel airlock doors in the event of an accident and evacuation of the containment is required.
Each of the D.C. Cook containments contains two containment personnel airlocks connecting the containment interior with the auxiliary building.
The containment personnel airlock is provided for the purpose of permitting personnel to enter and exit the containment while maintaining the integrity of the containment pressure boundary.
Each containment personnel airlock contains two airlock doors with a personnel chamber between the doors.
In reactor operational modes 1, 2, 3, and 4, at least one of the two doors must be closed.
Mechanical interlocks ensure that both doors cannot be opened at the same time.
During shutdown and refueling operations, both doors may be opened at the same time (the interlock mechanism is intentionally disabled) unless core alterations or movements of irradiated fuel in containment are in progress.
The applicable staff positions regarding opening of containment personnel airlock doors during Mode 6 (Refueling Operations) are stated in Bases Section 3.9.4 of the improved Standard Technical Specifications, NUREG-1431, "Standard Technical Specifications Westinghouse Plants" (iSTS).
Text excerpted from the iSTS states:
The containment air locks, which are part of the containment pressure
- boundary, provide a means for personnel access during MODES 1, 2, 3, and 4 operation....
Each air lock has a door at both ends.
The doors are normally interlocked to prevent simultaneous opening when containment OPERABILITY is required.
During periods of unit shutdown when containment closure is not required, the door interlock mechanism may be disabled, allowing both doors of an air lock to remain open for extended periods when frequent containment entry is necessary.
During CORE ALTERATIONS or movement of,irradiated, fuel assemblies within containment, containment closure is required; therefore, the door interlock mechanism may remain disabled, but one air lock door must always remain closed.
The requirements on containment penetration closure ensure that a release of fission product radioactivity within containment will be restricted from escaping to the
environment.
The closure restrictions are sufficient to restrict fission product radioactivity release from containment due to a fuel handling accident during refueling.
During CORE ALTERATIONS or movement of irradiated fuel assemblies within containment, the most severe radiological consequences result from a fuel handling accident.
The fuel handling accident is a postulated event that involves damage to irradiated fuel.
Fuel handling accidents include dropping a single irradiated fuel assembly and handling tool or a heavy object onto other irradiated fuel assemblies.
The minimum decay time of 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />
[168 hours at Cook] prior to CORE ALTERATIONS ensure that the release of fission product radioactivity, subsequent to a fuel handling accident, results in doses that are well within the guideline values specified in 10 CFR 100.
The acceptance limits for offsite radiation exposure (contained in Standard Review Plan
[SRP]
Section 15.7.4, Rev.
- 1) will be 25% of 10 CFR 100 values or the NRC staff approved licensing basis.
As noted
- above, the basis for the staff position against simultaneous opening of both airlock doors during core alterations is to limit fission product leakage in the event of a fuel handling accident.
In performing analyses of the radiological consequences of a fuel handling accident, the containment isolation criteria of SRP Section 15.7.4 are used.
If fuel handling is prohibited when the containment is open, radiological consequences need not be calculated.
If the containment will be open during fuel handling operations, automatic isolation by radiation detection instrumentation must be provided for penetrations, and calculations must demonstrate acceptable consequences.
However, automatic isolation of airlock doors is not practicable.
Thus, the iSTS specify that airlock integrity be maintained during fuel handling in containment.
However, the licensee has shown by analysis comparison that the D.C. Cook licensing basis is not changed by the proposed amendments.
The licensee reviewed the dose consequences of a fuel handling accident as documented in the Updated Final Safety Analysis Report (UFSAR).
The design basis accident is the complete rupture of the highest rated spent fuel assembly.
The fuel handling accident inside containment was considered to provide the bounding conditions.
This was based on the fact that no reduction in the potential thyroid dose was assumed since charcoal filtration was not considered and no credit was taken for containment isolation.
In addition the analyzed case was assumed to occur 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> after shutdown although Cook TSs require 168 hours0.00194 days <br />0.0467 hours <br />2.777778e-4 weeks <br />6.3924e-5 months <br /> before fuel handling.
The accident inside containment gave a 0-2 hour site boundary thyroid dose of 82.3
These values, both of which are below the 300-rem thyroid and 25-rem whole-body limits established in 10 CFR Part 100, established the design basis for the plant.
The proposed changes do not adversely affect the assumptions in the UFSAR accident analysis.
3.0
SUMMARY
The licensee's analysis of radiological consequences of a fuel handling accident with the containment personnel airlock open confirms that design basis dose acceptance criteria for the analyzed fuel handling accident are met.
Also, standard controls are in place to ensure that the potential for
- other, more severe events which could occur during outages, such as reactivity increases or a heavy load drop on irradiated fuel, need not be postulated and analyzed.
Accordingly, based on the details discussed in Section 2.0, the staff finds that the requested revisions to the D.C.
Cook Nuclear Power Plant Units Nos.
1 and 2, TSs are acceptable
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Michigan State official was notified of the proposed issuance of the amendments'he State official had no comments.
- 5. 0 ENVIRONMENTAL CONSIDERATION The amendments change the requirements with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The 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 (60 FR 29879).
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51 '2(b),
no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments'.
0 CONCLUSION The staff 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 Contributors:
W. Long (by precedent)
J.
Lee (by precedent)
J.
Hickman Date:
JUly 12, 1995