ML20057D744
| ML20057D744 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/29/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20057D739 | List: |
| References | |
| NUDOCS 9310050291 | |
| Download: ML20057D744 (3) | |
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NUCLEAR REGULATORY COMMISSION WASHINGTON. D C. 20 % 5 0001 K..... J' SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 64 TO FACILITY OPERATING LICENSE NO. DPR-21 NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION. UNIT 1 DOCKET NO. 50-245
1.0 INTRODUCTION
By letter dated May 25, 1993, the Northeast Nuclear Energy Company (NNECO) submitted a request for changes to the Millstone Nuclear Power Station, Unit 1 Technical Specifications (TS). The requested change removes the operability and associated surveillance requirements for the main steam line radiation monitor (MSLRM) scram and Group I containment isolation functions. NNECO referenced Licensing Topical Report NED0-31400, " Safety Evaluation For Eliminating the Boiling Water Reactor Main Steam Line Isolation Valve Closure Function and Scram Function of the Main Steam Line Radiation Monitor," which was approved by the NRC staff on May 15, 1991, as justification for removal of the MSLRM trip functions.
The amendment also moves the requirements for MSLRH calibration to Surveillance Requirement 4.6.K.2 and makes some editorial changes to Limiting Condition for Operation Section 3.6.K.l.
2.0 EVALUATION NNEC0 referenced General Electric (GE) Topical Report NED0-31400 in support of its request to eliminate the MSLRM scram and group isolation functions.
In the topical report, GE analyzes a control rod drop accident where the main steam line high radiation isolation is eliminated.
The resulting radiological exposures are small fractions of 10 CFR Part 100 limits.
In the NRC safety evaluation dated May 15, 1991, the staff stated that participating boiling water reactor utilities, listed in Table 1 of the Topical Report, may reference NED0-31400 in support of their license amendment application if they meet the following criteria:
1.
The licensee must demonstrate that the assumptions with regard to input values (including power per assembly, Chi /Q, and decay times) that are made in the generic analysis bound those for the plant.
2.
The licensee must provide reasonable assurance that increased levels of radioactivity in the main steam lines will be controlled expeditiously to limit both occupational doses and environmental releases; and,
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The MSLRM and offgas radiation monitor alarm setpoints must be set at 1.5 times the nominal background including N-16 at the monitor locations and the licensee must promptly sample the reactor coolant to determine possible contamination levels if the setpoint of either monitor is exceeded.
NNEC0 has demonstrated that the assumptions with regard to input values that are made in the generic analysis bound those for the plant, with the exception of the number of failed rods. The power per assembly, Chi /Q, and decay time assumptions used in the NED0-31400 analysis are all conservative with respect to the Millstone 1 analysis. The number of failed rods differs from 880 in the Millstone analysis to 850 in NED0-31400, a ratio of 1.04.
This non-conservatism in the NEDO analysis is offset, however, by conservatism in a fuel inventory based on a thermal power multiplier of 1.05 for the NED0-31400 analysis and only 1.00 for the Millstone 1 analysis, and a power per rod of 0.08 MWt in the Millstone analysis as compared to 0.12 MWt in the NED0-31400 analysis.
With regard to the second and third criteria, NNECO indicated that procedural changes are planned to require operator response upon receipt of MSLRM alarms, which will be set at 1.5 times normal full power background. The procedure will require the operator to initiate sampling of reactor coolant and, as a precaution, observe the steam jet air ejector (SJAE) monitor readings for at least 15 minutes.
If the SJAE monitor Hi-Hi alarm is received, the operator will scram the reactor and close the main steam isolation valves. Although the delay of the response of the SJAE monitor could allow up to a 5 minute puff of offgas into the offgas system, the shortest transit time to the environment is approximately 50 minutes, approximately 10 times greater than the 5 minutes representing the leading edge of the puff.
Therefore, the puff will remain trapped in the offgas system after the reactor scram. This hold-up time will allow the radionuclides to decay and limit the occupational and environmental releases.
The Millstone 1 design incorporates a hold-up to allow short-lived activation gases to decay prior to reaching the SJAE monitor.
The SJAE monitor is designed to detect extremely small fuel failures. NNEC0 has indicated that because the SJAE monitor is in a low-dose background area, adjusting the setpoint to 1.5 times the nominal reading would correspond to a fission gas release rate of only.0005 Ci/sec. NNECO has stated that at this level corrective action is not warranted. The NRC has recognized that certain plants may have configur&tions warranting different setpoints.
In Section 7 of NED0-31400, the assumption was made that a change in the noble gas release rate, in the range of 1-10 Ci/sec, would be promptly alarmed at the SJAE.
NNEC0 stated in their submittal that the SJAE monitor at Hillstone I would 4
have a maximum Hi-Hi alarm setpoint, per TS, of 1.47 Ci/sec.
It is NNEC0's position that at this setpoint, they would have confidence that the operator could take additional corrective actions to assure that the assumption made in Section 7 was not negated. This confidence stems from the fact that NNECO currently has TS and procedural responses for a SJAE Hi-Hi alarm. These responses include the initiation of automatic isolation of the offgas system
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on a 15 minute delay timer to meet TS instantaneous release limits. Since NNECO has demonstrated a technical basis for setting the alarm at a different setpoint and has procedural responses in place for such an alarm, the NRC finds the SJAE setpoint of 1.47 Ci/sec sufficient to provide early indication of a potential environmental release due to fuel failure.
Based upon implementation of the revised procedures described in NNEC0's submittal, the staff finds that the requirenents of the NRC's generic safety evaluation on NED0-31400 are satisfied for Millstone Unit 1.
Therefore, the NRC staff finds the proposed revisions to the Millstone Unit 1 TS acceptable based on the above evaluation.
1 3.0 STATE CONSULTATIQN In accordance with the Commission's regulations, the Connecticut State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
j The amendment changes 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 changes surveillance requirements. The NRC staff has determined that the amendment involves 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 i
occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (58 FR 36441). Accordingly, the amendment meets 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 amendment.
5.0 CONCLUSION
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 amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
B. Korona l
Date:
September 29, 1993
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