ML20070B348
| ML20070B348 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 06/21/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20070B338 | List: |
| References | |
| NUDOCS 9406300067 | |
| Download: ML20070B348 (6) | |
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g UNITED STATES
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3 NUCLEAR REGULATORY COMMISSION
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j WASHINGTON, D.C. 2055fHX)01 l
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 154 TO FACILITY OPERATING LICENSE NO. OPR-35 1
j BOSTON EDISON COMPANY PILGRIM NUCLEAR POWER STATION DOCKET N0. 50-293 i
1.0 INTRODUCTION
i By letter dated October 19, 1993, the Boston Edison Company (the licensee or BECo) submitted a request for changes to the Pilgrim Nuclear Power Station Technical Specifications (TSs).
The requested changes remove the scram and Group I isolation valve closure functions with the main steam line radiation monitors (MSLRM).
4 By letter dated October 19, 1993, the BEco proposed changes to the Pilgrim Nuclear Power Station (PNPS) Appendix A of Operating License No. DPR-35 in accordance with 10 CFR 50.90.
The proposed changes will revise TSs to eliminate the main steamline radiation signal from the reactor scram and from i
the main steamline isolation valve (MSIV) closure.
The changes will also i
remove the Group 1 isolation of the main steamline drain (MSLO) lines and the reactor coolant system (RCS) lines.
These proposed TS changes will reduce scram frequency, maintain the availability of the condenser for scram recovery, and maintain / increase operator control over radioactive releases (Ref. 1).
On December 20, 1992, PNPS experienced a reactor scram and MSIV closure, with q
the plant at 75% power, when the setpoint trip of the MSLRM was exceeded.
The j
root cause of this MSLRM trip was determined to be improper setting of the j
trip setpoint. (Ref. 2)
2.0 BACKGROUND
The MSLRMs detectors provide an early indication of gross fuel failure. When high radiation (3 times normal) is detected, a reactor scram is 'nitiated to reduce possible continued failure of fuel cladding. This same h:gh radiation condition also signals the primary containment isolation system (PCIS) to initiate containment isolation of the released fission products.
The MSIVs are part of the PCIS and are also signaled to close when high radiation is detected by the MSLRMs.
The reactor scram and PCIS trip setting is high enough above background radiation levels to prevent spurious trips, yet low enough to promptly detect gross failure in the fuel cladding.
The MSLRM alarm setpoint is 1.5 times background based on normal full power background radiation levels.
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' 3.0 EVALUATION BECo proposed a revision to the PNPS TS Sections 3.1/4.1, 3.2/4.2, and 3.7/4.7 to eliminate the main steamline radiation signal from the reactor scram, MSIV closure and Group 1 isolation of the MSLD lines and the RCS lines.
The MSLRM initiated alarms and the mechanical vacuum pump trip signals will remain functional (Ref.1).
These changes are in accordance with the General Electric Topical Report NED0-31400, " Safety Evaluation for Eliminating the Boiling Water Reactor Main Steamline Radiation Monitor," dated May 1987 prepared for the Boiling Water Reactor Owners Group (BWROG).
The purpose of the topical report was to demonstrate that the vessel isolation function and scram function of the MSLRM are not required to ensure compliance with the radiation dose guidelines of 10 CFR Part 100.
In addition, it demonstrates that use of the offgas treatment system provides significant holdup times for radionuclides and is an acceptable method of controlling unexpected radioactivity releases.
This report concluded that elimination of the MSIV closure function and scram function of the MSLRM, in conjunction with proper use of an Augmented Offgas (A0G) system, results in offsite radiological exposures that are small fractions of 10 CFR Part 100 guidelines, even when utilizing very conservative source terms. The GE COMPASS scram data base starting in 1980 (a total of 162 plant operating years) identified eight inadvertent scrams that can be attributed to the MSLRM (Ref. 3).
The NRC staff reviewed NED0-31400 and requested additional information in a letter dated September 6, 1988 (Ref. 4).
Responses were received from the BWROG in letters dated April 4, 1989 (Ref. 5), August 24, 1989 (Ref. 6),
October 30, 1989 (Ref. 7), and April 19, 1990 (Ref. 8).
The NRC Safety Evaluation Report (SER) dated May 15, 1991, accepted NED0-31400 for use as reference in the licensee TS amendment applications, and in 4
accordance with procedures established in NUREG-0390, the BWR0G published accepted versions of the topical report as NED0-31400A.
The SER stated that participating BWR licensees may reference the topical report in their license amendment application provided the following conditions were satisfied (Ref. 9):
1.
The applicant / licensee demonstrates the assumptions with regard to input
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values (including power per assembly, Chi /Q, and decay times) that are made in the generic analysis bound those for the plant.
2.
The applicant / licensee includes sufficient evidence (which could be implemented or proposed operating procedure or equivalent commitments) to provide reasonable assurance that significantly increased levels of radioactivity in the main steamlines would be controlled expeditiously to limit both occupational doses and environmental releases.
_3-3.
The applicant / licensee standardizes the MSLRM and offgas radiation monitor l
alarm setpoint to 1.5 times the normal N-16 background dose rate at the monitor locations and commits to promptly sample the reactor coolant to datermine possible contamination levels and the need for additional corrective actions, if the MSLRM or offgas radiation monitors or both exceed their alarm setpoints.
The-PNPS licensee responded to the above conditions as follows:
RI. The licensee provided the results of a comparison of the key analysis input values between NED0 31400A for the control rod drop accident (CRDA) and a site-specific analysis, PNPS-1-ERHS-XIII.T-49-0, which demonstrated that plant-specific offsite doses for a CRDA are bounded by the values in NED0-31400A.
The NED0-31400A analysis considered two cases:
- 1) A CRDA where the source term is not reduced, even though the MSIV's close, and the radionuclides enter the condenser at atmospheric pressure to leak at a rate of 1% volume / day.
- 2) A CRDA where the MSIV's do not close and the activity is processed through the A0G system and released to the environment through the main stack.
4 The comparison of thyroid and whole body dosos between the NED0 and PNPS analysis indicates the PNPS doses were less than the NED0 dose values; therefore, the NEDO analysis bounded the plant-specific analysis.
R2. The licensee stated, "The MSL Hi Rad Scram will be changed to a Hi Hi Rad Alarm which will provide an additional alarm to alert personnel of increasing activity in the steam tunnel. This alarm setpoint is the same value that trips the mechanical vacuum pump.
In addition to the existing procedures that address increased coolant activity, a new off-normal condition procedure for abnormal transients has been developed to include operator actions for assessing and controlling increased activity in the mainsteam, reactor sample and offgas systems. The present alarm response procedures for high radiation in the offgas and mainsteam system will be revised to reference the new procedure." The staff requested the licensee to provide a copy of the new procedure and applicable portions of the existing and revised procedures that the operator would use for assessing and manually controlling increased radioactivity after a CRDA. On March 8, 1994, the licensee submitted Procedure No. 2.4.40 that the staff requested (Ref. 10).
The staff finds that the above procedure provides the operator sufficient guidance to manually control radioactivity in the main steam system, main steamline drain system, reactor coolant sample system, and the A0G system.
in addition, this procedure makes reference to existing procedures that address increases in reactor coolant activity.
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R3. The MSLRM will be set to alarm at 1.5 times normal full-power background.
l The MSLRM trip of the mechanical vacuum pump will remain; however, the i
automatic closure of the MSLD line valves and the RCS valves is eliminated.
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The removal of the MSLRM Group 1 isolation of the MSLD lines and the RCS lines is not addressed in NED0-31400A; however, it is addressed in the licensee's amendment request (Ref. 1).
The licensee's justificatic Nr removal of the MSLD line closure from a MSLRM trip is based on a
" nation that the radiological consequences i
are bounded by the NED0-31% , valuation. There is no effect on the resulting offsite dose with the MSLD line valves remaining open during a CRDA since the piping is routed to the condenser. The source term in the j
condenser is unaffected because no plate-out or condensation of the source term from the reactor to the condenser is assumed in the NED0-31400A i
analysis.
l The licensee's justification for remmi the RCS valve closure from a i
MSLRM trip is based on a determination that the calculated offsite dose is less than the Standard Review Plan (SRP) limits. This offsite dose assessment was made using conservative assumptions including the assumption that the operator would manually isolate the RCS lines within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> after the CRDA occurs.
As stated in R1 above, the licensee performed a site-specific analysis, l
PNPS-1-ERHS-XIII.T-49-0, which demon ' mtes that offsite doses for a CRDA i
are bounded by the values in NED0,
Also, because of the variety of trip functions from the participating utilities, the NED0-31400A safety evaluation did not include an offsite dose impact of other possible trip functions of the main steam line radiation monitors. The other site specific main steam radiation monitoring trip functions analyzed by the licensee are as follows:
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1.
Mechanical vacuum pump trip.
2.
Close the main steamline drain isolation valves.
l 3.
Close the reactor sample isolation valves.
l In addition to the above, the licensee identified the turbine gland seal condenser exhausters as another contributor to offsite doses during a
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CRDA.
j The resulting offsite doses from all the PNPS analyzed conditions were compared to the offsite doses in NED0-31400A and SRP 15.4.9.
The results show the whole body dose of 0.09 rem for PNPS to be less than the NED0-31400A value of 0.31 rem. The PNPS thyroid dose of 10.7 rem is greater than the NED0-31400A vr.lue of 4.3 because of the PNPS site specific added contributions. However, the total offsite dose for a CRDA l
at PNPS is less than the SRP limits of 75 rem thyroid and 6 rem whole i
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body.
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4.0 REFERENCES
1.
Letter from E.T. Boulette, Senior Vice President BECo, to NRC " Proposed Change to Technical Specifications to Remove the Main Steamline Radiation Monitor Scram and Isolation Functions."
l 2.
License Event Report 92-018-00, Event date 12/20/92, " Reactor Scram and Main Steamlina Isolation Valves closure from Main Steamline Radiation Monitor Trip."
3.
General Electric Topical Report NED0-31400, " Safety Evaluation of Eliminating the Boiling Water Reactor Main Steamline Isolation Valve Closure Function and Scram Function of the Main Steamline Radiation Monitor," May 1987.
Letter From Robert F. Janeck, BWROG, to NRC transmitting NED0-31400, dated July 9, 1987.
4.
Letter from Cunningham, NRC, to D. Grace, BWROG, " Resolution of Outstanding Issues Relative to Topical Report NED0-31400," dated September 6, 1988.
5.
Letter from D. Grace, BWROG, to L. Cunningham, NRC, " Response to NRC Questions on NE00-31400," dated April 4, 1989.
j 6.
Letter from S. Stark, Gr. to L. Cunningham, NRC, Additional Information.
Pertaining to NRC Review of NE00-31400, dated August 24, 1989.
7.
Letter from S. Floyd, BWROG, to L. Cunningham, NRC, Additional Information Pertaining to NRC Review of NED0-31400: Operator Action on MSLRM Alarm,"
dated October 30, 1989.
8.
Letter from S. Floyd, BWROG, to L. Cunningham, NRC, " Response to Action Items from March 22, 1990 NRC/BWROG Meeting," dated April 19, 1990.
9.
Letter from AC Thadani, NRC, to GJ Beck, BWROG, " Acceptance for Referencing of Licensing Topical Report NE00-31400, dated May 15, 1991.
- 10. Pilgrim Nuclear Power Station Procedure No. 2.4.40 " Rapid Increase in Main Steamline or Offgas Activity" Rev.12, originated July 1992, draft dated February 4, 1994.
5.0 STATE CONSULTATION
1.
In accordance with the Commission's regulations, the Massachusetts State Official was notified of the proposed issuance of the amendment.
The State official had no comments.
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6.0 ENVIRONMENTAL CONSIDERATION
f 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. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change.in the types, i
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 amendment involves no significant hazards consideration, and there has been no public comment on such finding (58 FR 62151).
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR i
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 i
the amendment.
7.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, 1
that:
(1) there is reasonable assurance that the health and safety of the l
public will not be endangered by operation in the proposed manner, (2) such 1
activities will be conducted in compliance with the Commission's regulations, j
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.
i Principal Contributors:
F. Paulitz j
S. Klementowicz i
Date:
June 21, 1994 l
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