ML20195J981
| ML20195J981 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 06/17/1988 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20195J978 | List: |
| References | |
| NUDOCS 8806290302 | |
| Download: ML20195J981 (3) | |
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NUCLEAR REGULATORY COMMISSION WASHINGTON. D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 118 TO FACILITY OPERATING L' CENSE NO. OPR-35 I
BOSTON EDISON COMPANY PILGRIM NUCLEAR POWER STATION DOCKET N0. 50-293
1.0 INTRODUCTION
By letter dated September 9, 1986, Boston Edison Company (BECo) the licensee, submitted a request for change to the Pilgrim Nuclear Power Station Technical Specifications (TS). The requested change modifies the Technical Specifications to accorinodate installation of a hydrogen water chemistry (HWC) system, which is~
intended to mitigate intergranular stress corrosion cracking (IGSCC) of stainless steel piping in the reactor coolant system.
The Pilgrim Technical Specifications will require change because the radiation level adjacent to the main steam lines will increase as a result of the addition of hydrogen to the reactor coolant. The radiation level adjacent to the main steam lines is monitored by instruments whose trip setting is specified in the Tachnical Specifications and will have to be increased.
2.0 EVALUATION 2.1 High Radiation Scram and Isolation Set Points The Main Steam Line Radiation Monitors (MSLRMs) provide reactor ecram as well as reactor vessel and primary containment isolation signals upon detection of high radioactivity in the main steam lines.
Additionally, these monitors serve to limit radioactivity released in the event of fuel failure.
The proposed Technical Specifications would change note (18) to table 3.1.1 anB note (9) to table 3.2. A (Attachment 1) by deleting the word "test" wherever it appears in current Technical Specifications, The change would also allow adjustn.ents to the nonnal background radiation level and associated trip setpoints for the MSLRMs at reactor power levels greater than 20 percent.
The adjustments will be based on either cal-culation or measurement of actual radiation levels resulting from increased N-16 levels in the main steam lines due to hydrogen injection. Within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of re-establishing normal radiation levels after completion of hydrogen in.iection, or prior to withdrawing control rods at reactor power levels below 20 percent rated power, the background radiation level shall be determined and associated trip setpoints shall be reset.
8806290302 080617 3
ADOCK 0500 LR
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F. The licensee states that the only design basis accident that takes credit for the MSLRM trip is the design basis control rod drop accident (CRDA),
Generic analysis of the consecuences of a CRDA have shnwn that fuel failures are not expected from a CRDA occurring at greater than 10 percent power. This is primarily a result of analyses that show that as power increases the severity of the CRDA decreases due to the effects of increased void formation and increased Doppler negative reactivity feedback.
Since hydrogen in,iection will be limited to above 20 percent of rated power and the increased MSLRM trip setpoint will be reduced to normal levels below 20 percent, the staff concludes that the currently approved CRDA analysis for the Pilgrim Nuclear Power Station is appropriately bounded and remains valid.
Therefore, the proposed Technical Specification change is acceptable.
2.2 Radiation Protection The staff has reviewed the proposed Technical Specification change to assure that the licensee has considered the radiological implications of dose rate increases associated with N-16 activity increases due to hydrogen injections into the reactor system.
Extensive plant interior and exterior radiation surveys were conducted during the HWC pre-implementation test, i which was performed during May 1985 at the Pilgrim Station.
At full power ~
with HWC, the MSLRMs increased by a factor of four over the normal BWR chemistry conditions. Additional shielding was installed in the turbine,
building to minimize this effect in the main turbine area.
The increased radiation levels near feedwater heaters and condenser bay have been minimized through installation of shierlding and/or procedural controls., Maintenance activities in high radiation areas resulting from HWC can be accomplished by interrupting or reducing hydrogen injection, since radiation levels will decrease in less than a minute to normal.
An interruption or reduction in HWC for up to about 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> will rot affect the reactor coolant piping protection against IGSCC provided by HWC, Environmental dose rate measurements during the HWC pre-implementation test indicated that at 1100 to 1500 feet from the center of the turbine, the dose rate was not affected. Turbine and turbine building shielding will further reduce environmental dose rates. The permanent HWC system will be operated to ensure ALARA in accordance with Regulatory Guide 8.8 and is, therefore, acceptable.
2.3 Hydrogen Generation and Distribution System The licensee has installed a hydrogen and oxygen injection system to implement permanent HWC at Pilgrim.
The primary hydrogen and oxygen supply is generated on-site by electrolytic cells. As a backup for the electrolytic system, the extended test system will be used. The extended test system consists of a compressed hydrogen gas and liquid oxygen storage facility.
The compressed hydrogen gas storage facility is located 290 feet from the nearest safety related structure (battery room located inside turbine bu 1 ding) and consists of nine high pressure 3
storage tanks having a tot.al capacity of 72,000 standard cubic feet.
The 1500 gallon liquid oxygen tank is located outside the turbine building.
The separation distance between the hydrogen cylinders and safety related structures meets the BWR Owners Group, "Guidelines for Permanent BWR
r y; e
Hydrogen Water Chemistry Installations," 1987 Revision.
The hydrogen injection system contains excess flow check valves to limit the release of hydrogen in the event of a pipe break.
Hydrogen will be injected into the feedwater system at the suction side of the condensate feed pumps.
To prevent the accumulation of combustible levels of hydrogen at the cordensate booster pumps, near the control valves and at various strategic locations along the supply lines, the hydrogen injection system will be leak tested prior to use and will be monitored for hydrogen concentrations during operation. The monitors will alarm when hydrogen concentration exceeds 2 percent and will isolate the hydrogen supply line when the hydrogen concentration reaches 4% to prevent reaching a potentially explosive concentration.
As part of the HWC system, oxygen is injected into the off-gas system to ensure that all excess hydrogen in the off-gas stream is recombined.
Oxygen injection into the suction piping of the condensate pumps is also available to maintain recommended dissolved oxygen concentrations of 20-50 ppb for feedwater piping corrosion control.
2.4 Site Visit The staff visited Pilgrim Station on August 20, 1987 to review the design i and installation of the HWC system.
System diagrams were reviewed and the* '
system was inspected.
The electrolytic and gaseous storage facilities, hydrogen and oxygen injection systems, instrumentation and controls, and safety considerations are consistent with the "Guidelines for Permanent BWR Hydregen Water Chemistry Installations," 1987 Revision.
3.0 ENVIRONMENTAL CONSIDERATION
S This amendment involves a change in 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 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 occupational radiation exposure.
The Commission has previously published a proposed findi..g that the amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 651.22(c)(9). Pursuant to 10 CFR 651.22(b), no environmental impact statement or environmental assessment need he prepared in connection with the issuance of this amendment.
4.0 CONCLUSION
We have concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety tf the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regulations, and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
F. Witt i
Pated: June 17, 1988
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