ML20246K161

Revised SER Supporting Amends 112 & 108 to Licenses DPR-29 & DPR-30,respectively,changing Setpoints of Main Steam Line Radiation Monitors & Correcting Typos in Tech Specs

ML20246K161
Person / Time
Site:	Quad Cities
Issue date:	08/24/1989
From:	Office of Nuclear Reactor Regulation
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ML20246K138	List: ML20246K134 ML20246K161
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NUDOCS 8909050393
Download: ML20246K161 (5)

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SAFETY EVALUATION BY THE'0FFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 112 TO FACILITY OPERATING LICENSE NO. DPR-29 AND AMENDMENT NO. 108 TO FACILITY OPERATING LICENSE NO. DPR-30 l

COMMONWEALTH EDISON' COMPANY AND l

IOWA-ILLIN0IS GAS AND ELECTRIC COMPANY QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-254 AND 50-265

1.0 INTRODUCTION

By letters dated September 16 and November the licensee requested an amendment to Quad Cities Station 18,(1988, Units 1 and 2) Operating

' Licenses DPR-29 and DPR-30 to change the setpoint of main steam line radiationmonitors(MSLRMS)andcorrecttypographicalerrorsinthe

-Technical Specifications. The requested change involves increasing the setpoint of MSLRMs from seven times Normal Full Power Background (NFPB) to 15 times NFPB (without hydrogen addition) to allow for implementation of Hydrogen Water. Chemistry (HWC) which is expected to mitigate the effectsofIntergranularStressCorrosionCracking(IGSCC). The MSLRM setpoint change is necessary since the injection of hydrogen into the feedwater lowers the oxidizing potential in the reactor coolant which in turn converts more N-16 to a volatile species and results in an

. increase in steam line radiation level. As a consequence, the NFPB sta:am activity during hydrogen addition can increase up to approximately a factor of five times greater than NFPB steam activity without hydrogen addition.

By letters dated September 28, 1988 and May 1, 1989, the licensen provided additional information to support the implementation of HWC. The additional information included:

(1) Report titled, "HWC Installation Report for Amendment to the facility Operating License," dated May 16, 1988.

(2) Report titled, "HWC Installation Compliance with Electric Power Research Institute (EPRI) Guidelines for Permanent BWR Hydrogen Water Chemistry Installations - 1987 Revision."

(3) Draft copy of Proposed Changes to Updated FSAR as a Result of HWC Addition at Quad Cities Station.

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The changes will be included in the June 30, 1989 update to the FSAR.

l 2.0 EVALUATION 2.1 MSLRM Setpoint The MSLRMs provide reactor stram and main steam line isolation signals when high-activity levels are detected in the main steam lines. Addi-tionally, these monitors serve to limit radioactivity releases in the event of fuel failures. Technical Specification (TS) changes are needed to accommodate the expected main steam line radiation levels (for increased N-16 activity levels in the steam phase) as a result of hydrogen injection into the reactor coolant system.

The licensee has requested TS changes to raise MSLRM set points from the current seven times NFPB to fif teen times NFPB (without hydrogen addition). The licensee proposes a single set point for the MSLRMs which is an exception to the EPRI " Guidelines for Permanent BWR Hydrogen Water Chemistry Installations - 1987 Revision" (hereafter referred to as the Guidelines). The Guidelines recommended a dual MSLRM set point: (1) For reactor power less than 20% of rated, when hydrogen should not be injected, the setpoint is maintained at the current TS factor above NFPB, and (2) For reactor power greater than 20% of rated, the set point is readjusted to the same TS factor above NFPB with hydrogen addition.

The only design basis event in which the Quad Cities Station takes credit for th? MSLRM is the Control Rod Drop Accident (CRDA). In the event of a CRDA, the MSLRMs detect high radiation levels in the main steam lines and provide signals for reactor scram and Main Steam Line Isolation Valve (MSIV) closure to reduce the release of fission products to the environment. For the proposed MSLRM set point of fifteen times NFPB (without hydrogen addition), the calculated dose rate at the MSLRM is 1.5 R/hr. For a CRDA, the dose rate at the MSLRM is 8R/hr. Since the MSLRM dose rate from the CRDA is over five times the proposed increased MSLRM set point, the high radiation signal caused by the CRDA will still scram the reactor and isolate the MSIVs.

Raising the MSLRM trip set point from the current 0.7 R/hr to 1.5 R/hr will not result in a significant increase in the radiological consequences of a CRDA. The time to reach the proposed MSLRM trip set point following a CRDA will be increased by less than 1/4 second. The Quad Cities TS permits five seconds for MSIV closure. The incre se in time-to-closure due to the proposed MSLRM set point is only 5% of the current time-to-closure. Since the calculated dose from the CRDA is only 12 mrem, the minor increase in MSIV isolation will have an insignificant effect on the total activity release and resulting dose to the general public.

In the event of an incident causing minor fuel damage such that radiation levels will not exceed the proposed MSLRM set point of fifteen times NFPB (without hydrogen addition), the downstream steam jet air ejectors radiation detectors would be alarmed. These detectors have a greater sensitivity thantheMSLRMsfornoblegasesbecauseoftheholdupperiod(delay

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betweenMSLRMandsteamjetairejectorradiationdetectors)whichallows for significant decay of H-16 (7.1 second half-life). Since steam jet air ejector radiation detectors are in the Quad Cities (Units 1 and 2) TS, the proposed MSLRM set point change will not result in offsite doses in excess of established release limits.

On the basis of the above evaluation, we find that the proposed Technical Specification changes required for implementation of HWC at Quad Cities Station (Units 1 and 2) are acceptable. The proposed increased single set point, versus a dual power dependent set point, for the MSLRMs is an exception to the BWR Owners Group, " Guidelines for Permanent Hydrogen Water Chemistry Installations - 1987 Revision." This exception is justified on the basis that the CRDA dose rate is already limiting at five times the new set point. Thus, it will not affect the safety of the plant or the general'public.

2.2 Radiation Protection The staff has reviewed the licensee's submittal regarding the radiological implications due to the increased dose rate associated with increased N-16 activity levels during hydrogen injections into the reactor system. The licensee is committed to designing, installing, operating, and maintaining the HWC System in accordance with Regulatory Guides 8.8 and 8.10 to assure that occupational radiation exposures and doses to the general public will be As Low As Reasonably Achievable (ALARA). A preliminary radiological study has been completed at the Quad Cities Station to identify areas of the station which may experience increased dose rates due to HWC. When HWC is implemented, the results of the preliminary study will be confirmed and additional measurements will be made, if required. Based on the preliminary HWC study)and in March experience 1983 , additional from appears shielding the Dresden to be Unit 2 (implemented unnecessary. Again, when HWC is implemented, these results will be confirmed and additional shielding will be provided, if required.

Plant procedures will aadress access control of radiation arens that are affected by HWC. Guidelines will be established for any additional controls needed for area posting and monitoring due to HWC. The existing radio-logical surveillance program (Section 8.4 of Offsite Dose Calculational Manual) assures compliance with regulatory requirements for offsite doses to the public. The licensee developed a temporary procedure for an extensive environmental monitoring program with an additional 70 TLDs. The program appears acceptable in determining radiation level increases from N-16 due to HWC.

Electrochemical Potential (ECP) measurements will be made to assure IGSCC protection as well as optimizing hydrogen injection rates to minimize radiation levels. Radiation protection practices implemented for HWC will ensure ALARA in accordance with Regulatory Guide 8.8 and are, there-fore, acceptable.

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2.3 Hydrogen an.10xygen Storage Facilities The hydrogen storage facility contains a liquid hydrogen tank, gaseous storage tubes, and two gaseous tube trailer discharge stations. The licensee will utilize a 20,000 gallon liquid hydrogen tank as a long term hydrogen source. Gaseous hydrogen storage tubes (total capacity 50,000 - 75 000 scf, each tube capacity 8,300 scf, maximum pressure 2,400 psig),are provided to serve as a gaseous surge volume for the liquid hydrogen tank. If the liquid hydrogen system is not completed, the licensee will utilize two gaseous hydrogen tube trailers for initial startup and operation. Gaseous tube trailers will also be brought onsite to provide backup hydrogen supply when liquid hydrogen is not available.

The pressure control station has two parallel full flow pressure reducing regulators. An excess flow check valve is installed downstream of the interim tube trailer and long-term liquid hydrogen storage facility. An additional excess flow check valve is installed in the hydrogen gas supply ifne near the west wall of the Unit 1 turbine building. Each excess flow check valve has a stop-flow-setpoint of 200 scfm (plant's hydrog'en flow requirements are 140 scfm).

The liquid hydrogen tank is constructed in accordance with Section VIII, Division 1 of the ASME Code for Unfired Pressure Vessels. The hydrogen storage facility (compressed gas and liquid) is located 1500 feet from the nearest safety-related structure. This distance meets the Guidelines which require 140 and 962 feet separation distance in the event of an explosion of a gaseous hydrogen storage tube and liquid hydrogen tank, respectively.

The hydrogen supply facility provides the gaseous hydrogen requirements for turbine generator cooling / purging as well as HWC for Units 1 and 2.

The liquid oxygen storage tank, with a maximum capacity of 11,000 gallons, is located 1000 feet away from the nearest safety-related air intake.

The hydrogen and oxygen storage facilities meet the Guidelines.

2.4 Hydrogen and Oxygen Injection System Hydrogen )iping is run underground from the storage facility to the outer wall of t,e Unit 1 turbine building. This piping is covered with a protective coating to protect against corrosion and is electrically grounded. The hydrogen injection lines for each unit are equipped with check valves and solenoid isolation valves which are interlocked with the condensate pump. Individual solenoid isolation valves provide hydrogen flow isolation if the associated condensate pump is shut down and for all hydrogen injection trips. Hydrogen is injected into the condensate pump discharge (at a rate of 70 SCFM at full power) to provide adequate dissolving and mixing and to avoid gas pockets at high points. The hydro-gen injection rate is automatically programmed as a function of main steam flow. Hydrogen injection is automatically tripped on main steam flow of less than 20%.

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The HWC system is tripped by the following signals:

Reactor scram, Low residual off-gas oxygen concentration, High hydrogen flow, Low hydrogen flow, Area hydrogen concentrator. high, Operator manual, Hydrogen storage facility trouble, and Low reactor steam flow Each unit has eight hydrogen area monitors located in the vicinity of hydrogen injection system components that may leak. The sensors feed to a monitor panel which trips the respective unit's HWC system at 20% of the lower explosive limit.

Oxygen is injected into the off-gas system to insure that all excess hydrogen in the off-gas stream is recombined. At the present time, oxygen is not piping into the condensate system to maintain recomended dissolved oxygen concentrations of 20-60 ppb for feedwater pipe corrosion control.

Should oxygen concentrations decrease below 20 ppb when HWC is implemented, the licensee comitted to provide for oxygen addition into the condensate system.

The hydrogen and oxygen injection system meet the Guidelines.

3.0 ENVIRONMENTAL CONSIDERATION

These amendments involve a change to a requirement 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 these 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 Comission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public comment on such findings. Accordingly, these amendments meet the eligibility criteria forcategoricalexclusionsetforthin10CFR51.22(c)(9)and10CFR 51.22(c)(10). Pursuant to 10 CFR 51.22(b) no environmental impact statement nor environmental assessment need be prepared in connection with the issuance of these amendments.

4.0 CONCLUSION

The staff has concluded, based on the considerations discussed above, that:

(1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, endsuch (2) public activities will be conducted in compliance with tne Comission's regulations

, and the 4suance of these amendments will r.ot be inimical to the common defense and security nor to the health and safety of the public.

l i Principal Contributor: Frank Witt Dated: August 24, 1939 L_- _