ML20003D526
| ML20003D526 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 03/23/1981 |
| From: | Utley E CAROLINA POWER & LIGHT CO. |
| To: | Ippolito T Office of Nuclear Reactor Regulation |
| References | |
| NO-81-073, NO-81-73, NUDOCS 8103270609 | |
| Download: ML20003D526 (6) | |
Text
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d March 23, 1981 File: NC-3514(3)
Serial No.: NO-81-073
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Office of Nue'. ear Reactor Regulation ATTENTION:
Mr. T. A. Ippolito, Chief
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Operating Reactors Branch No. 2 k
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United States Nuclear Regulatory Commission g
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Washington, D. C.
20555 (p
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2 l5 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS. 1 AND Y y DOCKET NOS. 50-325 AND 50-324 D
LICENSE NOS. DPR-71 AND DPR-62 g
,i AUGMENTED OFF-GAS SYSTEM
Dear Mr. Ippolito:
SINMARY In a letter dated May 1, 1979, Carolina Power & Light Company (CP&L) advised NRC that we expected to have the Augmented Off-Gas (A0G) system operable on our Brunswick Steam Electric Plant (BSEP), Unit Nos. I and 2 by December 31, 1981. This commitment was based on (1) the installation of hydrogen recombiners on the front end of the off-gas system (i.e. in the steam jet air ejector rooms), and (2) modification of the existing cryogenic distillation system. As discussed below, we now find that installation of a charcoal adsorber system would be technically superior to the modification of the existing cryogenic distillation system. The following describes the background for our decision, the scope of our revised plans, our schedule fo.-
completing the modifications and the basis for continued operations.
BACKGROUND CP&L submitted a " Preliminary Technical Description" of the Off-Gas System to NRC in a June 29, 1979 letter, and we had embarked on those activities necessary to design and procure that system. During 1980, as a parallel effort, we further studied the off-gas issue within the industry.
Based on this further evaluation of operating experience, it appeared that our cryogenic distillation system (CDS), when compared to other available technology, would probably experience excessive reliability problems, operation and maintenance difficulties with associated high annual costs, and excessive personnel radiation exposure. An example of the CDS system complexity is given by the quantity of components involved (e.g., more than 270 valves of which over 100 are active control valves, along with more than 180 instruments for each unit).
In addition, some 46 process variables have been identified as having the potential for CDS system shutdown from either a spurious signal or actual off-normal condition.
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8103270609
Mr. Ippolito In mid-1980, we began to investigate the feasibility of replacing the CDS with a new charcoal adsorber system (CAS).
Charcsal adsorber systems are being utilized successfully by 34 of 38 BWRs in the United States.
Subsequently, we re-evaluated the rechnical acceptability of utilizing the existing cryogenic system as compared to the installation of a new charcoal adsorber system. These comparisons indicated that a charcoal adsorption system would be superior to the cryogenic system from the standpoint of reliability and occupational exposure.
The charcoal adsorber system is essentially passive with no moving raits in the gas process.
Although the charcoal system will cost about 2.,5 times more than refurbishment of the existing cryogenic system, the tenefits of reliability and reduced exposure will outweigh the initial cost.
Another major item considered in our evaluation was annual man-rem exposure. To operate and maintain the cryogenic system, we estimate that the annual exposure would be about 350 man-rem, while the charcoal system's exposure estimate for annual operation and maintenance is 8 man-rem.
The additional costs associated with removing the existing cryogenic system and with purchasing and installing the charcoal adsorbers are offset by the reduction of operating, maintenance, and exposure costs.
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SCOPE Installation of off-gas pre-treatment equipment (e.g. hydrogen recombiners, preheaters, condensers, and moisture separator / coolers in the steam jet air ejector rooms) will be accomplished as described in our letter of June 29, 1979. This equipment will pre-condition the effluent stream by eliminating unacceptably high concentrations of hydrogen prior to entering the CAS.
In addition, two (2) 100% capacity, independent charcoal adsorption systems will be installed in the existing A0G building following complete removal of the existing cryogenic distillation system.
The off-gas would leave the existing 30-minute holdup pipe through the present off-gas filters l
in the stack filter house. Cross-tie piping at the filters would be retained to allow use of the standby filter; however, valve interlocks would be provided to prevent cross connecting the two units. Thus, unit independence i
of the off-gas filters would be achieved.
The following process description is based on our present I
preliminary design.
Process off-gas cooling and condensing of water vapor would take place in the shell side of the skid-mounted cooler condenser.
Chilled glycol would be circulated on the tube side by one of two (2) 100%
capacity glycol pumps. The glycol would be cooled by redundant full capacity refrigeration machines. The process 3.s would exit at 40'F and 100% relative humidity. Ambient heating would lower the relative humidity to 40%.
Downstream process gas temperature and dew point would be measured and alarmed. Sufficient reliability will exist, however, to prevent excessive moisture from entering the charcoal adsorber train. The sacrificial charcoal guard bed would provide further moisture protection for the downstream 4
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Mr. Ippolito charcoal adsorbers. The guard bed, with an easily replaceable charcoal basket, would provide efficient iodine removal and would isolate much of the Etigher activity, short-lived species in a small volume which facilitates shielding arrangements.
The main charcoal adsorber vessels would be arranged in parallel trains to minimize system pressure drop. The total mass of charcoal is determined by the design flow, relative humidity, operating temperature and required delay time for Xenon. The preliminary design considers two separate trains of adsorbers (one per unit), each with a loading to support a normal flow of 50 SCFM with at least a 30-day Xenon delay. Final design would be based on a 10CFR50, Appendix I analysis. Each system would still be able to handle up to 150 SCFM at reduced delay times if requiied.
The charcoal adsorber compartments will be maintained at the required temperature by the use of coolers.
After leaving the charcoal adsorber train, the process off-gas passes through a high efficiency HEPA filter and flow element prior to exiting the system to the stack.
Sufficient controls would be provided such that all system operation, including startup, shutdown and switching between redundant equipment, can be accomplished from the control room.
In addition, a local control panel, common to both units, would be installed in the A0G building control area along with a wall-mounted instrument rack where all system parameters can be monitored.
SCHEDULE Attachment i shows our current schedule for completion of the engineering, procurement, and removal and installation of augmented off-gas equipment.
CP&L is now scheduled to have the hydrogen recombiners and the charcoal adsorbers fully operable by May, 1983 on 3runswice Unit 1; this date is based on earliest delivery date for certain CAS equipment.
Installation of the hydrogen recombiners in the Unit 2 SJAE rooms cannot be completed until the 1983 refueling outage. Therefore, the A0G system will be ope able on Unit 2 by December 31 1953.
Performance of the recombiner work during a major refueling and maintenance outage is necessary because new recombiners are planned for installation in the SJAE rooms, upstream of the 30 minute delay line. To do this work on each unit requires that the unit be shutdown for approximately 17 weeks. This recombiner work on Unit 2 will be performed during the refueling outage which is currently scheduled for summer, 1983.
(This outage start date is subject to experienced capacity factors and our grid system reliability, and could change depending on system performance).
In addition to refueling and the recombiner modifications, the Unit 2 condenser will be retubed (which also requires approximately 17 weeks) during this outage. Similar outage planning logic also applies to the Unit I schedule. The removal of the existing hydrogen recombiners and the cryogenic system and. installation of the
Mr. Ippolito charcoal adsorbers on both units can proceed independently of the hydrogen recombiner work, and can be done while the units are in operation.
Sur schedule incorporates not only design and pt ' cure nent time, but also installation requirements for the adsorbers and the retvabiners.
Installation is a major factor, because it must reflect the limitation of construction personnel allowed on site due to health physics constraints,
( ALARA, contamination, etc.), and security and administrative restrictions.
Other critet ta such as peak demand oeriods, fuel charges to our customers, the 10 year in-service inspection requirements on H. B. Robinson Unit 2, refueling requirements at Brunswick 1 and 2 and Robinson 2, and other major plant modifications (torus modifications, condenser recubing) at Brunswick require the schedule presented in Attachment 1 to this letter. We are cognizant of the interest your staff has shown in the past in having the A0G system operable as soon as possible, and we will continue to extend our best efforts to have a reliable A0G System operable as soon as possible.
In view of the staff's continuing interest, we believe it may be appropriate for CP&L to submit a periodic progress report to the NRC documenting our progress relative to the schedule in Attachment 1.
If you prefer, we would also arrange for on-site review by NRC of our progress in this effort. Please advise us if you or your staff wishes to be provided with status information for this A0G modification.
The preceding information in this letter presents many of the complex and interacting factors which we must consider when developing our system outage schedules.
As we have explained earlier, the A0G modification work consists of two major divisions - replacement of the existing cryogenic system with the charcoal adsorbers, and replacement / relocation of the hydrogen recombiners. Both phases are dependent upon plant outage schedules, since the adsorber work must be done between outages, and the recombiner work must be done during an outage of at least 17 weeks length for each unit. The A0G schedule discussed in this letter and presented graphically in Attachment 1 is interminably dependent upon the outage schedules for both units.
As you are aware, outage planning for a utility's system is a dynamic process, because of the fluid nature of many of the factors that go into planning outage schedules. Thus, while we are making our best efforts to meet the A0G operability dates put forth in this letter, parameters such as capacity factors, system reliability and new or evolving regulatory requirements may necessitate c later modification in our outage schedules.
This in turn would impact our A0G modification work. We have attempted to account for some small change in outage schedules, as you will note on Attachment 1.
However, it is essential, in our opinion, that any written requirement establishing an end date for operability contain provisions for modifying the operability dates for good cause shown relative to our outage schedules. Accordingly, I, or any other representative of CP&L, will be available to meet with you and your staff to discuss our outage schedules and how they relate to the accomplishment of the AOC modifications.
BASIS FOR CONTINUED OPERATION Continued operation of the plant will not result in any adverse impact on the public health and safety, owing to the NRC imposed operating
Mr. Ippolito limits for the period prior to the AOG being operable. License A=endments 19 and 43 contain revised technical specifications as requested by NRC to limit the annual gaseous releases from the the Brunswick units to the 10CFR50, Appendix I design objectives during the interim period until the A0G system is '
restored to an operable status. These technical specifications will remain in effect as required by NRC, and CPSL will continue in compliance with them.
In addition, CP&L is responsible for submitting Semiannual Environmental and Effluent Reports to NRC once every six months which have thus far concluded that the Brunswick facility meets the guidelines of 10CFR50, Appendix I and the ALARA numerical standards for releases from the plant stack.
Therefore, CP&L has determined that there will be no adverse impact or the public health and safety during the interim period.
Please contact my staff should you have any questions concerning this matter.
Yours very truly, E.
. Utley I
Executive Vice President Power Supply and Engineering & Construction JAM /dk (N#36)
Attachment 3
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CAROLINA POWER & LIGHT COMPANY E&C MASTER PROJECT SCHEDULE hhk s me.-
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' CunS3T Unit 1 A0G Startup Brunswick Steam Electric Plant i
Unit Nos. 1&2 Unit 1 A0G AUGMENTED OFF-GAS SYSTDi Operable i
MILESTONE EVENTS MODIFICATION SCllEDUI.E linit 2 A0G Startup Unit 2 A0G Ope rable
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ir 1980 1981 1982 1983 MJ J/
SO ND JF MA MJ JA SO ND JF MA MJ JA lSO ND
.1F MA M.I JA SO ND I
Charcoal Adsorption Engr. Design l
Engr. Support l
l t
Procurement of Hajor Equip.
,,g Remove /Constr./ Install l
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Hydrogen Recombiners Engr. Design
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Engr. Support i
l Procurement of Major Equip.
u-a a u-Za Constr./ Install g,
4 Unit 1 l
Unit 2 Refueling / Maintenance 0-1 u-2 putaget A Designates completed it em for not ed unit.
O Installation must be done during refueling outages.
- This work is to be done between Start dates of outages may be adjusted due to outages, and the start /end dateu changes in operational conditions such as overal1 are subject to change should capacity factors. Procurement of major items may outage schedules be revised.
also change as a result of outage changes.
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