ML20082C361
| ML20082C361 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 03/31/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20082C359 | List: |
| References | |
| NUDOCS 9504060313 | |
| Download: ML20082C361 (5) | |
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UNITED STATES 7m y
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NUCLEAR REGULATORY COMMISSION
(.....f.t' WASHINGTON, D.C, 20006 0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION-
~ RELATED TO AMENDMENT NJ. 97 TO FACILITY OPERATING LICENSE N3. NPF-30 UNION ELECTRIC COMPANY CALLAWAY PLANT. UNIT 1.
DOCKET NO. 50-483 I
1.0 INTRODUCTICN By letter dated September 8,1994, Union Electric Company (UE),.the licensee, requested an amendment to Operating License NPF-30, which would
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revise the Callaway Plant Technical Specifications (TS) Bases Section 3/4.9.1 and Final Safety Analysis Report (FSAR) procedures which deal with boron dilution during refueling. Currently FSAR section 15.4.6.2 states that administrative controls and locking dilution source manual valves preclude an inadvertent dilution of the boron concentration of the primary system. A revision to this FSAR section and the TS Bases will be made '
since changes are required to procedural controls as-described in the'FSAR associated with the use of reactor makeup water to rinse items removed from the refueling pool and to spray down the refueling pool walls during pool drain.
This amendment application involves an unreviewed safety question identified by the licensee. Callaway uses reactor makeup water to rinse items removed from the refuelfug pool.
Reactor makeup water is also used to spray down the refueling pool walls while the fuel pool.is being drained.
The problem with these practices is that the current FSAR states that the closing and locking of dilution source manual valves and current.
administrative controls preclude the potential for an uncontrolled boron dilution of the primary system. However, the existing administrative controls do not consider the use of reactor makeup water as described above, as a potential dilution source. Therefore, without additional administrative controls, an uncontrolled dilution of the primary system could result from using reactor makeup water to facilitate the decontam-ination process. TS LC0 3.9.1 limits boron concentration during refueling to 2000 ppm.
Since the current FSAR does not-consider this dilution path, an unreviewed safety question exists.
To resolve the unreviewed safety question, the licensee submitted a revision to Bases 3/4.9.1 - Boron Concentration and necessary changes to FSAR section 9.1.3.2.3.2 (Fuel Pool Cleanup System) and to the Dilution During Refueling (Mode 6) part of.FSAR section 15.4.6.2 (Analysis of Effects and Consequences). The staff's i
review considers these proposed changes and procedural revisions which address preventing a sizable layer of diluted water from entering the primary system.
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2.0 BACKGROUND
During the' initial refueling of Callaway an inadvertent dilution of the primary system occured during Mode 6.
This dilution was caused by the use of unborated reactor makeup water to spray down the pool walls while simultaneously draining the refueling pool via the Residual Heat Removal system (RHR) flow path to the Reactor Water Storage Tank (RWST). As a result of its review of this incident, the licensee established aiministrative controls to limit the amount of unborated water added to tw refueling pool during the rinsing of items removed from the pool.
Retueling pool washdowns while simultaneously draining the pool were not a
performed at Callaway during refuels 2-5..
x' During' Refuel 5, in April 1992, the licensee experienced a problem with 9
airborne radioactivity,'which resulted in some personnel contaminations Ji and a work stoppage. This occurrance was attributed to an increase in
,T airborne radioactivity levels from the use of a strippable decontamination "di coating, which was sprayed on the refueling pool walls.and floor.
It is j'
believed, that as a result of the walls and floor being dry, loose surface contamination became airborne and caused the radioactivity levels to q% l increase. After this event, the licensee determined that the then.
existing administrative controls which prevented rinsing of the refueling dN; pool walls should be revised.
Therefore, Callaway administrative controls were revised to allow the rinsing of refueling pool walls during the-draining in order to facilit;'e the removal of the stripable coating and' 3
to avoid increasing airborne radioactivity. This revision included 4
performing calculations to ensure that the amount of unborated water added i
would not lower the refueling pool boron concentration below 2000 ppm as required by Technical Specification LC0 3.9.1.
Conservatism was added to this calculation by assuming that the rinse water was added to the RCS Ml volume at mid-loop, neglecting the rest of the volume of the refueling
.;i pool. This practice was initiated during the Refuel 6 at Callaway.
Unborated water was used to decontaminate items removed from the refueling Q
pool and to rinse the refueling pool walls while simultaneously draining the pool to the RWST.
Control of the amount of unborated water was 3
maintained by the use of 3/4 inch line which was equipped with a flow totalizer.
1 After Refuel 6 (September 1994), UE Quality Assurance personnel raised
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concerns that these refuel pool washdown and decontamination practices
.4 constituted an unreviewed safety question.
It was determined that a dilution path different than any discussed in FSAR Section 15.4.6.2. had j
been created.
Based on internal review, the licensee determined that a y
ravision.to its FSAR and TS Bases was necessary and submitted the subject-amendment application pursuant to 10 CFR 50.59(c)(2).
3.0 EVALUATIM 3'
The first change proposed by the licensee was to revise the Bases 3/4.9.1, y*
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" Boron Concentration."
The current Bases state that the locking-closed of required valves precludes the possibility of an uncontrolled boron dilution.
Since these valves do not preclude an uncontrolled dilution j
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3 from reactor makeup water, the licensee-revised'this Bases to state that locking-closed of the required valves prevents _all automatic paths from sources of unborated-water.
In addition, it is stated that administrative controls will be used to limit the volume of unborated water which can be added to the refueling pool for decontamination activities in order to 4
v prevent diluting the refueling pool below the limits specified in the LCO.-
We have reviewed the change made to Bases 3/4.9.~1, as proposed by the.
licensee,andfindthatitaccuratelyachievesthelicensee'sobjectives,j o
as described above, and is acceptable to the staff.
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lx The next major area of-staff review concerns changes made by the lice.nsee to the Callaway FSAR. A number of changes where made to section- _
'f' 9.1.3.2.3.2 (Fuel Pool Cleanup System). These changes are descriptive in y nature and are intended to specifically identify that items removed fromW the refueling pool are sprayed-down using reactor. makeup water and that -
this is performed to facilitate the decontamination of those items.
Statements were also added to recognize that administrative controls have 2gy' '
i been established to prevent diluting the. pool below acceptable boron concentration limits. Revisions of particular importance were made to
.i FSAR section 15.4.6.2 (Analysis of Effects and Consequences). These revisions make it clear that inadvertent boron dilution events resulting
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from automatic flow paths are precluded by valve closure and'that administrative controls will limit the volume of unborated water which can Yt be added to the refueling pool for decontamination activities. The staff 4
reviewed all of these changes.
We found these changes to be consistent 4
with those changes made to the Bases as previously described, and we 1*
believe that these changes accurately reflect Callaway Plant procedures as described in the licensee's submittal.
Therefore, the FSAR changes as proposed by the licensee are acceptable to the staff.
Another major area of staff review concerns the potential for a diluted layer of water entering the primary system.
The licensee states that this problem will be minimized by using the following procedures during refueling:
1.
The water level will be drained to approximately one foot above the reactor cavity seal / shield ring.
The refueling pool will then be drained via the reactor coolant drain tank (RCDT)-
pumps or other available means (excluding the RHR system),,
until the level is below the cavity seal / shield ring. This 4
will direct the potentially diluted layer of water at the top of the pool away from the reactor vessel and core.
2.
After the level has been lowered to below the cavity seal / shield ring, further draining of the area enclosed by the inside diameter of the ring will be performed via the RHR connection to the CVCS letdown.
s The staff has reviewed these procedures and based on our knowledge and review of the Callaway Plant, we find that they will indeed preclude the possibility for a diluted layer of water from reaching the reactor core.
L Therefore, the procedures are acceptable to the staff.
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, The initial review by the staff resulted in two open issues.
1.
The submittal 'did not provide a detailed description or.
diagram of exactly where the reactor makeup water was being sprayed. The staff was concerned about the potential paths that existed for this unborated water.
2.
The submittal did not provide detailed calculations showing the magnitude of unborated water that was being added to the refueling pool and the subsequent reduction in primary system boron concentration that could result from potential additions.-
of unborated water.
M' The staff raised these concerns in a meeting held at NRC headquarters with I
UE management on January 11, 1995. Based on the licensee's description of.
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the spray activities and on the staff's knowledge of the Callaway-Plant,
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the staff concluded that the licensee is aware of.the potential paths for unborated water entering the reactor core area. The licen:ee also stated a3 they had performed the calculations for determining the amount of boron.
M dilution that occurs as a result of using unborated water for decontamination purposes and that these calculations agree with the staff's estimation that the reduction in ppm boron concentration is minor.
i Based on this information, and the fact that the actual boron j
concentrations each cycle will be based on using one-half the. Reactor
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Coolant System Volume at mid-loop, the staff determined that further a
geineric analysis of boron concentrations by the licensee would not be D;
requi.ed.
The proposed changes do not involve any design changes, nor are there any
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changes-in the method by which any safety systems perform their function.
The ~ changes are required since the administrative controls described in the FSAR and Technical Specifications do not address the possibility for a boron dilution event directly from the reactor makeup water (RMW) system, as could occur when RW is used to rinse the refueling pool walls. This amendment establishes administrative controls for controlling the amount of unborated water added to the RCS from this source.
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Union Electric has proposed revising plant procedures which will enhance '
plant safety by reducing the potential for RCS boron dilution. The.
i procedural changes have been reviewed by the staff, and have been found to' d,
achieve this goal in a conservative manner.
The proposed changes to the FSAR and Technical Specifications are acceptable to the staff.
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3.0 STATE CONSULTATION
j In accordance with the Commission's regulations, the Missouri State sI official was notified of the proposed issuance of the amendment. The
'l State official had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to the installation or use of a f acility 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 issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding (60 FR 11151). Accordingly, this 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 this amendment.
5.0 CONCLUSION
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The staff 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 this amendment will not be inimical of the common defense and security or to the health and safety of the public.
Principal Contributor: G. Schwenk Date: March 31, 1995
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