ML20116J326
| ML20116J326 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 08/07/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20116J308 | List: |
| References | |
| NUDOCS 9608130148 | |
| Download: ML20116J326 (6) | |
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NUCLEAR REGULATORY COMMISSION WASHHeSToN, D.C. 30eeH001 4,.....,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l
RELATED TO AMENDMENT NO. 215 TO FACILITY OPERATING LICENSE NO. DPR_il IES UTILITIES INC.
CENTRAL IONA POWER COOPERATIVE CORN BELT POWER COOPERATIVE DUANE ARNDLD ENERGY CENTER DOCKET NO. 50-331
1.0 INTRODUCTION
J By letter dated November 30, 1995, IES Utilities submitted information supporting the application of Long Tern Stability Solution Option 1 ') (1-D) to the Duane Arnold Energy Center (a General Electric (GE) BWR-4). The pckage consisted of a plant-specific licensing topical report (Anolication of i.h-
"Reaional Exclusion with Flow Biased APRM Neutron Fluy Scram" Stability Solution (Oction 1-D) to the Duane Arnold Enerav Cento.t GENE-A00-04021-01, September 1995) supporting application of the previou;1y approved Long Term Stability Solution Option 1-D (BWR Owners' Group Lona-Ters Stability Solutions Licensina Methodoloov, NED0-31960A, November 1995) to the Duane Arnold Energy Center (DAEC) and several attachments. The attachments describe the ODYSY code (ODYSY Description and Qualification (Proprietary), GENE-A038-0495, August 1995), and the changes to the plant technical specifications necessary to implement 1-D.
Generic l-D consists of two parts. First, an exclusion region in the power-to-flow map is established within dich power oscillations are credible.
Should the unit enter this region, operators are instructed to immediately exit the region or to scram the plant should >ower oscillations be detected.
Second, a statistical method is egloyed to slow that the existing flow biased average power range monitor (APRM) scram is sufficient to shutdown the plant in the event of oscillations before the Safety Limit Minimum Critical Power Ratio (SLMCPR) is violated. The flow biased APRM scram defines a line on the a
power-to-flow map above which the reactor is not allowed to operate.
Should the power range instrumentation detect operation above this line, the reactor will automatically scram. The 1-D statistical method is described in NEDO-32465 (BWR Owners' Groun Reactor Stability Detect and Suporess Solutions Licensina Basis Methodoloav and Reload Acolications, NED0-32465, May 1995),
which has been approved by the staff.
9608130148 960807 PDR ADOCK 05000331 P
4 2.0 EVALUATION In our safety evaluation (SE) of NED0-31960 dated July 12, 1993, the staff approved criteria that have to be satisfied before 1-D can be applied to a plant.
First, the core must be small and, therefore, tightly coupled. Duane Arnold is a low power BWR-4 with a small core of 368 fuel bundles.
Additionally, it was demonstrated in the supporting analysis presented in GENE-A00-04021-01 (the attachment to the Duane Arnold 1-D submittal) that the core wide decay ratio far exceeds the channel decay ratio over a wide range of operating conditions. This means that Duane Arnold is most likely to experience core wide (fundamental mode) as opposed to out-of-phase (higher mode) oscillations. The second criterion is that the core must have relatively tight inlet orificing. This has been demonstrated to favor the core wide mode over the out-of-phase mode. Duane Arnold has an inlet orifice size 14% smaller than a typical BWR-4. Duane Arnold, therefore, meets the criteria necessary to use 1-D.
In addition to meeting the acceptance criteria stated above for a 1-D plant, licensees have a choice of either using power distribution controls while operating or using an on-line stability monitor (staff SER on NED0-31960).
IES has opted to use an on-line stability monitor to provide operators with a means of detecting when the stability margin is degrading.
IES proposes to use a system called SOLOMON at Duane Arnold. SOLOMON incorporates the General Electric (GE) proprietary frequency domain code DDYSY into an on-line software package that runs on the plant process computer to provide an evaluation of the reactor decay ratio. SOLOMON can also be used in a predictive mode to evaluate the stability effect of proposed reactor maneuvers.
IES proposes to i
use SOLOMON at all times when the reactor is at power and to control certain types of operation if SOLOMON is inoperable.
In order to do this, a " buffer zone" (for an example see Figure 12 of Cycle 14 Core Operatina limits Report, Rev.1, IES Utilities, October 1995) is established, inside which operation is not allowed if SOLOMON is inoperable.
4 The detect and suppress methodology, as approved by the staff in its SER on NED0-32465 (dated March 4,1996), was used to calculate the smallest Minimum Critical Power Ratio (MCPR) during a postulated power oscillation event. This method allows demonstration, with a high statistical certainty, that the 3
SLMCPR will not be violated before the Flow-Biased APRM system trips the j
plant. The procedure outlined in NED0-32465 was properly applied to Duane l
Arnold and the Final Minimum Critical Power Ratio (FMCPR) was calculated to be 1.16.
Since this is still above the SLMCPR, the calculation demonstrates I
that, with a 95 percent probability and a 95 percent confidence (the 95/95 l
value), power oscillations will be successfully terminated.
1 In order for the analysis presented in GENE-A00-04021-01 to be applicable to cycles other than Cycle 14, specific reload confirmation criteria have been developed and included in Section 7 of GENE-A00-04021-01. These criteria conservatively establish deviations in core design within which the FMCPR calculations in GENE-A00-04021-01 are applicable to the operating cycle under consideration. The intent of these criteria is to only require the calculations presented in GENE-A00-04021-01 to be redone in the event that a change in the core that could affect the stability margin of the reactor i
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The staff has reviewed these criteria and conclude that they are occurs.
restrictive enough to require the FMCPR calculation to be redone when necessary and are, therefore, acceptable.
Review of individual Technical Specification Changes necessary to implement Option 1-D follows:
Ebanae to Paae vii This change deletes a reference to Figure 3.3-1, " Thermal Power vs. Core Flow l.inits for Thermal Hydraulic Stability Surveillance." This figure is no longer needed as it was used to laplement the Interin Corrective Actions (ICA) which are superseded by 1-D.
This change is acceptable.
Chanae to Paaes 1.1-11.12 This change updates the APRM High Flux Scram bases to reflect that this scram also protects the plant from stability transients.
See the discussion presented in the introduction describing the APRM scram and what it does.
This change is acceptable because the updated description of the APRM scram correctly identifies its purpose.
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Chance to Paae 3.3-6 This change states that operation in natural circulation is not permitted.
The change also provides for an action to scram the reactor if reactor operation in natural circulation occurs. This change is acceptable because it reduces the challenge to the basic 1-D operational strategy and the manual scram action is backed up by the flow biased APRM High Flux scram protection.
Chance to Paae 3.3-6 This change clarifies 3.3.F.2 to state that no recirculation pumps shall be placed in operation while the reactor is in natural circulation. Should a restart of the recirculation pumps occur if the reactor is critical and operating in natural circulation (recirculation pumps at zero speed), the core will experience a transient power increase associated with the increase in flow. This change is acceptable because it seeks to prevent the transient effect associated with this action.
Chance to Paaes 3.3-6.7 This revised TS replaces 3.3.F.3 with the requirement that the plant not operate inside the exclusion region.
It also states either power should be decreased or flow should be increased (assuming the recirculation pumps are still running) to immediately exit the region upon entry. Surveillance requirements 4.3.F.3 are also deleted. This change is acceptable because it is consistet with the 1-0 operational strategy that was previously reviewed and approved by the staff in NED0-31960A.
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Chance to Pace 3.3-7a This revised TS deletes stability related requirements for single loop j
recirculation operation and requirements related to core differential pressure noise. This change is acceptable because the unrevised TS applied to i
operation under the ICAs which are being superseded by 1-0.
1 Channe to Paae 3.3-7b i
This change deletes additional core differential pressure measurement 4
requirements. This TS was incorporated into the Duane Arnold TSs after a 1985 Single Loop Operation (1 out of 2 recirculation pumps running) event at i
Brown's Ferry in which high core plate noise was observed.
It was thought j
that this noise could be an indicator of core stability margin. The staff agrees with DAEC's conclusion that this measurement is not indicative of the l
core stability margin and, therefore, removing this TS is acceptable.
Chanae to Paaes 3.3-13.14 i
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This change clarifies the bases of the TS regarding recirculation pump i
operation. The bases adds a discussion about thermal hydraulic instability.
l Thermal hydraulic instability refers to the fact that under certain conditions (high reactor power and low core flow as an example) a self sustained l
resonance can be established in the core causing large fission power
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oscillations. This change to the bases correctly describes thermal hydraulic 3
instability and, therefore, is acceptable.
Chance to Paae 3.3-15 i
l This change adds a reference to GENE-A00-04021-01, " Application of the Regional Exclusion with Flow-Biased APRM Neutron Flux Scram Stability Solution (Option 1-D) to the Duane Arnold Energy Center." This report correctly t
applies the 1-D methodology previously reviewed and approved by the staff in i
BWR Owners' Group Lona-Tere Stability Solutions Licensina Methodoloav, NEDO-i 31960A, November 1995 and BWR Owners' Grous Reactor Stability Detect and Suecress Solutions Licensina Basis Methodoloav and Reload AcolicatdSD1, NEDO-i 32465, May 1995. This change is acceptable because the analyses presented in j
the report use approved methodology and the analyses are correctly performed.
j Chance to Pace 6.11-4 This change adds the exclusion region in the power-flow' map into the Core
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Operating Limits Report (COLR). This change is acceptable because the j
methodology defining the exclusion region is being incorporated into the 1
technical specifications.
i The staff has reviewed the changes proposed by IES Utilities to implement j
stability long term solution Option 1-D.
The implementation consists of TS changes and referral to GENE-A00-04021-01 which contains the analyses (which were performed using staff approved methods) supporting 1-D at Duane Arnold.
3 Also, the power-to-flow map exclusion region is added to the COLR. The staff i
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e O concludes that the methodology proposed for reference in the TS and the relocation of the exclusion region from the TS to the COLR are acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Iowa State official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
S This amendment changes a requirement with respect to installation or use of a facility component ' ocated within the restricted area as defined in 10 CFR Part 20 or changes a surveillance requirement. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluent 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 (61 FR 10394-95). Accordingly, the 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 the amendment.
5.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the 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 the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
T. Ulses, SRXB/DSSA 4
Date:
August 7,1996
4 4
c REFERENCES 1.
Aeolication of the "Reaional Exclusion with Flow Biased APRM Neutron Flux Scram" Stability Solution (Oction 1-D) to the Duane Arnold Enerav Center, GENE-A00-04021-01, September 1995.
2.
BWR Owners' Grous Lona-Tern Stability Solutions Licensina Methodoloav, NEDD-31960A, November 1995.
3.
ODYSY Description and Qualification (Proprietary), GENE-A038-0495, August 1995.
4.
BWL0wners' Grous Reactor Stability Detect and Succress Solutions Licensina Basis Methodoloav and Reload Acolications, NEDO-32465, May 1995.
5.
Cycle 14 Core Goeratina limits Report, Rev.1, IES Utilities, October 1995.
6.
Application of the "Reaional Exclusion with Flow Biased APRM Neutron Flux Scram" Stability Solution (00 tion 1-D) to the Monticello Nuclear fagneratina Plant, GENE-A00-04021-02, February 1996.
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