ML20235G703
| ML20235G703 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 09/24/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20235G694 | List: |
| References | |
| REF-GTECI-B-19, REF-GTECI-B-59, REF-GTECI-ES, REF-GTECI-TH, TASK-B-19, TASK-B-59, TASK-OR GL-86-02, GL-86-09, GL-86-2, GL-86-9, NUDOCS 8709300169 | |
| Download: ML20235G703 (7) | |
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UNITED STATES y
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WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NOS. 125 AND 128 TO FACILITY OPERATING LICENSE N05. DPR-44 and DPR-56 PHILADELPHIA ELECTRIC COMPANY PUBLIC SERVICE ELECTRIC AND GAS COMPANY DELMARVA POWER AND LIGHT CCMPANY T LANTIC CITY ELECTRIC COMPANY PEAC.. BOTTOM ATOMIC POWER STATION, UNIT N05. 2 and 3 DOCKET N05. 50-277 and 50-278
1.0 INTRODUCTION
Py letter dated January 12, 1987, Philadelphia Electric Company (PECo or licensee) requested changes to the Technical Specifications (TSs) for Peach Bottom, Unit Nos. 2 and 3 relating to 1) core thermal hydraulic stability and 2) operation with jet pump flow indication failures and jet pump operability surveillance requirements. The application was in response to NRC generic letters 86-02 and 86-09, issued January 23, 1986 and March 31, 1986, respectively.
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On January 23, 1986, NRC issued generic letter 86-02, " Technical i
Resolution of Generic issue B-19-Thermal Hydraulic Stability", to j
licenseas of operating BWRs. The generic letter concluded that there was l
potential uncertainty in the approved methods for calculation of core stability decay ratio in predicting the onset of limit cycle oscillations. The generic letter stated that " licensees should examine each core reload to assure it is typical of previously evaluated cores which have acceptable stability margin. For cores which do not meet the analytical criteria, we have concluded that operating limitations which provide for the detection and suppression of flux oscillations in operating regions of potential instability consistent with the reconrnendations of General Electric SIL-380 are acceptable." The generic letter further stated thet:" all BWR owners should review the need for technical specifications (which enforce GE SIL-380 recommendations for I
operation of their plants) in light of the approved stability criteria and the status of core stability design calculations for specific plants.
Licensees are advised that the approved stability criteria are applicable to all operating reactors, and should be included in future safety evaluations in support of 10 CFR 50.59 determinations for all core reloads and design or operating modifications which relate to core thermal-hydraulic stability."
Philadelphia Electric Company (PECo) submitted a reload amendment for Peach Bottom Unit 2 by letter dated January 9,1987. The subject application for amendments is in response to generic letter 86-02. The hbf 7
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-7 proposed revisions to the Technical Specifications would add monitoring and operability requirements to the Unit 2 Technical Specifications to avoid the possibility for thermal hydraulic instability. The new, additional requirements would:
1)
Add a limiting Condition for Operation (LCO) to establish thermal power and core flow operating limits to avoid thermal hydraulic instability.
2)
Add a LCO to prohibit continued single recirculation loop operation below 39% of rated core flow and power above the 80% rod line.
3)
Add a LC0 to require APRM and LPRM noise level monitoring when operating in the regions of potential instability (low flow /high power).
4)
Revise an existing LCO to reduce the time limit for having the requirements applicable to single loop operation in effect from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to six hours.
5)
Remove a specification which prohibits operation in the natural circulation mode and replace it with an action to-be-taken requirements: namely, an immediate reduction of thermal power followed by a reactor shutdown within six hours if the mode switch is in Startup or Run with no recirculation loops in operation.
6)
Remove a restriction on operation at a maximum of 50% thermal power in the single loop mode since stability is assured by other re,strictions.
On December 3, 1984, the Commission issued Amendment 107 for Peach Bottom Unit 3 permitting increased core flow. Although generic letter 86-02 had not been developed at the time, the staff was developing some proposed Technical Specification provisions to preclude possible thermal-hydraulic j
instability. At the NRC staff's request, the licensee incorporated the provisions (which reflected the staff's position at the time) into the increased core flow application which was approved by Amendment 107 issued December 3,1984 and into the Peach Bottom Unit 2 Cycle 7 reload application which was approved by Amendment 108 issued March 19, 1985.
Now that the NRC requirements on thermal-hydraulic stability have been established (generic letter 86-02) some of the staff's previously proposed restrictions are no longer needed or applicable. Accordingly, the proposed amendments would revise the Unit 3 Technical Specifications to 1) remove APRM and LPRM noise level monitoring requirements in operating regions ?, 3 and 4; 2) decrease the allowable time for taking appropriate action when entering single loop operation from 24 to six hours; 3) increase the frequency for monitoring APRM and LPRM noise levels at low flows from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to once every eight hours; 4) reduce the upper core flow limit for Region I from 45% to 39% of rated flow, and 9 decrease the cut-off criterion for neutron flux noise levels from 5% to 4%. There would also for be some rewording and reformatting of the Technical Specification
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. requirements on recirculation pump operation to make the thermal-hydraulic stability requirements easier to understand.
2.0 EVALUATION The primary purpose of the PECo submittal is to provide suitable surveillance and action specifications for monitoring and suppressing, if necessary, core thermal hydraulic instabilities. The specifications reflect the conclusions of the staff Generic Letters 86-02 and 86-09
. (Refs. 2 and 3), which were based on extensive stability reviews and the recommendations of the General Electric report SIL-380 (Ref. 4). The specifications are required for operation under conditions of (a) Two Loop Operation (TLO) when approved analytical methods indicate that acceptable stability limits are not met and (b) Single Loop Operation (SLO), regard-less of analytical results.
These specifications generally call for restrictions or surveillance in the regions on the power-flow map above the 80 percent rod line and below 45 percent flow. This involves surveillance between 39 and 45 percent flow and no operation below 39 percent flow.
(Thirty-nine percent corresponds approximately to minimum two pump flow so that this restriction is effectively only for SLO.) ' Surveillance is b of the noise level of the Average power Range Monitor (APRM)y observation and selected LocalPowerRangeMonitor(LPRM)neutrondetectors. Noise levels greater than three times base levels generally call for noise suppression activity, e.g., lower power level or increased flow.
Peach Bottom 3 has stability surveillance and action specifications, approved in Amendment 107 (December 3, 1984). However, these were developed prior to the more recent staff reviews leading to the current positions of References 2, 3, and 4, and those TS differ from more recently approved TS, e.g., the Duane Arnold TS (See Reference 3 of Reference 3) or those for Susquehanna (Ref 5). Following discussions with the staff, the current Peach Bottom 3 TS have been revised in this submittal to reflect these recent staff positions and approvals.
3 The action and surveillance regions on the power-flow map given in the Peach Bottom 3 TS 3/4.6.F and Figure 3.6.5 have been altered. These now require, above the 80 percent rod line, no operation below 39 percent flow and surveillance up to 45 percent flow. Appropriate surveillance to establish base noise levels for the relevant (specified in Ref. 4) APRM and LPRM detectors is required. Action levels requiring power or flow change to suppress oscillations are set at noise levels of four percent and three times base levels. Appropriate times or frequencies for required surveillance and suppression actions are specified. These are all in accordance with NRC current positions and recent approvals and with Peach Bottom operating experience (as called for in Ref. 4). The proposed Specifications and Bases relating to Peach Bottom 3 TS 3/4.6.i are acceptable.
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. l Peach Bottom 2 currently has a TS 2.1.A.4 prohibiting operation in natural circulation (no recirculation loops in operation)..PECo proposes to move that TS to a Limiting Condition of Operation category as TS 3.6.F.6.
This specification requires immediate reduction of power and shutdown within six hours when no recirculation loops are in operation. Peach Bottom 3 has such a specification as TS 3.6.F.5, but with an allowable 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> for shutdown. PECo proposes that this be changed to six hours and the TS renumbered to 3.6.F.6, as with Unit 2.
When the TSs for-the first BWR-4s (such as Brown Ferry, Peach Bottom, Duane Arnold, etc.) were proposed, the NRC(AEC) staff had concerns about the possibility of thermal-hydraulic stability stemming from the GE test programs at low flows. At the time, there was not enough data at low flows to define what restrictions, if any, there should be on operating at low primary coolant flow rates. This was conservatively resolved by simply adding a safety limit in Section 2 of'all BWR-4 TSs prohibiting operation in the natural circulation mode.
Over the years, there have been extensive test programs and analyses funded by NRC end the utilities to determine what conditions might lead to thermal-hydraulic instability and what restrictions on plant operation will preclude entering these regimes.
In February 1985, a carefully controlled series of tests was conducted at Browns Ferry Unit I with NRC and Oak Ridge National Laboratory participation at various power levels and with two recirculation pumps in operation, with only one pump (single loop operation) and with no pumps operating (natural circulation).
Parameters were monitored with specially installed sophisticated instrumentation. The tests showed that stability ratios were very much better than had been predicted by(which are translated into flow rates)The perturbatio calculations.
pump differential pressure lines which had been noted in some BWRs at low-flow rates ( and had been regarded as an indication of possible instability) were due to harmonics set up in the sensing lines. The various test programs defined more precisely what restrictions would preclude thermal-hydraulic instability in all power / flow regimes,-taking into account instrumentation uncertainties. The proposed restrictions - i.e., proposed backfit TSs for BWR-4s, BWR-5s and BWR-6s - were presented to the NRC's Committee for Review of Generic Requirements (CRGR) 1H September 1985 as the proposed resolution of generic issue B-19.
The resolution approved by CRGR, including acceptable TS changes, were set forth in generic letter 86-02 issued January 23, 1986. The proposed TSs include restrictions on operation in the natural circulation mode. Thus, the specific restriction which is now in the Safety Limits Section (Section 2) of the Peach Bottom i
Unit 2 TSs (and which was in Section 2 of the Peach Bottom Unit 3 and many were other BWR TSs) is no longer necessary since the basis for the restriction is fully addressed by the overall restrictions (LCOs) being added to Section 3 of the TSs. The changes proposed by PECo are in accordance with generic letter 86-02 and are acceptable, i
The TS for both Paach Bottot units address the requirement for flow l
indication for the jet pumps for TLO (the indication for no more than one f
jet pump may be unavailable), but neither unit has a specification for SLO. PEco proposes to add TS 3.6.E.4 allowing no jet pump flow indication failures for SLO. They have also clarified the language, but not changed l
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. 1-the content, of TS 3.6.E.3 for TLO. They also propose that the surveillance
- specification 4.6.E.1.C requiring the diffuser to lcwer plenum pressure reading for a jet pump not to very from the mean of all pumps by more than 10 percent to be divided ir.to two (c and d), the first for TLD remaining the same and the second for SLO indicating the individual and mean references are to the operating loop. These changes are reasonable clarifications and are acceptable.
Peach Bottom 2 and 3 Amendments Nos. 78 and 77 (approved May 15,1981)
.were primarily : bout SLO. These amendments. approved SLO for these reactors but because of concerns about thermal hydraulic stability, a restriction of a maximum SLO power level of.50 percent was imposed. This restriction was removed for Unit 3 in Amendment 107 (December 3, 1984) after the NRC acceptance of the stability TS which are currently in effect for Unit 3.
It is still in effect for Unit 2.
PECo now requests that with the approval of the stability TS for Unit 2, the same as the recently improved TS for Unit 3, that the restriction Le removed for Peach Bottom 2 also. Since the stability question was the issue requiring the power limit, and since that problem has now been resolved and appropriate TS proposed, the removal of this restriction for Peach Bottom 2 is acceptable.
3.0
SUMMARY
PECo has proposed 10 for Peach Bottom 2 and 3 providing for surveillance and, if necessary, suppression of core thermal hydraulic instabilities.
The TS are in accordsnce with staff positions and other stability TS approvals. Our review has concluded that the appropriate material has i
been submitted and TS changes and additions are acceptable and that restrictions on Peach Bottom 2 SLO power level because of stability problems may be removed. Other proposed TS changes clarifying aspects of jet pump operability and natural circulation operation are also acceptable.
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4.0 ENVIRONMENTAL CONSIDERATION
S These amendments involve changes to requirements with iespect the to installation or use of facility components located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance requirements. The staff has detemined that the amendments involve no a
significant increase in the amounts, and no significant change in the l
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 this amendment involves no sip,nificant hazards consideration and there has been no public comment on such finding. Accordingly, these arenGnents meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental j
impact statement nor environmental assessment need be prepared in connection i
w?th the issuance of these amendments.
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5.0 CONCLUSION
The Commission made a proposed determination that the anendments involve no significant h8zards consideration which was published in the Federal Reoister on March 25, 1987 (52 FR 9578) and renoticed on May 20, 1987 (52 FR.18985) and consulted with the State of Pennsylvania. No public comments were received and the State of Pennsylvania did not have any comments.
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, and (2) such activities will be conducted in compliance with the Commission's regulations, and the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
H. Richings and R. Clark Dated: September 24, 1987 1
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6.0 REFERENCES
1.
Letter (and enclosures) from E. Bradley,'PECo, to H. Denton, NRC, dated January 12, 1987. " Peach Bottom Atomic Power Station Units 2 and 3."
2.
Generic Letter No. 86-02, " Technical Resolution of Generic Issue B-19 Thermal Hydraulic Stability," January 23, 1986.
3.
Generic Letter No. 86-09, " Technical Resolution of Generic Issue No..
B-59-(N-1)LoopOperationinBWRsandPWRs," March 31, 1986.
4.
General Electric Service Information Letter No.- 380,' Revision 1, February 10, 1984 5.
Letter (and enclosures) from E. Adensam, NRC, to H. Keiser, Pennsylvania-Power A Li9ht Co., dated April 11, 1986, " Amendment No. 56 and 26 to Facility Operating License No. NPF-14 and NPF-22 Susquehanna Steam Electric Station, Units 1 and 2."
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