ML20136D700
| ML20136D700 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 03/07/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20136D681 | List: |
| References | |
| GL-90-06, GL-90-6, NUDOCS 9703120463 | |
| Download: ML20136D700 (4) | |
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SO Cfo UNITED STATES NUCLEAR REGULATORY COMMISSION g
2 WASHINGTON, D.C. 30866-0001 J
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i SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 4
l RELATED TO AMENDMENT NO.180 TO 1
FACILITY OPERATING LICENSE NO. NPF-6 ENTERGY OPERATIONS. INC.
ARKANSAS NUCLEAR ONE. UNIT NO. 2 DOCKET NO. 50-368 1.0 INTRODUGILQN By letter dated April 11, 1996 (Ref. 1), as supplemented by letters dated September 5, (Ref. 2) and June 18, 1996 (Ref. 3), Entergy Operations, Inc.
(E01) (the licensee) submitted a request for changes to the Arkansas Nuclear i
One, Unit No. 2 (ANO-2) Technical Specifications (TSs). The requested changes 2
would add low temperature overpressure protection requirements to the TSs in accordance with recommendations contained in Generic Letter (GL) 90-06.
The supplements dated September 5, and June 18, 1996, provided additional information and modified the TSs slightly, but did not change the initial l
proposed no significant hazards consideration determination.
On June 18, 1991, E0I proposed modified TSs to satisfy the GL 90-06 requirements.
However, the relief valve setpoints were based on the topical report CEN-381-P. On June 14, 1995, the Nuclear Regulatory Commission (NRC) notified E01 that the CEN-381-P methodology was not acceptable.
E01 committed in a letter dated December 5, 1995, to submit a revised TSs request by l
April 15, 1996. Reference 1 fulfilled that commitment.
In the TS revision, E01 proposes to use the ASME Code Case N-514 as the basis for the low-temperature overpressure protection (LTOP) operating conditions. On January 28, 1997, NRC issued an exemption from the requirements of 10 CFR 50.60 which authorized the use of Code Case N-514 at ANO-2.
The ANO-2 LTOP system consists of a single discharge header from the pressurizer which feeds two redundant pressure relief valves each with an upstream motor operated isoittion block valve. The relief valves are operator aligned to the RCS during cooldown by opening the isolation valves and conversely are isolated during heatup by closing the isolation block valves.
The LTOP isolation valves provide the reactor coolant system (RCS) boundary in operating modes 1, 2 and 3.
The design basis LTOP event is a safety injection of two high pressure injection pumps and all three charging pumpg to a water solid RCS. Each LTOP relief valve )rovides a minimum of 6.38 in opening which has the capacity to relieve tie design basis event. To address the TS requirements of GL 90-06 for ANO-2, the transient pressure-temperature (PT) limits were reevaluated using the methodology of the Code Case 514 (ASME Section XI). The new limits are less restrictive than those estimated using Appendix G of ASME Section XI because the maximum vessel pressure for Code Case 514 is 110% of the pressure satisfying the Appendix G requirements, 970312o463 970307 ADOCKOSOOg8 DR
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2.0 EVALUATION 2.1 Inouts and Assi=ntions i
The relief valve setting is 430 psig (445 psia), and the valves are aligned to l
the RCS during cooldown and isolated from the RCS during heatup. An alarm will notify the operator if the temperature drops below the enable temperature i
during cooldown and the isolation valves are not fully open. The relief salve l
with the pressure setting, the enable temperatures and temperature settings and the revised PT curves settings combined with the revised PT curves j
comprise the LTOP system.
l In the revised LTOP system new pressure correction factors are associated with Code Case N-514.
In addition, administrative reactor coolant pump'F, twooperation limitationsareimposedasfollows:
no pumps operating below 120 j
pumps between 120 F and 200 'F and three pumps could operate above 200 F.
The temperatures represent actual cold leg temperatures without instrument uncertainty correction. Conservative pressurizer pressure and temperature instrument uncertainties of -85 psi and 20 *~ respectively were j
assumed. The pressurizer was assumed to be water solid at the lowest RCS i
temperature of 50 'F.
The PT limits are based on the existing temperature change rates and instrument corrections for pressure and temperature. The enable temperature i
was based on the existing analysis for the adjusted reference temperature at one-quarter thickness for 21 effective full power years (EFPYs) of operation.
l The relief valve opening model was an improvement on the original model with informationprovidedbythemanufacturer. The indicated enable temperature is 220 *F (200 F actual cold leg temperature +20 'F instrument uncertainty) for both heatup and cooldown.
3 The above assumptions used are acceptable because they are conservative and j
include accepted practice to accp)unt for pressure and temperature instrument error. While one valve (6.38 in is credited for depressurization both j
valves are enabled to meet the single failure criterion of Branch Technical Position RSB 5-2.
j The assumption of the 1/4T fluence at 21 EFPYs is conservative for several reasons:
(1) the original fluence value was determined using the second cycle high leakage fluence rate while the plant has been refueled with low leakage 4
loadings since the sixth cycle (currently is the 12th cycle) (2) the value for i
21 EFPYs will be used only to the next refueling when the plant will have experienced less than 13 EFPYs and (3) in recent cycles the inlet temperature at ANO-2 was lowered, thus, the density of the water in the downcomer j
increased. These conservatisms more than compensate for the fact that the original fluence was estimated using the ENDF/B-IV cross sections. ANO-2 does 4
not have a thermal shield; thus, the cross section change if ENDF/B-VI values were used would not affect the inner vessel surface flux by any significant amount. Therefore, the overall effect is that the conservatisms are 4
j significantly higher than the non-conservatism of the cross sections.
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I Per GL 92-01, the licensee will reevaluate the inner wall vessel fluence and submit the results in early 1997 (Ref. 2). This reevaluation will include the effect of the ENDF/B-VI cross sections and vessel chemistry and will include an estimate of the remaining EFPY operating margin and the next surveillance capsule removal schedule.
For the above reasons we find the proposed analysis model acceptable.
2.2 Results The enable temperatures for heatup and cooldown are 220 *F, where 200 'F is j
the actual cold leg temperature increased by 20 *F for instrument uncertainty.
The heatup and cooldown PT curve data are shown in Tables 2 and 3 and l
Figures 2 and 3 respectively in Ref. 1.
The calculated peak transient
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pressure from the design basis event with one LTOP relief valve operable is 517.7 psia. The corresponding RCS pressure is 526.6 psia. At this pressure the flow rate input from the two high pressure safety injection pumps and three charging pumps is 1532 gpm. The corresponding flow from a single relief valve is 1565 gpm which indicates that the valve capacity exceeds the mass input. The discharge will take place at a lower pressure than 517.7 psia which represents a conservative value for the pressurizer peak transient pressure. The pressure temperature limits indicate that the maximum pressure is conservative.
3.0 Procosed Technical Soecifications The proposed TSs correspond to those in Enclosure B of GL 90-06 which is appropriate for a Combustion Engineering designed plant.
There are two changes:
(1) the safety injection tank (SIT) must be isolated with the LTOP operable and the SIT pressure higher than the RCS pressure and (2) the proposed ANO-2 TSs do not include action (e) of Enclosure B which requires that a special report be filed whenever the LTOP vents are used to mitigate a transient. The first deviation is acceptable because it accomodates the presence of a pressurized SIT.
Regarding the second deviation; the licensee developed administrative requirements for reporting LTOP relief valve actuations on the same basis as the Improved Standard Technical Specifications (ISTS) require the reporting of pressurizer safety valve and pressurizer relief valve actuations.
ISTS require annotation in the monthly operating report whenever the pressurizer relief valve is actuated. The GL 90-06 reporting requirement consists of a special report within 30 days following an LTOP relief valve actuation.
Either reporting method provides timely notification to the cognizant NRC technical branch if the LTOP pressure relief vent is actuated.
The reporting requirement proposed by the licensee is similar to reporting requirements at other plants, meets the intent of GL 90-06, and is therefore
. acceptable.
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4.0 STATE CONSULTATION
In accordance with the Conunission's regulations, the Arkansas State official was notified of the proposed issuance of the amendment. The State official had no comments.
5.0 ENVIRONMENTAL' CONSIDERATION The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has determined 3
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 l
occupational radiation exposure. The Commission has previously issued a pro-posed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (61 FR 20846). 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.
6.0 CONCLUSION
l The Commission has concluded, based on the considerations discussed above, j
that:
(1) there is reasonable assurance that the health and safety of the pui>1ic will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commis: ion's regulations, j
and (3) the issuance of the amendment will not be ininical to the common defense and security or to the health and safety of the public.
7.0 REFERENCES
J 1.
Letter J. W. Yelverton, Entergy Operations Inc. to US NRC " Proposed Technical Specification Change Request for Exemption to 10 CFR 50.60 for j
ASME Code Case N-514" April 11, 1996.
2.
Letter from J. W. Yelverton, Entergy Operations Inc. to US NRC " Additional l
Information on ANO-2 LTOP for Fluence Considerations" September 5, 1996.
3.
Letter from J. W. Yelverton, Entergy Operations Inc. to US NRC
" Supplemental Change Regarding ANO-2 Proposed Technical Specification On Low Temperature Overpressure Protection" June 18, 1996.
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Principal Contributor:
Lambros Lois f
Date:
March 7, 1997 4
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