ML20043A822
| ML20043A822 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 05/11/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20043A819 | List: |
| References | |
| NUDOCS 9005230163 | |
| Download: ML20043A822 (6) | |
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NUCLE AR REGULATORY COMMISSION o
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i SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
'RELATED TO' AMENDMENT'NO.-109 TO FACILITY OPERATING' LICENSE NPF-9 t
AND AMENDMENT NO. 91'TO FACILITY OPERATING LICENSE NPF-17 DUKE POWER COMPANY' l
DOCKETS NOS. 50-369 AND 50-370 MCGUIRE NUCLEAR ~ STATION. UNITS 1 AND 2 l
1.0 INTRODUCTION
By letter dated May 9, 1990, as revised and supplemented May 10, 1990, Duke-Power Company.(the licensee) proposed amendments to the operatingLlicenses for McGuire Nuclear Station, Units 1 and 2, to revise surveillance requirements with respectEto the.
standard used for laboratory testing of the carbon.adsorber in the filter of the Unit 1 Annulus' Ventilation (VE) system.-
Presuntly,1for both Units.1 and-2, the carbon adsorber--is periodically tested by. removing a carbon-samplelfrom the filter and performing a laboratory analysis using'the< testing. criteria of Fegulatory Position C.6.a of 1 Regulatory Guide 1.52, Revision 2, ria rch 1978, for a methyl iodide-penetration of less than'1%.
l For Unit ~1 only, the amendment would revise surveillance:
f recuirements of Technical Specifications (TSs).4.6.1.8.b.2'and L
4.6.1.8.c to supplement the laboratory _ testing criteria of l
Regulatory Position C.6.a of Regulatory Guide: 1. 52 by1 speci f ying -
use of " Test Method A" of ASTM D3803-86 for a methyl iodide pe-netration of less than 0.71%.
TS 4.6.1.8.d.5 would also.be resvised for Unit i to reduce the lower limit of the allowable heat dissipation range to be'25.5 kW, rather-than the existing 36.6 kW, for: testing of the VE system; heaters.
Associa tred "TS =
Bases 3/4.6.1.8 would be. supplemented to discuss use.of-Test-Method A of ASTM D3803-96 for Unitol.
p The licensee has recently discovered that, under certain low l
voltage conditions'in conjunction with a loss of Joolant accident, sufficient power may not be supplied to the Unit.1 VE system heaters to maintain the relative humidity of the gases entering the VE carbon adsorber beds below 70% in accordance with existing TS 4.6.1.8.
Therefore, the Unit-1 VE system is-presently inoperable.-
McGuire Unit 1 is currently completing a refueling outage and is scheduled to enter Mode.4 (hot shutdown) on May 11, 1990.
Because the VE system is required to be operable before entering Mode A,
the licensee requested NRC.
approval of the proposed amendments on an emergency basis.
9005230163 900511 PDR ADOCK 05000369 L
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2 The amendments contain no changes of technical' substance for Unit
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Unit 2 is affected only administrative 1y because it shares a common TS document with Unit 1.
~ 2.0LEVALUATION:
During a review-of the heating, ventilation and-air conditioning systems at its Catawba Nuclear Station, the licensee discovered that the VE system heaters wereLnot-conservatively sized for all postulated 4 operating modes.
During postulated degraded grid
- voltage conditions with loss of-one o#.theLtwo offsite power sources.and with all' plant, auxiliaries of-the. unit 7 aligned to the other offsite power source through the remaining step-up-transformer,.and assuming-a-concurrent LOCA, sufficient power would not be supplied to the VE system heaters to maintain the-
.f relative-humidity of the air entering the.VELcarbon adsorber beds below 70% when the VE system flowrate is atEthe maximum valuei 8800 cfm, allowed by TSs.
The licenseets subsequent review of-the McGuire electrical system and VE system heatersfdetermined that the same problem exists there.'
TheElicensee. assessed potential. solutions and determined that-the. problem.could be mitigated for Unit 2 by reducing.its VE system?flowrate.within its allowable range and monitoring the voltage at<the 4160 volt bus to assure that the voltage at the VE heater terminal is maintained at or above 555 volts.
.This solution was not adequate for Unit 1, however, as the voltage Available to its heaters is less and the required reduction in flowratefwould, therefore, be excessive.
Consequently, the licensee requested the TS changes identified above.
In support of its requested changes, the licensee provided-the following discussion:
...we propose an emergency TS revision for McGu. ire Unit 1 which would change the testing standard. tor' the VE system carbon to another, more restrictive,. standard that is utilized for systems that don *t have' heaters.
for. humidity reduction.'
Revising the carbon absorber-test method will ensure the VE system filters maintain a decontamination' efficiency of greater than or equal to.95% under all anticipt.ted operating modes without use of the VE~ system heaters.. Even though we'would net be t& king credit for the VE' system-heaters, the heaters would still remain'in operation.
Whi'le'in operation, even under postulated degraded voltage, the relative humidity would not exceed approximately 85%.
In addition, and as a result of the carbon testing change, it is also-necessary to change the existing TS for Unit 1 (4.6.1.8.d.5),
regarding the VE system i
heaters power dissipation test.
The existing TSs j
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3 require a VE system flow of.BOOO cfm +/-10% and heat dissipation of 43 kW +/- 6.4.
.This value would be changed to 43 kW + 6.4 / -17.5.
.This limit is based on the consideration of a' degraded voltage with a corresponding heater capacity decrease, and the entering air.at 100%. relative humidity ~ andf122 degrees-F..
With the heater capacityodegraded by 17.5 kW-
-(surveillance-value converted to 600 volts), during a.
degraded voltage condition, the air entering the carbon filter would be approximately 85% relati've' humidity.
This humidity is well'below the 95% relative'. humidity specified by the proposed' carbon' test criteria, adding.
conservatism to the system operation.
As-stated, the VE system heaters are provided to ensure the relative humidity of the air entering the VE carbon absorber, h as is less than 70%. _Under-low voltage condition',
ith the maximum TS allowed VE system-flow.
rate of 86%G cfm, the relative humidity of the air?
entering the VE carbon absorber beds.is postulated to exceed 70%.
The proposed revision to.the: TS'will also change the-carbon-absorber: test method as described-in-Regulatory Guide 1.52'Rev 2, March 1978, Regulatory-Position C.6.a~to ensure the VE. filters continue to have a. decontamination efficiency'of greaterethan or equal to 95% under all anticipated operating conditions.
The proposed standard, ASTM D 3803-86', " Test Method A" will require testing of carbon samples at.30 degrees-C and at 95% relative humidity:for a-carbon-absorber bed
' decontamination efficiency of.95%.
TheEmethyl lodido penetration would.be' changed from'1%'to 0.71%.
Reducing the methyl lodide penetration.to 0.71% ensures-a carbon absorber decontamination factor of'95%, that is assumed in the existing McGuire FSAR Dose Analysis for'the VE' system.. The proposed methyl' iodide-penetration of O.71% instead of 1% alsoLincreases the penetration safety factor of the VE system from a factor of 5 to 7.
The requirements of the new standard compensate for the reduced capacity'of-the VE system heaters as a-result of the degraded voltage.
For the reasons described above, this change will conservatively ensure that calculated offsite'and onsite doses are not adversely affected while allowing the existing 8000 cfm +/- 10% VE system-flow rate.
The NRC staff has reviewed the licensee's p8oposed changes.
We agree with the licensee that use of Test Method A as a supplement to Regulatory Guide 1.52 provides an adequate compensation for the reduced voltage to VE system heaters and provides reasonable assurance that the carbon efficiency will-be maintained such-that'
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4 potential onsite and offsite doses will not be increased relative 4
to the efficiency and doses associated lwith existing TS requirements.
Moreover, we find that the use of. Test Method A as~
a supplement to Regulatory Guide 1.52, as proposed, meets General
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j Design Criterion 42 and is. consistent with the intent of the
' Standard Technical Specifications.
The proposed changes are, j
therefore, acceptable.
The NRC is continuing to. review the guidance of Regulatory Guide 1.52 for periodic updating, including its references'to appropriate industry. standards such-as ASTM D 3803-86 and later-versions of ASTM D 3803.
We note that, like'the current'TS requirements, ASTM D 3803-86 Test Method A. criteria.do not address an equilibration per'iod fcr testing samples from used carbon adsorbo.s.
A later version, ASTM D 3003-89,- published in February 1990, addresses this subject.. 'UntilEthe significance of an equilibration period during testing;of used carbon samples is better understood and the staff's present review of, Regulatory Guide 1.52 and associated standards is' completed, we conclude that our approval of the proposed <TS-changes.for McGuire. Unit l' should be. limited in duration'and should apply only until July 16, 1991, which -is sufficient for about one 18-month-inspection interval for the Unit 1 VE system required by-TS 4.6.1.8.b.
Thereafter the TSs for Unit i shall read the same as for' Unit'2.
We have appended a footnote to this end to'the TS pages.to be revised and have discussed this matter with the licensee.
3.0 FINDINGS OF EMERGENCY WARRANTING AN AMENDMENT WITHOUT NOTICE The licensee's application for the TS change has been timely.
In mid-April 1990 during a review of heating, ventilation and air conditioning systems at the Catawba Nuclear Station,-the' licensee discovered that the Catawba VE system heaters may.not receive sufficient voltage under certain-conditionsz.to< maintain the raquired relative humidity levels in air entering'the. carbon adsorber beds.
On April 27, 1990, the licensee initiated a similar review of the McGuire VE system to determine ~if this problem existed.
At the time, McGuire Unit.1 was completing a refueling outage and-was scheduled to reach Mode 4 on May 11,
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1990; Unit 2 was at full power.- Following its initial review, the licensee's Dosign Engineering group requested on May 3,
- 1990, that additional performa.nce data be acquired.to determine actual y
operating conditions on McGuire Units 1 and 2 with respect to the postulated degraded grid voltage condition.
From these results the licensee determined that Unit 2 could compensate for the lower heater voltage and heater dissipation by operating with-a decreased VE system flowrate within the allowed tolerance, but that the Unit i VE system would be inoperable if additional actions could not be-taken to raise flowrates to an acceptable level. The licensee assessed possible solutions to the problem, including adding an additional transformer to the power distribution system and replacing the VE system heaters with higher rated heaters.
From this assessment the. licensee
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p concluded that'the need to acquire replacement parts and to reanalyze the reconfigured power distribution systems could'not l-be accomplished withoutLa significant delay to the Unit-1 l
Thus, on Friday, on the evening of May~4, 1990, the I
licensee first realized that a TS change would be needed on an j
emergency basisEto avoid substantial delays in the restart of Unit.1.
Accordingly., on Monday morning, May 7, 1990, the l
licensee phoned the NRC to inform them of the situction and of the need for a prompt TS change.
The verbal-request was promptly followed by a written' application for TS change on May 9.
1990.:
'The NRC staff agrees with the licensee that failure to grant the L
proposed.TS changes in a timely, manner would result in a l
significant increase in outage time for Unit 1.
We also find that the licensee.could-not reasonably have avoided'this situation, that the licensee has responded inta' timely' manner, and has not' delayed.its application to take advantage.of~the Emergency License Amendments provisions of~1'O CFR 50.91' i
Accordingly, the staff concludes that the licensee hasEsatisfied' i
the requirements of 10 CFR 50.91-(a)(5), and'that a valid emergency exists.
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4.0 FINAL NO SIGNIF]QANT HAZARDS = CONSIDERATION DETERMINATION The Commission's staff has reviewed-~the licensee's reauest for the above-described amendments in accordance with 10 CFR 50.92-and finds that should the cnanges to the TSs:be implemented,'they would not 1
(1) Involve a-significant increase in the procability or l
consequences of an accident: previously evaluated.
The VE, system is an accident mitigation system only and has no causal effect on the occurrence of, and no effect on the probability-of, an accident.
The change to introduce a new dissipation voltage and testing standard does not alter the. function:offthe-system and the carbon efficiency remains the same as under'the present TSs.
Ratner, the changes would assure that, in the event of-low voltage conditions following an accident,'the VE system carbon adsorbers would continue to functionLas designed at a decontamination efficiency of 95% at c relative humidity ~up to H
95%. Therefore, the consequences of a'previously evaluated' accident would not -increase.
(2) Create the possibility of a new or different kind of accident from any accident previously' evaluated.
The changes do not introduce new-or modified equipment, or increase plant operating and safety limits.
No new failure modes would result.
g Therefore, no new or different kind of accident would be created.
(3)' Involve a significant reduction in a margin of safety.
l The changes impose a more conservative carbon testing requirement to assure the existing VE carbon adsorber efficiency is maintained at 95%.
Although credit for humidity reduction by the
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6 VE. system heaters at a reduced capacity was not included, the licensee states that the heaters would, under the postulated worst. case. accident and failure conditions, maintain the inlet air to theLVE carbon bed at approximately 85% relative humidity; thereby, adding conservatism.
The assumptions used.in the safety analyses-remain valid and-unchanged.- Therefore, the. margin-of safety associated with-the existing.TS would not be reduced.
'Accordingly, the Commission-finds'that these changes do not involve a significant hazards consideration.
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5.O' STATE CONSULTATION The State of North Carolina was informed by telephone on May 11, 1990,-of the NRC staff's no significantihazards consideration determination.-
The< State representative had no comments on the determination.
6.0 ENVIRONMENTAL CONSIDERATION
These amendments involve changes'to the requirements'with respect to installation or use of_ facility components. located'within the restricted area as defined in 10 CFR Part-20 and changes in-surveillance requirements.
The' staff has determined that'the-amendments involve no significant increase in the amounts -and'no significant change itt the types, of any effluents-that-may be released offsite and that there is no significant increase in individual or' cumulative occupational radiation expcsure.
The NRC staff has'made a final determination that'the amendments involve no significant hazards; consideration.
Accordingly, tho' amendments 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 impact statement or environmental assassment need be prepared in connection with the issuance of these amendments.
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7.0 CONCLUSION
We have concluded, based-on the considerations discussed above, thatt (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 these' amendments will not be inimical to the common defense and security or'to the health and safety of the public.
Principal Contributors:
D.
Hood, PD#II-3/DPR-I/II J.
Raval, SPLB/ DST Dated:
May 11, 1990
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