ML20042G591
| ML20042G591 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/26/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20042G588 | List: |
| References | |
| NUDOCS 9005150120 | |
| Download: ML20042G591 (5) | |
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SAFETY EVALUATION PY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 53 TO FACILITY OPERATING LICENSE NO. DPR-80 y
AND AMENDMENT NO. 52 TO FACILITY OPERATIS LICENSE NO. CPR-82
[
PACIFIC GAS AND ELECTRIC COMPANi DIABLO CANY6N NUCLEAR POWER PLANT, UNIT NOS. 1 AND 2
]
DOCKET NO. 50-275 AND 50-323 1.0. INTRODUCTION By "DCL-89-182, Application for Amends to Licenses DPR-80 & DPR-82, Consisting of License Amend Request 89-08,reducing Boron Concentration in [[Topic" contains a listed "[" character as part of the property label and has therefore been classified as invalid. Sys from 12 to 4 Weight Percent|letter dated July 5,1989]], as supplemented by letters dated December 1, 1989 and April 10.-1990 (Reference LAR 89-08), Pacific Gas and Electric Cc'apany (PG&E or the licensee) requested amendments to the combined Technical Specifications (TS)~ appended to Facility Operating License Nos. DPR-80 and DPR-82 for-the Diablo Canyon Power. Plant (DCPP)
L Unit Nos.1.and 2, respectively. The amendments change the TS to allow the boric acid-concentration in the boric acid tank (BAT) to be reduced from twelve to four weight percent. Generic Letter 85-16, "High Boron Concentraticas." issued on August 23, 1985, discussed incidents at-operating nuclear plants in which boric acid has crystallized in the Interncis and-rendered systems inoperable. The changes permitted herein will reduce the potential for such incidents at Diablo Canyon and reduce routine maintenance and' operational problems o sociated with the boric acid storbge and transfer systems.
The licensee planc to install two auxiliary tanks common to both Units 1 and 2 to provide additional tankage to support plant operations. The boric acid system modifications and boron concentration reduction will not be mde until after these auxiliary tanks have been installed.
Consistent with the schedu_le for installation of the auxiliary tanks,
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.PG&E has requested that the revised Technical Specifications become effective for each unit following the refueliiig outage in which all the associated modifications are implemented. This will be the fourth 4
refueling outage for each unf t, currently planned for February 1991 for
. Unit 1. and October 1991 for Unit 2.
The staff evaluation of these chanes is given below and is based on the licensee's letters of-July 5, 1980, December 1, 1989 and April 10, 1990.
The information contained in the licensee's letters of December 1, 1989 and April-10, 1990 did not change the action noticed, or alter the staff's proposed determinstion of no significant hazards consideration published in the Federal Register on August 9, 1989 at 54 FR 32713. The December 1,.1989 and April 10, 1990 submittals only modify the proposed TS changes to delay, fce one cycle, the date of implementation for Unit 2.
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- n 2.0 EVALUATION L
The NRC staff has evaluated 'the proposed changes and finds them acceptable based on'its review of the analyses and evaluations given by the licensee. A discussion of.each of the specific technical specification changes made by these amendments is presented below.
The Diablo Can'on Power Plant uses two boric acid tanks for each unit
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each containi'g 12 weight percent boric acid. These tanks are the
.E rimar p(CVCS)y sour.:e of boron within the chemical and volume control system and are used to change the reactor coolant system (RCS) boron concentra',1on c.nd to provide RCS makeup water at the prevailing boron concentration.
p Early Westinghouse plants such as Diablo Canyon were designed with the capacity of the two BATS to contain aufficient 12 weight percent boric a:.id solution to, without makeup to the BATS, borate the plant to a refteling configuration at the end of life, and following a return to fbil power, to borate to a cold shutdown condition.
These criteria were based on operational considerations and were not associated with mitigation of any desi
- Farley Nuclear Plant (gn basis accidents. Westinghouse plants since the licensed in 1977) use 4 weight percent boric acid concentration in the BATS.
Westinghouse conducted a-plant specific analysis for Diablo Canyon Units 1 and 2-and determined that the following required constraints are necessary and sufficient to assure that the boric acid system can fulfill its safety functions:
A.
The BATS must maintain adequ6te boric acid soloi. ion volume and concentration to borate the RCS and CVCS to a cold shutdown at any time in core cycle with a shutdown margin consistent with that' required by the technical specifications.
B.
Boric acid fluid temperatures must be maintained above the solubility limit throughout the acceptable concentration range.
C.
Sufficient volumetric margins must be provided to account for level instrument accuracy, avoid vortex formation within the tu,k outlet and provide uequate boric acid transfer pump net positive suction head.
The first requNment is satisfied by increasing th6"6erated water volume as specified~in Technical S and 3.1.2.6 (Modes 1, 2, 3, 6nd 4)pecifications 3.1.2.5 (Modes 5 and 6)
In TS 3.1.2.5 the minimum boratod water volume in the boric acid storage system is increased from 835 gallons to 2499 gallons where the boron concentration is decreased
.from between 20,000 to 22,000 ppm to betwetn 7,000 and 7,700 ppm. This boron capability is sufficient to provide slutdown margin of 1 percent delta-k/k af ter unon decay and cooldown from 200'F to 140*F.
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TS 3.".2.6 deals with' Modes 1, 2, 3, and 4 when the RCS average temp a.ure is above 200'F. For this case a minimum of two boron
- injet.uon flow paths are required in the event that one path fails. The boron capability of either flow path is sufficier.t to provide shutdown margin from expected operating condition of 1.6 percent delta-k/k af ter xenon decay and cooldown so 200'F. The maximum expected boration capability requirement occurs at beginning of life (BOL) when borating from hot zero power to cold shutdown and requires 14,042 gallons of 7,000 ppm borated water from the boric acid storage tanks or 65,784 gallons of 2,300 ppm borated water from the refueling water storage tank. The borated water volume and boroa concentration values for.the-boric acid storage system were changed in Specification 3.1.2.6 to ag.'ee with these values. The minimum borated water volume in the refueling water storage tank was 400,00G gallons. This value was not changed.
The second requirement is reflected in changes in the minimum tank and piping temperatures. The BATS have temperature indication on the main control board and are also alarmed.
The minimum solution temperature
. will be changed from 145'F to 65'F, because 4.4 weight percet.t boric acid precipitates at 65'F.
Since the solubility limit of 4 weight percent is close to room temperature the fluid temperature would approach its solubility-limit slowly and allow time for operator intervention once the alarm was sounded. Thus, declaring the 4 percent weight percent boric acid system inoperable based on the loss of the heat tracing is not necessary. The proposed TS deletes the requirement for heat tracing as a condition for operability of the boric acid injection system and boric acid storage system.
Sufficient volumetric margins are available to account for level instrument accuracy, avoid vortex formation within the tank outlet and provide adequate boric acid transfer pump net positive suction head.
This satisfies the third requirement.
The following systems modifications will be made in order to implement the reduced boron concentration changes.
A.
The internals of. valves in the borated water flow path will be replaced with larger internals to allow an increase in borated water flow rate from 10 gpm to 30 gpm.
B.
The range on the boric acid flow transmitter and flow indicator will be increased to correspond to the new borated water flow rate.
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The low-level al u m settings on each BAT will be modified to satisfy the new requirement of 7,021 gallons for each BAT.
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The settings of the heat tracing controller will be modified to conform to the 4 weight percent boric acid concentration.
E.
The settings of each BAT heater temperature controller will be modified to conform to the 4 weight percent boric acid
-concentration.
F.
In order to have a ready supply of boric acid t'o refill the BATS, PG8E will install two additional auxiliary tanks with capacity of approximately 2,600 gallons each. Thus, at least one tank will be-available to rapidly refill the BATS even while batching, 3
recirculation, filling, or chemistry analyses are being performed in the other auxiliary tank. These tanks are not considered safety related but are provided for operational convenience. These tanks will be installed no later than the Unit I fourth refueling outage
-(February 1991). The boric acid system modification and boron concentration reduction.will not be made until after these auxiliary tanks have been installed.
In' summary, the staff has reviewed the safety analysis performed by PG8E in support of the )roposed TS changes to reduce the boric acid 3
concentration in tie BAT from twelve to four percent.
The changes proposed by PG&E will make the Diablo Canyon TS.similar to the' Technical L
Specifications for most Westinghouse plants and to the current Standard
!1 Technical Specifications. Since the analysis demonstrates that all the required constraints have been met, the proposed TS changes are acceptable.
PG&E plans to implement the required plant modifications and reduce boron concentration in the boric acid system after-installation of the auxiliary tanks.
The revised TS will be effective for each unit following the refueling outage in which the boric acid system
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-modifications are implemented-(the fourth refueling outage for each unit).
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3.0. ENVIRONMENTAL CONSIDERATION These amendments involve changes to a requirement with respect to the
. installation or use of facility components located within the restricted area as defined in 10 CFR Part 20 and a change in surveillance requirements. At Diablo Canyon, the restricted area coincides with the site boundary.
We have determined that the amendments involve 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 Comission has previously issued a' proposed finding that the amendments involve no significant hazards consideration and there has been no public coment on such finding. Accordingly.
setforthin10CFR51.22(c)(9.these amendments meet the elig)ibility criteria for cat Pursuantto.10CFR51.22(b),no environmental impact statement or environmental assessment need be prepared in connection with the issuance of these amendments.
4.0 CONCLUSION
We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the p(2) such activities will be conducted in coup 11ance with theublic will not be Commission's regulations and (3) the issuance of these amendments will not be inimical to the common defense and security or the health and safety of the public.
1 Principal Contributors: Margaret Chatterton L
Harry Rood l
Dated: April 26, 1990 1
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