DCL-89-182, Application for Amends to Licenses DPR-80 & DPR-82, Consisting of License Amend Request 89-08,reducing Boron Concentration in Boric Acid Sys from 12 to 4 Weight Percent
| ML16341F237 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 07/05/1989 |
| From: | Shiffer J PACIFIC GAS & ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML16341F236 | List: |
| References | |
| DCL-89-182, GL-85-16, NUDOCS 8907130038 | |
| Download: ML16341F237 (16) | |
Text
PG&E tter No. DCL-89-182 ENCLOSURE UNITED STATES OF AHERICA NUCLEAR REGULATORY COHHISSION In the Hatter of
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PACIFIC GAS AND ELECTRIC COHPANY )
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Diablo Canyon Power Plant
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Units 1
and 2
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Docket No. 50-275 Facility Operating License No.
DPR-80 Docket No. 50-323 Facility Operating License No.
DPR-82 License Amendment Request No. 89-08 Pursuant to 10 CFR 50.90, Pacific Gas and Electric Company (PG&E) hereby applies to amend its Diablo Canyon Power Plant (DCPP) Facility Operating License Nos.
The proposed changes amend the Technical Specifications (Appendix A of the Licenses) as regards to Technical Specifications
- 3. l. 1. 1, 3. 1. 1.2, 4. 1.2. 1, 4.1.2.2, 3.1.2.5, 3.1.2.6, 3.5.5, 3.9.1, 3.10.1, and Associated Bases associated with the boron concentration in the Boric Acid System.
Information on the proposed changes is provided in Attachments A and B.
These changes have been reviewed and are considered not to involve a significant hazards consideration as defined in 10 CFR 50.92 or require an environmental assessment
-in accordance with 10 CFR 51.22(b).
- Further,
-there is reasonable assurance that the health and safety of the public will not be endangered by the proposed changes.
Subscribed in San Francisco, California, this 5th day of July 1989.
Respectfully submitted, Paci ic Gas and Electric Company Howard V. Golub Richard F.
Locke Attorneys for Pacific Gas and Electric Company By J.
D.
ffer Vice P
sident Nuclear Power Generation Subscribed and sworn to before me this 5th day of July 1989.
Richard F.
Locke 27 73S/0069K OFFICIALSEAL ADRIANE D. toKfREE NOTARYPISUC ~ CALFOR%l QYGem Exits Dec. 22, 1992 S907i30038 890705 PDR ADOCK 05000275 P
PDC Adriane D. To efree, Notary.Public for the County of Alameda, State of California Hy commission expires December 22, 1992.
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ATTACHHENT A REVISION OF TECHNICAL SPECIFICATIONS 3.1.1.1, 3.1.1.2, 4.1.2.1, 4.1.2.2, 3.1.2.5,
- 3. 1.2. 6, 3.5.5, 3.9. 1, 3. 10. 1, AND ASSOCIATED BASES A.
DESCRIPTION OF AHENDHENT REQUEST This license amendment request (LAR) proposes to revise technical specifications associated with the boric acid system boron concentration.
This LAR will allow a change of the boron concentration in the boric acid system from 12 to 4 weight percent.
To implement this change the following modifications to the Technical Specifications (TS) are required:
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TS 3.1.1.1, "Shutdown Hargin Tavg Greater than 200'F":
Due to a decrease in boric acid concentration from 12 weight percent (20,000 ppm) to 4 weight percent (7,000 ppm) the borated water flowrate will be increased from 10 gallons per minute (gpm) to 30 gpm.
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TS 3.1.1.2,""Shutdown Hargin - Tavg Less Than or Equal to 200'F":
As in Technical Specification 3.1.1.1, boron concentration will be decreased from 20,000 ppm to 7,000 ppm and borated water flow-rate increased from 10 to 30 gpm.
TS 4.1.2.1, "Flow Path Shutdown":
The surveillance requirement for verification of the temperature of the heat tracing will be changed from 145'F to 65'F and the reference to heat traced portions of the flow path will be deleted.
TS 4.1.2.2, "Flow Path Operating":
The same revisions as in TS
- 4. 1.2. 1 will be made.
- Also, TS 4. 1.2.2d, which verifies every 18 months that the flow path to the RCS delivers a flowrate of 10 gpm, will be changed to 30 gpm.
'-'Borated Water Source Shutdown":
Since the boron concentration will be decreased from 20,000 to 7,000 ppm, the minimum usable borated water volume will be increased from 835 to 2499 gallons.
Also, the minimum solution temperature will be changed from 145'F to 65 F, the reference to a heat tracing channel will be deleted, the reference to a minimum boron concentration of 2,000 ppm for Unit 1 Cycle 2 will be deleted, and the cycle dependent notes will be deleted.
TS 3.1.2.6, "Borated Water Source - Operating":
Since the boron concentration will be decreased from 20,000 to 7,000 ppm, the minimum usable borated water volume will be increased from 5,106 to 14,042 gallons.
Also, the minimum solution temperature will be changed from 145'F to 65'F, the reference to a heat tracing 2773S/0069K
channel will be deleted, the reference to a boron concentration between 2,000 and 2,200 ppm for Unit 1 Cycle 2 will be deleted, and the cycle dependent notes will be deleted.
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TS 3.5.5, "Refueling Hater Storage Tank":
This specification will be revised to reflect that a boron concentration of between 2300 ppm and 2500 ppm is being utilized in Units 1 and 2 and the cycle dependent notes will be deleted.
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TS 3.9.1, "Refueling Operations - Boron Concentration":
The action statement will be revised to reflect the change to 7,000 ppm boric acid solution and the increased boric acid flowrate to 30 gpm.
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TS 3.10.1, "Special Test Exceptions - Shutdown":
The action statement will be revised to reflect the change to 7,000 ppm boric acid solution and the increased boric acid flowrate to 30 gpm.
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TS Bases 3/4.1.2, "Boration Systems":
The second paragraph currently states
- that, "The maximum expected boration capability requirement occurs at EOL from full power equilibrium xenon conditions."
This will be replaced by "The maximum expected boration capability occurs at BOL when borating from hot zero percent power to cold shutdown...."
The minimum usable borated water volume of 5,106 gallons will be increased to 14,042 gallons and the boron concentration of 20,000 ppm will be decreased to 7,000 ppm.
Also, the reference in the Bases specifying the volume of borated water in the refueling water storage tank (RHST) needed to provide adequate shutdown margin will be changed from 75,000 gallons to 65,784 gallons.
The above changes affect Modes 1 to 4.
The requirements for borated water for Hodes 5 and 6 are also affected.
The boric acid tank (BAT) required volume will change from 835 gallons of 20,000 ppm borated water to 2,499 gallons of 7,000 ppm borated water.
The reference in the Bases specifying the water volume in the RHST needed to provide adequate shutdown margin will be increased from 9,690 to 17,865 gallons.
Also, the reference to having heat tracing as a requirement for operability of the system is proposed to be deleted.
Proposed changes to the Technical Specifications of Operating License Nos.
DPR-80 and DPR-82 are noted in the marked-up copy of the applicable Technical Specifications (Attachment 8).
B.
BACKGROUND Design Basis The Diablo Canyon Power Plant (DCPP) uses two Boric Acid Tanks (BATs) for each unit, presently containing 12 weight percent 2773S/0069K
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The BATs are the primary source of boron within the Chemical and Volume Control System (CVCS) and are used to change the Reactor Coolant System (RCS)
RCS boron concentration or to provide RCS makeup water at the prevailing boron concentration.
The boric acid transfer pumps draw concentrated boric acid from the BAT.
The concentrated boric acid may be blended with primary water to a pre-selected blend and delivered directly to the volume control tank and/or to the suction of the charging pumps.
Hestinghouse
- designs, since the Farley Nuclear Plant, use 4
weight percent boron concentration in the BATs.
Hhi le the current Westinghouse design uses 4 weight percent, the historical design basis for earlier Hestinghouse plants such as Diablo Canyon had been for the combined capacity of the two tanks to contain sufficient 12 weight percent boric acid solution to, without makeup to the BATs, borate the plant to a refueling concentration at the end of life, and following a return to full power, to borate to a cold shutdown concentration.
The basis for this design was operational and not associated with mitigation of any design basis accidents.
The historical design basis has been reevaluated and determined to be overly restrictive.
The required constraints have been determined to be:
a.
As a minimum, the BATs must maintain adequate boric acid solution volume and concentration to borate the RCS (and CVCS) to a cold shutdown concentration at any time during the core cycle and with a shutdown margin consistent with the Technical Specifications.
This requirement is reflected in the changes proposed to Technical Specifications 3.1.2.5 and 3.1.2.6 requiring an increase in available boron volumes for various modes.
b.
Boric acid fluid temperatures must be maintained above the solubility limit throughout the acceptable concentration range.
This requirement is reflected in the changes made to the Technical Specifications that require minimum tank and piping temperatures.
c.
Sufficient volumetric margins must be provided to account for level instrument accuracy, avoid vortex formation within the tank outlet, and provide adequate boric acid transfer pump net positive suction head.
2.
Boric Acid System Hodiflcations The following system modifications will be made to allow for the reduced boron concentration in the BAT and to meet the constraints discussed above:
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a.
The two presently installed BATs at DCPP have a nominal storage capacity of 8,000 gallons each (16,000 gallons total).
To ensure that the proposed Technical Specification requirement of 14,042 gallons of 4 weight percent boric acid solution is always available in Modes 1 through 4, PQkE will install additional tankage to support plant operations.
This additional tankage will consist of two auxiliary tanks comnon to both Units 1
and 2 with approximately a 2,600 gallon capacity each.
This will allow at least one tank to always be available to rapidly fill the BATs while batching, recirculation, filling, or chemistry analyses are being performed on the auxiliary tank not lined up to fill the BATs.
These tanks will not be seismically qualified or designed as safety related tankage.
They are provided for operational convenience in order to have a ready supply of boric acid to refill the BATs.
These additional tanks will be installed at the earliest possible time, but not later than the Unit 1 fourth refueling outage.
b.
The internals of valves in the borated water flow path will be replaced with larger internals to allow an increase in borated water flowrate from the present 10 gpm to 30 gpm.
c.
The range on the boric acid flow transmitter and flow indicator will be increased to correspond to the new borated water flow-rate.
d.
The low level alarm settings at each BAT will be modified to satisfy the new Technical Specification requirement of 7,021 gallons for each BAT.
e.
The settings of the heat-tracing controllers will be modified to conform to the 4 weight percent boric acid concentration.
f.
The settings of each BAT heater temperature controller wi 11 be modified to conform to the 4 weight percent boric acid concentration.
C.
JUSTIFICATION Historically, the boric 'acid transfer
- pumps, associated heat tracing equipment, and the level instrumentation on the BAT have created maintenance and operations problems not only at DCPP but also at other operating power plants.
Precipitation in the BIT/BAT recirculation line may cause malfunctions of safety in]ection flow paths, as discussed in Generic Letter 85-16.
In addition, valve stem leakoffs for 12 weight percent boric acid systems are a source of continuous cleanup and maintenance.
These maintenance items are costly in terms of personnel time and, more importantly, personnel radiation exposure.
The requirement for heat tracing as a condition for operability of the boric acid injection system and boric acid storage system is proposed to be deleted.
PGhE intends to mai'ntain the heat tracing system as 2773S/0069K
presently installed with 1ts associated redundancy and alarm capabi lity.
The BATs have temperature indication on the main control board and are also alarmed.
The solubility limit of 4 weight percent boric acid (4.4 weight percent boric acid prec1pitates at 65 F) is much closer to normal room temperature than the 12 weight percent boric acid currently 1n use.
This means the fluid temperature will approach its solubility limit much slower and allow sufficient time for operator intervention.
The alarm capabil1ty of the boric ac1d system will advise operators if the temperature is outside the prescribed range.
Compensatory measures could be taken, if necessary, if the fluid temperature approaches 65 F.
Declaring a 4 we1ght percent boric acid system inoperable based on the loss of heat tracing is an unnecessary.
operating restriction since the room temperature could be greater than 65'F (e.g.
summertime).
The operab1lity requirement can be based on temperature as has been previously licensed on the Holf Creek Nuclear Power Plant.
r A license amendment for a similar change was also issued by the NRC for the Waterford Unit 3 Nuclear Power Plant.
There are also many operating Hestinghouse nuclear power plants that were originally licensed with 4 weight percent bor1c acid.
D.
SAFETY EVALUATION Util1zing nom1nal 4 we1ght percent boric acid, West1nghouse has determined that l4,042 gallons of borated water is an adequate reserve to provide proper shutdown margin for modes 1, 2, 3, and 4 and 2,499 gallons 1s adequate for modes 5 and 6 for the present 18 month core cycle.
Neither of these values are assumed as the basis for any analyzed accident.
The volume requ1rement of 14,042 gallons assumes an initial RCS boron concentration of 1,449 ppm at hot full power at the beginning of core life (BOL).
The reactor is then shut down using rods to hot zero percent power.
With rods still inserted, boron concentration is diluted to follow the xenon transient and facilitate a qu1ck return to hot zero'ower upon the withdrawal of the rods.
Margin is included such that the dilution results in a boron concentrat1on which permits a return to critical1ty without the rods being completely withdrawn.
This margin corresponds to the rod insert1on limit.
At this point, the boron concentration (1,097 ppm) 1s less than before the shutdown.
It is now assumed that the plant must go to cold shutdown boron concentration (1,695 ppm and 200 F).
Hestinghouse has also recalculated the RHST volume that is required to provide adequate shutdown margin (65,784 gallons of 2,300 ppm borated water for Modes l, 2, 3, and 4 and 17,865 gallons of 2,300 ppm borated water for Modes 5 and 6).
The same basis described above for the BAT volumes of 14,042 gallons for modes 1, 2, 3, and 4 and 2,499 gallons for modes 5 and 6, applies for the RWST volumes.
- However, no Techn1cal Specification revisions are required because the present required volumes spec1fied 1n LCO 3.1.2.5.b.l (50,000 gallons) and 3.1.2.6.b.l (400,000 gallons) bound these changes.
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Based upon the information provided above, PG&E believes that there is reasonable assurance that the health and safety of the public will not be adversely affected by changing the boric acid concentration from 12 to 4 weight percent.
E.
NO SIGNIFICANT HAZARDS EVALUATION PG&E has evaluated the no s1gn1ficant hazard considerations 1nvolved with the proposed amendment, focusing on the three standards set forth in 10 CFR 50.92(c) as quoted below:
The Ceanission may make a final determination, pursuant to the procedures 1n paragraph 50.9l, that a proposed amendment to an operating 11cense for a facility licensed under paragraph 50.21(b) or paragraph 50.22 or a testing facility involves no significant hazards considerations, if operation of the facility in accordance with the proposed amendment would not:
(1)
Involve a significant increase 1n the probability or consequences of an accident previously evaluated; or (2)
Create the poss1bility of a new or different kind of accident from any accident previously evaluated; or (3)
Involve a significant reduction in a margin of safety.
The following evaluat1on 1s provided for the no significant hazards consideration standards.
l.
Does the change 1nvolve a s1gnificant increase in the probability or consequences of an accident previously evaluated?
The BAT borated water is not assumed for mitigation of any of the des1gn basis acc1dents or transients in the FSAR Update.
The RWST, however, supplies borated water to mitigate accidents such as, Hinor Secondary System Pipe Breaks (FSAR Update Section l5.3.2), and, "Rupture of a Hain Steam Line (FSAR Sect1on l5.4.2.1)."
The new RWST volumes specified in the Bases section of the Technical Specif1cation for the BAT and RWST are bounded by the current volumes specified in the Technical Spec1fications.
Therefore, th1s change does not involve a significant 1ncrease in the probab1lity or consequences of an accident previously evaluated.
2.
Does the change create the possibility of a new or different kind of accident from any accident previously evaluated' Precipitation in the BIT/BAT recirculation 11ne may cause malfunctions of safety injection flow paths, as discussed in 2773S/0069K
Reducing the boric acid concentration from 12 weight percent to 4 weight percent will reduce the probability of precipitation of boric acid in the Emergency Core Cooling flow path.
Furthermore, the removal of heat tracing from the technical specifications will have no adverse affect because the fluid temperature 'will still be required to be maintained above the solubility limit.
Therefore, this change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
3.
Does the change involve a significant reduction in a margin of safety?
The Basis Section, 3/4.1.2, "Boration System," states that the boron in)ection system ensures that negative reactivity control is available during each mode of facility operation to provide a
sufficient boron water source to provide a shutdown margin from expected operating conditions of 1.6'X delta k/k after xenon decay and cooldown to 200 degrees and a shutdown margin of 1'X delta k/k after xenon decay and cooldown from 200 to 140 degrees.
The new BAT volumes of 14,042 gallons of 4 percent boron for Modes 1, 2, 3,
and 4 and 2,499 gallons of 4 weight percent boron for Modes 5
and 6 still meet this requirement.
Therefore, this change does not involve a significant reduction in a margin of safety.
F.
NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION Based on the above safety evaluation, PG&E concludes that the activities associated with this LAR satisfy the no significant hazards consideration standards of 10 CFR 50.92(c) and, accordingly, a no significant hazards consideration finding is justified.
G.
ENVIRONMENTAL EVALUATION PG&E has evaluated the proposed changes and determined that the changes do not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure.
Accordingly, the proposed changes meet the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Therefore, pursuant to 10 CFR 51.22(b),
an environmental assessment of the proposed changes is not required.
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