ML20053A822
| ML20053A822 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 05/18/1982 |
| From: | Diab S Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20053A820 | List: |
| References | |
| REF-GTECI-A-09, REF-GTECI-SY, TASK-A-09, TASK-A-9, TASK-OR NUDOCS 8205270318 | |
| Download: ML20053A822 (8) | |
Text
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UflITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSIllG BOARD In the Matter of
)
)
TEXAS UTILITIES GENERATING COMPANY, )
Docket Nos. 50-445
_ET _AL.
)
50-446
)
(Comanche Peak Steam Electric
)
(Application for Operating License)
Station, Units 1 and 2)
)
AFFIDAVIT OF SAMMY DIAB I, Sammy Diab, being duly sworn, do depose and state:
Q.1.
By whom are you employed, and what is the nature of the work you perform?
A.1.
I am employed by the U.S. Nuclear Regulatory Comission, Division of Systems Integration, Reactor Systems Branch
("RSB").
A copy of my statement of qualifications is attached to this affidavit.
Q.2.
What is the nature of the responsibilities you have regarding the Comanche Peak Steam Electric Station ("CPSES")?
A.2.
I was the Reactor Systems Branch lead reviewer for CPSES.
In this capacity, I was responsible for the safety review of the CPSES Final Safety Analysis Report ("FSAR") Sections 4.6, 5.2.2, 5.4.7, 6.3 and 15.0, in accordance with the corresponding sections in the Standard Review Plant, NUREG-75/087. Section 6.3 above addresses the design of the Emergency Core Cooling System ("ECCS").
8205270 3I8
. Q.3.
What is the subject matter of your affidavit?
A.3.
I will address the Atomic Safety and Licensing Board (" Licensing Board") questions regarding the deletion of the Boron Injection Tank (" BIT"). The Licensing Board requested that the Staff pro-vide the following information:
1.
A copy of the " Summary of Meeting on Comanche Peak Design Change and Responses to RSB Questions," by S. B. Burwell dated May 26, 1981.
2.
A description of the system or equipment to be deleted by removal of the BIT.
3.
The status of the deletion of the BIT.
4 The basis for the deletion of the BIT.
5.
The intended purpose of the system that was being taken out.
Q.4.
Are you familiar with the report entitled, " Summary of Meeting on. Comanche Peak Design Change and Responses to RSB Questions,"
by S. B. Burwell dated May 26, 1981?
A.4.
Yes. A copy of that report is attached to this affidavit as.
Q.5, Please describe the BIT?
A.5.
The BIT is a 900 gallon stainless steel tank filled with 12%
concentration Boric Acid, which is located between the discharge of the centrifugal charging pumps and the injection point into the reactor vessel cold legs.
The BIT system is provided with a recirculation loop consisting of a 75 gallon Boron Injection Surge Tank ("BIST"), and two 20-gpm Boron Injection Recirculation
. Pumps ("BIRPs"). This loop maintains the 12 percent boric acid solution in the BIT at a temperature in excess of the solubility limit, and circulates the solution to prevent cold spots and crystallization.
In addition the BIT, the BIST and the BIRPs are monitored by instrumentation indicating the systen temperature, pressJre and flow, and the level in the BIST. Alarms are provided in the control room to alert the operator to any deviations in the system operation. The BIT system which contains the 12% boric acid solution is isolated on each of the two sides (i.e., the charging pump side and the reactor vessel side) by parallel motor operated vtlves that are normally closed, and which open on a safety injection signal. All the piping, tanks and pump surfaces adjacent to the high concentration boric acid solution are either heat traced or maintained in heated enclosures.
Q.6.
What system was the BIT part of?
A.6.
The BIT was a component in the high head charging pump system for the Emergency Core Cooling System ("ECCS"). This charging pump system is designed to provide make-up water for core cooling when the reactor vessel (or primary coolant system) pressures remain high.
The system is made up of two centrifugal charging pumps in parallel taking suction through two parallal motor-operated valves from the Refueling Water Storage Tank ("RWST"). The
. RWST contains 450,000 gallons of 2000 parts /million (ppm) boron concentrated water. The two centrifugal charging pumps are designed to provide 150 gpm-each of emergency core cooling water at 2500 psig.
That is, the high-head pumping system is designed to provide core cooling at high pressures, when lower pressure systems are ineffective. The two centrifugal charging pumps discharge into four li" lines that inject directly into the four reactor vessel cold legs. is a schematic of the high-head charging system with the BIT. Attachment 3 is a schematic of the system without the BIT. is a piping and instrumentation diagram
("PID") of the high-head charging system with the BIT. Attach-ment 5 is a PID of the high-head charging system without the BIT.
Q.7.
How would the BIT be utilized? What was it's intended purpose?
A.7.
The intended purpose of the BIT was to limit the power increase following a steam line break event.
The BIT would be utilized any time the ECCS is activated by a Safety Injection Signal (" SIS").
The SIS starts the charging B
. pumps and causes the four BIT isolation valves to open, thus allowing the emergency core cooling water discharged by the centrifugal charging pumps to sweep the BIT inventory into the reactor vessel cold legs, and then into the reactor vessel.
The following is a scenario that delineates the operation of the BIT.
For a steam line break, the excessive RCS cooling leads to the primary coolant shrinkage.
As a result the pressure in the RCS drops to the point that SIS is initiated and the BIT boron-concentrated inventory is introduced into the RCS.
The RCS cooling that caused the RCS pressure drop, also adds positive reactivity to the core effecting a power increase. Since the boron-concentration inventory of the BIT adds negative reactivity to the RCS, the net effect of the BIT is to limit the power increase following an excessive cooling accident.
Q.8.
What is the basis for the Bl. deletion?
A.8.
The Applicants have submitted for Staff review an ECCS design change deleting the BIT.
The supporting evaluation submitted by the Applicants for the BIT removal stated that while the BIT pro-
, vided additional shutdown margins in the form of negative reactiv-ity through the 12% boric acid solution, this additional shutdown l
1
, nergin was taken credit for only in the steam line break analysis. With conservative system assumptions in the steam line break analysis the removal of t.ie BIT does not change the analysis results significantly, nor does it violate any safety criteria. The Applicants calculateo, for a large steam line break accident without the BIT, a Departure from Nuclear Boiling Ratio "(DNBR)" of about 2.5, which is well above the safety limit of 1.3.
Consequently, no fuel failure will result from a steam line break with no BIT, according to the Applicants' calculations. However, the Applicants' FSAR conservatively assumed 1% failed fuel initially and an additional 5% fuel failing af ter the steam line break accident for the purpose of maximizing offsite dose calculations.
Those doses were calculated to be a small fraction of the 10 CFR 100 limits.
Since the BIT deletion did not cause a violation of any safety limits, the Staff has found that deletion to be acceptable.
Q.9.
What components or equipment are deleted when the BIT is deleted from the CPSES ECCS?
A.9.
Components between the two upstream isolation valves and the two downstream isolation valves, except for the 4" pipe
, connecting the two sets of valves, are to be removed. The upstream isolation valves are either locked-open or removed.
The heat tracing is also removed. See Attachments 3 and 5 for schematics of the high-head changing system without the BIT.
Q.10.
What is the status of the Staff's review and evaluation of the BIT removal?
A.10.
The Staff has completed its review of the BIT removal and has found it acceptable for CPSES, as stated on page 4-21 of the Safety Evaluation Report ("SER") for CPSES:
The applicant has proposed deleting the concentrated boron injection tank (BIT). Although this is a change from previously approved Westinghouse designs, the applicant has shown that removal of the BIT will not result in any unacceptable transient or accident analysis results.
The staff concludes that the designs of the reactivity control systems conform to all applicable regulations and are acceptable.
The Staff concluded the CPSES has an acceptable ECCS design as shown in the Safety Evaluation Report ("SER") and Supplement 1 for CPSES. The Staff had previously concluded that removal of the BIT was also acceptable for the Turkey Point plant, units 3 and 4.
Q.11.
Will the BIT deletion affect the ability of the CPSES to operate safely?
A.11.
No. As explained in my Answer to Question 8, removal of the BIT will not affect the ability of CPSES to operate Safety.
The Staff's safety evaluation of the CPSES ECCS is shown in the SER and Supplement 1 for CPSES.
'~
.. 0.12.
What is the construction status of deletion of the BIT?
A.12.
The Applicants advise that it is bypassing the BIT in Unit 1, leaving the BIT unconnected and in place.
The BIT will not be installed in Unit 2.
The above statements and opinions are true and correct to the best of my personal knowledge and belief.
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SA!1MY DIAB,,
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Subscribed and sworn to me this \\9, day of May,1982.
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My Commission expires: '
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