ML20052F566
| ML20052F566 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 05/07/1982 |
| From: | Mizuno G NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD) |
| To: | |
| Shared Package | |
| ML20052F540 | List: |
| References | |
| NUDOCS 8205130193 | |
| Download: ML20052F566 (7) | |
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05/07/82 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMf11SSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of TEXAS UTILITIES GENERATING C0ftPANY, )
Docket Nos.90-445 el al.
)
50-446 (Comanche Peak Steam Electric Station, Units 1 and 2)
)
NRC STAFF'S RESPONSE TO THE ATOMIC SAFETY AND LICENSING BOARD'S REQUEST FOR INFORMATION CONCERNING THE DELETION OF THE BORON INJECTION TANK (" BIT")
I.
INTRODUCTION On February 23, 1982, Intervenor Citizens for Fair Utility Rates
("CFUR") filed with the Atomic Safety and Licensing Board (" Licensing Board") a "flotion for Voluntary Withdrawal of Contentions Two, Three, Five and Seven by CFUR" (" Motion").
In its Motion, CFUR stated that it "no longer had the financial capability to conduct a meaningful interven-tion" with respect to Contentions 2, 3, 5, and 7.
Motion, p. 1.
CFUR therefore moved for voluntary withdrawal from this proceeding.
Id.
However, CFUR alleged that Contentions 2, 3, and 7 " remain valid, unresolved issues which must be resolved by the Applicant..."
Id., p. 2.
CFUR submitted Exhibits 1 and 2 with its Motion as support for its claim i
that Contentions 2, 3 and 7 were " valid, unresolved issues."
In its Exhibit 1, CFUR for the first time in this proceeding raised questions regarding the deletion of the proposed boron injection tank
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(" BIT"). The BIT is part of the emergency core coolant systen ("ECCS")
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for the Comanche peak Steam Electric Station ("CPSES").
Based on these Exhibits, CFUR moved the Licensing Board to " investigate and adopt" Con-tentions 2, 3 and 7.
Subsequent to the filing of CFUR's Motion, the NRC Staff (" Staff")
filed its " Answer to CFUR's Motion for Voluntary Dismissal", (" Answer")
on March 15, 1982. The Staff did not oppose CFUR's withdrawal. However, because of the Licensing Board's March 5,1982 Order granting summary dispositionofContentions2and7,$/ the remainder of the Staff's Answer addressed only the issue, whether Contention 3 should be adopted sua sponte by the Licensing Board as a Board Question, pursuant to 10 C.F.R. $ 2.760a. The Staff's Answer did not discuss the issue of the safety consequences of deletion of the BIT, because the Staff was of the belief that the issue was not within the scope of Contention 3.2/
Contention 3 was subsequently dismissed from this proceeding by the Licensing Board.
Order (Following Conference Call), p. 2 (April 2, 1982). However, on March 26, 1982, the Board and the parties partici-pated in a telephone conference call. During that phone conference call, Dr. Cole requested that the Staff provide the Licensing Board with
" pertinent information...of record" relating to the BIT. The informa-tion requested was:
If The Licensing Board granted the Applicants' January 26, 1982 "itotion for Summary Disposition of CFUR's Contention 2 and 7".
Order (Granting Summary Disposition of Contentions 2 and 7)
(March 5, 1982).
-2/
The Staff is also of the belief that the issue of the BIT deletion was not within the scope of Contentions 2 or 7.
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 renoval 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.
In accordance with the Licensing Board's request, the Staff now provides the answers to the Licensing Board's questions concerning the BIT. The Staff does not believe that the BIT is necessary for the safe operation of CPSES. Affidavit of Diab, Answers 10, 11 and 8.
Therefore, the Staff does not believe that an evidentiary hearing on the deletion of the BIT is necessary to resolve this issue.
II. DISCUSSION Boron Injection Tank (" BIT") is a 900 gallon stainless steel tank filled with a 12 percent concentration of boric acid. Affidavit of Sammy Diab, Answer 5.
The BIT is part of the high-head charging pump system for the Emergency Core Cooling System ("ECCS") for CPSES.
Id.,
Answer 6.
The high-head charaing pump system provides make-up water for core cooling when either the reactor vessel or primary coolant system pressures remain high.
The high-head pumping system draws water through j
suction from the Refueling Water Storage Tank ("RWST"). The RWST contains 450,000 mallons of 2000 p.p.m. boron concentrated water. The l
RWST water is then injected into lines that lead to the four reactor
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4-f vessel cold legs by two centrifugal charging pumps.
Each pump has the l
l capability to provide 150 gallons per minute of RWST water, at a pressure of 2500 psig.
Id.
1 The BIT system consists of the BIT and a recirculation loop.
Id.,
Answer 5.
The recirculation loop maintains the 12 percent boric acid solution at a temperature in excess of the solubility limit, and circulates the solution to present cold spots and stratification.
Id.
i The BIT System is connected to the high-head pumping system lines between the discharge point of the centrifugal charging pumps, and the injection point into the reactor vessel cold legs.
Id, Answer 5.
Isolation between the BIT system, and the high-head pumping system is provided by four BIT isolation valves.
Id., Answer 7.
A schematic of the high-head charging system with BIT is provided as Attachment 2 to Mr. Diabs' affidavit.
The purpose of the BIT was to limit the reactor's power increase I_d., Answer 7.
If such an event following a steam line break event.
d j
occurs, excessive RCS cooling may lead to primary coolant shrinkage.
In addition, the cooling also adds positive reactivity to the core, resulting in an increase in the reactor core power. However, as the RCS pressure drops, the ECCS is activated by a Safety Injection Signal l
(" SIS"). The SIS starts the centrifugal charging pumps, and opens the four BIT isolation valves. As a result, the emergency core cooling water discharged by the centrifugal charging pumps sweeps the BIT l
water into the reactor vessel cold legs, and then into the reactor vessel itself. Since the boron solution of the BIT adds negative
. m.
reactivity to the RCS, the net effect of the injection of the BIT water inventory into the reactor is to limit the power increase following an excessive cooling accident.
Id.
The Applicants submitted for Staff review an ECCS design change deleting the BIT. A schematic of the high-head charging system without the BIT is shown in Attachment 4 to Mr. Diabs' Affidavit. The BIT deletion would entail removal of all components between the two upstream isolation valves and the two downstream isolation valves, except for the 4" pipe connecting the two sets of valves.
Id.,
Answer 9.
Due to the advanced state of BIT construction in Unit 1 of CPSES, the Applicants will bypass the BIT in Unit 1, leaving the BIT unconnected, but in place. The BIT will not be installed in Unit 2.
Id., Answer 12.
The Staff has completed its review of the BIT removal, and the Staff concludes that it is acceptable to operate CPSES without a BIT, 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 c. accident analysis results."
Id., Answer 10. The Staff's conclusion is based on its agreement with the Applicants' reasons for deletion of the BIT.
First, the Applicants noted that the additional shutdown margin provided by the BIT was taken credit for only in the steam line break analysis.
Even with conservation system assumpti.as in this analysis, the removal of the BIT did not change the steam line break analysis results significantly, nor was any NRC safety criteria violated.
Id., Answer 8.
The Applicants calculated that the Departure from Nuclear Boiling Ratio ("DNBR") for CFSES during a large steam line break accident would be 2.5, without the BIT. The DNBR figure of 2.5 without the BIT is well above the safety limit of 1.3.
Thus, no fuel failure will result if there is a steam line break at CPSES without a BIT. M. However, to be conservative,the Applicants' Final Safety Analysis Report ("FSAR") conservatively assumed that 1 percent of the fuel would initially fail, and that an additonal 5 percent of the fuel rods would fail after the steam line break, for the purpose of maximizing offsite dose calculations. The offsite doses were calculated to be a small fraction of the 10 C.F.R. Part 100 limits. Since the BIT deletion did not result in a calculated violatior, of NRC safety criteria, the Staff concluded that BIT deletion is acceptable.
III. CONCLUSION The Staff has evaluated the effects of removing the BIT from the high-head pump system of the ECCS for CPSES. The Staff agrees with the Applicants' analysis that the safety margin for controlling reactor power increases during steam line break events is not appreciably altered by the deletion of the BIT. Affidavit of Diab, Answer 8.
No NRC safety criteria would be violated by the BIT deletion. H. The Staff has determined that deletion of the BIT is acceptable and will not affect the ability of CPSES to operate safely.
_Id., Answers 10 and 11.
7-Accordingly, the Staff submits that an evidentiary hearing on the deletion of the IBT is not necessary to resolve any safety concerns arising from the BIT deletion.
Respectfully submitted,
.56 "
bb J.
v Geary S. Mizuno Counsel for NRC Staff Dated in Bethesda, Maryland this 7th day of May,1982.
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