ML20246A891
| ML20246A891 | |
| Person / Time | |
|---|---|
| Issue date: | 10/20/1986 |
| From: | Burnett R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Philips J NRC OFFICE OF ADMINISTRATION (ADM) |
| Shared Package | |
| ML20244E562 | List: |
| References | |
| NUDOCS 8905080356 | |
| Download: ML20246A891 (24) | |
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ISSUANCE OF NOTICE .
-1 MEM0PANDUM FOR: John Philips, Chief Rules and Procedures Branch Division of Rules and Records, ADM FROM: Robert F. Burnett, Director Division of Safeguards, NMSS
SUBJECT:
ISSUANCE OF NOTICE Please arrange for the enclosed notice to be published in the Federal Register. This notice extends the time period for submittal of security plan amendments in response to the recently published Miscellaneous Amendments (51 FR 27817). The extension is necessary to allow for development and distribution of pertinent generic guidance to power reactor licensees. This action has been coordinated with the Offices of the General Counsel, Nuclear g
Reactor Regulation, Inspection and Enforcement and S. Wigginton of your staff.
NMSS contact is P. Dwyer, 42-74773. Thank you.
M. &Qr Robert F. Burnett, Director Division of Safeguards, NMSS ,,
Enclosure:
FRN to extend. amendment submittal period ,
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NAME :PDwyer:jr :JYardumian :GMcC rkle :ETenEyck :RBurn t : :
DATE:10/j /86 :10/ 86 :10/gQ/86 : ENCLOSURE 1
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[7590-01]
NUCLEAR REGULATORY COMMISSION 10 CFR Parts 50 and 73 Miscellaneous Amendments Concerning Physical Protection of Nuclear Power Plants; Extension of Time Period for Submittal of Plan Amendments e
AGENCY: Nuclear Regulatory Commission.
ACTION: Final rule; extension of time period for submittal of plan amendments.
SUMMARY
- On August 4, 1986, the Nuclear Regulatory Commission (NRC) published a final rule entitled, " Miscellaneous Amendments Concerning Physical Protection of Nuclear Power Plants." Section 73.55 contains the requirement for affected licensees to submit to the NRC security plan amendments in response to the new regulation by December 2, 1986. Due to the type and number of questions the m
NRC staff has received from power reactor licensees following the final rule's-publication, the period for submittal of security plan amendments
- in response to this new regulation is being extended by six months to June 2, 1987. This will permit the distribution of generi'c guidance that will' assist power reactor licensees in the development of their security plan amendments. .
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DATES: The time period'for submittal of- security plan amendments fin _
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responseto.theMiscellaneousAmendments.ConceiningPhysicalProtection
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_ of Nuclear Power Plants.has been~ extended and:now exp i res on June 2, 1987.
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[7590-01]
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ADDRESSES: Send security plan amendments in response to this new rule to: Director, Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 20555.
FOR FURTHER INFORMATION CONTACT: Priscilla A. Dwyer or Donald M. Carlson, Division of' Safeguards, Office of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, Washington, DC 20555 Telephone:
(301) 427-4773 or 427-4712, respectively.
Dated at Washington, DC, this day of , 1986.
For the Nuclear Regulatory Commission.
Samuel J. Chilk, Secretary of the Commission
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j . QUESTION 1. How should the " Miscellaneous' Amendments -
Concerning; Physical 1 Protection of Nuclear Power
- Plants" and amendments concerning " Searches of Individuals at Power Reactor Facilities" be submitted?
ANSWER.
' Plan amendments should be submitted to NRC Headquarters (Director, Office of. Nuclear Reactor Regulation ATTN: Document Control-Desk) as amendments in response to'the new rules. They should not be submitted under the provisions of 950.54(p) or 550.90. Six copies of the plan amendments should be submitted.
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Reference:
' @73.55 - Requirements for physical protection of 1
l licensed activities in nuclear power reactors I l'
against radiological sabotage, as printed in FR/Vol. 51, No. 149/ Monday, August 4, 1986/
Rules and Regulations /pages ?7817-27825 I
Conmittee/NMSS December 8, 1986 ENCLOSURE 2 1
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QUESTION 2. Can a generic SER be used to document a NRC licensing reviewer's findings on'the adequacy of commitments made by licensees in response to the Miscellaneous Amendments ANSWER.
Yes, but an appendix which details certain of the specific commitments should be attached to the generic SER and protected
> pursuant to 573.21 requirements.
Reference:
Current policy.
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Committee /NMSS November 19, 1986
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QUESTION 3. Does the licensee's: security-plan have to_be amended to.: incorporate _ commitments made-in response:to-the Miscellaneous Amendments?'
. ANSWER..
Yes.
Reference:
. R. Fonner, OGC, November 12,,1986.
Committee /NMSS December 8, 1986 1
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OVES, TION d.- What is meant by the' statement that, "Certain
, ' access controls may be suspended during emergency or abnormal plant conditions ..."?
-ANSWER.
-10 CFR 50.54(x). states a licensee may take reasonable action that departs from NRC issued license conditions or technical specifications in an emergency or abnormal condition declared by a senior licensed operator when, (a) the sa*Je operation of the reactor is affected, (b) the action is immediately needed to protect the public health and safety, and (c)'no action consistent with the license conditions and technical specifications that can provide adequate or equivalent protection is immediately apparent.
This same authority-also applies to physical security and
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safeguards contingency Plans and plant procedures relating to security matters.
Reference:
Regulatory Guide 5.65, Section 3 - Control Of Access To Vital Areas Under Routine Conditions, Subsedttop 3.1 -
Access List Committee /NMSS November 19, 1986
QUESTION 5. May access controls-for a' vital area be suspended when a. life threatening. event has occurred to~an on-site person?
ANSWER.
No. Suspension of. safeguards measures under 10 CFR 50.54(x) and-(y) should be exercised only.under conditions affecting the safe operation of the power reactor. It is believed'that the safeguards measures required under 10 CFR 73.55 adequately provide for emergency response to other events.
Reference:
Regulatory Guide 5.65, Section 5 - Sespending Security Measures, Subsection 5.3 - Controls That Can.Re Suspended During An'Emergencv Committee /NMSS December 8, 1986 i
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. QUESTION 6. What individuals are included in the term
" operating personnel" as used in the state-ment, "To facilitate access, operating personnel
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should b'e'provided with keys to open doors that are locked for security or other purposes"? l l
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ANSWER. j The term " operating personnel" means any individual who by virtue
, of.;his/her position is authorized to manipulate any reactor controls in order to mitigate or attempt to mitigate an emergency
- or abnormal condition and any member of an emergency response team.
Reference:
Regulatory Guide 5.65, Section 4 - Emergency Access To Vital Areas, Subsection 4.1 - Access Keys
- Committee /NMSS November 19, 1986 emea emy-"
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What individuals are included in the term OUESTION 7.
! "necessary personnel" as used in the statement, ,
" Ensure that all necessary personnel have keys" when, vital area locks fail closed during a power or computer outage? -
ANSWER.
> The term "necessary personne1" means the same as the term
" operating personnel" discussed in Item 6 above, but also I
includes security personnel.
Reference:
Regulatory Guide 5.65, Section 4 - Emergency Access To Vital Areas, Subsection 4.3 - Loss Of Electric .
Power i
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When should vital area hard keys which override l QUESTION 8.
vital area access systems be issued to operating personnel?
l ANSWER.
Vital area hard keys should be issued to on duty operating personnel at the beginning of each shift and properly accounted
- for at the end of each shift or as currently specified in a i
.. licensee's approved security plan. The use of any such keys to enter vital areas, however, must cause a vital area alarm to be generated and'a response must occur when the door is opened. .
Reference:
Regulatory Guide 5.65, Section 4 - Emergency Access .
To Vital Areas, Subsection 4.1 - Access Keys h
Committee /NMSS November 19, 1986 em.-e M m-M,Jae-p
QUESTION 9. Is a key card. considered to be "a related access control device" subject to the requirement to be changed or rotated at least once every twelve j months? !
ANSWER.
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No. However, whenever there is evidence or suspicion of compromise, or whenever an individual is terminated for cause, the individual's access authorization should be immediately removed from the key card system.
Reference:
673.55(d)(9) - Access Controls l
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Committee /NMSS November 19, 1986
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i OUESTION 10. Must licensees rotate or change keys, locks, etc.', if an individual's unescorted access authorization is temporarily suspended as opposed to " revoked"?
l-ANSWER.
If an individual's unescorted access authorization is temporarily suspended pending a review, locking devices do not have to be rotated or changed as long as access control devices possessed by the individual are returned to management and the individual is escorted while on-site. If the. individual's unescorted access authorization is permanently revoked for cause at the end of the review, locking devices must be changed or rotated.
Reference:
%73.55(d)(9) - Access Requirements Committee /NMSS November 19, 1986
e SUESTION 11. May all vital area' doors fail open during.a power outage or emergency?
I nSEER.
Yes. However, sufficient guards must be immediately available and-deployed to. monitor ingress / egress of the vital. area doors.
Groups of vital area doors may be monitored by a. single _ guard provided that direct observation of all doors can be maintained.
If a. sufficient number of guards are not available to monitor all vital area doors, then the doors should fail shut, be provided with mechanisms for emergency egress, and procedures implemented
. to assure emergency access by operational personnel.
Reference:
Regulatory Guide 5.65, Section 4 - Emergency Access To Vital Areas, Subsection 4.3 - Loss Of Electric Power Committee /NMSS ,
December 8, 1986 L_____________________---_-_---------_---_-_-___------_--__
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QUESTION 12. Can logging-of individuals granted access to vital areas.be suspended during emergencies and power outages?
ANSWER.
Logging requirements to vital areas may be suspended only when an emergency or abnormal condition has been declared by a " licensed senior operator." ,
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Reference:
573.70(d) k l
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Committee /NMSS -
November 19, 1986
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0VESTION 13. Do the revised search requirements mean that every time a member of the security. force leaves the protected area (PA) to perform official duties lhat he or she must be equipment searched for weapons, explosives, and incendiary devices prior to re-entry to the PA?
ANSWER.
Members of the security force must be equipment searched on their. initial entry to the PA at the beginning of their work shift. If these individuals leave the PA to perform official duties subsecuent to this initial search, they need not be searched prior to.re-entry into the PA if they have been under the direct observation or accompaniment of a member of the security organization while outside the PA. Security force individuals who do not meet this criterion must be equipment searched prior to their re-entry to the PA.
Reference:
673.55(d)(9) - Access Requirements .
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Committee /NMSS December 18, 1986 Ll_ ____ _ ___
.pVESTION 14.. If walk-through detection equipment alarms upon the search of an individual, must the individual be immediately " pat-down" searched or may the ind.ividual be more stringently searched by hand-held detection equipment to determine whether " pat-down" is necessary?
ANSWER.
If an alarm is received when an individual passes through a walk-through detector it is acceptable to conduct a search using hand-held equipment to assist in determining if a " pat-down" i search is needed.
Reference:
673.55(d)(9) - Access Requirements i
1 Committee /NMSS December 18, 1986 l l
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What~doesla security plan 1 commitment .to detect OVESTION_15.
r explosives at the entry point to the protected
' area; mean?;
.ANS}lER.
J Such a commitment means that a licensee has pr'ocured and is maintaining commercially available " state of the-art" walk-throuch explosives detection equipment.
' Re'f e ren c e : 673.55(d)(9) - Access Requirements j
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Committee /NVSS ;
December 18, 1986 i
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0VESTION 16. 'Is the central alarm station-(CAS) no longer 1
. required to be protected as vital?
. ANSWER. -l While the CAS is no longer specifically designated as-vital equipment by NRC' requirements, it is the NRC's policy that-it remain in'a vital area.
Reference:
' 73.55(e)(1) - Detection Aids i
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Committee /NMSS !
December 18, 1986 i
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OVESTION'17. Doe's an on-site secondary power supply system
.for a privately owned telephone system have to be
-located within a vital area?
MSWER.
l No.- Only the secondary power supply systems for non-portable-radio. communications equipment and alarm annunciators equipment have to be. located in vital area's.
Reference:
673.55(e)(1) - Detection Aids i
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Committee /NMSS December 18, 1986 l l
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'00ESTION 18. Does the_ requirement to locate "on-site l I
secondary power supply. systems for alarm l 1
annunciator equipment and non-portable )
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communications equipment" within vital areas mean that the on-site secondary power supply systems for non-portable communication equipment or the alarm annunciator and non-portable communications equipment itself must be located within vital areas?
I ANSWER. -i This requirement means that the on-site secondary power supply f systems for both the alarm annunciator and non-portable radio communications equipment must be located within a vital area.
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Reference:
673.55(e)(1) - Detection aids
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l Committee /NMSS December 18, 1986 l
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,s o L. I' QUESTION 19.. Does the-secondary alarm stations (SAS) secondary; power supply systems for alarm annunciator equipment and non-portable commbnfcations equipment have to be_ pro-tected as. Vital equipment?
ANSWER.
No. Only the secondary power supply systems for.the primary systems have to be Protected.
Reference:
573.55(e)(1) - Detection Aids i
i I Committee /NMSS l~
December 18, 1986
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'i OUESTION 20. What components of the secondary power supply systems ~for the alarm annunciator and non-portable communications equipment ~have to be protected as vital equipment?
ANSWER.
The ob.iective of secondary power supply systems (SPSS) is to provide auxiliary power during power interruptions or outages for periods of.
up to eight hours in duration. In view of the objective, it is necessary to protect all components of a SPSS needed to provide this period of stand-by power. Such components may include, but are not necessarily igmitedto,thefollowing:
- a. Batteries
- b. Battery chargers
- c. Inverters
- d. AC alternators
- e. DC generators
- f. Emergency buses ..
- g. Control panels
- h. Switch gear
- 1. Identifiable Cabling
- j. Main Fuel tanks or day tanks and associated plumbing / piping
Reference:
673.55(e)(1) - Detection Aids and Regulatory Guide l 5.65, Section 7 (Protection of Security Equipment)
Committee /NMSS December 18, 1986
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' 90ESTION 21. Can the secondary power supply systems for alarm annunciator equipment and non-portable communications equipment consist of.
"interruptible power systems (IPS)"~or do they have to be "uninterruptible power systems (UPS)"?
ANSWER.
Generally, the use of UPS is the preferable method for providing emergency power. However, IPS may also be a suitable means for providing emergency power if systems can withstand momentary failures of electric power input without significant detriment to
- the systems.
Protection devices like alarm annunciators are usually rendered ineffective or are immediately reduced in effectiveness if there is any interruption of their input power. Therefore, the Regulatory Position is that UPS should be used to protect the annunciators load from fluctuations or interruptions of the incoming power. On the other hand, momentary interruption.of power to non-portable communications equipment may be acceptable provided that secondary power is available within one minute.
973.55(e)(1) - Detection Aids and Regulatory Guide
Reference:
5.65, Section 7 - Protection of Security Equipment i
Committee /NMSS December 18, 1986
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4 jog UNITED STATES
[(
5 4l p, NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20655 DEC 181986 MEPORANDUM FOR: Robert M. Bernero, NRR Richard W. Starostecki, IE Richard E. Cunningham, NMSS Denwood F. Ross, RES Clemens J. Heltemes, Jr. , AEOD Joseph Scinto, OGC i
FROP: James H. Sniezek, Chairman Comittee to Review Generic Requirements
SUBJECT:
CRGR MEETING NO. 105 .
The Committee to Review Generic Requirements (CRGR) will meet on Thursday, January 15, 1987, 1-4 p.m. in Room 6507 MNBB. The agenda is as follows:
1-2 p.m. - S. Scott (IRM) will brief the CRGR concerning NRC's request to OMB to continue the re keeping burden ( 4 million hours)ofporting 10 CFRandPart record-50.
(Category 2 item.)
j 2-4 p.m. - T. Speis (NRR) will present for CRGR review the enclosed l
proposed Revision 2 of Standard Review Plan Section 6.5.2,
" Containment Spray As a Fission Product Clean-Up System."
(Category 2 item.)
If a CRGR member cannot attend the meeting, it is his responsibility to assure 4 i. hat an alternate, who is approved by the CRGR Chairman, attends the meeting.
Persons making presentations to the CRGR are responsible for (1) assuring that j the information required for CRGR review is provided to the Committee (CRGR Charter - IV.B), (2) coordinating and presenting views of other offices, (3) as
- t. appropriate, assuring that other' offices are represented during the presenta-tion, and (4)-assuring that agenda modifications are coordinated with the CRGR contact (Walt Schwink, x28639) and others involved with the presentation.
Division Directors or higher management should attend meetings addressing agenda items under their purview.
In accordance with the ED0's March 29, 198a memorandum to the Commission con- i cerning " Forwarding of CRGR Documents to the Public Document Room (PDR)," the enclosure, which contains predecisional information, will not be released to the PDR until the PRC has considered (in a public forum) or decided the matter addressed by the information.
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M fOlucd f 3 :, Jtmes H. Sniezek, Ch irman 7[f ,C mmittee to Review Generic s Requirements
Enclosure:
As stated .
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DEC 181986
. 2-cc: SECY Commission (5)
V. Stello, Jr.
Office Directors Regional Administrators W. Parler S. Scott T. Speis S
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UNITED STATES y,, pg 8 o NUCLEAR REGULATORY COMMISSION 'p r
$ : ,E WASHINGTON, D. C. 20555 b g*****,/ DEC 0 5126 MEMORANDUM T0: James H. Sniezek, Deputy Executive Director for Regional Operations and Generic Requirements FROM: Harold R. Denton, Director Office of Nuclear Reactor Regulation
SUBJECT:
PROPOSED REVISION 2 0F STANDARD REVIEW PLAN SECTION 6.5.2,
" CONTAINMENT SPRAY AS A FISSION PRODUCT CLEAN-UP SYSTEM" The enclosed generic requirement review packages are being submitted for consideration by the Committee to Review Generic Requirements (CRGR), as a category 2 action. This proposal seeks to revise the Standard Review Plan section which is used by the staff to assess the degree to which off-site poses are mitigated by containment sprays in evaluating radiological consequences to assure compliance with 10 CFR Part 100. The revisions include a number of minor changes to acknowledge the recent reorganization of the review staff, as well as changes which, by explicitly stating equations and numerical parameters previously contained in numerous references, will simplify the review procedure by anyone unfamiliar with those references.
These proposed changes constitute relaxations in current staff positions which are judged to have no significant detrimental effect on plant safety while providing cost savings for the industry. These changes would remove the current review emphasis on immediate actuation of spray additive systems and decrease the amount of additives that would be needed to achieve significant fission product clean-up. These changes affect staff positions which at pr'sent e conservatively underestimate the efficacy of containment sprays as
. fission product clean-up systems.
The major changes in this SRP relate to the need for chemical additives in the spray system, and to post-accident pH control of the containment sump solution. The revised SRP proposes that chemical additives are not necessary
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during pray injection, although licensees may retain this feature. The revised SRP also proposes that post-accident pH control of the containment sump solution be retained (at a pH of 7 or greater) at the time of recirculation to prevent evolution of volatile iodine. In contrast, the present SRP requires that the sump solution pH be maintained at 8.5 or greater.
It should be noted that licensees are not required to make any changes to their spray system under this SRP revision. However, for licensees of existing plants to profit by this revision, it would be necessary for them to amend their FSARs and license technical specifications and, upon approval, to perform modest changes in plant design and emergency procedures. As discussed in the enclosed package, for some older plants the potential cost savings may be too small to justify the expense, while other licensees may achieve significant savings.
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DEC 0 5 bst.
l James H. Sniezek Included in the enclosed packages are a Brookhaven National Laboratory technical report and a brief technical background paper. The Brookhaven report is a technical finding document that serves to support the minimum value of a mass transfer coefficient used in the proposed review procedure.
The background paper is intended as an explanation of the most important chemical evidence dealing with the relationship of the acidity of sump solutions to the long term retention of fission product iodine.
Following CRGR consideration, this package will be submitted to the ACRS.
After amendment to accommodate any comments from both of these committees, public comments will be sought.
Committee consideration of this action prior to January,1987, would be appreciated, t
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arold R. Denton, Dire or Office of Nuclear Re or Regulation
Enclosures:
As stated h
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' N U REG-0800 (Formerly NUREG 75/087) pm RECg
\ .7 I U.S. NUCLEAR RdGULATORY COMMISSION
@N$s)STANDARD REVIEW PLAN 1
OFFICE OF NUCLEAR REACTOR REGULATION
%*ese*f' 9 top h banwA 2 b 6.5.2 CONTAINMENT SPRAY AS A FISSION PRODUCT CLEANUP SYSTEM REVIEW RESPONSIBILITIES Primary - Acci&nt Evaluation Oranch (AES) P\ad hshs Sonh
$ Secondary Chemical-EwJ i neer-ing-Branch-(CNEB} he
}3 I. AREAS OF REVIEW g @o\ arc g wt e-- T M., or i
-[ The-AEB-rev-iews-Ahe containment spray and,, spray additive 4 systemgto determine the fission product removal effectiveness of the system whenever the applicant claims
@e~WontaininEthcleanup function for the system. The following areas of the g applicant's Safety Analysis Report (SAR) relating to the fission product removal g and control function of the containment spray system are reviewed.by the ^ES:
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- 1. Fission Product Remcval Requirement for Containment Spray Sections of the SAR related to accident analyses, dose calculations, and fis-( sion product removal and control are reviewed to establish whether fission product scrubbing of the containment atmosphere for the mitigation of offsite doses following a postulated accident is claimed by the applicant. This review usually covers Sections 6.2.3.1, 6.5.2.1, and Chapter 15 of the SAR. ;
2.
Design Bases ad The design bases of such containment spray systems are reviewed to determine whether they reflect the requirements placed upon this system by the assump-tions made in the accident evaluations of Chapter 15.
- 3. System Design The descriptive information concerning the design of the spray system, including any subsystems and supporting systems, is' reviewed to familiarize the reviewer with the design and operation of the system. The review includes:
1 Rev. 1 - July 1981 USNRC STANDARD REVIEW PLAN Star dard review plans are prepared f or the guidance of the office of Nuclear Reactor Regulation staff responsible for the review of applications to construct and operate nuclear power plants. These documents are made available to the public as part of the Commission's policy to inform the nuclear industry and the general public of regulatory procedures and policies. Standard review I plans are not substitutes for regulatory guides or the Commission's regulations and compliance with them is not required. The standard review plan se'ctions are keyed to the Standard Format and Content of Safety Analysis Reports for Nuclear Power Plants.
Not all sections of the Standard Format have a corresponding review plan.
Published standard review plans will be revised periodically, as appropriate, to accommodate comments and to reflect new inf orma-tion and experience.
l i Comments and suggestions for improvement will be considered and should be sent to the U.S. Nuclear Regulatory Commission, Office of Nuclepr Reactor Regulation, Washington o.C. 20555.
a___.____________________________ _ _ . _ _ _ _ _ . _
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@h The descriptive informationscontained in SAR Sections 6.2, 6.5.2.2,
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6.5.2.4, 6.5.2.5, and 6.5.2.6 to establish the basic de:,ign concept, g the systems, subsystems, and support systems required to carry out
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- go 7 the ,iodiee scrubbing function of the system, and the components and instrumentation employed in these systems, c (#
- b. The process and instrumentation diagrams of SAR Section 6.5.2 or 6.2.2, whichever contains the relevant information.
, c. Layout drawings (plans, elevations, isometrics of the spray distribu-tionheaders,fromSARChapter1.0andSection/)6.5.2or6.2.2.
- d. Plan views and elevations of the containment layout in Chapter 1.0 of the SAR.
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recers and i :trumentat4en41 gram: c f--any-v en t-i 4 at i on-sy s tem s ~ ope ra =
4ional--in-the-pes-taccident-env i ronmen t .
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- 4. ' Testing and Inspections r i'
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Section 6.5.2.4 of the SAR.is reviewed to establish the details of the 5 preoperational test'to be performed for system verification and the post- f operational tests and inspections to be performed for verification of the continued status of readiness of the spray system. e- 1
- 5. Technical Specifications 6 '
y At the operating license stage, the applicant's proposed technical speci- (
fications in Chapter 16 of the Final Safety Analysis Report (FSAR) are reviewed to establish permissible outage times and surveillance 4(
requirements.
M cr a cecandery review-is-per4ermed4y the Chemical Engineering Branch (CMEB) and -
the--results-are- used4y-the-AEB-to complete-the -overal1 teview-of -the contain- f ina n + creey syster CMEB revic~ +ha cha-4c21 edditive ster:ge requirements-
.and areas 2 i ndicated belew-The-results of CMEBls-analysis -are-transmitted. j a
t-c AE9 fer use 4- the SER ~ 4 teep. ~6 ggwr In addition, Af8-will coordinate other br:nches evaluations that interface with q,
-the review o,f the containment spray system as follows:
CMES r:.ici!: metal'i go materials compatibility and organic material decomposition including formatioh of organic iodide as part of its primary revicte rc:pencibi'ity for SRP Sections 6.1.1 and 6.1.2. The-Containment Systems-Branch (CSS) reviews the heat removal and hydrogen $ mixing function of the containment spray system and the containment sump design as part of its pr mary--rev4ete rc:pencibility-for i
SRP Sections 6.2.2 and 6.2.5. The acceptance criteria for the review and the methods of application are contained in the referenced SRP sectionicf the en"raepnndia; primary branch :: ct:ted :beve. 4 II. ACCEPTANCE CRITERIA The AE6- acce* p tance criteria are based on meeting the relevant requirements of the following regulations: j k
, 6.5.2-2 Rev. 1 - July 1981
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.2 A. General Design Criterion 41 (Ref. 1) as related to the containment atmos- d phere cleanup system being designed to control fission product releases 9 p to the environment following postulated accidents. e s-
'B. General Design Criterion 42 (Ref. 2) as related to the containment E atmosphere cleanup system being designed to permit appropriate periodic inspections.
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" J:
C. General Design Criterion 43 (Ref. 3) as related to the containment atmos- n/
phere cleanup system being designed for appropriate periodic functional testing.
Qf g
Specific criteria necessary to meet the relevant requirements of GDC 41, 42, fj y
a and 43 are: 5: T Fs%koNeO $ .3
- 1. Design Requirements for Icdine Removal Functier d a d6 ~
The containment spray system should be designed in accordance with the g ANSI requirements of Reference 4, As used in this S" section, the term j "centaiament-spray-system" inc-ludes-the-spray-system-end-th-spray -addi- J'c p t4ve subsystem n defined in Referenc^ d. cSce p % T ve irmc Cu Orfu,3 9 tog obddd< or okr % ccwM qsb d %s re{creece wy g%. Q[vM,y5 t-*
- a. System Operation {f 96 The containment spray system should be designed to be initiated auta- Qy matically by an appropriate accident signal and to be transferred automatically from the injection mode to the recirculation mode to b&
r e #
assure continuous operation until the design cbjectives of the system yJ G t have been achieved. In all cases the operating period should not be ngU less than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. v'In-addit 4en, th: y n a :hould be-eepable-of operation-in-the-recirculation mede, on-demand, for a period-of-at-
.3 ' T least 1 month fe!!cwing -the pc:tulated accident. O J'e
. E w.,r.
-r d r-
- b. Coverage of Containment Volume ,ggg
%g '
In order to assure full spray coverage of the containment volume, <vt the following should be observed: ft c *
(1) The' spray nozzles should be located as high in the containment as practicable to maximize the spray drop fall distance.
)i (2) The layout of the spray nozzles and distribution headers should be such that the cross-sectional area of the containment covered by the spray is maximized and that a nearly homogeneous distribu-tion of spray in the containment volume is produced. Unsprayed regions in the upper containment and, in particular, an unsprayed annulus adjacent to the containment liner should be avoided wherever possible. ,
(3) In designing the layout of the spray nozzle positions and orien-tations, the effect of the postaccident atmosphere should be considered, including the effects of postaccident conditions that result in the maximum possible atmosphere density.
1
( -
.- 6.5.2-3 Rev. 1 - July 1981 '
1 ,
L___m_____.__ _ . _ _
i a
- c. Promotion of Containment Mixing Because the effectiveness of the containment spray system depends on (
a well-mixed containment atmosphere, all design features enhancing postaccident mixing should be considered. -Where necezary, fceced-ci vcnt-i4ethhou4d-be-prcvided tc -cvcid-stegnent-air regicas.
- d. Spray Nozzles The nozzles used in the containment spray system should be of a design that minimizes the possibility of clogging while producing drop sizes effective for iodine absorption. The nozzles should not have internal moving parts such as swirl vanes, turbulence promoters, etc. They should not have orifices or internal restrictions which would4"^r"+4an narrow the flow passage to less than 1/4-inch diameter. "ct:#'cd vm the drop ;icc di;tribution for thc noccic, suc-h-as-a-h44togram r
-5hould bc grevidcd. Designetiens such on "ove ogc," "mesn," snd "mcd+er," numbcc; do not provide ; sufficiently detailcd informat40tHe-pei mit on indcpcadcat cycluatica cf the pcMor# nance-of the. nozz-le.
- e. Injectic^ Spray Solution The partition of iodine between liquid and gas phases is enhanced by the alkalinity of the solution. The spray system should be designedj 6 such that the spray solution maintains the h4 ?es+ pess4ble pH,fwithin material compatibility constraints. e
" v ie - n+ 4e oticfiad by-a-spray-pH-in-the range-of-Br5-to 10. 5. ^ -iniaun-partitioning of iodi ne between-149 u44-end-gas--- ph::c ha; che been demcastrated I for beric acid 004ution: "ith-teace -levch of 'mpurities-(Refr5).
La thic care, pH requirements-are deter 4ned ce!cly by ~2teri 1
.r.ompatibi'ity constraints, which cre reviewed by C"CO. Iodine scrubbing credit is given for spray solutions whose chemistry, including any additives, has been demonstrated to be effective for iodine absorption and retention under postaccident conditions. -Bee-theoretical-and-experimental verification are required.-
spray solutions shown in Table 6.5.2-1 have been shown to be ef ive for removal of elemental iodine. Acceptable, values f ese the ins ntaneous elemental iodine partition coefficient for 6 provides spray solu ns are also shown in Table 6.5.2-1. Refere information o ray solutions that are effective for emoval of organic iodides.
Table 6.5. Spray Solutions nd Acceptable artition C ficients Spray solution artition coefficient sodium hydroxide in boric see ure 6.5.2-1; ph values' acid solution are ass ed at room temperature hydrazine (50 ppm 5000
- boric acid (15 9-2500 ppm boron) 50 x' hh Water (pl 'n or demineralized) 100 [
~ ' . '- tris ium phosphate (added to see Figure 6.5.2-1; same pHs .
s dependence as sodium hydroxide' 4 4 4 p during recirculation mode) solutions
~
6.5.2-4 Rev. 1 - July 1981
(
l .
t ,
- f. Containment Sump Mixing )
lhe containment sump should be designed to promote mixing of emergency core cooling system (ECCS) and spray solutions. Drains to the engineered safety features (ESF) sump should be provided for all regions of the containment which would collect a significant quantity of the spray solution. Alternatively, allowance should be made for " dead" volumes in the determination of sump pH and the quantities of additives injected, q
- g. Containment Sump and Recirculation Spray Solutions The pH of the aqueous solution collected in the containment sump after completion of injection of containment spray and ECCS water, and all additives for reactivity control, fission product removal, or other purpose, should be maintained at a level sufficiently high to provide assurance that significant long-term iodine re-evolution does not occur. Long-term iodine retention is calculated based on the expected long-term partition coefficient. Tha 4 a c + = a + = naou Winwr-ti-t-i-sa-
.coef ficients-given in Table 6,5,4 -14nd-F-igure4,5t2-1-may-be-used
.in the-absence-of suitable ~ data for- equil4br-ium iodine partit4en-coef#icientc. Long-term iodine retention ::ith = ;ignificant "e-a"c'utier may be assumed only when the equilibrium sump pH, af ter mixing and dilution with the primary coolant and ECCS injection, is 5 'above Ai4. This pH value should be achieved at the onset of the spray S ( recirculation mode. The material compatibility aspect of the long-term sump and recirculation spray soiutions is reviewed by the C"ES. uhec EM Soch G.hL
- h. Storage of Additives The design should provide facilities for the long-term storage of g sLL spray additives. These facilities should be designed such that the additives required to achieve the design objectives of the system are stored in a state of continual readiness whenever the reactor is The storage facilities g i g ~ ~ critical $ho~uladurDe g the design design R ;uchlife thatof the plant.
freezing, precipitation, chemical reaction, and decomposition of7dtiditives, are prevented. For Na0H storage tanks, heat tracing of tanks and piping is required whenever exposure to temperatures below 40 F is predicted. An inert cover gas should be provided for solutions that may deteriorate as a consequence of expo-sure to air.
- i. Single Failure The system should be able to function effectively and meet all the above criteria with a single failure of an active component in the spray system, in any of its subsystems, or in any of its support systems. TS: sy;tcr, is can;idered fun;tional ith respect to iodine remcval if it ia :epsble-of-del-ivering-th& design spray flow rate with the :dditin-concentration-wi-thin-the-acceptable-range as <ieter-
- xd :b:ve.-
l 2. Testing .;
I Tests should be performed to demonstrate that the spray systems, jas
\ installea', meet all design requirements for an effective iodinegicrubbing function. Such tests should include preoperational verification of:
~
6.5.2-5 Rev. 1 - July 1981
/
o __ - - . . _ - _ - _ _ _ _ _ _ _ _ - - _ _ _ - - - - _ _ - - _ _ - - _ _ _ .
t y b ca p c c pc%d: %c .] we k;c p h , ~ ym,v e n d. c + y .:
syng systv.t. on plo i. ,
s abse ch Lu .4. c %v% bcnyw j tecdv cdtdo -. 055tm 9fahc-T CWo up Ndeh,"
- a. freedom of the containment spray piping and nozzles from obstructions,
- b. capability of the system to deliver the required spray flow, and ,
- c. capability of the system to deliverh required spray additives,wnh4n th: :pecified range of concentration:. For a system whose performance is sensitive to the as-built piping layout, such as a gravity feed system, the testing should be performed at full flow.
- 3. Technical Specifications e6 The technical specification should specify appropriate limiting conditions )
foroperation(LCOs),tes , and inspections to provide assurance that l the system is capable of its design function whenever the reactor is criti-cal. These specifications should include:
- a. The operability requirements for the system, including all active and passive devices, as a limiting condition for operation (with acceptable outage times). The following should be specifically included:
- containment spray pumps,
- additivepumps(ifany), l
- additive mixing devices (if any),
- valves and nozzles, i
oM ( !
- additive quantity and concentration in phe-additive storage tanks, and A
- nitrogen or other inert gas pressure in the-aduitive storage tanks.
PeriodicinspectionandsamplingofthecontentsofIt additive tanks
\ b.
to confirm that the additive quantity and concentrations are within l 1 l the limits established by the system design.
)
- c. Periodic testing and exercising of the active components of the system and verification that essential piping and passive devices are free g of obstructions.
III. REVIEW PROCEDURES The reviewer selects and emphasizes aspects covered by this SRP section as appropriate for a particular plant. Thejudgmentofwhichareasneedtobegiven attention and emphasis in the review is based on a determination that the material presented is similar to that recently reviewed on other plants or that items of special safety significance are involved. The review of the fission product removal function of the containment spray system follows the procedure outlined below.
The reviewer cletermines whether the containment spray system is used for fission (
I product removal purposes. Chapter 15 of the SAR should be reviewed to establish whether a fission product removal function for the containment spray system is assumed in accident dose evaluations. If the containment spray system is not 6.5.2-6 Rev. 1 - July 1981 l
/
K--.--- - - _ - - - -- _.
l i s-wh 'M 5< bM ' l used for dose mitigation purposes, no further review is required The-CSB-reviews-the-heat-removal-and-hydrogen-sing-aspects -ofd, by the AEB.
he-containment.
spray-systens Tf7he-con inment spray system is designed to reduce the concentrations-of-fission produc s in-the containment, the capability of_the systesTo function effectively as a fission pro'Hirct remo. 1 system W Yiviewed. If, as a result of the review, system modifications ~a~re requ rede the AEB reviewer will advise the CSB of th_e_Jequired modifications for integration with "any-other requirements glaced-on th~e containment spray system. This is a coordinating revneirfunctio(
- 1. System Design l Review of the system design includes an examination of the components and design including:features necessary to carry out .g theg(e449e g e scrubbing function,
- a. Spray Chemistry The forms of iodine for which spray removal credit is claimed in the accident analyses (SAR Chapter 15) are established. Containment spray systems may be designed for removal of iodine in the elemental form (i.e. vapor), in the form of organic compounds and 'n the particulate\ s form. Sog regon\ cacM -fc c 6thte porikdcdc nswn p.%3 u t'k.
Gud dcQdf o . .p g p g gy [t The systems or subsystems required to carry out thep e4+a4 scrubbing function of the containment spray, such as the spray system, recircu-lation system, spray additive system, and water source are identified.
The design of the systems involved is reviewed in order to:
op k (1) Determinef6e chemical additive and 4.e-ascertain phe effectiveness
-cf the cdd0t4ve' for elemental and organic iodine removal, by-comparison +ith-additives--of-proven-ef-fectivenc;; (ccc-acceptance criteric in subsec-t4en41) er by review of- theoret4 cal-and-experi- ;
mental-verincations 4upplied-for ee additives.
(2) Ascertain that the range of additive concentrations is within the limits listed in the acceptance criteria of subsection II above or that adequate justification is supplied for the iodine removal and retention effectiveness for the range of concentra-tions encountered. The concentrations in the storage facility, the chemical addition lines, the spray solution injection, the containment sump solution, and the recirculation spray solution should be examined. The extremes of the additive concentrations should be determined with the most adverse combination of ECCS, spray, and additive pumps (if any) assumed to be operating, and a single active failure of pumps or valves should be considered.
-The AEB reviewer coordinates-this-review-aspect-with-the-CMEB which rev4ews--the-sterage Of th: : prey cdditive: under cub:cca l -tion !!I.1.'
yedNL l The AEB reviewer censults-w4th-the-CMEB +^ "^"&y that the spray and sump water solutEon stability, and the corrosion, solidification, and precipitation behavior of the chemical additives, have appropriately
( been taken into consideration for the range of concentrations encountered.
~
l 6.5.2-7 Rev. 1 - Juiy 1981
t ,
- b. System Operation The time and method of system initiation, including additive addition, j is reviewed to confirm that the acceptance criteria of subsection II '
above are met. Automatic initiation of spray-and : pray additm fMw, without mechanical delays or manual overrides, is required. Credit for immediate initiation is assumed if the system can be shown, by test, to deliver the spray solution through the nozzles within For those systems where the spray solution W p 90 seconds, post-LOCA.
is delivered after 90 seconds, post-LOCA, credit for spray removal 7 fliedine will be assumed to commence upon the time of actual flow through the nozzles. The system operation should be continuous until S
h t iedia: removal objectives of the system are met. If a switchover from the injection to a recirculation mode of operation is required
{
during this time period, the reviewer should confirm that all require-ments listed in the acceptance criteria, particularly those concerning spray coverage and solution pH, are met during the recirculation phase.
Manual switchover from the injection mode to the recirculation mode during the first 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> following the initiation of the spray system operation is not acceptable.
- c. Spray Distribution and Containment Mixing The number and layout of_.the spray headers used to distribute the spray flow in the containment are reviewed. The reviewer verifies _
that the layout of the headers assures coverage of essentially the g oc \
entire cross-section of the containment with spray, under minimum _i spray flow conditions. The effect of thefhigh temfe75ture ~alid pressure t
conditions in the containment on the spray droplet trajectories should i be taken into account in determining the area covered by the spray.
6 j
The layout of the containment,=d f:rnd ;=til: tier cyct=: (::fety-
! grade)-operating-after-the400A-are reviewed to determine if any areas of the containment free volume are not sprayed. The mixing rate due to natural convection between the sprayed and unsprayed regions of the containment, provided that adequate flow area exists between these regions, is assumed to be 2 turnovers of the unsprayed region (s) per hour, unless other rates are justified by the applicant; it i: 21:e en=d that forced air ventiletien systems-designed-to-operate-in -
the pect:ccident erv rcrert erve :fr at 50% of their dc;ign fl0w i
.t re+er.- The containment may be considered a single, well-mixed volume F -prc';id d the spray covers regions comprising at least 90% of the con-tainment volume and peev4ded;'h ventilation system is available for adequate mixing of any unsprayed compartments. i 1
- d. Spray Nozzles The design of the spray nozzles is reviewed to confirm that the spray i nozzles are not subject to clogging from debris entering the recircu-lation system through the sump screens.
- e. Sump Mixing The mixing of the spray water containing the chemical additive and water without additive (such as spilling ECCS coolant) in the contain- (
ment sump is reviewed. The areas of the containment which are exposed 6.5.2-8 Rev. 1 - July 1981 e ______m_ _ _ . _ _ _ . . _ _ . . _ _ . _ _ _ . . . _
i e i
to the spray but are without direct drains to the recirculation sump (such as the refueling cavity) are considered. The reviewer confirms that the required sump concentrations are achieved within the appro-priate time intervals. The long-term sump pH should be reviewed in regard to iodine re-evolution, using the criteria given in subsec- l tion II.1.g above.
l l
The equilibrium partitioning of iodine between the sump liquid and the containment atmosphere is examined for the extremey-cf the-additive concentrations determined above, in combination with the range of l
temperatures possible in the containment atmosphere and the sump solu- ;
i tion. The minimum iodine partition coefficient (H) determined for l these conditions forms the basis of the ultimate iodine decontamination 1 factor in the staff's analysis described below. See Reference F 8 for ag htcretigd : = % tier of iodine partition coefficients.
discune
- f. Storage of Additives 1 M
The design of additive storage tanks is reviewed by CMEB to estab-lish whether at tracing is required to prevent freezing or precipi-tation in the tanks. The reviewer determines whether an inert cover gas is provided for the tanks to prevent reactions of the additive with air, such as the formation of sodium carbonate by the reaction of sodium hydroxide and carbon dioxide. Alternatively, the reviewer verifies by a conservative analysis that an inert cover gas is not required.
- g. Single Failure The system schematics are reviewed by inspection, postulating single failures of any active component in the system, including inadvertent operation of valves that are not locked open. The review is performed with respect to the cdine removal function, considering conditions 4
that could result in too fast as well as too slow an additive injection.
- 2. Testing b5@ P '
At the construction permit stage, the containment spray concept and the proposed tests of the system are reviewed to confirm the feasibility of verifying the design functions by appropriate testing. At the operating license stage, the proposed tests of the system and its components are reviewed to verify that the tests will demonstrate that the system, as installed, is capable of performing, within the bounds established in the description and evaluation of the system, all functions essential for ef fective 14 dine- removal following postulated accidents.
3.
thse 9toba8 Technical Specifications The technical specifications are reviewed to verify that the system, as <
designed, is capable of meeting the design requirements and that it remains in a state of readiness whenever the reactor is critical.
- a. Limiting Conditions for Operation (LC0)
(
The LCOs should require the operability of the containment spray pumps, a11' associated valves and piping, the spray additive tanks including 6.5.2-9 Rev. 1 - July 1981 J
A_-_-__-_-_-._ - _ . . _ _ - -
t ' ,
i l< the appopriate quantity of additives, and any metering pumps or mixing devices.
- b. Tests i.
l Preoperational testing of the system,' including the additive tanks, pumps (if any), piping, and valves is required, as discussed above.
In particular, the preoperational testing should verify that the system, as installed, is capable of delivering a well mixed solution containing all additives with concentrations falling within the design margins assumed in the dose analyses of Chapter 15 of the SAR.
Periodic testing and exercising of all active components should include the spray pumps, metering pumps (if any), and valves. Confirmation ,
1 l that passive components, such as all essential spray and spray addi-tive iping, and any passive mixing devices are free of obstructions ou dle made periodically) The contents of the spray additive. tanks ould be sampled and analyzed periodically to verify that the concen-trations are within the established limits, that no concentration gradients exist, and that no precipitates have formed.
- 4. Evaluation 4
A calculation of theg.qv;n e_!ne removal gdueffectiveness 3 of the system is performed to establish the degree of ve4me- dose mitigation by the containment spray following the postulated. accident. The mathematical model used for this calculation reflects the preceding steps of the review. The analysis and assumptions are as follows: gy b (gM g by l.iw !
Anw<sFM i.9 o.s ApetoOnok .
- a. The amountsof,iedime assumed to be released to,the containment 50% cf th: n.rc icdine invcatcry. Thi; h;; th; cc pc;itica cf 95.5 % 4 alamantal, 2. 5% particulater-and 2.0% crg:ric. The amountsof icdin fnis - pkn airborne inside containment depends upon plate out on interior contain-ment surfaces, removal by the spray and action of other engineered safety features present, radioactive decay, and outleakage from the containment.
Sv.swT'@'
- b. The removal of ^iod.ma from the containment atmosphere by the spray is considered a first-order removal process. The removal coefficients A (lambda) for each fe*= ef iodine (i.e., elcrenta!, parti.culate, emd ^rganic) for each of the sprayed regions of the containment is 1 computed,by the methods.sych at tha digit 3 computer ;0dc $PIRT (Raf A)- Removal coeffic4ents--representing time-dependent c!: rents' 4^ dine wall plate-out are also calculated. The coefficients for spray removal and wall plate-out are summed,for e!crental iodine. The removal lambdas are used as input parameters into a computer model used for dose calculation. In ce"treet te previce practice, the coef#icient:
ce calculated de not have On arbitraey-ma*4:ur allewable value > hen
.ured in conjunction uith the escu ptier of 50% of the core icdiae s n u e n + n ,u < n 4 + 4 _,1 1,o 24.sn. nm.
A The maximum -21;; nt:1 iodine decontamination factor, DF, for the d containment atmosphere achieved by the spray system is determined from the-ee equation (Ref. 4):
, k 6.5.2-10 Rev. 1 - July 1981 e
i .
C. Fission Product Cleanup Models The reviewer estimates the area of the interior surfaces of the con-tainment building which could be washed by the spray system, the volurne flow rate of the system (assuming single failure), the average drop fall height and the mass-mean drop diameter of the spray from inspection of the information submitted in the SAR. The c
effectiveness of a containment spray system may be estimated by consideration of the chemical and physical processes that could occur during an accident in which the system operated. Models containing such considerations are reviewed on case-by-case bases. In the absence of detailed models, the'following simplifications may be used:
All available experiments (Refs. 6 and 7 ) and computer simulations of the chemical kinetics involved (Ref 8) show that the most important j factor determining the effectiveness of sprays against elemental iodine vapor is the concentration of iodine in the sprayed solution.
For fresh sprays having no dissolved iodine, solutions have approximately equal effectiveness regardless of their pH and chemical redox potential (Ref 9). Solutions having dissolved iodine, such as recirculated sump solutions following an accident, may revolatilize i iodine if acidic (Refs 5 and
't .,
-10). Any chemical additive in the spray solution has no significant effect upon aerosol removal.
1.) Elemental iodine removal during spraying of fresh solution.
During injection, the removal of elemental iodine by wall deposition may be estimated by
\, = % A/V Here,kisthefirst-ordersprayremovalcoefficienttobeusedinthe dose assessments in Chapter 15 of the SERs, A is the wetted surface area, V is the containment volume, and Kg is a mass-transfer coefficient. 'All available experimental data are conservatively enveloped if K, is taken to be 4.9 meters per hour (Ref 11 pcge 17).
During injection, the effectiveness of the spray against elemental iodine vapor is chiefly determined by the rate at which fresh solution surface area is introduced into the containment atmosphere.
The rate of solution surface created per unit gas volume in the containment may be estimated as (6F/VD), where F is the volume flow rate of the spray pump, V is the containment volume, and D is the mass-mean diameter of the spray drops. All experimental data are conservativelyenvelopedifk,thefirst-ordersprayremoval coefficient, is taken to be (Ref 12) s GKTF 5
\'D l
7_
')
a and if Kg, the gas-phase mass transfer coefficient,'is assumed to
.be 3m/ min. T is the time of fall of the drops, and may be estimated by the ratio of the average fall height to the terminal velocity of the mass-mean drop.
(,istobelimited.to20 hour ~1 to prevent extrapolation beyond the existing data for boric acid solutions with a pH of 5 (Ref 6).
The sump solution at the end of injection is assumed to contain fission products washed from the core as well as those removed from the containment atmosphere. The radiation absorbed by the sump solution, if the solution is acidic, would generate hydrogen peroxide in sufficient amount to react with both iodide and iodate ions and raise the possibility of elemental-iodine re-evolution (Ref. 5). For sump solutions having pH values less than 7, molecular fodine vapor should be conservatively assumed to evolve into the containment i
atmosphere. (Ref 10).
The reviewer should consider all sources and sinks of acid or base that would occur naturally (e.g., alkaline earth and alkali metal oxides) or by design (e.g., alkaline salts or lye additives) in a post-accident containment. Any active spray additive system that is not automatic should be reviewed to assure that it is capable of performing its design function during either spray injection or recirculation or both, given a single failure.
- t. . .
For sequences during which the sprays would begin recirculation of the sump. solution prior to releases of fission products into the containment, credit is given from the~beginning of the release for any spray additive either dissolved from storage baskets in the sump or 1
added by manual or automatic initiation of an engineeered safety feature additive system. The spray should be assumed to be free of dissolved fodine until half of the sump solution volume has been recirculated following the beginning of fission product release.
The first order removal coefficient for molecular iodine may be j
calculated either by a staff contractor computer code such as described in reference 8, or by methods described as the " realistic model" in reference 11.
- 3. Organic iodine It is conservative to assume that organic iodidesare not removed by either spray or deposition. 'Radiolytic destruction of iodomethane may be modelled, but such model must also consider radiolytic production. Engineered safety features designed to remove organic iodides are reviewed on a case by case bases.
l
- 4. Particulate .
The first-order removal coefficient for particulate may be estimated by
=-
3h( /.E p
h K ? IV (oi o
s .
l i l
Here, h is the fall height of the spray drops, F is the spray flow and E/D is the ratio of a dimensionless collection efficiency to the average drop size. Since the removal of particulate material depends markedly upon the relative sizes of the particles and the drops, it is convenient to combine parameters that cannot be known It is conservative to assume (E/0) to be 10 per meter j (Ref. 11).
initially (i.e.,1% efficiency for 1 mm drops), changing abruptly to 1 per meter after the aerosol mass has been depleted by a factor of 50 (i.e., 98% of the suspended mass is ten times more readily removed than the remaining 2%).
4
_m____.__.________ )
V H -
DF=1+[c where:
H = equilibrium iodine partition coef ficient(s t< reimo c 9\
Vs = volume of liquid in containment sump and sump over flow Vc = containment net free volume less V s The maximum decontamination' factor for plain water, boric acid 00 DF is defined as the4in4+4el iodine concentration in the containment atmosphere, nh+=4nad uhan SnY c' the cere io dine i: d r, tant:n :=1y rolamead divided by the concentration of iodine in.the containment atmosphere at some later timeMcg deccdowcNim .
The effectiveness of the spray in removing elemental iodine shall be presumed to end at that time, post-LOCA, when the maximum elemental iodine DF is reached. Because the removal mechanisms are significantly different (and slower) for organic3 and particulate iodines, there is no need to limit the DF allowed in the analysis for these iodine forms.
IV. EVALUATION FINDINGS lohdG TWf's evaluation of the iodine removal effectiveness of the containme6t spray systems,.twuld include the following parameters, which are used in the thyroid dose calht4ans o a postulated loss-of-coolarjbacci~cient:
m overall first-order removal c6n ts pef. / '
hour) for elemental iodine, A 2.
for organic iodine A 2, and for 1cu - 'odine, A '
3-the effective sp volume, V (ft 3), s'N t ximum decontamination factor for elemental iodine, DF. '%
After the AEB reviewer determines that the containment spray -ad-gr2y addit 4"e system is effective #r ied He r=c'/21, the following can be reported in the staff's safety evaluation report (SER):
The staff concludes that the containment spray system as a fission product cleanup system is acceptable and meets the relevant require-ments of General Design Criterion 41, " Containment Atmosphere Cleanup,"
General Design Criterion 42, " Inspection of Containment Atmosphere Cleanup Systems," and General Design Criterion 43, " Testing of Contain- I ment Atmosphere Cleanup Systems." This conclusion is based on the following:
Qsp Qab u b N5(
TheconceptuponwhichtheproTosedsystemisbasedhasbeendemon-stratedtobeeffectivefor/4ndina =hearn+4^n and retention under postaccident conditions. The proposed system design is an acceptable 6.5.2-11 Rev. 1 - July 1981 n - . . _ . _ _ _ _ _ _ _ - _ _ . _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ - _ - - _ - - - -
e s
! application of this concept. The system provides suitable redundancy in components and features such that its safety function can be accom-plished assuming a single failure. The staff concludes that the ,
system meets the requirements of General Design Criterion 41. l The proposed pre-operational tests, post-operational testing and surveillance, and proposed limiting conditions of operatio_n for_the g g spray system provide adequate assurance that the W ' scrubbing Qd !
function of the containment spray system will meet or exceed the effectiveness assumed in the accident evaluation and, therefore, meets the requirements of General Design Criteria 42 and 43.
V. IMPLEMENTATION The following provides guidance to applicants and licensees regarding the staff's plans for using this SRP section. ,
l I
Except in those cases in which the applicant proposes an acceptable alternative method for complying with specifi&d portions of the Commission's regulations, the method described herein will be used by the staff in its evaluation of conformance with Commission regulations.
I. REFERENCES
- 1. 10 CFR Part 50, Appendix A, General Design Criterion 41, " Containment Atmosphere Cleanup."
- 2. 10 CFR Part 50, Appendix A, General Design Criterion 42, " Inspection of Containment Atmosphere Cleanup Systems."
- 3. 10 CFR Part 50, Appendix A, General Design Criterion 43, " Testing of
- Containment Atmosphere Cleanup Systems."
\
1 4. ANSI /ANS Standard 56.5-1979, "PWR and BWR Containment Spray System Design Criteria."
- 5. D. L. Reid, O. ti. Johnson, and A K Pc tmo, "Rc;carch en Removal-of-
{i Icdine by Containment-Speays-ecntaining Trace Lcveh--of Hydrazinc," Sattelle P;cific Northwest Laborat wic;, June 1979.
-E. ^ K Pcotm;, P -Rr---Sheeey,-and. P. S. T=, "Te:Melegical Bases for Mede!s
-of-Speay-Washout-of-Airborne Contr4nant: 4^ Centai" ment Vercels,"
l -N'JREC /CR 0000.
- 7. L. F. Parsly, " Design Considerations of Reactor Containment Spray Systems -
i Part IV. Calculation of Iodine Partition Coefficients," 0RNL-TM-2412, Part IV, Oak Ridge National Laboratory (1970).
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6.5.2-12 Rev.1 - July 1981
- 5. R.M. Sellers, A Review of the Radiation Chemistry of Iodine Compounds in Aqueous Solution, CEGB-RD/ BIN-4009, Berkeley Nuclear Laboratories, United Kingdom (June.1977).
- 6. R.K. Hilliard, A.K. Postma, J.D. McCormack, L.F. Coleman and C.E. Lunderman, Removal of Iodine and Particles From Containment Atmospheres - Containment Systems Experiments, BNWL -1244, .g Pacific Northwest Laboratories (February 1970).
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- 7. S. Barsali, F. Bosalini, F. Fineschi, B. Guerrini, S. Lanza, [' . y M. Mazzini and R. Mirandola, Removal of Iodine by Sprays in the j y 2-
- t. .
PSICO p Model Containment Vessel, Nuclear Technolooy 23, pages *3 146-156, (August 1974). je 7 y7 e E 1
- 8. M.F. Albert, The Absorption of Gaseous Iodine by Water Droplets, -i 2~
NUREG/CR-4081 (July 1985). 'J NI
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- 9. A.K. Postma, L.F. Coleman and R.K. Hilliard, Iodine Removal from qu9 -c [ :':
Containment Atmospheres by Boric Acid Spray, (July 1970). a -
vff
- 4;
- 10. A.0. Allen,TheRadiationChemistryofWat(andAqueousSolutions, l; I?j f' -
Van Nostrand, New York (1961).
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- 11. A.K. Postma, R.R. Sherry and P.S. Tam, Technological Bases for [
Models of Spray Washout of Airborne Containments in Containment t.
Vessel, NUREG/CR-0009 (October 1978). ,b A
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- 12. R.E. Davis, and M. Khatib-Rahbar, Fission Product Remval Effectiveness p.fChemicalAdditivesinPWRContainmentSprays,TechnicalReportA37 -
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6 7 8 9 10 11 Spray pH Fig. 6.5.2-1 Partition Coefficient vs. Spray pH For Solution Containing Sodium Hydroxide (Ref. 4) 6.5.2-13 l
Rev. 1 - July 1981 '
t' l-
. REGULATORY ANALYSIS OF THE AUTOMATIC ACTUATION OF SYSTEMS FOR CHEMICAL ADDITIONS TO CONTAINMENT SPRAY AND SUMP SOLUTIONS
- 1. Statement of the Problem - At most pressurized water reactors having large dry containments, the initiation of containment sprays also initiates the automatic addition of either hydrazine or sodium hydroxide.
into the boric acid spray solution. In those plants in which sodium hydroxide is added to the spray, three purposes are met: 1) the scrubbing of elemental-iodine vapor'from the containment atmosphere is enhanced, 2).the evolution of dissolved iodine from_ containment sump
.is diminished, and 3) the long-term corrosive effects of hot boric acid on equipment are avoided. In those plants in which hydrazine is added to-the spray, only the first purpose is _ met, and the second and third are accomplished by storing a solid alkaline salt, trisodium phosphate, in baskets in the sump to be dissolved by the boric acid sprays. In either case,. sufficient alkali or alkaline salt is supplied not only to neutralize the boric acid, but.also to render the sump recirculating spray i solution slightly alkaline. The resulting solution is similar in both boron concentration and basicity to that resulting from melting the borated ice in plants having ice condenser containments.
Automatic addition of hydrazine or sodium hydroxide is based upon i Regulatory Guide 1.4, " Assumptions Used for Evaluating the Potential. i Radiological Consequences of a Loss-of-Coolant Accident for Pressurized i Water Reactors,". Regulatory Position C.1.a. which states " Twenty-five l percent of the equilibrium radioactive iodine inventory developed from-maximum full power operation of the core is immediately available for leakage from the primary containment." This position flows from the TID-14844 assumptions ' referenced as a point of departure in 10CFR100.
As implemented by Standard Review Plan (SRP) Sections 6.5.2 and 15.6.5, Appendix A, radiciodine is assumed to begin to escape from the contain-ment inrnediately, being diminished only as the sprays reduce .the radio-iodine concentration within the containment atmosphere. In many instances, the off-site thyroid doses calculated using SRP guidance are due predominantly to iodine releases in the first few minutes of the accident.
It has-long been recognized that immediate release of fission products cannot occur, and that in any core damaging accident containment sprays would be initiated at least several minutes prior to the transport of radiciodine from the reactor fuel into the containment,
, The sole reason for automatic initiation of spray additives has been to counter very rapid release of large amounts of elemental iodine vapor postulated to.be instantaneously released into the containment atmosphere.
It is now expected that much smaller quantities of elemental iodine could be released, and that these quantities would enter the containment atmosphere at later times during core-damaging accidents. Consequently.
a, ,
2 the need for automatic initiation of the additives no longer exists.
Furthermore, all existirg information indicates that for fresh spray solutions having no dissolved iodine, the spray removal capability is virtually independent of the pH of the solution. Hence, the benefits The of the additives themselves are much less than previously supposed.
disadvantages of spray additive systems, which include the costs of maintenance including periodic replacement of chemicals, and the hazards to personnel and property from accidental spillage or spraying of the additives can no longer be easily justified. ;
I
- 2. Consequences The consequences of this change are judged to result in no change in safety significance in terms of public risk. Since research results referenced in the draft revised SRP indicate that fresh spray removal capability is virtually independent of the pH of the solution, the effectiveness of the spray in dose mitigation will not be reduced, provided appropriate post-accident pH control of the containment sump solution is maintained. In addition, operational safety will he improved by elimination of hazards to personnel and property from accidental spillage or inadvertent spraying of additives and by reduced maintenance.
- 3. Alternatives - Because of design differences, the preferred alternative-will vary widely among licensees. Three general alternatives are presented below, each with a discussion of the dependence of its costs and benefits upon variables of plant features; a) No change - This alternative would continue the following present dysbenefits: The costs of maintenance, testing and purchase of replacement additive are estimated to be between $10,000 and $100,000 per unit-year. The financial risk of plant damage caused by inadvertent actuation or the use of sprays during non-core-damaging accidents might be large compared to
$10,000 per year for those plants having sodium hydroxide spray additive. No monetary value is assigned to personnel hazards from inadvertent initiation, but licensee concerns over such a situation are considered significant. Downtimeandcleanupcoststhatcogid result from 0.01 inadvertent initiations per reactor year at 10 1 dollars per clean-up are $10,000/ reactor-year.
For those plants at which it is possible to add chemical to the spray at any time or at which neutralization by i
trisodium phosphate stored in sump baskets will occur, l there are no identifiable advantages to this option.
For those few plants at which the sodium hydroxide additive can be injected into the spray only during the early period of containment spraying, when boric acid is being withdrawn from the refueling water storage tank, there is an advantage to this alternative in that the likelihood of failure to neutralize the boric acid solution following an accident is essentially evoided, Such although there would be no reduction in maintenance costs.
below, and are plants could, however, profit by alternative c.,
discussed further under that alternative.
4
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~For those plants that do not have a containment spray additive system,-there is no cost.to this alternative.
b). Delete automatic actuation-of spray additive system - For those plants that are capable of adding sodium hydroxide only during initial injection and not during spray solution recirculation, this alternative would introduce the risk-of failure to neutralize the boric acid due to operator error. Such plants would be unlikely to elect this option over c., below.
For those plants capable of sodium hydroxide addition during recirculation, there could be small reductions in the costs of maintenance and testing, and avoidance of the financial M sk of plant damage caused.by inadvertent actuation. There would also be'small licensing costs in documenting changes and modifying
-technical specifications.. No reduction in the benefits of the additives would occur.
c) Delete spray additive system.- There would be a complete elimination of the costs of maintenance and testing and of the risk of spills and inadvertent. actuation. For plants which. rely upon trisodium' phosphate to neutralize the boric acid sprays, there would.be no reduction in the benefits-of acidity control, while between $10,000 and'$100,000 per unit-year would be saved in maintenance and.testingL If TSP. baskets were needed as replacement pH control, the savings would be reduced by about
$5,000 per unit-year and by $50,000 to $100,000 initial expense, which are the estimated of costs of periodic chemical renewal.and sump basket installation, respectively. All plants could have small licensing costs. NRC costs for review of submittals supporting system deletion are estimated at about one person-month per plant, about $10,000.
4.. Information Collection Requirements Table 1 lists all licensees and applicants having pressurized water
. reactors, and identifies those plants also having automatic injection of hydrazine or sodium hydroxide into their containment sprays. Plants having automatic addition of those chemicals would be informed of the revised staff position, and could consider either replacing auto-matic addition with an acceptable procedure to assure proper manual actuation, or eliminating the additive system.
No duplications with other collections of information are foreseen, and no consultations with other parties are considered necessary.
- 5. Impacts on Other Requirements This proposal is not intended to displace any safety-related backfits or plant modifications needed to improve safety.
- 6. Constraints There are no identifiable constraints to implementation, except those plant-specific constraints discussed under each alternative.
_ x __
_,.7_
4
- 7. Decision Rationale As discussed in Sections 1 and 2, above, there are bases for expecting that pressurized water reactors having automatically actuated containment spray additive systems will demonstrate that these systems may be modified to provide either improved safety function or equivalent safety function at less cost. This proposal will permit affected licensees to investigate the possibility of modifications to achieve improvements or savings and to submit proposals for implementation where they are found to be-advantageous.
- 8. Implementation Changes in the Standard Review Plan are presented in draft form in Attach-ment A. This proposal is one of a series flowing from source term research results. This series of regulatory revisions was identified in a Commission Information Paper, SECY 86-76, along with a schedule for further imple-mentations.
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r Containment Sprays In the event of a loss of coolant accident, many PWRs are equipped with spray Since the systems to condense steam from their containment atmospheres.
sprayed liquid would necessarily mix with any spilled reactor coolant and might.be later recirculated into the reactor, the liquid used must contain a neutron absorbing solute. In all U.S. PWRs, the spray solution is the This refueling water normally stored in tankage betwen refueling outages.
solution is about 0.2 M (M= molar, or moles per liter) in boric acid (orthoboric acid, H3B03 ).
Boric acid is a weak acid, meaning that it is only partially dissociated in aqueous solution. This dissociation can be written as:
~
.M3 60 3 F [ + QO & (3) 10 M at 20'C, such The equilibrium constant for this dissociation is 5.3 x 10 At that a 0.2 M solution has a pH of 5. The pH of pure water is 7.0 at 25 C.
higher temperatures greater fractions of both water and boric acid will dissociate. At 90 C, for example, pure water has a pH of 6.1, rather than 7.
The dielectric constant of water diminishes with increasing temperature, how-As ever, which acts to counter the tendency of increase solute dissociation.
a result of these conflicting temperature variations, the pH of 0.2 M boric acid has a minimum at 77*C of about 4.9. (see, e.g., R.W. Gurney Ionic I
Processes in Solutions, McGrau Hill, 1953) ;
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To prevent corrosion of metals other than stainless steel that might be exposed to containment sprays, it is usual for some basic material to be stored for dissolution into the sprayed solution to neutralize the boric acid. The two bases used for this purpose are trisodium phosphate-(TSP, Na PO 12H 0) ar.d sodium hydroxide (lye, Na0H). TSP is a powder 3 4 2 similar to dishwater detergent in consistency and solubility, and lye is stored as a 30% solution by weight. As purchased, TSP contains some impurities which lead to " caking" in humid atmospheres. Lye solution reacts with atmospheric carbon dioxide to form a sodium carbonate precipitate and must be stored in tanks with nitrogen-filled ullage.
In a typical PWR containment spray system, the spray and the ECCS share the refueling water, and can drain this supply in 20 to 45 minutes. Plants using TSP keep it stored in open baskets in the containment sump where it may be dissolved by the falling spray. Plants using lye are more diverse.
Some can add the lye solution into the spray both during the initial draw-down of the refueling water storage tank and during the recirculation of the solution from the sump back into the spray system. Other plants can only mix lye with refueling water and cannot add it during recirculation.
Other processes that may be expected in a containment following an accident can also affect the pH of sump and spray solutions. Chief of these would be the dissolution of pretransition element oxides and hydroxides in these I
solutions. Examples would be the rubidium, cesium, strontium and borium fission products, and calcium, sodium and potassium from concrete which
o .
3 would be volatilized as strong or moderately strong bases. Of lesser importance-would be the effects of carbon dioxide from concrete abletion and nitrogen oxides from air radiolysis, which would produce smaller potential amounts of acids. A trivial effect would be the acid generated by iodine hydrolysis and oxidation. For example, the acid produced by the air oxidation of iodine to the thermodynamically preferred iodate, if all the core inventory were involved, would be less than 0.1% of the equivalence of the boric acid.
602. +%.I A + %l4 L o e 4 Io3+Y (2)
Overall, these other processes are estimated to produce a neutralizing effect upon the boric acid, generally supplying more base than acid.
In addition to preventing corrosion, the boric acid is neutralized to enhance the dissolution into the spray solution of any iodine-containing vapors dispersed into the containment atmosphere. Although reaction (2), above, is favored .in overall equilibrium, it is very slow in occurring and could taken many hours to approach equilibrium. In addition, radiolytic processes due to the effects of ionizing radiation on the sump and spray solution are capable of producing iodine-containing gases that might evolve into the containment atmosphere. Chief amongst these radiolytic processes is the production of hydrogen peroxide (H 22 0 ) by water irradiation in the presence of air.
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-- 4 Althouch it was conservatively assumed in Reg. Guides 1.3 and 1.4 that fission product iodine would be released as molecular iodine vapor (1 2 )'-
other processes that'would be expected to occur within a containment after an accident would limit the occurrence of 12 . Any accident that might
! release iodine into'the containment atmosphere would necessarily also release noble gas tission products. These Krypton and Xenon isotopes, 8
amounting to as much as 7 x 10 Ci, transmute to rubidium and cesium isotopes,.respectively, upon decay. For the release of the core inventory 14 such of noble gases into a large PWR containment, there would be 8 x 10 decays per cubic meter per second occurring'in the early hours of the accident. Each alkali meta'l atom produced in the containment atmosphere would recoil from the decay as a highly charged cation, and as a result of the action of its electric field upon the dipoles of water molecules present as vapor, would create a small, highly basic aerosol particle.
This process would neavily deplete any molecular iodine vapor also present.
Any core-damaging accident would be likely to release hydrogen gas as well as iodine. The reaction between molecular iodine and hydrogen, while less exoergic than that between oxygen and hydrogen, proceeds rapidly without the necessity of a large activation energy (ignition).
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The product, hydrogen iodide (hydroiodiacid, HI) 1s easily oxidized by air to reform iodine 01 +9 HI @ 1ko+1R - g)
The net result is the catalytic oxidation of hydrogen. Note, however, that any molecular iodine present would spend some fraction of its time as hydrogen iodide, subject to ready solution or other depletion. . Hydrogen iodide is a very strong acid, being virtually totally dissociated in aqueous solution.
Molecular iodine is a comparatively unlikely substance to be made in fluids in which iodine is in low concentration. This is because the formation of 1
must necessarily involve the collision between two moieties each containing 2
a single lodine atom. If iodine atoms are very rare, then it is more likely that they will react with other components of the mixture prior to undergoing l a rare collision amongst themselves. This may be seen in the experimental results ot spray experiments at varying iodine concentrations in Y. Nishyawa, S. Oshima and T. Maekawa, " Removal of Iodine from Atmosphere by Sprays,"
Nuclear Technology 10, pp 486-98, April 1971. These results show that as i
the iodine concentration is decreased,.both the rate of molecular iodine i dissolution and the fraction dissolved increased markedly.
l, l
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As e example, consider the iodine hydrolysis reaction discussed in J.T. Bell, M.H. Lietyke and D.A. Palmer, " Predicted Rates of Formation of Iodine Hydrolysis Species at pH Levels, Concentrations and Temperatures Anticipated in LWR Accidents," NUREG/CR-2900, October 1982.
I 2 +R 2O O I'+ 14* + HOI (3)
This reaction is, in effect,-first order in 1 , 2since the concentration of water in aqueous solutions is virtually unchanged by the reaction proceeding to the right. The reverse reaction is first order in hydrogen ion, but It is apparent that unless depends upon the product of two iodine species.
the total of all iodine species concentrations is large compared to the nydrogen ion concentration, the net hydrolysis rate will depend more markedly upon the local iodine concentrations than upon the pH.
Of much greater importance to the chemistry of iodine in a post accident The environment is the potential for reaction with radiolysis products.
radiolysis of water has been described by the equation.
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(6) 4.9 (o a 0..h + 2.3 ot4 +1.961$ o.10ti+ o.9tH +. . 1
- t 0.15 (0 + 0.6 H second, i.e., the in equation 6, the coefficients are "G-values" at 10-7 molecules destroyed or created per 100 electron volts of deposited ionization
_mu.__ ____-__. - - _ _ _ _ _ _ _ _ _ _ _
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energy ..The G-values decrease markedly with time after a pulse of ionizing radiation as'the short-lived species on the right-hand side of equation 6 6
In a radiation field of 10 Rads / hour,.
reunite to form water molecules and heat.
equation 6 estimates that 2 x 10-7 moles per liter per second of hydrogen peroxide are produced by water radiolysis.
The British CEGB has produced a critical review of the literature in R.M. Sellers, "A Review of the Radiation Chemistry of Iodine Compounds in Aqueous Solution,"
RD/B/N4009, June,1977. The available literature shows that molecular iodine production in iodide solutions under radiation is quite small unless either the pH is less than about 4 or the concentration of iodide is much larger than 10-3 M. E.C. Beahm, W.E. Shockley and 0.L. Culberson " Organic lodide Formation Following Nuclear Reactor Accidents," NUREG/CR-4327 show that iodomethane production in iodide solutions being sparged by argon-methane gas is similarly In both cases, there is no much greater at pH of 6 or less than at higher pH.
firm evidence that more alkaline solutions would greatly improve iodine retention.
Iodine is also known to catalyze the decomposition of hydrogen iodide by the net effect of the two following reactions:
1 Ro t+ af+7-.fe 2.M to + .r7 (7) >
~
Ro t + It;# AI + W+o L
8 Under acid conditions the These are called the Harcourt-Essen reactions.
n the first becomes taster such that each iodine atom spends more time as 12 ,
When the hydrogen peroxide average, before reactina by the second equation.
is made radiolyticly, however, the effect of pH is less clear cut, due to the likelihood of competing reactions of other species in reaction (6.) as well as trace containments.
C.C. Lin, " Chemical Effects of Gamma Radiation on Iodine in Acueous Solutions,"
Journal of Inorganic and Nuclear Chemistry 42, 1101-7, 1980, reports that s1gnificant molecular iodine production occurs by radiolysis at pH value below 4, with progressively less occurring at higher pH values. Lin's experiments were performed while the sparging of the solutions with helium, which might be considered to imitate the evolution of noble gas daughters expected in a post-accident sump solution. At values of pH above 8, radio-lytic reduction of iodate was observed. In general, neutral solutions (pH=7) were about as effective as alkaline solutions in retaining iodine in non-volatile forms.
S. Barsali et.al., " Removal of Iodine by Sprays in the PSICO 10 Model Containment Vessel," Nuclear lechnology 23, pp 146-56, August,1974 reported a series of twelve spray tests using either tap water or 1% sodium thiosulphate 5 0 ). They concluded that "the elemental iodine removal solution (Na223 half-times obtained by spraying service water do not differ greatly from those found by spraying thiosulphate solution. The sprayed solution was, in some cases, recirculated for a period ranging from 1 to 11 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br /> without any
9 Some runs were performed with fractions release of iodine to the atmosphere.
The elemental iodine removal -l of the model containment vessel not sprayed.
half-times in the sprayed and unsprayed regions do not essentially differ."
These University of Pisa experiments were at spray solution flow rate to sprayed volume' ratios less than those in U.S. PWR containment spray designs.
R.E. Davis and M. Khatib-Rahbar, " Fission Product Removal Lttectiveness of-Chemical Additives in PWR Containment Sprays," BNL Technical Report A-3788, October,1986, reviewed the literature and concluded that for all cases of interest the rate of iodine removal by sprays during refueling water injection In such was limited by gas transport of iodine to the surface of the drops.
cases, the composition of the spray solution itself does not have a great effect upon the rate of removal unless the solution contains dissolved Should the solution have a significant dissolved molecular elemental-iodine.
iodine concentration, then its re-evolution could compete with the reverse process of iodine dissolution.
Henry's Law (Joseph Henry, 1797-1878) states that the ratio of the concentration of a substance in a gas phase to that in a liquid phase at equilibrium is a tunction only of temperature. Henry's Law holds only for true solutions of non-reactive gases, and does not hold for the ratio between iodine vapors in the gas phase to the concentration of iodine hydrolysis products in the liquid phase. The existing SRP 6.5.2 assumes that a
" partition coefficient" exists for iodine in equilibrium between air and borate solutions which is a function only of the pH of the solution (Figure 6.5.2-1). There is, however, no experimental evidence that the rate of l dissolution of iodine vapor into borate solutions is chiefly dependent upon pH, and no theoretical reason to suppose that such might be the chse.
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'In the early years of this century. A. Einstein computed a simple relationship 2
between the mean' square displacement of an atom {r ) during time. interval t and the diffusivity.D of that atom.
M 2.D t- (8)
I the diffusivities of molecular iodine and its hydrolysis products in hot
-5 2 Spray drops of about aqueous solutions are between 2 and 5 x 10 cm /sec.
0.1 cm diameter require several seconds to fall through a typical PWR containment. It follows trom these comparative magnitudes that only the smallest of. spray drops are capable of being diffusively mixed during their.
time of fall.
Larger drops could be mixed by other mechanisms than diffusion, as, for example, by convective flows.
.In addition, due to the greatly different fall velocities of drops of different sizes,.the collision and agglomeration among Nonetheless, drops will also lead to mixing, both between and within drops.
it'is not assured that all spray drops will be a equilibr1um or steady state with respect to iodine during their fall, even if they do approach thermal equilibrium with steam.
Current models of core melt accidents predict that fission product iodine released into the containment in an accident will be released over a time span of at least tens of minutes, and that there will be a delay between the release !
In addition, that iodine of steam and that of iodine of at least ten minutes.
which is released is more likely to be in the form of an iodide in aerosol than as molecular vapor.
11 We conclude that there are no compelling reasons to adjust the pH of containment sprays prior to the recirculation of the sprayed solutions, and that there are likewise no compelling reasons to adjust recirculated solutions to a pH of much above 7.
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TECHNICAL REPORT A-3788 8-12-86 FISSION PRODUCT REMOVAL EFFECTIVENESS OF CHEMICAL '
ADDITIVES IN PWR CONTAllMENT SPRAYS i
R. E. Davis, H. P. Nourbakhsh, and M. Khatib-Rahbar Accident Analysis Group Department of Nuclear Energy Brookhaven Naticnal Laboratory Upton, NY. 11973 August 1986 l
Prepared for U. S. Nuclear Regulatory Commission Washington, DC 20555 -
Under Contract No. DE-ACO2-76CH00016 .
FIN A-3788
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1 ABSTRACT 1
~ The presence of gaseous iodine in severe accident situations is based )
upon a regulatory source term prescription whose basis predates the accident at'^Three Mile Isl and-Unit 2 and the source term research that TMI-2 stimulated. This report reviews the current best-estimate of source term characteristics, and the experimental bases that establish the effectiveness i of spray additives. Based on this review, several current operating practices, vis-a-vis the addition of additive (s), may warrant regul atory i I
reevaluation.
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-iv-ACKNOWLEDGEMENTS The authors would like to thank Dr. J. Read (NRC) for the guidance he provided during the course of this effort. In addition, the authors appre-ciate the skillful preparation of the manuscript by Ms. Cheryl S. Conrad and Ms. Theresa Skelaney.
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-v-CONTENTS Page ABSTRACT................................................................ iii~
ACKN0WLEDGEMENTS........................................................ iv LIST OF FIGURES......................................................... vi LIST OF TABLES.......................................................... vi
- 1. -INTR 000CTION........................................................ 1
- 2. PAST AND CURRENT SOURCE TERM CHARACTERISTICS........................ 3
- 4. SPRAY N0DELS........................................................ 13 4.1 An al yt i c al P roc ed u re . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.2 Reev al u ation of Exi sti ng Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
- 5. DISCUSSION AND CONCLUSION........................................... 19
- 6. REFERENCES.......................................................... 23 APPENDIX A.............................................................. A-1 APPENDIX B.............................................................. B-1 9
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-vi-I LIST OF FIGURES Figure Title Page 1- Comparison, for Zion, of the airborne aerosol' mass suspended in containment with and without containment sprays.............. 6 2 Comparison for Surry of the airborne aerosol mass suspended in containment with and without containment sprays.............. 7 3 Removal constant versus normalized, new drop surf ace area; fresh spray data................................................ 17 LIST OF TABLES Table Titl e Page 1 Summa ry lof CSE F i rst S p ray Resul ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2 Sumna ry of PI SCO Fi rst Spray Resul t s . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3 Summa ry Res ul ts of J AER I Te st s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
- 1. INTRODUCT10N Commercial pressurized water reactors (PWR) are equipped with Containment
/ Spray Systems (CSS) to limit the peak pressure in containment below the design pressure in the event of a blow down associated with a design basis accident.
The CSS is composed of spray pumps, spray rings, nozzles, and necessary pipes and valves. Coolant is supplied by the Refueling Water Storage Tank. Many CSS are also equipped with a spray additive tank and an associated pump.
These additives are intended to increase the capacity of the coolant to absorb gaseous iodine in the event of fuel clad failure or core melt. Hence, an important secondary function of the CSS is the attenuation of fission products released to the containment. Section 6.2.2 of the Standard Review Plan (SRP)1 describes the performance objectives of the CSS as a heat removal system, ;
while SRP 6.5.2 addresses the function of the CSS as a fission product cleanup system.
The performance objective of CSS as a fission product cleanup system, given the source term assumptions given in Regulatory Guide 1.4,2 coupled with the containment leakage rate is tg aid in meeting the design basis accident (DBA) dose guideline of 10CFR100. The basis of source term prescription given in Regulatory Guide 1.4 is given in Reference 3. The source term con-sists of 100% of the noble gases (Xe, Kr), 25% of the iodine and 1% of other sol ids . lodine is assumed to be primarily gaseous based on the observed release f rom the Windscale accident. (Regulatory Guide 1.4 further prescribes the following iodine chemical composition: 91% elemental, 5% particulate, and 4% organically bound). The Atomic Energy Commission adopted this source term to establish criteria for licensing of plant / site combinations and assessing the potential hazard to the public. The use of this hypothetical source term, which would be' associated with substantial core damage to assess the conse-
_ quences of a DBA, which should not result in any substantial core damage since the Engineered Safety Features (ESFs) should terminate the accident prior to core damage, was viewed as intentionally conservative. Application of this approach led to the conclusion that gaseous iodine dominated the off-site radiation doses. This in turn led to increased efforts to scrub iodine from the containment atmosphere, including the use of a chemical additive to increase the effectiveness of the sprays to absorb and retain gaseous iodine.
On March 28, 1979, Three Mile Isl and Unit 2 experienced a partially mitigated loss of cool ant accident. Substantial core damage occurred and significant amounts of radionuclides were released from the f uel .
Environmental monitoring of the accidental releases indicated 0.02 to 0.08 of the nobl e gas inventory and only 3x 10-7 of the iodine inventory were released to the environment. No metallic radionuclides are known to have been rel eased . The difference in the fractional releases of noble gases and iodine were attributed to the following:
.1. Noble gases are inert, volatile, and only slightly to fairly soluble <
in water. -
- 2. The chemically reducing environment in the reactor vessel promotes the stability of cesium iodide which is nonvolatile (in the containment atmosphere) and water soluble.
t
- 3. Injection of sodium hydroxide into the CSS would have enhanced the absorption of gaseous iodine if it was released during the accident.
- 4. . Filters ef fectively trapped iodice in the auxiliary fuel handling building from which environmental releases occurred.
The. inference that the majority of iodine released from the TMI-2 reactor vessel was Cs1 and not molecular iodine focused attention upon the TID-14844
source term. assumptions and .the measures taken in response to these assump-tions, e.g., the design of the engineered safety features.
This report focuses on the technical data base that is available to sup-port the use of chemical additives in the CSS. Computer searches of several literature data bases were also carried out to identify relevant materials.
These searches are documented in Appendix A.
I i
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I
- 2. PAST AND CURRENT SOURCE TERM CHARACTERISTICS Regulatory Guide 1.4 prescribes that the following source term be con-sidered, for example, in assessing the DBA doses guidelines values set forth in 10CFR100:
l 100% of the noble gas inventory, 1.
- 2. 25% of the iodine inventory; Composition - 91% molecular, 5% particu- !
late, 4% organic.
- 3. Release to the containment assumed to be instantaneous and well mixed in the containment atmosphere.
NUREG-0772 addressed the impact of source term assumptions on regul ation.s Specifically, the impact of the observation that particulate Csl )
and not gaseous 12 was the predominant chemical form of iodine released to '
containment was assessed. Based upon the analyses presented in NUREG-0772, it would appear that except for those accidents in which the fission products are released through water, the amount of iodine calculated to be released would not be substantially reduced by the chemical form (1 2 or CsI).
l As a result of the observations of radionuclides released at TMI, sub- !
stantial research efforts were initiated. An effort sponsored by the NRC has resulted in a set of computer codes, the Source Term Code Package (STCP),
which simulates the progression of covere nuclear reactor accidents and esti-mates the release of materials from the fuel, through the reactor coolant sys-tem and to the environment. The function and status of these codes are described a NUREG-0956: 6 some typical results of the code package and pre-
_ liminary observations regarding accident source terms are also presented. in addition, the basis of STCP methodology has been reviewed by a study group of ,
the American Physical Society. While this review understandably noted many areas of uncertainty and identified several phenomena not fully analyzed, it generally concluded that considerable pro cation of the Reactor Safety Study (RSS).gress has published (The RSS, been made sincealso in 1975, the publi-predicted substantial releases of gaseous iodine to the containment, and was more or less consistent with the Regul atory Guide 1.4 Source Term Prescription.)
In comparison to the Regulatory Guide 1.4 source terms, several substan-tial differences exist in regard to the characteristics of the fission product (FP) release predicted by current, state-of-the art methods of source term estimation. These characteristics have been described elsewhere, e.g., see References 7 and 8. A brief summary of the characteristics is given below.
The total release of FP material to the containment can be divided into two distinct phases: the initial, in-vessel phase where material is released l from the damaged or melted fuel and the ex-vessel phase where material 'is I
released from the core / concrete interaction. In the in-vessel phase, the release is domi nated by nobl e gases ( -100% release), cesium (-100%),
iodine (-100%), and tellurium (-30-70%), which are rather vol atile at the '
j temperature excursions predicted during core degradation. Very much smaller amounts of the ref ractory groups, Ba, Sr, Ru, La, and Ce, are predicted to be released in-vessel . As the volatile materials, with the exception of the
i noble gases, migrate away from the core to cooler regions in the reactor cool-ant system (RCS), they are ' assumed to condense on surf aces or onto aerosols.
Based upon observations made at TMI-2, and subsequent thermochemical analy-ses,5 iodine is assumed in the STCP to be present as Csi, and any iodine release from the RCS is modeled as an emission of Csl in aerosol form. The behavior of aerosols released from the RCS can be modeled in several alternate fashions which depend upon the particular type of reactor and sequence being considered. For BWR sequences, where the RCS ' blowdown is vented through a suppression pool,9 aerosol decontamination factors (DF) are calculated by SPARC, a computer code within the STCP. Simil a rly, for PWR's equipped with
. ice condensers, the ICEDF code within STCP is executed to estimate aerosol DF's associated with this ESF. Ultimately, the behavior of aerosols in the containment atmosphere is simulated by the code NAVA-4 This code models several natural processes, e.g. aerosol agglomeration and settling, that can deposit airborne aerosols onto reactor surfaces and, hence, result in a decrease in the airborne activity. The duration of the in-vessel FP release is limited to the period from -the start of core degradation to bottom head failure. . The onset of core damage is plant and sequence dependent. Typical estimates of the times for the start of core melt are 25 minutes, Surry AB sequence, and 135 minutes, Surry S 2 D,8 from the time of scram. In the AB sequence, the CSS is assumed to fail. In the S D 2 sequence, the CSS is opera-tional, and sprays initiate 20 minutes after scram. It is interesting to note that by the time the release of FP's has begun, the CSS has already entered the recirculation mode. It should be noted that current regulatory guidance effectively requires immediate injection of additives into the sprays, once the CSS is initiated.
The ex-vessel FP releases result from the core / concrete interaction where gases generated from the decomposition of concrete sparge through the molten
- core debris. The large volumes of gases which pass through the melt and the increased surface area associated with these gases accelerate the vaporization of melt constituents, which subsequently condense into aerosols af ter leaving the mel t . Another mode of aerosol generation is also modeled. This is the formation of mechanical ' aerosols which are a . result of the gas bubbles break-ing through the upper melt surf ace. Hence, all -FP release from the core / con-
-crete interaction is modeled as being in aerosol form. The ex-vessel release is dominated by the Ba, Sr, Ru, La, and Ce groups. In general , a small f rac-tion of the core inventory of iodine is predicted to be retained in the core debris at the time of bottom head failure and is passed to VANESA, a computer code in the STCP which estimates ex-vessel releases, for release during the ex-vessel phase. VANESA assumes this iodine release to be in the form of Csl aerosol. The duration of the ex-vessel release starts shortly af ter bottom head failure and is typically calculated ten hours beyond initiation, although the majority (-90%) of ex-vessel release generally occurs within three hours of the initiation of the core / concrete interaction.
In summary, results of severe accident simulation with the state-of-the-art methodology incorporated into the STCP indicate two phases for fission '
product release. The in-vessel phase is associated with core degradation and releases are dominated by noble gases, cesium, iodine, and tellurium. Iodine is assumed to be in the chemical form Csl. With the exception of the noble gases, all releases from the RCS are in aerosol form. The ex-vessel release phase resul ts from the interaction of the molten core and the concrete
basemat. The ex-vessel release is dominated by the Ba, Sr, Ru, La, and Ce ,
groups. Small amounts of volatiles are also released ex-vessel, notably 1 I
iodine - in the form of Csl. All releases are in the form of aerosols. When appropriate intermediate codes, SPARC AND ICFDF, estimate FP aerosol retention in ESFs. The removal of airborne aerosol 5, ' generated either in-vessel or ex-vessel, by natural deposition processes is estimated in NAVA.
The STCP, as currently implemented, does not model any gaseous iodine >
release, nor is there any explicit modeling of gaseous iodine behavior, or the q effect of any chemical additive to the CSS. The physical washout of aerosol by sprays is modeled and results in substantial removal of aerosols from the containment atmosphere. Figure 1 shows a typical comparison of the accumula-ted masses of material leaked to the environment for a sequence, Zion S2 0-c, where the CSS operates and another sequence, Zion TMLB'-c, where the CSS is assumed to fail.g A similar comparison for the Surry plant is shown in Figure 2.8 The reduction of Csl aerosol leaked to the environment for these reactor-sequence combinations is approximately 50 to 105 , respectively.
Hence, given the current best estimate of the fission product, release charac-teristics and the processes that can act on the FP releases, the physical action of the CSS and natural aerosol removal processes which proceed with or without the CSS can substantially reduce airborne concentration of FP's. This includes iodine as it is modeled to appear in aerosol form. It is noteworthy to mention at this point that tne CSS chemical additive (s) effect only gaseous forms of iodine,1,2 Hl. and, depending upon the specific additive, organic
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iodine, and do not contribute to the physical removal of aerosols. Aerosol removal by CSS washout is modeled as a purely physical process. The most com-mon adgige (namely, NaOH), however, may play a secondary but important role in 6. y the sump pH and mitigating radiolysis assisted evolution of iodine in gaseous form.
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- 3. CSS EFFECTIVENESS AS A FP REMOVAL SYSTEM As mentioned heretofore, adoption of the TID-14844 source term assump-tions to assess the consequences of DBA resulted in the conclusion that molec-ular iodine dominated off-site dose. This, in turn, fostered consideration of the CSS as a fission product removal system and resulted in the addition of additives, namely, sodium hydroxide for 12 and HI removal and sodium thio-sulfate for the further removal of organic iodine, to increase the effective-ness of the spray solution to absorb and retain iodine.
A primary data base upon which much of the thinking regarding the effec-tiveness of spray as a fission product removal system was the large scale' con-tainment system experiments (CSE).10 The CSE were carried out in a one-fifth linear scale containment having an internal volume of 751 m . Experiments 3 A-3, A-4, A-6, A-7, and A-8 were performed to determine the effectiveness of CSS to remove airborne FP. The major variables considered included contain-ment temperature and pressure, spray solution composition, and initial or Details of the experiment may be found in the original recirculatgy phase.or the concise summary provided by Albert,ll which is reproduced references here as Appendix B. The results are displayed in the appendix in Figures 46 through 50 (original text numbering) as plots of airborne iodine to the con-centration versus time. The absorption iodine was generally interpreted as being governed by a first order process:
h = -AC, x where C is .the airborne concentration of iodine, t is the time, and A is the first order removal constant. The results are tabulated in Table 1. Only the first spray period results are given since other processes, such as desorption from wall or the effect of inhomogeneous mixing, complicate the interpretation of subsequent spray periods.
Several observations can be noted. The DF's, ratio of iodine concentra-tion prior to spray initiation divided by the concentration immediately after spray has been stopped, range from 5 to 100. The differences in run A-3 and run A-4, may in part, reflect the change in spray flow rate. The differences in A-4 and A-6 could result f rom either the increased buffering capacity of the spray solution or the change in initial containment temperature, 25 versus 124*C, respectively. However, a comparison of runs A-5 and A-6 with run A-7, where the solution is unbuffered H 3803 , suggest the latter. In addition, it is interesting to note that runs A-6 and A-7 gave comparable DF's, indicating that in the initial injection phase buffering, pH control, had little observ-able effect. A superficial comparison of the results given in Table 1 for runs A-7 and A-8 indicate comparable performance on the basis of 0F, while showing significant difference in A or t1/2 This results from two changes in the experimental procedure: spray nozzles that delivered a smaller mean i drop size and a shorter duration of initial spray operation. Given these !
changes to the experiment?1 protocol, the results of run A-8 would appear con-sistent with the former runs.
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-. ; a l-Table 1 Summary of CSE. First' Spray Results a d
.Run Solution Composition D t C
(min) A(min-1)' DF 1/2 A3 525 ppmr3'i B03 , pH 9.5 5.5 0.13 ~5 1
A4 525 ppm H3 B03 , pH 9.5 1.4 0.50 100 A6 3000 ppm H3 B03 , pH 9.5 2.1 0.33 30 A7 3000 ppm H3 B03 , pH 5 2.2 0.32 30 A8 3000 ppm H3 B03 , pH 9.5 0.64 1.1 30
-a Adapted from Reference 10.'
. Fresh room temperature solution. , .
- cCorrected for other removal mechanisms, e.g. , reaction wall; corrections.
were <10%; t1 d Ratio of airo/2orne = in 2/concentration iodine A. direct before and after spray opera-tion.
i 3
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Two additional experimental sources of information on the effectiveness of spray additives12were located.13 These experiments were performed in the PISCO 10 facility and by JAERI.
.The PISCO 10 model containment had an interval volume of 95 m3 . Twelve experimental runs were carried out. Service water and 1% sodium thiosulf ate (Na2S02 3) solutions were tested. Service water can certainly be considered additive free. The authors of Reference 12 concluded that the removal rates were similar for both service water and 1% thiosulfate solution. A summary of these results is given in Table 2.
Nishio et al .13 quotc) results obtained at the Japan Atomic Energy Research Institute (JAERI). However, no citation was given and the original manuscript could not be located. Based upon the description given by Nishio, the experiments were carried out in a 708 m3 cylindrical vessel . Two experi-ments, BIS-1 and BIS-2, were done under conditions .that simulated a BWR LOCA.
One experiment (PIS-9) was performed for conditions which simulated a PWR LOCA. Summary results are given in Table 3. The range of values observed in the JAERI tests is in fair agreement with previous studies. However, direct comparison in all cases is not possible since the spray flow rates are atypi-cal of the regime anticipated in domestic PWRs. However, these results ar.5 applicable to BWR containments.
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Table 2 Summary of PISCO First Spray Results a
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Solution Composition b t A (SI"~ l)
Run 1/2 ("I")
101 1% Na 2S0, 2 3 62 C 1.3 0.53 106 1% Na 2 3, 30 C 1.0 0.69 107 1% Na 23, 18 C 0.3 2.3 108 1% Na 2 3, 14 C 1.5 0.46 103 service water, 86'C 3.0 0.23 102 service water, 80 C 0.3 2.3 104 service water,16*C 2.0 0.35 109 service water, 26 C 3.0 0.23 110 service water, 34 C 2.0 0.35 111 service water, 35'C 3.5 0.20 112 service water, 33 C 1.2 0.58 a
Adapted from Reference 12. DF's not calculated, since spray duration ' varied widely, bS olution composition, temperature of spray.
~
Table 3 Summary Results of JAERI Tests a Run Solution Composition b t A (*I"~!)
1/2 (*i")
BIS-1 pure water, 70*C 2.9 0.24 BIS-2 pure water, 70*C 6.5 0.11 PIS-9 1.4% H3 B03 , pH 9.6, 40 C 0.50 1.4 a
Adapted from Reference 13. DF not calculated; insufficient data.
Solution composition, temperature of supplied spray.
r, 3 4 -SPRAY MODELS
!' 4.1 Analytical Procedure The original treatment of the' removal of iodine from the containment atmosphere is presented'in Reference 10. Th summary description given here is based upon the discussion given by Albert.{l'
-The removal of iodine 'from -the containment atmosphere is traditionally modeled as a first order process:
h='-AC, (1) where C is the airborne iodine concentration, t is the time, and A is the -
removal rate constant. . Integration of Equation (1) yields C = Coe "# (2) with Co is ' the initial concentration of iodine. The removal coefficient has been defined 10, l" as A = FPc/V, (3) where F is the volumetric flow rate, P is -the partition coefficient of iodine between the spray liquid and the gas phase, V is the sprayed containment vol-ume, and cis the removal ef ficiency. The removal efficiency has been theo-retically defined for several mass transport limiting processes. These
< expressions are for the stagnant- drop model 2
2 c = 1 - I (6 N he A 4)/a [a n +N sh5 "sh"I) ()
for the stagnant film model c=1-exp[(-6kt)/d(P+k/k[)],
ge g (5) for the well mixed drop model e = 1 - exp [(-6 kg t,)/d P], (6)
.l
'.- 4 and for the gas' phase controlling resistance model
- ._ t c=6k h/P g
v g d. (7)
In these equations, k
g
= gas film mass transfer coefficient, k{ = liquid film mass transfer coefficient (no reaction),
t, = drop exposure time, d = drop diameter, Nsh = kg d + (2 P D3 )
Dy = liquid phase diffusion coefficient, 2
e =4D t g e/d ,
a n = nth root of the equation an cot (an) + Nsh - 1 = 0
.; . h = drop fall height, and v = terminal drop velocity.
g In the initial spray phase, when the solution is fresh and therefore con-tains no dissolved iodine, it might be expected that the mass transfer to the drop is limited by gas phase transfer. Combining Equations 3 and 7 one obtains 6k Fh 9
A= yv d
- f(P). (8) 9 i Note that if gas-phase transfer is the rate limiting step, then the first order removal coefficient is predicted to be independent of sol ut, ion composition. Similar first spray removal rate coefficients for various solu-tions have been observed (see previous section), although the equilibrium par-tition coefficient certainly does vary with the composition of the solution.15 Another variable, which will find use in the next section, is the total drop surf ace area, A, created per unit time per unit sprayed containment volume.
I L__--__ _ _ _
)
1 l
l A= =
d
=h(h3)(wd),g 2
[g)
A is simply the total surface area (ST = nS ) created by drops of mean d
diameter, d, at the flow rate, F, and divided by V, the sprayed containment vol ume . Substituting Equation 9 into 8 yields:
A=k gh A/v g. (10) 4.2 Reevaluation of Existing Data In an earlier section, available data on the iodine removal effectiveness was reviewed. Care was taken to select and display only data for fresh spray sol utions . In both the CSE and PISCO experiments, multiple spray periods, including recirculation, were investigated. These latter results are expected to reflect the effects of increased iodine concentration in the drop, as well as the heretofore mentioned complications of wall desorption and inhomogeneous mi xi ng . However, when the spray solution was fresh, all solutions appeared to ,
effectively reduce the airborne iodine concentration, regardless of the pres-ence or absence of an active spray additive. To demonstrate this contention, and account for the major variables causing variation, selected first spray data from the CSE, PISCO, and JAERI tests are displayed in Figure 3. In this figure, the first order removal rate coefficient is plotted against the nor-malized total new drop surface, A. Also displayed are the range of flow regimes of several typical PWR's. These were estimated from information obtained from the Surry FSAR" and information provided in References 17 and
- 18. The upper limit of a range represents both spray header systems are oper-ating, while the lower limit represents operation of only one of the two redundant spray systems. Approximately 3/4 of the PISCO data and both JAERI BWR test data are not plotted, as they would lie well beyond the anticipated range of A for domestic PWRs. ,
Although the plotted data exhibit some scatter, a generally good correla-tion is found. Hence, when spray solution is fresh, the removal of iodine from the containment atmosphere is dominated by gas phase mass transport and is effectively independent of the equilibrium iodine partition coefficient of the solution, and primarily controlled by the amount of available surface to which iodine may be transported. At a first level of approximation, the good correlation of A and A observed indicates that the combination of terms not explicitly examined in Equation 10 is effectively constant or slowly varying over the range of experimental conditions investigated. It should also be noted that 3/4 of the PISCO and JAERI data not plotted, that data which was taken in a flow regime atypical of domestic PWR's, does not correlate well j with A alone. There are several potential reasons why this occurs, howcVer, j these have not been examined since it is felt that the experimental conditions are basically atypical of those conditions associated with domestic commercial f PWR's.
l i
b_ _ _ _ _ _ _ _ _ _ _ _
Values of k g, computed from Equation (10) and for the experimental data di spl ayed in Figure 3, are given in Table 4. For comparison, estimates of kg and A, based upon a well known correlation for heat transfer to a single drop, are al so given. Aguming la the mi nimum observed experimental k, 3 m/ min, maximum fall height e and that both spray headers are operating, first order removal coef ficients of 0.8 min-1 and 2.0 min-1 are estimated from Equation (10) for the Surry and Zion plants, respectively. If it is assumed that structures, e.g., the reactor pressure vessel and steam gener-ators reduce the effective drop fall height by 50% to 60% of the maximum, then estimated A's of 0.4 min-1 and 1. 3 mi n-1 are obtained for these plants, respectively.
L -
.p. ..
100 A
50 e
e a , i
~
t a
f a x - 10 -
e 5
Surry Zion o CSE
~
m PISCO !
A JAERI j 1 l l l l l 0 1 2 3 4 5 6 A (m-min)~1 Figure 3 Removal constant versus normalized, new drop surface area; fresh spray data.
' - - ~ ' " - ' - - - - - _ _ - . _ _ _ _ _ , _
d ,o BLANK PAGE l
O
- j l
l l
\
i mm .
1 . .
- 5. DISCUSSION AND CONCLUSION In previous sections of this report, the current best estimate descrip-tion of source term characteristics was summarized and available data on the effectiveness of spray as a fission product removal system were presented, reviewed, and reevaluated. CSS can effectively reduce airborne concentrations of aerosols which current methods of source term estimation predict to over-i whelmingly dominate fission product releases . The inert noble gas releases l are unaffected by sprays. Aerosol removal by the sprays is a physical process and this process is not al tered or aided by the presence of chemical additives. Other natural processes, modeled by NAVA-4, can also reduce air-borne aerosol concentration. The relative benefit accrued is closely related with the time available prior to containment failure for these natural proc-l esses to act. Data presented in Chapter 2 indicated that the combined effect of these processes can reduce airborne Csl aerosol concentrations by a factor 50 to 10 , depending upon the specific reactor and accident sequence being examined.
Current NRC sponsored analytical modeling of severe accidents, i.e., the STCP, does not predict the emission of gaseous iodine in the anticipated acci-dent environment associated with commercial LWR's. This is based upon an examination of the TM1-2 accident, and subsequent thermochemical analyses.
The actual chemical form of iodine is still subject to 7a de on uncertainty. Evolving experimental and analytical evidence ,19,2 gree indi-cates boron may be chemically associated with Cs; hence, boron may be in com-petition with iodine and potentially liberate iodine in another form, possibly gaseous, prelimi nary experimental resul ts21,22 al so suggest reaction of Cs0H and Csl with the stainless steel surf aces of the RCS, with the reported emission of gaseous iodine in some cases. The reproducibility of these exper-imentg3 are currently being investigated. In addition, some experimental evi-dence has been obtained that indicates the conversion of Csl aerosol to gaseous iodine during hydrogen burns. These observations certainly reinforce the diversity of material interactions and phenomena that can occur and give rise to uncertainty. Additional research is in progress and is required to resolve this uncertainty. However, regardless of the extent of gaseous iodine conversion, the washout by an operational CSS would occur and the data pre-sented in Chapters 3 and 4 clearly suggest that it is effective. Moreover, the fresh spray data suggest efficient iodine removal regardless of the pres-ence of additives during the initial injection phase. This is not to say that Na0H is not ul timately required to increase the absorption capacity of the spray solution and mitigate iodine reevolution from the reactor sump. On the contrary, suf ficient evidence exists to warrant pH control in the long term.
The regulatory option to be reconsidered is whether or not the presence of NaOH is required during the initial injection phase of CSS operation. Two items affect this decision. One, is the effectiveness of fresh spray solution, and the other is that since the CSS is activated on high containment pressure, it is quite possible that the CSS will have switched from the injec- -
tion to the recirculation phase prior to the release of any fission prod'uct activity.
A potential alternative is to cdd pH control directly to the reactor sump rather than in the initial injection supply of the CSS. Additionally, it would be attractive to initiate pH control on some feedback directly related to the release of activity rather than on high containment pressure. This I
- ________________ _ _ . . . 1
- e. 0 would have the obviou.s advantage of not introducing the additive (s) until required. A secondary benefit should the reactor incident be terminated with-out the release 'of FP activity, would be a simplified cleanup recovery.
O
L, s.
L
' Table 4 Comparison of Experimental and Estimated Mass Transfer Constants m
k Run A(m-min) 1 t e("i") A(*i "~ l) 'A R
gmin k g est d
A3 0.40 a
0.050 D
0.13 0.14 c 6.5 6.7 8 A4 1.55 0.050 0.50 0.52 6.5 6.7 A6 1.55 0.050 0.33 0.65 4.3 8.4 A7 1.55 0.050 0.32- 0.65 4.2 8.4 A8 2.45 0.083 1.1 1.8 5.4 8.9 PIS-9 5.36 0.092 1.4 3.7 2.9 7.4 109 0.74 0.029 0.23 0.15 11 6.7 110 1.35 0.020 0.35 0.18 13 6.9 111 1.19 0.020 0.20 0.16 8.6 6.9 112 0.79 0.029 0.58 0.16 25 6.9 (a) Calculated from reported data for F, V and d.
(b)te = h/vg. Velocity calculated from vg = (4(Pa - Pg) g d/3 pg ()1/2, where E = 18.5/Re ,6, and o
pa is the drop density, pg is the gas density,.g is the gravitation constant, ( is the drag coef ficient and Re is the Reynolds number; Handbook of Multiphase Systems, G. Hetsroni, Hemisphere Pub. Corp.,
New York, NY,1982.
(c)Aest = A te kg est.
(d)kgback calculated from experimental data.
(e)kg est estimated from the correlation of Ranz and Marshall, Chem.
Eng. Prog., 48, 1952.
kg = D/d (2+0.6(pdvg/p)1/2(p/p0)1/3),
where D is the.diffusitivity of 1 .2 All gas phase variables are for air.
- , - - - - -- - - - - - - ------n--,-------, ---,-- - - - - - - - - - - - - - - - -
i *
- p .. .
l BLANK PAGE l
1 1
i i
, e.
l O
. 4 1
1
- 6. REFERENCES
- 1. U. S. NRC, " Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants," NUREG-0800, July 1981.
2.- U. S. NRC Regulatory Guide 1.4, " Assumptions Used for Evaluating the Po-tential Radiological Consequences of a Loss of Coolant Accident for Pres-surized Water Reactors," Rev. 2, June 1984
- 3. V. S. NRC,10CFR100, " Reactor Site Criteria," 27FR3509, April 12,1962.
- 4. J. J. DiNinno et al ., " Calculation of Distance Factors for Power and Test Reactor Sites," U. S. Atomic Energy Commission, TID-14844, March 1962.
- 5. U. S. NRC, " Technical Bases for Estimating Fission Product Behavior Dur-ing LWR Accidents," NUREG-0772, June 1981.
- 6. M. Silberberg et al . , " Reassessment of Technical Bases for Estimating Source Terms," NUREG-0956, 1986.
- 7. R. Wilson et al ., " Report to the American Physical Society of the Study Group of Radionuclides Release from Severe Accidents at Nuclear Power Plants," Rev. Mod. Phys., 57(3), Part II, July 1985.
- 8. J. A. Gieseke et al ., " Radionuclides Release Under Specific LWR Accident Conditions," BMI-2104, July 1983.
- 9. H. P. Nourbakhsh et al ., " Effectiveness of BWR Pressure Suppression Pools in Retaining Fission Products," Brookhaven National Laboratory, Technical Report A-3788, July 1,1986.
- 10. R. K. Hilliard et al ., " Removal of lodine and Particles from Containment Atmosphere by Sprays: Containment Systems Experiment Interim Report,"
BNWL-1244, February 1970.
- 11. M. F. Al be rt , "The Absorption of Gaseous Iodine by Water Dropl et s ,"
NOREG/CR-4081, July 1985.
- 12. S. Barsali et al ., " Removal of Iodine by Sprays in the PISCO 10 Model Containment Vessel," Nuc. Tech., 23, August 1974
- 13. G. Nishio et al . , " Containment Spray Model for Predicting Radiciodine l Removal in Light Water Reactors," Nuc. Tech., 54, July 1981.
- 14. A. K. Postma et al ., " Technological Bases for Models of Spray Washout of Airborne Contaminants in Containment Ves sel s ," NUREG/CR-0009, October 1978. ,
- 15. Reference 14 and citations contained therein.
- 16. .VEPC0, Surry Power Station Units 1 and 2, Final Safety Analysis Report, Virginia Electric and Power Company.
l I
r- .
d 4 l
I
- 17. " Westinghouse Nuclear Training--Four. Loop Plant Information Book," West-
' inghouse Electric Corp., Pittsburgh, PA,1978.
- 18. U.S. NRC, ." Preliminary Assessment lof Core Melt Accidents at the Zion and Indian Point Nuclear Power Plants and Strategies for Mitigating Their Ef-fects," NUREG-0850, Nov. 1981.
- 19. D. Powers, "High Temperature Fission Product Chemistry," Severe Fuel Dam-age and Source Term Research--Program Review Meeting, Oak Ridge, TN, April 1986.
- 20. A. T. D. Butland et al ., " The Effect of Variations in Chemical Species and Associated Properties on Primary System Retention in PWR Severe Acci-dent," to be published.
- 21. R. M. Elrick et al ., " Reaction Between Some Cesium-lodine Compounds and the Reactor Materials . 304 Stainless Steel, Inconel 600 and Silver,"
NUREG/CR-3197 (3 volumes), June 1984.
- 22. D. Powers and R. Elrick, "SNL Radiation Effects Experiments," Severe Fuel Damage and Source Term Research--Program Review Meeting, Oak Ridge, TN, April 1986.
. 23. L. S. Nelson et al . , "The Behavior of Reactor Core-Simulant Aerosol s During Hydrogen / Air Combustion," Thirteenth Water Reactor Safety Research i Information Meeting, Gaithersburg, MD, Oct. 1985.
S l
e,: :.'
A-1 i'
APPENDIX A.
Computerized searches of the literature were performed to obtain perti-
'nent citations on the subject containment spray and spray additives for PWRs.
The following' databases were queried:
EDB'(Energy Data Base, D0E/ RECON, 1976-present)
The search resulted in 171 citations; of which 18 were selected and ac-quired in support of the research project; and NSA- (Nuclear. Science Abstracts, DOE / RECON, 1967-1976)
The search resulted in 8 citations. l The search strategy was:
PWR i
and
[ containment spray systems .
or 1
(containment system) and (atmospheres) 1
'or 1
- ((sprays or droplets or particles or iodine removal or i particulate or' additive (s)) and (containment systems))].
I i
i i
1 i
1
l~, .
B-1 APPENDIX B The following chapter was reproduced from NUREG/CR-4081. It provides a brief description of the CSE and a concise summary of the CSE results and their precision.
4
1 l
85 l l f
- 7. EXPERIMENTAL DATA j
I i
The experimental data used to compare with the results of the spray ;L model are f rom the Containment System Experiments (CSE).3 Expe rime nt al L runs A-3, A-4, A-6, A-7, and A-8 of this series are large scale spray system tests to de t e rmine the effectiveness of a spray system for removing airborne fission products. The results of these tests are -
reported in terms of the gas phase elemental iodine concentration versus '
time and also in terms of the liquid phase elemental iodine concentra- ,
tion versus time. The parameters for the spray experiments are the spray flux, the drop size, the gas phase temperature, pressure, and humidity, and the liquid spray composition. The physical dimensions of j the CSE vessel are listed in Table 3 and are shown in Figure 44. Since ,,
}
lil Y
Table 3. Physical conditions common to all spray experiments (Hillard 3)
I it Volume above deck including drywell 21,005 f t3 'b 595 m3 Surface area above deck including 6,140 ft2 569 m2 drywell i
Surface area / volume 0.293 ft-1 0.958 u-'l {
Cros:3 section area, main vessel 490 ft2 45.5 m2 i Volume, middle room 2,089 f t3 59 m3 Surface area, middle room 1,363 ft2 127 m2 Volume, lower room 3,384 ft3 96 m3 '
' Surf ace area, lower room 2,057 ft2 191 m2 I Total volume of all rooms 26,477 f t3 751 m3 Total surface area, all rooms 9,560 ft2 888 m2 Drop fall height to deck 33.8 ft 10.3 m i Drop fall height to drywell bottom 50.5 ft 15.4 m 'l Surface coating All interior surf aces .
coated with phenolic paint."
Thermal insulation All exterior surf ace s : [
covered with 1-in. '
fiberglass insulation.b ' '
aTwo coats Phenoline 302 over one coat Phenoline 300 primer. The Carboline Co., St. Louis, Mi s s o u ri .
b k = 0.027 Btu /(hr) (ft2) (oT/ft) at 200* F, Type PF-615, Owens-Corning Fiberglass Corp.
i- g. .-
w l
86 onw owc so Etv ETD RUN RUN A3 A4,G.7,8 m
J R = 6y [h S
- 6 f t PLAN VIEW cf NOZZLE ARRANGtWENT j $ PRAY NOZZLES
- f'*y%,
- y MAYPACK CLUSTER (14) .
o* a cf DRYWELL N y j MAIN CONTAINMENT l VESSEL Ll0 SOLUTION - A \ o a o N DROP COLLECTOR (4)
STOtl AGE TANK g h VIEWING WINDOW Y Y YI2>-- -TsiEr SAMPLER DECK
- I "l
, WALL TROUGH c FISSION PRODUCT WET WE LL AEROSOL (CLOSED OFFL j( l
' ~
.. DR YWE L L -
io Q[J -MIDDLE ROOM
'b -kJ -
LIQUID SAMPLEq D j
PUMPS LOWER ROOM R ECIRCUL ATION PUMP
,, Fig. 44. Schematic diagram of containment arrangement used in CSE spray tests (H111ard 3).
thes'e tests were made in realistic and not idealized equipment and con-ditions, the liquid and gas flow patterns are complex and not well characterized. The results from the new spray model will be compared with these results, but no better than approximate agreement can be ex-pected. This data, howeve r, can still provide a means for useful and meaningful evaluation of the spray model.
The CSE vessel is a large scale vessel (see Table 3 and Figure 44). The overall dimensions of the vessel are 20.34 meters high and a diameter of 7.62 meters. The vessel has a drop fall height of 15.4 i meters.
The overall volume of the vessel is 751 cubic meters.
The tests varied the temperature, pressure, pH . of the drop, spray nozzle configuration and drop size. The conditions for run A-3 are a temperature of 298K, I atmosphere of pressure, pH of 9.5 and a drop dia .
meter of 1210 microns. For all of the tests, the spray solution tem- '
perature was at 25'C, and the solutions were all buffered. For run A-4, the conditions were the same as for A-3 except for a higher spray flow rate and a different spray noz zle configuration. Run A-6 increased the temperature of the gas to 397K and the pressure to 3 atmospheres. Run A-7 changed the pH to 5, lowered the temperature to 394K and raised the l
.o
} . _ _ . . .
87 l
pressure to 3.4 atmospheres. { i l
microns. Run A-8 changed the drop diameter to 770 !
) See Figure 44 for spray nozzle arrangements, Table 4 for spray nozzles used, Table 5 for the atmospheric conditions, Table 6 for the , i spray timing of therates flow sprayand solutions used in the tests and Table 7 for the periods. f[.
The experimental procedure for the molecular iodine spray absorp-tion tests involved first heating the containment vessel with steam j until the specified temperature was reached. A flask containing. b) molecular iodine T'
'cally. traced with I curie of iodine-131 was heated electri-Air was passed der the , flask to release molecular iodine.
Samples were taken prior to turning on the sprays to determine how molecular iodine behaves without sprays. After the first spray period i
't Table 4. Nozzles used in CSE spray experiments (li111ard3 )
u Runs A3, 4, 6, 7 i Nozzle type: !
Spraying Systems Co. 3/4 - 7G3 Nozzle characteristics: ~ Toy type, full cone 1l i
A3 A4 6, 7 Number 3 12
Layout U
'M g Triangular Square gride
'y ..- Spacing 10 ft 5 in. 6 ft apart F 5
apart i I
i Pressure 40 psid 40 psid k Rated flow s4 .g g 4 4 gpm 4 gpm MMD ,
1210 p 1210 y [
a 1.5 8 1.5 ~
Run A8 J!
.}
Nozzle type: Spray Systems Co. 3/8 A 20 Nozzle characteristics: Fine atomization, hollow cone .
j Number used 12 Layout Square grid g Spacing 6 ft apart
, n Pressure 40 psid .
,EY
' t [..
Rated flow 4 gpm '
MMD 770 p W 4
o 1.5 li g
lt q;
P 4
5
- e ,
l T
'I 88 Table 5. Atomspheric conditions in CSE spray experiments (Hillard 3)
Run Run Run Run Run A3 A4 A6 A7 A8 Containment vessel No No Yes Yes Ye s insulated ,
Forced air circula- Yes Yes No No No tion" ~
Start of 1st spray Vapgrtemperature, 77 77 255 248.7 250
- F Pressure, psia 14.6 14.6 44.2 50.0 50.7 Relative humidity, % 70 88 100 100 100 End of lst. spray.._._. _ ____.........._ _... .... . _ _.
por temperature, 77 77 229 234.5 243
'Va. p o --... ..-
Pressure, psia 14.6 14.6 38.6 44.4 48.2 Start of 2nd spray Vapor temperature, 77 77 237 240 __243
.p o Pressure, psia 14.6 14.6 40.8 46.0 243 End of 2nd spray '
~ Vapor temperature, 77 77 202 203 188 opo Pressure, psia 14.6 14.6 29.5 36 34.1 Start of 3rd spray Vapgrtemperature, 77 77 233 230 218
'F Pressure, psia 14.6 14.6 40.7 41.8 32.2 Start of 4th spray Vapgrtemperature, c e c 232 247
- F ,
Pressure, psia e o a 42.4 52.4 End of 4th spray Vapgrtemperature, e o e 192 175
- F Pressure, psia e c e 32.7 32.4
- Fan without duct located in bottom of drywell. .- '
2400 f t 3/ min diccharge. .
b Average of 5 thermocouple located at various eleva-tions and radii.
C j No fourth spray. '
l Il
_ _ _ _ _ . _ . __ _ _ _ _ _ I
_q
~
4 89-i L. I p
. Table 6. Spray flow rates and solutions l
used in CSE experiments (Hillard3 )
Run Run Run : :
Run Run A4 j
.A3 A6 A7 A8
1st spray Total flow rate, gpm 12.8 49 49 l
Volume sprayed, gal 49 50 128 .
490 490 490 150 Spraying pressure, psid 40
- 40 40 40 40 l '
Solution a a !g b c b '
2nd spray -q{
s..
Total flow rate, gpm 12.8 49 l
Volume sprayed, gal 385 50 48.5 50 U,l; h 1480 1500 1455 1850 Spraying pressure, 40 40 40 psid 40 40 Solution a a b
[C
.) -
c h i: ,
3rd spray ,
Total flow rate, gpm 12.5 42 t Volume sprayed, gal 16 45.5 47 '
II 735 1890 960 2730 Spraying pressure, 2820 40 29 4 36.5 Solution d e 36.5 ,
e e e 9!
4th spray , :.,
v, . i Total flow rate, gpm g g g U3-Volume sprayed, gal 48.6 50.4 g g g 2428 f;
Spraying pressure, 2520 9(ll g g g 40
- i psid 40
!.Y Solution g g g l f f
" Fresh, room temperature. 525 ppm boron as H3B03 in H; demineralized water. NaOH added to pH of 9.5. :l!%
b Fresh, room temperature. 3000 ppm boron as H3B03 in j,N;je U
demineralized water. NaOH added to pH of 9.5. j,g.J Fresh, room tec:perature. 3000 ppm boron as H3B03 in pa demineralized water. No NaOH added. pH 5. I d '
$,[+j Fresh, room temperature demineralized water. &
- S olution in main vessel sump recirculated No heat ex-
' igg changer used. .
.l{
i
[Frdsh, room temperature. P.ht !
I wt7. Na2 S203, 3000 ppm boron as H3B03 in demineralized water. NaOH added to pH 9.4. ,. }
9 No fourth spray. j y'
4 !
I
.h 4
'i.
O,
o o ff 9
. Table 7. Timing of spray periods (Hillard3 )
Time after start of iodine release, min Run Run Run Run Run A3 A4 A6 A7 A8 First spray Start 40 40.5 30 30 30 Stop 50 50.5 40 40 33 Duration 10 10 10 10 3 i
Second spray Start &
140 140 80 80 80 Stop 170 170 110 110 117 Duration 30 30 30 30 37 Third spray Start 1473 1205 1565 1323 200 Stop 1533 1250 1525 1383 260 Duration 60 45 60 60 60 Fourth spray Start a a a 1443 1350 Stop a a a 1493 1400 Duration a a a 50 50 C
No fourth spray. ' '
of each run was started, many samples were taken from the gas phase, fromcollectors.
drop the liquid in the sump, from the wall trough and from the spray When the first spray period was ended, more samples were taken sometimes a to determine how molecular iodine acts. A second, third, and the gas and liquid phases.period fourth spray were used with many samples taken from The gas phase concentrations were determined by Maypack samplers (see Figure 45), and the liquid phase concentrations were de te rmined by measuring the amount of iodine-131 tracer present.
For more information see Reference 3. '
55 andResults Table 8. of these experimental tests are shown in Figures 46 through. -
the experimental Table runs. 8 shows the material balance of iodine for all of It should be noted in this table that between 25.65% andfor57.58%
unaccounted and is assumed of the to iodine be deposited delivered on surf to the aces.containment vessel is through 50 show the Figures 46 as a function of time. concentration of elemental iodine in the gas phase The data is reported in terms of the half life i
m
- m. 0 0 4 2 0 6
2 3
4 3
8 6 ;
i 0 9 2 1 0 2 8 8
w 1 0 3 1 0 5 4 N d. 0
- 5. iI 5
- d. 1 5 1 8 8
0 9 0 5 0 0 1 8 1 w 1 5 4 A 1 n
w.
u 0 5 2 2 9 1 R s 0 4 6 3 3 1 5 8 1 4 7 4 m 6 s 6 1 8
w a 3 m .
1 4 5 0 r
1 1 0 5 5 a 5 3 m C 1 0 ' -
9 r 9 5 0 0 1 5 0 5 4 g
ll a G
- i *f -
0 5 3 2 r .
1 0 0 0 0
0 t
2 3
0 0 0 4
3 6
6 h
Z 0
0 0
6 2
0 0
6 0 0 7
1 9 2 8 3
1 4
2 7 5
e 7 1 9 0 4 5 4
A 1 n
r., R u 0 6 5 2 3 7 s 0 0 0 3 4 7 8 9 6 6 93 8
- m 5 s 5 2 5 1 3 1 a 1 t 2 0 3 7 m
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1 INLET 6 SIX SILVER PLATED SCREENS 11 SCREEN 2 TEFLON BALL 7 SILVER MEMBRANE FILTER 12 SPRING 3 NOSE CONE 8 CHARCOAL LOADED FILTER 13 BODY 4 TEFTON GASKET 9 STOPRING 14 END CAP 5 TWO PARTICLE FILTERS 10 CHARCOAL BED 15 OUTLET Fig. 45. Maypack Sampler.
of iodine, defined as
^
t 1 /2 = - Ln (1/2)/A ,
(65)
= 0.693/A ,
(66) where A is the removal rate constant.
The reason the data are in this form is because the old spray models ( Equa tions 1 through 7 of Chapter I, Section 2) are in terms of the removal rate constant. Figures 51 to 55 shows the concentration of iodine in the liquid versus time. As can be seen in these figures, there is a delay in the response of the increase in the concentration of iodine in the liquid phase.
In these tests there are many processes for the removal of molecu-lar iodine from the gas phase.
In these large scale realistic tests, there are painted wet walls, and d ry walls. surfaces, non painted surfaces, insulation, sprays, All of these features can contribute to iodine sorption, and heat transfer can also have an offeet on the i
moval rate of molecular iodine from the gas phase. Therefore, one can re f .
only hope to develop an approximate model which accounts for the major phenomena involved and considers only the removal by the sprays. If one looks at the drop data, these data are " difficult to interpret, not only because of sampling inadequacies but because the relative fractions of the various iodine forms and particle sizes were changing rapidly with time."3
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'The data for the gas phase are the result of the combined effects of all of the phase. But processes for the removal of molecular iodine from the gas I
small overallif all of the processes except for the sprays exerted only a effect in the removal of molecular iodine from the gas phase, then these data would be acce'pt5b1E ' f rom the standpuint of use-fulness in determining the efficiency of the spray model. i liquid in the sumps should eliminate The data for cause some of the sources of error be-liquid.these data shows how much molecular iodine is transferred to the Nevertheless, any iodine that is on the surf aces and is not chemically . held to the walls could be washed of f in the sumps. Since the sprays were not started at the instant the molecular iodine was released, a significant amount of molecular iodine released into the containment may have deposited on the.. surf aces, and subsequently been washed off into the 'sitmps'6r~Eight"have been transferred back into the gas phase later when the partial pressure of molecular iodine in the gas phase was smaller than the partial pressure of molecular iodine on the surfaces.
removal rateThe latter effect of molecular could result in an underestimate of the iodine. ~ '
To remove experimental some of the possible sources of error, the comparison of results to the results of the spray model will be limited to the' area of the drywell. A The drywell had a cross sectional area of 8.8 square meters (which is a diameter of 3.35 meters), a drop fall height of 15.4 meters, and a volume of 135.52 cubic meters. For example, in rud 'A-3, 'at The s ta rt of the first spray period, the initial gas phase concentration was approximately 5 x 10" micrograms / cubic, meter (1.97 x 10-7 moles / liter) 125 x 10 micrograms / cubic meter (4.92 xand the final concentration was approximately of iodine removed from the gas phase during 10-8 mole s/li te r) . The amount the first grams. spray was 5.082 Also, at the start of the first spray, the concentration of the liquid in the drywell sump was approximately 8x 102 micrograms / liter
- and the initial volume was approximately 150 liters. At the end of the first spray, the concentration in the d rywell sump was 4x 10" micro-grams / liter and the volume was approximately 332 liters. The number of grams g rams . of iodine transferred to the liquid in the drywell sump was 13.15 The difference between the number of grams of iodine removed from the gas phase and the number of grams of iodine transferred to the liquid phase was -8.1 grams. The resulting relative error based on the gas phase is
,fgramsremovedfromuas-gramstransferredtoliouid\
\ grams removed from gas (67) x 100% , /
e rror = ( 5.082 -- 3.15) x 100*' = -13 3. 4% .
(68)
Results of the other runs were similar with more lodine appearing trans-ferred to the liquid than was removed from the gas. In fact, for many i cases the error is much greater.
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